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Plastic Crystal Neopentyl Glycol/Multiwall Carbon Nanotubes Composites for Highly Efficient Barocaloric Refrigeration System

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Journal of Thermal Science 2024年第1期33卷 383-393页

作者： DAI Zhaofeng SHE Xiaohui SHAO Bohan YIN ershuai DING Yulong li Yongliang ZHANG Xiaosong ZHAO Dongliang School of Energy&Environment Southeast UniversityNanjing 210096China School of Mechanical Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China School of Energy and Power Engineering Nanjing University of Science&TechnologyNanjing 210094China Birmingham Centre for Energy Storage School of Chemical EngineeringUniversity of BirminghamBirmingham B152TTUK

Plastic crystal neopentyl glycol(NPG)exhibits colossal barocaloric effect with high entropy changes.However,their application is restricted in several aspects,such as low thermal conductivity,substantial supercooling effect,and poor springback properties.In this work,multi-walled carbon nanotubes(MWCNTs)with ultra-high thermal conductivity and high mechanical strength were selected for performance enhancement of NPG.The optimal mixing ratio was determined to be NPG with 3 wt%MWCNTs composites,which showed a 6K reduction in supercooling without affecting the phase change enthalpy.Subsequently,comprehensive performance of the composites with optimal mixing ratio was compared with pure NPG At 40 MPa,390J·K^(-1)·kg^(-1)change in entropy and 9.9 K change in temperature were observed.Furthermore,the minimum driving pressure required to achieve reversible barocaloric effect was reduced by 19.2%.In addition,the thermal conductivity of the composite was increased by approximately 28%,significantly reducing the heat exchange time during a barocaloric refrigeration cycle.More importantly,ultra-high pressure release rate resulted in a73.7%reduction in the springback time of the composites,offering new opportunities for the recovery of expansion work.

关键词： barocaloric refrigeration neopentyl glycol MWCNTs performance enhancement

Deterministic bound for avionics switched networks according to networking features using network calculus

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Chinese Journal of Aeronautics 2017年第6期30卷 1941-1957页

作者： Feng HE ershuai li School of Electronic and Information Engineering Beihang University

The state of the art avionics system adopts switched networks for airborne communications. A major concern in the design of the networks is the end-to-end guarantee ability. Analytic methods have been developed to compute the worst-case delays according to the detailed configurations of flows and networks within avionics context, such as network calculus and trajectory approach. It still lacks a relevant method to make a rapid performance estimation according to some typically switched networking features, such as networking scale, bandwidth utilization and average flow rate. The goal of this paper is to establish a deterministic upper bound analysis method by using these networking features instead of the complete network configurations. Two deterministic upper bounds are proposed from network calculus perspective: one is for a basic estimation,and another just shows the benefits from grouping strategy. Besides, a mathematic expression for grouping ability is established based on the concept of network connecting degree, which illustrates the possibly minimal grouping benefit. For a fully connected network with 4 switches and 12 end systems, the grouping ability coming from grouping strategy is 15–20%, which just coincides with the statistical data(18–22%) from the actual grouping advantage. Compared with the complete network calculus analysis method for individual flows, the effectiveness of the two deterministic upper bounds is no less than 38% even with remarkably varied packet lengths. Finally, the paper illustrates the design process for an industrial Avionics Full Duple X switched Ethernet(AFDX) networking case according to the two deterministic upper bounds and shows that a better control for network connecting, when designing a switched network, can improve the worst-case delays dramatically.

关键词： Deterministic bound Grouping ability Network calculus Networking features Switched networks

Research on Testing Methods of Ⅰ-Ⅴ Characteristics of Solar Photovoltaic Cell Array

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Research on Testing Methods of Ⅰ-Ⅴ Characteristics of Sola...

The 2011 International Conference on Electric and Electronics (EEIC 2011)

作者： Yunhai Hou ershuai li Shihua Sun School of Electric ＆ Electric Engineering Changchun University of Technology

By testing the I-V characteristics of the solar photovoltaic cell array and referencing the experimental data, it can effectively evaluate the PV power plant control and design standards. In order to get the accurate test to the characteristics of solar photovoltaic cell array data, test its I-V characteristics, we use the dynamic capacitance charging test method, according to the characteristics of capacitors, take the dynamic capacitance as a solar PV array variable load, through the current and voltage sampling on the whole process of charging the capacitor for the photovoltaic cell array, then get I-V curve of PV array.

关键词： Solar photovoltaic cell array I-V characteristics Dynamic capacitance Sampling

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钎焊工艺对双层焊管材料时效性能的影响

热加工工艺 2024年第9期53卷 55-58,63页

作者：刘顺明张志敏龙佳明庞二帅梁斌李悦刘再旺首钢京唐钢铁联合有限责任公司制造部河北唐山063210 首钢集团有限公司技术研究院北京100043

使用退火模拟器对双层焊管用钢带进行热处理,模拟其在不同制管速度、钎焊温度下的钎焊过程。使用拉伸试验机检测不同钎焊温度及不同制管速度下钢带的屈服点延伸率和时效指数,以研究钎焊温度和制管速度对双层焊管材料时效性能的影响。结... 详细信息

使用退火模拟器对双层焊管用钢带进行热处理,模拟其在不同制管速度、钎焊温度下的钎焊过程。使用拉伸试验机检测不同钎焊温度及不同制管速度下钢带的屈服点延伸率和时效指数,以研究钎焊温度和制管速度对双层焊管材料时效性能的影响。结果表明,钎焊温度越高,材料的屈服点延伸率越小,时效指数也越小,制管的抗时效性越好。随着制管速度的提高,钎焊后钢带的屈服点延伸率和时效指数均呈增大趋势,抗时效性变差。这是由于制管生产速度增大,冷却段时间变短,渗碳体析出量减小造成的。钎焊前钢带时效指数为10.6 MPa,模拟钎焊后钢带的时效指数为76.8~104.9 MPa,其抗时效性明显变差。

关键词：双层焊管时效指数钎焊工艺

Formal Modeling of Frame Selection in Asynchronous TSN Communications

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Chinese Journal of Electronics 2023年

作者： li ershuai ZHOU Xuan SUN Jinjing XIONG Huagang HE Feng School of Electronic and Information Engineering Beihang University

The asynchronous Time-Sensitive Networking(TSN) based on IEEE 802.1Qcr is expected to be a promising solution for the asynchronous transmissions of safety-critical flows without the support of clock synchronization. When the Asynchronous Traffic Shaping(ATS) mechanism is adopted to meet the deadline requirements for transmissions of safety-critical flow, it is necessary to formally verify the real-time properties and corresponding network performance. However, it is still unclear how to build an efficient formal model to evaluate different frame selection methods during the ATS scheduling process, which originate from the dominations of priority or eligibility time. In this paper, we present a formal modeling framework to compare the impacts of different frame selection on transmission sequence under the asynchronous ATS mechanism. According to the priority level(pATS) or eligibility time(eATS) for flows,two transmission selection methods in ATS are modeled and compared. Then, we verify the real-time properties of ATS. The result shows that the shaping-for-free property can be satisfied with the pATS method but can not be fulfilled with the eATS method. Besides, the timing analysis results illustrate that the eATS method can provide more fairness than the pATS method for the transmission of low-priority flows in TSN networks.

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Effect of non-uniform illumination on performance of solar thermoelectric generators

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Frontiers in Energy 2018年第2期12卷 239-248页

作者： ershuai YIN Qiang li Yimin XUAN MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power Engineering Nanjing University of Science and Technology Nanjing 210094 China IMIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power Engineering Nanjing University of Science and Technology Nanjing 210094 China School of Energy and Power Nanjing University of Aeronautics and Astronautics Nanjing 210016China

Solar thermoelectric generators （STEGs） are heat engines which can generate electricity from concentrated sunlight. The non-uniform illumination caused by the optical concentrator may affect the performance of solar thermoelectric generators. In this paper, a three- dimensional finite element model of solar thermoelectric generators is established. The two-dimensional Gaussian distribution is employed to modify the illumination profiles incident on the thermoelectric generator. Six non-uniformities of solar illumination are investigated while keeping the total energy constant. The influences of non-uniform illumination on the temperature distribution, the voltage distribution, and the maximum output power are respectively discussed. Three thermoelectric generators with 32, 18 and 8 pairs of thermocouples are compared to investigate their capability under non-uniform solar radiation. The result shows that the non-uniformity of the solar illumination has a great effect on the temperature distribution and the voltage distribution. Central thermoelectric legs can achieve a larger temperature difference and generate a larger voltage than peripheral ones. The non-uniform solar illumination will weaken the capability of the TE generator, and the maximum output power decrease by 1.4% among the range of non-uniformity studied in this paper. Reducing the number of the thermoelectric legs for non-uniform solar illumination can greatly increase the performance of the thermoelectric generator.

关键词： solar thermoelectric generators non-uniform solar illumination performance evaluation solar energy

基于遗传算法的光伏-热电耦合系统多目标优化研究

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工程热物理学报 2023年第6期44卷 1669-1674页

作者：殷二帅李强南京理工大学能源与动力工程学院电子设备热控制工信部重点实验室南京210094

多因素共同作用下的系统优化设计是光伏-热电耦合系统研究的难点之一。本文建立了光伏-热电耦合系统与单一光伏系统的理论模型,以最高耦合效率与相对于单一光伏系统的最大效率差值为优化目标,采用多目标遗传算法,开展了耦合系统优化设... 详细信息

多因素共同作用下的系统优化设计是光伏-热电耦合系统研究的难点之一。本文建立了光伏-热电耦合系统与单一光伏系统的理论模型,以最高耦合效率与相对于单一光伏系统的最大效率差值为优化目标,采用多目标遗传算法,开展了耦合系统优化设计研究。结果表明,最高耦合效率与最大效率差值两个优化目标是负相关的,且其负相关性是由光伏参考效率所导致,需综合考虑系统经济性,确定最高耦合效率和最大效率差值的折中方案,从而获得耦合系统最佳设计。

关键词：光伏-热电耦合系统多目标优化遗传算法全光谱利用

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TSN时间敏感流量带宽分配与优化

系统工程与电子技术 2022年第6期44卷 2027-2034页

作者：赵长啸李二帅何锋王鹏中国民航大学安全科学与工程学院天津300300 北京航空航天大学电子信息工程学院北京100191

针对时间敏感网络(time-sensitive networking,TSN)中时间敏感流量的带宽分配,必须要根据流量传输的实时性需求,并考虑不同类型流量的占比,提供具体的优化策略和带宽分配结果。首先,基于网络演算方法,建立时敏流量带宽分配评估模型;然后... 详细信息

针对时间敏感网络(time-sensitive networking,TSN)中时间敏感流量的带宽分配,必须要根据流量传输的实时性需求,并考虑不同类型流量的占比,提供具体的优化策略和带宽分配结果。首先,基于网络演算方法,建立时敏流量带宽分配评估模型;然后,根据实时性需求构建带宽分配的约束条件,采用启发式方法,实施带宽分配的优化;最后,通过案例,验证带宽分配在不同链路负载率和流量占比下的变化趋势。实验结果表明,采用基于信用量的流量整形机制,当案例中A类型流量的带宽分配占比为70%时,可获得最佳带宽匹配效果,实现网络中所有流量端到端延迟和最小的流量传输。

关键词：时间敏感网络带宽分配网络演算启发式算法性能评估

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机载时间敏感组网分析综述

航空学报 2023年第17期44卷 20-44页

作者：何锋李二帅周璇赵露茜北京航空航天大学电子信息工程学院北京100083

时间敏感网络“准时、准确”的调度与传输机制可以有效地提升工业自动化系统、车载综合电子系统中信息交互的确定性,潜在的也成为了机载系统高确定性组网的候选方案之一,但如何将其多种时间敏感整形和调度机制与机载组网环境和需求进行... 详细信息

时间敏感网络“准时、准确”的调度与传输机制可以有效地提升工业自动化系统、车载综合电子系统中信息交互的确定性,潜在的也成为了机载系统高确定性组网的候选方案之一,但如何将其多种时间敏感整形和调度机制与机载组网环境和需求进行匹配,是当下首要解决的问题。在对现阶段的时间敏感网络的标准进行总结的基础上,详细分析了机载组网的需求,并从时间敏感网络调度与优化、保证时延边界分析两方面总结了当下时间敏感网络相关研究的最新进展,以及与机载组网环境相结合的考虑,进一步针对机载组网的典型需求,从协议剪裁、体系管理、模型工程、可靠安全、无线混传等方面详细讨论了时间敏感网络技术在机载环境应用所面临的挑战和关键技术。

关键词：航空电子系统机载网络时间敏感网络通信调度时延分析