This paper evaluates how knowledge affecting the survival of new private small and medium sized enterprises (SMEs) in an emerging economy like Vietnam. The panel data extracted from the national surveys allow for comprehensive analysis during the period 2005–2011 with the semi-parametric Cox proportional hazard model. The study examines knowledge factors under controlling firm-specific and industrial factors. The findings express strong evidence that Vietnamese SMEs benefit strongly from knowledge development. The findings suggest firms to foster labor productivity, value added, and computerization. There is evidence of market selection, based on efficiency of investment. Besides, firms should improve return on sales, especially in growing market. Start-up SMEs should prepare sufficient total assets, not basing on leverage to enter the market. Start-up in industries with high growth, especially at the early stages of the life cycle will require more government support. These findings provide the evidence for policy improvement to help SMEs in the development of knowledge economy. Knowledge; SMEs; Firm survival; Cox model; Emerging economies. PPrivate SMEs not only have the most potential role for stable growth  but alsoNevertheless, the failure rate of firms in Vietnam has extraordinarily increased during 2005–2011, especially in 2011 the exiting rate of firms was more than 12%, four-fold the normal rate due to facing some difficulties . In 2011The research significance comprises: (i) The study examines a comprehensive set of knowledge as well as control variables at firm and industrial levels to evaluate the effects of the knowledge on the survival of Vietnamese SMEs; ii) and compare their changes under different contexts, among different firm sizes and locations; iii) The paper investigates the effects of market selection, Start-up factors on firm survival which findings could provide the evidence for policy improvement to help SMEs in the development of knowledge economy.The novelty of the study includes: (i) it gives bases for the future policy renovation to support Vietnamese enterprises because determinants of firm survival are important to understand the selection market ; (ii) Th(i)The knowledge improves the survival of Vietnamese private SMEs(ii)survival depend on internal and external factorsThe effects of the knowledge on Vietnamese private SMEs'(iii)survival depend on firm size and location.The effects of knowledge on Vietnamese private SMEs'The research concentrates on the following hypotheses:After the introduction, the research includes: section 2 expresses the employed methodology with model, variables, and data. section 3 presents the empirical results and analysis while the final one presents conclusion and policy implications.22.1For knowledge factors, the number of computers is investigated because ‘computers are best described as a general-purpose technology’ , pp. 793Profitability factors, Regarding tart-up factors, start-up total assets and Start-up Leverage are found as important determinants of firm survival , “Firm failure” in this study means the firm disappearance from the market, then survivors are those appeared. The “Firm failure” function presents probability that a firm disappears at time t under the condition that it was survival until t . The hazThe stochastic events of the interested variable can be described completely by hazard function (Manjón-Antolín–Arauzo-Carod. 2008). The survival time is the spell from the start-up time of a company to the disappearance time. In this study, spell is incomplete because the time period is not fully observed , that is right censoring .2.2Vietnam had conducted the reform –“Doi moi” in 1986 with the transition to a "Socialist-oriented market economy" from a centrally planned economy. The year 1986 marked the first time private sector was recognized, then strongly developed with the privatization launched from 1992. The first Law on Enterprises was issued in 2000 along with a series of reform policies and guidelines of the Party to create a clear environment to support enterprises of all economic sectors, it opened a booming and fast-growing period for Vietnamese enterprises.SMEs had played an important role in economic development, in the period of 2000–2020, contributing more than 40% of the country's GDP and 30% of the total state budget revenue on average. The SME sector has been a major contributor to job creation, poverty alleviation, improved living conditions and inclusive and sustainable development. SMEs created 5.98 million jobs in 2010 and this number increased to 8.8 million in 2018. In addition, the development of the corporate sector made an important contribution to the expansion of social insurance participants with the proportion of the labor force of age participating in social insurance increasing from 28.4% in 2017 to 32.5% in 2019 .SMEs developed rapidly in the whole period of 2000–2015 and the average growth rate in the period 2000–2015 was quite fast with 18.1%/year, while the large-scale enterprise sector only increased by an average of 7.3%/year . The sizThe annual firm survival rate for 2013–2015 was 90.6%, down from the previous 2011–2013 survival rate of 91.3%. This was equivalent to the average withdrawal rate in developing countries of 9–10% . In 2019This shows a challenging business environment for most private enterprises in Vietnam. Vietnamese enterprises, especially micro and small enterprises, have slow development scale due to main limitations in the business environment, access to capital and finance, human resources, management skills, market access, technology and innovation capacity.33.1The hazard function is given by:With the hazard function in This semi-parametric model is more advantaged than other models due to avoiding misspecification function of the baseline hazard .In this research, new SMEs are classified as firms born in 2005, and will be investigated during the period 2005–2011. The unit of time analysis is measured by years, named firm age.To address unobserved factors, for examples management quality, prestige and fame , the CPH model in In This paper applies the research model expressed in 3.2As mentioned before, the dependent variable, hazard rate, is the probability of a firm exiting at year t under the condition that it was ‘alive’ until year t . The independent variables are theoretically driven as follows see :Table 1VAll financial variables in this paper are deflated with CPI—the annual consumer price index.3.3This study employs data from the national enterprise survey in Vietnam from 2005 to 2011, which are conducted jointly by GSO  and World Bank. This survey covers all firms in all sectors of Vietnam economy. Nevertheless, this paper only investigates the new private SMEs. The concept of ‘new’ private SMEs, refers to those that were born only in 2005 (without concerning to those born in the year different from 2005).The data are employed for period 2005–2011 because this period has experienced an outstanding institutional reform for enterprises as well as knowledge development in Vietnam. The year 2005 has remarked the first time when Enterprise Law has unified regulations on the establishment and management of all types of enterprises, regardless of whether they are state-owned or privately owned, eliminating unreasonable differences between enterprises of different economic sectors, and expanding business freedom. Furthermore, this time has observed the strong reform in innovation and technology framework, operating the national scientific and technological tasks. In the period 2005–2011, Vietnam has experienced strong fluctuation in economic development. In the period 2006–2007, the average economic growth reached 8.34%, while only reached 6.14% for the period 2008–2010 due to the impact of high inflation and the world economic recession . EspeciaBesides, the study only considers Vietnamese wholly owned SMEs, the foreign partnership companies are not taken into account. The employed dataset is right censored, similar to most other empirical studies, because the survival firms cannot be observed after year 2011—the time ending in this study. The applied methodology has accounted for this right censoring. Besides, missing values are excluded then the applied dataset include 6.752 medium sized firms and 6.514 small sized firms; or 4.034 firms locates at the North and 9.232 ones at the South of Vietnam). The employed dataset is unbalanced panel with 13.266 observations, with descriptive statistics in 4The dependent variable in this survival model is the hazard rate, therefore a positive (negative) coefficient expresses that the corresponding factor increases (decreases) the instantaneous hazard of firm failure, or in other words, decreasing (increasing) the survival probability of firms. Based on the results of the Schoenfeld test and the Wald test, the proportional hazard assumption was not rejected while the null that all parameters are zero is rejected. In addition, the assumption of no unobserved heterogeneity was not rejected then the controlling for unobserved heterogeneity has helped unbiased estimates of explanatory variables .4.1Profitability, start-up factors, and Sustainability, while Model (3) evaluates how the effects are modified after controlling industrial factors.This section investigates the impact of knowledge factors on firm survival under controlling firm and industrial factors . Model . The most beneficial knowledge factor for SMEs is number of computers, proxy for IT application, with the strongest effect, coefficient is −0.2745 .In addition, these effects of knowledge factors slightly decrease after controlling profitability, start-up factors, sustainability, and industrial factors in model 2 and model 3 . In otheThis suggests that in the development of knowledge economy, the survival is one not with higher investment but rather higher efficiency of investment.Regarding the group of profitability, all factors are significant and favourable for SMEs survival, expressing the market-selection power. Markedly, return on investment significantly contributes to SMEs firm survival while capital intensive does not. 0.5083 . This suggests that making use successfully leverage requires business experience which the new firms usually lack of.In terms of industrial factors, higher HHI, presenting market concentration, threatens the private SMEs with a higher risk of failure. The higher market concentration means the higher competition pressure for exiting and the higher risk of insolvency which are more harmful for SMEs with micro, small and medium sizes see .4.2This section investigates how the effects of knowledge factors change among different cohort of firm sizes. Based on Vietnam legal regulation, the medium sized firm is one with more than ten employees, otherwise a small one. Firm size based on the number of employees has the advantage of avoiding being affected by flexible inflation like financial measures, thus it facilitates comparison with other studies.The empirical results confirm the third hypothesis “The effects of knowledge on Vietnamese private SMEs ‘survival depend on firm size". While the effects of knowledge factors on small firms’ survival generally are the same as on whole sample, the medium firms only positively depend on labour productivity see . This su4.3This section compares effects of knowledge factors on private SMEs by different location, based on the fact that different geographical locations with different conditions of business and production, including transportation, production resources, co-operators, and characteristics of customers, etc. will support firm operation at different levels.There are outstanding differences between Northern and Southern private SMEs. While the effects of knowledge factors on the Southern firms' survival generally are the same as whole sample, only labour productivity supports the Northern ones’ survival see .Table 5CApplying IT equipment like computer powerfully helps the Southern private SMEs’ survival while it is insignificant for the Northern ones see . The reaMarket concentration becomes really harmful for the Southern but not for the Northern. The reasons might be the fact that firms located in the Northern regions are often more likely to engage in longer term contract arrangements , thus ha5Regarding the academic perspective, the paper contributes to the literature review on the performance of the enterprises in general and business performance of new private SMEs in the process of knowledge economy development in particular, and on the determinants of these firms' performance. This is a useful, highly reliable reference resource for researchers and policy consultants. From a practical perspective, the study's findings pave the way for solutions to adapt and capture opportunities in the knowledge economy. The research also contributes to the science base for supporting programs and policies, enhancing the competitiveness of enterprises, and for the policy of developing innovative eco-systems.The findings are also sources of reference for researchers and training institutions, opening up a broader way of researching the performance of enterprises in the knowledge economy, and suggesting some policy solutions as follows:First, the government should support firms in investing more in IT equipment, modern technology, creation and innovation, or R&D programs because the disadvantages of SMEs in developing countries commonly are the lack of capital and investment in creation and innovation. These investments are highly risky while their capital and capacity are limited at small and medium sizes. In addition, the implication for policy makers is to help these firms to improve labour productivity and value added by modernization, computerization and the development of human resources.Second, there is evidence of market selection, based on efficiency of investment. Therefore, the government should facilitate investment, especially in knowledge, IT, human capacity. Besides, firms should improve return on sales, especially in growing market.Fourthly, start-up SMEs should base on sufficient total assets, not on leverage to enter the market. And the government should support young firms with favourable financial source at beginning of firm business, and more easily accessible loans during its development process, especially for medium-sized firms.Finally, regarding external factors, the results suggest policy makers should support firms in industries with high market concentration. This suggests policy makers should boost the economy restructure, and improve business environment to attract firms to enter high-market-concentration industries. Besides the government should have more financial supporting, such as favourable loans and rent, tax cuts, and the like, particularly when firms are small.This research has some limitations which could be further researched. Firstly, the paper was only able to investigate number of computers, labour productivity, without total factor productivity (TFP) and total investment on R&D, innovation, human resource training, literacy rate and knowledge transfer due to the limitation of the data at the firm-level. In addition, further research should investigate the impact of present economic contexts, such as COVID-19 to Vietnamese SMEs.Nguyet Nguyen Thi, Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.National Foundation for Science and Technology Development .Assoc. Prof. Nguyet Nguyen Thi was supported by The authors do not have permission to share data.The authors declare no conflict of interest.No additional information is available for this paper.


The demand for biodegradable products has increased; hence, a suitable method for producing green composites is essential. This study prepared corn starch-based films using the solution casting method, and the physicochemical properties of the prepared films were investigated using a mixture of glycerol (GLY) and erythritol (ERY) at different ratios  as plasticizing agents. The crystallinity, hydrophilicity, mechanical properties, oxygen and water vapor, surface roughness, and thermal stability of corn starch-based films were analyzed using small-angle X-ray diffraction, water contact angle, automatic tensile testing machine, oxygen permeability tester and water vapor permeability analyzer, atomic force microscope, and thermogravimetric analyzer. With the increase in GLY ratio, the thickness, water-solubility, water content, water vapor permeability, elongation at break, oxygen permeability and V-shaped crystallization of the corn starch-based films increased. The tensile strength and the thermal stability decreased with increasing the GLY ratio. We developed a new plasticizer using glycerol and erythritol to improve the properties of starch films and provided the basis for the industrial production of corn starch-based films. GLY  and ERY  were supplied by Solebo .Corn starch-based films were prepared using the solution casting method . BrieflyAfter the corn starch-based films were balanced for 48 h, the thickness of the films was measured  using an1). Next, the corn starch sample and 100 mL distilled water were added to a conical bottle, the bottle was placed at 25°C and stirred at 180 rpm for 6 h, and the sample was removed and dried in an oven at 110°C for 7 h. The samples were weighed (M2), and the solubility of the different corn starch-based films was calculated according to the following formula:The solubility of corn starch-based films was determined according to the method described by Wang et al.  with sliThe experiment was repeated three times, and the average value was calculated.3). Then, the corn starch-based film samples were placed in an oven at 110°C and dried for 24 h. After the drying was completed, the samples were removed, and each starch film sample was weighed (M4). The moisture content of the different corn starch-based films was calculated using the following formula:After corn starch-based films were balanced for 48 h, they were cut into square pieces of 2 × 2 cm, and their mass was weighed  was placed on the surface of starch-based films with the size of 5 cm × 5 cm. The surfaces should be smooth and wrinkle-free. As the drop of water spreads, it forms a dome shape across the surface. The contact interface between the droplet and the corn starch-based films was photographed when the droplet contacted the starch film for 10 s.2. Circular corn starch-based film samples were then placed into the WVP tester. The time was set to 12 h, with a determination interval of 30 min. The average WVP of the corn starch-based films samples was obtained after measuring WVP of each sample three times.Herein, we used W3, a 030 WVP tester  . After b2. The corn starch-based films should be smooth and intact without scratches.The gas permeability tester  was used to measure the oxygen permeability of corn starch-based films. The parameters were 25°C, 53% relative humidity, and the tested area was 50 cmAfter the corn starch-based films were balanced, they were cut into rectangular pieces (1 × 10 cm), then placed on a tensile testing machine , with a crosshead speed of 50 mm/min. At the end of the experiment, the tensile strength  and elongation at break  were measured using an automatic tensile testing machine. The mechanical properties of each group of samples were measured at least five times, and the average value was used.After the corn starch-based films were balanced at 25°C and 50% RH for 48 h, each sample was installed on a special measuring glass sheet, and the crystallinity was measured using an X-ray diffractometer  , 18. TheA thermogravimetric analyzer was used to determine the thermal stability of the corn starch-based films , 20 and Atomic force microscopy can evaluate the surface roughness of corn starch-based films. The atomic force microscopy tapping mode was set at a scan size of 10 μm × 10 μm. After testing, NanoScopeAnalysis1.5 analysis software was used to analyze AFM data (Rq: Root mean square average of height deviation) .Each group of experiments was repeated at least three times, and one-way analysis of variance was performed. Data were analyzed using SPSS software . The difference between the average values of the data was compared using Duncan’s range test, and P < 0.05 was considered statistically significant.We observed that the thickness of the starch films increased with the increasing plasticizer ratio. The molecular basis for this may be that the plasticizer can penetrate the structural network of the corn starch-based films, resulting in a greater film thickness . As showMoisture content is an important index of materials used to make starch films. Water molecules can play a plasticizing role in starch films because starch is a hydrophilic polymer . As showThe mechanical properties of corn starch-based films determine their use in the packaging industry, so the TS and EAB of corn starch-based films are important indicators for determining whether corn starch-based films can be used as packaging materials . PlasticThe primary function of food packaging materials is to avoid contact between food and external media and control the water exchange between food and the environment; therefore, WVP is an important parameter of packaging materials . As show2s–1Pa–1), indicating that GLY had a significant effect on the OP of corn starch-based films. The reason behind that could be attributed to the molecular weight of GLY, which is smaller than that of ERY, making it easier for GLY to enter starch granules and destroy the intermolecular bonds of starch, thus softening the internal bulk structure of corn starch-based films. As a result, corn starch-based films’ internal oxygen transport channel increases. In turn, the OP of corn starch-based films increases with the increase of GLC concentration. Siripatrawan and Vitchayakitti   . It has  < 0.05) , 35, 37. < 0.05) .The water contact angle is an important index for determining the efficiency of packaging materials . The sizThe crystallinity of corn starch-based films with different GLY to ERY ratios is shown in As shown in It can be implied from Herein, the physicochemical properties of corn starch-based films with different GLY/ERY ratios were investigated. With the increase of the GLY ratio, the barrier performance (WVP and OP) of corn starch-based films increased. In addition, the mechanical properties of corn starch-based films changed significantly with the increase of the GLY ratio (TS decreased and EAB increased). The basic physicochemical properties  of corn starch-based films decreased with the increase of GLY ratio. Further, GLY has a greater effect on the thermal stability of corn starch-based films than ERY. The experimental results can provide a theoretical basis for the production of high barrier packaging materials, such as tea packaging.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.BW: investigation, software, visualization, and writing – original draft. XX and YF: supervision and project administration. SY: formal analysis. BC and AMA: conceptualization, methodology, writing–review and editing, and supervision. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Planar spiral spring is important for the dimensional miniaturisation of motor-based elastic actuators. However, when the stiffness calculation of the spring arm is based on simple beam bending theory, the results possess substantial errors compared with the stiffness obtained from finite-element analysis (FEA). It deems that the errors arise from the spiral length term in the calculation formula. Two Gaussian process regression models are trained to amend this term in the stiffness calculation of spring arm and complete spring. For the former, 216 spring arms’ data sets, including different spiral radiuses, pitches, wrap angles and the stiffness from FEA, are employed for training. The latter engages 180 double-arm springs’ data sets, including widths instead of wrap angles. The simulation of five spring arms and five planar spiral springs with arbitrary dimensional parameters verifies that the absolute values of errors between the predicted stiffness and the stiffness from FEA are reduced to be less than 0.5% and 2.8%, respectively. A planar spiral spring for a powered ankle–foot prosthesis is designed and manufactured to verify further, of which the predicted value possesses a 3.25% error compared with the measured stiffness. Therefore, the amendment based on the prediction of trained models is available. The outstanding performance of elastic actuators facilitates the wide application in various fields. Especially in the fields of exoskeletons, walking robots and powered upper- or lower-limb prostheses, a rotating elastic actuator with a sufficiently small size is desired. The key to dimensional miniaturisation lies in the design and performance of the elastic element, that is the torsion spring. When the required stiffness and twisting angle of the spring are large, two common kinds of torsion springs, the traditionally cold-coiled torsion spring and the torsion bar, are not suitable for miniaturisation. The former needs a large diameter of the material, correspondingly, large inner and outer diameters. The latter needs a long length. The research of planar torsion spring possesses the potential to solve the problem.1. A similar spring is designed and applied in a cycling-enhanced knee exoskeleton2. In the rehabilitation instruments, two motor-based series elastic actuators of gait rehabilitation4 and a hydro-elastic actuator for upper limb rehabilitation5 are designed with the planar spiral spring with two spring arms. Other kinds of planar torsion springs are also reported in several fields, such as humanoid robots6 and powered transfemoral prostheses7.A typical design of the planar torsion spring is based on Archimedean spiral, usually called planar spiral spring, and the kind of springs has been engaged in different applications. A unidirectional series elastic actuator employs a planar spiral spring with a single spring arm3 find that, for their designed spring, the actual spring stiffness differs considerably  from what has been calculated and simulated  based on simple beam bending equations. With a similar calculation method, Chaichaowarat et al.2 report that the geometry design obtained from the calculation shows more than two times stiffness than that of the design target. In the design from Stienen et al.5, the proposed geometry design and theoretical stiffness cannot be verified correctly in the finite-element analysis (FEA).For a motor-based elastic actuator, the stiffness of the elastic element, which has an influence on the bandwidth of the control system and other performances, is an important objective during the design process. However, in the above applications of planar spiral springs, most of them fail to obtain the theoretical stiffness from the verification. For example, Lagoda et al.9. However, several of the parameters at the end of the spring arm in the derived equation, including the components of deformation forces, the components of displacement, and the differential coefficient of the arm deformation angle, are not easy to attain during the design process, which makes the calculation complicated and not suitable for the initial design. The other study discusses the influence of the number of springs, the turns of Archimedean spiral, the angle shift of inner support, and the spinning angle of assembly on the stiffness of spring10. However, the results are obtained from the FEA of limited models instead of a method of calculation or prediction. Lin et al.11 introduce an experienced correction coefficient determined by the external connection mode and circle number of the spring in the stiffness expression of the spring during the parametric modelling of the planar spiral spring. However, the problem of how to select the value of the experienced correction coefficient is not solved. Therefore, studying how to calculate the stiffness of the spring accurately and simply, which contributes to reducing the number of design iterations, is needed for the design and application of planar spiral spring.Several previous studies try a few methods to calculate the stiffness of planar spiral spring more accurately. A mathematical model based on curved beam theory is derived to describe the relationship between the stiffness and any given angular displacement of the spring, and a topological optimisation on the spring arm is achieved12 successfully estimate 13 kinds of metal–organic framework (MOF)-based adsorbents’ abilities of CO2 adsorption by GPR with a small amount of experimental data, in which the four kinds of input parameters have an apparent nonlinear relationship with the target. Based on a GPR model improved by the integrated radial basis function based kernel principal component analysis, Kong et al.13 construct a real-time, accurate tool wear predictive model between 48 kinds of signal features and the flank wear width of tool inserts. The study verifies that the improved GPR can deal with high-dimensional input vectors with complex relationships because all the signal features are extracted from time-domain, frequency-domain, and wavelet-domain, respectively. West et al.14 utilise the capacity of interpolation and extrapolation of GPR with sparse, highly clustered data to produce smoother estimates of radiation intensity in the reconstruction of nuclear radiation map when provided with uncertain, irregularly spaced observations. The fields of the applications of GPR include but are not limited to environment17, materials18, engineering20, and finance21. For the research target of this paper, the available data also express the above features, such as small samples, complex interrelationships and irregular observations. Therefore, GPR is selected as a possible solution, and the application of GPR in the field of mechanical design is explored.To fill up the above research gap, utilising the prediction capacity of the Gaussian process regression (GPR), which is an excellent machine-learning solution for the problem with small samples and nonlinearity, may be able to amend the current method. GPR has shown its advantages in various fields. Gheytanzadeh et al.After identifying which term is the source causing error mainly in the stiffness calculation, this paper contributes to the amendment of the error-source term via the prediction of GPR models, which are trained by finite-element data sets and corresponding geometrical parameters of Archimedean spiral spring arms or complete planar spiral springs. The amended method improves the accuracy of theoretical stiffness calculation when the calculated results are compared with the stiffness from FEA and the actual stiffness obtained by measuring the sample of the designed spring. The application of the amended method substantially improves the efficiency of designing a planar spiral spring and reduces the number of design iterations.The spring arm is the main part of a planar spiral spring, and its geometry is based on Archimedean spiral, whose parametric equations are shown in Eq. .1\documeentclass1pt{minimay by Eq.  with the in Eqs.  and 5)..1\docume11, the stiffness of the spiral spring arm is calculated via Eq.  a a3) and Based on the front view shown in Fig. With controlling variables of the material , the software will optimise five kinds of parameters, including basis function, kernel function, kernel scale, sigma and standardising. Thereinto, for the basis function, the software searches among zero, constant and linear. For the kernel function, the options include five major categories: rational quadratic, squared exponential, Matern 5/2, Matern 3/2 and exponential models, and each category also includes nonisotropic and isotropic models. All the mathematical expressions of the above kernel functions can be found in the introduction of Kernel (Covariance) Function Options from the website of MathWorks25.After the values of stiffness are analysed by FEA, the effective working lengths . The larger errors may come from the error accumulation. For the research of the connecting part, this paper only pays attention to the spring with two identical spring arms, whose spiral wrap angle is 1.5π rad. Therefore, several limitations are more likely in the direct application in other structures. However, the method of estimation is feasible with the data of different structures. In addition, when a planar spiral spring is designed, there are always some mounting holes on the connecting part for the assembly. The influence of mounting holes on the stiffness is also not considered in this paper because of the high uncertainty of the holes’ position distribution and sizes. Generally, the existence of mounting holes on the connecting part will increase the total stiffness to some extent because of the reduction of the deformable region.Finally, during the verification with given specific stiffness, the error between the measured stiffness of the manufactured spring and the predicted stiffness is more substantial than any other errors (3.25%). However, the error is reasonable because the stiffness from FEA is set as the truth value instead of the real stiffness of the manufactured spring. Therefore, the error mainly comes from the difference between the stiffness from FEA and the real stiffness of the manufactured spring, which is caused by several possibilities. The machining error is a possible reason because it needs at least two methods, such as lathing and laser engraving, to manufacture such a piece of planar spiral spring, which creates the accumulation of machining errors. The second reason is the stiffness of assistive fixtures during the experiments, which is not included in the prediction. Similarly, the two mounting parts on the distal ends of spring arms are not analysed in the prediction. The last possibility is that the measurement accuracy of instruments is not high enough in the torque and angle measurement when the rotated angle of spring only occupies a small part of the total measuring range.In a word, the amendment based on the trained GRP models in the stiffness calculation that is based on simple beam bending theory is available to improve the accuracy of the theoretical stiffness of the planar spiral spring and its spring arm, and the method can be applied to other kinds of springs. However, the terms employed to complete the amendment still need further theoretical verification in elastic mechanics. Finally, richer data are preferred for the training to improve the precision of the prediction in future work.This paper contributes to amending the stiffness calculation of the planar spiral spring based on Archimedean spiral by training two GPR models. The results find the term of arc length of Archimedean spiral is the source of the significant errors between the calculated stiffness and the stiffness from FEA of the spiral spring arms. Amending the original error-source term in the equation, the improved calculation can considerably reduce the error between the calculated stiffness of and the stiffness from FEA of the spiral spring arms and the complete planar spiral springs. The predicted theoretical stiffness also has an acceptable error compared with the actual stiffness obtained by measuring the piece of manufactured planar spiral spring. The application of the amended equation is able to improve the efficiency of designing a planar spiral spring and reduce the number of design iterations.Supplementary Information.


KT survival was analyzed according to KDPI quartile and preimplantation biopsy score simultaneously: Q1 donors with biopsy score ≤3 had the best survival, especially comparing against Q3 with a biopsy score >3 and Q4 donors (p = 0.014). In multivariable analysis, hyaline arteriopathy, glomerulosclerosis, and KDPI Q4 were predictors for graft survival. High KDPI and a greater histological injury in the preimplantation biopsy, especially glomerular and vascular lesions, were related to a higher rate of KT loss from ECD.The increasing comorbidity of kidney transplant (KT) donors make it necessary to develop scores to correctly assess the quality of kidney grafts. This study analyzes the usefulness of the preimplantation biopsy and the Kidney Donor Profile Index (KDPI) as indicators of KT survival from expanded criteria donors (ECD). Retrospective study of KT in our center between January 2010 to June 2019 who received a kidney from an ECD and underwent a preimplantation biopsy. 266 KT were included. Graft survival was categorized by KDPI quartiles: Q1 = 86%, Q2 = 95%, Q3 = 99% and Q4 = 100%. KT from KDPI Q1 presented better survival ( The shortage of kidneys for transplantation has led to the increased use of suboptimal donors. These changes in the demographics of kidney transplant (KT) donors make it necessary to develop tools to assess the suitability of the grafts .Usually, KT viability was determined according to the United Network for Organ Sharing (UNOS) criteria and donors were identified as standard criteria donors (SCD) or expanded criteria donors (ECD) . HoweverIn the last years, several scales have been developed to measure the prognosis of the KT trying to eliminate the dichotomy of SCD versus ECD. The Kidney Donor Profile Index (KDPI) was developed in 2014 by the American Transplantation Registry. It gives a score from 0% to 100% which summarizes the risk of graft failure and it is calculated using 10 donor factors . KDPI isPreimplantation biopsy has been used to evaluate the kidney graft, mostly in ECD . There aOur main purpose is to analyze the value of preimplantation biopsy and the KDPI in our setting as indicators of KT graft survival from ECD. As a secondary objective, we analyzed the renal graft function and its relationship to the KDPI score and the histological findings in a preimplantation biopsy.We present a retrospective cohort study of KT patients at Puerta del Mar Hospital between 01/01/2010 and 01/06/2019 who received a KT from an ECD  . We perfAll recipients received immunosuppressive induction with basiliximab or thymoglobuline . Maintenance immunosuppression included tacrolimus (trough level 5–10 ng/ml), mycophenolate mofetil , and prednisone (5 mg/day).Graft biopsies were obtained by renal wedge during the bench surgery from a representative part of the graft, avoiding scars. KT biopsies were analyzed by four expert pathologists. All of these biopsies had more than 25 glomeruli. The ECD KT with biopsies from other centers were excluded. The samples were processed fresh and tissue was frozen immediately using methyl butane which was cooled in liquid nitrogen. Subsequently, the cuts were made in the cryostat, and stained with rapid hematoxylin-eosin staining. The results are obtained in 15 min approximately.The biopsy score was calculated following the Spanish protocol for preimplantation biopsy, based on the Remuzzi score. Five parameters were evaluated: glomerular sclerosis, myointimal elastosis, hyaline arteriopathy, interstitial fibrosis, and tubular atrophy. They were scored from 0 to 3, depending on the degree of injury. A global score ≥7 or a score of 3 in any of the first 3 histological compartments is considered unfavorable for transplantation and graft should be discarded .We analyzed donor and KT recipient variables, and estimated glomerular filtration rate 3 months and 1 year after KT. The score obtained in each individual histological component and the cumulative score for pathological lesions of the preimplantation biopsy were collected. Kidney graft survival was defined as the time from transplant to graft failure, censoring for death with a functioning graft. Deceased patients with a functioning graft were considered as lost to follow-up. Glomerular filtration rate was estimated by the Modification of Diet in Renal Disease (MDRD-4) . The KDPContinuous variables are presented as mean and standard deviation or median and interquartile range as appropriate; categorical variables as frequencies and percentages. Categorical variables were compared using Fisher exact test or Chi-square test, and continuous variables using the Student’s t-test, U Mann-Whitney, or ANOVA, according to normality and number of groups. For multiple comparisons in continuous variables, Bonferroni correction was conducted. Normality was analyzed by the Kolmogorov-Smirnov test.The KDPI was analyzed as an absolute value and stratified according to quartiles. The biopsy score was stratified according to the mean value of the assessment scale (score = 3). Graft survival categorized by KDPI quartile and biopsy score were plotted using the Kaplan-Meier method and compared between groups by log-rank test. Pairwise testing over strata was performed if > 2 groups were compared in survival analysis.p-value <0.1 in the univariable analysis. Several models were performed to analyze the global biopsy score, the different histological compartments, and the KDPI as a continuous and a categorical variable according to quartiles. In the models that included KDPI, donor variables already evaluated in the score (such as age and diabetes) were excluded.To identify risk factors associated with graft failure univariable and multivariable analysis was performed using Cox regression. Pretransplant variables related to graft survival, KDPI, and biopsy score were included in the multivariable analysis as well as other covariates based on the criterion of p < 0.05 were considered. The statistical analysis was performed with SPSS v.25.Values significant In the study period, 720 KT were performed in our center, of which 83 corresponded to living KT donors. In 267 no biopsy was performed and in 104 KT the biopsy was processed in another center. Finally, 266 KT met the criteria and were included. The median follow-up was 46 months.n = 66); Q2 = 95% (n = 72); Q3 = 99% (n = 83); Q4 = 100% (n = 45). The median KDPI was 95% and the median biopsy score was 2 points. Four donors had acute kidney injury at the time of donation. However, they did not present greater histological scores compared to donors with normal renal function .Baseline characteristics of donors and recipients are presented in p = 0.017) and after the first year post-KT   .p = 0.001). Pairwise testing did not show differences between other groups  vs. score >3, n = 52 (19.5%). KT with a biopsy score >3 presented worse survival (p = 0.018) (p < 0.001).We compared graft survival according to preimplantation biopsy score: score ≤3, = 0.018) . In addip = 0.014)  had the best survival rate, especially compared against Q3 with a biopsy score >3 and Q4 donors (= 0.014) .p = 0.005 and p = 0.034), but not the histological injury in the rest of the compartments  and the presence of histological injury (scores 1 and 2). The absence of glomerulosclerosis and hyaline arteriopathy were associated with a better graft survival  (Model 1). When KDPI was analyzed as quartiles, Q4 was an independent risk factor for graft survival (p = 0.010) (Model 2). Replacing score biopsy for glomerulosclerosis and hyaline arteriopathy, the presence of these lesions was related to a worse graft survival  (Model 3). Finally, when we included KDPI quartiles and the score of glomerulosclerosis and hyaline arteriopathy, glomerulosclerosis (p = 0.016), hyaline arteriopathy (p = 0.047), and Q4 KDPI (p = 0.029) remained as independent predictors for kidney graft survival (Model 4).Models performed in the multivariable analysis are shown in This study presents one of the biggest cohorts and with the largest follow-up that analyzes the efficacy of the graft preimplantation biopsy and the KDPI simultaneously in the evaluation of the ECD. Both variables are necessary for the assessment of non-optimal grafts. Additionally, we have identified a very high-risk group of donors, who are those with a KDPI greater than 99% and a biopsy score >3 points.The usefulness of preimplantation biopsy as a predictive tool for graft survival has not been validated yet and some studies discuss its value for the assessment of the quality of organs from ECD ,18-20. IWe observed that glomerulosclerosis and hyaline arteriopathy was related to shorter graft survival. Some groups have defended the value of glomerulosclerosis as the main parameter in the evaluation of the preimplantation biopsy, showing that a percentage of glomerular sclerosis >20% is associated with a worse graft evolution -25. BröcRegarding a typical frozen sections’ biopsy analysis, subtle findings such as interstitial fibrosis and tubular atrophy, thickening of capillary walls, mesangial cellularity, and histological lesions related to diabetes and other comorbidities are often more difficult to identify compared to correctly fixed and stained sections such as microwave paraffin embedding ,24,27. IBecause of the controversy about the efficacy of histologic evaluation for predicting graft survival, the KDPI has been implemented in the United States as an effective system for evaluating the quality of deceased donors . Along wDue to the technical limitations of the preimplantation biopsy and the lack of accuracy of KDPI, it seems reasonable the combination both variables for the assessment of the ECD. We analyzed simultaneously KDPI and biopsy scores in an ECD cohort and we identified a group at high risk of graft failure: KDPI greater than 99% and biopsy score >3. However, a KT with a very high KDPI score that does not present these lesions in the biopsy can offer an acceptable medium-term survival , especially through an old-for-old allocation program or for high estimated post-transplant survival (EPTS) recipients . On the Our study presents several limitations. It is a retrospective, single-center study, with the limitations that inherently may exist in data collection. Second, biopsies were not re-evaluated retrospectively by a single pathologist in order to reduce the interobserver variability. However, only a limited group of expert pathologists analyzed the biopsies. Therefore, to avoid further biases, we excluded kidneys with biopsies analyzed in other centers where there could be differences in the preparation and interpretation of the histological samples. In third place, according to our protocol, the grafts with a very high biopsy score were not implanted, so we cannot be sure what function they might have had. Fourth, the use of the frozen-section analysis has drawbacks that have already been discussed. Last, when we analyzed the KDPI and the biopsy score as continuous in the multivariate models, we found no significant differences. However, when both variables were stratified, survival inequalities were observed. These divergences in the results may be due to the multicollinearity between both variables.In conclusion, the KDPI and a greater histological injury in the preimplantation biopsy, especially glomerular and vascular lesions, were related to a higher rate of KT graft loss coming from ECD. Both parameters were related to graft function and survival. As long as a kidney donor evaluation index more adapted to our country is not available as well as more rapid and precise histological techniques, we suggest that both the clinical and histological variables should be considered together in the pretransplant assessment of ECD with a high KDPI.


In cases after pancreas transplantation (PTx), the pancreas graft might be lost for various reasons, including a pancreatoduodenal graft-related complication or patient death with a functioning graft. Although the causes seem to have distinct characteristics, the causes of pancreas graft loss have not been characterized. This study aimed to characterize the causes of pancreas graft loss by analyzing data from a Japanese nationwide registry. This study included 391 patients who received simultaneous pancreas-kidney transplantation among 461 patients with PTx during the study period in approved institutions in Japan. We characterized each cause in terms of the timing of the cause-specific graft loss and preoperative factors associated with graft loss based on nationwide data from a Japanese nationwide registry. Among the 391 cases, 113 lost the pancreas graft due to patient death with a functioning graft , graft thrombus , or chronic rejection . Average (± standard deviation) time from PTx to graft loss due to DWFG, graft thrombus, and CR was 3.70 ± 4.36, 0.02 ± 0.01, and 2.37 ± 2.08 years, respectively. Duration of type 1 diabetes mellitus and donor body mass index were significantly associated with pancreas graft loss due to DWFG and graft thrombus, respectively. This characterization showed that the timing and preoperative factors associated with pancreas graft loss were significantly different for different causes of graft loss. These results may inform PTx follow-up protocols to ensure that appropriate care is based on the cause of graft loss. When successfully performed, PTx can restore endogenous insulin secretion, which results in normal glucose metabolism in patients with diabetes. Due to the therapeutic effects of insulin on glucose metabolism, PTx can reduce diabetes-related complications, such as retinopathy, nephropathy, neuropathy, gastroparesis, and cardiovascular diseases. Furthermore, considering that the complications can lead to impaired quality of life and the occurrence of life-threatening events, the clinical benefit of PTx is evident for patients with diabetes mellitus8. However, the outcomes of PTx remain unsatisfactory. For example, in Japan, the 5- and 10-year survival rates for post-transplant pancreas grafts are 76.2% and 67.4%, respectively10. These post-transplant survival rates are comparable to outcomes reported in other countries11, and this universal problem of unsatisfactory PTx outcomes is thought to be due to post-transplant pancreas graft loss. Several causes of pancreas graft loss have been reported, including pancreatoduodenal graft-related complications and death with a functioning graft (DWFG). The complications include a graft thrombus, duodenal graft perforation, immunological rejection, and recurrence of type 1 diabetes mellitus. DWFG can be caused by cerebrovascular disease, cardiovascular disease, infection, or malignancy. Thus, pancreas graft loss has a variety of causes10. Each cause is likely to exhibit different clinical characteristics, including the frequency of the cause, the timing of the occurrence, and influencing factors. To the best of our knowledge, this is the first study to describe pancreas graft loss by etiology and clinical characteristics. We hope that investigations of the clinical characteristics influencing pancreas allograft failure may enhance our understanding of pancreas graft loss and improve management and outcomes. Thus, the present study aimed to characterize the specific causes of pancreas graft loss after PTx, including predictive preoperative factors for cause-specific pancreas graft loss based on data from a Japanese nationwide registry.Pancreas transplantation (PTx), which was first performed to treat type 1 diabetes mellitus in 1966, is an established therapeutic procedure for patients with diabetes mellitusThis study included 461 recipients of PTx from a deceased donor after brain death (DBD) or a deceased donor after circulatory death (DCD). The 461 procedures were performed between 2000 and 2021 to treat type 1 diabetes mellitus at 19 institutions approved by the Japanese Pancreas and Islet Transplant Association. For the present study, we extracted anonymized clinical data for the 461 cases from the Japan Pancreas Transplant Registry of the Japanese Pancreas and Islet Transplant Association. Among the 461 PTx cases, including 458 from DBD and 3 from DCD, 391 underwent simultaneous pancreas-kidney transplantation (SPK), 51 received a pancreas after kidney transplantation (PAK), and 19 underwent PTx alone (PTA). To simplify the study model, the 391 cases with SPK, the predominant category of PTx, were included in this study. Clinical data were analyzed to identify perioperative factors and post-transplant outcomes.13.Pancreas graft loss was defined as a return of serum C-peptide to < 0.3 ng/ml. Kidney graft loss was defined as a return to dialysis. In defining graft loss, DWFG was considered a graft failure. Expanded donor criteria were defined based on criteria reported by Kapur et al. and Troppmann et al.Given the anonymization of the data, the study was exempt from approval by the Institutional Review Board of Osaka University Hospital based on the ethical guideline in Japan, "Ethical Guidelines for Medical and Biological Research Involving Human Subjects." Informed consent was waived for the same reason. This study was conducted in accordance with the Declaration of Helsinki. Measured data are described as the mean ± standard deviation for continuous variables, and as the number (%) for categorical variables. Differences between groups were assessed by chi-squared, Fisher’s exact test, or Mann–Whitney U test, as appropriate. The cumulative incidence of pancreas graft loss was assessed by the Kaplan–Meier method. Hazard rates were measured in terms of the number of events per the number of patients at risk over a 1-year interval. To visualize the hazard rate pattern, we created smoothed curves with a Kernel smoothing procedure. Univariate and multivariate analyses of Cox proportional hazards regression models were performed to identify preoperative factors that may affect pancreas graft loss. Multivariate analysis was performed using significant factors and those with a tendency toward significance in the univariate analyses. Statistical analyses were performed using JMP Pro 14 software . p-values < 0.05 were considered significant, and p-values < 0.1 were considered to trend towards significance.Post-transplant pancreas graft loss was identified in 77 of the 391 SPK cases (19.7%). The cumulative incidence of pancreas graft loss 1, 3, 5, and 10 years after PTx was 12.5%, 15.2%, 17.2%, and 24.9%, respectively. The pancreas graft loss was caused by DWFG , graft thrombus , chronic rejection , duodenal graft perforation , acute rejection , recurrence of type 1 diabetes mellitus , and pancreatoduodenal graft-related complications other than graft thrombus or duodenal graft perforation . DWFG was caused by infection (n = 13), cerebro-cardiac disease (n = 10), malignancy (n = 4), multiple organ failure (n = 3), renal deficiency (n = 1), graft versus host disease (n = 1), and unknown reasons (n = 2). These causes are summarized in Table 13), there were no significant differences among the groups. In contrast, donor body mass index (BMI) was significantly higher in the graft thrombus group than the DWFG group (p = 0.0279). The number of human leukocyte antigen mismatches was comparable among the groups. With regard to recipient-related factors, sex distribution, the duration of type 1 diabetes mellitus, the proportion of patients that required dialysis, the duration of dialysis, and the time after the registration of PTx were also not significantly different among the groups, whereas recipient age tended to be older in the DWFG group than the CR group (p = 0.058) and recipient BMI tended to be higher in the graft thrombus group than the DWFG group (p = 0.0615). There were also no significant differences in PTx-related factors, such as the duration of pancreas or kidney graft ischemia, among the three groups.In the present study, we focused on the three major causes of post-PTx pancreas graft loss: DWFG, graft thrombus, and CR. First, we compared the clinical backgrounds of these three groups Table . In regaNext, we investigated the timing of graft loss due to the three major causes Table . The aveBased on the results in the three groups, we investigated potential factors that might affect pancreas graft loss in univariate and multivariate Cox proportional hazards regression analyses. Preoperative factors associated with pancreas graft loss were significantly different among the three groups. The univariate analysis showed that, in the DWFG group, pancreas graft loss was significantly associated with recipient age , the duration of type 1 diabetes mellitus in the recipient , the duration of dialysis in the recipient , and the duration after the registration for PTx , a more than average BMI was significantly associated with graft thrombus-related pancreas graft loss compared to less than average BMI . Thus, the significant preoperative factors independently associated with pancreas graft loss were different between the DWFG group and the graft thrombus group, and no preoperative factors were significantly associated with pancreas graft loss in the CR group.Finally, to identify independent preoperative factors significantly associated with pancreas graft loss, a multivariate analysis was performed using the significant factors and those with a tendency toward significance in the subgroups based on the causes of pancreas graft loss Table . The anaIn the present study, we characterized three major specific causes of pancreas graft loss after SPK based on the nationwide PTx registry in Japan. The three causes were selected based on the frequency of occurrence in anticipation of the potential clinical applications of our results. We found that the timing of pancreas graft loss and associated preoperative factors were remarkably different for the three causes in the SPK cases.18. However, these analyses included the entire PTx cohort without focusing on the causes of graft loss, even including PAK and PTA cases with considerably varied characteristics. Considering the potentially different characteristics of the causes, some significant factors associated with prognosis may have been masked in previous studies that included an entire population. Furthermore, due to the pooling of the various causes of pancreas graft loss, the statistical analyses may have overestimated the significance of certain factors. Ito et al. demonstrated that no factors significantly influenced pancreatic graft survival in a multivariate analysis of post-PTx outcomes based on the Japanese database19. If they had performed the analysis based on cause-specific subgroups, their results would have been similar to those reported in the present study.Previous studies have discussed factors that significantly influence PTx outcomes in patients with type 1 diabetes mellitus, such as the ages of the recipient and donor, PTx category, pancreas graft preservation time, and immunosuppressive regimen25. Our results revealed that, in the presence of graft thrombus, the pancreas graft is lost very early after PTx. We also found that the donor BMI is a risk factor for graft loss due to graft thrombus. The timing of graft loss in the graft thrombus group was consistent with previous studies27. Our finding that the donor BMI is a risk factor for graft thrombus is consistent with previous findings29. Finally, no preoperative factors significantly associated with CR-derived graft loss were detected in SPK patients. However, more cases with CR-derived graft loss are required for the analysis than are included in this study. Considering that a solitary PTx (PAK or PTA) increased the risk of CR compared to an SPK, the case accumulation would not be easily completed.The present study focused on the three major causes of pancreas graft loss and provided several new findings in the SPK cases. First, in the DWFG group, the timing of graft loss was not limited to a certain period, but varied widely. Moreover, the duration of type 1 diabetes mellitus was the only factor associated with graft loss due to DWFG. To date, no studies have investigated DWFG in post-PTx cases; however, considering the nature of DWFG, and particularly the causes of DWFG, our results were considered realistic. On the other hand, the predominant timing of each cause of DWFG may be different; in other words, infection-derived DWFG may develop early after PTx, whereas DWFG due to malignancy may occur long time after PTx Fig. . In contConsidering the potential clinical applications of our results, our findings will increase our understanding of the main causes of pancreas graft loss. For example, the timing of DWFG (causing 44.2% of pancreas graft loss) does not take into regard the length of the post-transplant period. In addition, increased understanding of the risk of pancreas graft loss associated with each cause may reduce delays in diagnosis and performing the post-transplant follow-up. In turn, this information may lead to improvements in the PTx outcome. For example, in patients with long-term type 1 diabetes mellitus who exhibit a high risk of DWFG (with an increasing rate of 6% per year), the clinician should closely check, before and after PTx, for systemic diseases that can cause DWFG, such as cerebro- or cardiovascular diseases, infection, or malignancy. For patients at high risk of graft thrombus, more careful postoperative management, such as more frequent checking of the blood flow by ultrasonography and administration of anti-thrombotic therapy, may be helpful for prevention. Thus, based on our results, clinicians can perform careful follow-ups, keeping in mind the specific characteristics of each cause, particularly the timing and factors associated with pancreas graft loss, which would in turn lead to earlier examinations and treatment for each cause, especially in cases at high risk for each cause. The present study results are somewhat novel in the field of PTx.The present study has several limitations. First, the study was based on a database analysis; we searched the data for specific causes of pancreas graft loss. However, we might have missed some cases in which the pancreas graft was lost due to multiple causes. For example, in some cases, the database might have recorded pancreas graft loss due to a duodenal graft perforation, but CR may have caused the perforation. Ideally, a closer investigation of the causes is required. However, due to the retrospective study design, closer investigation was not possible. Therefore, this limitation may have affected the study results. Second, the definitions of some events, such as AR and CR, are not fixed in this database. Information regarding whether the diagnosis is based on the result of a biopsy of the pancreas graft is also not included in the database. These findings imply not only the existence of certain bias, especially among the institutions, but also room for improvement in the database. Third, this study is based on a nationwide registry in Japan, where the criteria for pancreatic graft loss is strictly determined as a return of serum C-peptide to < 0.3 ng/ml. In this context, it might be difficult to apply our results in some countries. The last limitation was the small number of SPK cases, even though the database included nationwide PTx cases. In particular, each of the three cause groups comprised low numbers of patients. If the number had been more, we could investigate factors associated with each cause of DWFG. Including more PTx cases would have enabled a closer investigation of factors that affected the outcome.In summary, our results highlight different characteristics of the specific causes of pancreas graft loss, including the timing and associated preoperative factors after PTx. To the best of our knowledge, this study is the first to address this issue. In particular, DWFG occurred in 44.2% of the post-transplant cases, with the risk increasing at a rate of 6% per year of type 1 diabetes mellitus duration, and its timing has no regard for the length of the post-transplant period. These findings have increased our understanding of the specific causes of pancreas graft loss. Moreover, our results demonstrate the clinical utility of analyzing the specific causes of pancreas graft loss in patients undergoing PTx for type 1 diabetes mellitus.


In both trials, each parameter was measured at before (Pre) and 5 min (Post 1) and 30 min (Post 2) after trial. After the experiment, CT did not cause significant changes in any arterial stiffness parameters, whereas ET significantly reduced CAVI (from Pre to Post 1: −0.8 ± 0.5 unit p < 0.01), CAVI0 (from Pre to Post 1: −1.2 ± 0.8 unit p < 0.01), haPWV (from Pre to Post 1: −47 ± 35 cm/s p < 0.01), and baPWV (from Pre to Post 1: −120 ± 63 cm/s p < 0.01), but not hbPWV or cfPWV. Arm diastolic blood pressure (BP) at Post 2 was slightly but significantly increased in the CT compared to Pre or Post 1, but not in the ET. Conversely, ankle diastolic and mean BPs at Post 1 were significantly reduced compared to Pre and Post 2 in the ET (p < 0.01). These findings suggest that low-intensity EMS of the lower limbs reduces arterial stiffness, but only in sites that received EMS.Electrical muscle stimulation (EMS) has traditionally been employed to improve muscle strength and glucose uptake. EMS may also reduce arterial stiffness, but little is known about whether low-intensity EMS reduces systemic and/or regional arterial stiffness. This study aimed to examine the effects of low-intensity EMS of the lower limbs on segmental arterial stiffness. Fourteen healthy subjects participated in experiments under two different protocols  and electrical stimulation trial (ET)) in random order on separate days. The EMS was applied to the lower limbs at 4 Hz for 20 min at an intensity corresponding to an elevation of approximately 15 beats/min in pulse rate (10.7 ± 4.7% of heart rate reserve). Arterial stiffness was assessed by cardio-ankle vascular index (CAVI), CAVI Arterial stiffness has been identified as an independent risk factor for future cardiovascular disease . Pulse wExercises, particularly aerobic exercise, are widely known to be important for reducing arterial stiffness. Indeed, cross-sectional studies have shown that arterial stiffness is lower in runners, cyclists, and swimmers than in control subjects . Acute aIn the case of passively simulating aerobic exercise, EMS is widely applied to the lower skeletal muscle at relatively low intensity, because the lower limb contains many large muscles and low-intensity stimuli can reduce pain, discomfort, and risks of injury to the joints or muscles. However, one-legged exercises at low-intensity reduce arterial stiffness in the exercised leg, but not in the non-exercised leg or central part, and alterations in arterial stiffness may be predominately mediated by local factors rather than systemic factors . AlthougBased on this background, we hypothesized that low-intensity EMS of the lower limbs would induce reductions in arterial stiffness parameters involving the lower limbs, but not in body parts that did not receive EMS. The present study thus aimed to examine the effects of low-intensity EMS on segmental arterial stiffness.2, respectively. All participants were non-smokers and were not taking any medications or supplements at the time of enrolment. Patients were not obese (BMI <30 kg/m2) and did not have hypertension (systolic BP < 140 mmHg and diastolic BP < 90 mmHg). None had any history of chronic diseases that could affect cardiovascular health, metabolism, or exercise. Participants had not participated in any regular exercise programs, such as club, team, or extracurricular activities of sports, for at least the previous 2 years. The purpose, procedures, and risks of the study were explained to all participants and written informed consent was obtained prior to enrolment in the study. All study protocols were reviewed and approved by the Human Ethics Committee at Osaka Institute of Technology  and were conducted in accordance with the guidelines of the Declaration of Helsinki.Fourteen male Japanese college students  at the Osaka Institute of Technology participated in this study. Only males were recruited for this study because the student cohort at the institution is predominantly male and there were no female responders to local advertisements or referrals. Mean age, height, body mass, and body mass index (BMI) were 20 ± 2 years, 170.7 ± 3.5 cm, 64.6 ± 9.5 kg, and 22.2 ± 3.5 kg/mWe determined the appropriate and minimum sample sizes before the study by calculations using G*Power version 3.1. We assumed that CAVI would change by 5–10% based on our previous other findings . A samplAll experiments were conducted in a quiet, air-conditioned room at 24–25°C. To avoid potential diurnal variations, two experiments for each participant were performed at the same time of day at least 4 h after a light meal. The range of start times for each trial was 10:00–17:00. All subjects abstained from vigorous exercise for at least 24 h before testing, and from caffeine and food for 4 h before testing. In addition, participants were advised to eat their usual habitual breakfast, lunch, or dinner the day before each experiment, and similar standard contents and mealtimes without irregularity within and between participants were confirmed from checklist questionnaires and face-to-face interview when subjects attended our laboratory. In both trials, all subjects arrived at the laboratory and rested for at least 30 min, then PWVs, hemodynamic parameters, and blood lactate concentrations were assessed in the supine position to establish pre-trial baselines (Rest phase). In the ET, after sitting for 10 min, participants underwent 20 min of EMS of lower limbs using an electrical stimulator  in the sitting position on a bed, as previously described . Three r2], carbon dioxide output [2], and expired ventilation [2 at 30 min/ 2 at baseline. Day-to-day coefficient of variation (CV) for 2 during the same exercise was 5.3 ± 1.5%, as determined in eight individuals on two separate days . During each trial , oxygen uptake [ate days . Before BP and PWVs were measured with the patient supine using a VS-1500AE/AN semi-automated device  as assessment parameters for each trial before and 5 and 30 min after each trial . Cuffs ta and b are constants. ρ is the blood density. PP is SBP-DBP. SBP and DBP are arm systolic and diastolic BPs, respectively.The values of 0 is similar index to CAVI and is theoretically more independent of BP. The CAVI and arm systolic and diastolic BPs were then used to calculate CAVI0 , as an index of central arterial stiffness, was measured using the same device in another measurement mode. Carotid and femoral arterial pressure waveforms were recorded by amorphous pulse wave sensors  attached to the carotid and femoral arteries, and values were automatically calculated as the distance between the carotid and femoral artery sites divided by transit time. The CVs for CAVI, haPWV, baPWV, hbPWV, and cfPWV measurements on two separate days (reproducibility) were 3.6 ± 0.6%, 2.6 ± 0.6%, 2.7 ± 0.3%, 4.2 ± 0.6%, and 7.5 ± 1.2%, respectively . Recent te CAVI0  (Eq. 2).a and b in the CAVI equation are different for different ranges of CAVI. Pref = 100 mmHg as a reference pressure. Ps and Pd is right arm systolic and diastolic BP, respectively.The values of t-test. All data were statistically analyzed using Sigma Stat version 2.03 . To quantify the magnitude of the experimental effect between Pre and Post 1, ES (dz) was calculated using G*Power version 3.1. A criterion alpha level of p < 0.05 was used to determine statistical significance for all data.All values are presented as mean and standard deviation (SD). Changes in each parameter were analyzed by two-way  repeated-measures ANOVA. When the F-value was significant, Bonferroni correction was applied for post-hoc multiple comparisons. Changes in arterial stiffness between Pre and Post 1 trial were performed using the paired p < 0.01; Two-way repeated-measures ANOVA revealed significant interactions in PR, lactate, and respiratory gas parameters, respectively , but not in hbPWV or cfPWV , haPWV , and baPWV  were all significantly reduced at both Post 1 and Post 2 (p < 0.01). CAVI, CAVI0, haPWV, and baPWV values at Post 1 were also significantly lower in the ET than in the CT. Furthermore, value of reductions in CAVI, CAVI0, haPWV, and baPWV were significantly greater in the ET than in the CT . Ankle diastolic BP at Post 2 was also significantly lower in the ET than in the CT (p < 0.05). Ankle diastolic and mean BP were significantly reduced between Pre and Post 1 in the ET (p < 0.01). Ankle diastolic BP at Post 2 was significantly increased compared with Pre or Post one in both trials .Two-way repeated-measures ANOVA revealed no significant interactions in arm BPs. Arm BPs at Pre did not differ significantly between both trials. Arm systolic BP and mean arm BP did not change significantly in either trial throughout the experimental period. However, arm diastolic BP at Post 2 was slightly but significantly increased compared with Pre or Post 1 in the CT, but not in the ET p < 0.05 . Convers0, haPWV, and baPWV, but not cfPWV or hbPWV. These findings suggest that acute EMS reduces arterial stiffness and that this reduction in arterial stiffness is not uniformly observed among the segments.The salient findings from this investigation were that low-intensity EMS of the lower limbs significantly reduced CAVI, CAVIIn the present study, the intensity of EMS was set a 15 ± 7 beats/min increase in PR compared to the baseline value, and mean levels during EMS were 77 ± 6 beats/min (10.7 ± 4.7% HRR), which indicates light-intensity exercise stimulus . Respira0, haPWV, and baPWV were significantly reduced by EMS, whereas hbPWV and cfPWV were not. BP itself is well known to affect PWV values . The decrease in arterial stiffness with low-intensity EMS is therefore considered to be influenced by the increase in NO production due to increased blood flow. From the above, a potential mechanism explaining the acute reduction in segmental arterial stiffness may be related to increased segmental blood flow due to passive muscle contraction by EMS.Increased blood flow is considered to be one of the key factors contributing to acute exercise-induced reductions in arterial stiffness. Vascular smooth muscle tone is affected by vasoactive substances such as nitric oxide (NO) synthesized by vascular endothelial cells. Previous tiffness . In additiffness . The protiffness . The mustiffness . In the We can only speculate on the physiological mechanisms by which EMS reduces arterial stiffness only in sites that received EMS. A study has reported that acute exercise can induce a greater reduction in peripheral parts than in central parts , and cfP0 as an index of arterial stiffness, although intensity of EMS in the present study was 10.7 ± 4.7% of HRR. Moreover, METs during EMS corresponded to approximately 2 METs (1.8 ± 0.3), comparable to that during standing. The intensity of EMS was thus very low, but low-intensity EMS may generally induce similar reductions in arterial stiffness compared with acute low-intensity regular aerobic exercise. Interestingly, arterial stiffness was reduced despite the low-intensity EMS. This reduction in arterial stiffness due to EMS appears to be affected by increased local blood flow due to passive muscle contraction, and this response was only in sites that received EMS. However, such EMS would still be beneficial for individuals with lower limb disease. In addition, adding other exercise methods  may be an effective method. We therefore believe that these data represent useful information for the development of effective intervention programs using EMS.Regular aerobic exercise  is important to reduce arterial stiffness. A recent study reported that acute low-intensity aerobic exercise (30–50% HRR) reduced arterial stiffness (an approximately −15% reduction in CAVI) in young people . The preIncreased arterial stiffness is widely accepted as an independent risk factor for future cardiovascular diseases or mortality . Recent Finally, several important limitations need to be considered for this study. We calculated appropriate sample sizes before the study, but the cohort of participants was homogeneous, comprising healthy young individuals. In general, large elastic arteries progressively stiffen with age . TherefoResults from the present study demonstrated that low-intensity EMS of the lower limbs reduced arterial stiffness. Moreover, arterial stiffness was only reduced in sites at which EMS was performed.


Synergized multi-plasticizers for a starch-based edible film were developed for food packaging. The most popular edible plasticizers, water, glycerol, and sorbitol were used as modal materials to demonstrate the synergized function of multi-plasticizers. The efficiency, stability, and compatibility of each plasticizer, as well as their synergized functions were investigated based on the characterizations of tensile properties after storing under different humidity conditions and for different times. The relationship between the microstructures of the plasticizers and their performances was studied and established. The results showed that water is an efficient plasticizer but is not stable, which results in it becoming brittle under lower humidity conditions; glycerol has a stronger moisture-retaining and absorption capability, which results in a weaker tensile strength under higher humidity conditions; and sorbitol is an efficient and stable plasticizer but needs to work with water, and its function can be synthesized by mixing it with water and glycerol. Many natural polymers, such as protein, starch, and chitosan have not only attracted considerable attention as eco-friendly materials to replace conventional petrol-based plastic for packaging but have also become ubiquitous as edible packaging films or coatings to protect foods and extend their shelf-life ,2,3,4,5.The International Union of Pure and Applied Chemistry (IUPAC) gave the definition of plasticizers in 1951: it is a substance incorporated in a material matrix to increase its flexibility, workability, or distensibility. The basic requirement for a plasticizer is to be miscible or compatible with the plasticized polymer. Incompatible substances will exudate from the matrix and will result in poor physical properties ,21,22. TThe efficiency of a plasticizer containing hydroxyl groups strongly depends on the environment, especially on the humidity conditions. This work aimed to study and develop starch-based edible films used for application in food packaging. The films used for food packing need to meet different humidity conditions. For example, seasonings bags in fast noodles are kept with the noodles constantly under very dry conditions (RH < 5%) while some fruits or candy could be packed in higher humidity conditions. In this work, the most popular edible plasticizers, water, glycerol, and sorbitol, were used as modal materials and various mixtures were studied to explore their plasticizing efficiency and mechanism since glycerol is a liquid while sorbitol is a solid. The efficiency, stability, and compatibility of each plasticizer, as well as their synergized functions were investigated based on the characterizations of the tensile properties after storage under different humidity conditions and for different times. The relationship between the microstructures of the plasticizers and the performances was established. The signalization of different plasticizers were investigated and used as guidelines for developing starch-based edible films.All the materials used in this work are commercially available in the market. Hydroxypropyl cornstarch (HPCS)  was supplied by Hengrui Starch Company, Luohe, China since it has good mechanical and processing characteristics ,9,10. Tiw/w) prepared in a conical flask, in which 10 g starch (dried based) was mixed with 90g water. On a dry basis, the various plasticizers were applied at ratios in proportion to the starch weight (10%). The sample codes and formulations are listed in The casting starch films were fabricated from starch suspensions with 10% concentration  for 48 h  before testing. The data presented are the average results from seven specimens.The tensile behaviors of the starch films were measured based on the tensile standards of ASTM D882-12 using a tensile facility (Instron 5565). The crosshead of 5 mm/minThe surface structure and fracture surface of the films were studied by a SEM . The fracture surfaces were prepared from tensile testing. The surface and fracture surface of the samples were fixed on metal stubs with double-sided glue then coated under vacuum using an Eiko Sputter Coater. In order to avoid the risk of damaging the surface, a low voltage of 3 kV was used in this work.The film transparency (%) was measured using a UV spectrophotometer . The transparency value was presented based on the average of three measurements at a wavelength of 350nm.The CA of water on the starch films was measured using a Contact Angle System OCA20  at 25 °C. A total of 4 µL water was dropped on the starch film then the value of CA was immediately recorded. Three different places were evaluated for each sample and the reported data were the averages of the three readings.p < 0.05 was classified as having significant differences based on Duncan’s multiple range testing.All the results are presented by date based on statistical analysis as means ± SD (standard deviation). All the experimental results were statistically analyzed by the software ANOVA . The sample with result The effects of individual and mixed plasticizers on tensile properties, contact angle, and transparency of starch-based film under a certain RH (40%) are presented in Both glycerol and sorbitol decreased the contact angle, indicating they a stronger water absorption capability, which was expected. The transparency of starch film was not affected by the additional of both glycerol and sorbitol.Traditional plasticizers for plastics are normally liquids, while the plasticizers for starch-based materials can be either liquids or solids. However, they must be water soluble since these plasticizers have to be used together with water. Natural starches normally contain about 13% moisture ,29. ThisIt has been widely reported and well recognized that the performances of starch films strongly depend on plasticizer content and humidity conditions ,28; thusThe accepted plasticizers used for starch films, water, glycerol, and sorbitol, were used as modal materials to study the plasticizing efficiency and performance under different environmental conditions, as well as to demonstrate the synergized function of multi-plasticizers. Water acts as both a plasticizer and gelatinization additive for starch. Water is a very efficient plasticizer but is not stable, especially under very dry conditions, which results in the brittleness of starch materials under lower humidity conditions. Other plasticizers, including both liquid glycerol and solid sorbitol must work together with water as plasticizers for starch films. Without water, both glycerol and sorbitol cannot gelatinize starch given their larger molecular size. Both glycerol and sorbitol could act as plasticizers after penetrating starch chains with water. It was found that glycerol has a stronger moisture-retaining and absorption capability, which results in a weaker tensile strength under higher humidity conditions; while sorbitol is an efficient and stable plasticizer but needs to work with water, and its function can be synthesized by being mixed with water and glycerol. The fracture surface of the starch only plasticized by water had a smooth surface with typical brittle broken marks, while the fracture surfaces of starch plasticized by water with both glycerol and sorbitol, as well as their mixtures, showed some deformation of the starch matrix, indicating the toughness behavior of the materials. It was noticed that the multi-plasticizers showed a better plasticizing balance of the mechanical properties under both higher and lower RH. The sample containing both water, glycerol, and sorbitol showed some elongation under dry conditions and kept certain modulus and tensile strength under higher RH conditions. The results provide useful guidelines and directions for developing plasticizers for starch-based materials.


Cable-driven manipulators, characterized by slender arms, dexterous motion, and controllable stiffness, have great prospects for application to capture on-orbit satellites. However, it is difficult to achieve effective motion planning and stiffness control of cable-driven manipulators because of the coupled relationships between cable lengths, joint angles, and reaction forces. Therefore, a convolutional dynamic-jerk-planning algorithm is devised for impedance control of variable-stiffness cable-driven manipulators. First, a variable-stiffness cable-driven manipulator with universal modules and rotary quick-change modules is designed to overcome difficulties related to disassembly, installation, and maintenance. Second, a convolutional dynamic-jerk-planning algorithm is devised to overcome the discontinuity and shock problems of the manipulator’s velocity during intermittent control processes. The algorithm can also make acceleration smooth by setting jerk dynamically, reducing acceleration shock and ensuring the stable movement of the cable-driven manipulator. Third, the stiffness of the cable-driven manipulator is further optimized by compensating for the position and velocity of drive cables by employing position-based impedance control. Finally, the prototype of the variable-stiffness cable-driven manipulator is developed and tested. The convolutional dynamic-jerk-planning algorithm is used to plan the desired velocity curves for velocity control experiments of the cable-driven manipulator. The results verify that the algorithm can improve the acceleration smoothness, thereby making movement smooth and reducing vibrations. Furthermore, stiffness control experiments verify that the cable-driven manipulator has ideal variable stiffness capabilities. With the rapid development of space technology, various satellites have played important roles in the navigation, meteorology, and other fields. However, the failure of high-value satellites will bring huge losses. Since the above satellites are often non-cooperative, the corresponding on-orbit capture technology has attracted great attention ,2,3,4,5.In order to study the motion planning and stiffness control of the cable-driven manipulator, a variable-stiffness cable-driven manipulator with rotary quick-change module is designed and experimented on in this paper. The rest of the paper is organized as follows. Separate Layout of Mechanical and Electrical Components. The motors, controllers, and other electrical components of a manipulator are uniformly installed on a highly protected satellite platform, which enhances their reliability in harsh environments. This design also means that a manipulator is light weight and has low inertia, such that its motion has little effect on its satellite platform.Organic Integration of Rigid and Flexible Components. A manipulator achieves a rigid and flexible variable-stiffness working effect by controlling its configuration and cable tension. Thus, a manipulator is suited for use in the low-impact capture and high-stiffness manipulation of non-cooperative satellites.Dexterous Motion. A manipulator has both hyper-redundant DOF and slender linkages. Thus, it can move dexterously in unconstrained and narrow environments with many obstacles and perform maintenance tasks in complex environments.Variable-stiffness cable-driven manipulators have great promise for use in capturing non-cooperative satellites, as depicted in The variable-stiffness cable-driven manipulator studied herein has a modular design, with a universal module consisting of a universal joint and a fixed linkage, as shown in To achieve rapid disassembly, installation, and maintenance with a stable and simple mechanical structure, this paper designs an innovative variable-stiffness cable-driven manipulator with a drive system based on a rotary quick-change module. This drive system comprises six rotary quick-change modules and one central shaft. The central shaft constrains the six rotary quick-change modules between the two fixed plates, as shown in In order to achieve dexterous movement in narrow environments with many obstacles, the kinematic models of the variable-stiffness cable-driven manipulator among joint space, actuator space, and task space are derived in this section.The kinematic model is established to describe the relative kinematic relationship between joint space and task space. First, according to the structure of the variable-stiffness cable-driven manipulator, the Denavit–Hartenberg (D-H) coordinate system is established in It can be known that the homogeneous transformation matrix between two adjacent coordinate system is as (1).Then, the forward kinematics between joint space and task space of the variable-stiffness cable-driven manipulator can be written as (2).The principle of the convolutional dynamic-jerk-planning algorithm used to control the cable-driven manipulators studied herein is detailed in In Equations (1)–(4), As a demonstration, the above convolution method and an iterative Jacobian method are each used to plan the velocity curve for the movement of the manipulator, with the results shown in According to the actual operation of the variable−stiffness cable−driven manipulator and the above convolution operation process, the recursive expression of the convolution is determined by Equation (10), as follows: It can be seen from Equation (10) that the recursive calculation of the convolution is only composed of addition, subtraction, and division operations. It greatly simplifies the calculation process.The convolutional dynamic-jerk-planning algorithm is simpler to compute than the polynomial-based velocity planning method . The movAccording to the principle described in With this asymmetric velocity curve, the acceleration and jerk of the acceleration and deceleration stages can be set separately, allowing the velocity curve to adapt more flexibly to different displacements. Four displacement situations are defined: ultra-long displacement, long displacement, medium displacement, and short displacement. These different situations are described below.1.Ultra-long displacement:When the desired displacement According to the values calculated in Equations (15) and (16), the interval time By superimposing To simplify the calculation process and facilitate practical applications, the recursive expression of 2.Long displacement:When Therefore, the recursive expression for the long displacement can be derived using Equations (17)–(19).3.Medium displacement:When Thus, Then, using Equations (17)–(19), the recursive expression for the medium displacement can be derived.4.Short displacement:When Therefore, The recursive expression for the short displacement can then be derived from Equations (17)–(19).These examples demonstrate how the convolutional dynamic-jerk-planning algorithm can adapt to the cases of ultra-long, long, medium, and short displacements, and also adapt to cases with asymmetric acceleration and deceleration stages. It achieves this adaptability by freely adjusting the magnitude of the acceleration and jerk to suit different displacements of motion.The position-based impedance control is based on the second order spring–mass–damper system and adjusts the tension of the drive cables to control their stiffness. The contact force between the variable-stiffness cable-driven manipulator and the environment can be controlled by adjusting the position, velocity, acceleration, and tension of these drive cables. The impedance relationship model expression is established in Equation (28), as follows: The position-based impedance control system is composed of an inner position loop and an outer tension loop. This system controls the position and velocity of the drive cables by adjusting their tension. This system is combined with the actual cases and established in In the outer tension loop, the relationship between the position compensation of the drive cable and the tension of the drive cable can be expressed as Equation (31) indicates that the differential equation of the position-based impedance control is defined by Equation (33), as follows: The actual and compensated angles of the motor are The mapping relationship between If the error between the desired and actual tension of the drive cable is zero, then the control system can be simplified to the position control of the drive cable. If the error between the desired tension and the actual tension of the drive cable is not zero, then the control system can generate compensation based on the error between the desired tension and the actual tension of the drive cable to correct the desired position.In this paper, the inner velocity loop is added, as expressed in Equation (37), to provide position-based impedance control. Here, The prototype of the variable-stiffness cable-driven manipulator consists of hardware control and software monitoring components, which were integrated into the design of the manipulator system shown in Variable stiffness control is particularly important for the flexible capture of satellites. The stiffness of the cable-driven manipulator depends on the configuration of the moving manipulator and the tension in the drive cables. To assess these functionalities of the prototype, a series of velocity control and stiffness control experiments were performed. The entire experiment process was recorded by the global camera, which was fixed to the end of the prototype.The actual velocities of the 12 drive cables should be based on the velocity planned by the convolutional dynamic-jerk-planning algorithm. The velocity mapping between the motor and the drive cable is defined by Equation (35). The actual velocity and acceleration of the 12 drive cables are shown in The velocity errors of the 12 drive cables were calculated according to the desired velocity in The stiffness of the cable-driven manipulator refers to the ability of the end of the manipulator to resist deformation when it is affected by external forces. Generally, the greater the stiffness of the manipulator, the higher the positioning accuracy of its end. To verify the stiffness control ability of the manipulator, dynamic stiffness experiments were performed. The position-based impedance control system was applied in the dynamic stiffness experiments to control cable tension. The experiments also applied the convolutional dynamic-jerk-planning algorithm to control the displacement and velocity of the cable.Before the stiffness control experiment, the load experiment of the cable-driven manipulator was conducted in this paper. The cable-driven manipulator was placed on a fixed plane. A weight of 100 g, 200 g, 300 g, and 500 g is applied to the end of the cable-driven manipulator to test its loading capacity. The experimental results are shown in First, the dynamic stiffness control of the manipulator was established by determining the required displacement and velocity of the drive cables. The manipulator was directed to bend upward, with its motion recorded by the global camera. Then, the manipulator was moved back to its original horizontal state. Next, the end of the manipulator was loaded with a 100 g weight, and the actions of bending upward and returning to the horizontal state were repeated. Finally, the previous actions with the loaded weight were repeated with position-based impedance control applied. The end points of the manipulator’s different trajectories are plotted in The results showed that the cable-driven manipulator moved smoothly with high precision when not under load in trajectory 1. The manipulator also moved normally when loaded with a 100 g weight but exhibited a large position error compared with trajectory 1. When the final stationary state is reached, the end position error is 16.81 mm and the stiffness value is 59.49 N/m. However, this poor dynamic stiffness performance was significantly improved by applying the position-based impedance control. The position error between trajectory 1 and trajectory 3 is 1.96 mm. The stiffness value is 510.20 N/m. The stiffness of the cable-driven manipulator has been significantly improved. Therefore, the position-based impedance control improved the load capacity and control accuracy of the manipulator.A convolutional dynamic-jerk-planning algorithm was devised for impedance control of a variable-stiffness cable-driven manipulator. The manipulator was designed with six rotary quick-change modules and four universal modules to overcome the difficulties of disassembly, installation, and maintenance. The convolutional dynamic-jerk-planning algorithm solved the discontinuity and shock problems of the manipulator’s velocity during the intermittent control process. The algorithm also reduced acceleration shock and made movement more stable by setting jerk dynamically.Velocity control experiments revealed that this algorithm limited the velocity error during acceleration and deceleration to ±0.03 mm/s and the velocity error at constant velocity to ± 0.01 mm/s. By applying position-based impedance control to compensate for the displacement and velocity of the drive cables, the stiffness of the cable-driven manipulator was further optimized. Stiffness control experiments indicated that applying this control reduced the position error of a loaded manipulator from 16.81 mm to 1.96 mm.Future studies should investigate the payload capability, stiffness modeling, and force-compliant control of variable-stiffness cable-driven manipulators.