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North China Electric Power University is a university based in Beijing, People's Republic of China under the national Ministry of Education that specializes in polytechnic disciplines. Wikipedia.


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Cheng X.,North China Electrical Power University | Li T.,North China Electrical Power University
Proceedings of 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference, IMCEC 2016 | Year: 2016

The requirement of the credibility is analyzed for smart grid data and the traditional theories of data measurement and bad data identification are studied in power system. On the basis of that, this paper mainly studies the credibility between data sources, the construction of the trusted network generation algorithm, and the hierarchical and dynamic trusted network model innovatively which is based on the relationship between data sources. The credibility evaluation of data sources, the credibility evaluation between data sources and the credibility evaluation of data are studied. The credibility between data sources is restricted by the credibility of data sources, the credibility of data sources is restricted both from the credibility of data and the credibility between data sources, the credibility of data is restricted by the credibility between data sources and the credibility of data sources, they are interrelated and restricted by each other and constitute to a whole. The simulation results show that the model can satisfy the requirement of the credibility of smart grid data better, and provide the ideas to solve the problem of the credibility measure for prospective research is feasible. © 2016 IEEE.


Bai Z.-W.,North China Electrical Power University | Hu M.,North China Electrical Power University
Physica A: Statistical Mechanics and its Applications | Year: 2017

Motivated by that the quartic potential can confined Lévy flights, we investigate the escape rate of an inertial Lévy particle from a truncated quartic potential well via Langevin simulation. The escape rate still depends on the noise intensity in a power-law form in low noise intensity, but the exponent and the inverse coefficient vary significantly for different Lévy indexes compared with previous works. Trimodal structure of the probability density function was found in simulations. The probability density function in a quasi-stable state exhibits transition among unimodal, bimodal, and trimodal structures. A metastable state by stable state approach is developed to calculate the escape rate analytically, which may be applied to extensive escape problems. The theoretical approach is confirmed by Langevin simulation for the Cauchy case of Lévy flight in the applied potential. © 2017 Elsevier B.V.


Ye X.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Li C.,North China Electrical Power University
Energy | Year: 2017

The effect of five blade tip patterns on performance and acoustics of a twin-stage variable-pitch axial fan is investigated numerically. The best tip pattern is determined by comparing the overall performance under the condition of those patterns carving in stage I impeller, and the performance promotion is then examined under the selected tip grooving in stage I impeller, stage II impeller and both two stage impellers. Finally, flow dynamics and acoustic noise are explored. The results show that all proposed tip patterns can improve fan performance effectively, and the best scenario is the direct groove tip implementing in stage I impeller. After blade tip grooving, the internal dynamics in the tip clearance tends to be more complex, the static pressure reduces notably in the suction side and the sound power level in the tip increases significantly, while the leakage losses decline distinctly. Blade tip pattern changes the profile and amplitude of the sound pressure in time domain; the base frequency and first five−order harmonics are clearly observed in two stage impellers, but only the second−order harmonics are emerged in the other regions. The noise is generated largely by low and medium frequency sound with an obvious broadband feature. © 2017 Elsevier Ltd


Ni C.,North China Electrical Power University | Zhao Z.,North China Electrical Power University | Cui X.,North China Electrical Power University
IEEE Transactions on Electromagnetic Compatibility | Year: 2017

Calculation of magnetic vector potential A is fundamental in the partial element equivalent circuit method, which directly affects the value of inductive part, called partial inductance. All of the existing methods for partial inductance are based on Lorenz gauge. This paper presents an analytical method for calculation of partial inductance with Coulomb gauge in quasi-static field. The difference lays on the calculation of A, which has an obvious impact in open loop problems. Some analytical results of conductor segments are derived for comparison of two different gauges, and show the difference between the proposed method and existing methods. Numerical experiments of the self-A nd mutual-partial inductances of conductor segments in open loop problems are also given. The results illustrate that the proposed method is consistent with the energy method, whereas the existing method gives different values, especially for short conductor segments whose difference might reach 50%. The proposed method may also be applied to closed loop problems and give same results with existing method. © 2017 IEEE.


Liu X.,State Grid Corporation of China | Zeng M.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2017

China currently faces the dual constraints of developing low-carbon economy and enabling sustainable energy utilization. It is an inevitable choice for the strategic transformation of economy development and energy development in China to develop renewable energy. Since renewable energy is a capital-and tech-intensive industry, which requires a large amount of investment and a high level of technology innovation. Investors face many different uncertainties when making a renewable energy project investment decision. Therefore, it has great significance for the development of renewable energy to evaluate the risks in renewable energy investment projects, and then make the best investment decisions. Based on above background, the topic of renewable energy investment risk is studied in this paper using system dynamics method. In the first part of the work, three main risks in renewable energy investment, technical risk, policy risk and market risk, have been discussed, and then causal loop diagram of investment risk and risk assessment model have been established by the system dynamics method, after that a numerical example was given in the last part of the paper. The result of the numerical example indicated that policy risk was the main factor affecting the investment in the early development stage, while policy risk and technology risk decline gradually, market risk has gradually become the main uncertainty affecting the investment in the mature development stage. © 2017


Fangxin L.,North China Electrical Power University
Journal of Computational and Theoretical Nanoscience | Year: 2016

At the time of considering influences of demands, primary causes why predicted accuracy is lower than the one with no influences of demands being considered mainly include three aspects: the market is not open enough and the existence of power supply giants makes the price not promptly meet supply-demand relationship; due to restrictions of physical devices, electricity utilization end can not promptly respond to change of electricity price; complex non-linear relationship exists between electricity price and electricity consumption. Based on prediction of electricity price, one electricity price decision-making method is proposed in the Thesis. At the same time, the method of peak detection and prediction will be used to predict short-time electricity consumption index, thus assisting decision making of electricity price. This method can be used to predict the electricity price in a certain period in the future when substantial change suddenly happens to electricity price and thus enable electricity consumers to arrange using plan in the future ahead of schedule according to predicted electricity price and to predict electricity price in a period when great change happens to electricity price at the time of finding this situation, thus making real-time adjustment to electricity utilization plan. Copyright © 2016 American Scientific Publishers All rights reserved.


Zhao Z.,Inner Mongolia University | Li H.,Inner Mongolia University | Luo Z.,North China Electrical Power University
Computers and Mathematics with Applications | Year: 2017

The convergence of space–time continuous Galerkin (STCG) method for the Sobolev equations with convection-dominated terms is studied in this article. It allows variable time steps and the change of the spatial mesh from one time interval to the next, which can make this method suitable for numerical simulations on unstructured grids. We prove the existence and uniqueness of the approximate solution and get the optimal convergence rates in L∞(H1) norm which do not require any restriction assumptions on the space and time mesh size. Finally, some numerical examples are designed to validate the high efficiency of the method showed herein and to confirm the correctness of the theoretical analysis. © 2017 Elsevier Ltd


Cui H.,North China Electrical Power University | Wei P.,North China Electrical Power University
Energy Policy | Year: 2017

The price of thermal coal has always been the focus of the debate between coal mining industry and electric power industry. The thermal coal price is always lower than other same quality coal, and this phenomenon of thermal coal price distortion has been existing in China for a long time. The distortion coal price can not reflect the external cost and the resource scarcity of coal, which could result in environment deteriorating and inefficient resource allocation. This paper studied the phenomenon of thermal coal price distortion through economic theoretical modeling and empirical cointegration analysis from the perspective of market forces. The results show that thermal coal price is determined by electricity price, the prediction elasticity of a electricity enterprise, price elasticity of demand of electricity, the input prediction elasticity of a electricity enterprise and the price elasticity of supply of thermal coal. The main reason of coal price distortion is the unbalance market force of coal industry and thermal coal generation industry. The distortion rate of coal price is positively related to the market force of electric power industry and negatively related to the industrial concentration of coal industry. © 2017 Elsevier Ltd


Zhao H.,North China Electrical Power University | Guo S.,North China Electrical Power University
Environment, Development and Sustainability | Year: 2017

At the aim of solving the increasing conflicts among the economic growth, resource shortage, and environmental aggravation, the eco-industrial park becomes a significant research issue to achieve sustainable development and circular economy. Therefore, evaluating the comprehensive benefit of eco-industrial parks and providing references and policy formulation in supporting the improvement of construction and management level for eco-industrial parks are of great significance. In this paper, a hybrid framework was proposed to assess the comprehensive benefit of eco-industrial parks in terms of circular economy and sustainability. Firstly, the evaluation index system was constructed by using grey-Delphi method, which included economic benefit criteria, social benefit criteria, and environmental benefit criteria with nine quantitative sub-criteria and four qualitative sub-criteria. Then, a new comparison-based method, namely the best-worst method, was employed to determine the weights of all sub-criteria and the performance values of all selected eco-industrial parks with respect to the qualitative sub-criteria. Finally, five selected representative eco-industrial parks in China were ranked in terms of comprehensive benefit, and the optimal eco-industrial park was selected. According to the results of comprehensive benefit evaluation for eco-industrial parks, the strengths and weaknesses of each eco-industrial park were obvious. At the end, the recommendations for the effective and rapid development of eco-industrial parks were formulated. © 2017 Springer Science+Business Media Dordrecht


Wang Z.,North China Electrical Power University
Revista Tecnica de la Facultad de Ingenieria Universidad del Zulia | Year: 2016

Urban flood control and disaster reduction program evaluation is a currently hot issue that involves complex multi-attribute evaluation process. Aiming at solving uncertain, incomplete and insistent information, this paper proposed an optimized GCA(Grey Correlation Analysis) method based on interval neutrosophic sets. Firstly, the positive and negative ideal program were calculated by using the algorithm and property of interval neutrosophic sets; secondly, gray correlation degrees based on interval neutrosophic sets were calculated to get the optimal program; thirdly, robustness test was used to verify the effectiveness of this optimized method , and finally, the validity and feasibility of the method are testified by empirical study in order to provide a reference for dynamic- group decision-making in urban flood control and disaster reduction program evaluations.


Wang J.,North China Electrical Power University | Yang Y.,North China Electrical Power University
Energy | Year: 2017

A hybrid electric-thermal (HET) following method is proposed for a combined cooling, heating and power (CCHP) system driven by natural gas and solar energy, focusing on the supply matching of domestic hot water, space cooling/heating and electricity. The domestic hot water thermal demand (Class A) is set to be met preferentially due to its immediateness and timeliness, and the space cooling/heating (Class B) thermal demand matching condition will be discussed from the view of comfort reliability. Detailed strategy methods under summer and winter conditions are presented. Variable electric-thermal ratio (RA, the ratio of the thermal demand of domestic hot water to the electric demand, RB, the ratio of the thermal demand of space cooling/heating to the electric demand) load conditions are analyzed and a comparison of HET between the base following electric load and following thermal load strategies is discussed for hotel applications. The criteria including primary energy consumption, carbon dioxide emission, operation cost and exergy efficiency is employed to evaluate the performances in the HET strategy. The results indicate that HET can achieve more benefits than the base operation strategies. © 2017 Elsevier Ltd


Chen K.,North China Electrical Power University | Tang J.,North China Electrical Power University
Journal of Alloys and Compounds | Year: 2017

The effects of the doping of three cations with different valence states (Cu2+, Ga3+ and Ge4+) on the sintering and electrical properties of (K0.4825Na0.4825Li0.035)(Nb0.8Ta0.2)O3 (KNLNT) ceramics have been investigated in detail. The results show that these three cations all act as acceptor dopant and improve the sintering of the KNLNT ceramics; ceramic samples with excellent properties can be obtained at much lower sintering temperatures, and the range of useable sintering temperatures has been widened. In addition, the acceptor doping with Cu2+, Ga3+ and Ge4+ has resulted in increases in the Curie temperatures and improvements in ferroelectric properties. The results also show that for the KNLNT ceramics, in order to obtain high mechanical quality factor (Qm), the divalent cation Cu2+ can be used, resulting in a three-fold enhancement in Qm. In contrast, in order to obtain a high planer electromechanical coupling factor (kp), the tetravalent cation Ge4+ can be utilized, and kp can be improved by as much as 54%. © 2016 Elsevier B.V.


Wang Z.-G.,North China Electrical Power University
European Physical Journal C | Year: 2017

In this article, we assign Y(4274) to the color octet–octet type axialvector molecule-like state with JP C= 1 + + tentatively, and construct the color octet–octet type axialvector current to study its mass and width with the QCD sum rules in details. The predicted mass favors assigning the Y(4274) to a color octet–octet type molecule-like state, but the predicted width strongly disfavors assigning the Y(4274) to the color octet–octet type molecule-like state. The Y(4274) may be the conventional charmonium state χc 1(3 P) , and it is important to observe the decay Y(4274) → J/ ψω to diagnose the nature of Y(4274). © 2017, The Author(s).


Huang R.,Beijing University of Chemical Technology | Zhang J.,Beijing Institute of Technology | Lin Z.,North China Electrical Power University
Automatica | Year: 2017

This paper proposes a novel decentralized adaptive excitation control scheme to globally stabilize large-scale power systems and enhance the transient stability. Two smooth functions are introduced to counteract the effect of unknown time-varying interactions, then a completely decentralized adaptive controller is constructed on the basis of the adaptive backstepping approach. The proposed controller utilizes only local measurements and has no requirement for the bounds of interconnections in the power system. All signals of the overall closed-loop large-scale power system are proved to be globally uniformly bounded. The proposed control scheme is tested on a two-area benchmark power system in the face of a symmetrical three-phase short circuit fault. Simulation results have showed better transient performances in comparison with existing controllers. © 2017 Elsevier Ltd


Li R.,North China Electrical Power University | Li L.,North China Electrical Power University
International Journal of Applied Electromagnetics and Mechanics | Year: 2017

For wireless power transfer (WPT) systems, communication between the two terminals of power transfer system is also an important problem to be solved. This paper proposes a design method of multi-turn dual-band coil for implementing synchronous transfer of power and data in WPT system with one set of WPT coils. An extra compensation circuit is inserted into the multi-turn spiral coil, so the new coil has two resonant frequencies that lie on both sides of the original resonant frequency of the multi-turn coil. Just one set of dual-band coils is used to provide the data and power transfer via two different resonant frequencies, so the undesirable interference in multi-coil WPT system is avoided. The equivalent circuit model is built to analyze the characteristic of the dual-band WPT system. The data pickup circuit is analyzed and designed for the receiver of WPT system. Finally, a dual-band WPT prototype with data pickup circuit is built to demonstrate the effectiveness of the proposed dual-band WPT system. © 2017 IOS Press and the authors. All rights reserved.


Gao Z.-Y.,North China Electrical Power University | Yang W.-J.,North China Electrical Power University
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2017

The study of reaction mechanism of mercury oxidation on halogenated activated carbon was conducted by B3LYP method in density functional theory of quantum chemistry. Seven ring zigzag clusters was selected as research model to simulate the activated carbon surface, two halogenated activated carbon models X-AC and X-AC-X (X=Cl, Br, I) were designed to investigate oxidation reaction mechanism. The oxidation reaction process was confirmed by calculating transition states, then adsorption energy and oxidation reaction energy barrier of elemental mercury adsorption on modified activated carbon surface were calculated. Research results indicate that: adsorption energy of elemental mercury adsorption on halogenated activated carbon surface is in the order of Cl>Br>I, indicating that elemental mercury adsorption on chlorine modified activated carbon surface is the most stable in view of adsorption strength. Oxidation reaction energy barriar of elemental mercury adsorption on halogenated activated carbon surface is in the order of Cl>Br>I, suggesting that oxidation reaction of elemental mercury and iodine modified activated carbon surface is most likely to occur in view of reaction difficulty. The experimental phenomena of elemental mercury removal by modified activated carbon can be correctly interpreted by analysing oxidation reaction difficulty order of elemental mercury adsorption on halogenated activated carbon surface. In order to correctly reveal the mechanism of elemental mercury removal by halogenated modified activated carbon, the study of reaction energy barriar of mercury oxidation on halogenated activated carbon is indispensable. © 2017, Science Press. All right reserved.


Liu J.,North China Electrical Power University | Xu F.,North China Electrical Power University | Lin S.,North China Electrical Power University
Journal of Cleaner Production | Year: 2017

Installing a photovoltaic (PV) power plant at a proper location has been a critical problem for the system planners and investors. In this study, grey cumulative prospect theory is employed to study the site selection of PV power plants from the perspective of sustainability. First, considering the sustainable development, eight decision-making criteria are identified and divided into three categories: geographical conditions, economic profits and environmental benefits. The decision-making steps of grey cumulative prospect theory are then proposed to select the optimal alternative and in this method, an optimization model is used to obtain the importance of criteria. The proposed method has also been implemented in a case of four cities in Northwest China in which the optimal alternative, Yulin city, is selected with the highest prospect value. Finally, a comparison analysis of multi-criteria decision-making methods and a sensitivity analysis of all criteria are performed and the results show that the proposed method can be used effectively for the site selection of PV power plants. © 2017 Elsevier Ltd


Jiang J.-Z.,North China Electrical Power University | Liu L.,North China Electrical Power University | Sun B.-M.,North China Electrical Power University
International Journal of Greenhouse Gas Control | Year: 2017

An investigation for the enhancement of nanoparticles (TiO2, MgO, SiO2) on the mass transfer for CO2 absorption was presented through both the experiment method and a 3-D unsteady model. The effects of nanoparticle loadings, nanoparticle diameters, nanoparticle species, solution species, experimental temperature and the CO2 initial volume fraction on the CO2 absorption were investigated in this paper. Considering the chemical reaction between gas and solution, a 3-D unsteady model was developed to study the mass transfer for CO2 absorption enhanced by nanoparticles in monoethanolamine (MEA) solution. Based on the analysis of zwitterion mechanism in the process of chemical reaction between MEA and CO2, it was shown that the rate of chemical reaction is proportional to the concentration of CO2 due to the large MEA concentration and the zero-order reaction in the liquid membrane. Further, the differential equation of mass transfer in three dimensions was set up, which is related to the rate of chemical reaction and the random distribution of nanoparticles. The random distribution of nanoparticles in a fluid element was determined by Monte Carlo method. In addition, the absorption experiments of CO2 in MEA solution using the bubbling reactor were carried out, which could also verify the correctness of the developed model. © 2017 Elsevier Ltd


Li H.,North China Electrical Power University | Liu C.,North China Electrical Power University | Li G.,North China Electrical Power University | Iravani R.,University of Toronto
IEEE Transactions on Power Systems | Year: 2017

This paper introduces an enhanced droop-based dc-voltage control method, including dead-band, for applications to the high-voltage direct-current (HVDC) grid that utilizes the voltage-sourced converter (VSC) technology. The proposed droop-control structure also autonomously imposes energy balance between the HVDC grid and its host ac system. The droop-control method (1) divides the VSC stations into four groups, (2) activates the droop-control of each group based on a prespecified voltage margin, and (3) introduces an improved power-voltage characteristic for desirable VSC station dynamic performance. Feasibility and performance of the proposed control method are evaluated based on time-domain simulation studies in the PSCAD platform, using the IEEE-39-Bus system that imbeds a five-terminal VSC-HVDC grid. Each VSC station is a monopolar modular multilevel converter (MMC). The study results show that the proposed droop-control method enables the HVDC-AC system to reach a new steady state after transient events. © 1969-2012 IEEE.


Yang L.,Beihang University | Li Y.,North China Electrical Power University | Li Z.,Beihang University
International Journal of Electrical Power and Energy Systems | Year: 2017

Power grid is a complex system which closely links the power generation and power consumer through transmission and distribution networks. With the development of smart grid, smart grid is more open to external communication systems, it also has exposed some problems in the network attacks. A new false data injection attack (called the unobservable attack) that can bypass the traditional BDD and inject random errors into state estimation. We propose an improved extreme learning machine (ELM) for attack detection. The artificial bee colony (ABC) incorporates the thought of differential evolution algorithm (DE) to optimize ELM for improving detection precision. In this paper, Autoencoder is used to reduce the dimensionality of the measurement data, which makes the low-dimensional data information basically and fully represent high-dimensional data. We verify the performance of the proposed method on IEEE bus systems, and prove that the proposed method can effectively detect such unobservable attack. © 2017


Yin F.-F.,North China Electrical Power University | Shi J.-H.,North China Electrical Power University
Proceedings - 2016 International Conference on Information System and Artificial Intelligence, ISAI 2016 | Year: 2016

At present, more and more courses and exams are held in the college computer room, which leads to more complex operating environment and higher system requirements, so the systematic maintenance work is very difficult. In the article, we develope a control system by c# language, which combines with the actual usage of room and the blank space of the computer room management, aimed at focusing on monitoring student behavior during the computer operating time and controlling running programs, network services, storage devices, etc. This system assists teachers to manage and maintain computer room more easily, and greatly reducing the workload of computer room management personnel. © 2016 IEEE.


Fu D.,North China Electrical Power University | Wang L.,North China Electrical Power University | Tian X.,North China Electrical Power University
Journal of Chemical Thermodynamics | Year: 2017

The surface tension (γ) of 2-diethylaminoethanol (DEAE), DEAE-monoethanolamine (MEA), and DEAE-piperazine (PZ) aqueous solutions was measured by using the BZY-1 surface tension meter. The temperature ranged from 303.2 K to 323.2 K. The mass fraction of DEAE, MEA and PZ respectively ranged from 0.30 to 0.50, 0.05 to 0.15 and 0.025 to 0.075. An equation was proposed to model the surface tension and the calculated results agreed well with the experiments. The effects of temperature and mass fraction of amines on the surface tension were demonstrated on the basis of experiments and calculations. © 2016 Elsevier Ltd


Fu C.,North China Electrical Power University | Tan W.,North China Electrical Power University
Control Engineering and Applied Informatics | Year: 2017

Partially decentralized control for a Benchmark Boiler is proposed. First a partially decentralized control structure selection method is proposed based on the gap metric. Since the boiler contains integrating action due to the drum level dynamics, most interaction measures are not applicable here. The gap metric can be used for both stable and unstable systems, so the proposed method can be used for selecting suitable control structure for the boiler. The design of partially decentralized controllers is based on the generalized predictive control method, which overcomes the drawback of the IMC method that requires computing the pseudo-inverse of a non-square matrix. Simulation results show that the proposed partially decentralized control can achieve good performance with a simpler structure.


Gao J.,North China Electrical Power University | Sun S.,North China Electrical Power University
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2017

The simulation model of the pulverizing system of a 300 MW lignite oxygen-enriched combustion boiler was developed. And the dynamic and static simulation experiments were completed, the experiments included lignite surface moisture content variation, disturbance of feeder norm speed, flue gas inlet temperature and flow rate etc. The results show that, the model is able to correctly simulate the dynamic process of the system. Moisture reduction has a larger impact on the pulverizing system operating parameters. The mill outlet temperature gets a significant rise, especially when it is less than 30%. When the feeder norm speed or flow rate of inlet flue gas changes, the mill outlet parameters change obviously, especially the moisture of pulverized coal. Thus, the ratio of flue gas flow and coal should be controlled strictly by using re-circulation flue gas to dry high moisture lignite. © 2017, The Editorial Board of Journal of System Simulation. All right reserved.


Liu S.,North China Electrical Power University | Liu C.,North China Electrical Power University
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2017

Thermal power plants for the main steam temperature are difficult to control, using Imperialist Competitive Algorithm to accomplish main steam temperature cascade control strategy simulation optimization. The main steam cascade PID control system with limiting and speed actuator as simulation object determined the appropriate error indicator function ITAE criterion. Several types of Cascade PID control scheme were compared. Simulation results show that Imperialist Competitive Algorithm is convenient and effective method of parameter optimization, and PID-PI cascade type system has better balanced dynamic performance, anti-interference ability. © 2017, The Editorial Board of Journal of System Simulation. All right reserved.


Wang D.,North China Electrical Power University | Li J.,North China Electrical Power University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2017

The status monitoring data of substation equipment have the characteristics of big volume and low value density, since the traditional data processing method have some limitations in fast query for status monitoring, evaluation and diagnosis. By analyzing the characteristics of status monitoring data and the distributed data storage method, a big data processing framework for the status monitoring of the substation equipment is presented. By combing data attributes such as acquisition time, device code and linked device code, three kinds of status monitoring row key are designed to improve the flexibility of row key query. In order to solve the low efficiency of full table scan problem when the row key is unknown, a secondary index method based on coprocessor is proposed to achieve fast query under non-row key constraint conditions. The experimental results show that, the secondary index based on coprocessor has an obvious improvement on the query efficiency compared with the non-index and the IHBase secondary index, the impact of writing speed on the status monitoring data is insignificant, and it can better meet the needs of fast and flexible query of status monitoring data in big data environment. © 2017 Automation of Electric Power Systems Press.


Zhao X.,North China Electrical Power University | Yang G.,North China Electrical Power University
Journal of Intelligent and Fuzzy Systems | Year: 2017

Based on the minimum entropy and fuzzy subtractive clustering method, a new specialized algorithm for online multi-model identification is proposed in this paper. Different from the traditional identification model, the structure and parameters of the established model can be recursively updated when new data coming to the system, which makes it a wise choice for online modeling and complex processes control. The entropy-based online fuzzy subtractive clustering method is used to determine the number of the local models and their corresponding memberships. A controlled auto-regressive integrated moving average expression is adopted as the form of linear subsystems, for it not only match the identification process, but also can be used to design the control system easily. The parameters of local models are calculated by weighted recursive least square method, and the nondimensional error index is used to evaluate the performance of the identified model. By applying generalized predictive control strategy to the established model, a fuzzy generalized predictive control system is constructed, and the control law is given in the paper. Finally, a case of the method to "Mackey-Glass difference time delay equation" is studied. The simulation results illustrate the viability and the robustness of the strategy. © 2017 IOS Press and the authors. All rights reserved.


Lu X.,North China Electrical Power University | Xiao H.,North China Electrical Power University
Ceramics - Silikaty | Year: 2017

The overall conductivity of crystalline lithium ion conductors is generally low due to the large grain boundary resistance. In order to improve the grain boundary conductivity, NASICON structured Li1+xAlxSn2-x(PO4)3 has been studied in this paper. Samples Li1.2Al0.2Sn1.8(PO4)3 with the desirable amount of Al, made of a mixture of not-treated powders and treated powders in various ratios, are prepared to investigate the mixing effect on the grain boundary conductivity. The grains morphology of samples has changed from spherical shapes to rectangular shapes upon mixing, which indicates a liquid (or glass) phase formation during sintering. The overall conductivity peaks at 20 % of not-treated powders. The increase in the overall conductivity is attributed to the increase of grain boundary conductivity, not the grain conductivity. The reason accounting for the enhancement of the grain boundary conductivity is attributed to a less-resistive grain boundary as indicated by the grains morphology changes observed.


Hou X.,North China Electrical Power University | Yuan W.,North China Electrical Power University
CIE 2016: 46th International Conferences on Computers and Industrial Engineering | Year: 2016

It is sure that engineering projects exist many problems which always produce disadvantage to projects and often appear suddenly. Obviously, these problems bring much bother to engineering project managers. For the purpose of researching and solving these problems, many managers have been engaged in investigating the problems in engineering projects. Some direct relationships of all problems with their stage are discovered by analyzing the statistics to various problems. The results show that it is construction stage where the amount of problems is the maximum in engineering project; the increasing of the problems' amount is outstanding from decision-making stage to arranged stage. However, the problems' amount from construction stage to conclusion stage will decrease. The result warns that it is significant to project managers to make effective ready for solving some problems in advance. So, what is very important for project managers is to improve engineering management level.


Ming Z.,North China Electrical Power University | Ping Z.,North China Electrical Power University | Shunkun Y.,North China Electrical Power University | Hui L.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2017

China's thermal power industry has gone through the phases of rapid development in the last decade. But the excessive enthusiasm of thermal power investment is making this industry overcapacity. The unbalanced demand-supply relationship in electric power market greatly affects the economic benefit of most thermal power plants. In this paper, we give an overall review of the overcapacity situation of China's thermal power industry, which is supported by latest data. Then, policy orientation and its effect is discussed. It can be found out that policies on the respect of construction scale control, renewable power integration, feed-in tariff reduction and environmental protection were considered as the main solution to relieve the over capacity situation. Finally, we propose three suggestions for the future development of China's thermal industry. © 2017 Elsevier Ltd


Zuo Y.,North China Electrical Power University | Li X.,China Electric Power Research Institute
2016 IEEE Symposium Series on Computational Intelligence, SSCI 2016 | Year: 2016

Battery Energy Storage Station (BESS) is the most effective way to facilitate transmission of large scale hybrid power generation that includes unpredictable renewable energy sources. In this paper we consider a wind-solar-thermal power system with high voltage direct current (HVDC) transmission and propose a novel power imbalance adjustment scheduling strategy based on game theory method. We propose a cooperative approach to maximize the total benefits by developing an optimal power adjustment distribution scheduling method. First use frequency deviation to determine the required total power adjustment and then according to cooperative game model the distributed power adjustment orders are decided. To incentivize the self-interested subsystem to take the system optimal action, we design a punishment protocol which each agent would be punished due to decreased sale price and subsidy. We exam the impact of proposed cooperative strategy through a simulation model and demonstrate that our analysis provides useful insight for designing incentive-compatible game schemes for the hybrid power system with HVDC transmission. © 2016 IEEE.


Wang D.,North China Electrical Power University | Yu M.,North China Electrical Power University
2016 14th International Conference on Control, Automation, Robotics and Vision, ICARCV 2016 | Year: 2016

In this paper, leader-following consensus of the discrete-time heterogenous multi-agent system with bounded communication delays is studied. The heterogeneous multi-agent system is composed of first-order and second-order integrator agents. By applying the graph theory and the algebra theory, sufficient consensus criteria are obtained to guarantee that each agent can track the leader. Despite there exist bounded time delays among agents, consensus can also be realised under fixed and switching topologies. Event-triggered control laws are designed to reduce the frequency of individual actuation updating. Numerical examples are provided to demonstrate the effectiveness of the theoretical results. © 2016 IEEE.


Wang A.,North China Electrical Power University | Wen Y.,North China Electrical Power University
EVS 2016 - 29th International Electric Vehicle Symposium | Year: 2016

In this paper, a method of multi-objective optimal designing on interior permanent magnet synchronous machines (IPMSM) for electric vehicle application to get higher the torque produced by per unit mass PM, lower torque ripple and lower iron loss is presented. The relevant structure parameters of the IPMSM, such as PM size, location of barriers in rotor and air gap length are optimized. The effects and its relative importance of each optimization variable on the torque produced by per unit mass PM, the torque ripple and the iron loss of the machine are analyzed to get the best optimization scheme. The iron loss and torque ripple are effectively reduced by adopting the method, and the torque produced by per unit mass PM of the machine is greatly increased as well.


Gong J.,Sun Yat Sen University | Zhou S.,Tsinghua National Laboratory for Information Sciences and Technology | Zhou Z.,North China Electrical Power University | Niu Z.,Tsinghua National Laboratory for Information Sciences and Technology
IEEE Transactions on Wireless Communications | Year: 2017

Motivated by the rapid development of energy harvesting technology and content-aware communication in access networks, this paper considers the push mechanism design in small-cell base stations (SBSs) powered by renewable energy. A user request can be satisfied by either push or unicast from the SBS. If the SBS cannot handle the request, the user is blocked by the SBS and is served by the macro-cell BS instead, which typically consumes more energy. We aim to minimize the ratio of user requests blocked by the SBS to total number of user requests. With finite battery capacity, Markov decision process-based problem is formulated, and the optimal policy is found by dynamic programming (DP). Two threshold-based policies are proposed: the push-only threshold-based policy and the energy-efficient threshold-based policy, and the closed-form blocking probabilities with infinite battery capacity are derived. Numerical results show that the proposed policies outperform the conventional non-push policy if the content popularity changes slowly or the content request generating rate is high, and can achieve the performance of the greedy optimal threshold-based policy. In addition, the performance gap between the threshold-based policies and the DP optimal policy is small when the energy arrival rate is low or the request generating rate is high. © 2016 IEEE.


Wang Y.,Beijing Union University | Huang M.,North China Electrical Power University
ICIC Express Letters, Part B: Applications | Year: 2017

The purpose of this paper is to illustrate the structure, process, interoperability, and tools for the realization of the collaborative emergency management (EM) platform using big data. First, it analyzes the characteristics, especially the processes before and after using big data in EM. Secondly, it defines a structure of a collaborative EM with stakeholders of public, non-profit and private organizations, as well as social media and personal citizens and communities. Finally, it discusses several key technologies and implementing strategies to support the collaborative EM platform engaging and utilizing big data. Above all, the platform it proposed can enable EM to utilize information both from organizations and personal citizens, which means the data sources in EM will be expanded from official data to social media data. © 2017 ICIC International.


Lu B.X.,North China Electrical Power University | Sun H.Y.,North China Electrical Power University
AIP Advances | Year: 2017

A corona discharge measurement system and simulation model are presented to investigate the effects of photoionization and ion-impact secondary emission process in negative corona discharge. The simulation results obtained is shown good agreement with experimental observations. Distribution of electron density along the symmetry axis at three critical moments is shown and the role of photoionization in negative corona discharge is clearly explained. Moreover, the current pulses are also presented under different secondary emission coefficients and the effect of the secondary emission coefficient is discussed. © 2017 Author(s).


Fang L.,Beihang University | Ge M.-W.,North China Electrical Power University
Chinese Physics Letters | Year: 2017

To shed light on the subgrid-scale (SGS) modeling methodology of nonlinear systems such as the Navier Stokes turbulence, we define the concepts of assumption and restriction in the modeling procedure, which are shown by generalized derivation of three general mathematical constraints for different combinations of restrictions. These constraints are verified numerically in a one-dimensional nonlinear advection equation. This study is expected to inspire future research on the SGS modeling methodology of nonlinear systems. copy; 2017 Chinese Physical Society and IOP Publishing Ltd.


Xu Z.N.,North China Electrical Power University
AIP Advances | Year: 2017

The blur around the contact points significantly decreases the evaluated static contact angle for superhydrophobic surface which is clearly presented in the paper. To improve the accuracy in the evaluated static contact angle for superhydrophobic surface, an accurate static contact angle algorithm, namely ADSA-PH (axisymmetric drop shape analysis-profile and height), is proposed. It discards the extracted drop edge points close to the contact points and makes use of the residual points and the drop height to determine the static contact angle. The contact angle errors caused by the blur close to the contact points are significantly reduced. The classical ADSA-P algorithm, the modified selected-plane method and the proposed algorithm are used to evaluate static contact angle. The results validate the proposed algorithm. The accuracy in the evaluated contact angle increases with increasing image resolution. To reduce the error caused by a limitation of image resolution, the minimum allowable image resolutions are presented. © 2017 Author(s).


Zhang Z.-H.,North China Electrical Power University | Xu P.,North China Electrical Power University
Chinese Physics C | Year: 2017

The recently observed two high-spin rotational bands in the proton emitter 113Cs are investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. By using the configuration assignments of band 1 [π3/2+[422](g 7/2), α = -1/2] and band 2 [π1/2+[420](d 5/2), α = 1/2], the experimental moments of inertia and quasiparticle alignments can be reproduced much better by the present calculations than those using the configuration assginment of π1/2-[550] (h 11/2), which in turn may support these configuration assignments. Furthermore, by analyzing the occupation probability n μ of each cranked Nilsson level near the Fermi surface and the contribution of each orbital to the angular momentum alignments, the backbending mechanism of these two bands is also investigated. © 2017 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.


Zhang K.,North China Electrical Power University | Chen Q.,North China Electrical Power University
2016 IEEE International Conference on Information and Automation, IEEE ICIA 2016 | Year: 2016

With the development of artificial intelligence, robot navigation based on natural language processing is concerned by more researchs. At the present stage, there are few studies on route natural language processing (RNLP), and there is no professional corpus, so the method of route natural language processing is generally based on a small amount of restricted corpus. This paper puts forward a method of semantic extraction based on semantic role labeling. Firstly, the simulation environment is built, and the route natural language corpus is built. Then, based on the analysis of the route natural language corpus, this paper proposes several common chunks of route natural language, and carries out the chunking experiment. Finally, semantic role labeling (SRL) is performed on the basis of the chunking. According to the results of semantic role labeling, navigation intention map is generated. The experimental results show that this method is suitable for the semantic extraction of route natural languages with non restricted. © 2016 IEEE.


Ma L.,North China Electrical Power University | Cao P.,North China Electrical Power University
2016 IEEE International Conference on Information and Automation, IEEE ICIA 2016 | Year: 2016

Firefly algorithm (FA), first put forward by a Cambridge scholar Yang, is a kind of swarm intelligent algorithm imitating nature fireflies' predation and courtship behaviour. It has been widely studied and gradually applied to different engineering fields. However, the basic FA has several shortcomings such as easiness to fall into local optimum, premature convergence, et al. Recent years have witnessed different ways taken by some scholars to improve the FA. In this work, two improved firefly algorithms, inertia weight firefly algorithm and chaos-based firefly algorithm, are deeply investigated. The two algorithms are simulated and their performances are compared through typical benchmark functions. © 2016 IEEE.


News Article | May 4, 2017
Site: www.eurekalert.org

North China is one of the areas of strong earthquake activity on the Chinese mainland. In the 1960s~1970s, North China has undergone the 1966 Xingtai Ms7.2, 1969 Bohai Ms7.4, 1975 Haicheng Ms7.3 and 1976 Tangshan Ms7.8 earthquake, causing great losses to people's life and property, where the Tangshan earthquake caused casualties amounted to 240 thousand. In the past 50 years, Chinese seismologists have carried on the large-scale deep geophysical exploration and research, obtained the detailed crustal and upper mantle structure, and revealed the deep tectonic environment of strong earthquake in North China. The related research paper is entitled "Crustal and upper mantle structure and deep tectonic genesis of large earthquakes in North China" published in SCIENCE CHINA Earth Sciences, Vol.60, 2017, wrote by Professor Wang Chunyong at Institute of Geophysics, China Earthquake Administration. The research group reviewed the main achievements of the researches on the crustal and upper mantle structure as well as the seismogenic environment and tectonic patterns in North China since the 1966 Xingtai earthquake. Based on plate tectonics theory, geoscientists have successfully explained the patterns and mechanisms of earthquake activity on the global plate boundaries. However, plate tectonics theory has not explained the occurrence of earthquakes within the continental plate. North China is located within the Asian continent, and the geological structure, seismicity and focal mechanism show that the seismic activity is very different from that in the region of the plate boundary, indicating that the seismotectonics in North China is quite complex. The nucleation, occurence and development of continental earthquakes, and their relationship with the deep-seated structure of the earth are one of the most important subjects in the solid Earth Science. Seismologists have carried out numerous surveys of the crustal and upper mantle structure, and associated studies of seismic tomography in North China, finished 42 deep seismic souding profiles with total length of ~12000 km, and seismic tomography of three-dimensional crustal and upper mantle structure based on the seismic records at ~600 stations. Deep seismic reflection profiling results indicate a complex tectonic setting in the strong earthquake areas of North China, where a listric normal fault and a low-angle detachment in the upper crust coexist with a high-angle deep fault passing through the lower crust to the Moho beneath the hypocenter. Seismic tomography images revealed that the lithospheric structure in North China is highly inhomogeneous, where most of the large earthquakes occurred in the transition between the high- and low-velocity zones, and the Tangshan earthquake area is characterized by a low-velocity anomaly in the middle-lower crust. Comprehensive analysis of geophysical data identified that the deep seismogenic environment in the North China extensional tectonic region is generally characterized by a low-velocity anomalous belt beneath the hypocenter, inconsistency of the deep and shallow structures in the crust, a steep crustalal-scale fault, relative lower velocities in the uppermost mantle, and local Moho uplift. Earthquake prediction is one of the scientific problems in the Earth Science that have not yet been solved. A deep understanding of the deep tectonic environment of strong earthquakes will help to solve the problem of earthquake prediction. Seismologists Deng Qidong (2008) presented that the surface and shallow-deep tectonic features in the large earthquake area have been releaved by the combination of deep seismic reflection profiling and the surface geology and tectonic enviorment, thus we are able to obtain more comprehensive understanding of seismogenic tectonic conditions in the active fold area (the extension zone and the compression zone) of the normal or strike-slip normal fault and the reverse fault. He further pointed out that it is the right direction to combine the surface geological work with the deep structure and the deep material detection, and it is the key to understand the nucleation and occurrence of the large earthquake. The study of deep-seated structure and seismogenic environment in North China is an excellent model of the combination of deep geophysical exploration and surface seismic geologic research. Despite the deep seismic exploration and seismic tomography research has greatly enriched the knowledge of deep-seated structure and seismogenic environment, due to the complexity of continental seismotectonics, we still face some deep-seated problems, which need to further research. Wang C Y, Wu Q J, Duan Y H, Wang Z S, Lou H. 2017. Crustal and upper mantle structure and deep tectonic genesis of large earthquakes in North China. Science China Earth Sciences, 60: 821-857, doi: 10.1007/s11430-016-9009-1


Zhang S.,North China Electrical Power University | Andrews-Speed P.,National University of Singapore | Zhao X.,North China Electrical Power University
Energy Policy | Year: 2013

This paper identifies and explains how political and institutional factors have determined the relative successes and failures of China's wind power policy over the period 2005-2011. It finds that China has made significant progress in pursuing its wind power policy in terms of cumulative installed capacity, wind turbine manufacturing industry development and wind turbine cost, and argues that these achievements can be attributed to the political motives and institutional arrangements of the Chinese government as well as to institutional changes. On the other hand, the paper finds that there are two prominent policy failures, namely the low proportion of grid-connected capacity and the rising trend of wind turbine incidents. These have undermined the efficiency and effectiveness of China's wind power program. The paper holds that the institutional sources for the first policy failure lies in the preference for setting wind power development targets in terms of installed capacity rather than generation and in coordination problems while the second policy failure lies in the lack of state technical codes for wind power integration and the unfair competition from the large state-owned power companies. The paper contributes to the academic literature on the political and institutional roles in China's wind power policy. © 2013 Elsevier Ltd.


Huang Y.,Xinjiang Institute of Ecology and Geography | Li Y.P.,North China Electrical Power University | Chen X.,Xinjiang Institute of Ecology and Geography | Ma Y.G.,Xinjiang Remote Sensing Center
Agricultural Water Management | Year: 2012

An integrated optimization method is developed for supporting agriculture water management and planning in Tarim River Basin, Northwest China. The developed method couples two-stage stochastic programming (TSP) with inexact quadratic program (IQP). The hydrological model is provided for forecasting the available irrigation water. The simulation system is then embedded into an optimization framework, where the objective is to maximize the system benefit for water resources management. The developed method can not only deal with nonlinearities in the cost/benefit objective and uncertainties expressed as probabilities and intervals, but also support the analysis of policy scenarios that are associated with economic penalties when the promised water-allocation targets are violated. A case study is conducted for Kaidu-kongque watershed in Tarim River Basin. The results obtained can help generate desired policies for water resources management with maximized economic benefit and minimized system-failure risk. © 2012 Elsevier B.V..


Zhang S.,North China Electrical Power University | Andrews-Speed P.,National University of Singapore | Zhao X.,North China Electrical Power University | He Y.,North China Electrical Power University
Energy Policy | Year: 2013

This paper analyzes China's policy approach to renewable energies and assesses how effectively China has met the ideal of appropriate interactions between renewable energy policy and renewable energy industrial policy. First we briefly discuss the interactions between these two policies. Then we outline China's key renewable energy and renewable industrial policies and find that China's government has well recognized the need for this policy interaction. After that, we study the achievements and problems in China's wind and solar PV sector during 2005-2012 and argue that China's policy approach to renewable energies has placed priority first on developing a renewable energy manufacturing industry and only second on renewable energy itself, and it has not effectively met the ideal of appropriate interactions between renewable energy policy and renewable energy industrial policy. Lastly, we make an in-depth analysis of the three ideas underlying this policy approach, that is, the green development idea, the low-carbon leadership idea and indigenous innovation idea. We conclude that Chinas' policy approach to renewable energies needs to enhance the interactions between renewable energy policy and renewable energy industrial policy. The paper contributes to a deeper understanding of China's policy strategy toward renewable energies. © 2013 Elsevier Ltd.


Wei L.,North China Electrical Power University | Fang F.,North China Electrical Power University | Shi Y.,University of Victoria
IEEE Transactions on Control Systems Technology | Year: 2014

As an important process parameter of the U-tube steam generator (UTSG) in a nuclear power unit, the water level must be maintained in a safe range when the unit is working under fixed or variable conditions. Because the dynamic responses vary significantly when the load changes, traditional control methods cannot effectively maintain the UTSG water level, especially with a low load. In this brief, an adaptive backstepping-based composite nonlinear feedback control scheme is proposed. The adaptive backstepping approach is used to design the water level controller and the feedwater flow controller separately, forming a cascade control structure to overcome the load disturbance and feedwater flow fluctuation. Furthermore, the composite nonlinear feedback control action is integrated into the feedwater flow controller to accommodate the opening constraint of the feedwater valve. Case studies, based on a practical nuclear UTSG model, show the effectiveness of this control scheme. © 2013 IEEE.


Liu Y.-S.,Tsinghua University | Liu Y.-S.,North China Electrical Power University | Liu Y.-S.,Tsinghua National Laboratory for Information Sciences and Technology | Ramani K.,Purdue University | Liu M.,Tsinghua University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

A new visibility graph-based algorithm is presented for computing the inner distances of a 3D shape represented by a volumetric model. The inner distance is defined as the length of the shortest path between landmark points within the shape. The inner distance is robust to articulation and can reflect the deformation of a shape structure well without an explicit decomposition. Our method is based on the visibility graph approach. To check the visibility between pairwise points, we propose a novel, fast, and robust visibility checking algorithm based on a clustering technique which operates directly on the volumetric model without any surface reconstruction procedure, where an octree is used for accelerating the computation. The inner distance can be used as a replacement for other distance measures to build a more accurate description for complex shapes, especially for those with articulated parts. The binary executable program for the Windows platform is available from https://engineering.purdue.edu/PRECISE/VMID. © 2011 IEEE.


Yi Y.,Beijing Normal University | Yang Z.,Beijing Normal University | Zhang S.,North China Electrical Power University
Environmental Pollution | Year: 2011

The concentrations of heavy metals (Cr, Cd, Hg, Cu, Zn, Pb and As) in the water, sediment, and fish were investigated in the middle and lower reaches of the Yangtze River, China. Potential ecological risk analysis of sediment heavy metal concentrations indicated that six sites in the middle reach, half of the sites in the lower reach, and two sites in lakes, posed moderate or considerable ecological risk. Health risk analysis of individual heavy metals in fish tissue indicated safe levels for the general population and for fisherman but, in combination, there was a possible risk in terms of total target hazard quotients. Correlation analysis and PCA found that heavy metals (Hg, Cd, Pb, Cr, Cu, and Zn) may be mainly derived from metal processing, electroplating industries, industrial wastewater, and domestic sewage. Hg may also originate from coal combustion. Significant positive correlations between TN and As were observed. © 2010 Published by Elsevier Ltd.


Li Y.P.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Chen X.,Xinjiang Institute of Ecology and Geography
Applied Energy | Year: 2011

Greenhouse gas (GHG) concentrations are expected to continue to rise due to the ever-increasing use of fossil fuels and ever-boosting demand for energy. This leads to inevitable conflict between satisfying increasing energy demand and reducing GHG emissions. In this study, an integrated fuzzy-stochastic optimization model (IFOM) is developed for planning energy systems in association with GHG mitigation. Multiple uncertainties presented as probability distributions, fuzzy-intervals and their combinations are allowed to be incorporated within the framework of IFOM. The developed method is then applied to a case study of long-term planning of a regional energy system, where integer programming (IP) technique is introduced into the IFOM to facilitate dynamic analysis for capacity-expansion planning of energy-production facilities within a multistage context to satisfy increasing energy demand. Solutions related fuzzy and probability information are obtained and can be used for generating decision alternatives. The results can not only provide optimal energy resource/service allocation and capacity-expansion plans, but also help decision-makers identify desired policies for GHG mitigation with a cost-effective manner. © 2010 Elsevier Ltd.


Cheng Y.,North China Electrical Power University | Zhai N.,Taian Power Supply Corporation
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

In the areas that have executed peak-valley price, reasonable adjustment of time period partition is a new problem when considering current customer responses. The fuzzy membership based method reported in the literature to divide time periods is no longer suitable for adjustment of time period partition. A new time period partition model for time-of-use electrical price based on customer response is proposed. This model compares the intensity variation of customers load profile proportion structure to estimate customer response degree and property index for each time point. Then, based on the response degree of each point, the model adjusts time period partition of fuzzy membership cluster analysis results. The model is applied on real data set of some regions. The results demonstrate that the model can effectively stimulate demand response through adjustment of time period partition scheme. © 2012 State Grid Electric Power Research Institute Press.


Zhao Z.-Y.,North China Electrical Power University | Tian Y.-X.,North China Electrical Power University | Zillante G.,University of Adelaide
Renewable and Sustainable Energy Reviews | Year: 2014

The wind power industry is a complex industry involving many different types of enterprises from diverse fields loosely working together to form both internal and external associations. As a complicated system it is necessary to detect the location of the various industry components, their operation characteristics and the various relationships between the many sectors of the wind power industry. Using the general industry chain theory, this paper develops a wind power industry chain model and examines the operation mechanisms of the industry. This leads to the establishment of three perspectives for the wind power industry, these are the supply chain model, the technology chain model and the value chain model that respectively reflect the supply-demand relationship, technology transfer and value creation of wind power related industries. The models can be used to analyze: the resources distribution, the supply and demand and production relationships amongst related enterprises, the relevant technology systems and the value increase process of the wind power industry. Using China's wind power industry as an example, this study uses: (1) the supply chain to analyze the construction, equipment supply and the on-grid connection of wind power; (2) the technology chain to evaluate the technical status of China's wind power industry from the perspective of the level of technology, the source of the technology and the technology standard; and (3) the value chain to analyze the value distribution of China's wind power industry. The results suggest that over capacity, lack of core technology and an incomplete follow up service system are the major obstacles to China's wind power industry development. The models form an effective tool to analyze and evaluate the development status of the wind power industry in different countries, and support the concept of formulating a sustainable development strategy. © 2014 Published by Elsevier Ltd.


Li Y.F.,North China Electrical Power University | Li Y.P.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Chen X.,Xinjiang Institute of Ecology and Geography
Applied Energy | Year: 2010

In this study, an inexact fuzzy-stochastic energy model (IFS-EM) is developed for planning energy and environmental systems (EES) management under multiple uncertainties. In the IFS-EM, methods of interval parameter fuzzy linear programming (IFLP) and multistage stochastic programming with recourse (MSP) are introduced into a mixed-integer linear programming (MILP) framework, such that the developed model can tackle uncertainties described in terms of interval values, fuzzy sets and probability distributions. Moreover, it can reflect dynamic decisions for facility-capacity expansion and energy supply over a multistage context. The developed model is applied to a case of planning regional-scale energy and environmental systems to demonstrate its applicability, where three cases are considered based on different energy and environmental management policies. The results indicate that reasonable solutions have been generated. They are helpful for supporting: (a) adjustment or justification of allocation patterns of regional energy resources and services, (b) formulation of local policies regarding energy consumption, economic development and environmental protection, and (c) in-depth analysis of tradeoffs among system cost, satisfaction degree and environmental requirement under multiple uncertainties. © 2010 Elsevier Ltd. All rights reserved.


Li Y.P.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Chen X.,Xinjiang Institute of Ecology and Geography
Energy Policy | Year: 2011

In this study, an interval-valued minimax regret analysis (IMRA) method is proposed for planning greenhouse gas (GHG) abatement under uncertainty. The IMRA method is a hybrid of interval-parameter programming (IPP) and minimax regret analysis (MMR) techniques. The developed method is applied to support long-term planning of GHG mitigation in an energy system under uncertainty. Mixed integer linear programming (MILP) technique with fixed-charge cost function is introduced into the IMRA framework to facilitate dynamic analysis for decisions of timing, sizing and siting in planning capacity expansions for power-generation facilities. The results obtained indicate that replacing fossil fuels with renewable energy sources (i.e. hydro, wind and solar power) can effectively facilitate reducing the GHG emissions. They can help decision makers identify an optimal strategy that can facilitate reducing the worst regret level incurred under any outcome of the uncertain GHG-abatement target. © 2011 Elsevier Ltd.


Yu J.,University of Electronic Science and Technology of China | Yu J.,Peking University | Wang L.,Peking University | Yu M.,North China Electrical Power University
International Journal of Robust and Nonlinear Control | Year: 2011

Stabilization problems of networked control systems (NCSs) with bounded packet losses and transmission delays are addressed. We model such NCSs as a class of switched systems, and establish stabilizing conditions in the form of matrix inequalities by using packet-loss dependent Lyapunov functions. By solving the inequalities, packet-loss dependent controllers are designed for two types of packet-loss processes: one is an arbitrary packet-loss process, and the other is a Markovian packet-loss process. Several numerical examples and simulations are worked out to demonstrate the effectiveness of the proposed design techniques. © 2010 John Wiley & Sons, Ltd.


Wang A.,North China Electrical Power University | Jia Y.,North China Electrical Power University | Soong W.L.,University of Adelaide
IEEE Transactions on Magnetics | Year: 2011

This paper presents a detailed comparison of the characteristics of five different rotor topologies for a distributed winding permanent-magnet (PM) machine for high-performance traction applications, including hybrid electric vehicles. These rotor topologies include one surface PM topology and four single-layer interior PM topologies (conventional, segmented, V shape, and W̄). The performance characteristics, which include the back-electromotive force and its harmonics, magnet mass, iron loss, and ripple torque are compared and analyzed. A 7.5-kW interior permanent-magnetic (IPM) prototype using the conventional rotor topology was tested and the finite-element analysis results were compared. The aim of the paper is to give some guidance and reference for machine designers who are interested in IPM machine selection for high-performance traction applications. © 2011 IEEE.


Zhang S.,North China Electrical Power University | Zhao X.,North China Electrical Power University | Andrews-Speed P.,National University of Singapore | He Y.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2013

Wind power and solar PV power are the two major renewable energy technologies that are currently under rapid development in China. In this paper, the similarities and differences between the development trajectories of the two sectors are examined in terms of development status, development policy and development trend. Five interesting findings from the comparison are obtained and several policy recommendations are made. This paper contributes to the study on China's renewable energy policy from a new perspective. © 2013 Elsevier Ltd.


Yi Y.-J.,Beijing Normal University | Zhang S.-H.,North China Electrical Power University
Environmental Science and Pollution Research | Year: 2012

Purpose: The objective of this paper is to assess the regulation of the accumulation of heavy metals in the aquatic environment and different fish species. Methods: Water and fish samples were collected from upper to lower reaches of the Yangtze River. The heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in the muscle tissue of seven fishes were measured. Additionally, the relationships between heavy metal concentrations in fish tissue and fish size (length and weight), condition factor, water layer distribution, and trophic level were investigated. Results: Metal concentrations (milligrams per kilogram wet weight) were found to be distributed differently among different fish species. The highest concentrations of Cu (1. 22 mg/kg) and Zn (7. 55 mg/kg) were measured in Pelteobagrus fulvidraco, the highest concentrations of Cd (0. 115 mg/kg) and Hg (0. 0304 mg/kg) were measured in Silurus asotus, and the highest concentrations of Pb (0. 811 mg/kg) and Cr (0. 239 mg/kg) were measured in Carassius auratus and Cyprinus carpio. A positive relationship was found between fish size and metal level in most cases. The variance of the relationships may be the result of differences in habitat, swimming behavior, and metabolic activity. In this study, fishes living in the lower water layer and river bottom had higher metals concentrations than in upper and middle layers. Benthic carnivorous and euryphagous fish had higher metals concentrations than phytoplankton and herbivorous fish. Generally, fish caught from the lower reach had higher metals concentrations than those from the upper reach. Conclusions: Cadmium and lead concentrations in several fishes exceeded the permissible food consumption limits, this should be considered to be an important warning signal. © 2012 Springer-Verlag.


Zhao Z.-Y.,North China Electrical Power University | Sun G.-Z.,North China Electrical Power University | Zuo J.,University of South Australia | Zillante G.,University of Adelaide
Renewable and Sustainable Energy Reviews | Year: 2013

The Chinese wind power industry has achieved remarkable growth in the last two decades. The total installed capacity of wind power in China has now surpassed that of the United States thereby making it the country with the largest installed wind power capacity in the world. The independent and innovative capability of Chinese wind turbine manufacturers has undergone continuous improvement and has now reached the point where the country has the capability to produce large scale wind turbines. Although the Chinese domestic policy incentive has played a significant role in the rapid development of the Chinese wind power industry; the contribution made by external international forces should not be overlooked. This research aims to establish a comprehensive model reflecting the international forces that impact on the Chinese wind power industry. This model consists of three subsystems, i.e. (1) the international cooperation subsystem, (2) the Clean Development Mechanism (CDM) subsystem and (3) the import/export subsystem. Using the model as part of the research, the findings suggest that for the international cooperation subsystem, joint research and development (R&D) and information sharing provide both the finance and the technologies for the entire Chinese wind power industry. The financing impact of CDM certainly guarantees the profitability of wind power projects; however its effect in terms of the diffusion of technical information and technical capability is weak. Similarly, the degree of dependence of Chinese wind turbine manufacturing on imports is weakening as domestic wind turbine manufacturers actively explore overseas markets. This comprehensive model helps both international and domestic wind power investors to understand the impact of international forces on the Chinese wind power industry resulting in better investment decisions and the consequential minimization of risk. © 2013 Elsevier Ltd. All rights reserved.


Liu M.,University of Victoria | Liu M.,Hubei Engineering University | Shi Y.,University of Victoria | Fang F.,University of Victoria | Fang F.,North China Electrical Power University
Applied Energy | Year: 2013

Performance of the combined cooling, heating and power (CCHP) systems depends on the system structure, power flow strategy and the choice of facility capacity. This paper presents a matrix modeling approach to optimize the CCHP system. Modeled in a matrix form, the CCHP system can be viewed as an input-output model. Energy conversion and flow from the system input to the output is modeled by a conversion matrix including the dispatch factors and components efficiencies. By designing the objective function and determining the constraints, the optimization problem of minimizing the evaluation criteria function is solved. Furthermore, the size of the power generation unit (PGU) is also optimized to achieve the optimal performance of the CCHP system. An illustrative case study is conducted to present the effectiveness and economic efficiency of the proposed optimal power flow and operation strategy. © 2012 Elsevier Ltd.


Leng C.,North China Electrical Power University | Wang X.-D.,North China Electrical Power University | Wang T.-H.,North China Electrical Power University | Yan W.-M.,National Taipei University of Technology
Energy Conversion and Management | Year: 2015

In this paper, a three-dimensional solid-fluid conjugate model coupled with a simplified conjugate-gradient method was employed to optimize the performance of double-layered microchannel heat sinks. Channel number, channel width, bottom channel height, and bottom coolant inlet velocity were selected as search variables to achieve the optimal heat sink performance. Firstly, two single-objective optimizations based on different objective functions (one is the maximum temperature change on the bottom wall ΔTw,b and the other is the overall thermal resistance R) were performed at a constant pumping power. Subsequently, the effects of total pumping power on the optimal ΔTw,b and R were analyzed, and the optimal search variables at various pumping powers were obtained. For single-objective optimization with the objective function of ΔTw,b, ΔTw,b is respectively decreased by 6.01, 5.29, and 2.99 K when compared with three original designs. For the objective function of R, however, R is respectively decreased by 36.51%, 15.10%, and 16.67%. The results also indicate that R and ΔTw,b cannot achieve their optimal values simultaneously by the two single-objective optimizations. Thus, a multi-objective optimization was carried out, which demonstrates that when a set of desirable values of ΔTw,b and R is required by designers, the present multi-objective optimization could meet this requirement. © 2015 Elsevier Ltd. All rights reserved.


Dai Z.Y.,Peking University | Li Y.P.,North China Electrical Power University
Agricultural Water Management | Year: 2013

In practical agricultural water management problems, fluctuating water availabilities and demands, varying crop yields and economic profits, as well as changing irrigation patterns in both temporal and spatial scales are challenged decision makers. These challenges are being further compounded by rapid socioeconomic development associated with increased food requirement and decreased resources accessibility. A multistage irrigation water allocation (MIWA) model is developed for agricultural water management and cropland use planning in response to such complexities. The MIWA model is derived from incorporating interval parameters within a multistage stochastic programming (MSP) framework, such that uncertainties expressed as interval parameters and probability distributions can be tackled, and the real-time dynamic irrigation water management can be conducted. It can also support the analysis of various policy scenarios that are associated with different levels of economic consequences when the pre-regulated crop targets are violated over a multistage context. The MIWA model is then applied to a real case of planning agricultural water management and cropland use pattern in Zhangweinan River Basin, which is one of the driest regions in China and faces serious water scarcity. Solutions of irrigation targets for multiple crops as well as actual water-allocation patterns in different growth stages can help determine optimized water and land use in agricultural system, which could hedge appropriately against future available water levels in more profitable and sustainable ways. © 2013 Elsevier B.V.


Shi P.,University of Adelaide | Shi P.,Victoria University of Melbourne | Yin Y.,Jiangnan University | Liu F.,Jiangnan University | Zhang J.,North China Electrical Power University
Information Sciences | Year: 2014

In this paper, a robust H∞ controller is designed for saturated Markov jump systems with uncertainties and time varying transition probabilities. The time-varying transition probability uncertainty is described as a polytope set. Stochastic stability is analyzed for the underlying systems by Lyapunov function approach and a sufficient condition is derived to design controllers such that the resulting closed-loop system is stochastically stable and a prescribed H∞ performance is also achieved. Furthermore, the attraction domain of this Markov jump system is estimated and evaluated. A simulation example is given to show the effectiveness of the developed techniques. © 2013 Elsevier Inc. All rights reserved.


Zhang S.,North China Electrical Power University | Andrews-Speed P.,National University of Singapore | Ji M.,North China Electrical Power University
Energy Policy | Year: 2014

The last twenty years have seen the growth of both solar PV manufacturing capacity and deployment in China, yet this growth has followed a very erratic path. This study applies the concept of socio-technical regime to identify factors which have made this path so erratic. We examine four stages in China's solar PV policy from mid-1990s to 2013 and show that each is characterized by different combinations of policy program. These changes in government policy and in the resultant trajectory of the solar PV sector are attributed to three main sets of variables. The most important of these are events which shape the wider policy priorities of China's government. Secondary factors include the government's poor management of the policy interaction between the domestic solar PV manufacturing industry and the deployment of solar PV across the country, as well as policy learning within government. The general lesson from this study is that the development path of a single element of a national strategy for the low-carbon transition is likely to be erratic, subject as it is to a range of political and economic forces, and to experimentation and learning. © 2014 Elsevier Ltd.


Liu M.,University of Victoria | Shi Y.,University of Victoria | Fang F.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2014

The combined cooling, heating and power (CCHP) system - a typical representative of the decentralized energy system - has been increasingly attracting attention in academia and industries in recent years, thanks to its distinctive advantages of high system and economic efficiency, and less greenhouse gas (GHG) emissions. In this paper, the state of the art of CCHP research is surveyed. First, the development and working scheme of the CCHP system will be presented. Some analyses of the advantages of this system and a brief introduction of the related components are then given in the first part. In the second part of this paper, we elaborately introduce the prime mover and thermally activated facilities. Recent research progress on the management, control, system optimization and sizing will be summarized in the third part. The development of the CCHP system in representative countries and the development barriers will be discussed in the last part. © 2014 Elsevier Ltd.


Liu L.,North China Electrical Power University | Liu L.,Beijing Normal University
Journal of Materials Chemistry C | Year: 2014

We successfully synthesized porous Si nanowire arrays with excellent photoluminescence properties. We found that light irradiation not only promotes the formation of the Si nanowire arrays, but also enhances their porosity. The porous Si nanowire arrays have excellent photoluminescence properties. On moderately doped substrates the porous Si nanowire arrays display a luminescence intensity 11 times greater than that of arrays prepared on the same substrate without light irradiation; on highly doped substrates the luminescence intensity is increased by 1.8 times from that of arrays prepared on the same substrate without light irradiation. In addition, the photoluminescence properties of the as-prepared Si nanowire arrays are stable. These porous Si nanowire arrays may have potential applications in gas sensors, in photocatalysis and in solar cells. This journal is © the Partner Organisations 2014.


Patent
North China Electrical Power University, State Grid Corporation of China and State Grid Shanxi Changzhi Power Supply Company | Date: 2015-01-30

The disclosure relates to the crossing field between a power transmission of an ultra-high-voltage and a power system simulation, specifically a method for analyzing an operation state of a substation by combining a whole grid model with a local grid model is provided according to the disclosure. The method includes following steps: performing a load flow calculation for the provincial grid to which a ultra-high-voltage line belongs, wherein initial data of the load flow calculation employs a grid model with E format for national power grid dispatching control center; making an equivalent transform for the model, forming an island independently from the provincial grid to which a ultra-high-voltage line belongs, and making a load flow calculation for the island to acquire data of node voltages and line transmission power.


Fang F.,North China Electrical Power University | Wang Q.H.,North China Electrical Power University | Shi Y.,University of Victoria
IEEE Transactions on Power Systems | Year: 2012

The operating modes directly influence the system performance of combined cooling, heating and power (CCHP) systems. To improve the comprehensive operational performance, in this paper, based on two typical operating modes, i.e., following the electric load (FEL) and following the thermal load (FTL), a novel optimal operational strategy depending on an integrated performance criterion (IPC) is proposed. Using this strategy, the whole operating space of the CCHP system can be divided into several regions by one to three border surfaces determined by energy requirements and the IPC. Then the operating point of the CCHP system is located in a corresponding operating mode region to achieve improved IPC. The IPC simultaneously considers the primary energy consumption, the operational cost and the carbon dioxide emissions. The carbon tax is also included in the operational cost. A hypothetical hotel building is modeled as the reference system to evaluate the proposed strategy. Simulation results show that, for the same CCHP system of the hypothetical hotel, the IPC with the proposed strategy is better than that with the traditional strategy. The proposed strategy can reflect and balance the influences of energy requirements, energy prices and emissions effectively. © 2012 IEEE.


Dong C.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Cai Y.P.,Beijing Normal University | Cai Y.P.,Environment Canada | Liu Y.,North China Electrical Power University
Energy | Year: 2012

In this study, an inexact optimization modeling approach (IBEM: inexact Beijing energy model) was developed for supporting energy systems planning and air pollution mitigation under uncertainty. This model was based on the integration of multiple inexact optimization techniques, including interval-parameter programming, mixed-integer programming and chance-constrained programming, which make it have strength in dealing with uncertainties presented as both probabilistic distributions and interval numbers. The model could effectively facilitate systematic analysis of complexities associated with energy conversion and utilization, and air pollution mitigation. Particularly, it could help identify optimal patterns of energy resources allocation, as well as capacity expansion options for energy technologies under different air pollution emission reduction schemes. This could not only alleviate air pollution in the city, but also reduce the total system cost that was associated with various energy activities. Based on a two-step solution algorithm, useful solutions were generated, reflecting tradeoffs among environmental and economic conditions, and among different risk violation levels of constraints of the energy system in Beijing city. The interval solutions could then help decision makers identify desired policies for energy management and pollutions reduction. © 2011.


Liu M.,University of Victoria | Shi Y.,University of Victoria | Fang F.,University of Victoria | Fang F.,North China Electrical Power University
Applied Energy | Year: 2012

Performance and economical efficiency of the combined cooling, heating and power (CCHP) system mainly depend on the system structure, operation strategy and choice of facility capacity. This paper proposes a structural configuration of the CCHP system with hybrid chillers, consisting of a combined electric and absorption chiller, whose electric cooling to cool load ratio varies according to different electric and thermal loads in every hour. A new operation strategy, based on the variational electric cooling to cool load ratio, for the CCHP system with unlimited and limited power generation unit (PGU) capacity is investigated. Given the proposed operation strategy, an optimization algorithm is adopted to determine the optimal PGU capacity. In addition, a case study of a hypothetical hotel in Victoria, BC, Canada is conducted to verify the feasibility of the proposed CCHP system structure and the corresponding optimal operation strategy. © 2012 Elsevier Ltd.


Zhao Z.-Y.,North China Electrical Power University | Yan H.,North China Electrical Power University | Zuo J.,University of South Australia | Tian Y.-X.,North China Electrical Power University | Zillante G.,University of Adelaide
Renewable and Sustainable Energy Reviews | Year: 2013

China is facing a number of challenges such as electricity supply shortages, excessive consumption of fossil fuels and environmental pollution. As a renewable energy, wind power plays a vital role in mitigating these issues. With its unique geographical location and rich resources, China has produced a wind power industry that has achieved rapid growth. However, the complex Chinese market environment presents significant challenges to the industry. This research has adopted a strength, weakness, opportunity and threat analysis approach to examine both the internal and external factors that affect the competitiveness of the wind power industry in China. An extensive and critical review of a wide range of literature (including academic papers, industry reports, statistical data, relevant regulations and policy documents) was conducted. As a result, 19 factors were identified. These factors form part of an integrated framework that provides a useful tool for both policy makers and industry to gain a better understanding of what affects the sustainable development of the wind power industry in China. The results also provide a useful reference for foreign firms that intend to explore the Chinese wind power market. © 2012 Published by Elsevier Ltd.


Han Y.,CAS Institute of Physics | Li W.Y.,CAS Institute of Physics | Cao L.X.,CAS Institute of Physics | Wang X.Y.,CAS Institute of Semiconductors | And 4 more authors.
Physical Review Letters | Year: 2010

By realizing in thin films a tensile stress state, superconductivity of 13 K was introduced into FeTe, a nonsuperconducting parent compound of the iron pnictides and chalcogenides, with a transition temperature higher than that of its superconducting isostructural counterpart FeSe. For these tensile stressed films, superconductivity is accompanied by a softening of the first-order magnetic and structural phase transition, and also, the in-plane extension and out-of-plane contraction are universal in all FeTe films independent of the sign of the lattice mismatch, either positive or negative. Moreover, the correlations were found to exist between the transition temperatures and the tetrahedra bond angles in these thin films. © 2010 The American Physical Society.


Zhang X.,KTH Royal Institute of Technology | Yang W.,KTH Royal Institute of Technology | Dong C.,North China Electrical Power University
Journal of Analytical and Applied Pyrolysis | Year: 2013

Levoglucosan is one important primary product during cellulose pyrolysis either as an intermediate or as a product. Three available mechanisms for levoglucosan formation have been studied theoretically in this paper, which are free-radical mechanism; glucose intermediate mechanism; and levoglucosan chain-end mechanism. All the elementary reactions included in the pathway of every mechanism were investigated; thermal properties including activation energy, Gibbs free energy, and enthalpy for every pathway were also calculated. It was concluded that free-radical mechanism has the highest energy barrier during the three levoglucosan formation mechanisms, glucose intermediate mechanism has lower energy barrier than free-radical mechanism, and levoglucosan chain-end mechanism is the most reasonable pathway because of the lowest energy barrier. By comparing with the activation energy obtained from the experimental results, it was also concluded that levoglucosan chain-end mechanism fits better with the experimental data for the formation of levoglucosan. © 2013 Elsevier B.V. All rights reserved.


Liu X.J.,North China Electrical Power University | Kong X.B.,North China Electrical Power University | Hou G.L.,North China Electrical Power University | Wang J.H.,University of Warwick
Energy Conversion and Management | Year: 2013

A thermal power plant is an energy conversion system consisting of boilers, turbines, generators and their auxiliary machines respectively. It is a complex multivariable system associated with severe nonlinearity, uncertainties and multivariable couplings. These characters will be more evident when the system is working at a higher level energy conversion capacity. In many cases, it is almost impossible to build a mathematical model of the system using conventional analytic methods. The paper presents our recent work in modeling of a 1000 MW ultra supercritical once-through boiler unit of a power plant. Using on-site measurement data, two different structures of neural networks are employed to model the thermal power plant unit. The method is compared with the typical recursive least squares (RLSs) method, which obviously demonstrated the merit of efficiency of the neural networks in modeling of the 1000 MW ultra supercritical unit. © 2012 Elsevier Ltd. All rights reserved.


Miao Q.,KTH Royal Institute of Technology | Miao Q.,Shandong Normal University | Liu J.-C.,North China Electrical Power University | Agren H.,KTH Royal Institute of Technology | And 2 more authors.
Physical Review Letters | Year: 2012

X-ray lasing is predicted to ensue when molecules are pumped into dissociative core-excited states by a free-electron-laser pulse. The lasing is due to the population inversion created in the neutral dissociation product, and the process features self-trapping of the x-ray pulse at the gain ridge. Simulations performed for the HCl molecule pumped at the 2p1/2→ 6σ resonance demonstrate that the scheme can be used to create ultrashort coherent x-ray pulses. © 2012 American Physical Society.


Lin Q.G.,Environment Canada | Huang G.H.,University of Regina | Huang G.H.,North China Electrical Power University
Energy | Year: 2010

Energy management systems are highly complicated with greenhouse-gas emission reduction issues and a variety of social, economic, political, environmental and technical factors. To address such complexities, municipal energy systems planning models are desired as they can take account of these factors and their interactions within municipal energy management systems. This research is to develop an interval-parameter two-stage stochastic municipal energy systems planning model (ITS-MEM) for supporting decisions of energy systems planning and GHG (greenhouse gases) emission management at a municipal level. ITS-MEM is then applied to a case study. The results indicated that the developed model was capable of supporting municipal energy systems planning and environmental management under uncertainty. Solutions of ITS-MEM would provide an effective linkage between the pre-regulated environmental policies (GHG-emission reduction targets) and the associated economic implications (GHG-emission credit trading). © 2010 Elsevier Ltd. All rights reserved.


Wang L.,North China Electrical Power University | Gao Y.-T.,Beihang University | Qi F.-H.,Beijing University of Posts and Telecommunications
Annals of Physics | Year: 2012

Under investigation in this paper is a variable-coefficient modified Kortweg-de Vries (vc-mKdV) model describing certain situations from the fluid mechanics, ocean dynamics and plasma physics. N-fold Darboux transformation (DT) of a variable-coefficient Ablowitz-Kaup-Newell-Segur spectral problem is constructed via a gauge transformation. Multi-solitonic solutions in terms of the double Wronskian for the vc-mKdV model are derived by the reduction of the N-fold DT. Three types of the solitonic interactions are discussed through figures: (1) Overtaking collision; (2) Head-on collision; (3) Parallel solitons. Nonlinear, dispersive and dissipative terms have the effects on the velocities of the solitonic waves while the amplitudes of the waves depend on the perturbation term. © 2012 Elsevier Inc.


Wang J.,Argonne National Laboratory | Bloyd C.N.,Pacific Northwest National Laboratory | Hu Z.,State Power Economic Research Institute | Tan Z.,North China Electrical Power University
Energy | Year: 2010

The escalating demand for electricity in China has caused an electricity shortage in the past several years. This paper discusses the role of demand response (DR) as an integral component in alleviating the problem and coping with this shortfall. It reviews current experience with DR programs, analyzes China's situation and makes suggestions for DR implementation. Although China's DR programs offer high potential to succeed, they require substantial efforts in resolving such key issues as the programs' funding mechanisms, pricing, and relationship with electricity industry reform.


Mo L.,Beijing Technology and Business University | Niu Y.,North China Electrical Power University | Pan T.,Beijing Technology and Business University
Physica A: Statistical Mechanics and its Applications | Year: 2015

In this paper, the consensus problem of heterogeneous multi-agent systems with switching jointly-connected interconnection and a leader is considered. Firstly, by a model transformation, the original closed-loop system is turned into an equivalent system. And then, by applying the matrix theory and Lyapunov directed method, the convergence of the multi-agent systems is analyzed, a sufficient condition for consensus of systems is derived when the communication topologies are jointly-connected. Finally, simulation results are provided to demonstrate the effectiveness of presented results. © 2015 Elsevier B.V. All rights reserved.


Zhang Y.M.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Lin Q.G.,Environment Canada | Lu H.W.,North China Electrical Power University
Energy | Year: 2012

In this study, an environmentally friendly model of regional power system was developed to minimize the total cost of a regional power system consisting of an independent power grid. SO 2 emission is controlled and capacity expansion is scheduled. In the system, the deterministic variables represent the power supplied from different energy conversion facilities. The binary variables refer to expansions for electricity conversion facilities, with three options given to each technology. To solve this model, an integer credibility constrained programming (ICCP) is developed by incorporating the concepts of credibility based chance constrained programming and mixed integer programming within an optimization framework. ICCP can explicitly address planning problems and systematic uncertainties without unrealistic simplifications. In application, a comparative benefit motivated electricity production system is proposed without SO 2 control. Results of two cases are compared which show significant effect of emission control. By setting different credibility levels in constraints, it is able to find that the higher the credibility of energy supply satisfying the needs and total SO 2 emission being less than its allowance, and the higher the total energy and lower coal-fired electricity supplies, the higher the total operational costs. © 2011 Elsevier Ltd.


Niu D.,North China Electrical Power University | Wang Y.,North China Electrical Power University | Wu D.D.,University of Toronto | Wu D.D.,Reykjavik University
Expert Systems with Applications | Year: 2010

This paper creates a system for power load forecasting using support vector machine and ant colony optimization. The method of colony optimization is employed to process large amount of data and eliminate redundant information. The system mines the historical daily loading which has the same meteorological category as the forecasting day in order to compose data sequence with highly similar meteorological features. With this method, we reduced SVM training data and overcame the disadvantage of very large data and slow processing speed when constructing SVM model. This paper proposes a new feature selection mechanism based on ant colony optimization in an attempt to combat the aforemention difficulties. The method is then applied to find optimal feature subsets in the fuzzy-rough data reduction process. The present work is applied to complex systems monitoring, the ant colony optimization can mine the data more overall and accurate than the original fuzzy-rough method, an entropy-based feature selector, and a transformation-based reduction method, PCA. Comparing with single SVM and BP neural network in short-term load forecasting, this new method can achieve greater forecasting accuracy. It denotes that the SVM-learning system has advantage when the information preprocessing is based on data mining technology. © 2009 Elsevier Ltd. All rights reserved.


Fan Y.R.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Guo P.,China Agricultural University | Yang A.L.,North China Electrical Power University
Stochastic Environmental Research and Risk Assessment | Year: 2012

In this study, an inexact two-stage stochastic partial programming (ITSPP) method is developed for tackling uncertainties presented as intervals and partial probability distributions. A scenario-based interactive algorithm is proposed to solve the ITSPP model. This algorithm is implemented through: (i) obtaining extreme points of the linear partial information (LPI); (ii) generating an inexact two-stage stochastic programming (ITSP) model under each extreme point; (iii) solving ITSP models through interactive algorithm proposed by Huang and Loucks (Civil Eng Environ Syst 17:95-118, 2000); (iv) acquiring the interval solutions under each extreme point and the final optimal interval for the objective function. The developed method is applied to a case study for water-resources planning. The modelling results can generate a series of decision alternatives under various system conditions, and thus help decision makers identify the desired water-resources management policies under uncertainty. © 2011 Springer-Verlag.


Niu D.,North China Electrical Power University | Liu D.,North China Electrical Power University | Wu D.D.,Reykjavik University
Applied Soft Computing Journal | Year: 2010

Hourly energy prices in a competitive electricity market are volatile. Forecast of energy price is key information to help producers and purchasers involved in electricity market to prepare their corresponding bidding strategies so as to maximize their profits. It is difficult to forecast all the hourly prices with only one model for different behaviors of different hourly prices. Neither will it get excellent results with 24 different models to forecast the 24 hourly prices respectively, for there are always not sufficient data to train the models, especially the peak price in summer. This paper proposes a novel technique to forecast day-ahead electricity prices based on Self-Organizing Map neural network (SOM) and Support Vector Machine (SVM) models. SOM is used to cluster the data automatically according to their similarity to resolve the problem of insufficient training data. SVM models for regression are built on the categories clustered by SOM separately. Parameters of the SVM models are chosen by Particle Swarm Optimization (PSO) algorithm automatically to avoid the arbitrary parameters decision of the tester, improving the forecasting accuracy. The comparison suggests that SOM-SVM-PSO has considerable value in forecasting day-ahead price in Pennsylvania-New Jersey-Maryland (PJM) market, especially for summer peak prices. © 2009 Elsevier B.V. All rights reserved.


Shen W.,North China Electrical Power University | Guo X.,North China Electrical Power University | Wu C.,University of Waterloo | Wu D.,University of Toronto | Wu D.,Reykjavik University
Knowledge-Based Systems | Year: 2011

Stock index forecasting is a hot issue in the financial arena. As the movements of stock indices are non-linear and subject to many internal and external factors, they pose a great challenge to researchers who try to predict them. In this paper, we select a radial basis function neural network (RBFNN) to train data and forecast the stock indices of the Shanghai Stock Exchange. We introduce the artificial fish swarm algorithm (AFSA) to optimize RBF. To increase forecasting efficiency, a K-means clustering algorithm is optimized by AFSA in the learning process of RBF. To verify the usefulness of our algorithm, we compared the forecasting results of RBF optimized by AFSA, genetic algorithms (GA) and particle swarm optimization (PSO), as well as forecasting results of ARIMA, BP and support vector machine (SVM). Our experiment indicates that RBF optimized by AFSA is an easy-to-use algorithm with considerable accuracy. Of all the combinations we tried in this paper, BIAS6 + MA5 + ASY4 was the optimum group with the least errors. © 2010 Elsevier B.V. All rights reserved.


Wang Y.,North China Electrical Power University | Liu J.,Beihang University
International Journal of Advanced Manufacturing Technology | Year: 2013

Assembly sequence planning is a typical of NP-complete problem which will spend a large amount of computation time or disk memory once the assembly becomes complex. The complex product or assembly is composed of many parts and the number of assembly relationships between them is numerous. To decrease the difficulty of assembly sequence planning of complex products, the subassembly identification methods are focused on. It aims to decompose a complex assembly into a limitative number of subassemblies. Each subassembly contains a relatively smaller number of parts and the assembly sequence planning tasks of them can be handled efficiently. The subassembly identification methods for assembly sequence planning are summarized with respect to assembly constraints. The assembly constraints including the topological, geometrical, and process constraints are considered and merged into the assembly models for subassembly identification. The assembly models are generally represented as directed or undirected assembly diagrams including these considered constraints. It is generally taken as the input information to generate appropriate subassemblies complying with the requirements. The graph theories and graph search algorithms, integer programming methods and the emerging techniques, such as the knowledge-based methods, the intelligent algorithms and the virtual technology, etc. are advocated to resolve the subassembly identification problem with respect to the assembly models. The hierarchical assembly tree is widely used to represent the results of subassembly identification. These useful methods are not only used to subassembly identification for assembly sequence planning, but also successfully referred to by product disassembly. © 2013 Springer-Verlag London.


Niu D.-X.,North China Electrical Power University | Shi H.-F.,North China Electrical Power University | Wu D.D.,University of Toronto | Wu D.D.,Reykjavik University
Applied Soft Computing Journal | Year: 2012

This paper presents a short term load forecasting model based on Bayesian neural network (shorted as BNN) learned by the Hybrid Monte Carlo (shorted as HMC) algorithm. The weight vector parameter of the Bayesian neural network is a multi-dimensional random variable. In learning process, the Bayesian neural network is considered as a special Hamiltonian dynamical system, and the weights vector as the system position variable. The HMC algorithm is used to learn the weight vector parameter with respect to Normal prior distribution and Cauchy prior distribution, respectively. The Bayesian neural networks learned by Laplace algorithm and HMC algorithm and the artificial neural network (ANN) learned by the BP algorithm were used to forecast the hourly load of 25 days of April (Spring), August (Summer), October (Autumn) and January (Winter), respectively. The roots mean squared error (RMSE) and the mean absolute percent errors (MAPE) were used to measured the forecasting performance. The experimental result shows that the BNNs learned by HMC algorithm have far better performance than the BNN learned by Laplace algorithm and the neural network learned BP algorithm and the BNN learned by HMC has powerful generalizing capability, it can welly solve the overfitting problem. © 2011 Elsevier B.V. All rights reserved.


Yao X.,Beihang University | Yao X.,North China Electrical Power University | Guo L.,Beihang University
Automatica | Year: 2013

This paper is concerned with the problems of composite disturbance- observer-based control (DOBC) and H∞ control for Markovian jump systems with nonlinearity and multiple disturbances. Our aim is to design a disturbance observer to estimate the disturbance generated by an exogenous system, then construct the control scheme by integrating the output of the disturbance observer with state-feedback control law, such that, the closed-loop system can be guaranteed to be stochastically stable, and different types of disturbances can be attenuated and rejected. By constructing a proper stochastic Lyapunov-Krasovskii functional, sufficient conditions for the existence of the desired observer and the state-feedback controller are established in terms of linear matrix inequalities (LMIs), which can be readily solved by standard numerical software. Finally, a numerical example is provided to show the effectiveness of the proposed approaches. © 2013 Elsevier Ltd. All rights reserved.


Feng Y.,Monash University | Li X.,North China Electrical Power University | Shao Z.,Nanjing University of Technology | Wang H.,Monash University
Journal of Materials Chemistry A | Year: 2015

In this study, the electrochemical performance of hollow Zn2GeO4 nanoparticles as an anode material for lithium-ion batteries (LIBs) has for the first time been investigated and compared to other morphology-type Zn2GeO4 materials with a solid nanorod structure. The results show that the lithium-storage performance is morphology-dependent and the presence of hollow voids is beneficial to enhance the charge-discharge capacity at different current densities. Specifically, the capacity of hollow Zn2GeO4 nanoparticles is approximately 200 mA h g-1 higher than that of Zn2GeO4 solid nanorods after 60 discharge-charge cycles at a current density of 200 mA h g-1 and such high performance (ca. 1200 mA h g-1) is in the front rank of current anode materials and three times as high as that of commercial graphite-based anodes (372 mA h g-1). Moreover, hollow Zn2GeO4 nanoparticles show better rate capacity and the specific capacity is approximately 300 mA h g-1 higher at a current density of 2000 mA h g-1 in comparison with Zn2GeO4 nanorods. The hollow voids not only lower the charge transfer resistance by facilitating lithium-ion diffusion, but also effectively buffer against local volume changes. Therefore, considering the easy and environmentally friendly synthesis and the high performance (high reversible capacity and good rate capacity), such hollow Zn2GeO4 nanoparticles are a very promising candidate as a high-performance anode material for LIBs. © 2015 The Royal Society of Chemistry.


Cho Y.J.,Gyeongsang National University | Saadati R.,Islamic Azad University at Tehran | Wang S.,North China Electrical Power University | Wang S.,Gyeongsang National University
Computers and Mathematics with Applications | Year: 2011

In this paper, we introduce a concept of the c-distance in a cone metric space and, by using the concept of the c-distance, prove some fixed point theorems in ordered cone metric spaces. © 2010 Elsevier Ltd. All rights reserved.


Lv M.,CAS Chengdu Institute of Organic Chemistry | Li S.,North China Electrical Power University | Jasieniak J.J.,CSIRO | Hou J.,CAS Beijing National Laboratory for Molecular | And 5 more authors.
Advanced Materials | Year: 2013

An alcohol-soluble hyperbranched conjugated polymer HBPFN with a dimethylamino moiety is synthesized and used as a cathode interlayer. A PCE of 7.7% is obtained for PBDTTT-C-T/PC71BM based solar cells. No obvious interfacial dipole is found at the interface between the active layer and HBPFN however, an interfacial dipole with the cathode could be one of the reasons for the enhanced performance. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhao Z.-Y.,North China Electrical Power University | Zhang S.-Y.,China Electric Power Research Institute | Hubbard B.,Purdue University | Yao X.,Beijing Association for Electrical Power Industry
Renewable and Sustainable Energy Reviews | Year: 2013

Solar photovoltaic (PV) power is a new and green energy source. China has significant opportunities for solar energy utilization with its huge solar resource. The solar PV power in China has developed for 50 years, and experienced a rapid progress in the last 10 years. To address the needs of the fast growth of the PV power industry in China, it is critical to identify, analyze and understand the growth path and the characteristics of the industry. This paper summarizes the status of the solar energy resources and the development of the solar PV power industry in China, and puts forward the main factors that impacted the development of the industry. A study refers to the selected five main factors the factors are: technology research and development, industrial plans, laws and regulations, electricity price policies, and projects incentive policies. A multifaceted approach including literature survey, statistical data investigation, law review, and regulation and policy study are adopted to investigate these factors. Analysis of the typical events, the growth process and the characteristics of the five factors, allows the establishment of growth route models. The results can be a useful reference for the development of solar PV power industry in China and other countries. © 2013 Published by Elsevier Ltd.


Lin Z.,North China Electrical Power University | Liu J.,North China Electrical Power University | Zhang W.,Shandong University of Science and Technology | Niu Y.,North China Electrical Power University
Automatica | Year: 2011

This paper considers the stabilization problems for interconnected nonlinear stochastic Markovian jump systems from the viewpoint of dissipativity theory. Based on the strongly stochastic passivity theory, the feedback equivalence and global stabilization problems are studied for interconnected nonlinear stochastic Markovian jump systems. The strongly stochastic γ-dissipativity sustains a direct H∞ control for this class of systems instead of solving coupled HamiltonJacobi inequalities. © 2011 Elsevier Ltd. All rights reserved.


Liu N.,North China Electrical Power University | Chen J.,China Electric Power Research Institute | Zhu L.,Tianjin Normal University | Zhang J.,North China Electrical Power University | He Y.,Fujian Shuikou Hydropower Generation Company
IEEE Transactions on Industrial Electronics | Year: 2013

Advanced metering infrastructure (AMI) is an important component of the smart grid. The cyber security should be considered prior to the AMI system applications. To ensure confidentiality and integrality, a key management scheme (KMS) for a large amount of smart meters (SMs) and devices is required, which is not a properly solved problem until now. Compared with other systems, there are three specific features of AMI that should be carefully considered, including hybrid transmission modes of messages, storage and computation constraints of SMs, and unfixed participators in demand response (DR) projects. In order to deal with security requirements and considering the distinctive features, a novel KMS is proposed. First, the key management framework of an AMI system is constructed based on the key graph. Furthermore, three different key management processes are designed to deal with the hybrid transmission modes, including key management for unicast, broadcast, and multicast modes. Relatively simple cryptographic algorithms are chosen for key generation and refreshing policies due to the storage and computation constraints of SMs. Specific key refreshing policies are designed since the participators in a certain DR project are not fixed. Finally, the security and performance of the KMS are analyzed. According to the results, the proposed scheme is a possible solution for AMI systems. © 1982-2012 IEEE.


Xin Y.,North China Electrical Power University | Li Y.,Beihang University | Liu Z.,North China Electrical Power University
Scripta Materialia | Year: 2010

The effect of thermal cycling on the microstructure, martensitic transformation behavior and shape memory characteristic of the dual-phase Ni58Mn25Ga17 high-temperature shape memory alloy was investigated. The Ni58Mn25Ga17 alloy showed high thermal stability upon cycling up to 500 thermal cycles between 298 and 923 K without obvious differences in its microstructure and martensitic transformation behavior. Shape memory strain decreased slightly after 500 thermal cycles but remained over 2.6%. © 2010 Acta Materialia Inc.


Gu Y.,Tsinghua University | Zhao W.,North China Electrical Power University | Wu Z.,Tsinghua University
Journal of Process Control | Year: 2011

Boiler combustion optimization is a key measure to improve the energy efficiency and reduce pollutants emissions of power units. However, time-variability of boiler combustion systems and lack of adaptive regression models pose great challenges for the application of the boiler combustion optimization technique. A recent approach to address these issues is to use the least squares support vector machine (LS-SVM), a computationally attractive machine learning technique with rather legible training processes and topologic structures, to model boiler combustion systems. In this paper, we propose an adaptive algorithm for the LS-SVM model, namely adaptive least squares support vector machine (ALS-SVM), with the aim of developing an adaptive boiler combustion model. The fundamental mechanism of the proposed algorithm is firstly introduced, followed by a detailed discussion on key functional components of the algorithm, including online updating of model parameters. A case study using a time-varying nonlinear function is then provided for model validation purposes, where model results illustrate that adaptive LS-SVM models can fit variable characteristics accurately after being updated with the ALS-SVM method. Based on the introduction to the proposed algorithm and the case study, a discussion is then delivered on the potential of applying the proposed ALS-SVM method in a boiler combustion optimization system, and a real-life fossil fuel power plant is taken as an instance to demonstrate its feasibility. Results show that the proposed adaptive model with the ALS-SVM method is able to track the time-varying characteristics of a boiler combustion system. © 2011 Elsevier Ltd.


He L.,Chinese Academy of Sciences | Wang G.Q.,Tsinghua University | Zhang C.,North China Electrical Power University
Journal of Environmental Informatics | Year: 2012

Insufficient flow and excessive sediment supply in the Middle Yellow River lead to persistent sedimentation and rising flood levels in the lower river channel. Better understanding of the relationship between sediment erosion, transportation, and deposition can help in the decision making of soil and water conservation in the Coarse Sediment Source Area (CSSA) and sediment reduction works in the lower channel. A linked simulation can help elucidate the interrelationship. The goal of the current research is to simulate the whole sediment process from the CSSA to the downstream channels of the Yellow River. To achieve this goal, we use the Digital Yellow River Model (DYRM), a watershed hydrology and sediment yield and transportation model plate, coupled with a one-dimensional (1D) unsteady model for the hyper-concentrated sediment-laden flow in complex sections, to study the sedimentation process in the entire watershed. The performance of the simulation of flood in year 1977 was evaluated using the percent bias, Nash-Sutcliffe statistics of the residuals, and percentage difference. Simulation of the sediment process in 1977 shows that linked simulation can describe the hydrographs of discharge and sediment concentrations, especially flood in the downstream main channels. Compared with the underestimated discharge and sediment load in the main channel, the discharge of most tributaries is verestimated, whereas most of the sediment load is underestimated. The inconsistency indicates that more efforts are required to conduct better simulation, including data input and data processing, and both DYRM and 1D models. © 2012 ISEIS All rights reserved.


Li Z.,Tsinghua University | Liu Y.,North China Electrical Power University | Cai N.,Tsinghua University
Fuel | Year: 2014

The steam-enhanced carbonation reaction of CaO with CO2 is a widely observed phenomenon, but its mechanism is unclear. This study proposed that OH- formation caused by the dissociation of H2O molecules may explain enhanced carbonation. The relationship of oxygen vacancies with OH- at different temperatures and steam fractions was established and integrated into a new carbonation model. This new model included a simplified rate equation model to describe product island formation and a multi-ion diffusion model that describes product layer growth. Experiments on carbonation and sorption-enhanced water gas shift reactions in a laboratory-scale fluidized bed reactor were conducted to validate the idea of OH- formation. The new developed models were validated by thermogravimetric analysis. ©2013 Elsevier Ltd. All rights reserved.


Yu H.,Tsinghua University | Liu D.,Tsinghua University | Duan Y.,Tsinghua University | Wang X.,North China Electrical Power University
Optics Express | Year: 2014

Opacified aerogels are particulate thermal insulating materials in which micrometric opacifier mineral grains are surrounded by silica aerogel nanoparticles. A geometric model was developed to characterize the spectral properties of such microsize grains surrounded by much smaller particles. The model represents the material's microstructure with the spherical opacifier's spectral properties calculated using the multi-sphere T-matrix (MSTM) algorithm. The results are validated by comparing the measured reflectance of an opacified aerogel slab against the value predicted using the discrete ordinate method (DOM) based on calculated optical properties. The results suggest that the large particles embedded in the nanoparticle matrices show different scattering and absorption properties from the single scattering condition and that the MSTM and DOM algorithms are both useful for calculating the spectral and radiative properties of this particulate system. © 2014 Optical Society of America.


Zhao J.-J.,Tsinghua University | Duan Y.-Y.,Tsinghua University | Wang X.-D.,North China Electrical Power University | Wang B.-X.,Tsinghua University
International Journal of Heat and Mass Transfer | Year: 2012

The radiative properties and heat transfer in fiber-loaded silica aerogel composites were investigated using modified anomalous diffraction theory in a combined heat conduction and radiation model. The randomly parameterized 2-D fiber distribution was generated to simulate a very realistic material structure. The finite volume method was then used to solve a two flux radiation model and the steady-state energy equation to calculate the effective thermal conductivity of the composite. The numerical results provide theoretic guidelines for material designs with optimum parameters, such as the inclination angle, diameter and length-to-diameter ratio of the fibers. The results show that the fiber extinction coefficient increases as the fiber length-to-diameter ratio is reduced or the fiber inclination angle is increased. The effective thermal conductivity of the fiber-loaded aerogel can be reduced by reducing the fiber length-to-diameter ratio and the inclination angle and by moderately increasing the fiber volume fraction. The 4-6 μm diameter silicon fibers are optimum for high-temperature thermal insulation. © 2012 Elsevier Ltd. All rights reserved.


Wang X.,Jilin University | Li Y.,North China Electrical Power University
Journal of Hazardous Materials | Year: 2011

Clay minerals in surficial sediment samples, collected from the Songhua River in China, were separated via sedimentation after removal of Fe/Mn oxides and organic materials; Cu and Zn adsorption onto the sediment components was then evaluated. Clay minerals were examined via X-ray diffraction and scanning electron microscopy. Clay minerals were found to consist mainly of illite, kaolinite, chlorite and an illite/smectite mixed layer. Non-clay minerals were dominated by quartz and orthoclase. The retention of Cu and Zn by clay minerals was 1.6 and 2.5 times, respectively, greater than that of the whole, untreated surficial sediment. Compared to the other critical components in sediments related to metal sorption (Mn oxides, Fe oxides and organic materials), the adsorption capacity of clay minerals was found to be relatively lower on a unit mass basis. These data suggest that, although clay minerals may be important in the adsorption of heavy metals to aquatic sediments, their role is less significant than Fe/Mn oxides and organic materials. © 2011 Elsevier B.V.


Wang X.-X.,Tsinghua University | Li C.-R.,North China Electrical Power University
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In order to have a better understanding of the homogeneous dielectric barrier discharge in nitrogen at atmospheric pressure, we summarized the related results mainly from our experiments. It is found that, even with the help of a nitrogen flow through the discharge gap, the homogenous discharge can only be produced in a gap shorter than 3 mm., which is identified to be a Townsend discharge and is extinguished in an extraordinary manner, i.e., the discharge is extinguished while the gap voltage continues to increase. The electrons trapped in and released from the shallow traps on the dielectric surface are important for initiating and maintaining the Townsend discharge. The explanation of the effect of the nitrogen flow on the homogenous discharge based on "laminar flow" is proved to be incorrect. The role played by the nitrogen flow in the formation of the Townsend discharge is to reduce the density of oxygen from impurity, which significantly prolongs the lifetime of the metastable nitrogen molecule N2(A). N2(A) is suggested to be responsible for releasing the shallowly trapped electrons from the dielectric surface by bombardment, which provides the Townsend discharge with a sufficient amount of the seed electrons.


Yu H.-T.,Tsinghua University | Liu D.,Tsinghua University | Duan Y.-Y.,Tsinghua University | Wang X.-D.,North China Electrical Power University
International Journal of Heat and Mass Transfer | Year: 2014

Opacified silica aerogels are composite insulating materials containing silica nanoparticles and microsize opacifier grains. The radiative heat transfer in this dispersed medium was analyzed using a realistic microstructure model to calculate the opacified aerogel's optical properties. The aerogel matrices were simulated using aggregates generated by a DLA algorithm, where the particle sizes and numbers were determined from the basic physical parameters. The theoretical predictions of the aerogel's optical parameters agreed well with experimental data. A geometric unit containing one opacifier particle and a large number of aerogel particles was then built to study the coupled radiation effect between the aerogel and the opacifier. The optical parameters were computed using a multi-sphere T-matrix code with comparisons with Mie scattering solutions. The results show how the opacifier's modified optical properties reduce the aerogel's radiative conductivity.


Zhao Z.-Y.,North China Electrical Power University | Wu P.-H.,North China Electrical Power University | Xia B.,Queensland University of Technology | Skitmore M.,Queensland University of Technology
Renewable and Sustainable Energy Reviews | Year: 2014

Wind power is one of the worlds major renewable energy sources, and its utilization provides an important contribution in helping solve the energy problems of many countries. After nearly 40 years of development, Chinas wind power industry now not only manufactures its own massive six MW turbines but also has the largest capacity in the world with a national output of 50 million MW h in 2010 and set to rise by eight times of that amount by 2020. This paper investigates this development route by analyzing relevant academic literature, statistics, laws and regulations, policies and research and industry reports. The main drivers of the development in the industry are identified as technologies, turbines, wind farm construction, pricing mechanism and government support systems, each of which is also divided into different stages with distinctive features. A systematic review of these aspects provides academics and practitioners with a better understanding of the history of the wind power industry in China and reasons for its rapid development with a view to enhancing progress in wind power development both in China and the world generally. © 2014 Published by Elsevier Ltd.


Wang X.-D.,North China Electrical Power University | An B.,North China Electrical Power University | Lin L.,University of Science and Technology Beijing | Lee D.-J.,National Taiwan University of Science and Technology | Lee D.-J.,National Taiwan University
Applied Thermal Engineering | Year: 2013

An inverse geometric optimization for nanofluid-cooled microchannel heat sink (MCHS) considering effects of temperature-dependent thermophyiscal properties for the water-based Al2O3 nanofluid with 1% particle volume fraction was performed under a constant pumping power constraint. A three-dimensional fluid-solid conjugated MCHS model combining the simplified-conjugate-gradient-method was used as the optimization tool. The channel number, N, the channel aspect ratio, α, and the width ratio of channel to pitch, β, affect the cooling performance of MCHS, and were all incorporated in the present, three-parameter optimization study. Increase in viscosity of the nanofluid did not always lead to enhanced MCHS performance under fixed pumping power constraint, contradicting to the results for pure water. The optimal MCHS design is closely related to the assigned pumping power: increase in the pumping power enhances cooling performance; however, in high pumping power regime the performance enhancement is not as effective as in low pumping power regime. At pumping power of 0.05 W and a uniform heat flux of qw = 100 W cm-2, the optimal design for the nanofluid-cooled MCHS presented N = 51, α = 5.69 and β = 0.62, yielding the optimal thermal resistance of RT = 0.1059 K W -1. © 2013 Elsevier Ltd. All rights reserved.


Chen K.-P.,North China Electrical Power University | Zhang X.-W.,Tsinghua University
Ceramics International | Year: 2010

CaCu3Ti4O12 has a giant dielectric constant of up to 104 at room temperature and has great potential for various technological applications. In this work, CaCu3Ti 4O12 ceramic powder was synthesized by heating a stoichiometric amount of CaCO3, CuO and TiO2 in molten NaCl-KCl and Na2So4-K2So4, respectively. The synthesis temperature was decreased from 1000 °C (required by conventional solid-state reactions) to 750 °C for NaCl-KCl or to 850 °C for Na2So4-K2So4. The flux type has a larger influence on the phase compositions and morphology of the resultant powders than the synthesis temperature does. The dielectric constant of the resulting ceramics is more than 104 over the wide frequency range from 100 Hz to 100 kHz. The dielectric loss tangent of the resulting ceramics is lower than 0.2 in the frequency range from 100 Hz to 100 kHz. The dielectric behavior of both samples is similar to the results obtained for CaCu 3Ti4O12 ceramics that were synthesized by the sol-gel method. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


Sun W.,Tsinghua University | Sun W.,North China Electrical Power University
Construction and Building Materials | Year: 2011

In this study, the shape memory alloy (SMA) restrainer bars utilized to reduce the seismic response of arch dams with vertical contraction joints were investigated. The SMA damper model and the nonlinear behavior of arch dams affected by contraction joint opening/closing during earthquakes were simulated in ANSYS. Moreover, the nonlinear damping control principle and method were discussed. The effectivity of the SMA restrainer bars in arch dams was assessed through comparing with a traditional measure of reinforced steel across contraction joints. The SMA restrainer bars were effective in limiting the relative openings of the contraction joints and reducing the seismic acceleration. In addition, the new SMA vibration damper devices of arch dams are simple and easy to install. © 2011 Elsevier Ltd. All rights reserved.


Wang C.,Bohai University | Chen D.,North China Electrical Power University
Computers and Mathematics with Applications | Year: 2010

It is a useful method in research of group theory to construct a new group by using known groups. Lower and upper approximation operators of rough sets are applied into group theory and so the notion of a rough group has been introduced. In this paper, we first point out that there are still some incomplete propositions in [N. Kuroki, P.P. Wang, The lower and upper approximations in a fuzzy group, Inform. Sci. 90 (1996) 203-220] although some authors have showed several incorrect statements in the literature. We then present improved versions of the incomplete propositions and continue to study the image and inverse image of rough approximations of a subgroup with respect to a homomorphism between two groups. © 2009 Elsevier Ltd. All rights reserved.


Zhang G.,University of Technology, Sydney | Zhang G.,North China Electrical Power University | Gao Y.,University of Technology, Sydney | Lu J.,University of Technology, Sydney
IEEE Transactions on Industrial Electronics | Year: 2011

Competitive strategic bidding optimization is now a key issue in electricity generator markets. Digital ecosystems provide a powerful technological foundation and support for the implementation of the optimization. This paper presents a new strategic bidding optimization technique which applies bilevel programming and swarm intelligence. In this paper, we first propose a general multileader-one-follower nonlinear bilevel (MLNB) optimization concept and related definitions based on the generalized Nash equilibrium. By analyzing the strategic bidding behavior of generating companies, we create a specific MLNB decision model for day-ahead electricity markets. The MLNB decision model allows each generating company to choose its biddings to maximize its individual profit, and a market operator can find its minimized purchase electricity fare, which is determined by the output power of each unit and the uniform marginal prices. We then develop a particle-swarm-optimization-based algorithm to solve the problem defined in the MLNB decision model. The experiment results on a strategic bidding problem for a day-ahead electricity market have demonstrated the validity of the proposed decision model and algorithm. © 2010 IEEE.


Wang C.,Bohai University | Chen D.,North China Electrical Power University | Sun B.,Harbin Institute of Technology | Hu Q.,Harbin Institute of Technology
Information Sciences | Year: 2012

Communication between information systems is considered as an important issue in granular computing. The concept of homomorphism is an effective mathematical tool to study information exchange between information systems. This paper provides a study on some basic properties of covering information systems and decision systems under homomorphisms. First, we define consistent functions related to coverings and covering mappings between two universes, and study their properties. Then, we introduce the notions of homomorphisms of covering information systems and point out that a homomorphism is a special covering mapping between information systems. Furthermore, we investigate some important properties of homomorphisms in covering information systems and decision systems. It is proved that some basic properties of original systems, such as set approximations, attribute reductions, can be reserved under the condition of homomorphisms in both covering information systems and covering decision systems. © 2012 Elsevier Inc. All rights reserved.


Wang C.,Bohai University | He Q.,Hebei University | Chen D.,North China Electrical Power University | Hu Q.,Tianjin University
Information Sciences | Year: 2014

Attribute reduction has become an important step in pattern recognition and machine learning tasks. Covering rough sets, as a generalization of classical rough sets, have attracted wide attention in both theory and application. This paper provides a novel method for attribute reduction based on covering rough sets. We review the concepts of consistent and inconsistent covering decision systems and their reducts and we develop a judgment theorem and a discernibility matrix for each type of covering decision system. Furthermore, we present some basic structural properties of attribute reduction with covering rough sets. Based on a discernibility matrix, we develop a heuristic algorithm to find a subset of attributes that approximate a minimal reduct. Finally, the experimental results for UCI data sets show that the proposed reduction approach is an effective technique for addressing numerical and categorical data and is more efficient than the method presented in the paper [D.G. Chen, C.Z. Wang, Q.H. Hu, A new approach to attribute reduction of consistent and inconsistent covering decision systems with covering rough sets, Information Sciences 177(17) (2007) 3500-3518]. © 2013 Elsevier Inc. All rights reserved.


Zhang T.,North China Electrical Power University | Zhang G.,University of Technology, Sydney | Lu J.,University of Technology, Sydney | Feng X.,North China Electrical Power University | Yang W.,HOHHOT Power Supply Company
IEEE Transactions on Power Systems | Year: 2012

Conducting load pattern analysis is an important task in obtaining typical load profiles (TLPs) of customers and grouping them into classes according to their load characteristics. When using clustering techniques to obtain the load patterns of electricity customers, choosing a suitable clustering algorithm and determining an appropriate cluster number are always important and difficult issues. Therefore, this paper proposes a stability index for choosing the most suitable clustering algorithm and a priority index (based on the stability index) for determining the priority rank of clusters. Based on three known clustering algorithms, an analysis approach is presented to demonstrate the use of these indices. In the approach, all load curves of customers are first clustered with the clustering algorithms under a serial given number of clusters. The two above-mentioned indices are then calculated. Following this, the most suitable clustering algorithm is chosen and the optimal number of clusters can be determined from the rank list for special application purposes. A case study with large electricity customers connected to a distribution network in Northern China illustrates the approach. The results prove the efficiency of the approach using the proposed indices in the classification and generation of the TLPs of large electricity customers. © 2006 IEEE.


Wang C.,Bohai University | Chen D.,North China Electrical Power University | Wu C.,Harbin Institute of Technology | Hu Q.,Harbin Institute of Technology
International Journal of Approximate Reasoning | Year: 2011

In reality we are always faced with a large number of complex massive databases. In this work we introduce the notion of a homomorphism as a kind of tool to study data compression in covering information systems. The concepts of consistent functions related to covers are first defined. Then, by classical extension principle the concepts of covering mapping and inverse covering mapping are introduced and their properties are studied. Finally, the notions of homomorphisms of information systems based on covers are proposed, and it is proved that a complex massive covering information system can be compressed into a relatively small-scale information system and its attribute reduction is invariant under the condition of homomorphism, that is, attribute reductions in the original system and image system are equivalent to each other. © 2010 Elsevier Inc. All rights reserved.


Ma M.-M.,Jilin University | Ma M.-M.,North China Electrical Power University | Chen H.,Jilin University
IET Control Theory and Applications | Year: 2011

This study suggests an approach to design an active suspension controller with non-linear actuator dynamics, which can achieve good ride comfort while respecting safety constraints such as road holding and limited suspension strokes. The procedure includes two steps: design a state feedback ∞ controller for the linear subsystem with time-domain constraints, and then apply the backstepping technique to deal with non-linear actuator dynamics and to derive the control law. The closed-loop system achieves a bounded disturbance attenuation level (the l2 gain), which gives a measure of ride comfort in the case of general road disturbances. Simulation results are provided to show the effectiveness of the designed controller. © 2011 The Institution of Engineering and Technology.


Zhang Y.,North China Electrical Power University | Du X.,North China Electrical Power University | Xian H.,North China Electrical Power University | Wu Y.,Tsinghua University
Ultrasonics Sonochemistry | Year: 2015

Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency is theoretically investigated. The critical bubble radii dividing stable and unstable regions of bubbles under dual-frequency acoustic excitation are strongly affected by the amplitudes of dual-frequency acoustic excitation rather than the frequencies of dual-frequency excitation. The limitation of the proposed model is also discussed with demonstrating examples. © 2014 Elsevier B.V. All rights reserved.


Xu J.,North China Electrical Power University | Sun J.-L.,Tsinghua University | Wei J.,Tsinghua University
Applied Physics Letters | Year: 2012

Hetrodimensional contacts were fabricated by coating double-walled carbon nanotube (CNT) films on CuO nanowire arrays. Wavelength dependent photovoltaic effects by irradiating the devices with 405, 532, and 1064 nm lasers were observed. Two possible mechanisms responsible for the observed results were discussed. Photoexcitations within CuO nanowires and Schottky barriers in the heterojunctions dominate the photovoltaics in the 405 and 532 nm cases. For the 1064 nm case, the photovoltaic is the result of the excitation within the CNTs and of the heterodimensionality effect. Control experiments on CNT film/CuO granular film hetrodimensional contacts further show the relationship between these two mechanisms. © 2012 American Institute of Physics.


Gao X.,North China Electrical Power University | Gao Y.,Tsinghua University | Ralescu D.A.,University of Cincinnati
International Journal of Uncertainty, Fuzziness and Knowlege-Based Systems | Year: 2010

Liu's inference is a process of deriving consequences from uncertain knowledge or evidence via the tool of conditional uncertainty. Using membership functions, this paper derives some expressions of Liu's inference rule for uncertain systems. This paper also discusses Liu's inference rule with multiple antecedents and with multiple if-then rules. © 2010 World Scientific Publishing Company.


Kang J.,North China Electrical Power University | Yuan J.,North China Electrical Power University | Yuan J.,University of Michigan | Hu Z.,North China Electrical Power University | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2012

Since 2005, there has been dramatic progress in China's wind power industry. The annual growth rate of newly constructed capacity reached a miracle of 105% and the total installed capacity has increased from 1.27 GW in 2005 to 44.73 GW in 2010, which has exceeded the target of China's energy long-term planning for 2020. During the 11th Five-Year-Plan (FYP), the Chinese government has issued a series of polices to promote and regulate the development of wind power industry, which is the underlying force driving its rapid development. This paper is a systematical review on the current status and policies of wind power industry in China. Firstly the current status including achievements and shortcomings is presented, and then the relevant polices and regulations released during the period of 11th FYP are reviewed. Meanwhile, the main approaches of the policies and regulations in promoting the development of wind power industry are discussed and the issues of the current policies are analyzed. Finally, the paper concludes on the perspectives of wind power policies in China. © 2012 Elsevier Ltd. All rights reserved.


Xie L.,North China Electrical Power University | Khargonekar P.P.,University of Florida
Automatica | Year: 2012

This paper is concerned with an adaptive state estimation problem for a class of nonlinear stochastic systems with unknown constant parameters. These nonlinear systems have a linear-in-parameter structure, and the nonlinearity is assumed to be bounded in a Lipschitz-like manner. Using stochastic counterparts of Lyapunov stability theory, we present adaptive state and parameter estimators with ultimately exponentially bounded estimator errors in the sense of mean square for both continuous-time and discrete-time nonlinear stochastic systems. Sufficient conditions are given in terms of the solvability of LMIs. Moreover, we also introduce a suboptimal design approach to optimizing the upper bound of the mean-square error of parameter estimation. This suboptimal design procedure is also realized by LMI computations. By a martingale method, we also show that the related Lyapunov function has a non-negative Lyapunov exponent. © 2012 Elsevier Ltd. All rights reserved.


Guo W.,North China Electrical Power University | Zhang H.,North China Electrical Power University | Huo S.,Chinese Research Academy of Environmental Sciences
Ecological Engineering | Year: 2014

The levels of 13 organochlorine pesticides (OCPs) in the sediments obtained from Baiyangdian wetland in China were determined to evaluate the effect of aquatic hydrophytes, Ceratophyllum demersum, Phragmites, and Typha, on the distribution of OCPs in the wetland sediments. The total OCP concentration in the sediments was in the range 3.60-11.12ngg-1 on a dry weight basis. The surface sediment concentrations were higher than those near the roots of aquatic hydrophytes. Dichlorodiphenyltrichloroethanes predominated in the sediments. The OCP concentration in the plant tissues was in the range 4.72-11.19ngg-1 on a dry weight basis with the highest concentration in Phragmites leaves. Under the water, the plant tissues in the roots accumulated more OCPs than those in the stems. The relationship between the OCP octanol-water partitioning coefficient and bioconcentration factor in these media indicated that less hydrophobic hexachlorocyclohexane and endosulfans were more easily accumulated and transported in plant tissues. Compared to the other two aquatic plants, Phragmites showed more effective OCP removal from the sediments in the wetland. © 2014 Elsevier B.V.


Zhou G.,North China Electrical Power University | He J.,North China Electrical Power University | He J.,China Academy of Building Research
Applied Energy | Year: 2015

Experiments were carried out to investigate the performance of a low-temperature radiant floor heating system with different heat storage materials (sand and phase change material) and heating pipes (polyethylene coils and capillary mat) in the floor structure of a test room. Detailed temperatures in both floor structural layers and the air of the room were measured for four different combinations of these thermal mass and heating pipes during charge and discharge operations. The results showed that the floor structure with capillary mat provides more uniform temperature profile in vertical direction of the test room and needs much shorter time (nearly half) to attain the same room temperature than the cases with polyethylene (PE) coils during the charging process. Also, after the heat source was closed, the floor structures using phase change material (PCM) as thermal mass release heat about 2 times longer than the cases using sand. A CFD simulation is also performed which confirms the measured data during the charging and discharging processes. The results indicate the advantages of using PCM - capillary mat combination for low - temperature floor panel typical of solar - hot - water heating system. © 2014 Elsevier Ltd.


Yuan J.,North China Electrical Power University | Xu Y.,North China Electrical Power University | Hu Z.,State Grid Corporation of China
Energy Policy | Year: 2012

This paper studies the transition to low carbon power systems in China. The methodology is built on the newly developed multi-level perspective (MLP) transitions, as well as literature on innovation systems. Three lines of thought on the transition process are integrated to probe the possible transition pathways in China's power sector. Five transition pathways, namely reproduction, transformation, substitution, reconfiguration, de-alignment/re-alignment and reconfiguration, with their possible technology options are presented. The requirements for a smart grid in the socio-technical transition process are addressed within the MLP framework. The paper goes further to propose an interactive framework for low carbon transition management in China. Representative technology options are appraised by employing innovation theory to demonstrate the logic of policy design within the framework. The work presented in this paper will be useful in informing policy-makers and other stakeholders in China and it may prove to be a valuable reference for other countries in energy transition management. © 2012 Elsevier Ltd.


Zhu Y.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Li Y.P.,North China Electrical Power University | He L.,North China Electrical Power University | Zhang X.X.,State Grid Corporation of China
Applied Energy | Year: 2011

In this study, an interval full-infinite mixed-integer municipal-scale energy model (IFMI-MEM) is developed for planning energy systems of Beijing. IFMI-MEM is based on an integration of existing interval-parameter programming (IPP), mixed-integer linear programming (MILP) and full-infinite programming (FIP) techniques. IFMI-MEM allows uncertainties expressed as determinates, crisp interval values and functional intervals to be incorporated within a general optimization framework. It can also facilitate capacity-expansion planning for energy-production facilities within a multi-period and multi-option context. Then, IFMI-MEM is applied to a real case study of energy systems planning in Beijing. The results indicate that reasonable solutions have been generated. They are helpful for supporting (a) adjustment of the existing demand and supply patterns of energy resources, (b) facilitation of dynamic analysis for decisions of capacity expansion and/or development planning, and (c) coordination of the conflict interactions among economic cost, system efficiency, pollutant mitigation and energy-supply security. © 2011 Elsevier Ltd.


Qian D.,North China Electrical Power University | Yi J.,CAS Institute of Automation | Liu X.,North China Electrical Power University
Proceedings of the American Control Conference | Year: 2011

This paper investigates modeling and control problems of the speed governing system of a hydro-generator unit with one upstream surge tank, driven by a Francis turbine. This governing system is organized into four main functional blocks, namely the hydrodynamic, mechanical, electrical, and servo subsystems. Mathematic models of the individual components are developed and are subsequently interconnected to obtain a model for the governor design. From the viewpoint of modern control theory, only a part of states of this speed governing system are measurable. By introducing an additional state variable, a reduced order sliding mode controller is presented. Simulation results illustrate the feasibility and robustness of the presented method. © 2011 AACC American Automatic Control Council.


Chen D.,North China Electrical Power University | Hu Q.,Harbin Institute of Technology | Yang Y.,North China Electrical Power University
Information Sciences | Year: 2011

Fuzzy rough sets are considered as an effective tool to deal with uncertainty in data analysis, and fuzzy similarity relations are used in fuzzy rough sets to calculate similarity between objects. On the other hand in kernel tricks, a kernel maps data into a higher dimensional feature space where the resulting structure of the learning task is linearly separable, while the kernel is the inner product of this feature space and can also be viewed as a similarity function. It has been reported there is an overlap between family of kernels and collection of fuzzy similarity relations. This fact motivates the idea in this paper to use some kernels as fuzzy similarity relations and develop kernel based fuzzy rough sets. First, we consider Gaussian kernel and propose Gaussian kernel based fuzzy rough sets. Second we introduce parameterized attribute reduction with the derived model of fuzzy rough sets. Structures of attribute reduction are investigated and an algorithm with discernibility matrix to find all reducts is developed. Finally, a heuristic algorithm is designed to compute reducts with Gaussian kernel fuzzy rough sets. Several experiments are provided to demonstrate the effectiveness of the idea. © 2011 Elsevier Inc. All rights reserved.


Yuan J.,North China Electrical Power University | Hu Z.,North China Electrical Power University | Hu Z.,State Grid Corporation of China
Renewable and Sustainable Energy Reviews | Year: 2011

Low carbon electricity is essential for China's low carbon development. In the paper low carbon electricity is defined as an economy body manages to realize its potential economic growth fueled by less electricity consumption, which can be characterized by indexes of GDP electricity intensity and CO 2 emissions per unit electricity generation. IRSP is proposed by Hu [11] to implement power planning on state level in deregulated power sector and is used in the paper to study China's power planning into 2030. A business-as-usual scenario is projected as baseline for comparison while low carbon electricity development based on IRSP is studied. Results show that, with IRSP, China could save energy by 1.5 billion toes and reduce CO2 emission by 5.7 billion tons, during 2010-2030. Super Smart Grid (SSG) must be constructed as the physical foundation of IRSP. The main components of developing SSG in China are discussed. © 2011 Elsevier Ltd. All rights reserved.


Yuan J.,North China Electrical Power University | Kang J.,North China Electrical Power University | Yu C.,Energy Research Institute | Hu Z.,North China Electrical Power University | Hu Z.,State Grid Corporation of China
Renewable and Sustainable Energy Reviews | Year: 2011

Energy conservation (EC) has been taken as basic state policy in China for more than 20 years and China achieves 3.9% annual energy saving from 1980 to 2005. In 2006 China Central Government firstly set up a binding target of reducing GDP energy intensity by 20% in its 11th Five-Year-Plan (FYP). At the end of 2010, 19.1% reduction in energy intensity has been achieved, which is 95% of the target and means 608 million tons stand coal equivalence (sce) saved, 1510 million tons CO2 emission reduced, 300 billion RMB¥ saving in energy bill and vast saving in infrastructure investment. This paper is systematical review and prospective analysis on energy policy issue in China. Review on policy evolution and progress of EC and Emission Reduction (ER) in China during the 11th FYP periods is presented in detail. Outlook of energy demand and supply into 2050 is presented and the roadmap to realize sustainable energy development is drafted to set the framing constraints for Chinas energy policy options. Rationality and feasibility analysis on newly formulated 12th FYP EC and ER target is also addressed. Then lessons from the 11th FYP periods are drawn and factors underlying and limiting the policy formulation and implementation are discussed in details to probe the policy predicament and solutions. Finally policy suggestions are proposed for long-term successful implementation of EC and ER in China. © 2011 Elsevier Ltd. All rights reserved.


Yao X.,North China Electrical Power University | Wu L.,Harbin Institute of Technology | Zheng W.X.,University of Western Sydney
IEEE Transactions on Signal Processing | Year: 2011

This paper addresses the problem of fault detection filter design for discrete-time Markovian jump singular systems with intermittent measurements. The measurement transmission from the plant to the fault detection filter is assumed to be imperfect and a stochastic variable is utilized to model the phenomenon of data missing. Our attention is focused on the design of a fault detection filter such that the residual system is stochastically Markovian jump admissible and satisfies some expected performances. A new necessary and sufficient condition for a class of discrete-time Markovian jump singular systems to be stochastically Markovian jump admissible is proposed in the form of strict linear matrix inequalities. Sufficient conditions are established for the existence of the fault detection filter. Finally, a numerical example is provided to demonstrate the usefulness and applicability of the developed theoretical results. © 2011 IEEE.


He Q.,Harbin Institute of Technology | Wu C.,Harbin Institute of Technology | Chen D.,North China Electrical Power University | Zhao S.,Hebei University
Knowledge-Based Systems | Year: 2011

Fuzzy rough set is a generalization of crisp rough set to deal with data sets with real value attributes. A primary use of fuzzy rough set theory is to perform attribute reduction for decision systems with numerical conditional attribute values and crisp (symbolic) decision attributes. In this paper we define inconsistent fuzzy decision system and their reductions, and develop discernibility matrix-based algorithms to find reducts. Finally, two heuristic algorithms are developed and comparison study is provided with the existing algorithms of attribute reduction with fuzzy rough sets. The proposed method in this paper can deal with decision systems with numerical conditional attribute values and fuzzy decision attributes rather than crisp ones. Experimental results imply that our algorithm of attribute reduction with general fuzzy rough sets is feasible and valid. © 2010 Elsevier B.V. All rights reserved.


Qian D.,North China Electrical Power University | Yi J.,CAS Institute of Automation
International Journal of Control and Automation | Year: 2013

In industries, overhead cranes are commonly employed to lift and lower materials or to move them horizontally. A combining sliding mode control method is proposed for overhead crane systems in this paper. The ideas behind the combining sliding mode are as follows. First, an intermediate variable is introduced by dividing the system states into two groups. Then, a sliding surface is defined on basis of the intermediate variable. The control law is deduced from Lyapunonv direct method to asymptotically stabilize the sliding surface. The stability of the system states is also proven. Simulation results demonstrate the feasibility of the presented method through transport control of an overhead crane system.


Sun C.-P.,North China Electrical Power University | Yang X.,A Cheng Relay Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

A classification and recognition method for power quality disturbances based on module time-frequency matrixes by S transform is proposed. The corn of it is that, at first, module time-frequency matrix by S transform is used to indicate the characteristics of power quality distrubance, the standard mode of various distrubances is established on the base of probability density of magnitude of module time-frequency matrix, and then considering euclidean distance between distrubances and standard mode, the degree of similarity can be calculated, and disturbances are classified. And detection precision is also acceptable. The simulation results show that the approach has better anti-interference performance, and classification results in the condition of low SNR and detection precision are also acceptable.


Gu C.,University of Bath | Li F.,University of Bath | He Y.,North China Electrical Power University
IEEE Transactions on Power Systems | Year: 2012

This paper improves the existing long-run incremental cost (LRIC) pricing which forms the basis for one of the two common charging methodologies that are to be adopted by the U.K.'s seven distribution network operators for charging customers connected at extra-high voltage (EHV) distribution networks from April 2012. The original model is expected to respect network security while evaluating charges based on the extent of the use of the network, which it achieves by reshaping components' capacity with their contingency factors into maximum available capacity. It then identifies the impact of a nodal injection on each component under normal conditions within the threshold of the maximum available capacity. The problem with the LRIC is that it assumes that the impact from a nodal injection is the same under both normal and contingent states, thus underestimating its impact under contingencies. In this paper, the original LRIC model is improved by considering the respective impacts from users under both normal and contingent conditions. The improved model runs incremental contingency flow analysis to determine how they affect components' flows under contingencies. In order to illustrate the differences in the reinforcement horizons, a comparison of the original and enhanced approaches is carried out on three basic distribution networks: single-branch, parallel-branch, and meshed. The new approach chooses the smaller horizons between those from normal and contingent situations to derive charges. Sensitivity analysis is introduced to reduce the calculation burden in determining components' flowincrements due to injections. The improved approach is finally testified and compared with the original model on a threebusbar system and a practical system. © 2006 IEEE.


Zhu Y.,North China Electrical Power University | Fan X.,State Grid Electric Power Research Institute of China
International Journal of Electrical Power and Energy Systems | Year: 2013

As very little research on the fault location for multi-terminal transmission lines based on current traveling waves only has been done, a new fault location scheme on this is proposed. The proposed scheme is different from the traditional ones based on fundamental impedance. Fast Intrinsic Mode Decomposition (FIMD) and Teager Energy Operator (TEO) are combined (FIMD&TEO) to detect the arrival time of the traveling wave at each terminal. Fault Distance Ratio Matrix (FDRM) and rules for identifying faulted sections of a multi-terminal transmission line are proposed and the method for building FDRM is presented in this paper. After several couples of local and remote terminals connecting through the faulted section are got, their fault distances are calculated by means of a two-ended traveling wave method, and then the fault point can be located by averaging the fault distances. Many simulations under various fault conditions have been done, and the results show that the proposed scheme can locate faults more accurately than existing impedance-based methods. © 2013 Elsevier Ltd. All rights reserved.


Zhou D.,North China Electrical Power University | Shen X.,North China Electrical Power University | Dong W.,CAS Institute of Automation
IET Image Processing | Year: 2012

Image-zooming is a technique of producing a high-resolution image from its low-resolution counterpart. It is also called image interpolation because it is usually implemented by interpolation. Keys' cubic convolution (CC) interpolation method has become a standard in the image interpolation field, but CC interpolates indiscriminately the missing pixels in the horizontal or vertical direction typically incurs blurring, blocking, ringing or other artefacts. In this study, the authors propose a novel edge-directed CC interpolation scheme which can adapt to the varying edge structures of images. The authors also give an estimation method of the strong edge for a missing pixel location, which guides the interpolation for the missing pixel. The authors' method can preserve the sharp edges details of images with notable suppression of the artefacts that usually occur with CC interpolation. The experiment results demonstrate that the authors'method outperforms significantly CC interpolation in terms of both subjective objective measures. © 2012 The Institution of Engineering Technology.


Chen B.,Beijing Institute of Technology | Zhong H.,Beijing Institute of Technology | Zhang W.,North China Electrical Power University | Tan Z.,North China Electrical Power University | And 6 more authors.
Advanced Functional Materials | Year: 2012

The off-stoichiometry effects and gram-scale production of luminescent CuInS 2-based semiconductor nanocrystals, as well as their application in electroluminescence devices are reported. The crystal structures and optical properties of CuInS 2 nanocrystals can be significantly influenced by controlling their [Cu]/[In] molar ratio. A simple model adapted from the bulk materials is proposed to explain their off-stoichiometry effects. Highly emissive and color-tunable CuInS 2-based NCs are prepared by a combination of [Cu]/[In] molar ratio optimization, ZnS shell coating, and CuInS 2-ZnS alloying. The method is simple, hassle-free, and easily scalable to fabricate tens of grams of nanocrystal powders with photoluminescence quantum yields up to around 65%. Furthermore, the performance of high-quality CuInS 2-based NCs in electroluminescence devices is examined. These devices have lower turn-on voltages of around 5 V, brighter luminance up to approximately 2100 cd m -2 and improved injection efficiency of around 0.3 lm W -1 (at 100 cd m -2) in comparison to recent reports. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wu L.,Harbin Institute of Technology | Yao X.,North China Electrical Power University | Yao X.,University of Western Sydney | Zheng W.X.,University of Western Sydney
Automatica | Year: 2012

This paper is concerned with the generalized H 2 fault detection for two-dimensional (2-D) discrete-time Markovian jump systems. The mathematical model of the 2-D system is established upon the well-known Roesser model, and the measurement missing phenomenon, which appears typically in a network environment, is modeled by a stochastic variable satisfying the Bernoulli random binary distribution. In addition, the transition probabilities of the Markovian jump process are assumed to be partly accessed, that is, the transition probabilities are partly known. Our attention is focused on the design of a fault detection filter, or a residual generation system, which guarantees the fault detection system to be mean-square asymptotically stable and to have a prescribed generalized H 2 performance. Sufficient conditions for the existence of a desired fault detection filter are established in terms of linear matrix inequalities (LMIs). A numerical example is provided to illustrate the effectiveness of the proposed design method. © 2012 Elsevier Ltd. All rights reserved.


Zhao S.,Renmin University of China | Wang X.,Hebei University | Chen D.,North China Electrical Power University | Tsang E.C.C.,Macau University of Science and Technology
Information Sciences | Year: 2013

In this paper, by strict mathematical reasoning, we discover the relationship between the parameters and the reducts in parameterized rough reduction. This relationship, named the nested reduction, shows that the reducts act as a nested structure with the monotonically increasing parameter. We present a systematic theoretical framework that provides some basic principles for constructing the nested structure in parameterized rough reduction. Some specific parameterized rough set models in which the nested reduction can be constructed are pointed out by strict mathematical reasoning. Based on the nested reduction, we design several quick algorithms to find a different reduct when one reduct is already given. Here 'different' refers to the reducts obtained on the different parameters. All these algorithms are helpful for quickly finding a proper reduct in the parameterized rough set models. The numerical experiments demonstrate the feasibility and the effectiveness of the nested reduction approach. © 2013 Elsevier Inc. All rights reserved.


Patent
State Grid Corporation of China, Gansu Electric Power Company and North China Electrical Power University | Date: 2014-04-16

The present invention has disclosed a wind power bundling control method after wind power and thermal power are connected to a power grid in the field of electric power system security technology, including regulating wind power output and thermal power output forward or backward; calculating the transient stability margin of the grid, load level index of element and voltage out-of-limit index of busbar after regulating wind power output and thermal power output respectively; calculating wind power/thermal power paying value according to the transient stability margin of the grid, load level index of element and voltage out-of-limit index of busbar after regulating wind power output and thermal power output; if wind power/thermal power paying value is larger than set threshold value, regulating wind power output and thermal power output backward/forward; if wind power/thermal power paying value is smaller than set threshold value, regulating wind power output and thermal power output forward/backward. The present invention provides a wind power bundling control method after wind power and thermal power are connected to the power grid to ensure reasonable output of wind power and thermal power, so as to guarantee the power grid operates normally.


Patent
State Grid Corporation of China, Gansu Electric Power Company and North China Electrical Power University | Date: 2014-04-18

The present invention has disclosed an optimal control method for reactive voltage of wind power and photovoltaic power centralized grid connection in the field of wind power and photovoltaic power grid connection control technology, comprising: setting actuating stations used to control single wind power plant/photovoltaic power plant, setting substations used to control actuating stations and set master station used to control all the substations; master station calculates setting voltage reference U_(ref )of each substation; adopting 3 method to process set voltage reference U_(ref )to obtain set voltage reference interval; regulating high-side voltage of substation to make it fall in set voltage reference interval; if high-side voltage of substation does not fall in set voltage reference interval, then regulating the equipment in wind power plant/photovoltaic power plant via actuating station. The present invention guides the actual operations of electric power system.


Patent
State Grid Corporation of China, North China Electrical Power University and STATE GRID LIAONING Electrical POWER COMPANY Ltd ECONOMIC RESEARCH INSTITUTE | Date: 2014-07-26

A renewable energy-based hybrid bi-directionally interactive DC traction power supply system includes two traction substations. Each substation includes transformers, rectifiers, bidirectional AC-DC converters, a DC bus, a catenary, a steel rail and a section post. A DC bus between two adjacent traction substations is provided with a DC renewable energy system constructed by an electric vehicle charging-discharging system, a distributed generation and more than one low voltage DC microgrid. The DC renewable energy system is connected to the DC bus between two adjacent traction substations through a high voltage DC bus, thus a DC circular microgrid being formed in a power supply section post. The electric vehicle charging-discharging system is formed by more than one bidirectional DC-DC charging-discharging equipments which are intended for in connection with the power batteries of the electric vehicle. The renewable energy-based hybrid bi-directionally interactive DC traction power supply system of the invention realizes effective usage of distributed generation and recycling of electric locomotive braking energy, reducing DC voltage fluctuation, thus improving reliability of the DC traction power supply system.


Li Y.,North China Electrical Power University | Li Y.,CAS Institute of Engineering Thermophysics | Zhang N.,CAS Institute of Engineering Thermophysics | Cai R.,CAS Institute of Engineering Thermophysics
Energy | Year: 2013

Based on the principle of cascade utilization of multiple energy resources, a gas-steam combined cycle power system integrated with solar thermo-chemical fuel conversion and CO2 capture has been proposed and analyzed. The collected solar heat at 550°C drives the endothermic methane reforming and is converted to the produced syngas chemical exergy, and then released as high-temperature thermal energy via combustion for power generation, achieving its high-efficiency heat-power conversion. The reforming reaction is integrated with a hydrogen separation membrane, which continuously withdraws hydrogen from the reaction zone and enables nearly full methane conversion. The CO2 enriched gas being concentrated in the retentate zone is collected and processed with pre-combustion decarbonization.The system is thermodynamically simulated using the ASPEN PLUS code. The results show that with 91% CO2 captured, the specific CO2 emission is 25g/kWh. An exergy efficiency of 58% and thermal efficiency of 51.6% can be obtained. A fossil fuel saving ratio of 31.2% is achievable with a solar thermal share of 28.2%, and the net solar-to-electricity efficiency based on the gross solar heat incident on the collector is about 36.4% compared with the same gas-steam combined cycle system with an equal CO2 removal ratio obtained by post-combustion decarbonization. © 2013 Elsevier Ltd.


Li B.,North China Electrical Power University | Ji L.,CAS Institute of Engineering Thermophysics
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

In order to study the complex movement and the mixing of particle in fluidized bed better, the gas-solid two-phase flow in the single spouted fluidized bed was stmulated in two space dimensions by the soft-sphere model of discrete element method in Euler-Lagrange coordinate system. The particle phase was simulated by discrete element method, and the gas phase by the algorithm of SIMPLER. The gas-solid phase built coupling model by Newton third law and the calculation was carried out by using FORTRAN program. Heat transfer, combustion and particles' rotation were neglected. The simulation obtained the movement and mixing of particles in the top and bottom layers, velocity of gas-solid in different heights and particle concentration distribution. The results show that the back-mixing of intensive particles and internal recycle phenomenon are existed in fluidized bed under the influence of the air jet. There is a certain particle concentration gradient in the horizontal and vertical direction. The number of particle collisions is also different. The higher of the particle concentration is in the place the intenser of the particle collisions and mixing are. © 2012 Chinese Society for Electrical Engineering.


Yuan J.,North China Electrical Power University | Shen J.,North China Electrical Power University | Pan L.,North China Electrical Power University | Zhao C.,North China Electrical Power University | Kang J.,Nuclear Power Institute of China
Renewable and Sustainable Energy Reviews | Year: 2014

Smart grid is the direction of power system development and it has aroused wide attention. It is also the physical infrastructure to integrate renewable energy into the power system. In China power grid companies are the pioneer in developing smart grids. Propelled by strong demand, China has made encouraging progress in smart grid development, especially in the aspect of ultra-high voltage transmission system. However, in other aspects as distributed generation, microgrid and intelligent demand management etc., the progress is slow and limited. In this paper we analyze the policy, pilot projects, achievements and barriers of developing smart grids in China. We find that lack of a clear national strategy is one main institutional barrier. The current industrial structure of the electric power sector, or the vertical integration of power transmission with distribution and supply, is another institutional barrier. Finally we provide an outlook on smart grid development in China. © 2014 Elsevier Ltd.


Li H.,Hunan University | Lei J.,North China Electrical Power University | Liu Q.,CAS Institute of Engineering Thermophysics
International Journal of Heat and Mass Transfer | Year: 2012

The inverse heat conduction problems (IHCP) analysis method provides an efficient approach for estimating the thermophysical properties of materials, the boundary conditions, or the initial conditions. Successful applications of the IHCP method depend mainly on the efficiency of the inversion algorithms. In this paper, a generalized objective functional, which has been developed using a generalized stabilizing functional and a combinational estimation that integrates the advantages of the least trimmed squares (LTS) estimation and the M-estimation, is proposed. The objective functional unifies the regularized M-estimation, the regularized least squares (LS) estimation, the regularized LTS estimation, the regularized combinational estimation of the LTS estimation and the M-estimation, and the regularized combinational estimation of the LS estimation and the M-estimation into a concise formula. The filled function method, which is coupled with the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, is developed for searching a possible global optimal solution. Numerical simulations are implemented to evaluate the feasibility and effectiveness of the proposed algorithm. Favorable numerical performances and satisfactory results are observed, which indicates that the proposed algorithm is successful in solving the IHCP. © 2012 Elsevier Ltd. All rights reserved.


Meng M.,North China Electrical Power University | Niu D.,North China Electrical Power University | Shang W.,Hebei University
Energy | Year: 2014

Mitigating the impact of developing countries to global climate change has become an important issue in the fields of science and politics. This study proposes a small-sample hybrid model for forecasting the energy-related CO2 emissions of developing countries. The CO2 emissions of these countries have not reached the inflection point of the long-term S-shaped curve and usually present short-term linear or approximately exponential trends. This concern is considered in the design of a hybrid forecasting equation combined by a nonhomogeneous exponential equation and a linear equation. The estimated parameters of the hybrid equation are obtained by minimizing the residual sum of squares and solving for a non-constrained optimization equation. To evaluate the performance of the hybrid model, the traditional linear model, GM (grey model) (1, 1), and the hybrid model are used to forecast the CO2 emissions of China from 1992 to 2011. Analysis of forecasting results shows that the hybrid model can respond more quickly to changes in emission trends than can the two models because of the specialized equation structure. Overall error analysis indicators also show that hybrid model often obtains more precise forecasting results than do the other two models. © 2013 Elsevier Ltd.


Chen D.,North China Electrical Power University | He Q.,Hebei University | Wang X.,Hebei University
Fuzzy Sets and Systems | Year: 2010

This paper aims to improve hard margin support vector machines (SVMs) by considering the membership of every training sample in constraints. The membership is computed by employing the technique of fuzzy rough sets so that hard margin SVMs can be combined with fuzzy rough sets and the inconsistence between conditional features and decision labels can be taken into account at the same time. In this paper, we first propose fuzzy transitive kernel based fuzzy rough sets. For binary classification, we use a lower approximation operator in fuzzy transitive kernel based fuzzy rough sets to compute the membership for every training input. And then we reformulate hard margin support vector machines into fuzzy rough set based SVMs (FRSVMs) with new constraints in which the membership is taken into account. Finally, comparisons with soft margin SVMs and fuzzy SVMs are made. The experimental results show that the proposed approach is feasible and valid. It significantly improved the performance of the hard margin SVMs. © 2009 Elsevier B.V. All rights reserved.


Degang C.,North China Electrical Power University | Suyun Z.,Hebei University
Fuzzy Sets and Systems | Year: 2010

One important and valuable topic in fuzzy rough sets is attribute reduction of decision system. The existing attribute reductions with fuzzy rough sets consider all decision classes together and cannot identify key conditional attributes explicitly for special decision class. In this paper we introduce the concept of local reduction with fuzzy rough sets for decision system. The local reduction can identify key conditional attribute and offer a minimal description for every single decision class. Approach of discernibility matrix is employed to investigate the structure of local reduction. At last, several experiments are performed to show that the idea of local reduction is feasible and valid. © 2009 Elsevier B.V. All rights reserved.


Meng M.,North China Electrical Power University | Niu D.,North China Electrical Power University | Shang W.,Hebei University
Energy Policy | Year: 2012

For the period of the 12th Five-Year Plan (2011-2015), the Chinese government has decided to reconsider and adjust its policies on economic development because of the pressures of CO 2 emissions and fossil energy consumption. The current paper adopts the logarithmic Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model to simulate the relationship between CO 2 emissions and other economic development factors in China. Three groups of outliers are found using samples from 1989 to 2008 and the Partial Least Square (PLS) regularity test method. The outlier analysis reveals three important areas for CO 2 reduction: (a) decreasing the share of coal to the total energy consumption and replacing it with non-fossil energies; (b) controlling vehicles used in the cities as well as (c) adjusting industrial structure. Furthermore, based on the social and economic realities of China, the current paper designs six feasible development scenarios for the period covered by the 12th Five-Year Plan and predicts the values of each factor in each scenario. The values can test the implementation of China's CO 2 control development concept. The experiences obtained by outlier analysis can be of significant reference value for realizing the predicted scenarios. © 2011 Elsevier Ltd.


Wang J.-J.,North China Electrical Power University | Wang J.-J.,CAS Institute of Engineering Thermophysics | Yang K.,North China Electrical Power University | Xu Z.-L.,North China Electrical Power University | Fu C.,North China Electrical Power University
Applied Energy | Year: 2015

Biomass-fueled combined cooling, heating, and power (CCHP) system is a sustainable distributed energy system to reduce fossil energy consumption and carbon dioxide emission. This study proposes a biomass CCHP system that contains a biomass gasifier, a heat pipe heat exchanger for recovering waste heat from product gas, an internal combustion engine to produce electricity, an absorption chiller/heater for cooling and heating, and a heat exchanger to produce domestic hot water. Operational flows are presented in three work conditions: summer, winter, and the transitional seasons. Energy and exergy analyses are conducted for different operational flows. The case demonstrated that the energy efficiencies in the three work conditions are 50.00%, 37.77%, and 36.95%, whereas the exergy efficiencies are 6.23%, 12.51%, and 13.79%, respectively. Destruction analyses of energy and exergy indicate that the largest destruction occurs in the gasification system, which accounts for more than 70% of the total energy and exergy losses. Annual performance shows that the proposed biomass-fueled CCHP system reduces biomass consumption by 4% compared with the non-use of a heat recovery system for high-temperature product gas. © 2015 Elsevier Ltd.


Fan W.,Hebei University | Zhang X.,North China Electrical Power University | Dong L.,Hebei University
Physics of Plasmas | Year: 2010

A series of two-dimensional plasma photonic crystals have been obtained by filaments' self-organization in atmospheric dielectric barrier discharge with two water electrodes, which undergo the transition from square to square superlattice and finally to the hexagon. The spatio-temporal behaviors of the plasma photonic crystals in nanosecond scale have been studied by optical method, which show that the plasma photonic crystal is actually an integration of different transient sublattices. The photonic band diagrams of the transverse electric (TE) mode and transverse magnetic mode for each sublattice of these plasma photonic crystals have been investigated theoretically. A wide complete band gap is formed in the hexagonal plasma photonic crystal with the TE mode. The changes of the band edge frequencies and the band gap widths in the evolvement of different structures are studied. A kind of tunable plasma photonic crystal which can be controlled both in space and time is suggested. © 2010 American Institute of Physics.


Wu K.,North China Electrical Power University | Zhou H.,North China Electrical Power University | An S.,North China Electrical Power University | Huang T.,Shanghai Municipal Electric Power Company
Energy Conversion and Management | Year: 2015

An optimal coordinate operation control method for large-scale wind-photovoltaic (PV)-battery storage power generation units (WPB-PGUs) connected to a power grid with rated power output was proposed to address the challenges of poor stability, lack of decision-making, and low economic benefits. The "rainflow" calculation method was adopted to establish the battery cycle life model and to calculate quantitatively the life expectancy loss in the operation process. To minimize unit cost of power generation, this work optimized the output period of the equipment and strategy of battery charging and discharging with consideration of working conditions, generation equipment characteristics, and load demand by using the enhanced gravitational search algorithm (EGSA). A case study was conducted on the basis of data obtained using WPB-PGU in Zhangbei, China. Results showed that the proposed method could effectively minimize the unit cost of a WPB-PGU under different scenarios and diverse meteorological conditions. The proposed algorithm has high calculation accuracy and fast convergence speed. © 2014 Elsevier Ltd. All rights reserved.


Zhang R.,Mid Sweden University | Hummelgrd M.,Mid Sweden University | Lv G.,North China Electrical Power University | Olin H.,Mid Sweden University
Carbon | Year: 2011

A real time method for monitoring the drug load and release on graphene oxide (GO) in a cuvette is reported using rhodamine B (RB) as a model for a drug. The mechanisms of the release of RB at different pH were investigated, by monitoring the time dependency of the accumulative drug release. In vitro real time experimental results indicated that RB could be loaded on GO with a capacity of 0.5 mg/mg. The drug release of RB was pH sensitive as observed at pH 7.4 and pH 4.5 PBS solutions. The higher pH values lead to weaker hydrophobic force and hydrogen bonds, and thus higher release rate. The ionic strength also influenced the release of RB, as shown from the different release rates between PBS solutions and double distilled water. These results indicated a case II transport process at pH 7.4 and an anomalous diffusion process at pH 4.5 and in water. The method described here allows real time detection of the drug release rate, in contrast to common dialysis analysis. This method also points to other real time detections in biomedical investigations. © 2010 Elsevier Ltd. All rights reserved.


Huang Y.-X.,North China Electrical Power University | Huang Y.-X.,National Chung Cheng University | Wang X.-D.,North China Electrical Power University | Cheng C.-H.,National Cheng Kung University | Lin D.T.W.,National University of Tainan
Energy | Year: 2013

This paper develops an inverse problem approach to optimize the geometric structure of TECs (thermoelectric coolers). The approach integrates a complete multi-physics TEC model and a simplified conjugate-gradient method. The present TEC model couples the heat and electrical conductions and accounts for all physical mechanisms occurred within TECs. Three geometric parameters, the semiconductor pair number, N, leg length of semiconductor column, Hpn, and base area ratio of semiconductor columns to TEC, γ, are optimized simultaneously at fixed current and fixed temperature difference. The cooling rate on the cold end is the objective function to be maximized to obtain the optimal TEC geometry. The effects of applied current and temperature difference on the optimal geometry are discussed. The results show that at temperature difference of 20K, the geometry optimization increases the TEC cooling rate by 1.99-10.21 times compared with the initial TEC geometry, and the optimal N decreases from 100 to 47 with invariable γ=0.95 and Hpn=0.2mm, as the applied current varies from 1.0A to 3.0A. With the increase in temperature difference, the optimal N increases at smaller currents of I≤1.0A, however, it is almost invariable at larger currents of I≥1.5A. © 2013 Elsevier Ltd.


Liu T.,North China Electrical Power University | Xu G.,North China Electrical Power University | Cai P.,Yantai Longyuan Power Technology Co. | Tian L.,North China Electrical Power University | Huang Q.,North China Electrical Power University
Renewable Energy | Year: 2011

CO2 emissions of the electricity supply sector in China account for about half of the total volume in the country. Thus, reducing CO2 emissions in China's electricity supply sector will contribute significantly to the efforts of greenhouse gas (GHG) control in the country and the rest of the world. This paper introduces the development status of renewable energy and other main CO2 mitigation options in power generation in China and makes a preliminary prediction of the development of renewable energy in the country for future decades. Besides, based on the situation in China, the paper undertakes a comprehensive analysis of CO2 mitigation costs, mitigation potential, and fossil energy conversation capacity of renewable energy and other mitigation options, through which the influence of renewable energy on the mitigation strategy of China is analyzed. © 2010 Elsevier Ltd.


Hung T.-C.,Military Academy | Yan W.-M.,National University of Tainan | Yan W.-M.,Research Center for Energy Technology and Strategy | Wang X.-D.,North China Electrical Power University | Huang Y.-X.,National Cheng Kung University
International Journal of Heat and Mass Transfer | Year: 2012

This work uses an optimization procedure consisting of a simplified conjugate-gradient method and a three-dimensional fluid flow and heat transfer model to investigate the optimal geometric parameters of a double-layered microchannel heat sink (DL-MCHS). The overall thermal resistance R T is the objective function to be minimized, and the number of channels N, channel width ratio β, lower channel aspect ratio α l, and upper channel aspect ratio α u are the search variables. For a given bottom area (10 × 10 mm) and heat flux (100 W/cm 2), the optimal (minimum) thermal resistance of the double-layered microchannel heat sink is about R T = 0.12°C/m 2W. The corresponding optimal geometric parameters are N = 73, β = 0.50, α l = 3.52, and, α u = 7.21 under a total pumping power of 0.1 W. These parameters reduce the overall thermal resistance by 52.8% compared to that yielded by an initial guess (N = 112, β = 0.37, α l = 10.32, and α u = 10.93). Furthermore, the optimal thermal resistance decreases rapidly with the pumping power and then tends to approach an constant value. As the pumping power increases, the optimal values of N, α l, and α u increase, whereas the optimal β value decreases. However, increasing the pumping power further is not always cost-effective for practical heat sink designs. © 2012 Elsevier Ltd. All rights reserved.


Chen D.,North China Electrical Power University | Li W.,North China Electrical Power University | Zhang X.,Xi'an Jiaotong University | Kwong S.,City University of Hong Kong
International Journal of Approximate Reasoning | Year: 2014

Covering rough sets generalize traditional rough sets by considering coverings of the universe instead of partitions, and neighborhood-covering rough sets have been demonstrated to be a reasonable selection for attribute reduction with covering rough sets. In this paper, numerical algorithms of attribute reduction with neighborhood-covering rough sets are developed by using evidence theory. We firstly employ belief and plausibility functions to measure lower and upper approximations in neighborhood-covering rough sets, and then, the attribute reductions of covering information systems and decision systems are characterized by these respective functions. The concepts of the significance and the relative significance of coverings are also developed to design algorithms for finding reducts. Based on these discussions, connections between neighborhood-covering rough sets and evidence theory are set up to establish a basic framework of numerical characterizations of attribute reduction with these sets. © 2013 Elsevier Inc.


Wang L.,North China Electrical Power University | Li M.,North China Electrical Power University | Qi F.-H.,Beijing Wuzi University | Xu T.,China University of Petroleum - Beijing
Physics of Plasmas | Year: 2015

Under investigation in this paper is a variable-coefficient derivative nonlinear Schrödinger (vc-DNLS) equation modeling the nonlinear Alfvén waves in the inhomogeneous plasmas. The modulation instability is examined for this inhomogeneous nonlinear model. The nonautonomous breather and rogue wave solutions of the vc-DNLS equation are obtained via the modified Darboux transformation. It is found that the velocity and amplitude of the breather can be controlled by the inhomogeneous magnetic field and nonuniform density. Such novel phenomena as breather amplification and nonlinear Talbot effect-like property are demonstrated with the proper choices of the inhomogeneous parameters. Furthermore, dynamics of the fundamental rogue wave, periodical rogue wave, and composite rogue wave are graphically discussed. The trajectories and amplitudes of the rogue waves can be manipulated by the inhomogeneous magnetic field and nonuniform density. In addition, the nonlinear tunneling of the rogue waves and breathers is studied. As an application, a sample model is treated with our results, and the graphical illustrations exhibit the compressing, expanding, and fluctuating phenomena of the Alfvén rogue waves. © 2015 AIP Publishing LLC.


Wang X.-D.,North China Electrical Power University | Huang Y.-X.,National Chung Cheng University | Cheng C.-H.,National Cheng Kung University | Ta-Wei Lin D.,National University of Tainan | Kang C.-H.,National University of Tainan
Energy | Year: 2012

Thermoelectric devices (TEs) can achieve direct conversion of heat and electricity by semiconductor materials, coupling of heat transfer and electric conduction is important to accurately predict the performance of TEs. This paper develops a general, three-dimensional numerical model of TEs with consideration of coupling of temperature field and electric potential field. The model is used to figure out the performance of thermoelectric coolers (TECs) with the temperature-dependent thermal conductivity, electric conductivity, and Seebeck coefficient of semiconductor materials. A miniature TEC is considered and Bi 2(Te 0.94Se 0.06) 3 and (Bi 0.25Sb 0.75)Te 3 are selected as the n-type and p-type thermoelectric materials, respectively. The effect of parameters such as the temperature difference and the current is investigated under conditions of variable material properties as well as radiation and convection heat transfer occurred between the TEC and the ambient gas. The results show that the variable properties and the heat losses to the ambient gas have significant effects on the cooling capacity and the coefficient of performance (COP) of the TEC. Three-dimensional temperature distributions within the semiconductors is observed under convective boundary condition and it becomes remarkable at large temperature differences and high currents. © 2012 Elsevier Ltd.


Guo D.Z.,Xi'an Jiaotong University | Sun D.L.,North China Electrical Power University | Li Z.Y.,Xi'an Jiaotong University | Tao W.Q.,Xi'an Jiaotong University
Numerical Heat Transfer; Part A: Applications | Year: 2011

This article presents a numerical method directed towards the simulation of flows with changes of phase. The volume-of-fluid level set (VOSET) method, which is a new interface capturing method and combines the advantages of both volume-of-fluid (VOF) and level set methods, is used for interface tracking. A difficulty occurs for the problems studied here: the discontinuous velocity field due to the difference between mass-weighted velocity and volume weighted velocity caused by the phase change at the interface. In this article, some special treatment is made to overcome this difficulty. The VOSET method and the developed treatment for the difference between mass-weighted and volume-weighted velocities are adopted to simulate a one-dimensional Stefan problem, two-dimensional horizontal film boiling, and horizontal film boiling of water at near critical pressure. The predicted results in both Nusselt number and flow patterns are agreeable with experimental results available in the literature. Copyright © Taylor & Francis Group, LLC.


Hung T.-C.,Roc Military Academy | Yan W.-M.,National University of Tainan | Wang X.-D.,North China Electrical Power University | Chang C.-Y.,National University of Tainan
International Journal of Heat and Mass Transfer | Year: 2012

Heat transfer enhancement in a 3-D microchannel heat sink (MCHS) using nanofluids is investigated by a numerical study. The addition of nanoparticles to the coolant fluid changes its thermophysical properties in ways that are closely related to the type of nanoparticle, base fluid, particle volume fraction, particle size, and pumping power. The calculations in this work suggest that the best heat transfer enhancement can be obtained by using a system with an Al 2O 3-water nanofluid-cooled MCHS. Moreover, using base fluids with lower dynamic viscosity (such as water) and substrate materials with high thermal conductivity enhance the thermal performance of the MCHS. The results also show that as the particle volume fraction of the nanofluid increases, the thermal resistance first decreases and then increases. The lowest thermal resistance can be obtained by properly adjusting the volume fraction and pumping power under given geometric conditions. For a moderate range of particle sizes, the MCHS yields better performance when nanofluids with smaller nanoparticles are used. Furthermore, the overall thermal resistance of the MCHS is reduced significantly by increasing the pumping power. The heat transfer performance of Al 2O 3-water and diamond-water nanofluids was 21.6% better than that of pure water. The results reported here may facilitate improvements in the thermal performance of MCHSs. © 2012 Elsevier Ltd. All rights reserved.


Zhang Y.,North China Electrical Power University | Zhang Y.,University of South Carolina | Wang Z.,North China Electrical Power University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

In this paper, we introduce bifurcation theory into complex nonlinear systems. We adopt a novel approach to identify faults in electric circuit systems. After accidents occur without warning, with large numbers of complicated and high-precision calculations, we use bifurcation results of corresponding amplitude and frequency (period) to analyze their universal characteristics. Based on super attractive parameters, we have got the universal constant 4.6692.... The results from the present investigation imply that each fault in an electric circuit system must correspond to one or more bifurcation locations, which will provide a bifurcation criterion of faults in complex nonlinear systems. This research will have a significant theoretical value and engineering practical significance. © 2014 Elsevier B.V.


Fu X.,Wuhan University | Li A.,Changjiang River Scientific Research Institute | Wang L.,North China Electrical Power University | Ji C.,North China Electrical Power University
Computers and Mathematics with Applications | Year: 2011

This paper presents a new approach for short-term hydropower scheduling of reservoirs using an immune algorithm-based particle swarm optimization (IA-PSO). IA-PSO is employed by coupling the immune information processing mechanism with the particle swarm optimization algorithm in order to achieve a better global solution with less computational effort. With the IA-PSO technique, the hydro-electrical optimization model of reservoirs is formulated as a high-dimensional, dynamic, nonlinear and stochastic global optimization problem of a multi-reservoir hydropower system. The purpose of the proposed methodology is to maximize total hydropower production. Here it is applied to a reservoir system on the Qingjiang River, in the Yangtze watershed, that consists of two reservoirs. The results are compared with the results obtained through conventional operation method, the dynamic programming and the standard PSO algorithm. From the comparative results, it is found that the IA-PSO approach provides the most globally optimum solution at a faster convergence speed. © 2011 Elsevier Ltd. All rights reserved.


Zhang K.,North China Electrical Power University | Cao Y.,North China Electrical Power University | Cao Y.,Western Kentucky University | Pan W.-P.,North China Electrical Power University | Pan W.-P.,Western Kentucky University
Bioresource Technology | Year: 2013

Despite much research on co-combustion of tobacco stem and high-sulfur coal, their blending optimization has not been effectively found. This study investigated the combustion profiles of tobacco stem, high-sulfur bituminous coal and their blends by thermogravimetric analysis. Ignition and burnout performances, heat release performances, and gaseous pollutant emissions were also studied by thermogravimetric and mass spectrometry analyses. The results indicated that combustion of tobacco stem was more complicated than that of high-sulfur bituminous coal, mainly shown as fixed carbon in it was divided into two portions with one early burning and the other delay burning. Ignition and burnout performances, heat release performances, and gaseous pollutant emissions of the blends present variable trends with the increase of tobacco stem content. Taking into account the above three factors, a blending ratio of 0-20% tobacco stem content is conservatively proposed as optimum amount for blending. © 2012 Elsevier Ltd.


Wang L.,North China Electrical Power University | Li M.,North China Electrical Power University | Qi F.-H.,Beijing Wuzi University | Geng C.,North China Electrical Power University
European Physical Journal D | Year: 2015

Under investigation in this paper is a variable-coefficient derivative nonlinear Schrödinger (vc-DNLS) equation governing the femtosecond pulses in the inhomogeneous optical fibers or nonlinear Alfvén waves in the inhomogeneous plasmas. Higher-order breather and rogue wave solutions of the vc-DNLS equation are obtained via the variable-coefficient modified Darboux transformation. Two types of the breather interactions (the head-on and overtaking collisions) are exhibited with different spectral parameters. By suitably choosing the inhomogeneous functions, the parabolic breather, periodic breather, breather amplification and breather evolution are demonstrated. Furthermore, the characteristics of the higher-order fundamental rogue wave, periodic rogue wave and composite rogue wave are graphically discussed. Additionally, the nonlinear tunneling of the higher-order breathers and rogue waves are studied. © 2015 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.


Wang L.,North China Electrical Power University | Li X.,North China Electrical Power University | Qi F.-H.,Beijing Wuzi University | Zhang L.-L.,North China Electrical Power University
Annals of Physics | Year: 2015

Under investigation in this paper are the inhomogeneous nonlinear Schrödinger Maxwell-Bloch (INLS-MB) equations which model the propagation of optical waves in an inhomogeneous nonlinear light guide doped with two-level resonant atoms. Higher-order nonautonomous breather as well as rogue wave solutions in terms of the determinants for the INLS-MB equations are presented via the n-fold variable-coefficient modified Darboux transformation. The interactions among two nonautonomous breathers are graphically discussed, including the fundamental breather, bound breather, two-breather compression and two-breather evolution, etc. Moreover, several patterns of the higher-order rogue waves are also exhibited, such as the square rogue wave, two- and three-order periodic rogue waves, periodic fission and fusion, two-order stationary rogue waves, and recurrence of the two-order rogue waves. The character of the trajectory of the two-order periodic rogue wave is analyzed. Additionally, a novel type of interaction, namely, the collision between the breather and long-lived rogue waves, is found to be elastic. Our results could be useful for controlling the nonautonomous optical breathers and rogue waves in the inhomogeneous erbium doped fiber. © 2015 Elsevier Inc.


Wu M.,Xi'an Jiaotong University | Li M.,Xi'an Jiaotong University | Xu C.,North China Electrical Power University | He Y.,Xi'an Jiaotong University | Tao W.,Xi'an Jiaotong University
Applied Energy | Year: 2014

The impact of concrete structure on the thermal performance of the dual-media thermocline thermal energy storage (TES) tank which is very promising to be applied in concentrating solar power (CSP) systems is investigated. The lumped capacitance method is used since the introduction of corrected heat transfer coefficients between solid and fluid extends the validity of this method to large Biot numbers. The discharging performance of four typical concrete structures including the channel-embedded structure, the parallel-plate structure, the rod-buddle structure and the packed-bed structure is studied. The thermocline behaviors during the discharging process for the four structures with the influences of feature size and fluid inlet velocity are analyzed, and the corresponding effective discharging efficiency and discharging time are reported. The results show that the concrete TES tanks with four different structures show different thermocline behaviors during the discharging process. The packed-bed structure gives the best discharging performance, followed by the rod-bundle structure, the parallel-plate structure and the channel-embedded structure sequentially. The discharging performance is also found to be influenced to some extent by the feature size and the fluid inlet velocity for all four different structures. © 2013 Elsevier Ltd.


Wu M.,Xi'an Jiaotong University | Xu C.,North China Electrical Power University | He Y.-L.,Xi'an Jiaotong University
Applied Energy | Year: 2014

We investigate the dynamic thermal performance of a molten-salt packed-bed thermal energy storage (TES) system using capsules filled with high-temperature phase change material (PCM), which is identified as a promising low-cost TES system for concentrating solar power (CSP) plants. A transient two-dimensional dispersion-concentric (D-C) model is modified to account for the phase change process within capsules so as to determine the temperature distribution and phase change front within each capsule. Using the model, detailed characteristics of heat transfer between molten salt and the packed PCM capsules are investigated, and a parametric sensitivity analysis is provided. During the discharging process, different variation trends are found for the capsule temperature due to the existence of the isothermal solidification process. As a result, generally there exists a quasi-isothermal region and two thermocline regions for the molten-salt temperature along the tank height, and the molten-salt temperature at the outlet also shows a quasi-isothermal period, during which the molten-salt outlet temperature is very close to the phase change temperature (PCT) of PCM. It is also found that the effective discharging efficiency of the system can be increased by increasing the PCT, decreasing the molten-salt inlet velocity or decreasing the capsule diameter. These results provide suggestions to optimize the design and operational parameters for the system within practical constrains. © 2014 Elsevier Ltd.


Wang X.-H.,Data Management | Cong R.-G.,North China Electrical Power University
Procedia Engineering | Year: 2012

Supply chain management played a critical role in the electric power industrial chain optimization. The purpose of this paper was to review a sample of the literatures relating to supply chain management and its possible applications in electricity power system, especially in the context of climate change. The study compared the difference between electric power supply chain management and traditional supply chain management. Furthermore, some possible research topics are addressed. The aim of this paper was to promote the application of supply chain management in the China electricity sector optimizations and brought a change in the related government policy options. © 2011 Published by Elsevier Ltd.


Wang Y.,North China Electrical Power University | Xu L.,Queen's University of Belfast
IEEE Transactions on Power Delivery | Year: 2010

This paper investigates the control and operation of doubly-fed induction generator (DFIG) and fixed-speed induction generator (FSIG) based wind farms under unbalanced grid conditions. A DFIG system model suitable for analyzing unbalanced operation is developed, and used to assess the impact of an unbalanced supply on DFIG and FSIG operation. Unbalanced voltage at DFIG and FSIG terminals can cause unequal heating on the stator windings, extra mechanical stresses and output power fluctuations. These problems are particularly serious for the FSIG- based wind farm without a power electronic interface to the grid. To improve the stability of a wind energy system containing both DFIG and FSIG based wind farms during network unbalance, a control strategy of unbalanced voltage compensation by the DFIG systems is proposed. The DFIG system compensation ability and the impact of transmission network impedance are illustrated. The simulation results implemented in Matlab/Simulink show that the proposed DFIG control system improves not only its own performance, but also the stability of the FSIG system with the same grid connection point during network unbalance. © 2009 IEEE.


Chen D.,North China Electrical Power University | Zhang L.,Hong Kong Polytechnic University | Zhao S.,Renmin University of China | Hu Q.,Hong Kong Polytechnic University | Zhu P.,Hong Kong Polytechnic University
IEEE Transactions on Fuzzy Systems | Year: 2012

Attribute reduction is one of the most meaningful research topics in the existing fuzzy rough sets, and the approach of discernibility matrix is the mathematical foundation of computing reducts. When computing reducts with discernibility matrix, we find that only the minimal elements in a discernibility matrix are sufficient and necessary. This fact motivates our idea in this paper to develop a novel algorithm to find reducts that are based on the minimal elements in the discernibility matrix. Relative discernibility relations of conditional attributes are defined and minimal elements in the fuzzy discernibility matrix are characterized by the relative discernibility relations. Then, the algorithms to compute minimal elements and reducts are developed in the framework of fuzzy rough sets. Experimental comparison shows that the proposed algorithms are effective. © 2012 IEEE.


Zhao Z.-Y.,North China Electrical Power University | Zhang S.-Y.,North China Electrical Power University | Zuo J.,University of South Australia
Renewable and Sustainable Energy Reviews | Year: 2011

The solar photovoltaic (PV) is an emerging renewable energy technology. With massive resource potential and commercial prospects, the development of the Chinese PV power industry is exceeding expectations. Chinas total PV power installations will account for 5% of the total electric power capacity by 2050. A diamond model approach is adopted in this study to identify and analyze factors that have significant impacts on the development of Chinas PV power industry. These factors include: factor conditions, demand conditions, chance, firm strategy, structure and rivalry, related and support industry, and government. Each factor identified in the model affects the competitiveness of the whole PV industry from a different angle. Therefore all factors ought to be strengthened for the long-term development of PV industry. A gear model is developed as a result of diamond model analysis. This model provides a useful tool to show the dynamic interactions among all factors affecting the development of the Chinese solar PV industry. All rights reserved.


Zhao Z.-Y.,North China Electrical Power University | Zuo J.,University of South Australia | Fan L.-L.,North China Electrical Power University | Zillante G.,University of South Australia
Renewable Energy | Year: 2011

China is facing a number of energy-related challenges such as shortage of electricity supply and environmental pollution. The Government recognized the important role the renewable energy plays in the power generation structure. As a result, a series of supporting policies, laws and regulations have been issued to boost the renewable energies in China. This paper provides a critical analysis of the policy framework for the renewable energy in China and its impacts on the power generation structure. The relevant policy documents, including the most recent government work report delivered by Premier Wen Jia-bao during the Third Session of the 11th National People's Congress (NPC) in March 2010 are analyzed. The patterns of renewable energy developments are found strongly correlated with the promulgation of relevant policies. © 2010.


Zhao Z.Y.,North China Electrical Power University | Zuo J.,University of South Australia | Feng T.T.,North China Electrical Power University | Zillante G.,University of South Australia
Renewable Energy | Year: 2011

The past decades have witnessed the rapid growth of foreign participation in the renewable energy development in China. This is a result of massive energy demand and the Government's strategy to shadow the role of traditional fossil fuel in the energy mix. This paper critically reviewed the international cooperation in the field of renewable energy with various partners in the new century. The cooperation pattern varies from partner to partner. The results showed that China has benefited from the international cooperation on renewable energy such as accessing to finance and advanced technologies, developing human resources related to renewable energy, and enhancing related policy framework. Major issues associated with the international cooperation are discussed as well. © 2010.


Cong R.-G.,North China Electrical Power University | Cong R.-G.,Lund University | Wei Y.-M.,Beijing Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2012

Carbon allowances auctions are a good way to achieve the carbon allowance allocations under international agreements to address global climate change. Based on an economic experiment, this paper compares three possible carbon allowance auction formats (uniform price auction, discriminatory price auction and English clock auction) with heterogeneous bidders (coal power plants and gas power plants) from four perspectives (carbon price, auction efficiency, demand withholding and fluctuations in power supplies). Possibilities of collusion among bidders and impacts of allowance banking and penalty price on bidders' behaviors under different auction formats are also examined. The results show that (1) when there are relatively more bidders and there are no obvious communications between them, despite there being some tacit collusion, efficiency of English clock auction is greater than the other two formats; (2) when there are relatively fewer bidders and there are obvious communications between them, explicit collusions are observed under English clock auction. In this case, discriminatory price auction helps prevent collusion to some extents; (3) in the banking scenario, more speculations are observed, while penalty price exacerbates price volatility. © 2012 Elsevier Ltd. All right reserved.


Liu X.,North China Electrical Power University | Guan P.,Beijing Institute of Machinery | Chan C.W.,University of Hong Kong
IEEE Transactions on Control Systems Technology | Year: 2010

A coordinated control strategy is often used to ensure a thermal power plant to have a higher rate of load change, but without violating the thermal constraints. Although model predictive control has been widely used for controlling power plant, handling input constraints is a major problem especially as these plants are nonlinear. Two alternative methods of exploiting the nonlinear predictive control are presented in this paper. One is the input-output feedback linearization technique based on a suitably chosen approximated linear model. The other is based on neuro-fuzzy networks to represent a nonlinear dynamic process using a set of local models. From the criteria based on the integral absolute errors and the relative optimization time for completing the simulation, it is shown that the performance of the coordinated control of a steam-boiler generation plant using these two nonlinear predictive methods are better than the conventional predictive method. © 2010 IEEE.


Zhao Z.-Y.,North China Electrical Power University | Ling W.-J.,North China Electrical Power University | Zillante G.,University of South Australia | Zuo J.,University of South Australia
Renewable Energy | Year: 2012

Compared to the conventional fossil fuel energy, wind power provides clean energy which can mitigate the impacts of greenhouse gas emission and optimize the electric power source structure. During the last decade, the strong support of the Chinese government has contributed to the rapid development of the Chinese wind power sector which has in turn resulted in a significant growth of the Chinese wind turbine manufacturing industry. This growth went through several phases including the initial approval of several leading global Wind Turbine Manufacturers (WTMs) to enter the Chinese market through various methods which included the establishment of wholly foreign-owned enterprises from 2005. Similarly, several government policies have contributed to the significant expansion in terms of both productivity and quantities by local Chinese WTMs. The entrance of foreign WTMs into the Chinese market coupled with the rapid growth of local WTMs has contributed to intense competition in China's wind turbine manufacture market. This paper analyzes the characteristics of the wind turbine manufacturing industry in China and establishes a hierarchical structure of the WTMs' competitive priority system. This system consists of 5 indicators and 10 sub-indicators. By comparing the different performances of each indicator, the competitive advantages and disadvantages of the foreign and local WTMs in the Chinese market are identified. The findings provide a valuable reference for the WTMs to improve their competitive priorities and to formulate their competitive strategy in the Chinese wind turbine market. This paper provides inputs for the sustainable development of wind power industry in other countries. © 2011.


Zhao Z.-Y.,North China Electrical Power University | Ling W.-J.,North China Electrical Power University | Zillante G.,University of South Australia
Renewable and Sustainable Energy Reviews | Year: 2012

With support from the Chinese government, the Chinese wind power generation industry is experiencing rapid development. The quick growth of the wind power generation industry has promoted the development of the Chinese wind turbine manufacturing industry. Similarly, the quantity and the productivity of the local Chinese Wind Turbine Manufacturers (WTMs) have also undergone a quick and significant expansion. This is resulting in an increase in competition amongst the WTMs in China. Being relatively new, this creates a fertile environment for local Chinese WTMs that is ripe for study and analysis. Based on the niche theory of industrial ecosystem and enterprise, this paper investigates the Chinese wind turbine manufacturing industry, and proposes a wind turbine manufacturing industry ecosystem model and a WTMs' ecological niche evaluation index system (WENEIS). Use is made of a catastrophe theory model evaluation method to evaluate the ecological niche status of the 6 main local Chinese WTMs selected and a spider diagram is established to compare the status of the different enterprises' ecological niche. The proposed WENEIS aids WTMs in finding the competitive advantage and disadvantage factors for their development, as well as providing a valuable reference for the WTMs to improve their business environment and to formulate their competitive strategy in the future.


Feng X.,North China Electrical Power University | Xia Y.,North China Electrical Power University | Xia Y.,CAS Lanzhou Institute of Chemical Physics
Applied Surface Science | Year: 2012

In this paper, titanium doped diamond-like carbon (Ti-DLC) coatings were prepared onto AISI 52100 steel substrates using medium frequency magnetic sputtering process, and were analyzed using the Raman and transmission electron microscope (TEM). Two kinds of 1,3-dialkyl imidazolium ionic liquids (ILs) were synthesized and evaluated as lubricants for Ti-DLC/steel contacts at room temperature, and PFPE as comparison lubricant. The tribological properties of the ILs were investigated using a ball-on-disk type UMT reciprocating friction tester. The results indicated that the ILs have excellent friction-reducing properties, the friction coefficient kept at a relatively stable value of 0.07-0.06, which was reduced approximately by 47% compared with perfluoropolyether (PFPE). The worn surfaces of Ti-DLC coatings were observed and analyzed using a MICROXAM-3D non-contact surface profiler, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The Ti-DLC coatings using ionic liquids lubricating systems are considered as potential lubricating system in vacuum and space moving friction pairs. © 2011 Elsevier B.V. All rights reserved.


Xu B.,North China Electrical Power University | Sun L.,North China Electrical Power University | Xu L.,Queen's University of Belfast | Xu G.,Queen's University of Belfast
IEEE Transactions on Energy Conversion | Year: 2013

The traditional Hilbert method to detect broken rotor bar fault in induction motors is reviewed and its major drawbacks are clearly revealed, namely, deteriorating or even completely failing when a motor operating at low slip due to the fixed constraints of fast Fourier transform (FFT) is used in this method. To overcome this, the estimation of signal parameters via rotational invariance technique (ESPRIT) is then introduced to replace FFT, and an improved Hilbert method is thus presented by conjugating the Hilbert transform and ESPRIT together. Experimental results of a small motor in a laboratory and a large motor operating on an industrial site are reported to demonstrate the effectiveness of the improved Hilbert method. © 1986-2012 IEEE.


Zhao Z.-Y.,North China Electrical Power University | Zhao X.-J.,North China Electrical Power University | Davidson K.,University of South Australia | Zuo J.,University of South Australia
Journal of Cleaner Production | Year: 2012

In the construction industry, corporate social responsibility (CSR) is increasingly valued as one factor that will contribute to business sustainable development. Construction enterprises typically develop CSR reports as one way to maintain a positive corporate image. There is a growing body of research which considers the effectiveness of CSR. However, understanding what CSR means to the construction industry, and how to practice it, is limited. This paper develops a framework for CSR indicators relevant to construction enterprises worldwide as a tool for CSR performance. CSR stakeholders are identified through literature review, and these stakeholders are mapped on construction process and corporation to represent stakeholders involved in construction enterprises. Based on stakeholder theory, CSR performance issues related to each stakeholder are developed to show key factors of CSR performance of construction companies, and the indicators are subsequently extracted to reveal specific contents included in these performance issues. The indicator system provides guidance for CSR implementation in the construction industry and enables construction enterprises to assess CSR performance scientifically, which in turn will assist the attainment of business sustainable development. Future research opportunities exist to define a transparent weight system, to investigate the role of contextual factors, and to examine interactions of stakeholders and interactions of indicators in this model. © 2012 Elsevier Ltd. All rights reserved.


Cao J.,Queen's University of Belfast | Cao J.,North China Electrical Power University | Du W.,North China Electrical Power University | Wang H.F.,North China Electrical Power University | Bu S.Q.,Queen's University of Belfast
IEEE Transactions on Power Systems | Year: 2013

The paper considers the optimal power flow (OPF) of a meshed AC/DC power transmission network with voltage source converter based multi-terminal DC (VSC-MTDC) networks. The OPF problem is formulated to minimize the transmission loss of the whole AC/DC network with two different VSC control strategies considered, constant DC voltage control (master-slave control) and DC voltage droop control. In addition, Grid Code compliance of wind farms is also embedded in the OPF formulation. The presented OPF is evaluated and demonstrated in the paper by two example meshed AC/DC power systems. © 1969-2012 IEEE.


Zuo J.,University of South Australia | Zhao Z.-Y.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2014

Green building is one of measures been put forward to mitigate significant impacts of the building stock on the environment, society and economy. However, there is lack of a systematic review of this large number of studies that is critical for the future endeavor. The last decades have witnessed rapid growing number of studies on green building. This paper reports a critical review of the existing body of knowledge of researches related to green building. The common research themes and methodology were identified. These common themes are the definition and scope of green building; quantification of benefits of green buildings compared to conventional buildings; and various approaches to achieve green buildings. It is found that the existing studies played predominately focus on the environmental aspect of green building. Other dimensions of sustainability of green building, especially the social sustainability is largely overlooked. Future research opportunities were identified such as effects of climatic conditions on the effectiveness of green building assessment tools, validation of real performance of green buildings, unique demands of specific population, and future proofing. © 2013 Published by Elsevier Ltd.


Cong R.-G.,North China Electrical Power University | Cong R.-G.,Beijing Institute of Technology | Cong R.-G.,CAS Institute of Policy and Management | Wei Y.-M.,Beijing Institute of Technology
Energy | Year: 2010

In Copenhagen climate conference China government promised that China would cut down carbon intensity 40-45% from 2005 by 2020. CET (carbon emissions trading) is an effective tool to reduce emissions. But because CET is not fully implemented in China up to now, how to design it and its potential impact are unknown to us. This paper studies the potential impact of introduction of CET on China's power sector and discusses the impact of different allocation options of allowances. Agent-based modeling is one appealing new methodology that has the potential to overcome some shortcomings of traditional methods. We establish an agent-based model, CETICEM (CET Introduced China Electricity Market), of introduction of CET to China. In CETICEM, six types of agents and two markets are modeled. We find that: (1) CET internalizes environment cost; increases the average electricity price by 12%; and transfers carbon price volatility to the electricity market, increasing electricity price volatility by 4%. (2) CET influences the relative cost of different power generation technologies through the carbon price, significantly increasing the proportion of environmentally friendly technologies; expensive solar power generation in particular develops significantly, with final proportion increasing by 14%. (3) Emission-based allocation brings about both higher electricity and carbon prices than by output-based allocation which encourages producers to be environmentally friendly. Therefore, output-based allocation would be more conducive to reducing emissions in the Chinese power sector. © 2010.


Ma L.,Renmin University of China | Zhang J.,North China Electrical Power University | Chen G.F.,Renmin University of China | Yu W.,Renmin University of China
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

In this Rapid Communication, we reported the results of NMR study on LiFeAs single crystals. We find a strong evidence of the low-temperature spin fluctuations; by changing sample preparation conditions, the system can be tuned toward a spin-density-wave (SDW) quantum-critical point. The detection of an interstitial Li(2) ion, possibly locating in the tetrahedral hole, suggests that the off-stoichiometry and/or lattice defect can probably account for the absence of the SDW ordering in LiFeAs. These facts show that LiFeAs is a strongly correlated system and the superconductivity is likely originated from the SDW fluctuations. © 2010 The American Physical Society.


Liu G.,Hunan University | Shi H.,Hunan University | Yang Y.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

As power system is a non-analytical complex variable system, node voltages are not analytical complex-variable function of load current. In the plural domain, node voltages are not directly derivative of the load current, so there are still no papers using dynamic analytic method to study power system voltage stability. In this paper, the dynamic analytic method of non-analytical complex was derived; the comprehensive dynamic equivalent impedance of power system was defined; and the necessary condition when power system achieves limit transmission is that the comprehensive dynamic equivalence impedance mode is equal to load static equivalent impedance mode. By simulation and calculations, it proved that the necessary condition was right; load impedance modulus margin can accurately describe the system load node voltage stability level. Dynamic analytic method set a theoretical foundation to establish power system nonlinear equivalent model, and to apply nonlinear equivalent model to calculate limit power quickly and accurately. The maximum transmission power judgment criterion can be used to judge whether it is feasible to the solution of power flow equation for large-scale power system. © 2013 Chin. Soc. for Elec. Eng.


Liu G.,Hunan University | Yang Y.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Voltage stability and angle stability are only two extreme conditions of power system stability analysis. When Jacobian matrix is singular, it's not only critical point of voltage stability, but static critical point of angle stability. According to the general principle of extreme value analysis of nonlinear equations, the equivalence relation of static angle stability and voltage stability was proved. The decentralized dynamic equivalent method was proposed, by introducing current auxiliary variable and flow equations. The unified analysis method of dynamic voltage stability and angle stability was established by using the dynamic parameters in Jacobian matrix and the nonlinear dynamic analysis principle. Through the application of direction differential of complex current (voltage), the relationship between integrated dynamic equivalent impedance and load static equivalent impedance were studied and the comprehensive evaluation of voltage stability and static angle stability margin index were proposed. Impedance margin means the unitization of limit load power and the transformation of angle curve into power-impedance curve. The impedance margin is not only a sensitivity index, but has good nonlinear properties. Take the dynamic characteristics of injection power into account further; we will promote the online application value of resistance margin in the static stability, transient stability and dynamic stability analysis. © 2013 Chin. Soc. for Elec. Eng.


Zhou G.,North China Electrical Power University | Zhang Y.,Tianjin University
Applied Thermal Engineering | Year: 2012

Inlet pressure fluctuations were found during the experiments for coiled adiabatic capillary tubes in a one-pass-through type test facility. The fluctuation takes place when the inlet temperature rapidly changes from one point to another. Measured temperature distribution along the tube length showed that this phenomenon may be caused by the variation of flash point location in the capillary tube which leads to the pressure variation wave propagating upstream. Further experiments showed that the pressure fluctuation for coiled capillary tubes is much more prominent than for straight ones; the inlet pressure fluctuation is weak for small coil-diameter capillary tubes; with the increasing of the preset inlet pressure and decreasing of target inlet temperature, the fluctuation amplitude decreases; the pressure fluctuation amplitude at the inlet of parallel coiled capillary tubes is much lower than that of the single one and it needs less time to be stabilized which indicates the advantages of using parallel capillary tubes. The inlet pressure fluctuation in an actual air-conditioner system is found weaker than in the one-pass-through test facility. © 2011 Elsevier Ltd. All rights reserved.


Zhou G.,North China Electrical Power University | Zhang Y.,Tianjin University
Applied Energy | Year: 2010

This paper experimentally investigated the system performance of a split-type air conditioner matching with different coiled adiabatic capillary tubes for HCFC22 and HC290. Experiments were carried out in a room-type calorimeter. The results have shown that (1) similar cooling effects can be achieved by matching various capillary tubes of different inner diameters; (2) parallel capillary tubes presented better system performance and flow stability with weaker inlet pressure fluctuations than the single capillary tube; (3) with the coil diameter of the capillary tube increasing from 40 mm to 120 mm, the mass flow rate tended to increase slightly. But the cooling capacity, input power and energy efficiency ratio (EER) did not show evident tendency of change; (4) the refrigerant charge and mass flow rate for HC290 were only 44% and 47% of that for HCFC22, respectively, due to the much lower density. And HC290 had 4.7-6.7% lower cooling capacity and 12.1-12.3% lower input power with respect to HCFC22. However, the EER of HC290 can be 8.5% higher than that of HCFC22, which exhibits the advantage of using HC290. In addition, the experimental uncertainties were analyzed and some application concerns of HC290 were discussed. © 2009 Elsevier Ltd. All rights reserved.


Huang X.,North China Electrical Power University | Taytor G.,Brunel University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

When solving the service restoring (SR) problem using the intelligent optimization algorithm, considerable time has to be consumed and the optimizing performance of the algorithm is reduced as it is necessary to not only repeatedly do network topology analysis during changes of the network structure but also very often to do additional checking on radiation during optimization to ensure that the constraints on network radiation operation are not violated. To avoid these disadvantages, the node-depth encoding (NDE) technique is introduced into the non-dominating sorting genetic algorithm-II (NSGA-II) to solve the SR problem to replace traditional crossover and mutation operations with preserve ancestor opexator (PAO) and change ancestor operaton (CAO) operations in NDE technique. The topological structure of the system can be quickly obtained with the NDE technique. Simulation results show that the algorithm proposed has a better performance in convergence and diversity than NSGA-II. © 2011 State Grid Electric Power Research Institute Press.


Xu E.,CAS Institute of Electrical Engineering | Yu Q.,CAS Institute of Electrical Engineering | Wang Z.,CAS Institute of Electrical Engineering | Yang C.,North China Electrical Power University
Renewable Energy | Year: 2011

1 MW Dahan solar thermal power tower plant is modeled from mathematical models for all of the working conditions using the modular modeling method. The dynamic and static characteristics of the power plant are analyzed based on these models. Response curves of the system state parameters are given for different solar irradiance disturbances. Conclusions in this paper are good references for the design of solar thermal power tower plant. © 2010 Elsevier Ltd.


Chunxi L.,North China Electrical Power University | Ling W.S.,North China Electrical Power University | Yakui J.,Hebei Electric Power Research Institute
Energy Conversion and Management | Year: 2011

The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap. © 2011 Elsevier Ltd. All rights reserved.


Zhang J.,North China Electrical Power University | Zhao C.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

The high voltage direct current transmission based on modular multilevel converter (MMC-HVDC) usually adopts double closed-loop vector control, which has the problems such as too many parameters needed to be adjusted and dynamic response being unsatisfied under voltage unbalanced condition in order to control the positive and negative current in positive and negative rotating reference frame. This paper analyzes the MMC-HVDC's mathematic characteristics under αβ reference frame, what is more, the power calculation is also conducted. In order to reduce the sin ac signal zero error and control the positive and negative current uniformly, the proportional-resonant(PR)controller is introduced in αβ reference frame which does not need the complex reference transformation, so the disadvantageous effect of coupled or feedback voltage which is easily influenced by circuit parameters is eliminated, the control algorithm becomes easy to be realized; In addition, the traditional voltage balancing strategy is also improved through the PR. The simulation platform of MMC-HVDC is built in the electromagnetic transient simulation software PSCAD/EMTDC, and the simulation of αβ-PR is carried out to verify this controllers' effectiveness and feasibility. © 2013 Chinese Society for Electrical Engineering.


Wang L.,North China Electrical Power University | Wang L.,TU Berlin | Yang Y.,North China Electrical Power University | Dong C.,North China Electrical Power University | And 2 more authors.
Applied Energy | Year: 2014

The design trade-offs between thermodynamics and economics for thermal systems can be studied with the aid of multi-objective optimization techniques. The investment costs usually increase with increasing thermodynamic performance of a system. In this paper, an enhanced differential evolution with diversity-preserving and density-adjusting mechanisms, and a newly-proposed algorithm for searching the decision space frontier in a single run were used, to conduct the multi-objective optimization of large-scale, supercritical coal-fired plants. The uncertainties associated with cost functions were discussed by analyzing the sensitivity of the decision space frontier to some significant parameters involved in cost functions. Comparisons made with the aid of an exergoeconomic analysis between the cost minimum designs and a real industrial design demonstrated how the plant improvement was achieved. It is concluded that the cost of electricity could be reduced by a 2-4%, whereas the efficiency could be increased by up to two percentage points. The largest uncertainty is introduced by the temperature-related and reheat-related cost coefficients of the steam generator. More reliable data on the price prediction of future advanced materials should be used to obtain more accurate fronts of the objective space. © 2013 Elsevier Ltd.


Wang F.,North China Electrical Power University | Tan Z.,North China Electrical Power University | Li Y.,CAS Beijing National Laboratory for Molecular | Li Y.,Soochow University of China
Energy and Environmental Science | Year: 2015

The interfaces between the electrodes and the photoactive layer significantly influence the efficiency and stability of polymer solar cells (PSCs). By choosing suitable interfacial materials, the energetic barrier height at the interface could be reduced to form an ohmic contact with less series resistance, inducing high charge collection efficiency of the corresponding electrodes for holes or electrons. Solution-processable metal compounds, especially metal oxides and transition metal chelates, have the advantages of high charge carrier mobility, suitable work function, low cost, and high environmental stability, which make them attractive for applications as cathode and anode interfacial materials for efficient and stable PSCs. In this paper, we reviewed the recent progress on solution processable metal oxides and metal chelates as buffer layers in conventional and inverted PSCs. In the introduction section, we introduced the operating principles of conventional and inverted PSCs, followed by introducing the energy levels, optical properties, processing methods and characterization techniques of the buffer layers. In the second and third parts, we reviewed recent progress in materials for both anode and cathode buffer layers. Finally, we drew a conclusion and gave a perspective. We believe that solution-processable metal oxides and metal chelates will play a key role as buffer layers in the future fabrication of large area and flexible PSCs with high performance and long term stability. © 2015 The Royal Society of Chemistry.


Wang J.,North China Electrical Power University | Li L.,Beijing Information Science and Technology University | Niu D.,North China Electrical Power University | Tan Z.,North China Electrical Power University
Applied Energy | Year: 2012

Annual load forecasting is very important for the electric power industry. As influenced by various factors, an annual load curve shows a non-linear characteristic, which demonstrates that the annual load forecasting is a non-linear problem. Support vector regression (SVR) is proven to be useful in dealing with non-linear forecasting problems in recent years. The key point in using SVR for forecasting is how to determine the appropriate parameters. This paper proposes a hybrid load forecasting model combining differential evolution (DE) algorithm and support vector regression to deal with this problem, where the DE algorithm is used to choose the appropriate parameters for the SVR load forecasting model. The effectiveness of this model has been proved by the final simulation which shows that the proposed model outperforms the SVR model with default parameters, back propagation artificial neural network (BPNN) and regression forecasting models in the annual load forecasting. © 2012 Elsevier Ltd.


Tan Z.,North China Electrical Power University | Li L.,Beijing Information Science and Technology University | Wang J.,North China Electrical Power University | Wang J.,Argonne National Laboratory
Applied Energy | Year: 2011

This paper examines the driving forces for reducing China's CO2 emission intensity between 1998 and 2008, utilizing the logarithmic mean divisia index (LMDI) technique. By first grouping the CO2 emissions into two categories, those arising from activities related to the electric power industry and those from other sources, emission intensity is further broken down into the effects of the CO2 emission coefficient, energy intensity of power generation, power generation and consumption ratio, electricity intensity of the gross domestic product (GDP), provincial structural change, and the energy intensity of the GDP for other activities. The decomposition results show that improvements in the energy intensity of power generation, electricity intensity of GDP, and energy intensity of GDP for other activities were mainly responsible for the success in reducing China's CO2 emission intensity and that activities related to the electric power industry played a key role. It is also revealed that performance varied significantly at the individual province level. The provinces with higher emission levels contributed the most to China's improvements in CO2 emission intensity. © 2011 Elsevier Ltd.


Tan X.,North China Electrical Power University | Tan X.,CAS Hefei Institutes of Physical Science | Ren X.,CAS Hefei Institutes of Physical Science | Chen C.,North China Electrical Power University | And 2 more authors.
TrAC - Trends in Analytical Chemistry | Year: 2014

We review the analysis of lanthanide speciation at solid-water interfaces. We summarize the various mechanisms of lanthanide interaction with sorbent surfaces, such as surface complexation, precipitation and surface-induced redox reactions. There are a wide variety of available analytical techniques for understanding the speciation of lanthanides on surfaces and the reaction mechanisms of sorption. We also review recent advances in the utilization of quantum chemistry that widen the scope of lanthanide speciation studies. We review, summarize and discuss in detail the speciation of lanthanides, mainly Eu(III), at natural or synthetic mineral surfaces, and the available analytical techniques. We aim to collate valuable information about recent results for surface speciation analysis of lanthanides at solid-water interfaces. © 2014 Elsevier B.V.


Tan Z.,CAS Beijing National Laboratory for Molecular | Tan Z.,North China Electrical Power University | Zhang W.,CAS Beijing National Laboratory for Molecular | Zhang W.,North China Electrical Power University | And 6 more authors.
Advanced Materials | Year: 2012

High-performance inverted polymer solar cells (PSCs) with solution-processed titanium chelate TIPD as electron collecting layer are reported. The power conversion efficiency (PCE) of the inverted PSC with a-TIPD buffer layer with thermal annealing at 150°C for 10 min reached 7.4% under the illumination of AM1.5, 100 mW/cm2, which is increased by 16% in comparison with that (6.4%) of the device in the conventional structure. The PCE of 7.4% is the highest among the inverted PSCs reported so far in the literature. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Tan Z.,North China Electrical Power University | Li L.,North China Electrical Power University | Wang F.,North China Electrical Power University | Xu Q.,North China Electrical Power University | And 6 more authors.
Advanced Energy Materials | Year: 2014

High efficiency polymer solar cells using solution processed s-ReO x as the anode buffer layer are demonstrated. The s-ReOx layer can effectively change the light distribution within the photoactive layer and enhance its absorption. The solution-processable s-ReOx is a promising anode buffer layer material for high performance PSCs © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Liu Y.,North China Electrical Power University | Shi J.,North China Electrical Power University | Yang Y.,North China Electrical Power University | Lee W.-J.,University of Texas at Arlington
IEEE Transactions on Industry Applications | Year: 2012

The prediction algorithm is one of the most important factors in the quality of wind-power prediction. In this paper, based on the principles of wavelet transform and support vector machines (SVMs), as well as the characteristics of wind-turbine generation systems, two prediction methods are presented and discussed. In method 1, the time series of model input are decomposed into different frequency modes, and the models are set up separately based on the SVM theory. The results are combined together to forecast the final wind-power output. For comparison purposes, the wavelet kernel function is applied in place of the radial basis function (RBF) kernel function during SVM training in method 2. The operation data of one wind farm from Texas are used. Mean relative error and relative mean square error are used to evaluate the forecasting errors of the two proposed methods and the RBF SVM model. The means of evaluating the prediction-algorithm precision is also proposed. © 1972-2012 IEEE.


Shi J.,North China Electrical Power University | Lee W.-J.,University of Texas at Arlington | Liu Y.,North China Electrical Power University | Yang Y.,North China Electrical Power University | Wang P.,North China Electrical Power University
IEEE Transactions on Industry Applications | Year: 2012

Due to the growing demand on renewable energy, photovoltaic (PV) generation systems have increased considerably in recent years. However, the power output of PV systems is affected by different weather conditions. Accurate forecasting of PV power output is important for system reliability and promoting large-scale PV deployment. This paper proposes algorithms to forecast power output of PV systems based upon weather classification and support vector machines (SVM). In the process, the weather conditions are divided into four types which are clear sky, cloudy day, foggy day, and rainy day. In this paper, a one-day-ahead PV power output forecasting model for a single station is derived based on the weather forecasting data, actual historical power output data, and the principle of SVM. After applying it into a PV station in China (the capability is 20 kW), results show the proposed forecasting model for grid-connected PV systems is effective and promising. © 2012 IEEE.


Wang J.,North China Electrical Power University | Li L.,Beijing Information Science and Technology University
Renewable and Sustainable Energy Reviews | Year: 2016

The development of renewable energy, which is an important way to solve the environmental protection, has now become a research focus around the world. As a developing country with rapid growth, China gains the rapid development of economy, but the environmental pollution is becoming increasingly serious in recent years. Electricity industry plays an important role for energy-saving and emission-reduction in China, in order to reduce the environment pollution, it needs to consider how the electricity consumption affects the carbon emissions. In this paper, a stochastic impacts by regression on population, affluence, and technology (STRIPAT) model was built, which estimates the relationship between the carbon emissions, population, GDP per capita, electricity consumption and energy consumption. It found that population, GDP per capita and the ratio of electricity consumption in energy consumption are change 1%, the carbon emissions will change 1.207%, 0.901% and -1.188% respectively. Based on the relationship, there electricity energy development scenarios were assumed and analyzed, and it found that the way to reduce carbon emissions should consider improving technical ability, which should accounting for improving the ratio of electricity power ratio in the energy consumption, improving the efficiency of using fossil energy and the development of renewable energy. © 2016 Elsevier Ltd. All rights reserved.


Qian D.,CAS Institute of Chemistry | Qian D.,North China Electrical Power University | Ma W.,North Carolina State University | Li Z.,CAS Institute of Chemistry | And 6 more authors.
Journal of the American Chemical Society | Year: 2013

A novel polythiophene derivative, PBT1, was designed, synthesized, and applied in polymer solar cells (PSCs). This work provides a successful example of using molecular structure as a tool to realize optimal photovoltaic performance with high polymer content, thus enabling the realization of efficient photoabsorption in very thin films. As a result, an efficiency of 6.88% was recorded in a PSC with a 75 nm active layer. © 2013 American Chemical Society.


Liu Z.,North China Electrical Power University | Xu B.,Guangdong Power Grid Corporation | Niu D.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

Based on the analysis on development tendency of smart grid in future, the development prospect and ultimate objective of demand response technology based on the platform of smart grid are predicted and revealed. Research results show that the open and interactive smart grid in future is favorable to the development of demand response technology. The game model of demand response among plants, power grid and power consumers based on the platform of smart grid is researched by equilibrium analysis in the game theory, and the game equilibrium of demand response under complete information is discussed while the restrictions to both power suppliers and power consumers are deregulated, and the market rules for the game of demand response are given.


Peng M.,Beijing Jiaotong University | Yang X.,North China Electrical Power University
Chaos | Year: 2010

A detailed analysis of zero distributions in a special polynomial of the form λτ(λ-a1)(λ-a2)⋯(λ-an)-(c+id) is proposed, where all ai(i=1,2,...,) have the same sign. As its applications, new criteria for asymptotic behavior of nonlinear delayed coupled systems with different topological structures are established. All possible bifurcations, including codimension-two bifurcations with 1:4/1:3 strong resonance in such a delayed difference system, are discussed. Numerical simulation gives a solid verification of the theoretical analysis. © 2010 American Institute of Physics.


Wang Z.-G.,North China Electrical Power University | Huang T.,CAS Institute of High Energy Physics
Nuclear Physics A | Year: 2014

In this article, we study the axial-vector mesons Zb(10610) and Zb(10650) with the Cγμ-Cγ5 type and Cγμ-Cγν type interpolating currents, respectively, by carrying out the operator product expansion to the vacuum condensates up to dimension 10. In calculations, we explore the energy scale dependence of the QCD spectral densities of the hidden bottom tetraquark states in detail for the first time, and suggest a formula μ=MX/Y/Z2-(2Mb)2 with the effective mass Mb=5.13 GeV to determine the energy scales. The numerical results favor assigning the Zb(10610) and Zb(10650) as the Cγμ-Cγ5 type and Cγμ-Cγν type hidden bottom tetraquark states, respectively. We obtain the mass of the JPC=1++ hidden bottom tetraquark state as a byproduct, which can be compared to the experimental data in the futures. Furthermore, we study the strong decays Zb±(10610)→ϒ{hooked}π±,ηbρ± with the three-point QCD sum rules, the decay widths also support assigning the Zb(10610) as the Cγμ-Cγ5 type hidden bottom tetraquark state. © 2014 Elsevier B.V.


Chung C.Y.,Hong Kong Polytechnic University | Yu H.,Hong Kong Polytechnic University | Yu H.,North China Electrical Power University | Wong K.P.,University of Western Australia
IEEE Transactions on Power Systems | Year: 2011

Based on a quantum-inspired evolutionary algorithm for unit commitment, this paper proposed ways to advance the efficiency and robustness of the algorithm so that its capacity for application in large-scale unit commitment problems can be significantly enhanced. The paper develops an advanced quantum-inspired evolutionary unit commitment algorithm by developing a new initialization method based on unit priority list and a special Q-bit expression for ensuring diversity in the initial search area for improving the efficiency of solution searching. Different techniques such as multi-observation, single-search, and group-search are also proposed for incorporation in the advanced algorithm. The advanced algorithm is tested and compared with the earlier quantum-inspired evolutionary algorithm and a number of known methods through its applications to test systems with up to 100 generator units for a 24-h scheduling horizon. © 2010 IEEE.


Wang Z.-G.,North China Electrical Power University | Huang T.,CAS Institute of High Energy Physics
European Physical Journal C | Year: 2014

In this article, we construct both the color singlet-singlet type and the octet-octet type currents to interpolate X(3872), Zc(3900), and Zb(10610), and we calculate the vacuum condensates up to dimension-10 in the operator product expansion. Then we study the axial-vector hidden charm and hidden bottom molecular states with the QCD sum rules, explore the energy-scale dependence of the QCD sum rules for the heavy molecular states in details, and we use the formula (Formula Presented) with the effective masses MQ to determine the energy scales. The numerical results support assigning X(3872), Zc(3900), and Zb(10610) as the color singlet-singlet type molecular states with JPC =1++, 1+-, 1+-, respectively, more theoretical and experimental work is still needed to distinguish the molecule and tetraquark assignments; while there are no candidates for the color octet-octet type molecular states. © 2014 The Author(s).


Hu Z.,State Grid Corporation of China | Hu Z.,North China Electrical Power University | Yuan J.,North China Electrical Power University | Hu Z.,University College London
Energy Policy | Year: 2011

Emissions mitigation is a major challenge for China's sustainable development. We summarize China's successful experiences on energy efficiency in past 30 years as the contributions of Energy Usage Management and Integrated Resource Strategic Planning, which are essential for low-carbon economy. In an Economy-Energy-Electricity-Environment (E4) framework, the paper studies the low-carbon development of China and gives an outlook of China's economy growth, energy-electricity demand, renewable power generation and energy conservation and emissions mitigation until 2030. A business-as-usual scenario is projected as baseline for comparison while low carbon energy and electricity development path is studied. It is defined as low carbon energy/electricity when an economy body manages to realize its potential economic growth fueled by less energy/electricity consumption, which can be characterized by indexes of energy/electricity intensity and emissions per-unit of energy consumption (electricity generation). Results show that, with EUM, China, could save energy by 4.38 billion ton oil equivalences (toes) and reduce CO2 emission by 16.55 billion tons; with IRSP, China, could save energy by 1.5Btoes and reduce CO2 emission by 5.7Btons, during 2010-2030. To realize the massive potential, China has to reshape its economic structure and rely much on technology innovation in the future. © 2011 Elsevier Ltd.


Li Y.P.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Nie S.L.,Beijing University of Technology
Advances in Water Resources | Year: 2010

In this study, a fuzzy-boundary interval-stochastic programming (FBISP) method is developed for planning water resources management systems under uncertainty. The developed FBISP method can deal with uncertainties expressed as probability distributions and fuzzy-boundary intervals. With the aid of an interactive algorithm woven with a vertex analysis, solutions for FBISP model under associated α-cut levels can be generated by solving a set of deterministic submodels. The related probability and possibility information can also be reflected in the solutions for the objective function value and decision variables. The developed FBISP is also applied to water resources management and planning within a multi-reservoir system. Various policy scenarios that are associated with different levels of economic consequences when the pre-regulated water-allocation targets are violated are analyzed. The results obtained are useful for generating a range of decision alternatives under various system conditions, and thus helping decision makers to identify desired water resources management policies under uncertainty. © 2010 Elsevier Ltd.


Kirca M.,University of Pittsburgh | Yang X.,North China Electrical Power University | To A.C.,University of Pittsburgh
Computer Methods in Applied Mechanics and Engineering | Year: 2013

Carbon nanotubes (CNTs) are one of the presents of nanotechnology being investigated due to their extraordinary mechanical, thermal and electrical properties. Carbon nanotube networks feed the idea that CNTs can be used as the building blocks of new advanced materials utilizing the superior characteristics of CNTs. In this way, nanoscale features of CNTs can be scaled up to even continuum proportions. In this study, 2-D and 3-D CNT network generation methods are introduced by which the geometrical parameters, such as CNT length, chirality, intersection angle and junctional density, can be controlled and a random CNT network is obtained. Then, molecular dynamics (MD) simulations are used to create covalent bonds between intersecting CNTs, which allow the investigation of the mechanical, thermal and electrical properties of random CNT networks. © 2013 Elsevier B.V.


Wang Z.-G.,North China Electrical Power University | Huang T.,CAS Institute of High Energy Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In this article, we distinguish the charge conjunctions of the interpolating currents, calculate the contributions of the vacuum condensates up to dimension 10 in a consistent way in the operator product expansion, study the masses and pole residues of the JPC=1+± hidden charmed tetraquark states with the QCD sum rules, and explore the energy-scale dependence in detail for the first time. The predictions MX=3.87-0.09+0.09GeV and MZ=3.91-0.09+0.11GeV support assigning the X(3872) and Zc(3900) [or Zc(3885)] as the 1++ and 1+- diquark-antidiquark type tetraquark states, respectively. © 2014 American Physical Society.


Wang Z.-G.,North China Electrical Power University | Huang T.,CAS Institute of High Energy Physics
Physical Review C - Nuclear Physics | Year: 2011

In this Brief Report we calculate the in-medium mass modifications of the scalar mesons D0 and B0 using the QCD sum rules. In calculations we observe that the D0N and B0N scattering lengths are about 1.1 and 4.1fm, respectively, the mass shifts δM D0=69MeV and δMB0=217MeV, and the D 0N and B0N interactions are repulsive. The positive mass shifts indicate that the decays of the higher charmonium states into the D 0D̄0 pair are suppressed. © 2011 American Physical Society.


Qin X.S.,Nanyang Technological University | Xu Y.,North China Electrical Power University
Advances in Water Resources | Year: 2011

Incorporation of uncertainties within an urban water supply management system has been a challenging topic for many years. In this study, an acceptability-index-based two-step interval programming (AITIP) model was developed for supporting urban water supply analysis under uncertainty. AITIP improved upon the traditional two-step interval programming (TIP) through incorporating the acceptability level of constraints violation into the optimization framework. A four-layer urban water supply system, including water sources, treatment facilities, reservoirs, and consuming zones, was used to demonstrate the applicability of proposed method. The results indicated that an AITIP model was valuable to help understand the effects of uncertainties related to cost, constraints and decision maker's judgment in the water supply network, and capable of assisting urban water managers gain an in-depth insight into the tradeoffs between system cost and constraints-violation risk. Compared with TIP, the solutions from AITIP were of lower degree of uncertainty, making it more reliable to identify effective water supply patterns by adjusting decision variable values within their solution intervals. The study is useful in helping urban water managers to identify cost-effective management schemes in light of uncertainties in hydrology, environment, and decisions. The proposed optimization approach is expected to be applicable for a wide variety of water resources management problems. © 2011 Elsevier Ltd.


Liu Y.,North China Electrical Power University | Zhou J.,Wuhan Institute of Technology | Shen T.,Nanjing University of Technology
Materials and Design | Year: 2013

A theoretical model is proposed to study the influence of nano-metal particles (NMPs) on the fracture toughness of metal-ceramic composites (MCC). In the framework of the model, the crack tip intersects the grain boundary of the NMPs. Stress concentration at crack tip initiates edge dislocations which makes a shielding effect on the crack and leads to fracture toughness of the MCC. The dependence of critical crack intensity factors on grain size of the NMPs was calculated. The calculation suggested that the existence of the NMPs lead to an increase of critical crack intensity factors by 14%. © 2012 Elsevier Ltd.


Varhegyi G.,Hungarian Academy of Sciences | Bobaly B.,Hungarian Academy of Sciences | Jakab E.,Hungarian Academy of Sciences | Chen H.,North China Electrical Power University
Energy and Fuels | Year: 2011

The pyrolysis of four biomasses (corn stalk, rice husk, sorghum straw, and wheat straw) was studied at different temperature-time functions in an inert gas flow by thermogravimetric analysis (TGA). Linear and stepwise heating programs were employed. A distributed activation energy model (DAEM) with three pools of reactants (three pseudocomponents) was used because of the complexity of the biomass samples of agricultural origin. Compensation effects were observed between the kinetic parameters as in the works of other investigators. The compensation effects result in ambiguous parameter values; hence, they were eliminated with a decrease in the number of unknown parameters. For this purpose, some of the kinetic parameters were assumed to be the same for the four biomasses. This approach also helps to express the similarities of the samples in the model. The 16 experiments were evaluated simultaneously by the method of least squares, yielding dependable kinetic parameters. The resulting models describe well the experimental data and are suitable for predicting experiments at higher heating rates. The checks on the prediction capabilities were considered to be an essential part of the model verification. © 2010 American Chemical Society.


Zhang Z.,North China Electrical Power University | Kunihiro T.,Kyoto University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We investigate the effects of the axial-anomaly term with a chiral-diquark coupling on the phase diagram within a two-plus-one-flavor Nambu-Jona-Lasinio model under the charge-neutrality and β-equilibrium constraints. We find that when such constraints are imposed, the new anomaly term plays a quite similar role as the vector interaction does on the phase diagram, which the present authors clarified in a previous work. Thus, there appear several types of phase structures with multiple critical points at low temperature T, although the phase diagrams with intermediate-T critical point(s) are never realized without these constraints even within the same model Lagrangian. This drastic change is attributed to an enhanced interplay between the chiral and diquark condensates due to the anomaly term at finite temperature; the u-d diquark coupling is strengthened by the relatively large chiral condensate of the strange quark through the anomaly term, which in turn definitely leads to the abnormal behavior of the diquark condensate at finite T, inherent to the asymmetric quark matter. We note that the critical point from which the crossover region extends to zero temperature appears only when the strength of the vector interaction is larger than a critical value. We also show that the chromomagnetic instability of the neutral asymmetric homogenous two-flavor color-superconducting phase is suppressed and can be even completely cured by the enhanced diquark coupling due to the anomaly term and/or by the vector interaction. © 2011 American Physical Society.


Tong S.W.,Beijing Union University | Qian D.W.,North China Electrical Power University
International Journal of Hydrogen Energy | Year: 2013

A typical working mode for the fuel cell hybrid system is that the fuel cell produces constant power output while the auxiliary storage energy device such as ultracapacitor or battery provides the deviation between the desired power demand and the value of the actual operation. This paper concentrates on the control of the fuel cell flow system. The system which is like an under-actuated mechanical system needs to control two objects (the cathode pressure and the air flow) with one manipulated variable (the set voltage of the air mass flow controller). A SIRMs-based fuzzy inference model is successfully implemented in the system. Online random search optimization algorithm based on Simulink C-S functions is developed to adjust the parameters in the model. By alternative control of the two objects, experimental results demonstrate the realization of the control strategy with one adjustment means. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Yang A.L.,North China Electrical Power University | Huang G.H.,North China Electrical Power University | Qin X.S.,University of Regina | Fan Y.R.,Nanyang Technological University
Journal of Hazardous Materials | Year: 2012

A simulation-based fuzzy multi-criteria decision analysis (SFMCDA) method is developed for supporting the selection of remediation strategies for petroleum contaminated sites. SFMCDA integrates process modeling (using BIOPLUME III) and fuzzy ranking (based on fuzzy TOPSIS) into a general management framework, and can compare various remediation alternatives, in light of both cost-risk tradeoffs and uncertainty impacts. The proposed method is applied to a hypothetical contaminated site suffering from a benzene leakage problem. Six remediation alternatives are taken into consideration, including natural attenuation (NA), pump-and-treat (PAT), enhanced natural attenuation (ENA), and a number of their combinations. Six fuzzy criteria, including both cost and risk information, are used to compare different alternatives through fuzzy TOPSIS. The results demonstrates that the proposed method can help systematically analyze fuzzy inputs from contaminant transport modeling, cost implications and stakeholders' preferences, and provide useful ranking information covering a variety of decision-relevant remediation options for decision makers. © 2012.


Zhang B.Y.,Nanyang Technological University | Zhang B.Y.,North China Electrical Power University | Liu T.,Nanyang Technological University | Meng B.,Nanyang Technological University | And 4 more authors.
Nature Communications | Year: 2013

Graphene has attracted large interest in photonic applications owing to its promising optical properties, especially its ability to absorb light over a broad wavelength range, which has lead to several studies on pure monolayer graphene-based photodetectors. However, the maximum responsivity of these photodetectors is below 10 mA W -1, which significantly limits their potential for applications. Here we report high photoresponsivity (with high photoconductive gain) of 8.61 A W -1 in pure monolayer graphene photodetectors, about three orders of magnitude higher than those reported in the literature, by introducing electron trapping centres and by creating a bandgap in graphene through band structure engineering. In addition, broadband photoresponse with high photoresponsivity from the visible to the mid-infrared is experimentally demonstrated. To the best of our knowledge, this work demonstrates the broadest photoresponse with high photoresponsivity from pure monolayer graphene photodetectors, proving the potential of graphene as a promising material for efficient optoelectronic devices. © 2013 Macmillan Publishers Limited. All rights reserved.


Luo Z.,North China Electrical Power University | Du J.,Beijing Jiaotong University | Xie Z.,CAS Institute of Atmospheric Physics | Guo Y.,North China Electrical Power University
International Journal for Numerical Methods in Engineering | Year: 2011

In this paper, a proper orthogonal decomposition (POD) method is applied to reducing a classical stabilized mixed finite element (SMFE) formulation for the non-stationary Navier-Stokes equations. Error estimates between the classical SMFE solutions and the reduced SMFE solutions based on the POD method are provided. The reduced SMFE formulation based on the POD method could not only greatly reduce its degrees of freedom but also circumvent the constraint of Brezzi-Babuka (BB) condition so that the combination of finite element subspaces could be chosen freely and allow optimal-order error estimates to be obtained. Numerical experiments show that the errors between the reduced SMFE solutions and the classical SMFE solutions are consistent with theoretical results. Moreover, it is shown that the reduced SMFE formulation based on the POD method is feasible and efficient for solving the non-stationary Navier-Stokes equations. © 2011 John Wiley & Sons, Ltd.


Chen Q.,Beijing Jiaotong University | Liu S.,North China Electrical Power University
Chinese Journal of Chemical Engineering | Year: 2012

This study was conducted to investigate the characteristics of meso-scale combustion. The technique of electrical capacitance tomography (ECT) was used to locate flame position and monitor the effect corresponding to varied air/fuel ratio in a meso-scale combustor. Combustion phenomena including igniting, quenching and unsteady combustion have been visualized using ECT. The method of metallization protecting ECT sensor from high temperature damage and the novel calibration method adapted to ECT monitoring of unknown permittivity flame have been shown to be successful. At the same time, electrical nature of combustion and dielectric characteristics of hydrocarbon flame were studied. The relationship between flame permittivity and state parameters of combustion gas was demonstrated preliminarily. © 2012 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP).


Wang Y.,North China Electrical Power University | Yu X.,RMIT University
IEEE Transactions on Industrial Electronics | Year: 2010

A nonlinear model combining boilerturbinegenerator dynamic characteristics for a thermal-power-generation unit is first introduced. Based on the nonlinear model, a new coordinated control design is proposed using the backstepping method incorporating the coordinated passivation approach that considers the entire boiler-turbine-generator system as a whole. The control design consists of three subcontrollers, namely, a main steam valve controller, an excitation controller, and a fuel flow controller. It is shown that the proposed coordinated control design can ensure asymptotical stability of the closed-loop system and improve the electric power regulation performance. Simulation results based on a practical thermal-power-plant model are presented to show the effectiveness of the proposed control design. © 2010 IEEE.


Jing L.,Memorial University of Newfoundland | Chen B.,North China Electrical Power University | Chen B.,Memorial University of Newfoundland
Journal of Environmental Informatics | Year: 2011

Recently, investigation and conservation of subarctic wetlands has been recognized as an attractive route. To gain insight of the interactions between hydrology and atmosphere of the second largest wetland in Canada - the Hudson Bay Lowlands (HBL), the semi-distributed land use-based runoff process (SLURP) hydrological model was applied to a typical subarctic wetland - the Deer River watershed over a 20-year period (1978-1997). Sensitivity analysis, calibration and validation of the model identified a number of distinguishable hydrological features of subarctic wetlands as well as model deficiencies. Snowmelt was the major source of water recharge in subarctic wetlands and constituted approximately half of the average annual runoff in the Deer River watershed. The peaks of the simulated spring runoff were 34% lower than the observed ones in average which could be attributed to the effects of shallow permafrost that impeded the infiltration of melt water. Runoff of rainfall water during the summer season occurred only during storms due to canopy interception, depression storage, soil porosity, impermeable permafrost, and intensive evapotranspiration. A lag of 2-8 days between the peaks of streamflow and rainfall was observed through both field investigation and modeling results. The numerous seasonally connected ponds/lakes stretching over the middle and lower reach of the watershed behaved as buffers and significantly prolonged the concentration time in summer and fall. The findings will help build a scientific basis for advancing the knowledge of the hydrologic cycle and impacts of climatic changes on sub-arctic wetlands. © 2011 ISEIS All rights reserved.


Zhu Y.,Communication University of China | Shi Y.,North China Electrical Power University
IEEE Signal Processing Letters | Year: 2013

We use a small positive parameter to change the total-variation function for unconstrained MR image reconstruction to a strictly convex perturbed function. Bregman iteration is applied to solve the modified total-variation MR image (TVMRI) reconstruction problem. A lagged diffusivity fixed-point algorithm is applied to solve the minimization problem in the Bregman iteration. We use the periodic boundary condition and a Fourier transform to accelerate TVMRI reconstruction. Real MR images are used to test the approach in numerical experiments. The experimental results demonstrate that the proposed method is very efficient for TVMRI reconstruction. © 1994-2012 IEEE.


Sun Y.,North China Electrical Power University | Sun Y.,CAS Hefei Institutes of Physical Science | Ding C.,CAS Hefei Institutes of Physical Science | Cheng W.,CAS Hefei Institutes of Physical Science | And 2 more authors.
Journal of Hazardous Materials | Year: 2014

The reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were synthesized by chemical deposition method and were characterized by SEM, high resolution TEM, Raman and potentiometric acid-base titrations. The characteristic results showed that the nZVI nanoparticles can be uniformly dispersed on the surface of rGO. The removal of U(VI) on nZVI/rGO composites as a function of contact time, pH and U(VI) initial concentration was investigated by batch technique. The removal kinetics of U(VI) on nZVI and nZVI/rGO were well simulated by a pseudo-first-order kinetic model and pseudo-second-order kinetic model, respectively. The presence of rGO on nZVI nanoparticles increased the reaction rate and removal capacity of U(VI) significantly, which was attributed to the chemisorbed OH- groups of rGO and the massive enrichment of Fe2+ on rGO surface by XPS analysis. The XRD analysis revealed that the presence of rGO retarded the transformation of iron corrosion products from magnetite/maghemite to lepidocrocite. According to the fitting of EXAFS spectra, the UC (at ~2.9Å) and UFe (at ~3.2Å) shells were observed, indicating the formation of inner-sphere surface complexes on nZVI/rGO composites. Therefore, the nZVI/rGO composites can be suitable as efficient materials for the in-situ remediation of uranium-contaminated groundwater in the environmental pollution management. © 2014 Elsevier B.V.


Zhao X.,North China Electrical Power University | Li N.,North China Electrical Power University | Ma C.,University of Western Australia
Energy Policy | Year: 2012

Residential energy consumption (REC) is the second largest energy use category (10%) in China and urban residents account for 63% of the REC. Understanding the underlying drivers of variations of urban REC thus helps to identify challenges and opportunities and provide advices for future policy measures. This paper applies the LMDI method to a decomposition of China's urban REC during the period of 1998-2007 at disaggregated product/activity level using data collected from a wide range of sources. Our results have shown an extensive structure change towards a more energy-intensive household consumption structure as well as an intensive structure change towards high-quality and cleaner energy such as electricity, oil, and natural gas, which reflects a changing lifestyle and consumption mode in pursuit of a higher level of comfort, convenience and environmental protection. We have also found that China's price reforms in the energy sector have contributed to a reduction of REC while scale factors including increased urban population and income levels have played a key role in the rapid growth of REC. We suggest that further deregulation in energy prices and regulatory as well as voluntary energy efficiency and conservation policies in the residential sector should be promoted. © 2011 Elsevier Ltd.


An N.,Hefei University of Technology | Zhao W.,Lanzhou University | Wang J.,Lanzhou University | Shang D.,University College of Applied Sciences | Zhao E.,North China Electrical Power University
Energy | Year: 2013

For accurate electricity demand forecasting, this paper proposes a novel approach, MFES, that combines a multi-output FFNN (feedforward neural network) with EMD (empirical mode decomposition)-based signal filtering and seasonal adjustment. In electricity demand forecasting, noise signals, caused by various unstable factors, often corrupt demand series. To reduce these noise signals, MFES first uses an EMD-based signal filtering method which is fully data-driven. Secondly, MFES removes the seasonal component from the denoised demand series and models the resultant series using FFNN model with a multi-output strategy. This multi-output strategy can overcome the limitations of common multi-step-ahead forecasting approaches, including error amplification and the neglect of dependency between inputs and outputs. At last, MFES obtains the final prediction by restoring the season indexes back to the FFNN forecasts. Using the half-hour electricity demand series of New South Wales in Australia, this paper demonstrates that the proposed MFES model improves the forecasting accuracy noticeably comparing with existing models. © 2012 Elsevier Ltd.


Zhao X.,North China Electrical Power University | Ma C.,University of Western Australia
Energy Economics | Year: 2013

In 2003, China's integrated electricity utility - the State Power Corporation (SPC) - was unbundled and dismantled into five generation groups and two grid companies in an effort to increase competition and improve efficiency. In this paper, we study the impact of this deregulation reform on the operational efficiency for a balanced panel of 34 large power plants for the period 1997-2010. We find that on average these power plants have converged to the technological frontier over the sample period. Controlling for substantial heterogeneity in the technical profile, we also find that the unbundling reform has boosted productivity of China's large thermal power plants; however, the presumably differential impacts of the reform on the previously SPC-managed power plants and the independent power producers in our sample are insignificant. © 2013 Elsevier B.V.


Wang W.,Zhejiang University | Wang W.,North China Electrical Power University | Huang J.-H.,Zhejiang University | Sheng Z.-M.,Zhejiang University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The Z→e+e- decay is studied based on the noncommutative standard model with the hybrid gauge transformation. It is shown that if the latter is not included, the noncommutative correction to the amplitude of the Z→e+e- appears only as a phase factor, so that there is no new physical effect on the decay width. However, when the hybrid gauge transformation is included, the noncommutative effect appears in the two-body decay process. The discrepancy between the experimental branch ratio and the standard model prediction allows us to set the bound on the noncommutative parameters. © 2013 American Physical Society.


Teng J.,North China Electrical Power University | Snoussi H.,University of Technology of Troyes | Richard C.,University of Nice Sophia Antipolis
IEEE Transactions on Mobile Computing | Year: 2010

The prime motivation of our work is to balance the inherent trade-off between the resource consumption and the accuracy of the target tracking in wireless sensor networks. Toward this objective, the study goes through three phases. First, a cluster-based scheme is exploited. At every sampling instant, only one cluster of sensors that located in the proximity of the target is activated, whereas the other sensors are inactive. To activate the most appropriate cluster, we propose a nonmyopic rule, which is based on not only the target state prediction but also its future tendency. Second, the variational filtering algorithm is capable of precise tracking even in the highly nonlinear case. Furthermore, since the measurement incorporation and the approximation of the filtering distribution are jointly performed by variational calculus, an effective and lossless compression is achieved. The intercluster information exchange is thus reduced to one single Gaussian statistic, dramatically cutting down the resource consumption. Third, a binary proximity observation model is employed by the activated slave sensors to reduce the energy consumption and to minimize the intracluster communication. Finally, the effectiveness of the proposed approach is evaluated and compared with the state-of-the-art algorithms in terms of tracking accuracy, internode communication, and computation complexity. © 2006 IEEE.


Zhao X.,North China Electrical Power University | Lyon T.P.,University of Michigan | Song C.,North China Electrical Power University
Applied Energy | Year: 2012

China's electricity industry has experienced two major stages of development: from 1949 to 1984, the industry was treated as a subordinate sector whose goal was to support the development of other industrial sectors; since 1985, a series of reforms in its governance mechanisms have been carried out. This paper applies transaction-cost analysis to provide a new perspective on the efficiency of these reforms, emphasizing changes in the areas of electricity prices and investment incentives. We argue that the governance reforms successfully ended the significant social welfare losses resulting from the severe power shortages of the previous 30. years, introduced real or potential competition, and encouraged technological progress. However, they also led to low operational efficiency and excessive investment in power generation plants. Our empirical analysis, uses panel regression models, shows that by 2003 the reforms led electric capacity to increase tremendously. Meanwhile, the electricity price reform in 1996 promoted power generation corporations more responsive to electricity demand and price signals to some extend. However, it cannot be proved that the electricity price reform in 2003 (and the dismantle reform at the end of 2002) affect electricity generation corporations in the same way. © 2012 Elsevier Ltd.


Zhao X.,North China Electrical Power University | Lyon T.P.,University of Michigan | Wang F.,Shanghai University of Finance and Economics | Song C.,North China Electrical Power University
Energy Policy | Year: 2012

The asymmetry of Chinese coal and electricity pricing reforms leads to serious conflict between coal suppliers and electricity utilities. Electricity utilities experience significant losses as a result of conflict: severe coal price fluctuations, and uncertainty in the quantity and quality of coal supplies. This paper explores whether establishing cooperative relationships between coal suppliers and electricity utilities can resolve conflicts. We begin with a discussion of the history of coal and electricity pricing reforms, and then conduct a theoretical analysis of relational contracting to provide a new perspective on the drivers behind the establishment of cooperative relationships between the two parties. Finally, we empirically investigate the role of cooperative relationships and the establishment of mine-mouth power plants on the performance of electricity utilities. The results show that relational contracting between electricity utilities and coal suppliers improves the market performance of electricity utilities; meanwhile, the transportation cost savings derived from mine-mouth power plants are of importance in improving the performance of electricity utilities. © 2012 Elsevier Ltd.


Xiang L.,North China Electrical Power University | Yang S.,Zhejiang University | Gan C.,Zhejiang University
Optics and Lasers in Engineering | Year: 2012

In this work, a laser torsional vibrameter was used to measure the torsion vibration of a rotating shaft system under electrical network impact. Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) are non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. Furthermore, a highly complex shafting system is analyzed by a modified Riccati torsional transfer matrix. The system is modeled as a chain consisting of an elastic spring with concentrated mass points, and the multi-segments lumped mass model is established for this shafting system. By the modified Riccati torsional transfer matrix method, an accumulated calculation is effectively eliminated to obtain the natural frequencies. The electrical network impacts can activize the torsional vibration of shaft system, and the activized torsion vibration frequencies contained the natural frequencies of shaft system. The torsional vibrations of the shaft system were measured under electrical network impacts in laser Doppler torsional vibrometer. By comparisons, the natural frequencies by measurement were consistent with the values by calculation. The results verify the instrument is robust, user friendly and can be calibrated in situ. The laser torsional vibrometer represents a significant step forward in rotating machinery diagnostics. © 2012 Elsevier Ltd.


Tan Z.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Wang J.,Argonne National Laboratory | Xu J.,North China Electrical Power University
Applied Energy | Year: 2010

This paper proposes a novel price forecasting method based on wavelet transform combined with ARIMA and GARCH models. By wavelet transform, the historical price series is decomposed and reconstructed into one approximation series and some detail series. Then each subseries can be separately predicted by a suitable time series model. The final forecast is obtained by composing the forecasted results of each subseries. This proposed method is examined on Spanish and PJM electricity markets and compared with some other forecasting methods. © 2010 Elsevier Ltd.


Zhao X.,North China Electrical Power University | Zhao X.,University of Michigan | Ma C.,University of Western Australia | Hong D.,North China Electrical Power University
Energy Policy | Year: 2010

Despite the fact that China's energy intensity has continuously decreased during the 1980s and mostly 1990s, the decreasing trend has reversed since 1998 and the past few years have witnessed rapid increase in China's energy intensity. We firstly conduct an index decomposition analysis to identify the key forces behind the increase. It is found that: (1) the high energy demand in industrial sectors is mainly attributed to expansion of production scale, especially in energy-intensive industries; (2) energy saving mainly comes from efficiency improvement, with energy-intensive sectors making the largest contribution; and (3) a heavier industrial structure also contributes to the increase. This study also makes the first attempt to bridge the quantitative decomposition analysis with qualitative policy analyses and fill the gap between decomposition results and policy relevance in previous work. We argue that: (1) energy efficiency improvement in energy-intensive sectors is mainly due to the industrial policies that have been implemented in the past few years; (2) low energy prices have directly contributed to high industrial energy consumption and indirectly to the heavy industrial structure. We provide policy suggestions in the end. © 2009 Elsevier Ltd.


Yuan J.,North China Electrical Power University | Hou Y.,China Electricity Council | Xu M.,University of Michigan
Renewable and Sustainable Energy Reviews | Year: 2012

China has pledged to reduce its CO 2 emissions per unit of GDP by 40-45% by 2020 as of 2005 level. This research examines China's 2020 carbon intensity target and its interdependence with the overarching national economic and social development goals. The results show that, with annual GDP growth rate at 7% during the 12th Five-Year-Plan (FYP) period and 6% during the 13th FYP period, the 45% CO 2 intensity reduction target implies annual CO 2 emissions of 8600 million tonnes by 2020, close to 8400 million tonnes, the UNFCCC 450 ppm scenario for China. However, achieving only the 40% reduction target will lead to 9380 million tonnes CO 2 emissions in 2020 which largely surpass the UNFCCC 450 ppm scenario. We conclude that Chinas 45% CO 2 intensity reduction target is not only within international expectations but also self-consistent with its overall economic and social development strategy. Then primary energy and power planning for implementing the 45% carbon intensity reduction target is proposed. Related investment requirements are also estimated. To achieve the target, China needs to restructure the economic structure for significant improvements in energy conservation. © 2012 Elsevier Ltd. All rights reserved.


Yuan J.-H.,North China Electrical Power University | Yuan J.-H.,University of Michigan | Lyon T.P.,University of Michigan
Renewable and Sustainable Energy Reviews | Year: 2012

Carbon capture and storage (CCS) is the only technology available to mitigate greenhouse gas (GHG) emissions from large-scale fossil fuel usage. U.S. and China are the world's largest GHG emitters. Collaboration between the two nations, therefore, offers the greatest opportunity for achieving meaningful reductions in global GHG emissions. Two countries' current cooperation on CCS through Clean Energy Research Center based on the U.S.-China Strategic Forum on Clean Energy Cooperation mechanism provides an important initial step towards even closer and stronger cooperation in the future. In this paper, we justify such possibility by discourse on the seemly different but complementary social-political context in two countries including political system, government structure, economic policy, national innovation system, energy strategy, and energy market structure. We further address the key elements of future cooperation model by carefully considering the principle of equality and mutual beneficiary, the role of two countries in the whole value chain according to their comparative advantages, and the scale and mechanism of the funding. A milestone for the cooperation until 2030 is drafted and priority areas for both countries in the cooperation are identified. Such cooperation will provide the imperative leadership for global climate change and speed up the global CCS deployment. © 2012 Elsevier Ltd.


Wang W.,North China Electrical Power University | Wang W.,Zhejiang University
European Physical Journal C | Year: 2013

In this paper, we carry out a numerical and systematic analysis of the neutrino mass textures, which contain one vanishing minor and equality between two cofactors. Among 60 logically possible textures, only eight of them are excluded for both the normal and inverted hierarchy by the current experimental data at 3σ level. We also demonstrate that the future long-baseline neutrino oscillation experiments, especially for the measurement of the θ 23 mixing angle, will play an important role in the model selection. The phenomenological implications from neutrinoless double-beta decay and the cosmology observation are also examined. A discussion of the flavor symmetry realization of the textures is also given. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.


Zhu H.,University of Regina | Huang W.W.,McMaster University | Huang G.H.,University of Regina | Huang G.H.,North China Electrical Power University
Applied Energy | Year: 2014

In this study, an inexact mixed-integer fractional energy system planning (IMIF-EP) model is developed for supporting sustainable energy system management under uncertainty. Based on a hybrid of interval-parameter programming (IPP), fractional programming (FP) and mixed integer linear programming (MILP) techniques, IMIF-EP can systematically reflect various complexities in energy management systems. It not only handles imprecise uncertainties and dynamic features associated with power generation expansion planning, but also optimizes the system efficiency represented as output/input ratios. An interactive transform algorithm is proposed to solve the IMIF-EP model. For demonstrating effectiveness of the developed approach, IMIF-EP is applied to support long-term planning for an energy system. The results indicate that interval solutions obtained from IMIF-EP can provide flexible schemes of resource allocations and facility expansions towards sustainable energy management (SEM) under multiple complexities. A comparative economical energy management (EEM) system is also provided. Compared with least-cost models that optimize single criterion, IMIF-EP can better characterize practical energy management problems by optimizing a ratio between criteria of two magnitudes. In application, IMIF-EP is advantageous in balancing conflicting objectives and reflecting complicated relationships among multiple system factors. © 2013 Elsevier Ltd.


He C.,Chongqing University | Liu C.,Chongqing University | Gao H.,Chongqing University | Xie H.,Chongqing University | And 3 more authors.
Energy | Year: 2012

A theoretical formula is proposed to calculate the OET (optimal evaporation temperature) of subcritical ORC (organic Rankine cycle) based on thermodynamic theory when the net power output is selected as the objective function. The OETs of 22 working fluids including wet, isentropic and dry fluids are determined under the given conditions. In order to compare the accuracy of these results, the quadratic approximation method in EES (Engineering Equation Solver) is used to optimize the net power output and the OETs are obtained by numerical simulation. The results show that the OETs calculated by the theoretical formula are consistent with the numerical simulation results. In addition, the average computational accuracy of OETs from the theoretical formula is higher than that from the simplified formula recommended by the related literature. The larger net power output will be produced when the critical temperature of working fluid approaches to the temperature of the waste heat source. According to the maximum net power output, suitable working pressure, total heat transfer capacity and expander SP (size parameter), R114, R245fa, R123, R601a, n-pentane, R141b and R113 are suited as working fluids for subcritical ORC under the given conditions in this paper. © 2011 Elsevier Ltd.


Hu Q.,North China Electrical Power University | Huang G.,North China Electrical Power University | Cai Y.,Dalhousie University | Huang Y.,North China Electrical Power University
Applied Energy | Year: 2011

In this study, a feasibility based inexact fuzzy programming approach (FBIFP) was developed and applied to the planning of a regional electric power generation system (REPGS). As an extension of existing interval linear programming and fuzzy linear programming, FBIFP could tackle uncertainties expressed as intervals, fuzzy sets as well as their combination in both of the objective function and constraints. Through introducing the index of feasibility degree, FBIFP could be used to facilitate the efficient reflection of constraint violation, and thus allow decision makers to have a complete view of the relationships between uncertain inputs and the related solutions. A hypothetic regional electric power generation system was provided for demonstrating applicability of the developed model. Useful solutions for the planning of REPGS were generated. Interval solutions under different feasibility degrees were obtained. They could be used for helping decision makers identify desired alternatives under various reliability risks of the system. The solutions could also help identify optimal patterns for energy resources allocation, electricity generation and facility capacity expansion with a minimized system cost. Tradeoffs between system costs and system security could be successfully addressed through the analysis of the feasibility degrees of constraints, i.e., a higher feasibility degree would correspond to a higher system cost, while a lower system cost would run into a higher risk of potential instability of the study system. © 2011 Elsevier Ltd.


Wang Z.-G.,North China Electrical Power University | Tian Y.-F.,Hefei University of Technology
International Journal of Modern Physics A | Year: 2015

In this paper, we tentatively assign the Y(4140), Y(4274) and X(4350) to be the scalar and tensor csc¯s¯ tetraquark states, respectively, and study them with the QCD sum rules. In the operator product expansion, we take into account the vacuum condensates up to dimension-10. In calculations, we use the formula μ = √M2 X/Y/Z- (2M{double-struck}c)2to determine the energy scales of the QCD spectral densities. The numerical results favor assigning the Y(4140) to be the JPC= 2++diquark-antidiquark type tetraquark state, and disfavor assigning the Y(4274) and X(4350) to be the 0++or 2++tetraquark states. © 2015 World Scientific Publishing Company.


Guo C.,North China Electrical Power University | Guo C.,University of Manitoba | Zhang Y.,University of Manitoba | Gole A.M.,University of Manitoba | Zhao C.,North China Electrical Power University
IEEE Transactions on Power Delivery | Year: 2012

The impact of a voltage source converter-based HVDC (VSC-HVDC) infeed on a line-commutated converter-based HVDC infeed (LCC-HVDC) at the same busbar is investigated. Steady-state aspects such as the maximum available power (MAP) as well as transient aspects such as temporary overvoltage (TOV) and commutation failure immunity index are considered in the analysis. The results show that VSC-HVDC improves the maximum available power, reduces TOV, and makes the LCC-HVDC less susceptible to commutation failure. The resulting improvement in performance of the LCC-HVDC is quantified by a proposed "apparent increase in short circuit ratio" (AISCR) index. AISCR is a measure of the increase in short-circuit ratio for the LCC-HVDC that would be necessary in the absence of the VSC-HVDC link to obtain similar performance. The analytical results are validated by a detailed electromagnetic transient simulation. © 2012 IEEE.


Chen X.,North China Electrical Power University | Gole A.M.,University of Manitoba | Han M.,North China Electrical Power University
IEEE Transactions on Power Delivery | Year: 2012

This paper investigates interconverter interactions in multi-infeed systems that include both rectifiers and inverters. Performance indices used earlier for multi-inverter systems are extended to include the rectifier-inverter mix. These indices can be used to predict the maximum available power (MAP) and power stability limits of the converters as well as transient phenomena, such as transient overvoltages (TOV) and inverter commutation failures (CF ).The results show that the presence of a rectifier in the neighborhood of inverters is effectively similar to an increase in the inverters' short-circuit ratio in that the inverters achieve a higher MAP, are less susceptible to commutation failure, and have smaller TOV. © 2012 IEEE.


Wang W.,North China Electrical Power University | Lao Y.-C.,North China Electrical Power University | Song Y.-L.,North China Electrical Power University
Environment, Energy and Sustainable Development - Proceedings of the 2013 International Conference on Frontier of Energy and Environment Engineering, ICFEEE 2013 | Year: 2014

Green economy is an ideal economic model conformed to the requirements of the sustainable development. Smart grid is the ideal future grid getting the whole world's attention. Begin with the essence, connotation of green economy, this paper had a detailed analysis of green economy and established a green economy developing indexes system. Then this paper did further research on its facilitating function from smart grid to green economy and the coordinated development of green economy and strong smart grid. Finally, this paper put forward some targeted suggestions to the coordinated development of green economy and strong smart grid. © 2014 Taylor & Francis Group, London.


Liu H.-Y.,North China Electrical Power University
Conference Proceedings of the 4th International Symposium on Project Management, ISPM 2016 | Year: 2016

Word widely speaking, solar energy will be dominating resource in the future, and PV industry will be the pillar industry in power industry. With rapidly developing for many years, PV power industry has met problems about operation management and efficiency promotion. It is a general trend for competition intensifying between different PV enterprises to build a complete operation pattern. In this paper, STOW analytical method is used for football marketing strategy. Furthermore, marketing mix has been deeply analyzed for football marketing strange.


Yu J.,North China Electrical Power University | Ren J.,North China Electrical Power University | Zhou M.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

Grid-connection of large-scale wind farm with stochastic, fluctuating and counter-peak load regulation features brings severe challenges to dispatching and operation of power grid. According to the output characteristics of wind power generation system, based on smart energy management system (SEMS) a joint dispatching strategy for wind farm and pumped-storage power station is proposed, and based on stochastic programming a dynamic economic dispatching model for power grid with joint-operated wind farm and pumped-storage power station, in which the minimized fluctuation of wind power output alleviated by pumped-storage power and the lowest operating cost of thermal power plants are taken as the objectives, is built and the built model is solved by chaotic particle swarm optimization algorithm. Simulation results of a joint dynamic dispatch of a certain regional power grid composed of thermal plants, wind farm and pumped-storage power station show that the proposed dynamic economic dispatching strategy is reasonable and effective.


Huang W.,North China Electrical Power University | Zhang X.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

The accuracy of traditional weighted average based dynamic equivalent model for single wind power generator is hard to meet the demand of security and stability analysis of power grid containing large-scale wind farms, and the accuracy of wind farm model can be improved to a great extent if wind power generators were clustered according to a certain index and then a multi machine equivalent model of wind farm was built. Through feature analysis the reasonable clustering index for wind power generators is determined and the reasonableness of the index is expounded by physical meaning. Based on this clustering index an accurate multi machine equivalent model for wind farm is built, and the active and reactive output curves of the built model are almost the same as those of the detailed wind farm model under fluctuation of wind speed or under three-phase short-circuit fault occurred at grid side. The reasonableness of the clustering index is verified by simulation results, however such a clustering index is attained based on correlation analysis of linearized state equation, so the reasonableness of the clustering index under large disturbance should be further researched.


Li Y.,North China Electrical Power University | Yu X.,North China Electrical Power University | Wang Z.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

Due to long construction cycle, massive investment and many involved aspects of photovoltaic (PV) power generation, various uncertain factors and environmental factors, which both PV generation project and project manager have to be faced with, sharply increase and various risks going with the item appear, so it is of great significance to perform effective risk assessment on PV generation project. According to typical features of PV generation project, a more comprehensive risk assessment index system is proposed, in which the grey correlation analysis and technique for order preference by similarity to ideal solution (TOPSIS) method is utilized to construct a grey ideal value approximation model, to assess the risks in PV generation project. Using the proposed risk assessment index system, results of empirical research on eight PV generation projects that will be constructed in a certain province in Northwest China show that using the proposed method the overall evaluation on alternate schemes can be implemented and the differences between alternate schemes, in which the variation tendency of internal factors of alternate schemes and the ideal scheme can be reflected, therefore the proposed risk assessment method is effective.


Zhao X.-G.,North China Electrical Power University | Wei Y.-A.,North China Electrical Power University | Ren L.-Z.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2015

China's wind power industry experienced rapid growth before 2009. However, the growing rate slowed down and the problem of wind curtailment was serious recent years. This paper focuses on the analysis of the turning point of China's wind power industry combing with life circle theory. With a panoramic view of status quo, based on the resource endowment, capacity development and future trends, we draw the following conclusions: (1) China's potential wind power reserves are still rich and the development of wind power industry will sustain growth for some period in the future. (2) As for market structure aspect, oligopolistic characteristic of China's wind power market is still obvious. The market share of China's wind power generation is not very high enough in the total generation market. (3) Turning point of China's wind power industry has not come yet and the slowing down of development speed at present is mainly caused by inappropriate government intervention. It is estimated the turning point of wind power industry will come around 2020. © 2014 Elsevier Ltd. All rights reserved.


Tan Z.,North China Electrical Power University | Chen K.,North China Electrical Power University | Liu P.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2015

Forestry biomass resource has many advantages, which makes it a significant new energy to substitute fossil energy as an important role of biomass resources. For the utilization of China's forestry biomass resources, this paper analyzed the possibilities of its development from the aspect of policy, resource endowment, market and technology, and discussed its development challenges from the aspect of policy, economy, society, technology and resource endowment. Forestry biomass resources are very abundant in China. It has made a significant breakthrough in forest biomass resource utilization, with great prospects. Although there are still some difficulties and challenges in the policy, resource endowment and other aspects, these challenges are not insurmountable. Therefore, forestry biomass resources should develop in a way with Chinese characteristics considering the national condition. © 2014 Elsevier Ltd.


Ming Z.,North China Electrical Power University | Li S.,North China Electrical Power University | Yanying H.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2015

Abstract Demand-side management (DSM) is an effective means to construct low-carbon electricity system, improve energy efficiency and fastly enhance the sustainable development of economy. DSM in China has entered a period of rapid development. A series of policies and regulations related to DSM have been issued by some national ministries in China. However, some problems exist in the implementation of DSM. In view of that, the current situation of DSM development in China is analyzed in this paper from the three aspects of policies and regulations related to DSM, DSM organizational management and DSM development of representative regions. Following that, the challenges faced in DSM implementation are discussed and feasible measures are proposed based on the challenges. This paper is conducive to give impetus to the development of DSM in China. © 2015 Elsevier Ltd.


Shen J.,North China Electrical Power University | Luo C.,North China Electrical Power University
Renewable and Sustainable Energy Reviews | Year: 2015

China is vast, abundant and particularly plentiful in energy sources, due to which it has obtained remarkable achievements on economy. However, its energy structure is too simple to support the sustainable development of economy as coal still contributes to the majority of energy consumption in China. As a consequence, Renewable Energy Law was enacted in 2005, and Chinese government announced a series of policies to boom renewable energy industry. Subsidy policy is one of the major forms of these policies. This paper aims to present these subsidy policies and to analyze their effects according to relative data in energy industry 2005-2013, to find out the deficiencies and enlighten possible policy improvements. The original intentions and abstracts of 5 different levels of subsidy related policies are summarized, and the effects in reality are attentively analyzed. It can be concluded that subsidy policies have different short-term effect on different renewable energies, and they all show some negative effect to a certain extent. 6 core problems are summarized in this paper, and remedy strategies are suggested. © 2014 Elsevier Ltd. All rights reserved.


Xu L.,North China Electrical Power University | Xu J.,North China Electrical Power University
International Journal of Heat and Mass Transfer | Year: 2012

The flow boiling heat transfer in a single microchannel was investigated with pure water and nanofluid as the working fluids. The microchannel had a size of 7500 × 100 × 250 μm, which was formed by two pyrex glasses and a silicon wafer. A platinum film with a length of 3500 μm and a width of 80 μm was deposited at the bottom channel surface, acting as the heater and temperature sensor. The nanofluid had a low weight concentration of 0.2%, consisting of de-ionized water and 40 nm Al 2O 3 nanoparticles. The nanoparticle deposition phenomenon was not observed. The boiling flow displays chaotic behavior due to the random bubble coalescence and breakup in the milliseconds timescale at moderate heat fluxes for pure water. The flow instability with large oscillation amplitudes and long cycle periods was observed with further increases in heat fluxes. The flow patterns are switched between the elongated bubbles and isolated miniature bubbles in the timescale of 100 s. It is found that nanofluid significantly mitigate the flow instability without nanoparticle deposition effect. The boiling flow is always stable or quasi-stable with significantly reduced pressure drop and enhanced heat transfer. Miniature bubbles are the major flow pattern in the microchannel. Elongated bubbles temporarily appear in the milliseconds timescale but isolated miniature bubbles will occupy the channel shortly. The decreased surface tension force acting on the bubble accounts for the smaller bubble size before the bubble departure. The inhibition of the dry patch development by the structural disjoining pressure, and the enlarged percentage of liquid film evaporation heat transfer region with nanoparticles, may account for the heat transfer enhancement compared to pure water. © 2012 Elsevier Ltd. All rights reserved.


Sun D.-L.,North China Electrical Power University | Xu J.-L.,North China Electrical Power University | Wang L.,North China Electrical Power University
International Communications in Heat and Mass Transfer | Year: 2012

In this paper, a vapor-liquid phase change model is proposed for volume-of-fluid (VOF) method in FLUENT. This model is suitable for the case in which both unsaturated phase and saturated phase are present. In this model: (1) the unsaturated-phase thermal conductivity λ uns and specific heat C p,uns are actual physical parameters; (2) the saturated-phase thermal conductivity λ s and specific heat C p,s are assumed as zero and C p,uns, respectively; (3) the interfacial mass-transfer rate ṁ s=-ṁ uns=2λuns(∇αuns{dot operator}∇T)/L. Finally, the accuracy of the vapor-liquid phase change model is verified by one-dimensional Stefan problem and two-dimensional film boiling problem. © 2012 Elsevier Ltd.


Zhao X.,North China Electrical Power University | Zhang S.,North China Electrical Power University | Fan C.,North China Electrical Power University
Environmental Pollution | Year: 2014

Along with China's rapid economic growth, the environmental externality in the country is getting more and more serious. China's environmental externality is accompanied by environmental inequality, which presents two characteristics: First, the health loss caused by environmental externality is concentrated in the elderly and children. We take Beijing as an empirical analysis to conclude that children (0-4 years old) are the largest group suffered from respiratory disease; while the seniors are the largest group suffered from cardiovascular disease. Second, China's environmental inequality is mainly caused by the transfer of industries from urban to rural areas/suburbs. The villagers in poor rural areas are the biggest victims. China's environmental inequality is reflected particularly by the phenomenon of "cancer villages" which has existed ever since the end of 1970s. Finally, policy recommendations are provided for reducing China's environmental externality and inequality. © 2014 Published by Elsevier Ltd.


Jiao C.-Q.,North China Electrical Power University | Niu S.,North China Electrical Power University
Wuli Xuebao/Acta Physica Sinica | Year: 2013

The shielding effectiveness of an apertured rectangular cavity against the near-field waves of both electric and magnetic dipoles is investigated theoretically by using an extended equivalent circuit method. Both electric and magnetic shielding effectivenesses are calculated as functions of distance between the dipoles and the enclosure. It is shown that the near-field shielding effectiveness is lower than the far-field (plane-wave) shielding effectiveness. Also, in the near-field region, the shielding effectiveness will reduce obviously with the decrease of the source-to-enclosure distance. Based on Bethe's small aperture coupling theory, analytical formulas are presented to describe the quantitative relation between the near-field and the far-field shielding effectivenesses. It is shown that the results from equivalent circuit method are in good agreement with the relation obtained from the Bethe's theory. © 2013 Chinese Physical Society.


Zhao D.,North China Electrical Power University | Zhang N.,North China Electrical Power University | Liu Y.,North China Electrical Power University | Zhang X.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

Microgrid is an effective approach to solve the grid-connection of distributed generations, and the hybrid microgrid composed of wind farm, photovoltaic generation and energy storage system possesses the feature that the clean energy can be fully utilized and its operation is reliable. The smooth switching between grid-connected operation mode and islanded operation mode of microgrid is an important measure to ensure the secure and reliable operation of microgrid. For this reason, a synthetical control strategy integrating new type of master-slave control with peer-to-peer control is adopted to control the operation mode transition between grid-connected operation mode and islanded operation mode of microgrid. A model of microgrid composed of complementary wind farm, photovoltaic generation and energy storage system is constructed on DigSILENT/PowerFactory platform, and the feasibility of the proposed control strategy is verified by simulation results. Besides, simulation results also show that the improved control strategy can ensure power balance of microgrid before and after the switching and keep the voltage of the bus connected with microgrid and frequency of the microgrid within the allowed range.


Liang H.,North China Electrical Power University | Gu X.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

After the blackout occurred, the restoration of interconnected power grid can be quickened by dividing the power grid into several sub-networks for the restoration. A spectral clustering algorithm-based partitioning of sub-networks for the black-start is researched. Based on the number of black-start power sources and their distribution, taking similarity in divided sizes of sub-networks and tightness on internal relation inside sub-networks as the principles for the partitioning of sub-networks, the clustering computation, in which corresponding elements of nodes in the smallest and the second smallest nontrivial eigenvectors are taken as clustering objects, is performed to obtain the scheme for the partitioning of sub-networks. The proposed algorithm is based on community finding principle of complex network, so it possesses sound theoretical basis. The effectiveness of the proposed algorithm is verified by simulation results of IEEE 39-bus system and IEEE 118-bus system.


Xu R.,North China Electrical Power University | Wang Y.,China Electric Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2013

In allusion to precise judgment of security situation of electric power information network, a machine learning-based method for security situation awareness (SSA) is proposed and applied to actual environment. The proposed method abstracts the SSA as classification problem, and the records of actual field monitoring devices are taken as data source and input into classifier to attain awareness results. Based on ball vector machine a classifier is designed, and using quantum genetic algorithm the optimal training parameters of ball vector machine are searched to improve classification accuracy. Results of experiments based on KDD Cup 99 data set and actual operation of SSA system show that the proposed SSA system is better than traditional methods in the accuracy of situation awareness.


Luo Y.,North China Electrical Power University | Li Y.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

In allusion to incomplete information and strong subjectivity of index weights in present comprehensive decision-making of power transmission network planning, based on the combination of entropy weight with grey correlation analysis a comprehensive decision-making method for transmission network planning is proposed. Firstly, the entropy weight is used to determine objective weights of evaluation indices to remedy the insufficiency of average index weight and experts assigned index weight in original grey correlation; then the optimal scheme is obtained by improved grey correlation analysis. The combination of entropy weight with grey correlation analysis can fully utilize overall information of each index and give full play to the superiority of grey correlation that it is suitable for small sample events with a certain gray level. The effectiveness of the proposed method is verified by simulation results of IEEE Garver-6 system.


Fan X.,North China Electrical Power University | Zhu Y.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

In view of the poor accuracy in present fault location methods for multi-terminal transmission lines, a fault location method based on the principle of double-ended traveling wave is applied to fault location for multi-terminal transmission lines and a novel traveling wave based fault location scheme for multi-terminal transmission lines based on fast intrinsic mode decomposition (FIMD) and Teager energy operator (TEO) is proposed. Firstly, FIMD is applied to aerial mode component of each measured current wave and TEO is applied to calculate the instantaneous energy of first intrinsic mode function (IMF1), whose frequency is the highest among intrinsic mode functions obtained from FIMD, and the arrival time of initial fault traveling wave can be determined according to the first sudden arising of energy in the instantaneous energy of IMF1; secondly, the principle of double-ended traveling wave and the arrival times of the initial fault traveling waves are used to form the identification matrix for the faulty section, and the faulty section can be identified according to characteristics of elements in the formed identification matrix; finally, the busbar, which can form most two terminal lines through the fault point, is selected as the initial terminal and the fault distances of these double-ended sections from the initial point via faulty point to other nodes are calculated, and the average value of these fault distances is taken as the final fault distance. Result of PSCAD/EMTDC based simulation of a 220kV transmission network with five terminals shows that using the proposed method the arrival time of initial fault traveling wave can be detected accurately and rapidly, and then the faulty section can be located exactly.


Li H.,North China Electrical Power University | Guo S.,North China Electrical Power University | Tang H.,North China Electrical Power University | Li C.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

As for the pricing by electrical energy quality and the decision of rewards and penalties based on the examination at assessment point, Comprehensive evaluation on power quality is one of the principal foundations. A comprehensive power quality evaluation model based on improved matter-element extension model with variable weight, in which the classical domain of matter-element extension model and the maximum membership criterion are improved to remedy its boundedness and defects in the evaluation of power quality, is proposed. Meanwhile, applying variable weight theory the weights of all rating indices are determined to reduce the influence of subjective factors during the power quality evaluation and incarnate the active participation of evaluated objects during the comprehensive evaluation. Taking measured data form busbar of a certain 110 kV for example, the evaluation result shows that the grade of power quality is qualified but far from being satisfied. Case study shows that the proposed model is effective for comprehensive evaluation of power quality.


Zhu D.,North China Electrical Power University | Gu X.,North China Electrical Power University | Zhong H.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

Most post-blackout unit restoration strategies are based on single-objective optimization and factors influencing the starting sequence of units are neglected. A multi-objective optimization strategy for post-blackout unit restoration is proposed and a multi-objective optimization model for unit restoration, in which following items are taken as optimization objectives: the generating capacity of restored units should be as much as possible, the restored units should be distributed in the network frame level as possible and the restored units are favorable to the restoration of important loads and follow-up units to be restored in power plant level, is built. Firstly, the restoration process is divided into a series of restoration steps to be executed sequentially; secondly, the optimization of each restoration step is turned into multi-objective 0/1 knapsack problem and combining with the shortest path method the restoration paths for unit restoration scheme are searched, and then the restoration paths are solved by fast and elitist non-dominated sorting genetic algorithm and classic Dijkstra algorithm is employed to select restoration paths; finally, the Pareto optimal solutions are sorted to determine the optimal solution. The effectiveness of the proposed method is verified by simulation results of New England 10-machine 39-bus system.


Wu L.,North China Electrical Power University | Huang S.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

The selectivity of inverse-time zero-sequence current protection during earth fault occurred within parallel double-circuit transmission lines is analyzed. Research result shows that as for other transmission lines adjacent to both sides of the parallel double-circuit transmission lines the zero-sequence current in the formers is not always less than that in the parallel double-circuit transmission lines, so that the non-selective action of inverse-time zero-sequence current protections for the adjacent transmission lines may occur. For the faulty line itself the zero-sequence current at the end that is more distant to the fault point end may be larger than that at the opposite end nearer to the fault point, so the protection equipped at the more distant end may act earlier than the protection equipped at the nearer end; the protection equipped for the non-faulty line of the double-circuit lines will not act earlier that that equipped for the faulty line, so its selectivity can be ensured. Therefore, the possibility of misoperation of the protection is dependent upon zero-sequence parameters of transmission lines adjacent to both sides of the double-circuit transmission lines and the position of fault point, and is not dependent upon the zero-sequence parameters and zero-sequence mutual inductance of double-circuit transmission line themselves. Meanwhile, a wide area information-based inverse-time zero-sequence current protection algorithm is put forward, which can improve the speed of the protection while the selectivity of the protection is enhanced. The correctness of above-mentioned analysis is verified by simulation results.


Yang J.,North China Electrical Power University | Zhang J.,North China Electrical Power University | Gui X.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

To improve scheduling flexibility of grid-connected Wind and PV power generation system, it is necessary for the system to apply energy storage technology, and the primary key technological problem to be researched is how to determine the capacity configuration of the energy storage system. Using complementary characteristics of the battery and the supercapacitor, an energy management strategy, in which the optimization of battery operating condition is taken as the principle and the improvement of overall economy of energy storage system as the objective, is proposed. Based on the proposed energy management storage, the energy loss rate of grid-connected wind and PV generation system and the calculation course of the rate are analyzed. According to the theory of life cycle cost, the expressions for annual average cost function of energy storage system is established; taking the minimization of this function value as the objective and the loss of produced power probability and the loss of power supply probability as constraints, an optimal configuration model for optimal configuration of the capacity of energy storage system is built. Case calculation is performed by use of improved chaotic optimization algorithm and the built optimization model, and calculation results show that the built optimal modes and the improved algorithm are correct and effective.


Luo Y.,North China Electrical Power University | Liu M.,North China Electrical Power University
Dianwang Jishu/Power System Technology | Year: 2013

To solve the troubles in microgrid dispatching caused by the randomness of wind power generation and PV generation, through utilizing the probability distribution function of renewable energy sources to describe the uncertainty factors existing in microgrid and leading in the risk indicator of load loss and the risk indicator of wind power curtailment and wasted solar energy a multi-objective model, in which the generation economy and environmental protection are considered, is established to ensure the reliability of microgrid power supply and efficient utilization of renewable energy sources. The improved multi-objective particle swarm optimization (MOPSO) algorithm is used to solve the proposed model, and then through the entropy weight based decision-making the final dispatching scheme is determined, thus the impact of subjective factor in artificially determining multi-objective weights can be avoided to make the overall benefits of microgrid dispatching optimal. Validity of the proposed model and algorithm is verified by calculation results.


Ji X.,North China Electrical Power University | Xu J.,North China Electrical Power University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2012

Experiments were performed to study pressure drops in copper foams embedded in a rectangular copper channel. De-ionized water was used as the working fluid with mass fluxes of 30-200 kg/m 2 s, and inlet temperature of 40-80°C. The copper foam has the porosity of 0.88 and the pore densities of 30, 60 and 90 ppi (pores per inch). Both single-phase liquid flow and boiling two-phase flow are studied. Effects of mass fluxes, vapor mass qualities, and average pore diameters of metallic foams are investigated. It is found that friction factors for the single-phase liquid flow are mainly dependent on the Reynolds number and the average pore diameter of metallic foams. The friction factors are decreased with increases in the Reynolds numbers, and will approach 0.22 at high Reynolds numbers. For the boiling two-phase flow, two-phase pressure drops are increased with increases in the outlet vapor mass qualities, mass fluxes, and ppi values. The two-phase multiplier is increased with increases in the outlet vapor mass qualities and mass fluxes, and it is decreased with increases in the Martinelli parameter and will attain a constant value depending on the mass fluxes. The larger the mass fluxes, the larger the constant value is. An experimental correlation considering the effects of vapor mass qualities, mass fluxes, and average pore diameters of metallic foams is recommended, showing good accuracy to predict the two-phase pressure drops in metallic foams. © Springer-Verlag 2011.


Ding P.,Shandong University | Sun D.L.,North China Electrical Power University
Numerical Heat Transfer, Part B: Fundamentals | Year: 2013

In this article, a novel finite-volume solver for the two-dimensional incompressible flow on unstructured grids is presented. The solver is formulated to operate on any type of control volumes. The performance of the new algorithm as compared to the SIMPLE algorithm is tested by solving three benchmark problems using both methodologies and comparing their computational costs. Results indicate that the new algorithm can reach convergence in a more wide parameter range and it is at least two times faster than the SIMPLE algorithm. The advantage of the new algorithm is especially evident for the case of high Reynolds number. © 2013 Copyright Taylor and Francis Group, LLC.


Shi F.,North China Electrical Power University
MATEC Web of Conferences | Year: 2016

The development of the phasor measurement units (PMUs) and the wide-area measurement systems (WAMS) in power system provide abundant synchronous data for the new application. This paper proposes an online out-of-step monitoring and predicting scheme for the interconnected power systems based on the rotor angle measurement. The Prony algorithm is improved to predict whether and when a power swing will lead to out-of-step of the generator or the power systems. An energy-like weight coefficient approximation of the decomposed signals is introduced to maintain the accuracy and reliability of the model free dynamic prediction method. The effectiveness and applicability of the proposed scheme is illustrated using a 2-area-4-machine power system. © The Authors, published by EDP Sciences, 2016.


Zhang Z.-H.,North China Electrical Power University | Qiao Y.-L.,North China Electrical Power University
Gongcheng Lixue/Engineering Mechanics | Year: 2011

This paper analyzes the mechanism of TBM rock breaking and provides the basic principle of disc cutter layout. The normal force, circumferential force, side force and inertia force probed are discussed and their corresponding mechanics formulas are presented. A balancing theory of forces acting on cutter head of TBM during rock breaking is put forward and a mathematical mechanical model of disc cutter layout is set up. A typical case with some imported TBM justifies the correctness of the mathematical mechanical model and its solution. Therefore an applicable approach to the layout of TBM disc cutter is developed.


Wu Q.-L.,North China Electrical Power University | Lu A.-Z.,North China Electrical Power University
Gongcheng Lixue/Engineering Mechanics | Year: 2011

The stress analytical solution for plane problem of a thick-walled cylinder subjected to a type of non-uniform distributed pressures is given by the complex variable function method. The results show that tangential stresses and/or radial stresses change into tensile stresses from compressive stresses with the increase of non-uniform lateral pressure coefficient. And the value of tangential tensile stress is much larger than that of radial tensile stress. On the premise of non-existence of tensile stress zones, the range of non-uniform lateral pressure coefficients is back-calculated and the tensile stress zones corresponding to different non-uniform lateral pressure coefficients are given. Theoretical analysis results are verified by numerical method.


Zhang S.,North China Electrical Power University | Wang T.,North China Electrical Power University | Zhao B.,North China Electrical Power University
Journal of Hydrology | Year: 2014

Simulations of flood inundation have important practical significance for flood control and disaster alleviation. Accuracy and efficiency are two major indicators in evaluating the performance of flood inundation models. Although a flood inundation model based on hydrodynamics can use detailed topographic data to accurately evaluate flood inundation processes, it is difficult to build a reasonable model for complex topography and variable flood conditions. More importantly, the simulation time for these types of models is generally too long and cannot be accomplished in real time. This paper proposes a new method, named the flood-connected domain calculation (FCDC) method, to improve the efficiency of flood inundation models in regions of complex topography. The main concept of the method is that inundation can only occur in areas where the water level is higher than the terrain elevation and connected with the river; this requires the key development of an algorithm to search for connected domains. The FCDC method uses a topographic triangle network to define the DEM source data and topological relationships are constructed to undertake the flood-connected domain search. Two cases from the Songhua River in Harbin City, China have been examined to expand the usage and effect of the method. The results show that the FCDC method can simulate source flooding such as inundation by river flooding or dike breach flooding and can characterize inundation under a range of conditions. Also, it can use a range of resolutions for topographic data and water level as model input, which in turn significantly reduces simulation time while providing reasonable simulation results. In addition, the FCDC method can be used to obtain a smooth display effect for flood inundation processes. Overall, the FCDC method is useful for estimating flood inundation and preparing for emergencies because of its time-efficient performance and low input and hardware requirements. © 2013 Elsevier B.V.


Jia J.,North China Electrical Power University | Liu J.,North China Electrical Power University | Zhang Y.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

This paper deduced a mathematical model for the doubly-fed induction generator (DFIG) in positive and negative synchronous reference frames under balanced and unbalanced grid voltages. The dynamic characteristics of the DFIG were analyzed and the complete dynamic-analytical expressions of the DFIG stator flux under balanced and unbalanced voltage fault conditions were provided. The paper proposed that the stator flux can oscillate with the line frequency when balanced grid fault occurs; and with twice the grid frequency under the unbalanced grid voltage conditions. Through two voltage-fault simulations with the duration of 50 ms and 100 ms respectively, this paper proposed that under the unsymmetrical grid voltage fault condition, when the grid voltage returns, the amplitude of the flux oscillations can vary from zero up to twice the amplitude at the start of voltage sag. Simulations with various typical voltage faults were presented. The results validated the correctness of the theoretical analysis. © 2011 Chin. Soc. for Elec. Eng.


Mu G.,Northeast Dianli University | Cui Y.,North China Electrical Power University | Yan G.,Northeast Dianli University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

As some wind energy enriched regions are away from load centers, especially in the North China, it is necessary to connect clustering wind farms into the main grid with high-voltage transmission lines. So the primary issue is to rationally determine transmission capacity of the transmission line. This paper presented a static optimization method for transmission capacity determination considering the low energy density characteristics of wind generation. In order to maximize the comprehensive benefits of the transmission project, the following factors have been taken into account such as the transmission benefit, transmission constructing costs as well as the congestion loss probably caused by a low transmission capacity. Example shows that the proposed method can achieve optimal transmission project benefit than the traditional one based on the total installed capacity. Meanwhile, the proposed method is an effective tool to determine transmission capacity for incorporating some 10 GW-class wind farms into main grid. © 2011 Chin. Soc. for Elec. Eng.


Wang W.,North China Electrical Power University | Han Z.-L.,Nankai University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this paper we propose a radiated linear seesaw model where the naturally small term μL is generated at the one-loop level and its soft breaking of lepton number symmetry contributes to the spontaneous breaking (SSB) of B-L gauge symmetry. The value of B-L charges for new particles are assigned to satisfy the cancellation of anomalies. It is found that some new particles may have exotic values of B-L charge such that there exists residual Z2×Z2′ symmetry even after SSB of B-L gauge symmetry. The Z2×Z2′ discrete symmetry stabilizes these particles as dark matter candidates. In the model, two classes of inert fermions and scalars with different B-L charges are introduced, leading to two-component dark matter candidates. The lepton-flavor-violation processes, the relic density of dark matter, the direct detection of dark matter and the phenomenology at the LHC are investigated. © 2015 American Physical Society.


Li W.,North China Electrical Power University | Jia Z.,North China Electrical Power University
Applied Energy | Year: 2016

To cope with global warming, China has promulgated Enhanced actions on climate change: China's intended nationally determined contributions and will start the national carbon emissions trading market in 2017. Carbon emissions are distributed by the form of free quota and paid quota. However, few literatures have focused on how the economy and the environment would be changed by the change of free quota ratio. This paper establishes the 10 scenarios of different free quota ratio of carbon emissions rights and uses a dynamic, recursive computable general equilibrium (CGE) model to simulate the carbon emissions trading market, to explore the relationship between free quota ratio and carbon trading price, and the impact of carbon trading scheme (ETS) on China's economy and environment. The results show that free quota ratio will not have a direct impact on gross domestic product (GDP) and other economic and environment indicators but carbon trading prices. The prices and the rate of free payment in the current pilot cities in China are still relatively conservative. It is possible to reach emission peak, 8.21 billion ton, in 2025 and accumulative CO2 reduction from 2017 to 2030 is 20.02 billion tons, or 59.60% of 2010 world's total CO2 emission. Cement, minerals, electricity and nonferrous metals under ETS will suffer great losses, so subsidy should be considered. Finally, we suggested that China should reduce the total carbon rights to increase the carbon price in 2017, and gradually reducing the proportion of free quota, from 90% in 2017 to 50% or less in 2030, by which the peak year of CO2 emission can meet in 2025. We also suggest that ETS is an effective strategy for CO2 reduction and the ratio should be gradually reduced in ETS to prevent violent fluctuation of carbon price in China. © 2016 Elsevier Ltd.


Chao Z.,North China Electrical Power University
International Journal of Acoustics and Vibrations | Year: 2016

Signals collected from dual-channel sensors contain abundant fault characteristic information when the rub-impact fault occurs in a rotor system. As a combination of bispectrum and vector-spectrum analisys, vector-bispectrum analysis can achieve an effective elimination of Gaussian noise and accurate analysis on quadratic phase coupling in signals by combining dual-channel information. However, it has been found in the slight rubbing experiment that part of the fault information is lost by simply using the bispectrum or vector-bispectrum method. In order to resolve this problem, a new fault feature extraction approach for the rubbing rotor based on the energy index of vector-bispectrum is proposed and used in the experimental test to obtain typical characteristics of the full annular rub-impact fault. It is shown that this novel method of feature extraction inherits the advantages of vector-spectrum analysis. The features of the rub-impact fault based on the energy index of vector-bispectrum has been extracted successfully, and the result of classification through SVM illustrates that the extracted features are very noticeable, and the proposed method can comprehensively reflect nonlinear information of the rubbing rotor.


Xu Z.N.,North China Electrical Power University | Wang S.Y.,North China Electrical Power University
Review of Scientific Instruments | Year: 2015

To improve the accuracy in the calculation of dynamic contact angle for drops on the inclined surface, a significant number of numerical drop profiles on the inclined surface with different inclination angles, drop volumes, and contact angles are generated based on the finite difference method, a least-squares ellipse-fitting algorithm is used to calculate the dynamic contact angle. The influences of the above three factors are systematically investigated. The results reveal that the dynamic contact angle errors, including the errors of the left and right contact angles, evaluated by the ellipse-fitting algorithm tend to increase with inclination angle/drop volume/contact angle. If the drop volume and the solid substrate are fixed, the errors of the left and right contact angles increase with inclination angle. After performing a tremendous amount of computation, the critical dimensionless drop volumes corresponding to the critical contact angle error are obtained. Based on the values of the critical volumes, a highly accurate dynamic contact angle algorithm is proposed and fully validated. Within nearly the whole hydrophobicity range, it can decrease the dynamic contact angle error in the inclined plane method to less than a certain value even for different types of liquids. © 2015 AIP Publishing LLC.


Zhang S.,North China Electrical Power University | Pan B.,Changjiang River Scientific Research Institute
Journal of Hydrology | Year: 2014

With the increase of urbanization, conditions of the underlying surface and climate have been changed by human activities. This results in more frequent flooding and inundation problems in urban areas. Storm-inundation models based on hydrology and hydrodynamics require a large amount of input data (detailed terrain, sewer system and land use data). Simulation models are complex and difficult to build and run. To determine inundation conditions quickly with only a few commonly available input data, an urban storm-inundation simulation method (USISM) based on geographic information systems (GIS) is proposed in this paper. The method is a kind of simplified distributed hydrologic model based on DEM, in this method, depressions in the terrain are regarded as the basic inundated area. The amount of water that can be stored in a depression indicates the final inundation distribution. The runoff catchment area and maximum storage volume of a depression, and the flow direction between these depressions are all considered in the final inundation simulation. GIS technology is used to find the depressions in an area, divide the subcatchment for each depression, and obtain the flow order of the depressions based on a digital elevation model (DEM). The SCS method is used to calculate storm runoff, and a water balance equation is used to calculate water storage in each depression. Nangang District in Harbin City, China, is selected as the study area to verify the USISM. The result reveals that the USISM could find inundation locations in the urban area and quickly calculate inundation depth and area. The USISM is valuable for simulating storms of short duration in an urban area with a few commonly available input data. © 2014 Elsevier B.V.