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961.
通过总结目前2D-Layout在自顶向下设计中的不足,本文提出了基于参数化的3D-Layout顶层基本框架的设计思想。采用顶层基本框架作为自顶向下设计中的核心,能够很好地解决变形设计问题,提高了产品设计的效率与准确性。 相似文献
962.
Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion and hydrogen permeation characteristics of Zn-Ni-Cd alloy coatings electrodeposited from alkaline bath were studied and compared with those of Cd and Zn-Ni coatings obtained using commercial baths. Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion potential of this Zn-Ni-Cd coating was −0.62 V vs. SCE, which is still negative potential compared to iron. The corrosion rate of Zn-Ni-Cd coated steel was 0.073 mm y−1, which is estimated in a solution at a pH of 7. This value is much lower than the corrosion rate of Zn-Ni alloy (0.502 mm y−1) and Cd (0.306 mm y−1) coatings deposited from commercial baths. Zn-Ni-Cd alloys are also demonstrated to have superior hydrogen permeation inhibition properties compared to Cd and Zn-Ni coatings. Kinetic parameters of hydrogen permeation such as the transfer coefficient, α, the modified exchange current density, i0′, thickness dependent adsorption-absorption rate constant, k″, recombination rate constant, k3, surface hydrogen coverage, θs, were evaluated by applying a mathematical model to analyze experimental results. 相似文献
963.
球磨对ZrO2(Y2O3)超细粉末性能的影响 总被引:2,自引:0,他引:2
以共沉淀法制备煅烧态ZrO2(Y2O3)超细粉末为研究对象,研究了球磨对其物理和烧结性能的影响,结果表明,球磨虽可以有效地减小粉末的团聚尺寸,但对粉末一次颗粒尺寸的的影响不大,球磨可以显著增加团聚程度较严重的锻烧态粉末的比表面积,但对团聚程度较轻的粉末,其影响大:球磨还可显著减小粉末的晶粒尺寸,这与粉末在球磨过程中发生了相变有关。此外,对团聚较严重的粉末,球磨可改善其烧结性能,但对团聚程度较轻的粉 相似文献
964.
将9SiCr钢的粒状原始组织改变为片状,再经830℃淬火后,其马氏体形态为筐篮编结状。而传统工艺所获得的马氏体形态为针状.这种筐篮编结状马氏体是9SiCr钢中一种崭新的组织形态,其精细结构为平行成束的板条。亚结构为高密度缠结位错.它有良好的综合机械性能,强韧性高,耐磨性高。 相似文献
965.
Gr(C)纤维增强镁基复合材料的界面结构 总被引:4,自引:5,他引:4
采用真空—压力浸渗工艺制备Gr(C)/Mg复合材料,Gr/Mg材料界面上无化学反应迹象,有析出物γ相(Mg17Al12),该析出物形状、大小与制备工艺条件,主要是纤维预制件温度有关。C/Mg复合材料界面Al含量较基体高出2倍多,文中分析了可能的原因 相似文献
966.
激光熔覆TiC增强FeAl金属间化合物基复合材料涂层磨损性研究 总被引:7,自引:0,他引:7
利用激光熔覆技术在1Cr18Ni9Ti奥氏体不锈钢表面制得了以TiC为增强相、以FeAl 金属间化合物为基体的耐磨复合材料涂层,研究了激光熔覆。FiC/FeAl复合材料涂层在干滑动磨损条件下的耐磨性能及磨损机制。结果表明:随着载荷和滑动速率的增加,TiC/FeAl金属间化合物基复合材料涂层的磨损速率增加,其磨损机制随着载荷的增加逐渐由磨料磨损向粘着磨损转变;激光熔覆层中TiC体积分数的增加,一方面提高了涂层的磨料磨损抗力,另一方面降低了熔覆层表面与对磨材料之间的粘着倾向,提高了TiC/FeAl涂层的滑动磨损性能。激光熔覆TiC/FeAl金属间化合物基复合材料涂层具有优异的耐磨性能并随TiC体积分数的增加而提高。 相似文献
967.
Electron Emission from Barium Strontium Titanate Ceramics 总被引:1,自引:0,他引:1
Shutao Chen Xianlin Dong Shuxin Zheng Ziqiu Zhu Chuanxiang Tang 《Journal of the American Ceramic Society》2006,89(7):2118-2122
This paper focuses on understanding the influence of materials' properties on the ferroelectric electron emission. Ferroelectric ( x =1.0 and 0.8) and paraelectric ( x =0.67 and 0.5) compositions of barium strontium titanate (Ba x Sr(1− x ) TiO3 ) system were chosen for study based on their different ferroelectric and dielectric properties. Similar emission current waveforms were obtained from four compositions with negative triggering voltage applied to the rear electrode of the samples. It was difficult to explain the experimental results using the spontaneous polarization-switching model. The mechanism of electron emission from Ba x Sr(1− x ) TiO3 ceramics was ascertained to surface plasma emission. 相似文献
968.
We have adopted the flash method to the measurement of thermal diffusivity α of polymers in the temperature range 100–400K. The pulsed radiant energy from a flash tube is applied to the ‘front’ side of a suspended sample disc, and α is deduced from the exponential decay time constant of the subsequent transient temperature difference between the ‘front’ and the ‘back’ side, while correction against radiation loss is made by measuring the much longer decay time of the back-side temperature. Calibration runs on polycarbonate (PC) samples of several thicknesses show that the method is quick, precise and fairly accurate, and the results obtained are in reasonable agreement with previous determinations. We have also carried out measurements on polyoxymethylene (POM), poly (vinylidene fluoride) (PVF2) and poly (ethylene terephthalate) (PET) and computed their thermal conductivities. Results on POM and PVF2, which are semicrystalline, are analysed in the framework of several two-phase models, and the effect of crystallization (produced by annealing) on the glass transition behaviour of PET has also been studied. 相似文献
969.
A hollow fiber membrane reactor, which resembles a tube-and-shell heat exchanger, was developed for homogeneous catalytic reactions with gas reactants and products. The gas stream flows through the tube side while the reaction takes place in the catalyst solution which fills the shell side. The separation load of product from the catalyst solution can be reduced by using a hollow fiber membrane reactor instead of a conventional bubble column reactor. The reactor operates in a plug-flow pattern with a large mass transfer area per unit volume of catalyst solution
This concept was investigated experimentally using the direct oxidation of ethylene to acetaldehyde reaction in an aqueous solution of palladium (H) chloride-cupric chloride with a silicone rubber membrane reactor and a polypropylene membrane reactor. It was experimentally demonstrated that membrane reactors could achieve higher production rates per unit volume of catalyst than the conventional sparged reactor. The experimental data were in good agreement with the predictions by the mathematical model. The conditions under which the membrane reactor will be more advantageous than the conventional sparged reactors can be readily ascertained with the analytical solution of the simplified membrane reactor model. 相似文献
This concept was investigated experimentally using the direct oxidation of ethylene to acetaldehyde reaction in an aqueous solution of palladium (H) chloride-cupric chloride with a silicone rubber membrane reactor and a polypropylene membrane reactor. It was experimentally demonstrated that membrane reactors could achieve higher production rates per unit volume of catalyst than the conventional sparged reactor. The experimental data were in good agreement with the predictions by the mathematical model. The conditions under which the membrane reactor will be more advantageous than the conventional sparged reactors can be readily ascertained with the analytical solution of the simplified membrane reactor model. 相似文献
970.
Dynamic mechanical measurements between — 180°C and 180°C were made on both isotropic and drawn samples of polybutene-1 (PB-1) and poly-4-methylpentene-1 (P4MB1) over a wide frequency range by the use of a torsional pendulum (0.3–3 Hz), a viscoelastic spectrometer (5–90 Hz) and ultrasonic technique (3 MHz). The relaxation peaks were identified and the associated activation energies determined from Arrhenius plots. For PB-1 it was observed that orientation reduces the height and shifts up the temperature of the αa-peak associated with large scale main-chain motion in the amorphous regions, but has little effect on the β-peak associated with side-group motion. In addition to the αa and β relaxations a high-temperature crystalline relaxation (αc) is also observed in P4MP1. For both the αc and β relaxations the mechanical loss at 45° to the draw direction is much larger than that at 90°, which indicates that shear processes are involved in these relaxations. 相似文献