Influence of Water Molecules on Polarization Behavior and Time–Frequency Dielectric Properties of Cellulose Insulation

Wen Hao,Cheng Lin,Jiang Yi,Zhu Taiyun,Chen Zhong,Dai Xize,Gao Chenyu 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.3

Oil-immersed power transformer plays an important role in power transmission and transformation engineering. Moisture is one of the important factors to determine its insulation performance. Molecular simulation technique is used to study the mechanism of water molecules on the micro polarization behavior of cellulose insulation materials. The number of hydrogen bonds, solubility parameters, total dipole moment and polarizability are analyzed. These characteristics explain the action mechanism of water molecules on cellulose insulation. At the same time, the time domain and frequency dielectric response of cellulose insulation materials with diff erent moisture content are explored. The dielectric modulus spectrum is introduced to replace the traditional frequency dielectric spectroscopy to characterize the micro relaxation process of cellulose insulation under diff erent moisture content. Finally, the characteristic parameters are extracted from the polarization, depolarization current and dielectric modulus spectrum curves to evaluate the moisture content of cellulose insulation materials. The results show that the number of hydrogen bonds, binding energy density, solubility parameter, total dipole moment and polarizability increase with the increase of water content. It should be noted that dielectric modulus spectroscopy can eff ectively characterize the relaxation behavior of cellulose insulation materials. The moisture content of cellulose insulation can be quantitatively evaluated by DC conductivity, insulation resistance, imaginary part relaxation peak of dielectric modulus and integral value of real part and imaginary part of dielectric modulus.

Dynamic Function Allocation Method for Aircraft Cockpit Based on Operator Functional State

Wen-hao Bi,An Zhang,Shui-da Bao 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10

Dynamic function allocation for aircraft cockpit benefits the complementary between operators and automation and the whole system performance. We selected two important physiological parameters HRV2 and TLI2, which have great influences on the operator functional state (OFS) and took their measurements as a trigger mechanism for dynamic function allocation of the cockpit system. After that, we utilized fuzzy logic to put forward a dynamic adjustment methodology for the levels of automation and used MATLAB to verify the utility of the method.

Setting Considerations of Distance Relay for Transmission Line with STATCOM

Wen-Hao Zhang,Seung-Jae Lee,Myeon-Song Choi 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.4

Distance relay plays an important role in the protection of transmission lines. The application of flexible AC transmission systems (FACTS) devices, such as the static synchronous compensator (STATCOM), could affect the performance of the distance relay because of compensation effect. This paper analyzes the application of distance relay on the protection of a transmission line containing STATCOM. New setting principles for different protection zones are proposed based on this analysis. A typical 500 kV transmission system employing STATCOM is modeled using Matlab/Simulink. The impact of STATCOM on distance protection scheme is studied for different fault types, fault locations, and system configurations. Based on simulation results, the performance of distance relay is evaluated. The setting principle can be verified for the transmission line with STATCOM.

A Probabilistic Approach to the Protection Capability Evaluation of Distance Relay in Transmission Systems

Wen-Hao Zhang,Seung-Jae Lee,Myeon-Song Choi 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.3

This paper proposes a probability measure for the evaluation of relay performance from two aspects, namely, correct trip and no-unwanted trip. They are developed based on the relationship between relay settings and relay measurements, which follow a Gaussian probability model. The proposed method based on strict mathematical derivation is applied to protection capability evaluation of distance relays under various settings. Considering the specific attributes of each protection zone, the optimal settings are also determined accordingly. The protection capability could demonstrate clearly the relay performance under various settings and the optimal settings could provide good references for engineering applications.

Exploring GPU Data Cache Leakage Management Techniques

Hao Wen,Wei Zhang 한국정보과학회 2018 Journal of Computing Science and Engineering Vol.12 No.3

In this paper, we study how to reduce cache leakage energy efficiently for GPU data caches (L1 and L2). The access pattern of GPU cache is different from that of the CPU, which usually has little locality and high miss rate. In addition, GPU can hide memory latency more effectively due to multi-threading. Because of the above reasons, we find it is possible to place cache lines of GPU data caches into the low power mode more aggressively than traditional leakage management for CPU caches that can reduce more energy leakage without significant performance degradation. In some cases, we find it is possible for the GPU to bypass the L1 data cache to save 100% energy leakage while generating better performance. Also, we propose to combine the drowsy and gated-VDD techniques that can exploit short and long access intervals to minimize energy leakage with insignificant performance overhead. Interestingly, we may achieve better performance for some benchmarks due to the different cache access patterns after applying the leakage reduction method.

User-intervened structured meshing methods and applications for complex flow fields based on multiblock partitioning

Wen-Hao Cai,Jie-Min Zhan,Ying-Ying Luo 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.1

Recently, a series of automatic structured grid generation methods for different fields or specific problems have been proposed by various researchers, but these methods still have some disadvantages or limitations. Therefore, in the present study, several user-intervened structured meshing methods for complex flow fields have been introduced for multiblock docking and multiblock splicing based on multiblock structured grid technology. Besides, three applications compared with the other methods or experiments are discussed to illustrate the crucial workflow of the user-intervened partitioning. The successful implementation of these partitioning examples demonstrates the feasibility and effectiveness of the methods described herein. And the techniques and criteria summarized in the present paper are quite practical and helpful for high-quality meshing.

A Robust Fault Location Algorithm for Single Line-to-ground Fault in Double-circuit Transmission Systems

Wen-Hao Zhang,Umar Rosadi,Myeon-Song Choi,Seung-Jae Lee,Ilhyung Lim 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.1

This paper proposes an enhanced noise robust algorithm for fault location on double-circuit transmission line for the case of single line-to-ground (SLG) fault, which uses distributed parameter line model that also considers the mutual coupling effect. The proposed algorithm requires the voltages and currents from single-terminal data only and does not require adjacent circuit current data. The fault distance can be simply determined by solving a second-order polynomial equation, which is achieved directly through the analysis of the circuit. The algorithm, which employs the faulted phase network and zero-sequence network with source impedance involved, effectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The proposed algorithm is tested using MATLAB/Simulink under different fault locations and shows high accuracy. The uncertainty of source impedance and the measurement errors are also included in the simulation and shows that the algorithm has high robustness.

A Probabilistic Method Based Protectability Evaluation of Distance Relay in Transmission Networks

Wen-Hao Zhang,Myeon-Song Choi,Seung-Jae Lee,Il-Hyung Lim,Seong-Jeong Rim 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.3

This paper defines the concept of "protectability" for the performance evaluation of distance relay considering its sensitivity and selectivity. The paper starts from the probabilistic modeling of the errors, and based on this model, a detailed explanation of protectability calculation for each zone of the distance relay is presented. An effect of the Weighting Rate and the Measurement Deviation on the protectability evaluation is also given. By considering this effect, the optimization of relay setting can be realized. The proposed method is applied to a typical model system to show its effectiveness

Genomic Screening for Targets Regulated by Berberine in Breast Cancer Cells

Wen, Chun-Jie,Wu, Lan-Xiang,Fu, Li-Juan,Yu, Jing,Zhang, Yi-Wen,Zhang, Xue,Zhou, Hong-Hao Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.10

Berberine, a common isoquinoline alkaloid, has been shown to possess anti-cancer activities. However, the underlying molecular mechanisms are still not completely understood. In the current study, we investigated the effects of berberine on cell growth, colony formation, cell cycle distribution, and whether it improved the anticancer efficiency of cisplatin and doxorubicin in human breast cancer estrogen receptor positive (ER+) MCF-7 cells and estrogen receptor negative (ER-) MDA-MB-231 cells. Notably, berberine treatment significantly inhibited cell growth and colony formation in the two cell lines, berberine in combination with cisplatin exerting synergistic growth inhibitory effects. Accompanied by decreased growth, berberine induced G1 phase arrest in MCF-7 but not MDA-MB-231 cells. To provide a more detailed understanding of the mechanisms of action of berberine, we performed genome-wide expression profiling of berberine-treated cells using cDNA microarrays. This revealed that there were 3,397 and 2,706 genes regulated by berberine in MCF-7 and MDA-MB-231 cells, respectively. Fene oncology (GO) analysis identified that many of the target genes were involved in regulation of the cell cycle, cell migration, apoptosis, and drug responses. To confirm the microarray data, qPCR analysis was conducted for 10 selected genes based on previously reported associations with breast cancer and GO analysis. In conclusion, berberine exhibits inhibitory effects on breast cancer cells proliferation, which is likely mediated by alteration of gene expression profiles.

Preferential Induction of CYP1A1 over CYP1B1 in Human Breast Cancer MCF-7 Cells after Exposure to Berberine

Wen, Chun-Jie,Wu, Lan-Xiang,Fu, Li-Juan,Shen, Dong-Ya,Zhang, Xue,Zhang, Yi-Wen,Yu, Jing,Zhou, Hong-Hao Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.1

Estrogens are considered the major breast cancer risk factor, and the carcinogenic potential of estrogens might be attributed to DNA modification caused by derivatives formed during metabolism. $17{\beta}$-estradiol ($E_2$), the main steroidal estrogen present in women, is metabolized via two major pathways: formation of 2-hydroxyestradiol (2-OH $E_2$) and 4-hydroxyestradiol ($4-OH\;E_2$) through the action of cytochrome P450 (CYP) 1A1 and 1B1, respectively. Previous reports suggested that $2-OH\;E_2$ has putative protective effects, while $4-OH\;E_2$ is genotoxic and has potent carcinogenic activity. Thus, the ratio of $2-OH\;E_2/4-OH\;E_2$ is a critical determinant of the toxicity of $E_2$ in mammary cells. In the present study, we investigated the effects of berberine on the expression profile of the estrogen metabolizing enzymes CYP1A1 and CYP1B1 in breast cancer MCF-7 cells. Berberine treatment produced significant induction of both forms at the level of mRNA expression, but with increased doses produced 16~ to 52~fold greater induction of CYP1A1 mRNA over CYP1B1 mRNA. Furthermore, berberine dramatically increased CYP1A1 protein levels but did not influence CYP1B1 protein levels in MCF-7 cells. In conclusion, we present the first report to show that berberine may provide protection against breast cancer by altering the ratio of CYP1A1/CYP1B1, could redirect $E_2$ metabolism in a more protective pathway in breast cancer MCF-7 cells.