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81.
V. I. Gulyaev P. Z. Lugovoi V. V. Gaidaichuk I. L. Solov’ev I. V. Gorbunovich 《International Applied Mechanics》2007,43(9):1017-1023
A mathematical model is proposed to describe the critical quasistatic equilibrium of long rotating drillstrings. The prestress
of drillstrings by the gravity and torsion forces, the gyroscopic interaction of rotary and linear motions, and the destabilizing
effect of the internal flow of the drilling fluid are taken into account. The phenomena accompanying the drilling to different
depths are studied numerically
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 83–92, September 2007. 相似文献
82.
Voronov V. P. Belyakov M. Yu. Gorodetskii E. E. Kulikov V. D. Muratov A. R. Nagaev V. B. 《Transport in Porous Media》2003,51(2):123-140
The adiabatic calorimetry method is used to measure the isochoric heat capacity and the dew-bubble curves for the methane-normal pentane mixtures in bulk for three different mixture compositions of n-pentane. The near-critical behavior of the mixture heat capacity indicates that at low n-pentane concentrations, this system is close to the special point of the critical locus. The effect of porous medium has been investigated for one of the mixtures studied in bulk. It has been shown that in porous medium the essential shift of the dew-bubble curve takes place. In our opinion this shift is caused by the formation of wetting film on the surface of porous medium. The estimation of film thickness resulting from the data obtained yields the value 7–8 nm. 相似文献
83.
84.
The rheology of tetrafluoroethylene/hexafluoropropylene (TFE/HFP) copolymers, also known as Teflon FEP polymers, having different
molecular weight and composition (HFP content) was studied by means of a parallel-plate rheometer. Two groups of polymers
having different molecular weights with nearly constant polydispersity (around 2.5) were considered; namely, one group having
a relatively low melting temperature (amorphous with a high content of HFP) and a second group having a higher melting point
(semi-crystalline with a lower content of HFP). The relaxation time spectrum, H(λ), calculated by use of the BSW model (developed for monodisperse linear polymers) followed a scaling relationship in the
terminal zone with scaling exponent of 0.13. However, at higher frequencies the model fails to predict adequately the experimental
data. The longest relaxation time calculated from both the BSW model and discrete relaxation spectra (λ
i
,g
i
), which was determined by use of a parsimonious fitting software, depends on the molecular weight in a similar way as the
zero-shear viscosity does with the well-established scaling factor of 3.4. The critical molecular weight for the onset of
entanglements, M
c
, was found to be about 100000, a value much higher than those previously reported in literature for other polymers. The rheology
of resins in the second group (higher melting point) was found to exhibit a strong dependence on thermal history during oscillatory-shear
measurements. The data obtained in experiments at different temperatures without a preheating to a certain value (330°C) exhibited
a violation of the time-temperature superposition principle and no well-defined values of the zero-shear viscosity. This is
attributed to residual crystallinity even at temperatures well above their melting point (260°C). However, the same experiments
with preheating and subsequent cooling to desired temperature resulted into a very good time-temperature scaling.
Received: 13 January 1998 Accepted: 6 April 1998 相似文献
85.
PBX颗粒力学性质对其撞击感度影响的初步研究 总被引:1,自引:0,他引:1
利用自行研制的应力测试系统研究了在机械撞击作用下粉状塑料粘结炸药(PBX)的表现。结果表明,由不同的聚氨酯(PU)溶液处理黑索今(RDX)得到的混和炸药PU-RDX,在机械撞击作用下给出的应力-时间曲线是多样的。而且PU-RDX的机械撞击感度随出现第二个应力峰的时间比(指不同的PU-RDX第二应力峰出现时间和仪器在空打时相应时间比)的增大,有下降的趋势。该时间比在一定程度上代表了粉状PU-RDX的塑性。研究在机械撞击作用下PBX的应力-时间特性有助于理解钝感炸药的机理、改进有关的工艺。 相似文献
86.
利用阻尼来抗震是建筑物最简单的抗震方法,当在阻尼数目少于楼层数时,为使所布置的阻尼达到最优的抗震效果,本文开发了两种最优阻尼配置方法。第一种方法是根据临界激励法确定计算所有可能布置位置中的临界阻尼,选择最小的临界阻尼位置作为最优配置。第二种方法则是根据给定阻尼,计算最优控制效果以确定最优阻尼配置。然后根据实代码遗传算法,在结构抗震效果基本保证的前提下,寻找最优阻尼以降低结构总的阻尼增量。最后给出了一个计算实例。 相似文献
87.
88.
89.
Effects of ultrasonic on desulfurization ratio from bauxite water slurry (BWS) electrolysis in NaOH solution were examined under constant current. The results indicated that ultrasonic improved the desulfurization ratio at high temperatures because of the diffusion and transfer of oxygen gas in electrolyte. However, due to the increase in oxygen gas emission, ultrasonic could not improve the desulfurization ratio obviously at low temperatures. Additionally, the particle size of bauxite became fine in the presence of ultrasonic, indicating that the mass transfer of FeS2 phase was improved. According to the polarization curves, the current density increased in the presence of ultrasonic, indicating that the mass transfer of liquid phase was improved. The apparent activation energy (AAE) of electrode reaction revealed that ultrasonic did not change the pathway of water electrolysis. However, ultrasonic changed the pathway of BWS electrolysis, converting indirect oxidation into direct oxidation. The AAE of BWS electrolysis in the presence of ultrasonic was higher than that in the absence of ultrasonic. And the low AAEs (less than 20 kJ/mol) clearly indicated the diffusion control during BWS electrolysis reaction. 相似文献
90.
We define two transforms of non‐conformal harmonic maps from a surface into the 3‐sphere. With these transforms one can construct, from one such harmonic map, a sequence of harmonic maps. We show that there is a correspondence between harmonic maps into the 3‐sphere, H‐surfaces in Euclidean 3‐space and almost complex surfaces in the nearly Kähler manifold . As a consequence we can construct sequences of H‐surfaces and almost complex surfaces. 相似文献