A peapod-like ZnO@C design with internal void space to relieve its large-volume-change as lithium-ion battery anode

Peapod-like ZnO@C with internal void space has been synthesized by calcination of ZnO/ZnOHF@polydopamine nanorods. By designing both the large void space between particles and external elastic carbon shell, the large volume change of ZnO during charge-discharge process could be effectively relieved. Moreover, the carbon shell functioned as an electronic conductor and elastic barrier, could accelerate the reaction kinetics and confine stable SEI films formation on the outer protective layer to further improve the structural integrity. Benefiting from these structure advantages, the peapod-like ZnO@C presents a prominent electrochemical performance with a retained discharge capacity of 565.1 mA h g^?1 at 0.2 A g^?1 and high rate capacity of 246.6 mA h g^?1 even at 4 A g^?1.     

受限空间安全作业管理浅析

受限空间因受作业场所限制,存在的危险因素较多,受限空间安全管理控制措施为:建立许可制,落实责任和措施,做好受限空间作业人员的个体防护,对受限空间作业的安全管理要实行从审批到应急处理全过程的控制。介绍了受限空间的危险特点和事故类型,提出了受限空间作业安全管理的具体措施。     

New approaches to determine the interface height of fire smoke based on a three-layer zone model and its verification in large confined space

Large confined space has high incidence of fires, which seriously threatens the safety of people working there. Understanding the distribution of smoke in such large space is critical to fire development prediction and smoke control. Three improved methods for the stratification interface prediction of fire smoke are developed, including of improved intra-variance, integral ratio and N-percentage methods. In these methods, the interface height is determined by the vertical temperature distribution based on a three-layer smoke zone model, which is an improvement of a two-layer zone model. Thereafter, the three improved methods are applied to several typical fire cases simulated CFD to predict the smoke interface, and their applicability and reliability are verified by comparison of the smoke stratification results with the filed simulation results. Results show that the three improved methods can effectively determine the location of the three-layer zone model's interface, and they have the ability to predict smoke interface for fires with different fire source types and ventilation conditions.     

浮法玻璃熔窑火焰空间石油焦部分替代重油燃烧的数值模拟

针对浮法玻璃熔窑火焰空间建立模型并进行了数值模拟，在保证热值相同的前提下，对比研究了重油燃烧及将石油焦部分替代重油燃烧时的流场分布特征。结果表明，石油焦部分代替重油燃烧后，两种燃料可很好地混合燃烧，窑炉内温度制度基本不受影响；石油焦着火时间比重油长，两种燃料混合燃烧时平均着火点滞后于仅使用重油时，且燃烧路径更长，燃烧时产生了大量CO，整个火焰空间及烟气出口处NOx的平均排放量与仅使用重油相比降低了30.02%，NOx减排效果明显。     

一种计算空间异面高压线间最短距离的方法

在电力工程建设、运行、管理中,需要遵循许多行业规范,尤其是高压线间的间距,关系到电网运行的安全与否。对于一些容易判断两线间最短距离的高压线,如平行的高压线等,可以方便的求出其最短距离,但是,在遇到一些不易判断出两线间最短距离位置的高压线时,需要通过一定的方法求出两高压线间的最短距离,以判断是否符合规范要求,确保电网的安全运行。本文提出一种利用Mathematica软件计算空间异面高压线间最短距离的方法。     

关于信息化测绘时代工程测量发展的思考

如今我国信息化技术全面发展，尤其对于工程测量工作领域来讲，不管是在工程建设和管理方面都产生不小的支撑引导效用。由此，笔者具体结合如今工程建设信息化测绘核心任何以及设备布置细节，进行结构整体安全管理周期和周边地理空间信息技术发展能效整理解析，试图将工程测量最新发展机遇和技术挑战问题处理完全。希望能够借此为日后一定时期范围内相关工程测量规划主体提供合理指导性建议内容，最终为我国各类工程事业可持续发展前景绽放奠定深刻适应基础。     

受限空间内天然气爆炸反应过程模拟分析

为定量研究受限空间内天然气爆炸反应动力学特征，开展了3个方面的研究工作，①建立了基于激波管的天然气爆炸过程数值分析模型；②将天然气气相燃烧动力学反应分解为53种反应组分、325种基元反应，给出了朗金―雨贡尼关系式和正激波的压强比、密度比和温度比计算方法；③利用化学反应模拟软件CHEMKIN构建天然气燃烧过程机理文件，对激波诱导受限空间内天然气混气爆炸过程进行数值模拟，讨论了反应过程、初始压力和空间尺寸对天然气爆炸过程的影响，并绘制了天然气爆炸温度、压力变化特征曲线。结果表明：采用入射激波模拟混气引爆过程中体系温度会出现跳跃式上升随之向下扰动；混气被引爆后温度逐步提高，在温度达到峰值时压力随之提高；提高初始压力将缩短混气引爆时间，高的初始压力可以得到更为迅速的反应速度和更高的爆炸压力；空间尺寸对散热作用的影响高于其对活性基团消毁作用的影响，小尺寸空间条件下可以获得更迅速的爆炸升压速度。     

Electrical Breakdown Properties and Space Charge Formation in High Temperature Region in Ultraviolet Ray Irradiated PVC

Polyvinyl chloride (PVC) is the most popular insulating material for electric wiring instruments. However, an exothermic reaction above 150 °C may cause deterioration of the insulating properties of PVC. Therefore, it is important to clarify the heat degradation in PVC, not only to investigate the ignition of electrical wiring products but also to use electrical products safely. It is known that ultraviolet (UV) irradiation causes chemical deterioration of PVC and an increase in its conductivity. Generally, it has been thought that the electrical breakdown properties, electrical conduction, and insulating performance are affected by space charge accumulation in an insulating material. A high temperature pulsed electroacoustic (PEA) system usable up to 250 °C has been developed, and the PEA system can measure the space charge distribution and conduction current in the high temperature range simultaneously. In this investigation, the space charge distribution and conduction current were measured up to electrical breakdown in a non‐UV irradiated sample (normal PVC) and in 353 nm and 253 nm UV‐irradiated PVC samples in the range from room temperature to 200 °C in a DC electric field. In the short wavelength UV irradiated PVC sample (253 nm, 300 h), a deterioration of breakdown strength at 90 °C to 150 °C and negative packet‐like charges were observed at 60 °C and 100 °C, a positive charge accumulated in front of both the anode and cathode above 90 °C, and a higher electric field near the cathode side because the positive charge of the cathode side was greater.     

Model-Based Design Space Exploration for FPGA-based Image Processing Applications Employing Parameterizable Approximations

The increasing demand for low power consumption and high computational performance is outpacing available technological improvements in embedded systems. Approximate computing is a novel design paradigm trying to bridge this gap by leveraging the inherent error resilience of certain applications and trading in quality to achieve reductions in resource usage. Numerous approximation methods have emerged in this research field. While these methods are commonly demonstrated in isolation, their combination can increase the achieved benefits in complex systems. However, the propagation of errors throughout the system necessitates a global optimization of parameters, leading to an exponentially growing design space. Additionally, the parameterization of approximated components must consider potential cross-dependencies between them. This work proposes a systematic approach to integrate and optimally configure parameterizable approximate components in FPGA-based applications, focusing on low-level but high-bandwidth image processing pipelines. The design space is explored by a multi-objective genetic algorithm which takes parameter dependencies between different components into account. During the exploration, appropriate models are used to estimate the quality-resource trade-off for probed solutions without the need for time-consuming synthesis. We demonstrate and evaluate the effectiveness of our approach on two image processing applications that employ multiple approximations. The experimental results show that the proposed methods are able to produce a wide range of Pareto-optimal solutions, offering various choices regarding the desired quality-resource trade-off.     

Dual closed-loops current controller for a 4-leg shunt APF based on repetitive control

ABSTRACT

Current repetitive control strategy for a 4-leg APF is usually of a poor speed in responding to the drastic changes in load harmonic profile. In this paper, a dual closed-loop current controller composed of a repetitive control-based outer loop and a PI-based inner loop is proposed to improve the performance of a 4-leg APF, with a focus on response speed and harmonic current compensation gain. The principle of the dual loop controller is explained in detail, and the stability of the system is analysed thoroughly. To further decrease the inherent time delay associated with the PWM strategy, a zero-sequence-voltage-based PWM strategy is proposed to solve the complexity in the implementation of 3D-SVPWM methods. By formulating the relationship between the duty ratio of the neutral leg control pulse and the zero-sequence-component of the reference voltages, the duty ratios of the other three legs can be calculated conveniently. The simulation and lab experiment results are provided to verify the correctness and effectiveness of the proposed dual closed-loop current controller and the zero-sequence-voltage-based PWM strategy.