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OSCILLATION OF SUB LINEAR DIFFERENCE EQUATIONS WITH POSITIVE NEUTRAL TERM
LI, QIAOLUAN,WANG, CHUNGIAO,LI, FANG,LIANG, HAIYAN,ZHANG, ZHENGUO 한국전산응용수학회 2006 Journal of applied mathematics & informatics Vol.20 No.1
In this paper, we consider the oscillation of first order sublinear difference equation with positive neutral term $\Delta(\chi(n)+p(n)\chi(\tau(n)))+f(n,\chi(g1(n)),\cdots,\chi(gm(n)))=0$. We obtain necessary and sufficient conditions for the solutions of this equation to be oscillatory.
Power Closed-loop Control of Switched Reluctance Generator for High Efficiency Operation
Li, Zhenguo,Gao, Dongdong,Ahn, Jin-Woo Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.3
This paper describes a control method of turn-on/off angles to improve the efficiency of the switched reluctance generator(SRG) with a power closed-loop control system, and the inner-loop of the system is current hysteresis control. The SRG control system is constituted by the PI power controller and the two-level current hysteresis controller. By measuring and analyzing the system losses of different reference powers, speeds and turn-on/off angles, selection strategy of optimal turn-on/off angles is discussed. The proposed method is simple, reliable, and easy to achieve.
Torque Ripple Minimization in Direct Torque Control of Brushless DC Motor
Zhenguo Li,Songfa Zhang,Shenghai Zhou,Jin-Woo Ahn 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
This paper mainly proposes a direct torque control strategy to minimize torque ripple in brushless DC (BLDC) motor. BLDC motor has large current and torque ripple when one voltage vector applied in one cycle due to its low inductance. Hence, this paper proposed a hysteresis torque control with PWM mode to control the resultant torque. Moreover, when the direct torque control system is operating during the two-phase half-bridge 120° conduction mode, large torque ripple in commutation area appears every 120 electrical degree. Based on analyzing the root of torque ripple in detail, lookup tables of switching devices states for new half-bridge modulation mode in the positive and negative reference torque put forwarded. Finally, simulations by MATLAB software and experiment results from DSP are presented to verify the feasibility and effectiveness of the proposed strategy operating in four-quadrant operation.
A Sensorless Switched Reluctance Drive System Based on the Improved Simplified Flux Method
Li, Zhenguo,Song, Andong,Ahn, Jin-Woo Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.4
This paper describes a new rotor position sensorless control method for SRM drives based on an improved simplified flux linkage method. In the traditional simplified flux linkage method, every phases take turns conduction and current chopping control method is used. Every phases take turns conduction means turning on the incoming working phase while turning off the working phase. This conduction mode causes coupling between turn-on and turn-off angles, which goes against optimal efficiency or torque ripple minimization with sensorless speed control. In the improved simplified flux linkage method, turn-off angle is calculated by flux loop, the turn-on angle can be given arbitrarily and has no relations with the turn-off angle, and the current chopping control method is used. The speed and rotor position can be estimated then. Finally, a sensorless SRM speed control system and an experiment platform with DSP are built and validity of this method is confirmed.
Torque Ripple Minimization in Direct Torque Control of Brushless DC Motor
Li, Zhenguo,Zhang, Songfa,Zhou, Shenghai,Ahn, Jin-Woo The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
This paper mainly proposes a direct torque control strategy to minimize torque ripple in brushless DC (BLDC) motor. BLDC motor has large current and torque ripple when one voltage vector applied in one cycle due to its low inductance. Hence, this paper proposed a hysteresis torque control with PWM mode to control the resultant torque. Moreover, when the direct torque control system is operating during the two-phase half-bridge $120^{\circ}$ conduction mode, large torque ripple in commutation area appears every 120 electrical degree. Based on analyzing the root of torque ripple in detail, lookup tables of switching devices states for new half-bridge modulation mode in the positive and negative reference torque put forwarded. Finally, simulations by MATLAB software and experiment results from DSP are presented to verify the feasibility and effectiveness of the proposed strategy operating in four-quadrant operation.
High-efficiency Operation of Switched Reluctance Generator based on Current Waveform Control
Li, Zhenguo,Yu, Siyang,Ahn, Jin-Woo Journal of International Conference on Electrical 2013 Journal of international Conference on Electrical Vol.2 No.1
The main aim of this paper is to expound high-efficiency operation of Switched Reluctance Generator (SRG) based on the current waveform. For this purpose, theoretical analysis of the copper loss and iron loss of the system is done first. Then, necessary simulation is done to find the variation trend of the copper loss and iron loss with the variation of the current waveform at the same output power. Finally, the best current waveform which can make the system operate with high efficiency is obtained by considering the influence of these two kinds of loss. In order to verity the simulation results, the experimental platform of DC motor-SRG is built and the modified angle position control (APC) method which can specify the current shape optionally is presented. By comparing the system efficiency at the three kinds of typical current waveform, the correctness and feasibility of the theory is verified. The proposed method is simple, reliable, and easy to achieve.
Zhenguo Zhang,Houhun Li 한국응용곤충학회 2017 Journal of Asia-Pacific Entomology Vol.20 No.3
The biology and immature stages of Epicephaha assamica Li (Lepidoptera: Gracilariidae) were investigated firstly based on the field observations and laboratory experiments, E. assamica pollinate for Glochidion assamicum (Muell. Arg.) Hook. (Phyllanthaceae) and then lay eggs in pollinated female flowers. In turn, hosts partly sacrifice seeds for larval growth and keeping some seeds for breeding, thus they form the most strictly integrated one-to-one nursery pollination mutualism. E. assamica have two generations correspondingly which are closely consistent with flowering phenology of G. assamicum, peak in March–April and September–October respectively. We investigated the benefits that each species obtains from partner. For G. assamicum, the ripening rate is 51.14%, the rate of consumed fruits is 79.52%, the average number of seeds consumed by each larva is 2.62, and the proportion of intact seeds is 68.03% that could keep the stabilization of mutualism in each population. The study first reports sex ratio in the genus Epicephala and suggests that the male-biased offspring in E. assamica can make sure that female moths have more mating opportunities. The eruciform larva bears three pairs of thoracic legs and four pairs of prolegs on abdominal segments III–V and X (caudal proleg), 11 crochets uniserial arranged in proleg. Antenne exceeds segment X in pupa. The study helps to further understand the evolutionary mechanism and driving force of coevolution in the obligate pollination mutualism between Epicephala and Glochidion.
Development of a Directly Self-adaptive Robot Hand with Pulley-belt Mechanism
Guoxuan Li,Bowen Li,Jie Sun,Wenzeng Zhang,Zhenguo Sun,Qiang Chen 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
Directly self-adaptive under-actuated (DSUA) hands have great potential to stably grasp different objects in unstructured environments. This paper develops a DSUA Hand based on multi-pulley-belt mechanism, which consists of 5 fingers and has 14 DOF. Self-adaptation is designed as the main function of it. The stability of DSUA hand’s grasping process does not highly depend on control algorithm, sensors or control system. This DSUA fingers are based on multi-pulley-belt mechanism. A mathematical model of the 3-joint finger’s contact force is given. Contact force analyses of the DSUA finger are discussed in detail. DSUA Hand weighs 0.94 kg and can grasp objects up to 0.6 kg. The grasping adaptation of DSUA hand is certified by grasping experiments of different objects.
Cheng, Peng,Cheng, You,Li, Yan,Zhao, Zhenguo,Gao, Hui,Li, Dong,Li, Hua,Zhang, Tao Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.8
Lung cancer seriously threatens human health, so it is important to investigate gene expression changes in affected individuals in comparison with healthy people. Here we compared the gene expression profiles between smokers with and without lung cancer. We found that the majority of the expressed genes (threshold was set as 0.1 RPKM) were the same in the two samples, with a small portion of the remainder being unique to smokers with and without lung cancer. Expression distribution patterns showed that most of the genes in smokers with and without lung cancer are expressed at low or moderate levels. We also found that the expression levels of the genes in smokers with lung cancer were lower than in smokers without lung cancer in general. Then we detected 27 differentially expressed genes in smokers with versus without lung cancer, and these differentially expressed genes were foudn to be involved in diverse processes. Our study provided detail expression profiles and expression changes between smokers with and without lung cancer.