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Search Results: 1 - 10 of 27829 matches for " Zhijian Hu "
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Live Line Measuring the Parameters of 220 kV Transmission Lines with Mutual Inductance in Hainan Power Grid  [PDF]
Zhongzhu Xu, Zhijian Hu, Chuanqi Li
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.51B027
Abstract: A live line measurement method for the zero sequence parameters of transmission lines with mutual inductance is introduced. The mathematical models of the measurement method are given. Global Positioning System (GPS) is used as the synchronous signal for the measurement carried out at different substations simultaneously. The measurement system and digital simulation results are given. Finally, the live line measurement results of two 220 kV transmission lines with mutual inductance in Hainangrid are given. Results from both simulation and on-site measurement show that the live line measurement method is feasible, and its measurement accuracy can satisfactorily meet the requirements of engineering measurement.

 

Research on the Three-phase Photovoltaic Grid-connected Control Strategy  [PDF]
Yukai Liu, Zhijian Hu, Ziyong Zhang, Jianglei Suo, Kaibin Liang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B006
Abstract: This paper mainly studies scheduling type photovoltaic generation system, and establishes a three-phase photovoltaic grid-connected model in Matlab/Simulink, which uses the MPPT control that can make full use of the solar energy. At the same time, energy storage device is added. The inverter of the energy storage device adopts V/f control. In the running state of the islanding because of a certain power failure, it can maintain a constant voltage and frequency. The simulation shows that as the output of the photovoltaic power increases, harmonic rate decreases under the same conditions, and the energy storage device can increase the stability of photovoltaic grid and reduce harmonic contents. So it’s very necessary to add energy storage device in the photovoltaic system.
An Integrated Control Strategy Adopting Droop Control with Virtual Inductance in Microgrid  [PDF]
Jianjun Su, Jieyun Zheng, Demin Cui, Xiaobo Li, Zhijian Hu, Chengxue Zhang
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.51B008
Abstract: As there exists sorts of distributed generators in microgrid, an integrated control strategy containing different control methods against corresponding generators should be applied. The strategy in this paper involves PQ control and droop control methods. The former aims at letting generators like PV output maximum power. The latter stems from inverter parallel technique and applies to controlling generators which can keep the network voltage steady to make the parallel system reach the minimum circulation point. Due to the unworthiness of droop control applied in low-voltage microgrid of which the impedance ratio is rather high, the paper adopts the droop control introducing virtual generator and virtual impedance. Based on theoretical analysis, simulation in Matlab is also implemented to verify the feasibility of the strategy.
Wide-Area Delay-Dependent Adaptive Supervisory Control of Multi-machine Power System Based on Improve Free Weighting Matrix Approach  [PDF]
Ziyong Zhang, Zhijian Hu, Yukai Liu, Yang Gao, He Wang, Jianglei Suo
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B084
Abstract:

The paper demonstrates the possibility to enhance the damping of inter-area oscillations using Wide Area Measurement (WAM) based adaptive supervisory controller (ASC) which considers the wide-area signal transmission delays. The paper uses an LMI-based iterative nonlinear optimization algorithm to establish a method of designing state-feedback controllers for power systems with a time-varying delay. This method is based on the delay-dependent stabilization conditions obtained by the improved free weighting matrix (IFWM) approach. In the stabilization conditions, the upper bound of feedback signal’s transmission delays is taken into consideration. Combining theoriesof state feedback control and state observer, the ASC is designed and time-delay output feedback robust controller is realized for power system. The ASC uses the input information from Phase Measurement Units (PMUs) in the system and dispatches supplementary control signals to the available local controllers. The design of the ASC is explained in detail and its performance validated by time domain simulations on a New England test power system (NETPS).

Simulation on Calculation Accuracy of Three Methods for Live Line Measuring the Parameters of Transmission Lines with Mutual Inductance  [PDF]
Jianjun Su, Ronghua Zhang, Demin Cui, Yongqiang Chai, Xiaobo Li, Chengxue Zhang, Peiyan Li, Zhijian Hu, Yingying Hu
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B272
Abstract:

Live line measurement methods can reduce the loss of power outages and eliminate interference. There are three live line measurement methods including integral method, differential method and algebraic method. A simulation model of two coupled parallel transmission lines spanning on the same towers is built in PSCAD and the calculation errors of these three methods are compared with different sampling frequencies by using of Matlab. The effect of harmonic on calculation is also involved. The simulation results indicate that harmonic has the least effect on the algebraic method which provides stable result and small error.

New Method of Measuring the Positive-sequence Capacitance of T-connection Transmission Lines  [PDF]
Yuansen Zhang, Demin Cui, Qingtao Cao, Yongqiang Chai, Peng Liu, Xiaobo Li, Zhijian Hu, Chuanqi Li, Chengxue Zhang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B180
Abstract:

A novel method of measuring the positive-sequence capacitance of T-connection transmission lines is proposed. The mathematical model of the new method is explained in detail. In order to obtain enough independent equations, three independent operation modes of T-connection transmission lines during the line measurement are introduced. The digital simulation results and field measurement results are shown. The simulation and measurement results have validated that the new method can meet the needs of measuring the positive-sequence capacitance of T-connection transmission lines. This method has been implemented in the newly developed measurement instrument.

Identification of Early Zygotic Genes in the Yellow Fever Mosquito Aedes aegypti and Discovery of a Motif Involved in Early Zygotic Genome Activation
James K. Biedler, Wanqi Hu, Hongseok Tae, Zhijian Tu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033933
Abstract: During early embryogenesis the zygotic genome is transcriptionally silent and all mRNAs present are of maternal origin. The maternal-zygotic transition marks the time over which embryogenesis changes its dependence from maternal RNAs to zygotically transcribed RNAs. Here we present the first systematic investigation of early zygotic genes (EZGs) in a mosquito species and focus on genes involved in the onset of transcription during 2–4 hr. We used transcriptome sequencing to identify the “pure” (without maternal expression) EZGs by analyzing transcripts from four embryonic time ranges of 0–2, 2–4, 4–8, and 8–12 hr, which includes the time of cellular blastoderm formation and up to the start of gastrulation. Blast of 16,789 annotated transcripts vs. the transcriptome reads revealed evidence for 63 (P<0.001) and 143 (P<0.05) nonmaternally derived transcripts having a significant increase in expression at 2–4 hr. One third of the 63 EZG transcripts do not have predicted introns compared to 10% of all Ae. aegypti genes. We have confirmed by RT-PCR that zygotic transcription starts as early as 2–3 hours. A degenerate motif VBRGGTA was found to be overrepresented in the upstream sequences of the identified EZGs using a motif identification software called SCOPE. We find evidence for homology between this motif and the TAGteam motif found in Drosophila that has been implicated in EZG activation. A 38 bp sequence in the proximal upstream sequence of a kinesin light chain EZG (KLC2.1) contains two copies of the mosquito motif. This sequence was shown to support EZG transcription by luciferase reporter assays performed on injected early embryos, and confers early zygotic activity to a heterologous promoter from a divergent mosquito species. The results of these studies are consistent with the model of early zygotic genome activation via transcriptional activators, similar to what has been found recently in Drosophila.
Primary hepatic carcinoid tumor
Jinbo Gao, Zhijian Hu, Junwei Wu, Lishan Bai, Xinqun Chai
World Journal of Surgical Oncology , 2011, DOI: 10.1186/1477-7819-9-151
Abstract: Carcinoid tumors are neoplasms that originate from the cells of neuroendocrine system, and were first characterized by Oberndorfer in 1907. They are usually low-grade malignant tumors that may cause the carcinoid syndrome by secretion of serotonin and other vasoactive hormones. Most of them occur within the gastrointestinal tract, primarily in the appendix and the terminal ileum [1,2]. Primary hepatic carcinoid tumors (PHCT) are very rare. Here, we report a case of PHCT, and describe the clinical features and treatment of this case.A 53-year-old female presented with right upper quadrant abdominal pain and was admitted to our hospital in May 2007. The patient had no history of jaundice, vomiting, flushing or diarrhea. Her past medical history included hypertension and a cholecystectomy due to gallstones 10 years previously. Physical examination showed no abnormality except for the presence of a scar in the right upper quadrant of abdomen. Laboratory investigations, including liver function test, renal function test, blood routine test and tumor markers (AFP, CEA, CA19-9, CA242, CA125 and CA15-3), were within normal limits. Serum hepatitis B surface antigen and hepatitis C antibody were negative.Computer tomography (CT) revealed a low density nodule in segment 4 of liver. Dynamic CT scans showed enhanced of the nodule in the arterial phase and early washout in the portal phase (Figure 1). Liver ultrasound confirmed the presence of the hypervascular mass. No enlarged lymph nodes were found by CT or ultrasonic. Based on the imaging finding, hepatocelluar carcinoma was highly suspected. A fine-needle aspiration biopsy was performed under ultrasonographic guidance for definite diagnosis. The histological examination of the biopsy specimens suggested the tumor was a carcinoid tumor. The neoplastic cells were round or columnar cells with round nuclei and pale eosinophilic cytoplasm. Immunohistochemistry was positive for pancytokeratin AE1/AE3, synaptophysin and chromorgran
An Optical Carry Chain Fast Adder
Zhijian Hu,G. King,D. Al-Dabass
Radioengineering , 1994,
Abstract: A significant problem in Arithmetic Unit design and particularly for systolic arrays remains the speed attainable in achieving high speed addition. The root of the problem is carry propagation and a method is presented which is relatively independent of word length. The problem is addressed by the description of a suggested radical design involving a hybrid optical and electronic approach. The method of carry chain addition through pass gates is explained and a suggested implementation utilising Fabry-Perott resonators, optical waveguides and voltage controlled couplers is described. The design is suitable for n-stage modular expansion.
Internetware Structure Description and Research of the Petri Net Method
Zhijian Wang,Yuping Hu,Shaohua Li,Dingguo Wei
Journal of Software , 2011, DOI: 10.4304/jsw.6.9.1779-1786
Abstract: Architecture design and specification is more important than algorithm or data structure establishment for a complex system, existing Architecture Description Languages are difficult to support the complete Internetware developing process. Petri nets describe system graphically and mathematically, provide a way to solve the problems in Internetware description and development. In this paper we investigate Internetware architecture description methods, current application of Petri nets in Internetware and the deficiency; present basic principles to describe Internetware architecture using Petri nets, the possible architecture model and architecture evolution mechanisms; discuss subnet based Web services composition description technologies; present the idea of developing Internetware using Petri nets as a whole process unified model. The Petri net method helps to transfer among different stages of Internetware developing easily; the smooth transition from architecture description to code implementation makes sure a good design can deduce a good realization.
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