Influence of counterbalance valve parameters on stability of the crane lifting system
In this paper, a model of the large crane lifting system has been developed in the AMESim environment. The comparison between the simulation results and the experimental data shows good agreement in both time and frequency domains, indicating the correctness of the model. Furthermore, the causes of pressure pulsations of the lifting system are described by means of dynamic simulation and experimental research. The analysis result indicates that the pressure pulsation of the lifting system is closely related to dynamic characteristic of the counterbalance valve, and stability of the system can be improved by means of the flow area of counterbalance valve with linear small gradient.
Research on pipeline pressure shock in valve control hydraulic positioning system
In order to research on pipeline pressure shock in valve control hydraulic system,a mathematical model of valve control hydraulic system was established,which included the servo valves,hydraulic cylinder,pumps and spillover valve,while the effect of the pipeline to dynamic performance of the system was took into account.With Simulink software package of Matlab dynamic simulation tools,a simulation analysis was made for step response of valve control hydraulic system to study the phenomenon of producing the hydraulic shocks.Simulation results show that the mathematical model reflected the real work of the system.
Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.