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991.
Measurements of saturated liquid viscosities and densities were performed on environmentally acceptable hydrochlorofluorocarbons (HCFCs), CH3CCl2F (HCFC-141b), CH3CClF2 (HCFC-142b; only for viscosity), CF3CF2CHCl2 (HCFC-225ca), and CClF2CF2CHClF (HCFC-225cb), using a capillary viscometer and a glass pycnometer in the temperature range from 273 to 353 K. The uncertainty in the measurement of viscosity is estimated to be 5% based on the comparison of the present data with those in the literature for HCFC-141b. An equation is given to represent our saturated liquid viscosity data as a function of temperature. 相似文献
992.
The use of the tension-softening model for analyzing fracture processes of rock is examined with special reference to the effect of confining pressure on the fracture extension. Tension-softening curves are measured by means of theJ-based technique from unconfined tests performed on compact tension (CT) specimens of granite. On the basis of the determined tension-softening relation, numerical analyses are executed using a boundary element method (BEM) to simulate fracture of the granite under confining pressures. Numerical results are compared to the experimental results of two series of tests for which CT specimens and thick-walled cylindrical specimens were loaded to failure under confining pressures ranging from 0 to 26.5 MPa. It is shown that the BEM analyses can predict the observed fracture behavior. Based on the results, it is demonstrated that the tension-softening relation provides a suitable model to analyze the fracture process in the rock. The source mechanism for the pressure sensitive fracture is discussed by examining the growth of the fracture process zone. 相似文献
993.
Liquid viscosity and density of six binary mixtures of HFC-134a with glycols [ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (400), and polypropylene glycol (2000)] have been measured in the temperature range from 273 to 333 K. The viscosity was measured by a rolling-ball viscometer calibrated with standard liquids of viscosities and densities (JS5, JS10, JS20, and JS50). The density was measured with a glass pycnometer. The uncertainties of the measurements were estimated to be less than 3.4 % for viscosity and 0.04 % for density, respectively. An equation is given to represent the obtained viscosity values as a function of weight fraction and temperature. 相似文献
994.
Carbon fibre/poly (ether-ether-ketone) (PEEK) composites were fabricated from plain weave cloth using the commingled yarn of carbon fibres with PEEK filaments. The undirectional specimen was made from the warp of commingled yarn and the weft of PEEK yarn, while the two-dimensional specimen was made from commingled yarns both of the warp and the weft. During the hot-pressing process, PEEK filaments melt to form the matrix of the composite. The interlaminar fracture toughness of the commingled composite was measured and compared with that of the prepreg composite. The critical strain energy release rates,/'G
Ics, obtained for the commingled composites were higher than the prepreg composite. In particular, the two-dimensional composite exhibited higherG
Ic than the unidirectional commingled composite. Factors increasing the fracture toughness of commingled composites have also been investigated by SEM observation of the fractured surface. 相似文献
995.
N. Umesaki M. Takahashi M. Tatsumisago T. Minami 《Journal of Materials Science》1993,28(13):3473-3481
Raman spectra of glasses in the Li2O-SiO2 system (41.3 Li2O 61.3 mol%), prepared by rapid quenching, were measured. The proportions of SiO4 units with 1–4 non-bridging oxygens per silicon (NBO/Si) and the fractions of bridging oxygen, non-bridging oxygen and free or full-active oxygen were determined for these glasses from quantitative analysis of the Raman spectra obtained. X-ray structural analysis of Li2O-SiO2 showed an increasing elongation of the average atomic distance of the Si-O pair with increase in Li2O content due to weakening of the Si-O bond. 相似文献
996.
Ichihiko Takahashi Tokuharu Yoshii Hiroo Iidaka Eisuke Fujii Kazuyoshi Matsuoka 《Fatigue & Fracture of Engineering Materials & Structures》1993,16(1):37-51
The fatigue strength of non-load-carrying fillet welded joints of KE36(TMCP) steel was studied. Both residual stress measurements and fatigue tests were carried out, with the plate thickness, the plate width and the heat input being varied. Specimens given a Post Weld Heat Treatment (PWHT) were also prepared. The plate width had no effect on the fatigue strength, because it hardly affected the transverse residual stresses at the weld toe. However, the heat input influenced the transverse residual stress distribution, and a significant difference in fatigue strength due to the heat input was observed, especially when N≥ 106 cycles. It was also found that PWHT removed almost all the residual stresses at the weld toe, improving the fatigue strength drastically. In this study, the values of stress concentration factor K2 were estimated by Machida's method and it was concluded that the thickness effect resulted from a combination of both stress concentration and residual stresses with the contribution of the latter being particularly significant for N≥ 106 cycles. 相似文献
997.
Y. Mutoh M. Takahashi M. Takeuchi 《Fatigue & Fracture of Engineering Materials & Structures》1993,16(8):875-890
Fatigue crack growth tests of five ceramic materials were carried out in order to investigate the general characteristics of cyclic and static fatigue crack growth in ceramics. A cyclic effect was found in Si3N4, Al2O3 and TiB2, where the main fracture mechanism was intergranular separation, and stress shielding due to grain bridging occurred near the crack tip. On the other hand, no cyclic effect was observed in Sic and ZrO2, where the main fracture mechanism was transgranular fracture. The fatigue crack growth curves reduced to a unique curve by using the parameter Kup/E, regardless of the kind of ceramics studied. 相似文献
998.
Koga J. Takahashi M. Niiyama H. Iwase M. Fujisaki M. Toriumi A. 《Electron Devices, IEEE Transactions on》1994,41(7):1179-1183
Under cryogenic operation, a low Vth realizes a high speed performance at a greatly reduced power-supply voltage, which is the most attractive feature of Cryo-CMOS. It is very important in sub-0.25 μm Cryo-CMOS devices to reconcile the miniaturization and the low Vth. Double implanted MOSFET's technology was employed to achieve the low Vth while maintaining the short channel effects immunity. We have investigated both the DC characteristics and the speed performance of 0.25 μm gate length CMOS devices for cryogenic operation. The measured transconductances in the saturation region were 600 mS/mm for 0.2 μm gate length n-MOSFET's and 310 mS/mm for 0.25 μm gate length p-MOSFET's at 80 K. The propagation delay time in the fastest CMOS ring oscillator was 22.8 ps at Vdd=1 V at 80 K. The high speed performance at extremely low power-supply voltages has been experimentally demonstrated. The speed analysis suggests that the sub-l0 ps switching of Cryo-CMOS devices will be realized by reducing the parasitic capacitances and through further miniaturization down to 0.1 μm gate length or below 相似文献
999.
Effective interaction of two-dimensional liquid 3He is studied with the (selfconsistent) reaction matrix theory. The theory is found to be valid in the dilute region, 2D
0.02 Å–2, where 2D
is the areal density. In the region, the attractive interaction in the p-wave channel is the most dominant, and the system is expected to undergo a transition to a p-wave superfluid state, except for the dilue limit. The transition temperature is estimated to be of the order of mK in the clean limit. In the dilute limit, 2D
0.002 Å–2, an s-wave superfluid state becomes more stable than a p-wave one, but the transition temperature is found to be of the order of 0.1 mK at most. Furthermore, in the reaction matrix theory, it is found that a d-wave superfluid state becomes more stable than a p-wave one at 2D
0.035 Å–2. 相似文献
1000.
Seiji Yamashita Hideo Watanabe Takashi Shirai Masayoshi Fuji Minoru Takahashi 《Advanced Powder Technology》2011,22(2):271-276
We have successfully synthesized zinc oxide microrods perpendicularly oriented on hexagonal ZnO sheets by a simple heat treatment approach using LDH (layered double hydroxide) precursor in an aqueous solution. The synthesized ZnO microrods have an average diameter of 500 nm and length of 2–3 μm, and form highly-oriented array. In this work, the effect of heating temperature and time on morphology and orientation of ZnO microrods was studied experimentally and the formation mechanism was discussed in detail. Transformation from hexagonal precursor to ZnO microrods can be attributed to dissolution and re-precipitation of the precursor, which should be caused by its thermal unstability under heating temperature. 相似文献