N-enriched porous carbon doped with co,ni, and Mo as efficient electrocatalyst for hydrogen evolution reaction

Splitting water for hydrogen production is still a promising technique to meet the energy requirements of society and overcome many environmental problems. However, the development of carbon-based transition electrocatalysts with superior activity for hydrogen evolution reaction (HER) is still challenging. In this study, a CoNiMo/NPC electrocatalyst was successfully fabricated using ZIF-67 as a precursor via facile absorption, pyrolysis and annealing processes. The fabricated CoNiMo/NPC was used as an electrocatalyst for hydrogen production. The results revealed that the doping of Ni and Mo increase the number of active sites and enhance the conductivity of electrocatalysts. CoNiMo/NPC exhibits excellent HER activity in alkaline solutions and only requires an overpotential of 182 mV to reach a current density of 10 mA/cm². Furthermore, long-term measurements demonstrated that CoNiMo/NPC has superior durability in alkaline solutions. The excellent HER performance of CoNiMo/NPC can be attributed to the doping of Co, Ni, and Mo on porous carbon. In addition, the high specific surface area and high graphitisation degree of the electrocatalyst are beneficial for rapid charge transport and collection.     

Power conversion system for high altitude wind power generation with medium voltage AC transmission

High Altitude Wind Power (HAWP) generating system provides clean energy at low cost and high capacity factor due to reduced size of the turbine and high speed streamlined wind at high altitude. An air-borne wind turbine (AWT) at high altitude extracts kinetic energy from wind using buoyancy provided by the blimp/aerostat. The generated electrical power is then transmitted to the ground based station (without any power conditioning) using the transmission lines (tether). The power conversion system (PCS) for harnessing HAWP is proposed in this paper. The proposed PCS consists of a three-level neutral point clamped (NPC) rectifier, a three-level NPC DC–DC converter followed by a two-level inverter. Modelling, design and control of the PCS are presented and discussed. The PCS provides generation side maximum power-point tracking (MPPT) using sensorless optimal torque control technique. The DC–DC converter provides electrical isolation as well as voltage step-down functions. A modified proportional resonant (PR) control which can selectively eliminate lower order current harmonics of the grid-connected inverter is also presented. The proposed control scheme of the PCS is evaluated through simulation studies using software programs like PSIM and MATLAB. A scaled-down 1 kW laboratory prototype of the complete PCS is designed, built and tested. The experimental test results obtained validate the proposed control scheme for efficient power generation from high altitude wind and interface to the grid/load.     

EB病毒膜潜伏蛋白LMP-1筛选鼻咽癌的初步结果

Objective: Early diagnosis of nasopharyngeal carcinoma (NPC) is an important method to improve the survival rate. However, the sensitivity and specificity of the screening protocols which was widely used in clinic now are considered to be unsatisfactory. Epstein-Barr virus (EBV)-encoded latent membrane protein-1 (LMP-1)is one of the proteins that have been suggested to be a classic oncogene with transformation properties. The current study set out to discuss the clinical significance of LMP-1 on the screening of NPC. Methods: Three hundred patients who visited our institution (Department of Radiation Oncology, Fujian Provincial Cancer Hospital, Fuzhou,China) with ENT symptoms between 2007 and 2008 were involved in this study, and all of them were agreed to be involved in this investigation. Not only did they undergo nasopharyngeal swab to obtain cells for the LMP-1 polymerase chain reaction (PCR) analysis, but also nasopharyngeal biopsy were taken to identify the diagnosis. Results: An amount of DNA that was sufficient for PCR was extracted from 243 (81%) swab samples, the positive rate of LMP-1 of those with non-nasopharyngeal carcinoma was 3.85% (4/108), which was much lower than those with nasopharyngeal carcinoma (P ＜ 0.05). By detecting LMP-1 in nasopharyngeal swabs, NPC was diagnosed with a sensitivity of 88.15% (119 of 135 patients), specificity of 96.30%(104 of 108 patients), a positive predictive value of 95.2% (119 of 123 patients), a negative predictive value of 86.67% (104of 120 patients), accuracy of 91.77%, and Youden index of 84.45%. Conclusion: The nasopharyngeal swab coupled with PCR-based EBV LMP-1 detection have high sensitivity and specificity, and also good repeatability, it could serve as part of the screening program for high-risk populations.     

A circulating current control scheme for multiple three‐level NPC inverter systems

In recent years, motor drive systems for steel rolling mills have been steadily increasing in capacity. In particular, the development of three‐level NPC (Neutral Point Clamped) inverters is now focusing on the replacement of cycloconverters. In order to satisfy such a requirement, in this paper a multiple three‐level NPC inverter system is proposed. The configuration consists of two three‐level NPC inverters with the same configuration connected in parallel by current limiting reactors. In this case, the circulating current flowing between the two three‐level NPC inverters must be controlled to prevent a decrease in the maximum output capacity. In particular, a new method for control of the circulating current is a major topic of discussion. The method is based on space voltage vector‐based PWM (Pulse Width Modulation) control for the three‐level NPC inverters and the circulating current is controlled by adjusting the output durations of the respective space voltage vectors. In this method the circulating current controller can be decoupled from the motor current controller. Therefore, it is possible to design the different controllers independently. In addition, the experimental results obtained using an induction motor show that the circulating current can be reduced to within 2% of the rated motor current when the motor current response exceeds 1000 rad/s. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 38–48, 2001     

三电平逆变器直接转矩控制仿真分析

对三电平逆变器直接转矩控制的基本原理,拓扑结构,控制原理,及控制策略进行了详细的分析,给出了一种结合三电平特性的异步电机数学模型,通过仿真验证了建立在该模型下的中点钳位式三电平逆变器直接转矩控制的良好动静态特性.     

FPS游戏中基于HTN的Anytime规划器的研究

动态性和实时性电脑游戏世界的两个关键特征。Anytime规划是能够产生满足上述两个特征的行为的规划方法。分层任务网络（Hierarchical Task Network,HTN）是表示分层规划的一种形式,它非常适合于表达电脑游戏中非玩家角色（non-player character,NPC）复杂的目标。以著名的第一人称射击（First-Person Shooter,FPS）游戏虚幻竞技场2004（Unreal Tournament 2004）作为游戏平台,为NPC设计实现了一个基于HTN规划的anytime规划器,并使用遗传算法调整规划目标的优先级。该规划器可以根据环境变化随时中断规划并给出可用的规划结果,同时具有一定的适应性。实验表明它能够使NPC的行为更智能。     

NPC逆变器特定谐波组消除法

针对传统特定谐波消除脉宽调制(SHEPWM)中所得触发角与调制比的非线性关系以及非线性超越方程组的困难求解,指出了SHEPWM中非线性超越方程组解的几何意义.基于此,设计了基于脉宽的谐波消除方法,仅需引入一个变量便可对任一次及其整数倍次的一组谐波进行消除.以5次组谐波和3次谐波消除为例,介绍了该方法在多个谐波消除中的应...     

三电平变流器的压频转换式中点电位平衡控制方法研究

将三电平变流器运用于中高压游粱式抽油机,不仅可以节能降耗而且还可提高油井的采收率。然而,中点箝位式三电平变流器（NPc）的直流侧电压平衡问题直接影响变流器及其电机调速系统的可靠性。本文分析了其原因并提出压频转换式中点电位平衡控制的一种新方法,给出了利用87C196MC单片机实现的具体编程思路,通过软件仿真和实物实验证明了这种方法的正确性。     

新型简易单相五级逆变器

探讨了将中点箝位三级逆变器的一桥臂用于单相逆变桥,来作简易单相五级逆变器用,改善输出电压波形。其特点是元器件用量少、成本低、可靠性高。经Matlab/simulink仿真实验证明,设计方案是可行的。     

NPC三电平逆变器混杂建模及开路故障诊断

由逆变器、滤波器、负载和控制器等组成的逆变系统可视为一个混杂系统,传统的建模方法不能有效地揭示系统的状态特性,影响逆变器功率管故障分析和诊断的准确性。文中介绍了一种基于混合逻辑动态模型的NPC三电平逆变器故障诊断方法。分析了NPC三电平逆变器的工作原理,在混杂系统理论和建模方法基础上,构造逆变系统在无故障时的状态估计器。比较功率管发生单管开路故障时逆变器输出的三相电流真实值和状态估计器输出的三相电流估计值得到残差方程,通过对残差方程表现特性进行分析实现故障诊断。设计了相应的仿真实验,实验结果表明,文中方法可以准确快速地诊断单管开路故障,验证了所述方法的可行性。