- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 Chinese Automation Congress (CAC) - Hangzhou, China (2019.11.22-2019.11.24)] 2019 Chinese Automation Congress (CAC) - A New Method for Multiple Open-Transistor Fault Diagnosis in Photovoltaic micro-grid inverter by disposing the output current
摘要： If there is no reactive power exchange between a doubly fed induction generator (DFIG) and a grid, the various characteristics of the power converters in a DFIG wind turbine system cause the lifetime expectancy of a rotor-side converter (RSC) to be significantly less than that of a grid-side converter (GSC). In order to fulfill modern grid codes, over-excited reactive power injection will further reduce the lifetime of the RSC. In this paper, the additional stress of a power semiconductor due to the reactive power injection is first evaluated in terms of a modulation index and the current loading. Then, an optimized reactive power flow is proposed in the case where an over-excited reactive power support is applied with the joint compensation from both the RSC and the GSC. Finally, some experimental validations are performed at a downscale DFIG prototype. It is concluded that, among the different combined reactive power support strategies, the best scheme will tradeoff the lifetime between the GSC and the RSC.
关键词： thermal behavior,Consumed lifetime,reactive power,doubly fed induction generator (DFIG)
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Optical Parametric Oscillator Based Differential Absorption Lidar for Tropospheric Methane Concentration Measurement
摘要： If there is no reactive power exchange between a doubly fed induction generator (DFIG) and a grid, the various characteristics of the power converters in a DFIG wind turbine system cause the lifetime expectancy of a rotor-side converter (RSC) to be significantly less than that of a grid-side converter (GSC). In order to fulfill modern grid codes, over-excited reactive power injection will further reduce the lifetime of the RSC. In this paper, the additional stress of a power semiconductor due to the reactive power injection is first evaluated in terms of a modulation index and the current loading. Then, an optimized reactive power flow is proposed in the case where an over-excited reactive power support is applied with the joint compensation from both the RSC and the GSC. Finally, some experimental validations are performed at a downscale DFIG prototype. It is concluded that, among the different combined reactive power support strategies, the best scheme will tradeoff the lifetime between the GSC and the RSC.
关键词： thermal behavior,Consumed lifetime,reactive power,doubly fed induction generator (DFIG)
更新于2025-09-19 17:13:59
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Modeling of thermal behavior and microstructure evolution during laser cladding of AlSi10Mg alloys
摘要： An improved three-dimensional finite element model has been proposed for studying the thermal behavior and microstructure evolution during laser cladding of AlSi10Mg alloys. Different material properties between AlSi10Mg powders and AlSi10Mg alloys are distinguished from the experiment and theoretical calculation to provide more reliable material parameters for simulation. In order to investigate the melting and solidification process during the formation of cladding layers, a temperature selection judgment mechanism is established to simulate the evolution of AlSi10Mg powders from the powder state to melting state and alloy state. In addition, to simulate the complex thermal behavior associated with powder particles and the voids between particles, a simplified exponential attenuation model is used for correcting the heat source. A complex asymmetric heat source considering about the different material properties and laser absorptivity on both sides of the remelting zone is used for multi-track cladding process. By simulating the temperature distribution of molten pool, the improved FEM could be used to predict the geometric shape of cladding layers (ignoring the effect of melting flow) and the temperature history. The simulation results show that the heat tends to diffuse to the unmelted powder owing to the asymmetric heat source during multi-track cladding, which leads to the asymmetry of cladding layers along the width direction. Based on the results of the temperature field simulations and the solidification characteristics of AlSi10Mg powders, the temperature gradient (G), solidification growth rate (R), cooling rate (G*R) and G/R are investigated to predict the morphology and size of the solidification microstructure under different laser scanning parameters. The scanning speed mainly determines the cooling rate during the laser cladding process, which results in different microstructures. Higher scanning speed leads to higher cooling rate, corresponding to a finer microstructure. Coarse dendrites are generated at the bottom of the molten pool, while finer dendrites are formed at the top.
关键词： Simulation,Microstructure evolution,AlSi10Mg alloy,Laser cladding,Thermal behavior
更新于2025-09-16 10:30:52
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Thermal Behavior During the Selective Laser Melting Process of Ti-6Al-4V Powder in the Point Exposure Scan Pattern
摘要： Currently, there are two main scan patterns, including the continuous exposure scan pattern and the point exposure scan pattern, during the selective laser melting (SLM) process. The point exposure scan pattern allows a three-dimensional (3-D) printer to build ?ner detail features as a static molten pool that is more stable than a dynamic one. However, there has been limited theoretical research on the thermal behavior characteristics during the process in the point exposure scan pattern. Therefore, in this study, the simulation of thermal behavior during SLM of Ti-6Al-4V powder in the point exposure scan pattern was performed. The temperature evolution behavior of di?erent positions and the e?ects of exposure time on the temperature evolution behavior of di?erent positions, temperature distributions, and dimensions of the molten pool were investigated. The results showed that the direct exposure position and unexposed position had signi?cantly di?erent temperature evolution behaviors under a given condition, and the changed exposure time had the greatest in?uence on the direct exposure position compared with unexposed position. Moreover, the thermal accumulation e?ect of a former exposure point on a later one decreased with increasing exposure time. In addition, with the increase of exposure time, the maximum temperature of the molten pool was enhanced and the surface morphology of the molten pool changed from an approximate ellipse to an approximate circle. Besides, the molten pool dimensions were found to increase with exposure time, which indicated that the exposure time played an important role in the stability of the molten pool and the metallurgical bonding in the process. Furthermore, the dimensions of the molten pool and metallurgical bonding in the cross-sectional view were obtained through experiments. Good agreement was obtained when comparing the simulated results with the experimental ones.
关键词： Point exposure scan pattern,Selective laser melting,Ti-6Al-4V,Exposure time,Thermal behavior
更新于2025-09-11 14:15:04
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Raman spectra in LiH <sub/>2</sub> PO <sub/>4</sub> and KLi(H <sub/>2</sub> PO <sub/>4</sub> ) <sub/>2</sub> : Mode assignment
摘要： We report and analyze Raman spectra recorded on crystals of LiH2PO4 (LDP) and KLi(H2PO4)2 (KLDP). We provide a new and complete assignment of Raman lines in both crystals from their behavior as function of temperature. Among internal vibrations, we discern the modes within PO4 tetrahedra, the modes related to Li―O bonds, and those due to the O―H vibrations. In the wavenumber range between 300 and 600 cm?1, the lines associated with O―P―O or Li―O show different temperature dependencies. The bands of PO4 are red‐shifted with increasing temperature according to thermal dilatation, whereas the positions related to Li―O are temperature independent.
关键词： vibrational modes,phosphate compounds,crystal,thermal behavior,mode assignment
更新于2025-09-10 09:29:36
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Reference Module in Earth Systems and Environmental Sciences || Solar Energy in Buildings☆
摘要： Solar Energy can be utilized in many ways (e.g., photovoltaics, solar–thermal–electrical systems, solar ponds, and biomass conversion), but in the current chapter only applications associated with covering the heating and cooling requirements of buildings will be discussed. These applications require low or medium -temperature heat and include water heating, either for domestic hot water systems or swimming pools, space heating, and possibly also space cooling.
关键词： Net Zero Energy Buildings,Economics,Passive Systems,Design Methods,Thermal Behavior of Buildings,Buildings,Solar Energy,Solar Collectors,Space Heating and Cooling Systems,Hot Water Systems
更新于2025-09-09 09:28:46
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Nickel(II) Coordination Complex Constructed from Benzimidazole and Pyridine-2,6-dicarboxylate Co-ligands: Synthesis, Crystal Structure, Thermal Behavior, and Photoluminescence
摘要： A Ni(II) complex, [Ni(pydca)(bim)3] (pydca = pyridine-2,6-dicarboxylate, bim = benzimidazole) has been prepared by hydrothermal synthesis. It is characterized by elemental analysis, IR and thermal analysis. The crystal structure is determined by single crystal X-ray diffraction. The mononuclear complexes are linked by N–H···O hydrogen bonds. The title complex has good thermal stability and exhibits good fluorescence properties in ethanol solution at room temperature.
关键词： crystal structure,Nickel(II) complex,6-dicarboxylate,hydrothermal synthesis,benzimidazole,photoluminescence,thermal behavior,pyridine-2
更新于2025-09-04 15:30:14