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排序方式: 共有876条查询结果,搜索用时 10 毫秒
71.
Yotaro Akamine Shigeyasu Matsuoka Masakuni Chiba Kunihiko Hidaka 《Electrical Engineering in Japan》2000,132(4):28-33
The breakdown voltages of the longer‐gap configurations in gaseous nitrogen and air that are necessary in designing superconducting electrical power apparatuses are measured at temperatures of 293 and 93 K. The quasi‐uniform electric field made by a sphere‐to‐sphere electrode with a diameter of 150 mm and a gap length of about 10 to 100 mm is used in the measurement of the breakdown voltages. When 50‐Hz ac and dc voltages are applied to the sphere‐to‐sphere gap, the breakdown voltages in nitrogen and air obey Paschen's law even at cryogenic temperatures (93 K). When a 1.4/50‐μs lightning impulse voltage is applied to the gap, the 50% breakdown voltage of nitrogen also obeys Paschen's law under UV irradiation of the cathode electrode. However, the breakdown voltage in air at 93 K is higher in the case of lightning impulse voltage applications, and the delay from impulse voltage application to breakdown occurrence is apparently longer at 93 K than at 293 K. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 28–33, 2000 相似文献
72.
Saburo Matsuoka Hiroyuki Masuda Masuo Shimodaira 《Metallurgical and Materials Transactions A》1990,21(8):2189-2199
The fatigue threshold and low-rate crack propagation properties for a carbon steel, two high-strength steels, and two stainless
steels were investigated in a 3 pct sodium chloride aqueous solution at frequencies between 0.03 and 30 Hz. Tests were conducted
in a manner designed to avoid crack closure. Under freely corroding conditions, the effective values of the threshold stress
intensity factor range, ΔKth,eff, were lower than in air for all of the steels. In particular, the ΔKth,eff values for the carbon and high-strength steels were almost equal to the theoretical ΔKth value of about 1 MPa m1/2 calculated on the basis of the dislocation emission from the crack tip. At a given ΔK level higher than the threshold, the
fatigue crack propagation rates accelerated with decreasing frequency for all of the steels. Under cathodic protection, the
threshold and fatigue crack propagation properties were coincident with those in air regardless of material and frequency.
The observed fatigue crack propagation behavior in a 3 pct NaCl solution was closely related to the corrosion reaction of
the bare surface formed at the crack tip during each loading cycle. 相似文献
73.
Kensuke Miyahara Saburo Matsuoka Tohru Hayashi 《Metallurgical and Materials Transactions A》2001,32(3):761-768
A nanoindentation hardness testing system, including an atomic-force microscope (AFM)-based nanoindentation tester and a calibration
method using electrolytically polished single-crystal metals as references, was proposed. This was applied to a study of the
mechanical properties of fine-grained ferritic steel (grain size of 1.2 μm) and coarse-grained ferritic steel (30 μm). An
empirical function giving the macroscopic hardness for all four reference metals from the nanoindentation force curves was
established. The converted Vickers hardness (HV*) of the coarse-grained steel is almost independent of the indent size. The
fine-grained steel shows only HV* 130 with an indent of only 100 nm, compared with a macroscopic hardness of HV 210. The difference,
HV 80, is considered to reflect the amount of grain-boundary strengthening. The critical indent size for the hardness transition
seems to be around 1 μm, comparable to the grain size of the specimen. This result supports the explanation of grainboundary
strengthening. It is also consistent with Pickering’s work on low-carbon steel, as the estimated locking parameter (k of 2.6×105 N/m3/2) in the Hall-Petch relationship is in good agreement with his value of 2.4×105 N/m3/2. 相似文献
74.
For some adhesive joints where the main difference is the degree of contact at the interface, failure occurs not at the interface, but some distance away in the polymer itself. This cohesive mode of failure in the polymer was always found to be the case in our studies of cupric oxide to branched polyethylene interfaces, even where the joint was so weak that the peeled surface seemed clean of the polymer to the naked eye. It was observed that the strength of the joint was associated with the coarseness of the texture of the peeled surface of the polymer. With a differential scanning calorimetry technique we have shown that the coarseness of the surface texture and therefore the strength of the joint, is a direct function of the amount of polymer involved in plastic deformation. The strength criteria for the adhesive joint of this kind is thus the energy of deformation and not the maximum tensile stress that the material can withstand. 相似文献
75.
Nishimura S. Inoue H. Matsuoka H. Yokota T. 《IEEE journal of selected topics in quantum electronics》1999,5(2):360-367
Optical interconnection between the nodes of the RWC-1 massively parallel computer has been implemented. A one-node testbed system and an eight-node parallel processing system have been produced to demonstrate large-throughput small-skew low-latency and highly reliable optical internode connection. Each node was interconnected through dc-coupled 24-bit synchronized parallel optical interconnection at 100 MHz using 50-m-long single-mode ribboned fibers. The skew in a 24-bit data signal was suppressed to within 650 to -380 ps, and the OE/EO conversion delay time was 15.2 ns. We ran a parallel-processing program on the eight-node system as an evaluation, and the 50-m-long optically interconnected system performed as well as a 10-m-long electrically interconnected system. This clearly shows that optical interconnection will overcome the communication bottleneck in multinode computer systems 相似文献
76.
77.
This paper covers some examples of the STRI and NGK experience with the standard IEC 1109 salt fog test and some modifications of this test for different types of test objects 相似文献
78.
This paper presents a computer program for fault tree analysis. The algorithm is a bottom-up algorithm and the detailed procedure of the program is explained. The analyses are performed for six sample fault trees and the results are compared with those obtained by the BAM and CUT codes. This program has a ten to thousand times faster calculation speed compared with the BAM and CUT codes. 相似文献
79.
Zhanpeng Lu Tetsuo Shoji Yoichi Takeda Yuzuru Ito Akira Kai Seiya Yamazaki 《Corrosion Science》2008,50(2):561-575
The stress corrosion cracking (SCC) growth kinetics for a cold worked 316L stainless steel was continuously monitored in high purity water at different temperatures and dissolved oxygen (DO) levels under a K (or Kmax) of 30 MPa m0.5. The total SCC test time was more than 8000 h to make sure the steady state crack growth rate under each test condition could be reached. Crack growth rate (CGR) increases with increasing temperature in the range 110-288 °C. A typical intergranular-cracking mode is identified. Depending on the previous test condition, especially the temperature, three kinds of crack growth kinetics, i.e., increasing with testing time then becoming steady, being constant during the whole period, or decreasing with test time then becoming steady, are identified and discussed. Time-dependent and testing history-dependent crack growth modes were confirmed in two series of tests in 2 ppm DO and 7.5 ppm DO pure water. The apparent activation energies are calculated and compared with other data in different environments under different applied loading levels for understanding the cracking mechanism. 相似文献
80.