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Electrospun nanofibers is a promising and versatile avenue for building controlled drug release system because of the facile fabrication and the broad range of polymer materials. This research systematically studied the morphological effect of thermosensitive electrospun nanofibers, including porous and coaxial structures, on controllable drug release. Three types of drugs, nicotinamide, paracetamol, and ibuprofen, with different hydrophilicity were applied in this study. The data of drug release were all fitted to the first-order kinetic model regardless of the drug properties, and the release rates paralleled with their hydrophilicity. Sol-gel phase transition of the thermosensitive poly(

Self-contained soft electrofluidic actuators display excellent performance in portability, rapid response, and actuation., Soft robotics revolutionized human-robot interactions, yet there exist persistent challenges for developing high-performance soft actuators that are powerful, rapid, controllable, safe, and portable. Here, we introduce a class of self-contained soft electrofluidic actuators (SEFAs), which can directly convert electrical energy into the mechanical energy of the actuators through electrically responsive fluids that drive the outside elastomer deformation. The use of special dielectric liquid enhances fluid flow capabilities, improving the actuation performance of the SEFAs. SEFAs are easily manufactured by using widely available materials and common fabrication techniques, and display excellent comprehensive performances in portability, controllability, rapid response, versatility, safety, and actuation. An artificial muscle stretching a joint and a soft bionic ray swimming in a tank demonstrate their effective performance. Hence, SEFAs offer a platform for developing soft actuators with potential applications in wearable assistant devices and soft robots.

There is likely to be a demand to run high-speed trains in extreme cold weather conditions in the near future; therefore, it is important to study the change in the characteristics of the materials and components in an extreme cold environment and their effects on the vehicle system dynamics. Experimental research into the low temperature characteristics of a pantograph hydraulic damper was carried out in this study. The results show that low temperature causes an increase in damping forces, and when the temperature is above the boundary temperature range, most indices of the damping capability increase with the decrease of temperature; when the temperature is below the boundary temperature range, most indices decrease with the decrease of temperature. Key parameters are identified to obtain the theoretical description of low-temperature damping characteristics using a simplified-parametric damper model and the experimental data. A mathematical model of the pantograph–catenary system incorporating the pantograph damper model is then established to calculate the effect of the damper performance on the pantograph dynamics low temperatures. Simulation results show that the lowering performance of the pantograph deteriorates noticeably due to the unstable low-temperature damping characteristics, but the deterioration of the raising performance and contact quality of the pantograph due to the low-temperature characteristics of the damper are less obvious. The results obtained in this study are valuable for understanding the low-temperature characteristics of a hydraulic damper, and instructive in the optimal specification of the pantograph damper for high-speed trains running in cold weather conditions.

A new simplified parametric model, which is more suitable for pantograph–catenary dynamics simulation, is proposed to describe the nonlinear displacement-dependent damping characteristics of a pantograph hydraulic damper and validated by the experimental results in this study. Then, a full mathematical model of the pantograph–catenary system, which incorporates the new damper model, is established to simulate the effect of the damping characteristics on the pantograph dynamics. The simulation results show that large $$F_{\mathrm{const}}$$ (saturation damping force of the damper during compression) and $$C_{\mathrm{0}}$$ (initial damping coefficient of the damper during extension) in the pantograph damper model can improve both the raising performance and contact quality of the pantograph, whereas a large $$C_{\mathrm{0}}$$ has no obvious effect on the lowering time of the pantograph; the nonlinear displacement-dependent damping characteristics described by the second item in the new damper model have dominating effects on the total lowering time, maximum acceleration and maximum impact acceleration of the pantograph. Thus, within the constraint of total lowering time, increasing the nonlinear displacement-dependent damping coefficient of the damper will improve the lowering performance of the pantograph and reduce excessive impact between the pantograph and its base frame. In addition, damping performance of the new damper model would vary with the vehicle speeds, when operating beyond the nominal-speed range of the vehicle, the damping performance would deteriorate obviously. The proposed concise pantograph hydraulic damper model appears to be more adaptive to working conditions of the pantograph, and more complete and accurate than the previous single-parameter linear model, so it is more useful in the context of pantograph–catenary dynamics simulation and further parameter optimizations. The obtained simulation results are also valuable and instructive for further optimal specification of railway pantograph hydraulic dampers.

In order to collect energy from human activities, piezoelectric energy harvesters should have a flexible structure, low resonant frequency and wide frequency bandwidth. In this paper, the fabrication and characterization of a metal-based Pb(Zr,Ti)O3 (PZT) bimorph thick film energy harvester. PZT thick films were deposited on cantilever-shaped titanium (Ti) substrate via a dip-coating process. The electrical properties of the PZT films sintered at different temperatures were investigated. The nonlinear piezoelectric energy harvester has the following advantages: it is suitable for low frequency, weak vibration, and wide frequency bandwidth. The maximum open-circuit voltage of the piezoelectric energy harvester is 1.6 V and the output power is 0.85 μW with 150 kΩ load resistance at low resonant frequency of 17.6 Hz when the input vibration acceleration was 0.12 g. In addition, the frequency bandwidth is broadened from 0 to 8.4 Hz as the input acceleration increases from 0.05 g to 0.12 g. Keywords: Energy harvesting, PZT, Sintering temperature, Nonlinear vibration

Recent advances in soft materials enable robots to possess safer human-machine interaction ways and adaptive motions, yet there remain substantial challenges to develop universal driving power sources that can achieve performance trade-offs between actuation, speed, portability, and reliability in untethered applications. Here, we introduce a class of fully soft electronic pumps that utilize electrical energy to pump liquid through electrons and ions migration mechanism. Soft pumps combine good portability with excellent actuation performances. We develop special functional liquids that merge unique properties of electrically actuation and self-healing function, providing a direction for self-healing fluid power systems. Appearances and pumpabilities of soft pumps could be customized to meet personalized needs of diverse robots. Combined with a homemade miniature high-voltage power converter, two different soft pumps are implanted into robotic fish and vehicle to achieve their untethered motions, illustrating broad potential of soft pumps as universal power sources in untethered soft robotics., Utilizing soft pumps in soft robotics is an attractive approach to endow untethered soft robots with muscle-like actuation. Here, the authors report bio-inspired soft electronic pumps as driving power sources to drive actuation and self-healing in untethered soft robotics.

Based on the data analysis and collection of optical thermal power station, this paper uses big data and machine learning method to mine the knowledge and rules contained in various data to guide the operation. Combined with various data sources, the model is established, and the system optimization and operation reference research are carried out.

Equivalent static wind loads (ESWLs) on cooling towers derived even by the refined multiple-mode dynamic algorithm such as the complete quadratic combination theory usually shows quite different types for various design targets. So, it is evitable to bring complex and burdensome calculation for structural design. To this problem, the improved multi-objectives ESWLs method was proposed by combining the wind vibration characteristics of large cooling towers itself. Through several numerical examples, the multi-objective ESWLs distribution characteristics were discussed, and its rationality of application in the cooling towers was also validated.

This investigation aims at typical adverse wind load patterns under tower group interference and overall structure optimization of large cooling towers considering multiple geometric parameters, focusing on potential unfavorable load patterns. Wind tunnel tests were performed on typical six-tower groups with various central distances, incoming flow directions and arrangement types, and external wind pressures were measured under interference conditions. Adverse wind load patterns are summarized with the help of interference criteria for three parameters: aerodynamic load, structure response and weighted internal force combination. Furthermore, overall structure optimization is achieved through the hybrid of grid search and gradient descent method, taking into account various possible wind loading distributions. Total 13 geometric parameters are adjusted to seek an optimized design that satisfy the requirement of structure strength, stability and economy under a particular wind load pattern. Crossover checks are then introduced to select a final optimized design scheme that is universally applicable to different adverse wind load patterns. The optimization procedure proposed in this study shows that adverse wind load patterns of grouped towers has distinct features comparing with wind load codes. It is necessary to consider the influence of multiple typical adverse wind load patterns for structural design, and the final optimization scheme should be determined through crossover checks to guarantee structure safety, stability and economy of cooling towers.

Recent years, China is facing an increasingly severe obesity situation. With the further improvement of the life quality of the youth in China, fitness consciousness has gradually been deeply rooted in people’s heart, thereby, people’s demand of fitness is at a status of steep rise. Mobile fitness apps then attracted a large number of young people’s eyes. Nevertheless, the profit model of this kind of apps is still at a stage of diversified development, and the model is relatively blurry and chaotic. The problem of profit model is one of the significant reasons lead to the slow development of mobile fitness industry. Through comparing these three mobile fitness apps and make an analysis about the current situation of the profit model of mobile fitness apps in our country and then find out the deficiency of existing profit models and explore the potential profit models in the future.

Interference factors (IFs) are commonly used to envelope various dynamic loading distributions due to wind-induced interference effects. However, those parameters are discrete in values for different evaluation criteria. Aiming at unifying cognitive distinction for series equivalent criteria about IFs, cooling tower groups with typical 6-towers arrangement were selected to conduct case studies by wind tunnel tests and numerical calculation, investigating interference effects among classical rectangular and rhombic arrangement. 25 kinds of IFs' definitions were totally compared basing on three index levels, namely loading, internal force and reinforcement ratio. Wind pressure measurements about 1:200 reduced-scale model were carried out in TJ-3 wind tunnel, corresponding 3D dynamic or static calculation were finished to analyse IFs. Main conclusions can be summarized, such as there are great distinctions about IFs’ value for different criteria, whose maximum may reach 42%, IFs’ variance coefficients in loading level would be the largest, and those in reinforcement level are the smallest, etc.

A new phase separation system, aqueous multiphase system (MuPSs, ranging from two to four phases), containing surfactants and polymer (SDS/DTAB/PEG/NaBr/H 2 O) was designed and the complicated four-phase systems were investigated systematically. To interpret the phase separation phenomena, the phase composition, phase density, phase volume ratio between the studied phase and the whole system as well as the particle size and zeta potential of aggregates in each phases were investigated. The results have shown that the multiphase system contains liquid crystal phase, which may imply a close relationship between MuPSs and liquid crystal. At the same time, it seems there is a direct relationship between zeta potential of the existed phase and the appearance of new phase. Phase composition analysis results illustrate that the rich component for the three phases from top to the third one are PEG, DTAB, and SDS, respectively. However, the bottom phase is almost dilute brine. Furthermore, the differential scanning calorimetry experiments prove that the micro-complexity of aggregates in different phases is different from each other. The studied MuPSs are very stable but temperature sensitive; the coexisted phases have different extraction power to xylenol orange because of the variation of composition. The higher stability of MuPSs makes it useful when the storage and long-term stability of the separation media are important. The work not only provides theoretical guidance for the development of efficient extraction and separation technology but also provides new opportunities for the development of aqueous multiphase systems.

The effect of ionic liquids on aqueous multi-phase system of DTAB/SDS/PEG/NaBr/H2O has been studied by displacing the inorganic salt NaBr partially or completely with short chain ionic liquids (1-ethyl-3-methyl imidazolebromine [C2mim]Br, 1-butyl-3-methyl imidazole bromine [C4mim]Br) and the cationic surfactant DTAB with long chain ionic liquid (dodecyl-3-methyl imidazole bromine [C12mim]Br). The results show that the formation of aqueous four-phase system of DTAB/SDS/PEG/NaBr/H2O is the result of the coexistence of "polymer ATPS" and "surfactant ATPS". The stonger hydrophilic nature of short chain ionic liquids ([C2mim]Br, [C4mim]Br) endows their stonger salting out ability, which ensured the existence of "polymer ATPS" in aqueous four-phase system. The interaction between ionic liquids and polymer and the effect of ionic liquids on the interaction among surfactants can not be neglected because all of them have prominent influence on the phase behavior of mixed system and the properties of the coexisted multi-phase. The long chain ionic liquid [C12mim]Br affects the properties of "surfactant ATPS" by hydrophobic effect and act as the role of surfactant. However, the difference of molecular structure between [C12mim]Br and DTAB leads to the redistribution of surfactant molecules in two phases of "surfactant ATPS". Correspondingly, the volumes and extraction ability of the two phases are changed. Obviously, aqueous multiphase system with specific properties could be obtained by tailor the alkyl chain length and adjust the content of ionic liquids in mixed systems.