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991.
This paper presents a position sensorless drive of salient‐pole PM synchronous motors in all speed ranges including zero speed. Two position and speed estimation algorithms using the current differences between the actual and the estimated currents are proposed. One is based on the back emf estimation in the medium‐ and high‐speed ranges. Another is based on the position dependency of the winding inductances in the low‐speed ranges including zero speed. The effectiveness of the proposed algorithm has been verified with a six‐pole, 1.5‐kW, 1500‐rpm test motor. Stable sensorless speed control from zero to 3000 rpm within ±100% load torque range was achieved. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 64–73, 2001 相似文献
992.
Akira Urano Ken Syoji Taiki Sato Hidemitsu Koyanagi Masayuki Oguro Yasushige Morikawa 《Building Simulation》2014,7(2):123-129
We have developed a simulation system for a year-round assessment of environmental comfort, energy conservation, and CO2 emissions in buildings and street blocks where active utilization of sunshine, vegetation and solar energy resources is fully considered. An analysis model has been constructed for handling interactions between highly complex street-block wide solar radiation patterns and building air-conditioning load. As a demonstration case of the present system, coupled solar radiation-thermal load analysis for an eleven-story office building has been performed. By comparing the result of a building located in a city block with a reference case of a self-standing building, the proper arrangement of buildings and spaces such as solar reflectance of building surface may be proposed. 相似文献
993.
Laminated carbon fiber reinforced polymer (CFRP) composites have widespread applications in aerospace structures, and thus optimization of the stacking sequences in these composites is indispensable. Here, a fractal branch and bound method (FBB) is proposed for optimizing the stacking sequences. This method requires only low computational costs, and an optimal result can be obtained rapidly by means of the deterministic process. For practical stacking sequence optimizations, more than two laminates have to be optimized, because a practical aerospace structural component usually comprises a panel and stiffeners made from composite laminates. Since the stacking sequences of the skin panel and stiffeners affect the buckling load of the stiffened panel, the optimization of both laminates must be performed simultaneously. In the present study, a new method to implement a strength constraint for the FBB method is proposed for the simultaneous optimization of more than two laminates (such as a panel and stiffeners). Moreover, a quadratic polynomial objective function, which includes lamination parameter variables of the two laminates: the stiffeners and the panel, is adopted. The strength constraint is implemented by means of a response surface. The new method is applied to the buckling load maximization of a blade-stiffened composite panel, in which the strength constraint is demonstrated as a feasibility study. The method successfully obtained optimal stacking sequences with the strength constraint at low computational cost. 相似文献
994.
Kenji Takizawa Akifumi Takahashi Kazuaki Tokuhashi Shigeo Kondo Akira Sekiya 《Combustion and Flame》2005,141(3):298-307
Burning velocity has been measured using the spherical-vessel (SV) method for four hydrofluorocarbons (HFCs), i.e., difluoromethane (HFC-32), 1,1,2-trifluoroethane (HFC-143), 1,1,1-trifluoroethane (HFC-143a), and 1,1-difluoroethane (HFC-152a). Experiments were conducted for initial pressures in the range 78-108 kPa and initial temperatures in the range 280-330 K, over wide ranges of HFC-air equivalence ratios. The burning velocities were determined from the rate of pressure increase by applying a spherical-flame propagation model. Flame propagation behavior was observed in a cylindrical vessel equipped with optical windows by employing schlieren photography. It was found that the values of burning velocity derived from the spherical-vessel method are in good agreement with the ones obtained with schlieren method. It is found that the SV method is adequate for determining the burning velocity for weakly flammable HFCs as well as for moderately flammable compounds. The burning velocity of each HFC was obtained as a function of temperature, pressure, and equivalence ratio. The maximum burning velocities of HFC-32, HFC-143, HFC-143a, and HFC-152a were determined to be 6.7, 13.1, 7.1, and 23.6 cm s−1, respectively. The maximum burning velocity occurred for slightly fuel-rich concentrations. The magnitude of the burning velocity is strongly dependent on the ratio of H atoms to F atoms in the HFC molecules. 相似文献
995.
We present a novel filtering method for reconstructing an all-in-focus image or an arbitrarily focused image from two images that are focused differently. The method can arbitrarily manipulate the degree of blur of the objects using linear filters without segmentation. The filters are uniquely determined from a linear imaging model in the Fourier domain. An effective and accurate blur estimation method is developed. The simulation results show that the accuracy and computational time of the proposed method are improved compared with the previous iterative method and that the effects of blur estimation error on the quality of the reconstructed image are very small. The method performs well for real images acquired without visible artifacts. 相似文献
996.
Shima Sabbaghianrad Megumi Kawasaki Terence G. Langdon 《Journal of Materials Science》2012,47(22):7789-7795
Processing by high-pressure torsion (HPT) was performed on disks of an Al-7075 alloy at room temperature. The alloy was initially annealed at 753 K and then processed by HPT under a pressure of 6.0 GPa up to a maximum of ten turns. Measurements of the Vickers microhardness showed lower values at the centers of the disks after small numbers of turns but higher numbers of turns led to a reasonable hardness homogeneity across each disk. After five turns, the grain size at the edge of the disk was ~250 nm. It is demonstrated that results from mechanical testing are consistent with the hardness and microstructural data. 相似文献
997.
Characterization of simple and reproducible vascular stenosis model in hypercholesterolemic hamsters
Hiroyuki Matsuno Osamu Kozawa Masayuki Niwa Akira Abe Yoshiharu Takiguchi Toshihiko Uematsu 《Lipids》2001,36(5):453-460
The importance of low-density lipoprotein (LDL) in the etiology of atherosclerosis is well recognized. We have established
a reproducible stenosis model in hypercholesterolemic hamsters, and the process of arterial stenosis by thrombus or neointima
was studied and compared with that in normal hamsters. The level of plasma LDL was 4.6 times higher in hamsters fed a high-cholesterol
diet than in hamsters fed normal food. Endothelial injury in right common carotid arteries was induced using a modified catheter.
Arterial blood flow was monitored continuously using a Doppler flow probe. Arterial patency after the initiation of injury
in high-cholesterol hamsters was significantly changed as compared with that of normal hamsters. Neointima was observed 2
wk after the vascular injury. The neointimal area of high-cholesterol hamsters was significantly larger than that of normal
hamsters. To characterize the stenosis in hypercholesterolemic hamsters, we measured platelet aggregation, thrombin time,
activated partial thromboplastin time, and proliferating smooth muscle cells (SMC) in vitro and in vivo. The half-maximal inhibitory concentration value for platelet aggregation induced by thrombin or collagen, the DNA synthesis
stimulated by plateletderived growth factor (PDGF)-BB, and 5-bromo-2-deoxy-uridine labeling indices (proliferating index of
SMC in vivo) in high-cholesterol hamsters were each significantly higher than the comparable value from normal hamsters. However, specific
binding of PDGF-BB in SMC was not different between the two types of hamsters. Furthermore, we investigated the inhibitory
effects of probucol or losartan on neointima formation using this model. Probucol, but not losartan, significantly reduced
the neointimal area in hypercholesterolemic hamsters. These findings indicated that high levels of plasma LDL strongly contributed
to the development of thrombus and neointima formation via both up-regulation of platelet aggregation and the enhancement of SMC proliferation. This stenosis model may be useful for
the investigation of hypercholesterolemia-associated cardiovascular diseases. 相似文献
998.
The thermal formation of dioxins is typical of recent environmental issues relating to metallurgy. To analyze the behavior
of these toxic species, computer assisted thermodynamic assessments were extensively carried out. In the homogeneous gas phase
equilibria of the C−O−H−Cl system, the formation of dioxins is usually observed below 300–350°C, but is observed at higher
temperature under the condition of oxygen deficiency. It has become clear that the presence of enough oxygen and hydrogen,
as well as a decrease in chlorine content, would be desirable to prevent dioxin formation. From a strict thermodynamic standpoint,
dioxins are meta-stable products observed under the retardation of the carbon deposition reaction which must be very slow
at low temperature. The effects of some inhibitors or accelerators on the formation of dioxins are also discussed.
This article based on a presentation made in the symposium “2000 Spring Meeting of the Korean Institute of Metals and Materials”,
held at Sunchon National University, Sunchon, Korea, April 21–22 under the auspices of The Korean Institute of Metals and
Materials. 相似文献
999.
Katsumi Yamazaki Shunji Ohki Akira Nezu Takeshi Ikemi 《Electrical Engineering in Japan》2009,168(3):59-66
In this paper, we present the development of interior magnet motors reducing iron loss at high rotational speed under the flux weakening control. The rotor core and magnet shapes are determined by the automatic numerical calculation using combination of the optimization method and the adaptive finite element method. The optimized motor is manufactured to prove the effectiveness by the measurement of the iron loss. Both results of the calculation and the measurement indicate that the iron loss of the proposed motor at the high rotational speed under the flux weakening control is reduced by half compared with the initial rotor shape while the torque is nearly constant. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 59–66, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20827 相似文献
1000.
Lithium iron phosphate (LiFePO4) powders were prepared by hydrothermal reactions under a nitrogen atmosphere or an air atmosphere, and the microstructure and electrochemical properties of the LiFePO4 powders were investigated. The LiFePO4 powder prepared under the nitrogen atmosphere (LiFePO4–N2) had a small particle size in the range of 300–500 nm, whereas the powder prepared under the air atmosphere (LiFePO4?air) had a large particle size in the range of 1–5 μm. Although the Fe2+/Fe3+ ratio was not significantly different in both LiFePO4 powders, the Fe2+/Fe3+ ratio in the precursor suspension prepared under the nitrogen atmosphere was much higher than that prepared under the air atmosphere, thereby resulting in the small particle size of the LiFePO4–N2 powder. The discharge capacity of a LiFePO4–N2 electrode was 149 mAh g?1 at a low current density of 10 mA g?1, whereas that of a LiFePO4?air electrode was 83 mAh g?1. Impedance analyses indicated that the charge transfer resistances normalized to the surface area of LiFePO4 particles for the LiFePO4–N2 and LiFePO4?air electrodes were 4.6 and 4.8 Ω m2, respectively. These values were not significantly different. This revealed that the factor dominating the electrochemical properties of LiFePO4–N2 and LiFePO4?air powders was particle size and not crystalline lattice or Fe2+ concentration. 相似文献