Based on the experimental analysis, the results show that the effect of hybrid fiber on the crack width and propagation is greater than that on the crack width and propagation of WOC and PC after exposure to high temperatures. However, the enhanced effect of hybrid fiber on the mechanical properties, rack width, and propagation decreases after subjecting it to a high-temperature treatment, owing to the melting and ignition of hybrid fibers at high temperatures. Regarding the computational analysis, it was found that the developed MLR model shows higher efficiency than ANN in predicting the compressive and tensile strength of PC, WOC, and WOC-Hybrid concrete.Waste ceramic concrete (WOC) made from waste ceramic floor tiles has several economic and environmental benefits. Fire is one of the most common disasters in buildings, and WOC is a brittle construction material; therefore, the mechanical properties of WOC structures under high temperatures should be considered. According to previous studies, hybrid fiber can further reduce damage to concrete under high temperatures. Meanwhile, crack width and propagation are among the key characteristics of concrete materials that need to be considered, but few studies have focused on their behavior when subjected to elevated temperatures. The new concrete materials proposed by the authors are WOC and WOC-Hybrid. WOC was prepared with Natural Coarse Aggregates (NCA), Natural Fine Aggregate (NFA), Ordinary Portland Cement (OPC 43 grade), and ceramic waste tiles with 20% replacements for coarse aggregates, 10% replacements for fine aggregates, and 10% replacement for cement. In contrast, WOC-Hybrid was prepared with the addition of hybrid fiber  in WOC. The specimens were exposed to temperatures of 100–300 °C, and then the specimens were tested for tensile and compressive strength. The present study aims to find a new method to improve concrete resistance to elevated temperatures at the lowest costs by experimental and computational analysis via machine learning models. The application of machine learning models such as artificial neural networks (ANN) and multiple linear regression (MLR) was employed in this study to predict the compressive and tensile strength of concrete. The linear coefficient correlation (R Buildings constitute the majority of built infrastructure and play a pivotal role in the socio-economic development of a country. Most buildings are designed to last for several decades and provide residential and functional operations to a large number of inhabitants throughout their design life. During this long-time span, buildings are subjected to several natural and manmade hazards which can cause a partial or complete collapse of the building and incapacitation of building operations. Such destruction or incapacitation in the event of a hazard can jeopardize the lives and safety of inhabitants and can cause significant direct and indirect monetary losses. Hence, buildings are designed to withstand actions from numerous anticipated hazards to ensure life and structural safety during their design life, and fire represents one such extreme hazard that can occur in buildings.Therefore, the resistance of concrete structures to rising temperatures is a major global concern today. It requires a strong and unified effort to arrive at a heat-resistant economic concrete using readily available resources. A promising source of low-cost materials is the growing amount of waste generated as a result of excessive urbanization, global economic development, and rapid industrialization. Casares, M.L. et al.  noted thExtreme heat causes dramatic physical and chemical changes in concrete, resulting in its deterioration . Althoug3) degrades to form quicklime (CaO), which is extremely hydrophilic. When lime comes into contact with water or air humidity, it will absorb a large amount of water. Subsequently, its volume will be increased. This increase in volume results in cracks in the rocks, thus causing the concrete to collapse [When conventional concrete is exposed to heat, exceptionally elevated temperatures cause it to lose significant strength or even wholly degrade. The presence of limestone rocks and ordinary cement in concrete is the main reason for the cracks and the release of certain gases when exposed to elevated temperatures. However, limestone is the major reason that contributes to this process. Ordinary rocks are primarily composed of lime. Normal lime  PVA + crimped steel fiber is used to improve the performances of concrete both before exposure  and after exposure (compressive and tensile strength) to elevated temperatures. (2) The inclusion of ceramic waste material is mainly for environmental protection and ceramic tiles have lower thermal conductivity and better fire resistance after exposure to high temperatures. (3) A beneficial interaction exists between hybrid fiber (PVA + CR) and ceramic, as mentioned above. Improved resistance to elevated temperatures makes WOC-Hybrid concrete useful in fire-resistant structures.The authors have conducted several tests to investigate the behavior of the proposed WOC and WOC-Hybrid. This paper presents a study on the effect of ceramic material  and hybrid fiber (PVA and CR fibers) on the mechanical behaviors of WOC and WOC-Hybrid subjected to elevated temperatures. The specimens were exposed to temperatures of 100–300 °C, and then the specimen was tested for tensile and compressive strength. The temperature 300 °C was used as the maximum elevated temperature due to the high water: cement ratio used in the mixed design (0.5W/C), which may cause damage to the furnace if we increase the temperature by more than 300 °C. To overcome this flaw, the application of machine learning models such as artificial neural networks (ANN) and multiple linear regression (MLR) was employed in this study to predict the compressive and tensile strength of plain concrete (PC), waste ceramic optimal concretes (WOC), and WOC-Hybrid fiber concrete (PVA–CR–WOC).The ANN is a widely used and efficient tool for different types of analysis. The elevated temperature  is considered as input data and compressive strength (CS), tensile strength (TS) of PC, WOC, and WOC-Hybrid concrete used as target data. The Levenberg–Marquardt training function is used to train the target data.Overall, most studies on ceramic waste materials have focused on mechanical properties at ambient temperature; however, some characteristics have not yet been clarified, including the mechanical behaviors under extreme conditions such as exposure to fire or high temperatures. Therefore, further experimental and computational studies on the fire performance of ceramic waste materials with and without fibers are necessary to promote its use. Thus, this study’s main contributions are: (a) to evaluate the potential use of  and hybrid fiber (PVA and CR) on the mechanical properties, crack width, and propagation of concrete subjected to elevated temperatures; (b) to provide a basis for further research on WOC and WOC-Hybrid concrete and its potential applications, and; (c) to compare the performances of ANN and MLR for evaluation and prediction the mechanical properties of PC, WOC, and WOC-Hybrid concrete.The present study aims to develop a low-cost method for increasing concrete resistance at elevated temperatures. Due to hybrid fibers and ceramics’ advantageous properties, the simultaneous use of these two materials in concrete mixes reduces concrete costs and environmental pollution and enhances mechanical properties when exposed to high temperatures. Furthermore, since the main reason for concrete collapses under elevated temperatures is limestone, natural materials may be partially or even entirely replaced by ceramic material to prevent such damage to concrete damage. Furthermore, to prevent concrete cracking, reduce internal stresses, and increase its thermal conductivity, hybrid fibers have been used. This study also assesses the ability of machine learning models such as artificial neural networks and multiple linear regression (MLR) to predict the strength (compressive and tensile) of three types of concrete . A MATLAB program has been created for this purpose, and representative models have been run to demonstrate efficiency and correctness. In addition to the estimate of concrete mechanical characteristics, the suggested neural system has been designed. By supplying all of the necessary information, anybody may test the proposed model.WC); 4.75 mm (waste ceramic sand—SWC), and; 75 μm (waste ceramic cement—CWC), shown below in In the experimental work, locally available materials such as ceramic waste powder, coarse ceramic aggregate, and fine ceramic aggregate have been used to replace cement (OPC 43 grade), natural sand, and natural coarse aggregate, respectively . Waste cOverall, 21 cylindrical specimens with a diameter of 150 mm and a height of 300 mm were cast in three groups for testing under high temperatures, as shown in For the present study’s purposes, 21 cylindrical specimens, each 150 mm in diameter and 300 mm in height, were cast in three groups, as shown in First Group: on the basis of test methods in accordance with IS 10262 guidelines , Plain CSecond Group: on the basis of experimental results , waste cThird Group: on the basis of experimental results , WOC-Hyb3) and W/C ratio (0.5) were the same for all the concrete mixes. However, they differed in their cement and aggregate (coarse and fine) content because waste ceramic was used as a partial replacement for either cement, or coarse or fine aggregates. The quantities of ceramics material, natural material, and fibers used are reported in WC, SWC, and CWC represent coarse ceramic aggregate, fine ceramic aggregate, and ceramic powder weight per cubic meter of concrete. The mix proportions for different types of concrete are shown in The concrete mixture for reference specimens containing natural aggregate and ordinary Portland cement (43-grade) is designed for compressive strength of 25 MPa. The water quantity . After 24 h, these specimens were demolded and cured for 28 days. The specimens were prepared for testing at a single heating–cooling cycle from ambient temperature to an elevated temperature ranging from 100 °C to 300 °C at an interval of 100 °C after the submerged curing process. The researchers used 300 °C as the maximum limit of elevated temperature due to the high water: cement ratio used in the mixed design (0.5 W/C), and damage to the furnace would occur if we increase the temperature to more than 300 °C.Automatically after heating up to the target temperature  at an average rate of 5 °C/min, (ramp rate 1–2 h), the temperatures were on hold for 1 h and then it was automatically closed down, which is shown in WC = 37 Mpa) [The compressive strength of unheated concrete samples is comparable to that of heated concrete samples and oscillates around 25 MPa . At ambient temperature (25 °C), ceramic material can increase the compressive strength by up to 39.82% for 10% ceramic powder replacement with OPC (43-grade). This finding illustrates that ceramic powder had higher strength than cement, which increased in concrete compressive strength  can improve the compressive strength of concrete, especially when fiber distribution is uniform in concrete. Using waste ceramic optimal concrete (WOC) with hybrid fibers effectively increased the compressive strength by up to 16.87% . The comFirst Group: the CS decrement for PC concrete under 100 °C, 200 °C, and 300 °C is 11.61%, 18.19%, and 36.01%, respectively. Chang, Y.F. et al.  have conSecond Group: the CS decrement for WOC concrete under 100 °C, 200 °C, and 300 °C is 8.48%, 16.72%, and 34.25%, respectively. Up to a temperature of 200 °C, the mixtures with a ceramic material (WOC) show a smaller reduction in the compressive strength compared to the reference mixture. Netinger, I. et al. [Third Group: hybrid concrete shows good performance under elevated temperature compared to reference concrete, where the reduction in CS for WOC-Hybrid concrete is 7.15%, 14.55%, and 19.51%, respectively.Hager, I.  concludeConcrete behavior in tension, whether directly or indirectly, has received scant attention. Consequently, limited research has been conducted in this area. Furthermore, most of the TS tests found in the literature are for high-performance concrete.Tensile strength decreases with increasing temperature, as illustrated in At ordinary temperature 25 °C), hybrid fiber (PVA–CR) was found capable of improving the tensile strength (TS) of concrete, especially when well distributed in concrete. Using waste ceramic optimal concrete (WOC) together with hybrid fibers (PVA + CR) was shown to be effective in increasing the TS by up to 85.44% [ °C, hybrFirst Group: the TS decrement for PC concrete under 200 °C and 300 °C is 19.21% and 35.91%, respectively. The decrease in TS could be due to the decrease in cohesive forces associated with water evaporation at this temperature. The reduction may also be due to shrinkage caused by free water evaporation and chemically bound water in cement paste, weakening the bond between aggregate–cement pastes. Chang, Y.F. et al.  have repSecond Group: the WOC specimens behave better than PC specimens with the increasing temperature, and the TS decrement for WOC concrete at 200 °C and 300 °C was 14.18% and 30.6%, respectively. For tensile strength, the mixture with ceramic material was more fire-resistant than the reference mixture over the whole temperature range. The concrete with ceramic tiles has lower thermal conductivity than concrete with natural aggregates, which might explain such mixtures’ better fire resistance in this research.Third Group: hybrid concrete shows good performance under elevated temperature compared to WOC, where the reduction in TS for WOC-Hybrid concrete under 200 °C and 300 °C is 10.26% and 17.10%, respectively. The current tests demonstrate that the addition of hybrid fibers can improve the mechanical properties of concrete at elevated temperatures, especially when tensile strength is considered. Such improvements could be attributed to the mix of two types of fibers such as metallic and non-metallic, contributing to resisting normal and elevated temperatures. Mechanical properties of concrete specimens were decreased by increasing temperature, as shown in According to Netinger, I. et al. , concretGenerally, the addition of non-metallic fibers (PP or PVA) has no significant effect on improving concrete’s CS after exposure to elevated temperature. However, such improvement is visible to a certain extent when FS and TS are considered, particularly at a temperature below 400 °C. Non-metallic fibers (PP or PVA) can increase concrete resistance to cracking, improving its behavior under the TS test . HoweverThe addition of metallic fibers (HK or CR) can improve the concrete mechanical properties at elevated temperatures when CS and TS are considered. These improvements may be a result of the fact that the testing temperatures are not high enough to melt steel fiber. Furthermore, Gao, D. et al.  concludeCrack formation, width, and propagation occur in concrete structures at high temperatures. This effect can make the structure unusable and a risk to life and property by causing death or permanent damage. Cracks in concrete specimens under high temperatures caused a decline in unit weights.Demir, A. , Tang, YAfter testing, the specimens were checked for crack width and propagation, since that was one of the purposes of this research. High-resolution digital pictures of the cylinder were taken and imported into specialized software for manual tracing of the crack pattern for each specimen. At the same time, the crack width was measured using a mobile laser crack width reader with a reading range from 0.03 mm to 2.5 mm, with an increment of 0.05 mm.Previous studies noted that the damage and cracks mainly accumulate and develop at the interface between the waste materials particles and the cement matrix ,35.The non-metallic fibers reinforced concrete has much better resistance to thermal spalling compared to the concrete without fibers because of the melting and ignition of non-metallic fibers. Consequently, the pores formed to expand to form micro-cracks, connecting the existing capillary pores to provide channels for water vapour to escape. Therefore, an optimum dosage of non-metallic fibers (PVA or PP) around 0.5–1% by the mix’s volume is recommended for concrete to obtain high-temperature crack resistance .Neurons are the structural and functional components of the nervous system that relay information between the brain and the body. A neuron has its biological structure composed of (a) the cell body, (b) the axon, and (c) the Dendron.ANN and MLR are a type of machine learning technique that depends on biological neuron networks as a foundation. This is the anatomy of biological and artificial neural networks, as depicted in ANN is built out of multiple hidden layers and an output layer. The single-layer network has a source node as an input layer and a neuron as an output layer. One or more hidden layers of neurons build out the multilayer network. When it comes to output accuracy, the number of neurons in the input plays a significant role.(a)The arrangement of connections between neurons is known as network architecture.(b)The weights of the links are determined using a learning method.(c)The activation function, which is a neuron’s intrinsic state. A single input or multiple input system is used to carry out this training procedure. It may also be divided into single and multiple hidden layers .The three essential aspects of ANN have been described by Paral, A. et al.  as folloOne of the most basic mathematical models is the multiple linear regression model (MLR). It works based on linear connections between inputs and outcomes. In other words, it involves a constant regression in the formula to extract the linear correlations between dependent and independent variables ,39. EvenThere are three distinct architectures for ANN networks: single-layer feed-forward networks, multilayer feed-forward networks, and recurrent networks. This study examined the feed-forward network with a single hidden layer. This single neuron system carries out three different functional activities. Demuth and Beale’s single and multiple input neuron systems architecture is illustrated  Figure .p is a scaler unit, multiplying with scalar weight W, and forms a product PW. Next, the weighted input PW is added with scalar bias b to develop a net input n. Finally, the net input n crosses through the transfer function f, which forms a scalar output a. The output of the single-input system is shown in Equation (1):Initially, the term f that is chosen can significantly impact the ANN’s complexity and performance. Although sigmoidal transfer functions are the most popular, other types of functions can be employed. A significant variety of potential transfer functions have been presented in previous research [The weight function, net-input function, and transfer function are the names for these three processes. The transfer or activation function research . The logThe expression of a single neuron can be written in matrix form, as in Equation (3).Therefore, the neuron output is as written in Equation (4).Si number of neurons, the weighted matrix is written as in Equation (5).For Since the training method used for optimization is essential in creating quality mapping, a thorough analysis was carried out to determine the best method for this problem. As a result, the back-propagation technique is the most often utilized approach in the literature.y: the independent variable.b: the regression constant.x: the ith predictor.MLR work is based on the equation below:This section presents the process for tuning optimum ANNs and MLR used for the training, validation, and test of the mechanical properties of plain concrete (PC), waste ceramic optimal concrete (WOC), and hybrid concrete (WOC-Hybrid) based on experimental data .The correction coefficients and the new specific terms must consider the ceramic concrete mechanical properties and replacement ratio of ceramic materials. The proposed expressions and the correction coefficients have been analyzed using formulas statistical indexes: (a) the Pearson correlation coefficient and (b) the mean squared error (MSE). Lastly, the best prediction expressions for the compressive and tensile strength of structural PC, WOC, and WOC-Hybrid are proposed.WC), ordinary Portland cement (OPC), waste ceramic cement (CWC), natural fine aggregate (NFA), waste ceramic sand (SWC), crimped fiber (CR), and polyvinyl alcohol (PVA fiber) are the appropriate input training vectors of dimension 10 × 12 for compressive strength training and 10 × 9 for tensile strength training. Compressive strength (CS) and tensile strength (TS) are the appropriate output training vectors of dimension 10 × 1 for compressive strength training and 10 × 1 for tensile strength training. Water (W), natural coarse aggregate (NCA), waste ceramic aggregate  determine neural networks’ power. ANN was trained using the Levenberg–Marquardt back-propagation algorithm. Many different ANN models were built in this study to evaluate the sensitivity of the ANN outcomes. Each of these ANN models was trained using 60% of the data points, and the trained ANN was validated and tested using the remaining 40%. In particular, 20% of the data points were utilized to validate the trained ANN and 20% of the data points were utilized for testing.Different ANN models were constructed and studied based on the above to determine the best ANN model for predicting the compressive and tensile strength of PC, WOC, and WOC-Hybrid concrete. Based on Pearson’s correlation coefficient values, the created ANN models were ranked in decreasing order. The optimal ANN for the PC, WOC, and WOC-Hybrid mechanical characteristics is shown in For the PC, WOC, and WOC-Hybrid mechanical characteristics, In the present paper, the MLR model was applied to predict two concrete characteristics, tensile strength and Compressive strength. A total of nine samples were used to predict the tensile strength (77% for training and 23% for test), and 12 samples were used to predict the compressive strength (75% for training and 25% for test).Due to the system’s complexity, it is difficult to determine the effect of a single parameter change on the model’s various output parameters. However, a parametric analysis was carried out to check the ANN and MLR models’ capability to capture the sensitivity of PC, WOC, and WOC-Hybrid concrete mix properties to individual constituents .The artificial neural network modeling results for all input parameters and all PC, WOC, and WOC-Hybrid models with a different number of hidden neurons indicated that elevated temperatures have the greatest effect on the TS of concrete .Artificial neural network modeling was used to determine the effect of elevated temperatures on the CS of concrete for all input parameters and all PC, WOC, and WOC-Hybrid models with a different number of hidden neurons .(a)Among all available training algorithms in the literature, the Levenberg–Marquardt algorithm produced the best ANN prediction of WOC strength.(b)It was determined that the optimal number of hidden layers for the top ten models is 1.(c)Initial weights significantly affect the results; varying the initial weights results in varying the optimal ANN architectures.The performance of the developed models by ANN can be drawn from the According to Based on the following results, the mathematical model to predict the tensile strength has the following form:2 achieves 0.9862 in the training phase and 0.9983 in the test phase.2 achieved 0.9715 in the training phase, and 0.9687 in the test phase.As with The performance of the developed models during training and test periods was assessed by calculating three performance criteria, namely, mean square error (MSE), root mean square error (RMSE), and mean absolute error (MAE). The formulas used for the calculation of the previous indicators is mentioned in (a)The concrete compressive strength which contains natural material (PC) is decreased by up to 11.61%, 18.91%, and 36.01% when exposed to a temperature of 100 °C, 200 °C, and 300 °C. In comparison, this reduction is about 8.48%, 16.72%, and 34.25% in the specimens containing waste ceramic material (WOC). Thus, it may be concluded that ceramic material contributes to the heat resistance of concrete compared with natural material because concrete with ceramic tiles have lower thermal conductivity than concrete with natural aggregates.Due to the increase in the transport properties of heated material, concrete with hybrid fibers (PVA + CR) showed a good effect on concrete compressive strength under elevated temperatures. The reductions in compressive strength in specimens containing hybrid fiber are about 7.15%, 14.55%, and 19.51% when exposed to 100 °C, 200 °C, and 300 °C, respectively.The concrete tensile strength which contains natural material (PC) is decreased by up to 19.21% and 35.91% when heated to 200 °C and 300 °C. In comparison, this reduction is about 14.18% and 30.60% in the specimens containing waste ceramic material (WOC).Hybrid Fibers (PVA–CR) affected concrete tensile strength at elevated temperatures positively. This is because heat transmits more uniformly in the concrete reinforced with hybrid fibers and the cracks caused by a thermal gradient in concrete decrease, improving concrete behavior under tensile strength tests. The reductions in tensile strength in specimens containing hybrid fiber are about 10.26% and 17.10% when exposed to temperatures of 200 °C and 300 °C, respectively.Concrete crack width and propagation develop primarily at the interface between waste material particles and the cement matrix.Experimental Analysis(b)Machine Learning (ML) models such as ANN and MLR can evaluate concrete’s mechanical properties. It was demonstrated that the developed ML model was successfully trained, validated, and tested.Concrete is a complex material, and there is a correlation between many factors. ML is a highly interconnected system that can learn the nature of complex interrelationships between independent and dependent variables. As a result, the models could evaluate the compressive and tensile strength at 28 days.The ANN and MLR models’ capability to evaluate the effect of elevated temperatures between 100 °C and 1000 °C on the properties of PC, WOC, and WOC-Hybrid concrete was mentioned.2 and MSE, and through visual assessment using scatter plots and line and bar diagrams. It has been found that best model performance between machine learning models in the training phase was registered for multiple linear regression (MLR), where the R2 value achieve achieved 0.9715 in the training phase and 0.9687 in the test phase.The ML models were assessed using statistical tools, including RIt would also be helpful to conduct studies on benchmarking of different prediction models. It is also suggested that ANN and MLR models be applied with different properties and materials parameters. In future work, we will use these techniques in different areas. We shall also discover possible enhancements to the method, such as adding different percentages of waste materials such as waste rubber and study their strength. Additionally, we shall encompass these approaches to the cooperative prediction of multiple parameters.Machine Learning Model AnalysisThe purpose of this study was to determine whether it was possible to increase the heat resistance of concrete exposed to high temperatures by developing a new concrete generation proposed by the authors (WOC concrete + WOC-Hybrid concrete), and to assess the ability of machine learning models (ANN and MLR) to predict the strength (compressive and tensile) of these types of concrete using a MATLAB program. The following conclusions can be drawn from the results of the experimental and computational test:


Flexural strength of concrete is an important property, especially for pavements. Concrete with higher flexural strength has fewer cracking and durability issues. Researchers use different materials, including fibers, polymers, and admixtures, to increase the flexural strength of concrete. Silicon carbide and tungsten carbide are some of the hardest materials on earth. In this research, the mechanical properties of carbide concrete composites were investigated. The silicon carbide and tungsten carbide at different percentages  by weight of cement along with hybrid silicon carbide and tungsten carbide (2% and 4%) were used to produce eleven mixes of concrete composites. The mechanical tests, including a compressive strength test and flexural strength test, along with the rapid chloride permeability test (RCPT), were conducted. It was concluded that mechanical properties were enhanced by increasing the percentages of both individual and hybrid carbides. The compressive strength was increased by 17% using 4% tungsten carbide, while flexural strength was increased by 39% at 4% tungsten carbide. The significant effect of carbides on flexural strength was also corroborated by ANOVA analysis. The improvement in flexural strength makes both carbides desirable for use in concrete pavement. Additionally, the permeability, the leading cause of durability issues, was reduced considerably by using tungsten carbide. It was concluded that both carbides provide promising results by enhancing the mechanical properties of concrete and are compatible with concrete to produce composites.  Concrete is generally the most utilized construction material. It is a user-friendly, economical, easily moldable, and highly efficient structural material. However, it has some drawbacks, such as low modulus of elasticity, inconsiderable elastic range, low tensile and flexural strength, and permeability (due to which corrosion is susceptible). Therefore, concrete is usually reinforced to overcome such demerits using metals, polymers, and fibers ,2. ThereMetallic carbides can exist naturally or are produced as byproducts of different industries. However, carbides have distinctive properties such as hardness, abrasiveness, tensile strength, neutron attenuation, heat resistance, and chemical inertness. They are added in metal to make the composites hard, corrosion and chemical resistant, and manufacture different tools . CarbideSilicon carbide (SiC) is incredibly hard and found scarcely in nature; however, it is a synthesized crystalline compound of silicon and carbon. It has high strength and chemical inertness. Silicon carbide produces strong materials such as sandpapers, crushing equipment, and cutting machinery .When used in mortars and concretes, SiC decreases the fluidity and exhibits lower early strength but higher late strength. It reduces the shrinkage rate of concrete. The cement paste hydration process is affected, and the microstructure is densified by SiC addition . The useSilicon carbides are also found compatible to make aggregates for concrete. As sand replacement material, they improve the microstructure of concrete . PundienRecently SiC was investigated for concrete production pertaining to particular applications ,15,16. STungsten carbide (WC) is useful because it is a radiation protection material. WC in nano powder form provides higher protection from radiation and better compressive strength. Moreover, it has excellent wear resistance and hardness  and exceThe WC network causes specific plasticity and a high range of ductility properties while preserving the high stiffness. It has high corrosion resistance, and when exposed to the air, WC shows corrosion signs at temperatures over 600 °C. WC is also an electromagnetic radiation absorber . WC is utilized alone or mixed with different metal composites to enhance strength. This ceramic carbide is also used to enhance the mechanical properties of different composites due to its strength, chemical stability, rigidity, and high-temperature resistance . WC is aTungsten and tungsten carbides provide excellent gamma radiation shielding and neutron absorption . WC provIn this study, the effect of carbides (silicon carbide and tungsten carbide) on the mechanical properties and permeability of concrete composites were studied, and their compatibility with concrete was determined. Both carbides were added individually at 1%, 2%, 3%, and 4% of cement weight in concrete. The hybrid combination of both carbides at 2% and 4% was also used. The concrete density, compressive strength, corrosion properties, and flexural strength were investigated.Ordinary Portland cement (Pioneer Cement) was used to prepare carbide concrete composites. Properties of cement used are presented in The color and true density (density excluding pores) of silicon carbide and tungsten carbide used in the investigation are presented in A total of 11 mixes of concrete were produced, as shown in For each mix preparation, sand (fine aggregate) and crushed stone (coarse aggregate) were dry mixed for 1 min. Cement, carbides, and half of the water were added and mixed for 2 min. After a 1-min gap, the remaining half water mixed with superplasticizer was added and mixed for a further 2 min. A constant water–cement (w/c) and polycarboxylic-based superplasticizer content were used. Mixes were poured into molds and compacted by a vibrator. After twenty-four hours, samples were demolded and cured in water until the 28th day of casting.The bulk density of each fresh concrete specimen was calculated by taking the ratio of the weight of four samples to the volume of samples from each batch. For this purpose, after casting of concrete, the pans with known volumes were filled, compacted, and weighed. Concrete mix density was determined within a short time after its production.Four cylinders (4 × 8 inches) were cast for each batch for the compressive strength test and four prisms (4 × 4 × 20 inches) for the flexural strength test. Two cylinders (4 × 2 inches) were used to conduct a rapid chloride permeability test (RCPT). RCPT provides information about the permeability of the concrete to allow chloride ions to pass through it under 60-volt potential. For this purpose, two of 2 × 4 inches cylinders are first prepared using a vacuum desiccator and water. After sample preparation, the sample was fixed between two cells, one with NaOH solution and the other with NaCl solution. Voltage is applied to let the chloride ion pass through 2-inch concrete samples. The charge passed (coulombs) during 6 h indicates the permeability of the concrete. Finally, the rapid chloride permeability test (RCPT) was carried out on concrete samples. FESEM images were studied to find out the reasons for the behavior of carbide composites. For this purpose, images at different magnifications at 10 KV EHT were obtained. The images found better for reasoning purpose was used in the study.The results obtained through testing on concrete samples are presented and analyzed. SiC is also one of the hardest ceramic materials ,32. It wIt was observed that the hybrid WC and SiC in concrete enhanced the compressive strength considerably. It might be due to better interphase developed due to carbides and higher density due to better packing of particles, leaving fewer voids behind. The enhancement in compressive strength may also be attributed to the carbides’ intrinsic compressive strengths as concrete constituents.Strength is the most important property of concrete. The concrete generally has weak flexural strength ,34,35. FThe impact of carbides in concrete with different percentages on flexural quality is shown in The flexural strength of concrete was significantly increased by increasing both individual and hybrid carbides. However, SiC showed a very high flexural strength than WC, unlike compressive strength. WC showed an increase in flexural strength up to 20%, while SiC showed a 39% increase in strength. It can be easily attributed to the shapes, size, and form used during testing. WC has very high tensile strength, but it was used in small fiber form. It increased the flexural strength considerably, even when used in a minimal amount. Flakes of SiC flakes did not allow prism to fail easily, and they provided enough reinforcement for increasing the flexural strength of concrete. Although it has very high tensile/flexural strength, WC could not transfer tensile stresses effectively due to its tiny size of 3 to 4 mm. The higher intrinsic strength of carbides led to the higher flexural strength of composites.Additionally, the abrasive resistance did not allow composite particles to move away easily . It resuThe hybrid carbide WC and SiC showed high flexural strength. WC is usually mixed with other metals because of its capacity for synergistic effects ,40,41,42p < 0.05 (and near to 0) indicates that the alternate hypothesis is true, and the effect of fiber percentage is so significant that it can not be just by chance. For WC, the p-value is 0.028  that by changing the percentage of carbides, flexural strength was changed significantly. is 0.028 , and foris 0.010 . Therefo2) value near 1 suggests a good fit of predicted and experimental values. 2 is 0.906 for WC-containing composites, proving the good fit of the model developed. 2 is 0.96 for SiC containing composites, proving the excellent fit of the model developed.Root mean square error  and tungsten carbide (WC), on the compressive strength, flexural strength, and permeability of concrete was investigated. Both carbides were used individually and in the hybrid form added up to 4% of cement weight to produce carbide concrete composites.The increase in the percentage of both carbides, individually and hybrid form, increased the compressive strength and flexural strength of concrete. Though both carbides increased the compressive strength, WC concrete composites showed higher compressive strength  than SiC composites (6% increase in compressive strength). Contrarily, SiC showed very high flexural strength (39%) compared to WC (20%), although both carbides enhanced flexural strength noticeably. The ANOVA analysis proved the significant effect of both carbide contents on the flexural strength of concrete. This property makes WC and especially SiC desirable for pavement concrete.Additionally, the Rapid chloride permeability of flaky SiC concrete composite was higher. However, WC and hybrid composites showed relatively lower permeability when used at 4%. FESEM images also verify the results. It is evident that both tungsten and carbides enhance the properties and are quite compatible with concrete. However, hybrid carbide composites provided a synergetic effect by enhancing the mechanical strength, especially flexural strength, and mitigating the permeability. The composite properties were enhanced directly by increasing percentages of carbides up to 4% addition. It implies that investigation can be carried out on higher percentages of both carbides. The work can be further extended to concrete composite for other unique properties of their constituent carbides, including neutron shielding, bulletproofing, electromagnetic radiation barriers used in nuclear reactors, and 3D printing. The positive results, if obtained, may pave a path for the production of special performance-based cement and concrete.


Dekker,” not “Jan-Willem T. Dekker.” This article has been corrected.In the Original Investigation titled “Predictors of 30-Day Mortality Among Dutch Patients Undergoing Colorectal Cancer Surgery, 2011-2016,”


Conclusion: Antibiotic overuse could be evaded in PICU using simple bedside screening tools and clinical characteristics, particularly in poor resource settings among children with diarrhea. Background: Antibiotic exposure in the pediatric intensive care unit (PICU) is very high, although 50% of all antibiotics may be unnecessary. We aimed to determine the utility of simple bedside screening tools and predicting factors to avoid antibiotic overuse in the ICU among children with diarrhea and critical illness. Methods: We conducted a retrospective, single-center, case-control study that included children aged 2–59 months who were admitted to PICU with diarrhea and critical illness between 2017 and 2020. Results: We compared young children who did not receive antibiotics  during ICU stay to those treated with antibiotics . For predicting the ‘no antibiotic approach’, the sensitivity of a negative quick Sequential Organ Failure Assessment (qSOFA) was similar to quick Pediatric Logistic Organ Dysfunction-2 (qPELOD-2) and higher than Systemic Inflammatory Response Syndrome (SIRS). A negative qSOFA or qPELOD-2 score calculated during PICU admission is superior to SIRS to avoid antibiotic overuse in under-five children. The logistic regression analysis revealed that cases were more often older and independently associated with hypernatremia. Cases less often had severe underweight, altered mentation, age-specific fast breathing, lower chest wall in-drawing, adventitious sound on lung auscultation, abdominal distension, developmental delay, hyponatremia, hypocalcemia, and microscopic evidence of invasive diarrhea (for all,  Appropriate use of antimicrobial agents is the cornerstone of effective antimicrobial stewardship programs and has become a focus of patient safety, quality assurance, and health care outcomes. The Intensive Care Unit (ICU) deals with critically ill patients, and infections are among the most frequent causes of hospitalization among patients in the ICU. Thus, antibiotic burden in ICU is very high; 66 to 77% of all ICU patients and 84–100% with an ICU stay of more than 48 h are exposed to at least one class of broad-spectrum antibiotic . As the However, 50% of antibiotic prescriptions were inappropriate and could be avoided . The sitImproving diagnostic tools, and discriminating against bacterial infections from viral infections and other non-infectious mimics, is the eventual solution to reducing unnecessary antibiotic initiation in the ICU. However, bacterial isolation by culture and sensitivity, the gold standard test, is time-consuming and has low sensitivity for slow-growing and fastidious microorganisms . AlthougSeveral scoring systems have been developed to predict suspected infection or sepsis as a surveillance tool, and a positive score might be of value to identify infection promptly. Historically, the systemic inflammatory response syndrome (SIRS) criteria were considered to be fundamental to the diagnosis of inflammation and infection , althougInformative studies regarding whether clinicians could adopt a ‘watchful waiting’ approach safely and confidently for a subset of PICU patients in LMIC are still lacking. ICU physicians seldom consider a watchful waiting approach; in contrast, they prefer to overuse broad-spectrum antibiotics when faced with a non-reassuring characteristic . Thus, oIn total, 2089 children aged 2 months to 59 months were admitted to the ICU of Dhaka Hospital between 2017 and 2020; 268 (12.8%) children did not receive any antibiotics, and we excluded 104 children because they were treated with antibiotics at the emergency ward or after being transferred to another ward.A final cohort of 510 children formed the analyzable data, where 164 were cases (no antibiotic group), and 346 were controls (antibiotic group).Bivariate analysis revealed that the cases were more often older, presented with acute watery diarrhea, history of vomiting, seizure, and hypernatremia than the controls .In contrast, cases less often presented with SAM, severe underweight, severe stunting, dehydration, age-specific fast breathing, lower chest wall in-drawing, hypoxemia, adventitious sound on lung auscultation, abdominal distension, altered mentation, developmental delay, and congenital heart disease. The mortality rate was significantly lower amongst the cases compared to controls .Similarly, hyponatremia, hypokalemia, hyperkalemia, hypocalcemia, leukocytosis, and microscopic evidence of invasive diarrhea were less frequent among cases than their corresponding peers . LaboratOf the included children, the frequency of Systemic Inflammatory Response Syndrome (SIRS), quick Sequential Organ Failure Assessment (qSOFA) score and quick Pediatric Logistic Organ Dysfunction Score-2 (qPELOD-2) negativity was 311/510 (61%), 452/510 (89%), and 475/510 (91%), respectively. Cases more often had SIRS, qSOFA, and qPELOD-2 negative children compared to controls .For predicting a no antibiotic approach, a negative qSOFA and a negative qPELOD-2 both displayed a very high sensitivity of 95.9% (95% CI 91.8 to 98.3) and 95.9% (95% CI 91.8 to 98.3), respectively, and low specificity of 17.1% (95% CI 13.2 to 21.4) and 13% (95% CI 9.6 to 17). Negative SIRS score had an intermediate sensitivity and specificity .The AUROC curve of a negative Systemic Inflammatory Response Syndrome (SIRS), quick Sequential Organ Failure Assessment (qSOFA) score, and quick Pediatric Logistic Organ Dysfunction-2 (qPELOD-2) score is presented in p-value = 0.023). However, the AUROC curve between SIRS and qSOFA  as well as between qSOFA and qPELOD-2  were comparable , quick Sequential Organ Failure Assessment (qSOFA) and quick Pediatric Logistic Organ Dysfunction-2 (qPELOD-2) scores for implementing a no antibiotic approach in PICU. We also focused on the associated factors and outcome of children who did not receive antibiotics.Some noteworthy observations were: first, we observed both negative qSOFA and qPELOD-2 scores showed higher sensitivity to identify children suitable for implementing a no antibiotic approach, although the observations were compromised by lower specificity. Second, the no antibiotic approach was more often implemented in older children and children with hypernatremia. Third, this approach is implemented less often in children with severe underweight, altered mentation, age-specific fast breathing, chest wall in-drawing, adventitious sound on lung auscultation, abdominal distension, developmental delay, hyponatremia, hypocalcemia and microscopic evidence of invasive diarrhea.Although clinicians often struggle to decide when to initiate antibiotics in critically ill children in ICU, still no study has examined the utility of negative SIRS, qSOFA, and qPELOD-2 scores as a bedside screening tool to overcome this challenging situation. We found negative qSOFA and qPELOD-2 with <2 scores have high sensitivity of 96% for predicting a no antibiotic approach, though no scoring system has high specificity.However, considering AUROC, negative SIRS (<2 scores) is equivalent to qSOFA and more accurate than qPELOD-2. A previous study examining the performance of qSOFA demonstrated that the prevalence of PICU transfer and or mortality was 2% with qSOFA < 2 scores compared to 22.5% with qSOFA ≥ 2 in children presented to the emergency department . The sepWe found that antibiotic prescriptions were less in relatively older children. In this context, young infants are at increased risk for severe infection and often receive empirical antibiotic therapy. Rogawski et al. showed that antibiotic use was common in the first 6 months of life, even at the community level . The assShigella infection, associated with considerable mortality and morbidity [Similarly, children showing microscopic evidence of invasive diarrhea and dysentery (visible blood in stool) should be treated with antibiotics  as Shigeorbidity , is suspNone of our cases had SAM. Several studies have revealed a high prevalence of infections among children hospitalized for SAM, and routine antibiotic therapy is recommended for such children . ChildreThe association of less implication of a no antibiotic approach in children with age-specific fast breathing, chest wall in-drawing, adventitious sounds on lung auscultation is understandable. In LMIC, the diagnosis of pneumonia is based on cough and or breathing difficulty with clinical signs such as fast breathing and lower chest wall in-drawing. The presence of hypoxemia is a sign of severe pneumonia . World Hα, interleukin (IL)-1, IL-6; hypoparathyroidism, vitamin D deficiency, or resistance [We found that children who did not receive antibiotics less often had altered mentation, abdominal distension, hypocalcemia, and hyponatremia. Earlier studies have shown that altered mentation and abdominal distension in critically sick children might represent sepsis  and shousistance . Similarsistance .Our study result might not be generalizable because it was conducted in a single-center PICU of a diarrheal disease hospital. We comprehend that this is an important limitation of the study since results may not be extrapolated to other PICUs where patients with other syndromes are admitted. In developing countries, the PICU mortality ranges from 13 to 25% ,41, thouWe conducted this study in a single center diarrheal-hospital, the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh , located in Dhaka, Bangladesh. This hospital is the largest diarrheal disease hospital globally and provides care for approximately 150,000 patients annually. Among them, sixty-two percent are aged below five years. Patients presenting with diarrhea with or without other comorbidities can seek health care at this hospital. The emergency department has a well-organized triage for sorting and prioritizing patients for care and initiating appropriate therapeutic measures. More than 90% of patients are managed in the short-stay ward, where the median duration of stay is 18 h. Only 1–2% of individuals needing immediate resuscitation at triage or patients with a critical illness or those with clinical deterioration in the short-stay ward or longer-stay ward are transferred to the ICU. The median duration of stay at the ICU is five days.We conducted a retrospective observational study with an unmatched case-control design. Children aged 2–59 months admitted to the ICU of Dhaka Hospital with suspected critical illness between January 2017 and January 2020 were eligible for enrolment. We retrieved data through the hospital’s electronic database of the patient information system. Patients were considered to have critical illness if they met ICU transfer criteria following hospital guidelines  and stayIn contrast, controls were children who received one or more intravenous antibiotic therapy during their stay at ICU. We assumed 85% exposure of acute watery diarrhea (AWD) in controls to compare the percentage of cases and controls, considering the high prevalence of AWD among children with high infection burden countries . To provWe developed a pretested case report form for the acquisition of relevant data. We reviewed all medical records, including the initial presentation to the triage, inpatient course, and outcome. Data on demographics , vital signs , anthropometric measurements, clinical features  and outcome were collected. We also examined laboratory results, including complete blood count, hypernatremia, hyponatremia, hyperkalemia, hypokalemia, metabolic acidosis, hypocalcemia, microscopic evidence of invasive diarrhea, UTI, and CNS infection, as well as bacterial pathogens from blood and stool culture for those helped with a no antibiotic approach.3 or <4000/mm3 or bandemia >10%) in the absence of dehydration. SIRS score must include either temperature or white blood cell abnormality. qSOFA [We calculated SIRS, qSOFA, and qPELOD-2 scores based on the first measured values after ICU entry. SIRS  was defiy. qSOFA  criteriay. qSOFA  criteriaAll children admitted to ICU were initially managed by trained ICU physicians following hospital guidelines. All children received standard treatment, including noninvasive or invasive oxygen therapy, intravenous fluid, suitable antibiotics (if necessary), anti-seizure therapy for seizure, and other supportive management. We adopted a no antibiotic approach among the children who did not have severe acute malnutrition, sepsis , severe 2 was <17.0 mmol/L, hypocalcemia if serum calcium was <2.12 mmol/L.We defined severe stunting with a length or height for age z-score (LAZ/HAZ) ˂ −3, severe underweight with weight for age z-score (WAZ) < −3 but ≥−4 ensuing WHO growth standards . We defiU test, as appropriate, was used to analyze the continuous variables. The Chi-square test or Fisher’s exact test was used to compare differences in proportions. We applied multiple logistic regression analysis to identify the no antibiotic approach’s determinants and the evolution of variables having a p-value < 0.05 at the bivariate analysis; OR were adjusted, and 95% confidence intervals were calculated.We analyzed data using the Stata v13.0 for Windows . We assessed the normality of distribution with the Shapiro–Wilk test. Continuous variables were expressed as mean ± SD or median (IQR), categorical variables as frequency and percentages. When comparing the no antibiotic and antibiotic groups, Student’s t-test or Mann–Whitney’s p-value of <0.05 was considered statistically significant.The receiver operating characteristics (ROC) curve was created for each score. We determined each scoring system’s predictive accuracy using the AUROC (area under the receiver operating characteristics curve). We calculated sensitivity, specificity, positive and negative predictive values using contingency tables for every score. We compared the sensitivity and specificity of negative SIRS, qSOFA, and qPELOD-2 scores for no antibiotic approach using McNemar’s test and the AUROC curve using DeLong’s method . A p-valThis is the first study in the epoch of antibiotic resistance to determine the utility of bedside screening tools and associated factors that might help PICU clinicians avoid overusing antibiotics in children with diarrhea and other comorbidities, especially in resource-poor settings. Based on our findings, we may propose that PICU clinicians adopt the no antibiotic or watchful waiting approach in children with a negative (score < 2) qSOFA or qPELOD-2 score calculated during PICU admission. However, in addition to these simple screening tools, physicians should judiciously implement a no antibiotic approach by careful diagnosis and severity assessment based on underlying pathophysiology to limit harmful consequences in PICU. However, as this result may be applicable for children with diarrhea in PICU, future prospective studies involving larger populations in different settings may consolidate our observation.


IgG4-related disease mainly manifests as organomegaly and is accompanied by tissue fibrosis :213, 2019) which is frequently confused with tumour :1375–8, 2020). There are few reports with of IgG4-related disease with the first clinical manifestation involving the stomach.We present the case of 46-year-old male patient with a “stomach tumour” as the first manifestation of IgG4-related disease. Gastroscopy showed a mass in the stomach, however, the pathology result was chronic inflammation with IgG4 positivity. CT scans of abdomen showed that the stomach wall was thick, the head of the pancreas was swollen, and retroperitoneal fibrosis was severe.The serum IgG4 level was 75 g/L .After treatment with methylprednisolone for one month, the symptoms were greatly relieved.To reduce the suffering of patients and relieve their financial burden, we should consider the possibility of IgG4-related disease when the initial manifestation is a stomach mass. IgG4-related disease is immune-mediated chronic inflammation that is diagnosed by clinicopathological presentations of enlarged organs, elevation of serum concentrations of IgG4 and pathological findings such as a typical dense lymphoplasmacytic infiltration enriched in IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis , 2. Panc2. Gastroscopy showed a mass in the stomach  was 18.32 kg/mach Fig. . The serach Fig.  were perach Fig. ,the headach Fig. .The seruThe reason for IgG4-related disease is unknown, and the pancreas, biliary tract, lymph nodes, lungs, livers, pleura, kidneys and other organs can been involved  and DumaWhen IgG4-related disease involves the stomach, the swelling of the stomach is similar to that of a tumour. The results of gastric mucosa biopsy, serum IgG4 level, and organomegaly or tissue fibrosis must be combined to confirm the diagnosis of IgG4-related disease. However, the prospective cohort study showed that Chinese IgG4 disease patients had a 2.78-fold increased risk of having malignancy, and the most common malignancy site was the gastrointestinal tract . IgG4-reWe should consider the possibility of IgG4-related disease and alert the potential for malignancy when a mass is seen in the stomach, to reduce the suffering for patients and the financial burden for their families.


This study investigates the feasibility evaluation of smart PZT-embedded sensors for impedance-based damage monitoring in prestressed concrete (PSC) anchorages. Firstly, the concept of impedance-based damage monitoring for the concrete anchorage is concisely introduced. Secondly, a prototype design of PZT-embedded rebar and aggregate  is chosen to sensitively acquire impedance responses-induced local structural damage in anchorage members. Thirdly, an axially loaded concrete cylinder embedded with the smart rebar–aggregate is numerically and experimentally analyzed to investigate their performances of impedance monitoring. Additionally, empirical equations are formulated to represent the relationships between measured impedance signatures and applied compressive stresses. Lastly, an experimental test on a full-scale concrete anchorage embedded with smart rebar–aggregates at various locations is performed to evaluate the feasibility of the proposed method. For a sequence of loading cases, the variation in impedance responses is quantified to evaluate the accuracy of smart rebar–aggregate sensors. The empirical equations formulated based on the axially loaded concrete cylinder are implemented to predict compressive stresses at sensor locations in the PSC anchorage. In prestressed concrete (PSC) structures, anchorage zones resist particularly high compressive forces induced by pre-tensioned strands ,2. Due tCurrently, periodic visual inspection is commonly practiced for inspecting surface defects of concrete structures . Recently, vision-based monitoring has been applied to automatically identify crack or spalling in PSC structures via deep learning techniques ,12. HoweTo overcome this limitation, various structural health monitoring (SHM) techniques have been developed by using sensing and analysis systems to enable real-time precautions. Vibration-based approaches have been successfully implemented to monitor structural defects in PSC structures by utilizing changes in vibration responses  ,14,15,16Among local SHM methods, impedance-based methods have been implemented for detecting various damage types, such as concrete damage ,21,22, pResearch attempts have been made to monitor damage in a concrete structure using PZT patches affixed on its surface . The impAs an alternative, a PZT sensor embedded in a concrete structure could be more suitable for monitoring impedance features sensitive to the occurrence of an incipient crack in a concrete body. There exist at least three reasons to develop PZT-embedded monitoring techniques for the PSC anchorage. Firstly, the PZT-embedded sensor can directly catch the variation of impedance signals induced by stress changes by knowing that the stress change yields the change in impedance responses . SecondlAs surveyed in the literature, the damage types in PSC structures can be classified as tendon corrosion, prestress loss, and concrete cracks. In this study, the target damage was selected to verify the proposed sensors. Therefore, the prestress-force variation during the installation of prestressing strands was selected to evaluate the practicability of a smart rebar and a smart aggregate. Firstly, the fundamentals of the impedance measurement via PZT-embedded sensors are concisely described for the anchorage zone. Secondly, two design samples of a PZT-embedded smart rebar and a PZT-embedded smart aggregate are selected to acquire the change of impedance responses sensitive to incipient defects in the PSC anchorage. Thirdly, numerical and experimental analyses are conducted on a concrete sample embedded with the smart rebar–aggregate to analyze its performance of impedance monitoring. For a sequence of loading cases, the change in impedance signatures is quantified using statistical RMSD (root mean square deviation) indices to analyze the sensitivity of the smart rebar–aggregate to the force changes. Lastly, an experimental test on a full-scale concrete anchorage embedded with smart rebar–aggregates at various locations is performed to evaluate the feasibility of the proposed method. For a sequence of loading cases, the variation in impedance responses is quantified to evaluate the accuracy of smart rebar–aggregate sensors. The empirical equations formulated based on the axially loaded concrete cylinder are implemented to predict compressive stresses at sensor locations in the PSC anchorage.b = 200 × 200 × 30 mm), and a concrete block (height × width × length = H × W × L = 460 × 460 × 500 mm). A duct (φ 110 mm) at the center of the concrete was used for passing steel-strands , and the tensile strength was selected as tσ = 2.33 MPa (0.1cσ). Moreover, the material properties of reinforcement were selected based on the recommendations of the company, VSL [ands see b. The anands see . The comany, VSL   examined at points L1 and L2 (its position can be seen in σzz) at point L1 yielded a higher value (about 24 MPa) than that at point L2 (14.8 MPa). Furthermore, the lateral stresses (σxx or σyy) at point L1 also experienced higher variation than those at point L2. It is known that von Mises stress is calculated from the root square of stress components , thus leading to this stress always having a positive value. The von Mises stress is commonly used to determine the yield states of ductile materials. For the anchorage zone, stress components were significantly different among them (see them see . In thisthem see a.F(ω) was produced due to the inverse piezoelectric effect under the applied voltage V(ω) to the PZT sensor. The force F(ω) was transferred into a local region of the inspected structure. Instantaneously, the structural response was transferred to the PZT patch to produce a voltage signal . In practice, an output electric current, I(ω), was measured for the determination of EM impedance signals.Once the external load N alters , it causes changes in the modal parameters  of the PZT interface and the host structure. As shown in Z(ω), is determined by the ratio of the input voltage and the output current [j, ω, and pA are the imaginary unit, the excitation frequency, and the PZT-geometric parameters’ constant. aZ and sZ are the SM impedance of the PZT patch and one of the interface–host structures. The terms 31d, Z(ω), represents the mechanical properties of the interface structure. Assuming that the structural mechanical (SM) impedance of the PZT-embedded interface is constant before and after the damaging events, changes in the structural properties can be determined by quantifying the variations of impedance responses (Z(ω)).The EM impedance,  current :(1)Z(ω)=m (mass), k (damping coefficients), and c (spring stiffness), in which the symbols i and s represent the interface and the structure, respectively. extf, the governing equation of motion at the PZT-driving point for the 2-DOF impedance model can be formulated as follows:im and sm, respectively. The coupling SM impedance, sZ, of the PZT interface and the host structure at the PZT driving point is determined as follows [K11, K12, and K22 are the following dynamic stiffness coefficients K11= −ω2i + jωci + kim, K12i − ki= −jωc, and K222ms + jω= −ω(i + csc) + (i + ksk). The stiffness coefficients depend on the structural parameters of the inspected structure and interface. Assuming there are no changes in the PZT patch electric and mechanical properties, any external effects  would cause changes in the measured impedance responses of the interface structure. Thus, any changes in the monitored structure can be quantified using the impedance features of the PZT-embedded interface.Under a harmonic excitation  follows : (3)Zs, the stress fields are uniformly distributed for both tensile and compressive stresses. As previously analyzed in To monitor the impedance-responses-induced structural damage, the PZT-embedded smart interfaces can be placed at potential damage locations . Figure Z(iω) and *Z(iω) represent the real-part impedance signals obtained at the intact and damaged states at ith, a sweeping frequency in total measured frequency point N. In general, the RMSD magnitudes are only beyond zero when structural damage occurs. However, due to the uncertainties in experimental tests and computational error, the RMSD values could be greater than zero, even when no damage exists. To deal with the problem, a control limit (CL) is commonly used to assure the determination of damage existence [μ and the standard deviation σ of impedance signatures are calculated from an ensemble of the RMSD indices at the intact case. The CL with 3σ represents a damage identification with a confidence level of 99.7%.Changes in the impedance signals between the intact state and a post-damage state are quantified using the following RMSD (root mean square deviation) index to characterize damage in the concrete anchorage : (4)RMSDxistence , as follAs shown in max 25) was utilized to make the smart aggregate sensors. As shown in The sensitivity of signal acquisition was numerically investigated for the smart sensing interfaces , as seen in The FE model was meshed with 32,319 elements  were placed at the center of the concrete sample, and their distance to each end of the concrete surface was 60 mm. To simplify the FEM of the SR, the nodes and ribs of the steel bar  and the SR  to 110 kN (N6) with an interval of 20 kN see , correspAs resonant impedance signals comprise meaningful structural parameters at the PZT-driven point ,49, the cσ = 23.3 MPa (compressive strength), as listed in The smart rebar–aggregate was experimentally evaluated on a concrete sample embedded with the smart interfaces, as schematized in The variations in impedance signals under the loading cases were quantified using the RMSD damage metric, as depicted in As shown in c). This observation is consistent with the behavior of the normal concrete [c, the RMSD magnitudes of the smart rebar rapidly increased, that is, the RMSD index at loading N6  was larger than that of loading N5 . Meanwhile, the RMSD value of the smart aggregate slightly increased, as shown in For both the SR and the SA, the relationships between the compressive loads (N1–N6) and the RMSD damage metrics were linear once the force was lower than 70 kN  orthogonal stirrups 6 φ 10, @ = 60 mm, and l = 1280 mm; (3) orthogonal stirrups 8 φ 10, @ = 60 mm, and l = 1760 mm; and (4) longitudinal rebars 16 φ 10 and l = 820 mm  are listed in ρ = 7850 kg/m3 (mass density), ν = 0.33 (Poisson’s ratio), and E = 200 GPa (elastic modulus). The seven-wire strands with φ of 15.2 mm  and a length of 6.0 m  had the following material properties: E = 195 GPa (Young’s modulus) and pkF = 260.4 kN (breaking load).The concrete mix for the concrete block , each of the nine strands were separately pre-tensioned with a small force (about one kN) to set up the prestressing strands and anchorage zone. As the intact baseline for the experiment, all the load cells were initialized by setting zero force (0 kN). In the second test case (PS2), each of the nine strands were tensioned up to about 40 kN. The sequence of tensioning strands was conducted as follows: Strand nine (the center strand), Strands one and five (two outer strands), Strands three and seven, Strands two and six, and Strands four and eight see e. In theThe HIOKI 3532 impedance analyzer was utilized to measure the impedance responses of the PZT sensors using an exciting range of 100–600 kHz . Four ensembles of impedance signals were recorded for each test case (PS1–PS4) to calculate. During the impedance measurement, the laboratory temperatures were kept at about 21.5 °C (air conditioners) to minimize the temperature effects on the impedance features. From the smart rebars, impedance signals were measured in the range 200–400 kHz for the loadings PS1~PS4, as shown in From the four smart aggregates, the impedance signals were measured in the range of 100–300 kHz for the same loading cases. As shown in From the surface-bonded PZT1 and PZT2, impedance signals were measured in the range of 100–300 kHz for the loading cases see . The chaThe statistical damage metric RMSD was utilized to quantify the variations in the impedance responses for loading cases. The ensembles of signals at the first test cases (intact case) were utilized to calculate the CL for each sensor. For each of the prestressing cases, PS2~PS4, four ensembles of measured data were used to evaluate the deviation of the impedance data. For the calculation of the RMSD indices, the resonant frequency ranges, selected as 200–400 kHz for the smart rebars, 100–300 kHz for the smart aggregate, and 100–300 kHz for the surface-bonded sensors, were utilized, as shown in As shown in As shown in As shown in The empirical equations (see Equations (6)–(9)) of the measured impedance signals with respect to the compressive stresses applied on the concrete cylinder were utilized to predict the compressive stresses in the PSC anchorage subjected to the loading cases PS1~PS4. For the four smart rebars (RB.1-1~RB.2-2) installed in the PSC anchorage, compressive stresses were predicted by applying RMSD values quantified from the measured impedance signatures see  to the eFor the four smart aggregates (AG.1-1~AG.2-2) installed in the PSC anchorage, the compressive stresses were predicted by applying the measured RMSD values of impedance signals see  to the eThese results provide at least four important things. First, the local impedance-based estimation of compressive stress variation was at a single sensor location. For example, the location at smart rebar RB.2-2 varied from 1.98 to 13.7 MPa see b when thPrestressing force variation in the nine-strands concrete anchorage was successfully detected using the impedance signatures obtained from the smart rebars, the smart aggregates, and the surface-mounted PZT sensors. The sensitivity of the surface-bonded sensors was less than that of the embedded sensors. It is noted that the bearing plate embedded in concrete led to a significant variation of stresses at its near field as compared to the concrete surface. The result suggests that the smart rebar–aggregate sensors should be implemented for condition monitoring of the anchorage zone.Comparatively, the PZT-embedded smart rebars gave better indications for prestressing force variations. As shown in Empirical relationships between the impedance features and the compressive stresses applied were formulated on the basis of the axially loaded concrete cylinder, as shown in The patterns of impedance features were slightly different for a pair of smart rebar–aggregate sensors , as shown in Furthermore, the sensitivities of embeddable PZT sensors depend on the material properties of their components  ,30. ThusThis study investigated the feasibility evaluation of smart PZT-embedded sensors for impedance-based damage monitoring in the PSC anchorage. The concept of impedance-based damage monitoring for the concrete anchorage was concisely introduced. The sample of a PZT-embedded rebar and aggregate was designed for impedance monitoring sensitive to incipient defects in the PSC anchorage. The axially loaded concrete cylinder embedded with the smart rebar–aggregate was numerically and experimentally analyzed to investigate the performance of impedance measurement. Additionally, empirical equations were formulated on the relationships between the measured impedance signatures and the compressive stresses applied. The experimental test on a real-scale anchorage zone was performed to investigate the practicality of smart rebar–aggregate sensors positioned at various locations. For a sequence of loading cases, the variation in impedance responses was quantified to evaluate the accuracy of smart rebar–aggregate sensors. The empirical equations formulated based on the axially loaded concrete cylinder were implemented to predict compressive stresses at sensor locations in the PSC anchorage. Based on the results, it can be concluded that (1) the feasibility of the smart rebar–aggregate sensors was successfully evaluated by monitoring the impedance features sensitive to prestress forces; (2) the embedded PZT sensors near the bearing plate yielded higher sensitivity to prestress forces; (3) the empirical equations of the measured impedance signals with respect to the compressive stresses applied could be implemented to predict compressive stresses in the PSC anchorage; and (4) the smart rebar was more sensitive for local monitoring as compared to the smart aggregate.As a remaining issue, the optimal design parameters of embeddable sensor devices should be achieved to detect relatively small changes of long-term prestress loss induced by concrete creep/shrinkage and steel strands relaxation. Additionally, the effect of temperature variation should be surveyed for the smart rebar–aggregate sensors.


This study was aimed at defining the demographic, social, clinical, and laboratory factors that affect antibiotic prescriptions in children discharged from the emergency department. We performed a retrospective observational study of children aged younger than 18 years discharged from a pediatric university hospital between Jan. 1, 2015 and Dec. 31, 2020. We determined the proportion and type of antibiotic prescription according to demographic, social, clinical, laboratory, and imaging data, as well as doctor’s expertise. Fifty-one thousand six hundred thirty-three children were included, and 13,167 (25.5%) received an antibiotic prescription. Amoxicilline/clavulanate (Am/Cl) was the most prescribed antibiotic . Factors independently associated with an antibiotic prescription were older age (OR = 1.62 [1.53–1.73] for age 2–5 years, OR = 1.77 [1.64–1.91] for age 6–10 years, OR = 1.36 [1.25–1.49] for age 11–18 years, Conclusions: Overprescription of antibiotics, including Am/Cl, is relevant in pediatric emergency departments. Factors associated with overprescription are not limited to the clinical characteristics of the treated patients. These findings highlight the need for a new and comprehensive approach to ensure successful antibiotic stewardship initiatives in the emergency departments.    The online version contains supplementary material available at 10.1007/s00431-022-04386-y. Antibiotic resistance is one of the biggest threats to global health, and, unfortunately, it is rising globally and is now at dangerous high levels. New resistance mechanisms are emerging and spreading, and a growing list of diseases, including the major global killers—such as pneumonia, tuberculosis, and foodborne diseases—are becoming more and more difficult to treat . Recent Tackling antibiotic resistance is challenging since it requires integrated and multifactorial interventions targeted at all levels of society, from the daily habits of individuals to the healthcare industry, from policymakers to health professionals. In this complex scenario, appropriate antibiotic prescription practices play an obvious role and, at least theoretically, represent the easiest area of intervention. Understanding reasons behind physicians’ choices to prescribe antibiotics and how improving these practices represent a priority for modern medicine.In this context, children are a well-known and recognized target of antibiotic prescriptions , making Most of these studies were single center and included small numbers , and theFor these reasons, to fill the current knowledge gap, we designed this study aimed to comprehensively assess the factors associated with the antibiotic prescriptions in children discharged from the ED of a University Hospital, including several variables not yet assessed in current literature.This is a retrospective cross-sectional observational study conducted in the pediatric ED of the Fondazione Policlinico Universitario A. Gemelli IRCCS of Rome, Italy, which is a third-level ED and a regional trauma center. Our ED held a dedicated pediatric section, with a senior pediatrician present 24/day, in addition to one or more residents (pediatrician in training). The final disposition, the medical responsibility, and signature on the discharge letters are always made by the senior pediatrician.We included in the analysis all children aged ≤ 17 years who accessed the pediatric ED between Jan. 1, 2015 and Dec 31, 2020, and were discharged with suspect or confirmed infectious disease.We excluded from the analysis the patients not discharged directly from the ED . We also excluded patients assessed for any type of trauma, or post-surgery complications, since they may have received antibiotic prescriptions for prophylaxis. Moreover, since the study period has partial overlap with the COVID-19 pandemic, we excluded children with SAR-CoV-2 infection that, particularly during the first months of uncertainties, may have influenced the doctor’s choice of prescribing antibiotics. Since the beginning of the pandemic, children with signs or symptoms suggestive of an infectious disease were tested with PCR test on nasopharyngeal swab, and children with a positive result were excluded. Finally, we excluded patients with inconsistent or incomplete medical records.This study was conducted according to the principles expressed in the declaration of Helsinki and its later amendments and was approved by the local Institutional Review Board .Data were retrospectively collected from the computerized clinical records of our institution, and included in an electronic database.Characteristics of ED access, including season, day, and daytime of the ED access; self-reported or transferred by the emergency medical system; triage code assigned.The expertise of the treating pediatrician (cathegorized as > 3 years or lower).Patients’ demographic, including age and sex.Reported symptoms, including cough, vomit, dyspnea, diarrhea, fever peak > 40 °C, myalgia/arthralgia, palpitations, and headacheClinical findings at ED evaluation, including fever > 37.5 °C, crepitation on auscultation, poor or mediocre general condition, peripheral cyanosis (including capillary refill > 2 s).Clinical history, including the presence of major inherited disease (any), history of cardiac disease, history of prematurity, history of asthma, intellectual disability, history of epilepsy.9 cell/L. A positive CRP was considered for CRP ≥ 50 mg/L. For CRP, we chose a 50 mg/dL cutoff since available literature describes it as the most realistic to discriminate bacterial and viral infections , and are compared at univariate analysis by Mann–Whitney 3/mm3, and WBC ≥ 103/mm3; the reference category for odds calculation was considered WBC not requested. For PCR, patients were divided into “PCR not requested,” PCR < 50 mg/dL, and PCR ≥ 50 mg/dL; the reference category for odds calculation was considered PCR not requested.Variables having a significant association with an antibiotic prescription at discharge from the ED were entered into a logistic regression model in order to identify independent predictors of prescription. Prior to being entered into the logistic models, for a better model fitting and odds estimation, we transformed the continuous variables age, WBC, and PCR into categorical variables. For age, patients were divided into age < 1-year-old, age 2–5 years, age 6–10 years, and age 11–18 years; the reference category for odds calculation was the group age < 1 year. For WBC, patients were divided into “WBC not requested,” WBC < 10To avoid model redundancy or overfitting, single items composing derived variables were excluded from multivariate analysis,The univariate and multivariate analysis was performed considering the whole population at the same time, and the single age group separately. Similarly, multiple models were obtained for “general antibiotic prescription,” Am/Cl prescription, and single amoxicillin prescription.p ≤ 0.05. Data were analyzed by SPSS v25® .Multivariate association of factors with the study endpoints was expressed as odds ratio (OR) [95% confidence interval]. We considered significant a two-sided In the study period, 112,516 patients ≤ 17 years were evaluated in the pediatric ED of our institution. Considering the inclusion criteria, 51,633 children discharged with suspect or confirmed infective diagnosis were included in the analyses (Table Their median age was 3 years IQR 1–6), and 28,384 (55%) were males. Two thousand eight hundred eighty-one (5.8%) children were triaged as emergent or urgent cases  received an antibiotic prescription, with Am/Cl being the most prescribed antibiotic . Further details on the study population are reported in Table p < 0.001), winter season (p < 0.001), being assessed by a more experienced pediatrician (p < 0.001), having inherited (p < 0.001), or cardiac diseases (p = 0.026) were the demographic/anamnestic factors associated with a higher antibiotic prescription. Other clinical and laboratory factors associated or not to antibiotic prescriptions on univariate analyses are detailed on Table Table When entered into a multivariate logistic regression model, several factors emerged as independent predictors of antibiotic prescription Table .p < 0.001), a poor or mediocre general condition , and positive thorax auscultation .Clinical findings and symptoms independently associated with an antibiotic prescription were a reported fever peak > 40 °C (OR 1.37), the presence of fever > 37.5 °C at the physical examination  compared to less experienced colleagues. Other factors are reported in Table A PCR ≥ 50 mg/dL, a positive urine analysis, and a positive CXR were independently associated with an antibiotic prescription at ED discharge. Conversely, the sole prescription of these examinations in the ED was associated with a higher odds of antibiotic prescription Table , compareMultivariate analyses of factors influencing the antibiotic prescription for each age group are presented in Supplementary Table The antibiotics prescribed according to the discharge diagnoses are represented in Fig. In each age group, Am/Cl remained largely the most prescribed antibiotic, although use of macrolides and other drugs like fluoroquinolones was higher in older age groups.Table Compared to patients < 1 year, the older age groups had significantly higher odds of Am/Cl prescription, being the overall OR almost doubled in the 11–17-year group.The access on weekends, on nightshifts, the transportation by EMS, and higher pediatrician expertise were all associated with higher odds of Am/Cl prescription.The clinical findings independently associated with Am/Cl prescription were the presence of cough, a fever peak > 40 °C, a positive CRX, the presence of headache, and a history of cardiac disease. As expected, Am/Cl had a higher odds of prescription (compared to other classes of antibiotics) in cutaneous infections.The multivariate analyses of factor influencing the prescription of amoxicillin, the antibiotic expected to be theoretically more prescribed, is presented in the Supplementary Table In this study, we provide a comprehensive overview of prescriptions and their determinants in a large sample of children assessed in the pediatric ED. To our knowledge, this is the largest study that also includes a comprehensive list of non-clinical variables that may affect antibiotic prescription, adding to patients’ signs and symptoms, and to a wide range of diagnostic categories, the daytime of presentation, the seasonality, the physicians’ expertise, and the physicians’ attitude for diagnostic request.Overall, we found that a large proportion of children, as high as one in four children, were discharged from the ED with antibiotics. Among the antibiotic classes, Am/Cl was the most prescribed, representing more than half of all prescriptions. These data are in line with previous studies from Europe and the USA , 11–13, Contrarily to adults, the presence of pre-existing comorbidities did not seem to significantly affect antibiotic prescriptions in this pediatric cohort. However, those with inherited and cardiac diseases could have a higher odds of receiving antibiotics, and other fragile children such as ex-premature did not have this risk. However, it is indeed possible that these children were more frequently admitted to the ward rather than discharged, thus limiting the analysis for this group of children. This is confirmed by a multinational European study showing that children with inherited comorbidities are more frequently admitted by pediatric EDs .Distinguishing bacterial from viral infections is challenging, particularly in the EDs, and the newer and promising transcriptomic tests are not available in routine settings. Moreover, the traditional dichotomous distinction of viral and bacterial has been recently challenged by the PERFORM consortium, which proposed a novel framework for phenotyping children with suspected or confirmed bacterial/viral infections . HoweverClinical signs and symptoms can, indeed, help clinicians in treatment decisions. We found that some symptoms that may be more suggestive of viral infections, such as myalgias/arthralgias, gastrointestinal symptoms, and dyspnea , were associated with a lower likelihood of receiving antibiotics. However, the relevant number of children with signs or symptoms and laboratory investigations suggestive of viral infection that received antibiotics suggests a wide variability among physicians and the possibility that other factors may affect the prescription decision.For these reasons, we also investigated non-clinical factors, such as the timing of the ED access and the day of the week (weekend vs working days). In our country, general practitioners are not available during the night and the weekends, nor routine laboratories. These factors can affect access to routine outpatient diagnostics, consultations, or the possibility of discharging ED children to “safety nets,” and therefore, they may have theoretically affected the pattern of ED access and consequently the prescription rates. To our knowledge, these non-clinical elements have never been widely including in previous studies. Interestingly, while we found no differences in the prescriptions for children evaluated during weekends, those assessed during night shifts had a lower odd of antibiotic prescription. Given the large samples, these data suggest that these factors should reasonably do not affect the prescription decisions, although a much smaller study from Malaysia assessing 500 children revealed a higher prescription rate during weekends .Among factors not related to the patients’ conditions, the expertise of the treating physician could indeed affect the prescription likelihood. Interestingly, and contrary to common sense, physicians with a longer experience had a higher odds of prescribing antibiotics, including Am/Cl. This finding is interesting and may suggest that younger doctors may have more attention toward antimicrobial stewardship programs, whose importance has received more attention during recent years. For example, the WHO recently implemented the AWaRe  classification to help allocate the proper choices of antibiotics, which may be more familiar to doctors closer to training periods , 24. Thep 0.001), although in multivariate analyses, differences were statistically not significant. However, when the analyses were performed for age groups, those 2–5 years old had significantly higher probability to receive antibiotics in winter. Interestingly, this is the age group that is more affected by viral infections during school age. However, since climate change mainly refer to shifts of mean temperatures during seasons [Another important non-clinical factor is the contribution of temperature, and therefore seasons, on human health. There is increasing recognition that global climate change can directly affect health, and therefore, we included seasons of evaluation as a potential variable affecting probability of antibiotic prescription . Overall seasons , a next The high rates of antibiotic prescriptions and the variability in practice  may reflTo further highlight the uncertainties behind the decision to prescribe antibiotics, a recent randomized clinical trial found the unexpected results that the use of rapid respiratory pathogen testing in the ED for children with influenza-like illness did not decrease antibiotic prescribing . AlthougOur study, being the largest one that included several variables in terms of demographic and clinical data, investigations, daytime variability, doctors’ experience, and decisions to perform diagnostics, provides strong confirmation of the complexity behind the decisions to prescribe or not antibiotics in the pediatric ED. Our data are in line with the recent PERFORM positions , strengtOur study has some limitations to address. The retrospective nature of the study is an intrinsic limitation, although our electronic system allowed us to include and analyze a large number of detailed variables. Second, in our institution, the use of procalcitonin has been introduced late in 2020, and its use is not yet considered routine in our internal guidelines. Third, we have not been able to collect data on the length of antibiotic therapies prescribed. Finally, we did not include the immunizations performed by the patient at the moment of admission. Theoretically, the knowledge of immunization status may lower the risk of serious infection on discharge and influence the antibiotic prescription. However, since the overall coverage in Italian children is above 90% in our region for most immunizations , this daIn conclusions, our analysis confirmed that the children discharged from the pediatric ED receive a high rate of antibiotic prescriptions, most of the time with Am/Cl. The inclusion of several non-clinical variables allowed us to explore the complexity of the reasons behind the pediatricians’ decision of prescribing antibiotics, highlighting the importance of developing a new and comprehensive approach to improve antibiotic use in the ED. This approach should include the simultaneous participation of all actors involved in this process: doctors, parents, children, antimicrobial stewardship programs, diagnostics, and a new categorization of viral and bacterial infections.Supplementary file1 (DOCX 1014 KB)Below is the link to the electronic supplementary material.