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81.
本文运用模式识别技术提出了一种分析和选择复杂系统变量的方法.运用该方法使得系
统的建模和控制简化.本文以复杂碳化过程作为实例,用模式识别技术对其内在规律进行分
析,找出了温度分布与结晶质量的定量关系.在此基础上,建立了碳化过程的动态模型.实践
表明,该模型与实际过程基本吻合,并已取得明显经济效益. 相似文献
82.
83.
Barium copper oxalate was grown in silica hydrogel at ambient temperature. The effect of various parameters like gel pH, gel
density, gel aging and concentrations of reactants on the growth of these crystals was studied. The crystals grown were characterized
by chemical analysis, X-ray powder diffractometry, infrared spectroscopy, thermogravimetric and differential thermal analysis.
The results of these observations are described and discussed. 相似文献
84.
85.
In this work, we present three different formulations, namely the pressure field integral equation formulation (PFIE), the velocity field integral equation formulation (VFIE), and the combined field integral equation formulation (CFIE) for solving acoustic scattering problems associated with two-dimensional fluid-filled bodies of arbitrary cross-section. In particular using the boundary conditions on the surface of the body, two equivalent problems, each valid for the outside and inside regions of the scatterer, are derived. By properly selecting the associated equations for these equivalent problems, the three different formulations are derived. The PFIE, VFIE, and CFIE are then solved by approximating the cylindrical cross-section by linear segments and employing the method of moments. Further, it is shown that the moment matrices generated by the PFIE and VFIE are ill-conditioned at resonant frequencies of the cylinder, whereas the CFIE generates a well-conditioned matrix at all frequencies. The solution techniques presented in this work are simple, efficient and applicable to truly arbitrary geometries. Numerical results are presented for certain canonical shapes and compared with other available data. 相似文献
86.
87.
CMOS artificial subretinal chip for natural light illumination 总被引:1,自引:0,他引:1
A novel CMOS oscillating pixel array for subretinal prosthesis used in natural light illumination is presented. Its prototype chips are fabricated in a standard 0.6 /spl mu/m CMOS technology. Experimental results show the device can deliver effective self-oscillation for subretinal electrical stimulation. 相似文献
88.
89.
Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications.
In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels
an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported
by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture
resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work
of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing
a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive
strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has
good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets
the requirements of performance and cost rendering it an attractive option for advanced structural applications. 相似文献
90.
M. Valsan D. Sundararaman K. Bhanu Sankara Rao S. L. Mannan 《Metallurgical and Materials Transactions A》1995,26(5):1207-1219
A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld
joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 ×
10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by
the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy,
scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried
out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid
hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening
followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all
strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in
base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation
in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations
during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true
at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related
to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the
growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening
of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance
of the coarse-grained region in the heat-affected zone. 相似文献