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141.
The work shows the results obtained in recognition of different types of austenitic steels with an ultrasonic system that provides the necessary data towards two different neural networks. One of the neural networks (RNAU) used as input a vector containing processed data (propagation velocity and ultrasonic attenuation). The second neural network (AUFRAN) used the amplitude of digitized radio-frequency signal and its numerical Fourier transform as input vector.Two thirds of data obtained from three kinds of steels (W.1.4541, W.1.6903 and HP50) were used in the learning process. The last third of acquired data on these samples were used in the testing process. The obtained classification probabilities were above 98.3%. As a supplement, the testing process was extended to three other types of austenitic steels having different chemical compositions than those used in the learning process. 相似文献
142.
On MDS codes via Cauchy matrices 总被引:1,自引:0,他引:1
Roth R.M. Lempel A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1989,35(6):1314-1319
A special form of Cauchy matrix is used to obtain a tighter bound for the validity region of the maximum distance separable (MDS) conjecture and a new compact characterization of generalized Reed-Solomon codes. The latter is further used to obtain constructions and some existence results for long [2k , k ] double-circulant MDS codes 相似文献
143.
A questionnaire measuring 26 group leader characteristics investigated by Lieberman, Yalom and Miles (1973) was administered to 204 experienced group leaders distributed geographically throughout the United States. A confirmatory factor analysis of the data revealed no support for the factor structure previously reported by Lieberman et al. Principal-components analysis with varimax rotation was performed, and an eight-factor solution was adopted. The factors pertained to group leader behavior or style (i.e., Cognitive Direction, Affective Direction, Behavioral Direction, and Nonverbal Exercises), leader personal qualities (i.e., Nurturant Attractiveness and Charismatic Expertness), and leader objectives (i.e., Group Functioning and Personal Functioning). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The corrosion and passivation behaviour of bulk polycrystalline martensite Ni50Mn30Ga20 and austenite Ni48Mn30Ga22 alloys was compared in electrolytes with different pH values. Linear anodic and cyclic potentiodynamic polarisation methods and anodic current transient measurements have been conducted for the alloys and their constituents to analyze free corrosion, anodic dissolution and passive layer formation processes. Electrochemically treated alloy surfaces were characterized with scanning electron microscopy (SEM) and angle-resolved x-ray photoelectron spectroscopy (XPS). The electrochemical response of both alloys is in principal similar and is dominated by the Ni oxidation. In acidic solutions (pH 0.5 and 5) a slightly higher reactivity is detectable for the martensitic alloy which is mainly attributed to enhanced dissolution processes at the multiple twin boundaries. In weakly acidic to strongly alkaline solutions (pH 5-11) both alloys exhibit a low corrosion rate and a stable anodic passivity. While air-formed films comprise NiOOH, Ga2O3 and MnO2, passive films formed in near neutral media (pH 5-8.4) are composed of Ni(OH)2, NiOOH and Ga2O3 in the outer region and of NiO, MnO2 and MnO in the metal-near region. 相似文献
146.
E. Dul’kin V. Beilin E. Yashchin M. Roth L. V. Grebenkina 《Technical Physics Letters》2001,27(5):387-388
The secondary sintering of a Bi-2223/Ag ribbon, following the stages of primary sintering and rolling to a strain of ε∼18%, was studied by methods based on the acoustic emission, thermal expansion, and magnetic susceptibility measurements. During the second thermal treatment, a signal of acoustic emission from the ribbon was detected in a temperature range from 570 to 660°C. The process of liquid-phase healing of the rolling cracks in the ribbon material is considered as a reason of the acoustic emission. The possibility of using the acoustic emission measurements for nondestructive testing in the Bi-2223/Ag ribbon fabrication technology is considered. 相似文献
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149.
Edward R. Generazio Don J. Roth David B. Stang 《Journal of the American Ceramic Society》1989,72(7):1282-1285
A silicon carbide disk was sintered from 2090° to 2190°C in 25°C steps. After each sintering step, the disk was examined using a precision acoustic scanning system to determine acoustic attenuation and velocity. The bulk density was found to vary non-monotonically with sintering temperature. The density varied as much as 10% from its value at 2090°C during the sintering process. Local density fluctuations occurred in an organized and history-dependent way. These local density fluctuations varied up to ±7% of the bulk density and were made visible by acoustic attenuation and velocity mapping. 相似文献
150.
The thermal conductivities of three plasma-sprayed cermets have been determined over the temperature range 23–630°C from the measurement of the specific heat, thermal diffusivity, and density. These cermets are mixtures of Al and SiC prepared by plasma spray deposition and are being considered for various applications in magnetic confinement fusion devices. The samples consisted of three compositions: 61 vol% Al/39 vol% SiC, 74vol% Al/26vol% SiC, and 83 vol% Al/17 vol% SiC. The specific heat was determined by differential scanning calorimetry through the Al melt transition up to 720°C, while the thermal diffusivity was determined using the laser flash technique up to 630°C. The linear thermal expansion was measured and used to correct the diffusivity and density values. The thermal diffusivity showed a significant increase after thermal cycling due to a reduction in the intergrain contact resistance, increasing from 0.4 to 0.6 cm2·–1 at 160°C. However, effective medium theory calculations indicated that the thermal conductivities of both the Al and the SiC were below the ideal defect-free limit even after high-temperature cycling. The specific heat measurements showed suppressed melting points in the plasmasprayed cermets. The 39 vol% SiC began a melt endotherm at 577°C, which peaked in the 640–650°C range depending on the sample thermal history. Chemical and X-ray diffraction analysis indicated the presence of free silicon in the cermet and in the SiC powder, which resulted in a eutectic Al/Si alloy.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献