A numerical study of dynamic behaviors of a unitized regenerative fuel cell during gas purging

The gas purging states affect electricity output and energy storage capacity of unitized regenerative fuel cells. In this study, a model of unitized regenerative fuel cell is established. Cell voltages and operating temperatures influences on the dynamic distribution of thermal fluid during purging process and the discharge of residual liquid water in electrolytic cell mode are investigated. The motivation of the present study is better understanding the gas purging characteristics and its effect on reaction behaviors of unitized regenerative fuel cells. Simulation results reveal a significant influence of purging gas temperature on the water flooding and a great effect of operating voltage on the water diffusion. The operating temperature of electrolytic cell model almost has little effect on purging results at different cell temperature and the same purging gas temperature. When the purging gas temperature is changed, higher temperatures of cell and purging gas facilitate liquid water discharging out from the cell regions. In cell water flooding situation, when having large liquid content, the purging gas has little effects on the water expelling process.     

基于参数预标定的长行程PMLSM无传感器控制

为了解决长行程定子不连续永磁直线同步电机存在的因无法全程安装位置传感器和不同动子和定子之间的电磁参数不固定所造成的控制性能下降的难题,提出一种在每一段定子内先进行参数标定,再进行速度控制的控制系统设计。首先,在动子进入过程中,对电机进行电磁参数标定,根据标定参数对控制器参数进行调整,以达到更好的控制效果。然后,使用无位置传感器控制系统使动子快速达到设定速度值并稳定运行。实验结果表明:动子进入过程参数标定精度分别为0.002Wb和0.000 4H;无位置传感器控制中位置估计精度为0.63mm,速度收敛时间为0.45s,稳态误差为0.02m/s。基本满足永磁直线同步电机用于长行程运输的控制快速性、稳定性等要求。     

A charge sharing–based switching scheme for SAR ADCs

This paper presents an energy-efficient switching scheme for successive approximation register (SAR) analogue-to-digital converter (ADC). The proposed scheme employs charge recycling method to keep the capacitor arrays free of transitional energy between bit generations except reset phase. In comparison with the conventional switching scheme, the proposed one achieves 100% transitional energy saving without considering reset phase. In addition, configuration of a 10-bit SAR ADC shows that the proposed switching scheme reduces the capacitor area by 25% compared with the conventional switching scheme.     

Negative magnetization and exchange bias effect in Fe-doped CoCr2O4

Polycrystalline ceramics of Co(Cr_1-xFe_x)₂O₄ (0?≤?x?≤?0.12) were experimentally studied based on a series of temperature and time-dependent dc magnetic measurements using different magnetic field histories. Magnetization in field cooling process was continuously decreased for doping content x in the range of 0?≤?x?≤?0.04. Remarkable negative magnetization is observed when x reaches to 0.06 and persists up to x?=?0.1. Two-sublattice model is established and competition of the two magnetic sublattices is responsible for the phenomenon. The magnetic switching effect is realized just by changing the magnitude of the applied magnetic field and double magnetocaloric effects are obtained. These unique features under low magnetic fields show attractive for application in spintronic devices due to that the magnetic state can effectively be tuned through magnetic field or temperature. Besides, the system exhibits both positive and negative exchange bias fields which are considered to be originating from the unidirectional anisotropy of exchange coupling of antiferromagnetic/ferromagnetic phases and spin reorientation of the two sublattices magnetic moments, respectively.     

反应釜夹套多介质智能切换控制系统设计

为了解决反应釜夹套内多种介质切换时易因操作失误引起介质混乱的问题,提出了反应釜夹套多介质智能切换控制方案。在生产过程中进行升/降温操作时,程序通过介质标识位自动识别夹套内的当前介质,并通过压空操作时间标准判断夹套压空终点,可以自动完成介质压空及切换等操作。实际应用表明:该方案提高了夹套介质切换的可靠性。     

Effects of Winding Attachment Positions on Output Characteristics of Flux‐Modulating Synchronous Machines

The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power.     

谐振变换器的ZVS软开关同步整流技术研究

以感应电能传输(IPT)谐振变换器为研究对象,研究了谐振变换器的ZVS同步整流(SR)技术。分析了基于SR技术IPT谐振变换器的工作原理,利用系统的谐振工作特性,提出了一种新颖的ZVS软开关SR实现方法。建立了系统频闪映射稳态数学模型,给出了ZVS软开关SR的周期不动点函数、数值求解状态变量及ZVS软开关SR工作周期的算法流程。在设计控制电路的基础上,通过实验验证了提出的同步整流技术的可行性。     

The visual impact of augmented reality during an assembly task

Many studies have shown the benefits of augmented reality (AR) to improve manufacturing and control processes in industry. However, the presentation of AR content through optical see-through head-mounted displays may induce unnatural viewing conditions, which consequences on the user’s visual system have not been investigated yet. This study aimed at assessing whether using AR instructions to guide a manual task, i.e., conditions where the user is forced to repeatedly look at and accommodate in different planes to extract information from both real and virtual environments, could potentially impact the visual system of operators. A before/after design study was carried out, asking 26 participants to perform Lego assemblies for 30 min with either paper or AR instructions. The effects of using AR compared to paper instructions were evaluated both on binocular vision, with classical optometric measurements, and on visual fatigue, with the Virtual Reality Symptoms Questionnaire. No clinically significant differences in optometric measurements (far/near visual acuity, stereoacuity, phoria, convergence, fusional amplitude, accommodation amplitude, accommodative convergence) have been found between AR and paper instructions, and only negligible fatigue symptoms have been seen specifically for AR. Results from both objective and subjective measurements suggest that there is no impact of AR on the oculomotor system and that, in this specific case of use, AR can be safely used for production operators.