Application of differential evolution for cascaded multilevel VSI with harmonics elimination PWM switching

Harmonic elimination pulse width modulation (HEPWM) method has been widely applied to multilevel voltage source inverter (MVSI) to remove low frequency harmonics from its output voltage. However, the computation of the HEPWM switching angles for MVSI is very challenging due to several constraints, namely angle sequencing, very tight angular spacing and the numerous possibilities of angles distribution ratio. Realizing the potential of Differential Evolution (DE) to handle complex problems, this work proposes its application to solve the HEPWM problem for cascaded MVSI. Its emphasis is on improving the availability of HEPWM for higher output voltage by extending the maximum range of modulation index (M). It also removes the discontinuities in the switching angles and reduces the number of distribution ratio required to obtain the required solution. Compared to the most advanced (similar) work, i.e., 7-level MVSI with seventeen switching angles, DE covers a wider range of M; the maximum achievable M is 2.80. Furthermore, it exhibits very low second order distortion factor (DF₂): for the worst case, the value of DF₂ is 0.0014%. To verify the viability of the proposed algorithm, simulation is carried out and hardware prototype is constructed. Both results show very good agreement with the theoretical prediction.     

Metabolism of phospholipids in the yeast Schizosaccharomyces pombe

The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules.     

Effect of Moving Speed of Charged Metallic Spherical Electrode on Electrostatic Discharge

In this investigation, the nature of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary grounded object is experimentally clarified. The spark lengths, discharge currents, and induced voltages in a magnetic probe were measured when a charged metallic spherical electrode connected to a 422 pF capacitor approached a stationary grounded object, which was the current target, for different moving speeds of the charged metallic spherical electrode in a range of 1 mm/s to 100 mm/s. The charge voltages of the capacitor were +6.5 kV and +10 kV. Based on the results, the average gap length shortened with the speed of the spherical electrode. The average peak values of the discharge current and the induced voltage were likely to increase with the speed of the spherical electrode. The average rise times of the discharge current and the induced voltage were likely to drop with the speed of the spherical electrode. The relation between the spark length and the discharge current due to the ESD can be explained qualitatively by using an equation derived from the spark resistance formula proposed by Rompe and Weizel.     

Voltage reference architectures for low-supply-voltage low-power applications

This paper presents a voltage reference generator architecture and two different realizations of it that have been fabricated within a standard 0.18 μm CMOS technology. The architecture takes the advantage of utilizing a sampled-data amplifier (SDA) to optimize the power consumption. The circuits achieve output voltages on the order of 190 mV with temperature coefficients of 43 ppm/°C and 52.5 ppm/°C over the temperature range of 0 to 120°C without any trimming with a 0.8 V single supply. The power consumptions of the circuits are less then 500 nW while occupying an area of 0.2 mm² and 0.08 mm², respectively.     

Reexamination of the Ergothioneine Biosynthetic Methyltransferase EgtD from Mycobacterium tuberculosis as a Protein Kinase Substrate

Ergothioneine has emerged as a crucial cytoprotectant in the pathogenic lifestyle of Mycobacterium tuberculosis. Production of this antioxidant from primary metabolites may be regulated by phosphorylation of Thr213 in the active site of the methyltransferase EgtD. The structure of mycobacterial EgtD suggests that this post-translational modification would require a large-scale change in conformation to make the active-site residue accessible to a protein kinase. In this report, we show that, under in vitro conditions, EgtD is not a substrate of protein kinase PknD.     

Estimation of power density in IMPATT using different materials

ABSTRACT

The RF output power dissipated per unit area is calculated using Runge-Kutta method for the high-moderate-moderate-high (n⁺-n-p-p⁺) doping profile of double drift region (DDR)-based impact avalanche transit time (IMPATT) diode by taking different substrate at Ka band. Those substrates are silicon, gallium arsenide, germanium, wurtzite gallium nitride, indium phosphide and 4H-silicon carbide. A comparative study regarding power dissipation ability by the IMPATT using different material is being presented thereby modelling the DDR IMPATT diode in a one-dimensional structure. The IMPATT based on 4H-SiC element has highest power density in the order of 10¹⁰ Wm^?2 and the Si-based counterpart has lowest power density of order 10⁶ Wm^?2 throughout the Ka band. So, 4H-SiC-based IMPATT should be preferable over others for the power density preference based application. This result will be helpful to estimate the power density of the IMPATT for any doping profile and to select the proper element for the optimum design of the IMPATT as far as power density is concerned in the Ka band. Also, we have focused on variation of power density with different junction temperatures and modelled the heat sink with analysis of thermal resistances.     

浅谈焦炉煤气鼓风机高压变频调速控制系统的设计

本文对焦炉煤气加压控制系统进行了分析，在焦炉煤气加压机控制系统中运用变频调速技术对其进行改造，从而实现煤气加压机运转的自动调节，有效地稳定了焦炉煤气母管压力，保证了安全运行，并且达到节约能源的效果。解决了两台鼓风机并列运行，靠调节回流阀无法实现压力恒定这个始终困扰焦炉生产的难题。     

大气状态下AFM阳极氧化加工Si的研究

Si纳米氧化线是构筑基于Si的纳米器件的基础。通过AFM针尖诱导阳极氧化加工的n型Si(100)的实验得到凸出的n型Si(100)氧化物高度和偏置电压成线性关系,与针尖扫描速度成负对数关系,并在前人的基础上深化了AFM针尖诱导氧化加工的机理和理论模型,得到了合适的加工条件为偏压8 V和扫描速度1μm/s。     

电流叠加型CMOS基准电压源

介绍了一种CMOS基准电压源,该电路由NMOS管阈值电压的温度系数及NMOS管迁移率温度系数形成温度补偿,产生低温度系数的基准电压。与传统的带隙基准比较而言,不需要三极管;另外,通过结构的改进,变成正负温度系数电流叠加型的基准电压源,可以按需要任意调节输出基准电压的值,而且可以同时提供多个基准电压。电流叠加型基准电压源电路已经在3μmCMOS工艺线上实现,基准电压源输出中心值在2.2 V左右,温度系数为80 ppm/℃。     

智能化中高压变频器实载试验平台的实现

中、高压变频器产量越来越多，但试验手段大多比较落后，一般采用带电机空转的方法。本文介绍了一个高压变频器试验平台，通过该平台可以对电压等级在3kV～10kV、功率在5000kW以下的变频器进行实载试验。