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41.
Boiler tubes in power plants have finite life because of prolonged exposure to high temperature, stress and aggressive environment. Service-exposed platen superheater and reheater tubes (148,900 h) made of 2.25Cr-1 Mo steels in a 120 MW boiler of a thermal power plant were evaluated for remnant life. The investigation included hot tensile tests, hardness measurement, dimensional measurement, microscopy and creep tests. Experimentally determined yield and ultimate tensile strength, and estimated 10,000–100,000 h rupture strength in the temperature range 520–580 °C, exhibited a decreasing trend with increasing temperature. Microstructural study did not reveal any significant degradation in terms of creep cavities, cracks, graphitization, etc. Analysis of tensile and stress rupture data revealed that although there was degradation of the tubes due to prolonged service exposure in terms of the ultimate tensile strength values, stress rupture plots showed that the service exposed superheater and reheater tubes could remain in service for a length of more than 10 years at the operating hoop stress of 40 MPa/540 °C, provided no localised damage in the form of cracks or dents develop. 相似文献
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A necessary and sufficient condition for the union of an arbitrary family of fuzzy subgroups of a group to be a fuzzy group has been proposed. The criterion which gives a cut of the unit interval is called the Schnittaxiom. It has been applied successfully to investigate fuzzy subgroupness of arbitrary unions of homomorphic images and preimages. 相似文献
44.
The basics of acoustic resonance spectroscopy (ARS), which provides data about an object's physical structure and composition, are explained. In ARS, one actively excites a large number of resonances (normal modes) in an object that has no internal vibrations by slowly sweeping the excitation frequency to obtain an acoustic spectrum of the object. The instrumentation for this nondestructive evaluation technique is described, and some applications are briefly discussed 相似文献
45.
Zaleski A. Sinha S.P. Ioannou D.E. Campisi G.J. Hughes H.L. 《Electron Devices, IEEE Transactions on》1995,42(9):1697-1700
By operating one channel of a typical SOI MOSFET in avalanche while keeping the opposite channel accumulated, charge injection into the opposite gate takes place. Three independent experiments are described that demonstrate the occurrence of this opposite-channel based charge injection. The experimental results are in agreement with PISCES numerical simulations 相似文献
46.
W. Harmon Ray 《加拿大化工杂志》1991,69(3):626-629
A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free-radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes. 相似文献
47.
Eleven Spectralon1 (a sintered polytetrafluoroethylene-based material) and 16 BaSO4 reference reflectance panels were calibrated using a field calibration technique. The Spectralon panels differed both in their directional/hemispherical and directional/directional reflectance. However, the differences were sufficiently small that “general” calibration equations were developed. For panels constructed of the same material and with the same methods as those used in these experiments, the directional/directional reflectance may be within ± 0.020 at 10°, ± 0.015 at 45°, and ± 0.041 at 80° of that predicted by the “general” equations. For field measurements, these values are considerably better than those that would be obtained using a value of the directional/hemispherical reflectance. The directional/directional reflectance of the 16 BaSO4 panels varied considerably among panels, so much so that it was not feasible to develop “general” calibration equations. Apparently, the nonlambertian properties of BaSO4 panels are dependent upon the method of applying the barium sulfate coating. 相似文献
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A compression moulded Kevlar-phenolic resin composite consisting of 30 wt% continuous fibres was slid against a steel disc such that the fibre axis was normal to the sliding plane. The sliding experiments were conducted in a normal pressure range of 0.47–4.27 MPa and at a sliding speed of 0.5 ms–1. The initial sliding interaction is abrasive. With further sliding, as patches of polymer transfer film develop on the polymer pin and counterface, the interaction becomes adhesive and steady-state friction is established. The wear resistance of the polymer was found to be related to the stability of this film. 相似文献