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To address the problems of uneven mass distribution and hydrothermal management imbalance in flow fields, this study proposes a snowflake slope composite flow field (SSCFF). A three-dimensional multiphase computational fluid dynamics (CFD) model was developed to analyze the differences between the SSCFF and traditional flow fields, and to investigate the effects of gas inlet and outlet configurations, height ratios (L d / D ), and the number of main channels (N) on the performance. The study shows that the SSCFF excels in gas distribution and temperature control, with a maximum power density 35.5% higher than the honeycomb structure. The diagonal inlet and outlet configuration effectively reduces the risk of local hotspots and flooding. With L d / D of 0.9, the uniformity of oxygen distribution improves significantly and the current density reaches 1.168 A cm−2. Additionally, with 6 main channels, the proton exchange membrane (PEM) achieves a higher hydration level, which boosts catalytic activity and working efficiency. [Display omitted] • The SSCFF enhances net power density by 35% than a honeycomb flow field. • The diagonal inlet and outlet configuration reduces localized concentration loss. • L d / D of 0.9 balances the lateral and longitudinal flow of gases within the channels. • N of 6 improves the hydration level of PEM with a performance of 1.168 A cm−2. [ABSTRACT FROM AUTHOR]

The output performance of piezoelectric pumps is not only affected by the structural design but is also related to the drive signal. To study the effect of different drive signals on the output performance of piezoelectric pumps, this paper takes dual-chamber serial piezoelectric pumps as the investigation object, theoretically deduces the effective value of the drive signal and the output performance of the piezoelectric pump, and tests the displacement of piezoelectric vibrator center, the output performance of the piezoelectric pump, and the operating noise within the range of 0–500 Hz, respectively, driven by square waves, sine waves, and triangular waves (the peak-to-peak values of which are all 300 V). The results show that at low frequencies, the piezoelectric vibrator's center displacement curve matches the drive signal, which is sinusoidal and decreases with frequency. Under the square drive, the piezoelectric pump has the best performance, with a flow of 147.199 mL/min and pressure of 14.42 kPa, but the noise is also the highest. The output performance of the sine wave is better than that of the triangular wave, and the flow rate of the three signals shows a trend of first increasing and then decreasing. [ABSTRACT FROM AUTHOR]

In order to improve the output performance of multi-chamber piezoelectric pumps, this paper proposes a novel design for a four-chamber series–parallel piezoelectric pump, based on the characteristics that the parallel chamber structure significantly increases the output flow rate, and the series chamber structure effectively improves the output pressure. The theoretical output flow rate and pressure of the four-chamber series–parallel piezoelectric pump were calculated, and a prototype was fabricated. Tests were conducted to compare the liquid transport performance of piezoelectric pumps with three different structures: series, parallel, and series–parallel. The results show that, when transporting liquid, the output flow rate of the four-chamber series–parallel structure increased by up to 13.3% compared to the four-chamber series structure, reaching a maximum of 767 mL/min. Additionally, the maximum output pressure of the series–parallel structure increased by 43.4% compared to the four-chamber parallel structure, reaching 42.3 kPa. The four-chamber series–parallel design combines the advantages of both series and parallel configurations, improving the output performance of the piezoelectric pump and providing a reference for the structural design of multi-chamber piezoelectric pumps. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) can collect and convert random mechanical energy into electric energy, with remarkable advantages including broadly available materials, straightforward preparation, and multiple applications. Over the years, researchers have made substantial advancements in the theoretical and practical aspects of TENG. Nevertheless, the pivotal challenge in realizing full applications of TENG lies in ensuring that the generated output meets the specific application requirements. Consequently, substantial research is dedicated to exploring methods and mechanisms for enhancing the output performance of TENG devices. This review aims to comprehensively examine the influencing factors and corresponding improvement strategies of the output performance based on the contact electrification mechanism and operational principles that underlie TENG technology. This review primarily delves into five key areas of improvement: materials selection, surface modification, component adjustments, structural optimization, and electrode enhancements. These aspects are crucial in tailoring TENG devices to meet the desired performance metrics for various applications. [ABSTRACT FROM AUTHOR]

Abstract In the production of oil and natural gas, excessive clearance volume is an important factor affecting the normal operation of oil-gas multiphase pump. Currently, little research has been conducted on the effect of clearance volume on the output characteristics of multiphase pump at home and abroad, leading to extremely low efficiency in the field application of multiphase pump. Therefore, this study conducted numerical calculations on the internal flow characteristics and output performance of multiphase pump under different clearance volumes using FLUENT software. Results show that pressure and fluid velocity gradually decrease as the clearance volume increases. Simultaneously, the number and intensity of vortex flow gradually increase, media pressurization speed becomes slower, and the lag angle of the discharge valve opening becomes larger. Moreover, under conditions with a higher gas volume fraction, multiphase pump with larger clearance volumes experiences gas locking. Furthermore, this study provides a theoretical basis for the reasonable design of clearance volume for multiphase pump by drawing a relationship curve between gas volume fraction and clearance volume. These research findings can provide theoretical support for the performance optimization and design improvement of multiphase pumps.

Graphene betavoltaic isotope battery is one of the applications of graphene in semiconductor and microelectronics. Among them，the modification of graphene is an important research content to improve the application of graphene in these fields. In this study，we compared the effect of nitric acid doping and electron beam irradiation on the output performance of graphene betavoltaic isotope batteries. At the same time，the mechanism of two different methods on the modification of graphene materials was studied by means of light microscope，XPS and Raman spectroscopy. The results show that the nitric acid doping was a surface charge transfer process，which can not change the sp2 hybrid carbon atoms in graphene into sp3 hybrid，but can improve the short-circuit current of graphene betavoltaic isotope batteries. While the electron beam irradiation of graphene will introduce defects in graphene，and transform sp2 hybrid carbon atoms in graphene into sp3 hybrids，thus opening the band gap of graphene and improving the open circuit voltage and filling factor of graphene betavoltaic isotope batteries. The above results can provide experimental theoretical basis for the design and preparation of graphene betavoltaic isotope batteries，and provide reference for further improving the performance of graphene betavoltaic isotope batteries.

In order to address Solid oxide fuel cells(SOFC) the issues of uneven gas distribution and low fuel utilization rate in conventional straight-channel. In this research, a connected cable-type channel with enhanced connectivity and broader radiation coverage was developed. The research revealed that in a singular flow channel scenario, the distribution of oxygen on the electrode within the connected cable-type channel exhibited greater uniformity compared to the conventional straight-channel design. The gas utilization rate is increased by 2.38% compared with the conventional straight-channel, and the output power density is increased by 8.55%. In the flow field, it is observed that the gas distribution on the cathode side of connected cable-type channel is significantly superior to that of the conventional straight-channel. In the case of a parallel flow field, the output power of the connected cable channel increases by 8.39% compared to the conventional straight channel, while the serpentine channel shows an increase of 11.65% in output power. Then, the impact of the flow field combination on the flow field was investigated. It was discovered that the output power of the cell could reach up to 5158.17 W/m2 when the serpentine-parallel staggered flow field distribution structure was utilized. This output was 11.33% higher than that of the parallel flow field. • A new type of connected cable-type channel was designed to increase the gas diffusion range at the electrode. • Expand the new flow channel into the flow field for a comprehensive study. • Find the optimal geometric arrangement and further optimize the new channel. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Isotopes is the property of Journal of Isotopes Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biodegradable polymers (BPs)‐based triboelectric nanogenerators (TENGs) have advantages, including biocompatibility and biodegradability. However, biodegradable TENGs (BD‐TENGs) possess relatively low output performance, limiting their application due to the small differences in triboelectric polarities for most BPs. Molecular doping is a simple and effective method in altering the triboelectric polarity of triboelectric materials and improving the output performance of BD‐TENGs. However, there is a lack of laws and mechanism about the differences in triboelectric polarities of different doped molecules, especially of molecules with biodegradability and biocompatibility. Here, kinds of doping molecules are selected for doping in tribopositive and tribonegative materials, respectively, and their triboelectric polarities and related laws are researched. In particular, the output performance of BD‐TENG is improved several times by doping small amounts of poly (propylene glycol) (PPG) and ethyl cellulose (EC), with enhanced resolution in abnormal respiratory signal monitoring. This work not only provides theoretical guidance for the selection of triboelectric molecules but also conducts in‐depth research in molecular‐level triboelectric mechanisms. [ABSTRACT FROM AUTHOR]

Wearable thermoelectric generators have great potential to provide power for smart electronic wearable devices and miniature sensors by harnessing the temperature difference between the human body and the environment. However, the Thomson effect, the Joule effect, and heat conduction can cause a decrease in the temperature difference across the thermoelectric generator during operation. In this paper, phase change materials (PCMs) were employed as the heat sink for the thermoelectric generator, and the COMSOL software 6.1 was utilized to simulate and optimize the power generation processes within the heat sink. The results indicated that with a PCM height of 40 mm, phase transition temperature of 293 K, latent heat of 200 kJ/kg, phase transition temperature interval of 5 K, thermal conductivity of 50 W/(m·K), isobaric heat capacity of 2000 J/(Kg·K), density of 1000 kg/m3, and convective heat transfer coefficient of 10 W/(m·K), the device can maintain a temperature difference of 18–10 K for 1930 s when the thermoelectric leg height is 1.6 mm, and 3760 s when the thermoelectric leg height is 2.7 mm. These results demonstrate the correlation between the device's output performance and the dimensions and performance parameters of the PCM heat sink, thereby validating the feasibility of employing the PCM heat sink and the necessity for systematic investigations. [ABSTRACT FROM AUTHOR]

In order to reduce the permanent magnet synchronous motor cogging torque and improve the motor output performance, a method of motor stator slot offset was proposed with the example of 3-phase 8-pole 36-slot built-in combined permanent magnet synchronous motor. Firstly, a mathematical model of motor stator slot offset was established by theoretically deriving the stator tooth air gap permeability function. Secondly, the effects of peak cogging torque, output torque and torque pulsation at different offset angles under different numbers of stator slot offsets were analyzed, and adaptive genetic algorithms were used to determine the target values under the offset angles for the number of stator slot offsets. Finally, a trial prototype was produced and the experiment was conducted. The results show that the peak cogging torque of the optimized motor is reduced by 49.56%, the torque pulsation is reduced by 39.2%, the average output torque is appropriately improved, and the air-gap magnetic density harmonics are appropriately reduced; the average output torque increases and the motor output performance is improved. The proposed stator slot offset structure and multi-objective joint simulation method are rational and effective, which can provide some reference for cogging torque optimization and output performance improvement of the same type of motors.

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Polyvinylidene fluoride/graphene oxide (PVDF/GO) composite nanofibers were fabricated by electrospinning technology, to enhance the output performance of triboelectric nanogenerators (TENG) based on PVDF. These nanofibers were assembled into vertically contact-separate TENG to investigate the influence of GO mass fraction on the output performance of TENG. By utilizing the COMSOL software, the output performance of the TENG was simulated and analyzed, and the variations of electric potential and electric energy density at different electrode distances were observed. This study provides theoretical support for the working principle of TENG. Moreover, the morphology and structure of the PVDF/GO composite nanofibers were characterized using scanning electron microscopy, while the output performance of the TENG based on PVDF/GO composite nanofibers was characterized using a digital oscilloscope. The results indicate that the TENG based on PVDF/GO composite nanofibers exhibits excellent output efficiency when the GO mass fraction is 0.06%. The output voltage is approximately 350 V, and the short-circuit current is around 28 µA, and under impedance matching conditions, the maximum peak power is approximately 9.66 mW, with a power density of approximately 3.86 W/m². The TENG prepared by PVDF/GO composite nanofibers exhibits excellent output performance, capable of powering 120 LEDs, hereby demonstrating potential application prospects in the field of energy harvesting. [ABSTRACT FROM AUTHOR]

The article considers the situation with uniformity assurance in measuring the output performance of high-power lasers, describing works that report an increase in the measured laser power of up to hundreds of kilowatts. The studies were carried out at the All-Russian Research Institute for Optical and Physical Measurements. In order to establish a system of metrological support for measuring the output performance of high-power continuous lasers, it was necessary to create three measurement standards, including GET 28-2022 State Primary Standard of the unit of average laser power, and four measuring instruments operating within the spectral range of 1.07–10.6 µm and the power range of 1–500 kW. A dynamic method for measuring high-power laser radiation was developed and used for the first time. This ensured the certification of instruments by means of standard radiation having a power of below 100 kW. The obtained results led to a significant increase in the level of metrological support to process and special high-power laser equipment. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of rotary proton exchange membrane fuel cell (R-PEMFC) and its simulation model is established and verified based on experimental data. Then the effects of different rotational angular speeds (RASs) on reactant flow characteristics and electrochemical reactions are investigated. Also, the key quantitative indexes, such as average value, uniformity index and effective mass transfer coefficient (EMTC) are adopted, while combining the polarization curve and net power to estimate the comprehensive R-PEMFC performance. The results indicate that the R-PEMFC effectively ameliorates uneven distribution and improves the transmission capability and output performance. Compared with the static state (0 rpm), the EMTC and maximum power density are enhanced by 65.86 % and 8.51 % respectively at the RAS of 1080 rpm, and the net power density can reach 5316 W·m−2. • A novel rotary proton exchange membrane fuel cell is first proposed and designed. • Effects of rotational angular speed on the R-PEMFC performance are investigated. • Key quantitative indexes are adopted to evaluate the comprehensive performance. • Compare static scheme effective mass transfer coefficient raise 65.86 % at 1080 rpm. • Maximum net power density of the newly designed R-PEMFC can reach 5316 W m−2. [ABSTRACT FROM AUTHOR]

Based on the inverse piezoelectric effect and other characteristics of piezoelectric ceramics, a new type of piezoelectric variable friction damper is developed, and the output performance test of piezoelectric ceramic actuator and piezoelectric variable friction damper is carried out, and the parametric mechanical model of the damper is established by using Simulink to carry out numerical simulation, and compared and analyzed with the test results. The results of the study show that the simulation and the test present a good regular agreement. With the increment of loading voltage, the displacement deformation and zero-displacement thrust of piezoelectric ceramic actuator are approximately linear with the loading voltage; when the loading voltage is increased by 15V every time, the test value of the output damping force of the damper increases by 259.66N on average step by step, and the simulated value increases by 256.14N step by step, and the damping force has a linearly incremental relationship with the voltage and the slope of the linear increase is 16.434. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) and thermoelectric (TE) hybrid systems have the potential to increase solar energy utilization and possess broad development prospects. However, it is critical to select a suitable PV cell to couple with TE device and improve the efficiency of the photovoltaic–thermoelectric (PV-TE) hybrid system. This study used thermal interface materials (TIMs) with different thermal conductivities in triple-junction InGaP/GaAs/GeInG (tj-GaAs) PV-TE hybrid systems to reduce thermal contact resistance (TCR). The performance was investigated using a solar simulator with adjustable irradiation intensity and a liquid cooling device with controllable temperature. A comparative study has also been conducted with mono-crystalline (mc-Si) PV-TE system of the similar structure. The results indicated that the total output power of the direct contact PV-TE hybrid device and the optimized hybrid device using a thermal grease with a conductivity of 5.8 W m−1 K−1 could increase by 5.50% and 16.24%, respectively, compared with that of the pure PV. Moreover, lower cooling water temperatures have improved the performance of both PV cell and TE device. Results also indicated that the output power produced by the PV cell and TE device in the tj-GaAs PV-TE system are 537 mW and 0.76 mW higher than that produced by the PV cell and TE device in mc-Si silicon PV-TE system at 3.5 suns and 20 °C cooling water temperature, respectively. Compared to mc-Si PV cells, GaAs PV cells are more suitable for PV-TE hybrid systems and more adaptable under concentrated light conditions.

In this study, a novel composite flow channel was proposed to address issues of gas transport obstruction, poor water removal performance, high pressure drop, and low current density within the cathode flow channel of proton exchange membrane fuel cells (PEMFCs). The flow channel could optimize performance by combining a tapered design with a 3D wave structure. Based on a controlled variable method and three-dimensional (3D) multiphase computational fluid dynamics (CFD) simulations, the effects of the flow channel inlet and outlet side length ratio L D / d , amplitude A, and wavelength λ on PEMFC performance were investigated. As shown by results, appropriate decrease of L D / d , increase of A, and reduction of λ could increase convective mass transfer in the flow channel, improve the uniformity of the reaction gas distribution, and enhance the Water removal performance. Moreover, the optimal performance was achieved when L D / d = 1 / 3 , A = 0.3 mm and λ = 4 mm for PEMFC. Finally, when the cell output voltage was 0.4 V, the current density of the novel composite flow channel was up to 6.26% higher than that of the traditional 3D wave-shaped flow channel. • A novel composite channel considering a tapered-3D wavy structure is proposed. • Impact of structural parameters on PEMFC performance studied for novel channels. • Optimal parameter combination for the novel composite flow channel achieved. • The current density of the novel composite channel can increase by up to 6.26%. [ABSTRACT FROM AUTHOR]

Energy harvesting and power generation technologies hold significant potential for meeting future energy demands and improving environmental sustainability. A triboelectric nanogenerator (TENG), which harnesses energy from the surrounding environment, has garnered significant attention as a promising and sustainable power source applicable in various fields. In this study, we present a technique to improve the triboelectric performance of a PDMS-based TENG by incorporating nanostructured cadmium sulfide (N-CdS). This study investigates the utilization of CdS nanomaterials in TENG production, where mechanical energy is converted into electrical energy. We conducted a comparative analysis of TENGs utilizing N-CdS/PDMS, commercial CdS/PDMS (C-CdS/PDMS), and pure PDMS substrates. The N-CdS/PDMS substrates demonstrated superior triboelectric performance compared to TENG devices based on pure PDMS and C-CdS/PDMS. The triboelectric open-circuit voltage (Voc) and short-circuit current (Isc) of the N-CdS/PDMS-based TENG device were approximately 236 V and 17.4 µA, respectively, when operated at a 2 Hz frequency. These values were approximately 3 times and 2.5 times higher, respectively, compared to the pure PDMS-based TENGs. They were further studied in detail to understand the effect of different parameters such as contact–separation frequency and contact force on the TENGs' operation. The stability of the TENG devices was studied, and their potential to be integrated into self-powered smart textiles as power sources was demonstrated. [ABSTRACT FROM AUTHOR]

In order to optimize the performance of proton exchange membrane fuel cell (PEMFC), obstacles with transverse distribution were set up in the channel, and the effect of the arrangement mode, number, and size of obstacles on PEMFC performance was studied. It is found that obstacles with transverse distribution in the channel can accelerate reactant transfer to gas diffusion layer, improved the utilization rate of reactants, and promoted the local current density distribution and electrochemical performance of PEMFC. The obstacle with aligned distribution (type I) in the channel was superior to the staggered distribution (type II) in terms of fuel cell output characteristic and mass transfer. The best set of obstacles design schemes in this research was aligned distribution (type I), with the number of obstacles in a single channel reached 36, the length of the obstacle was 1 mm, the width was 0.2 mm, and the height was 1 mm. Compared with traditional scheme, the net power density of the designed scheme was increased by about 47.8%, and the drainage performance increased by about 32.6%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the advantages of superior wear resistance, mechanical durability, and stability, the liquid–solid triboelectric nanogenerator (LS-TENG) has been attracting much attention in the field of energy harvesting and self-powered sensors. However, most of the studies on LS-TENG focused on device innovations, changes in solid materials, and the effect of solid properties on output performance, and there is a lack of studies on liquids, especially at the molecular level. A U-tube LS-TENG was assembled to conduct experiments, whereby the effects of molecular structures, including molecular composition, carbon chain length, functional groups and material properties on the output performance were investigated. The deuterium replacing hydrogen and the atomic compositions could not achieve the enhancement of the output performance. Whether the chemical functional groups improve the output performance of LS-TENG depends on the mating solid material. Hydroxyl and cyanogenic groups can improve the output performance for the FEP case, while amide and cyanogenic groups can improve the output performance for the PTFE case. The order of output performances for functional groups of four groups of liquids with both FEP and PTFE materials is also obtained. It was also found that the dielectric constant is not positively correlated with the output performance. The results of this study might provide a reference for the deeper study and application of LS-TENG. [ABSTRACT FROM AUTHOR]

Conventional thermoelectric generators, predominantly based on the π-type structure, are severely limited in their applications due to the relatively low conversion efficiency. In response to the challenge, in this work, a Bi2Te3-based thermoelectric transistor driven by laser illumination is demonstrated. Under laser illumination, a temperature difference of 46.7 °C is produced between the two ends of the transistor structure. Further, the hole concentrations in each region redistribute and the built-in voltages decrease due to the temperature difference, leading to the formation of the transistor circuit. Additionally, the operation condition of the thermoelectric transistor is presented. The calculation results demonstrate that the maximum output power of such a designed thermoelectric transistor is 0.7093 μW. [ABSTRACT FROM AUTHOR]

Pneumatic motors have several advantages and have many robotics and automation applications. The importance of the study is that it is a cheap and possible way to apply it to the fixed displacement pneumatic motors with simple directional control valve used. The purpose of the addition to any traditional pneumatic motors is to change the fixed displacement pneumatic motor to be variable speed and torque compared to the expensive systems such as the proportional control valve in many industrial applications. The study also included validated simulations using the Automation Studio program to control the pneumatic motor's speed and torque. In addition, the results showed remarkable success in controlling the pneumatic motor outputs depending on the frequency of the compressed air-source pulses and pressure. The pulsating air frequencies of 1.5, 3, and 4.5 Hz were considered at different inlet source pressure changes from 1.72, 3.45, and 5.17 bar. As the pulsating flow frequency of compressed air decreased from 4.5, 3, and 1.5 Hz, the motor pressure and torque decreased. Furthermore, empirical correlations related to frequency and pressure effect have been developed. The error is 6.3–9.5% in predicting the motor speed and torque outputs. The limitation of the proposed method in real-life applications is about a maximum of 7.5 bar. On the other hand, the frequency is limited to 9 Hz using a mechanical solenoid. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the purpose of better matching the performance of the organic Rankine cycle (ORC) system concerning the vehicle engine waste heat recovery, this paper studies the output performance of free piston expander-linear generator (FPE-LG). A test bench of FPE-LG is established for small scale ORC system, and timing and displacement control strategy is proposed. Furthermore, the impact of the intake pressure and the torque on motion characteristics and output performance of FPE-LG are analyzed. According to evaluating different learning rates, number of hidden artificial neural networks and training functions, a prediction model of FPE-LG based on artificial neural network is established. Genetic algorithm is used to optimize the key operating parameters, to maximize the power output of FPE-LG. In consideration of the mean square error and determination coefficient, the artificial neural network model is verified and tested by experimental data. Finally, combining genetic algorithm with artificial neural network model, the maximum power output of FPE-LG is optimized and its performance is predicted. The results show that the maximum value of electric current, voltage and power output are 2.8 A, 14.75 V and 28.5 W, respectively. Based on artificial neural network, this method can provide useful guidance for performance prediction and coordinated optimization, with advantages of minimum deviation and high precision.

This paper investigated the variations in module temperature T and I-V,and analyzed the output law of photovoltaic modules in a day. Firstly, the temperature of the module during the day was found to be a result of coupling factors, not just related to the light intensity. The module output power was primarily determined by current, but not by voltage. Secondly, the series-parallel resistance of the modules basically decreased and then increased during the day. This was attributed to the increase in leakage current caused by high temperature and intense solar irradiance at noon. Compared with the series resistance, the parallel resistance was more affected by the environment during the day. Finally, the series and parallel resistances were relatively stable at high temperature conditions. The reason was that the nonlinear coupling factors that affect modules performance were more complex at low temperature condition. The above results were proved by comparing the theoretical and experimental series resistance. [ABSTRACT FROM AUTHOR]

Copyright of European Policy Analysis is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A 3D (three-dimensional) numerical simulation model is proposed to investigate the output performance and liquid water distribution of large-scale FF (flow field) considering DMGDZ ("dot matrix" gas distribution zone). The PEMFC (proton exchange membrane fuel cell) is affected by gravity, and the simulation results demonstrate that the PEMFC has the best output performance and water removal effect when the length and width of DM ("dot matrix") are 1.5 mm and 0.8 mm, respectively. The effect of gravity direction on liquid volume fraction in cathode large-scale FF is not obvious, but liquid volume fraction increases with the increase of the contact angle of GDL (gas diffusion layer) and working current density. The variation of water vapor condensation rate and the MPL (micro-porous layer) contact angle in porous electrodes significantly affects the amount of liquid water in the CFF (cathode flow field), and the PEMFC performance is degraded. Due to the enhancement of convection effect, the waveform channel can effectively remove the liquid water from the cathode channel and slightly strengthen the overall PEMFC performance. According to the results of waveform channel analysis, the comparison of waveform and straight FFs with DMGDZ shows that the waveform FF is more conducive to facilitate the liquid water removal on the cathode side. Simultaneously, the reactant gas distribution is uniform and the output performance is higher. • Large-scale flow field with DMGDZ is proposed to study the water management of PEMFC. • PEMFC shows better performance with the length and width of DM are 1.5 mm and 0.8 mm. • The GDL contact angle has a significant effect on the water removal in the PEMFC. • The condensation rate has an important effect on the liquid saturation in CCL. • Waveform flow field is favorable for liquid water removal and gas distribution. [ABSTRACT FROM AUTHOR]

Compared with thrombus dissolution using only thrombolytic agents, an advanced therapy of direct stirring of the blood clot can yield shorter recanalization time and higher recanalization velocity. Our previous research presented the design of a novel micro-stirrer, which can convert longitudinal vibration into transverse vibration and eventually generate opposite transverse vibration at the end-effort, like a scissor, for efficient blood clot stirring and thrombus dissolution acceleration. Transverse vibration is the most effective movement to dissolve thrombi. However, the small size of blood vessels has strict limits, which will greatly affect the output transverse vibration. Therefore, to improve the output performance of the micro-stirrer in curved and narrow vascular spaces, the analysis and structure optimization of the micro-stirrer is expected to increase the vibration mode conversion efficiency from longitudinal to transverse mode. The design concept and theoretical analysis of the micro-stirrer are presented in detail. Aiming to obtain the optimal structure parameters of the micro-stirrer, the mathematical model is established and analyzed. Next, a series of finite element models involving important structure parameters are designed and investigated. Finally, the optimal structure parameters are obtained, and the stirring effect in a blood vessel is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

With simple structure and control, impact inertial piezoelectric actuators are one promising type for precision positioning with large working stroke and high resolution. However, their applications still face some challenges, especially the incompatibility between speed and resolution as well as the motion instability due to the overturning moment. Therefore, innovative design of impact inertial actuators is urgently required. In this article, by designing an asymmetric compliant mechanism with a thick end and a thin end to generate asymmetric friction between the driving feet and U-groove, a novel impact inertial piezoelectric actuator was proposed. Its structure design, working principle, and output performances were addressed in detail. The results indicated that the thick end and thin end had quite different stepping characteristics, and the ideal stepping characteristic with quite small backward motion was achieved at the thick end. The displacement-time curves confirmed the motion stability of the actuator for bidirectional motions, and the small difference in forward and reverse speeds was explored. This actuator achieved the maximum speed of 7311 μm/s, the resolution of 221 nm, vertical and horizontal loading capacities being over 20 N and 1.4 N, respectively. Performance comparison with some previous impact inertial actuators further demonstrated the advancement. [ABSTRACT FROM AUTHOR]

This study investigates the use of photovoltaic (PV) arrays on airships, focusing on challenges due to the curved structure that affects solar radiation distribution. A novel Photo-Thermal-Electric Model (PTEM), developed in MATLAB/Simulink, is introduced to simulate PV array behavior under various conditions, including the impact of solar altitude, laying angle, and airship flight attitude on power generation. PTEM's effectiveness is demonstrated through detailed power output graphs, revealing that radiation gradients significantly affect power generation, often leading to overestimations in the Photo-Thermal Model (PTM) model by 3 %–30 %. Comparative analysis shows that PTEM provides more accurate energy output estimates for individual PV modules, especially in areas with pronounced radiation gradients, differing from PTM estimates by hundreds of watts. These findings offer valuable insights for enhancing PV module lifespan and optimizing energy system designs, contributing to more efficient renewable energy solutions for long-endurance aircraft. [ABSTRACT FROM AUTHOR]

Research on proton exchange membrane fuel cells (PEMFC) has mainly focused on the design of gas channels, often neglecting the effects of distribution zones and cooling flow fields (CFF) on the cell. Therefore, a novel bipolar plate (BP) structure of metallic material is proposed in this paper, which adopts a three-stage forked distribution zone and a wave staggered round table cooling flow field (WSRTCFF). This study systematically investigates the effects of WSRTCFF presence or absence, flow direction, velocity, and inlet temperature on heat and mass transfer as well as PEMFC performance. The results show that introducing WSRTCFF significantly improves temperature distribution in the flow field. Compared to hydrogen flow direction, oxygen flow direction not only effectively mitigates local hot spot effects but enhances current density by 12.55 % compared to no cooling. When coolant flow velocity is below 0.1 m/s, increasing velocity promotes system heat dissipation, enhancing working efficiency and cell stability. However, when velocity exceeds 0.1 m/s, the change in the flow velocity has minimal effect on PEMFC performance. Furthermore, comparative analysis of different coolant temperatures indicates that at 333.15 K, maximum temperature remains below 348.2 K, maintaining membrane hydration and achieving a good balance of substances, temperatures, and performance. [Display omitted] • Co-direction with oxygen can significantly enhance the performance of the cell. • In this model, the most appropriate flow velocity of the coolant is 0.1 m/s. • The coolant temperature of 333.15 K accelerates the hydrogen-oxygen amalgamation. [ABSTRACT FROM AUTHOR]

Piezoelectric stick-slip actuators (PSSAs) utilize sliding friction between the mover and stator to convert and transmit motion. However, the phenomenon of backward displacement often hinders the output performance of PSSAs. This paper proposes a method to mitigate backward displacement and enhance output performance by modifying the overall flexibility of the actuator. The key idea of this approach is to propose a novel flexible hinge structure and apply it to PSSA. Numerical calculations and finite element analysis confirm that the flexibility and output performance of the PSSA are significantly improved. The method's feasibility is supported by comparing experiments. The experimental results show that under the same locking force, the optimal excitation frequency of perforated Elliptical Flexure Hinge (EFH) is significantly lower than the non-perforated EFH and the speed is increased over 53 %. Furthermore, the PSSA has a maximum load capacity of 190 g, which is 31.7 times its own weight (6 g). The proposed PSSA can provide valuable insights for its application in precision motion control systems in the foreseeable future. [Display omitted] • New compliant mechanic with perforation of piezoelectric stick-slip actuators introduced. • Enhances flexibility of compliant mech and improves piezoelectric stick-slip actuator displacement control. • Verified piezoelectric stick-slip actuator performance via theory, simulation, and testing. [ABSTRACT FROM AUTHOR]

Energy harvesting and power generation technologies hold significant potential for meeting future energy demands and improving environmental sustainability. A triboelectric nanogenerator (TENG), which harnesses energy from the surrounding environment, has garnered significant attention as a promising and sustainable power source applicable in various fields. In this study, we present a technique to improve the triboelectric performance of a PDMS-based TENG by incorporating nanostructured cadmium sulfide (N-CdS). This study investigates the utilization of CdS nanomaterials in TENG production, where mechanical energy is converted into electrical energy. We conducted a comparative analysis of TENGs utilizing N-CdS/PDMS, commercial CdS/PDMS (C-CdS/PDMS), and pure PDMS substrates. The N-CdS/PDMS substrates demonstrated superior triboelectric performance compared to TENG devices based on pure PDMS and C-CdS/PDMS. The triboelectric open-circuit voltage (Voc) and short-circuit current (Isc) of the N-CdS/PDMS-based TENG device were approximately 236 V and 17.4 µA, respectively, when operated at a 2 Hz frequency. These values were approximately 3 times and 2.5 times higher, respectively, compared to the pure PDMS-based TENGs. They were further studied in detail to understand the effect of different parameters such as contact–separation frequency and contact force on the TENGs’ operation. The stability of the TENG devices was studied, and their potential to be integrated into self-powered smart textiles as power sources was demonstrated.

Magnetostrictive electro-hydraulic actuator (M-EHA) is a highly integrated hydraulic servo device with very complex movement and conduction processes. The output performance could be affected by many factors. To design such actuator and analyze its performance with simple and efficient analysis method, an M-EHA impedance network modeling method considering the fluid inertia and the compressibility is proposed. The M-EHA components behavior were respectively described based on the fluid flow continuous equation, the pressure drop equation, and the dynamic motion equation. By employing the electro-mechanical and electro-hydraulic analogies, the impedance network of M-EHA is established and the output performance is analyzed. Through independent impedance analysis of different structures of the M-EHA, the natural frequency and dynamic characteristics of manifold, hydraulic cylinder, and accumulator are obtained respectively, and this provides the theoretical guidance for optimizing the actuator structure and performance. The influence of driving frequency, system bias, and load on the output performance of M-EHA are studied based on the impedance network. Simulations show that the best output performance is obtained under 593 Hz with 1.2 MPa system bias pressure, and the flow is 0.52 L/min.

The flow field optimization design is one of the important methods to improve the performance of proton exchange membrane fuel cell (PEMFC). In this study, a new structure with staggered blocks on the parallel flow channels of PEMFC and auxiliary flow channels under the ribs is proposed. Through numerical calculation method, the effect of blocks auxiliary flow field (BAFF) on pressure drop, reactant distribution and liquid water removal in the fuel cells are investigated. The results show that when the operating voltage is 0.5 V, the current density of BAFF is 21.74% higher than that of the straight parallel flow field (SPFF), and the power density reaches 0.65 W cm−2. BAFF improves performance by equalizing the pressure drop across sub-channels, promoting the uniform distribution of reactant, and enhancing transport across the ribs. In addition, through parameter analysis, it is found that BAFF can discharge liquid water in time at the conditions of high humidification, high current density and low temperature, which ensures the output performance of the fuel cell and improves the durability of the fuel cell. This paper provides new ideas for the improvement of PEMFC flow field design, which is beneficial to the development of PEMFC with high current density. • A 3D PEMFC model incorporating liquid water transport is established and validated. • Staggered blocks and auxiliary flow channels are arranged in the flow field. • Effect of the working environment on the newly designed structure is investigated. • The new flow field structure increases the maximum output power by 21.74%. • Auxiliary channels have a significant improvement in liquid water removal. [ABSTRACT FROM AUTHOR]

Compressed air energy storage is a promising technology with the advantages of zero pollution, long lifetime, low maintenance, and minimal environmental impact. However, compressed air energy storage has some disadvantages, such as low efficiency and low energy density. A parallel operation mode of pneumatic motor is proposed in this study to improve the power performance, energy conversion efficiency, and economy of compressed air energy storage system. First, the test bench of compressed air energy storage system is established. Then, the influence of key parameters, such as current, rotating speed, and regulated pressure, on the output performance of compressed air energy storage system is investigated in this study. Afterward, the interaction among volume flow rate, rotating speed, torque, output power of pneumatic motor, and the current, voltage, and output power of the generator, as well their influence on one another, are discussed. Finally, the output performances of compressed air energy storage system when the pneumatic motor works alone and in parallel are compared and analyzed. The experimental results show that the power performance, energy conversion efficiency, and economy of compressed air energy storage system can be improved when the pneumatic motor works in parallel operation mode. The minimum compressed air consumption rate is 0.1369 g/J, the maximum power output is 818 W, the maximum efficiency of the generator is 88.7%, and the maximum efficiency of pneumatic motor is 6.5% when the pneumatic motor works in parallel operation mode. [ABSTRACT FROM AUTHOR]

Compressed-air vehicles have the advantages of zero pollution and low cost. A compressed-air engine test bench is established in this study. The effects of rotational speed, torque, and regulated pressure on the power performance, economy, and energy conversion efficiency of the pneumatic motor are investigated. The differences in power output, compressed-air consumption rate, and energy conversion efficiency between forward and reverse rotation of the pneumatic motor are compared and analyzed. To effectively investigate the performance of a compressed-air vehicle under various road conditions, this study compares and analyzes the power performance, economy, and energy conversion efficiency of pneumatic motors under different road conditions. Experimental results show that the power output and energy conversion efficiency of the pneumatic motor in reverse rotation are less than those in forward rotation, indicating that the pneumatic motor has better power performance and higher efficiency with forward rotation than reverse rotation. The compressed-air consumption rate of the pneumatic motor with reverse rotation is higher than that with forward rotation, indicating that the pneumatic motor with forward rotation has better economic performance than with reverse rotation. The maximum power output and energy conversion efficiency of the pneumatic motor are about 1220 W and 13.23%, respectively. [ABSTRACT FROM AUTHOR]

Cellulose, a biomass material prepared by plants or bacterial, has high specific surface area, good biocompatibility and excellent mechanical flexibility. The hydroxyl group on the molecular chains of cellulose gives it a strong ability to lose electrons. The dipoles formed by the hydrogen bonds between the molecular chains endow it piezoelectric properties. Besides, cellulose has renewable and degradable merits, so it can be used as an environment-friendly material to prepare flexible nanogenerators. This paper mainly introduces the research progress of cellulose-based piezoelectric nanogenerators, friction nanogenerators and hybrid piezoelectric/friction nanogenerators in recent years. The development prospects and challenges of cellulose-based nanogenerators are also discussed. [ABSTRACT FROM AUTHOR]

Microfluidic microbial fuel cells (MMFC) are one of the most promising power sources. However, due to the lack of clarity in the internal operating mechanism, the output performance is suboptimal. Thus, a comprehensive two-dimensional cathode dual-population model is developed to gain deeper insights into internal workings. Based on verifying the accuracy of the model, the influence of temperature, ionic strength, and spacing of electrode on the performance and microbial growth of MMFC are explored. The finding reveal a nonlinear trend in the performance of MMFC at temperatures of 293.15 K and 313.15 K. Furthermore, the impact of electrode spacing and ionic strength on the performance of MMFC is examined, thereby emphasizing the applicability in experimental research and numerical simulation. This study provided insights into the operating mechanism of dual-population microbial microfluidic fuel cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

As a novel energy harvesting technology, bettering the output performance of triboelectric nanogenerators (TENGs) is vital. Although quite a number methods to increase charge density have been proposed, challenges such as high impedance matching and low output current persist, severely limit the energy utilization efficiency of TENGs. Here, a new power management circuit (PMC) is proposed that through charge storage and release strategy. This circuit first excites the surface charge of the TENG using the charge excitation circuit, and then releases the stored charge through a self-triggered switch. Compared to a standard TENG, the output current of the TENG with this PMC is increased by a factor of 1108, the impedance is decreased from 100 MΩ to 10 kΩ, and the energy utilization efficiency is markedly improved. This work affords a reference for enhancing the output performance of TENG, reducing impedance, and broading the utility attainable of TENGs., (© 2024 Wiley‐VCH GmbH.)

This paper establishes a test bench for a free piston expander–linear generator (FPE–LG) system coupled with the drive motor (DM) to promote the application of FPE–LG on vehicle. Firstly, it discusses the operating characteristics and output performance of the FPE–LG under the simulated operation conditions of vehicle. Meanwhile, it investigates the operating characteristics of FPE–LG under different torques and expansion times. Finally, this paper analyzes the influence of different torques and expansion times on the operating frequency of FPE–LG. The experimental results show that the operating frequency of FPE–LG is related to the expansion time and torque. The power output of the DM decreases as the torque increases, the power output of the DM increases first and then decreases as the expansion time increases. Therefore, the selection of suitable expansion time under different intake pressure plays an important role in improving the power output of the DM. The maximum of the peak power output of DM is about 25.8 W, when the intake pressure is 4 bar, the expansion time is 30 ms and the torque is 0.00571 N m.

With the advantages of superior wear resistance, mechanical durability, and stability, the liquid–solid triboelectric nanogenerator (LS-TENG) has been attracting much attention in the field of energy harvesting and self-powered sensors. However, most of the studies on LS-TENG focused on device innovations, changes in solid materials, and the effect of solid properties on output performance, and there is a lack of studies on liquids, especially at the molecular level. A U-tube LS-TENG was assembled to conduct experiments, whereby the effects of molecular structures, including molecular composition, carbon chain length, functional groups and material properties on the output performance were investigated. The deuterium replacing hydrogen and the atomic compositions could not achieve the enhancement of the output performance. Whether the chemical functional groups improve the output performance of LS-TENG depends on the mating solid material. Hydroxyl and cyanogenic groups can improve the output performance for the FEP case, while amide and cyanogenic groups can improve the output performance for the PTFE case. The order of output performances for functional groups of four groups of liquids with both FEP and PTFE materials is also obtained. It was also found that the dielectric constant is not positively correlated with the output performance. The results of this study might provide a reference for the deeper study and application of LS-TENG.

This paper presents a proton exchange membrane fuel cell (PEMFC) using anode and cathode printed circuit boards (PCBs) to load the membrane electrode assembly (MEA). A three-dimensional CFD-electrochemical model of the PCB-based PEMFC is developed and used to calculate the internal species, charge, and water distribution. The effects of the shape of the inlet opening, the opening ratio and the relative humidity of the air on the output performance of the PEMFC are investigated. To validate the simulation model, the output performance of the PEMFC is tested under the same operating conditions. The results show that circular and rounded rectangular openings show better PEMFC output performance than U-shaped openings, and the output performance of PEMFC is improved as the opening ratio of the inlet openings and the relative humidity of air increase. The results will provide specific reference values for the design of PCB-based planar PEMFC stacks. • A PCB-based PEMFC is constructed using anode and cathode PCBs to carry the MEA. • A 3D CFD-electrochemical model of PCB-based PEMFC is built to optimize it. • The effects of the shape of inlet openings, opening ratio and air relative humidity are investigated. • Membrane dehydration is a potential problem. [ABSTRACT FROM AUTHOR]

In the ordinary way, the output performance of 85Kr radioactive source depends on activity, 85Kr radioactive sources with equal activity have similar output performance. But the output performance of 85Kr thickness gauge source on the market is inconsistent while the sources have the same size and activity, and this may be related to the preparation process of 85Kr radioactive source by different suppliers. Furthermore, preparation process that shell material, active region and feed gas should be considered. 85Kr radioactive source with equal activity (7.4 GBq) were prepared by different shell material, active region and feed gas with different abundances. The output voltage of these 85Kr radioactive sources were measured by 85Kr β output voltage device developed by HTA Co., Ltd. The results show that 85Kr radioactive source prepared by titanium shell has lager output voltage than stainless shell, 85Kr radioactive source prepared by small activity region has a little bit lager output voltage than big activity region, and output voltage of 85Kr radioactive source prepared by more abundant feed gas is slightly lager than less abundant feed gas. This because that 85Kr radioactive source prepared by titanium shell, small activity region and lager abundant feed gas has less absorption of beta rays than that prepared by stainless shell, big activity region and less abundant feed gas. This can guidance on of preparation for 85Kr thickness gauge source based on β output efficiency.