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991.
Microfibre reinforced cement composites reinforced with high volume fractions of carbon, steel and polypropylene fibres were tested in uniaxial tension. Composites investigated included those with only one type of fibre (mono-fibre composites) and those with two or more types of fibres (hybrid-fibre composites) in the same mix. Considerable strengthening, toughening and stiffening of the host matrix due to microfibre reinforcement were observed. In the hybrid-fibre composites, different fibres appear to act as additive phases; i.e., they maintain their individual reinforcing capabilities. The composites were also impact tested in uniaxial tension using a newly designed instrumented impact machine. When compared with static test results, considerable sensitivity to stress rate was noted; composites were found to be stronger and tougher under impact and the improvements were more pronounced at higher fibre volume fractions. The potential of these composites for use in thin sheet products and other similar applications is recognized, and the need for continued research is stressed. 相似文献
992.
对经固溶处理的二种Al-Li合金(1.94wt.%Li和2.75wt.%Li)的时效过程进行了研究。结果表明:δ’的生长速率遵从Ostward粗化动力学。1.94wt.%Li合金δ’产生于时效过程中,而2.75wt.%Li合金的δ’产生于时效的前期阶段。前者的表现体积分数明显大于根据相图估算的数伍,真实体积分数则与此值接近;后者的体积分数低于根据相图估算的数值,这可能归咎于δ’固相线的位置、统计学误差及Li更易在时效过程中贫化。 相似文献
993.
In a survey of the practical wind energy resource present in the Tayside Region of Scotland it was estimated that over 1500 km2 of land is suitable for wind energy development in the Region after consideration of a range of physical, technical and institutional factors. Wind speed data for this survey was obtained from the Energy Technology Support Unit (ETSU) UK Wind Speed Data Package. To verify the wind speeds obtained from the ETSU package a representative sample of sites in and around the identified areas of potential in Tayside were modelled for mean annual wind speed using the Wind Atlas Analysis and Application Program (WAsP). The wind speeds for the sites obtained from the WAsP analysis were compared with those obtained from the ETSU UK Wind Speed Data Package and conclusions drawn as to the reliability of the Tayside wind energy survey and the general applicability of the ETSU package for broad wind energy resource assessment. 相似文献
994.
While high-performance organic fibres such as poly (para phenylene benzobisthiazole) and Kevlar possess excellent mechanical properties under axial tension, their strength under compression is generally poor. This study focuses on a polymer infiltration approach to modify the mechanical properties of the Kevlar 49 fibre in tension as well as compression, in which various polymeric resins are infiltrated in an opened fibrillar network of Kevlar single filaments. Opening was achieved using concentrated sulfuric acid, which resulted in a strength loss at high acid concentrations. However, compared to the acid-treated fibre, both the tensile strength and strain-to-failure of the fibres were found to increase after infiltration with epoxy resins and bismaleimide polymers. Polymer infiltration also resulted in a significant improvement in the compressive strength of the Kevlar fibre, with the bismaleimide performing better than the epoxy resins. Plasma modification using ammonia was also used to enhance interfibrillar adhesion by incorporating reactive amine groups on the fibril surface 相似文献
995.
Stanisic B.R. Verghese N.K. Rutenbar R.A. Carley L.R. Allstot D.J. 《Solid-State Circuits, IEEE Journal of》1994,29(3):226-238
This paper describes new techniques for the simulation and power distribution synthesis of mixed analog/digital integrated circuits considering the parasitic coupling of noise through the common substrate. By spatially discretizing a simplified form of Maxwell's equations, a three-dimensional linear mesh model of the substrate is developed. For simulation, a macromodel of the fine substrate mesh is formulated and a modified version of SPICE3 is used to simulate the electrical circuit coupled with the macromodel. For synthesis, a coarse substrate mesh, and interconnect models are used to couple linear macromodels of circuit functional blocks. Asymptotic Waveform Evaluation (AWE) is used to evaluate the electrical behavior of the network at every iteration in the synthesis process. Macromodel simulations are significantly faster than device level simulations and compare accurately to measured results. Synthesis results demonstrate the critical need to constrain substrate noise and simultaneously optimize power bus geometry and pad assignment to meet performance targets 相似文献
996.
As an alternative to surgical splenectomy, partial splenic embolization was performed in seven children for hypersplenism manifested by splenomegaly, thrombocytopenia, leukopenia, and erythrocyte hemolysis. Within a few days, platelet and leukocyte counts rose significantly in all patients and were maintained in six of seven patients during a follow-up period of 9 to 69 months. Spleen size and abdominal distention also decreased significantly in all children. There were no infectious complications. 相似文献
997.
998.
N. M. Agh-Atabay W. Edward Lindsell Peter N. Preston Peter J. Tomb 《Polymer International》1993,31(4):367-374
Symmetrically substituted 1,3-diynes containing hydroxyalkyl ( 1a-d ), bromoalkyl ( 1e-h ) (diphenylphosphinyl) ( 1i-k ) and carboxyalkyl ( 2a-d ) substituents have been prepared and characterised; the phosphine derivative ( 1k ) has been converted with alkyl iodides ( RI ; R = Me, Et) into bis(phosphonium) salts ( 1l and m ). During preparation of the diynedioic acid. ( 2a ), the non-centrosymmetrical diyne, HO2CCH2C?C—C?C(CH2)2OH ( 3 ), was also isolated. 60Co γ-Irradiation of diacetylene monomers ( 2a – d ) and 10,12-tricosadiyn-1-oic acid gave the corresponding polydiacetylene derivatives ( 4a – d and 5 ), respectively. Rubidium salts of ( 4c ) and ( 4d ), a barium salt of ( 4c ), and a potassium salt of ( 5 ) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers ( 4 ) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed. 相似文献
999.
N Nishioka T Kawabata KH Minagawa M Nakamura A Oshima Y Mochizuki 《Canadian Metallurgical Quarterly》1996,43(6):434-445
The purpose of this study was to evaluate the short-term effect of a smoking prevention program for Japanese elementary school-children in the fifth and sixth grades. The program was developed with concepts found in the Know Your Body Program and the conclusions of a National Cancer Institute-convened Expert Advisory Panel, and focused on teaching about the short-term effects of smoking and on resistance to social pressures to smoke. The study was conducted with a quasi-experimental design. An intervention group (52 boys and 54 girls) received three sessions for both the fifth grade in 1992 and the sixth grade in 1993. Moreover, the intervention group received a pre-test before the first session and a post-test after the third session in each grade. A comparison group (102 boys and 91 girls) received the same tests at the same time as the intervention group, but did not receive any program on smoking prevention. The short-term effect of the program were evaluated using the results of the pre-test in the fifth grade and of the post-test in the sixth grade in both groups. The results were as follows: 1) Remarkable short-term effects of the intervention were seen in respect to awareness of the importance of not smoking in girls, and also in the knowledge of the short-term effects of smoking in both sexes. 2) The intervention was not effective with respect to intention to smoke at the age of 20 and self-efficacy of refusing to smoke in both sexes. 3) The short-term effects were not clear in the smoking behavior in both sexes because the rates of ever smokers and of monthly smokers were almost the same for two years between the intervention group and the comparison group. 4) The smoking behaviors of children, their parents and their best friends had little influence on the results of the post-test in the sixth grade. 相似文献
1000.
Based on periodic solutions of the governing heat conduction equations in a single zone building, computer software ADMIT has been developed for thermal simulation of buildings. Standard computer software, namely TRNSYS and SUNCODE, have also been used to simulate the same building under similar conditions. Simulations have been performed for three different climatic zones in India for light and heavy constructions under conditions of glazed/unglazed areas and ventilation rates. The results are presented in terms of the hourly variation of the room temperature. For insulated heavy construction, the results of different models are significantly different. This difference is due to the use of different approaches to solve the heat conduction equations. SUNCODE depends on the RC network approach and underestimates the heat losses. TRNSYS uses the transfer function approach, which is sensitive to the initially assumed value of the room temperature. ADMIT represents a quasi-steady-state periodic variation and is not suitable for transient variations. For insulated light buildings, the heat transfer mechanisms used in the mathematical models are not the governing factors. The models also differ in treating the penetration of solar radiation through a glazed window and the subsequent heat-transfer mechanism. For a south window and air changes in an insulated building, the results obtained by SUNCODE and ADMIT are in good agreement, but the results obtained by TRNSYS are considerably different. The reason for this needs detailed analysis. 相似文献