The first non-parallel operating AC/DC system with series capacitor being constructed in China is hybrid of the Hulunbeier-Liaoning ±500kV HVDC lines and Yimin-Fengtun 500kV AC transmission system. Its subsynchro...
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作者:
Dehui XuLi ZhaoGang LiLinyan SunSchool of Management
The State Key Laboratory on Mechanic Manufacturing System Engineering The Key Laboratory of the Ministry of Education on Process Control and Efficiency Engineering Xi''an Jiaotong University Xi'an China
Supply chain integration nowadays is considered as an important approach to building and sustaining advantages. Many previous empirical researches focus on the effect of supply chain integration on the firms' perf...
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ISBN:
(纸本)9781424464852;9781424464876
Supply chain integration nowadays is considered as an important approach to building and sustaining advantages. Many previous empirical researches focus on the effect of supply chain integration on the firms' performance, yet, the antecedence of supply chain integration is still largely unknown. This paper investigates the relationship between environmental uncertainty (including demand uncertainty, supply uncertainty and technology uncertainty) and supply chain integration (including customer integration, supplier integration and internal integration) with 139 samples from Chinese manufacturing industry. The results reveal both supply uncertainty and technology uncertainty significantly influence supply chain integration; the effect of supply uncertainty is negative, while that of technology uncertainty is positive. However, demand uncertainty just has a significant effect on internal integration. The relationship between demand uncertainty and external integration (including customer integration and supplier integration) is mediated by the internal integration.
A new method of power quality synthetic evaluation based on relative intensity entropy and local variable weight is presented in the paper. This method firstly uses the relative intensity entropy theory to extract the...
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A wind turbine rotor system containing blades has its own characteristics. The vibration characteristics of blades with special airfoil can influence the vibration characteristics of the rotor system. This paper analy...
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A wind turbine rotor system containing blades has its own characteristics. The vibration characteristics of blades with special airfoil can influence the vibration characteristics of the rotor system. This paper analyzed the vibration characteristics of a wind turbine rotor including blades with two-dimensional airfoil. The Finite Element Method (FEM) is applied to establish the rotor model, with the purpose that the FEM can adjust complex blades airfoils and acquire the details of the blades vibration characteristics. The modal characteristics are extracted based on the wind turbine model established in the laboratory. Using harmonic analysis of FEM, the excitation forces on the blades caused by the stochastic wind load are imposed on the rotor model and the stable response of the rotor system is calculated using ANSYS. Then the vibration characteristics are analyzed and the characteristics of the harmonic response are studied under different phases of the circumferential and axial forces.
Photovoltaic application of LED lighting has been a hot trend in residential illumination, for it integrates the advantages of both the PV systems and LED lights. However, it has a series of problems, such as high the...
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Photovoltaic application of LED lighting has been a hot trend in residential illumination, for it integrates the advantages of both the PV systems and LED lights. However, it has a series of problems, such as high thermal loss, poor reliability, and a short life span. To address these problems, this paper presents a deep research on the whole system from a low-cost, high-efficiency and long-life point of view. A main circuit integrating maximum power point tracing (MPPT) control and battery management, as well as a double-loop control for LED load is developed. A set of protection system is applied to ensure high reliability of the system. The control strategies are tested on the demonstrator and prove to be effective.
This paper describes the effect of magnetic field on tracking failure of gamma-ray irradiated polybutylene naphthalate (PBN), polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). The experiment was c...
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This paper describes the effect of magnetic field on tracking failure of gamma-ray irradiated polybutylene naphthalate (PBN), polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). The experiment was carried out by applying a dc pulse voltage under magnetic field. The magnetic flux density (MFD) of the magnetic filed was 495 mT and the direction of E×B was 0, 90 and 270 degrees with respect to the sample surface. The PBN, PBT and PET were irradiated in air up to 100 kGy and then up to 1000 kGy with a dose rate of 10 kGy/h by using a 60 Co gamma-source. Obtained results revealed that the tracking failure was greatly changed by gamma-ray irradiation and magnetic field.
DC voltage control is critical for grid-connected inverters, as it contributes to reduce the DC capacitance and improve system reliability as well as MPPT performance. A predictive control scheme of DC voltage for sin...
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DC voltage control is critical for grid-connected inverters, as it contributes to reduce the DC capacitance and improve system reliability as well as MPPT performance. A predictive control scheme of DC voltage for single-stage three-phase grid-connected PV inverters is proposed based on the analysis of the energy balance relationship in one control period, while AC current is also regulated by predictive control. The proposed scheme provides both good dynamic and steady-state performance. The dynamic response is especially excellent. The DC voltage is adjusted as fast as possible with little overshoot.
The vibration signals of wind turbines are highly nonlinear and non-stationary due to wind turbine operation conditions that are very complicated. The signals will be more complex when a fault occurs. Aiming at these ...
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The vibration signals of wind turbines are highly nonlinear and non-stationary due to wind turbine operation conditions that are very complicated. The signals will be more complex when a fault occurs. Aiming at these problems, a fault diagnosis method for direct-drive wind turbine is presented based on back propagation neural network (BPNN). The time-domain feature parameters of vibration signals in the horizontal and vertical direction are considered in the method. Five experiments of direct-drive wind turbine with normal, wind wheel mass imbalance, wind wheel aerodynamic imbalance, yaw and blade break are carried out in laboratory scale. Through analyzing the features of five conditions, the time-domain feature parameters in horizontal and vertical direction of the vibration signal are selected as the input samples of BPNN. By training, the BPNN model can be constructed between feature parameters and fault types. The validity of the BPNN model is verified using test samples. The results indicate that the proposed method has higher diagnostic accuracy. It can used in on-line fault diagnosis of direct-drive wind turbines.
As an important component of a wind turbine drive chain, the high failure rate of the gearbox can have a serious impact on the operation of wind turbine units. The fault diagnosis of the gearbox is therefore important...
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As an important component of a wind turbine drive chain, the high failure rate of the gearbox can have a serious impact on the operation of wind turbine units. The fault diagnosis of the gearbox is therefore important for the safety of wind turbine units. In this paper, a gearbox experiment rig was built, experiments on the gear surface spalling fault were held on the rig under laboratory conditions, the shaft vibration displacement signals were collected, related vibration signals were analyzed by time domain, amplitude domain, frequency domain and wavelet analysis, and the results of different analysis methods were compared. The results show that the waveform of normal and fault signals are similar, the amplitude of the signals will change while the fault happens, and the wavelet analysis is more effective than frequency domain analysis on gearbox fault features extraction.
As the support structure of wind turbine, the tower bears alternating loads of wind when the wind turbine runs. To ensure the reliability of the wind turbine, it's necessary to carry out modal analysis on the towe...
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As the support structure of wind turbine, the tower bears alternating loads of wind when the wind turbine runs. To ensure the reliability of the wind turbine, it's necessary to carry out modal analysis on the tower, and this would prevent the natural frequency of the tower close to the rated speed of wind turbine. In this paper, finite element analysis of the tower is solved using ANSYS, and the natural frequencies and modes of the tower are presented. After comparing the results of three models, a simple model for modal analysis, which can be calculated in short time, is finally determined.
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