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91.
A self-consistent scheme is used in order to determine the permeability of a cracked porous medium. For weak values of the permeability of the uncracked porous matrix, it is found that the order of magnitude of the permeability increases beyond a critical threshold of the crack density parameter. In the framework of a micromechanical model, it is shown that both the evolution of crack opening and the crack propagation are controlled by Terzaghi's effective stress which therefore captures the coupling between permeability and mechanical loading. To cite this article: L. Dormieux, D. Kondo, C. R. Mecanique 332 (2004). 相似文献
92.
为研究不同围压条件下孔隙介质的渗透性能,利用新研制的高压渗流仪,对大尺寸低渗透性软弱岩进行了系统的试验测试。试验渗透压差波动幅度仅为0.02MPa,渗出端溶液体积变化量测试精度可达0.03mL。通过溶液体积变化与时间的线性关系,稳定渗流量大小可以精确测定。以稳定压差、流量法(即稳压法),试验验证了岩石的渗透系数随着围压的增加而下降,当围压降低时,岩石渗透系数回升,但回升路径低于原始路径。根据轴向应变的变化情况,提出了室内试验应力-渗流耦合过程中渗透性的变化主要是侧向压力使孔隙、喉道产生压缩变形所致。 相似文献
93.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1185-1197
The polymerization of 4,4-bis(t-butylbenzoylmethyl)-1,6-hepta-diyne (BTBH) was carried out by group 5,6-transition metal catalysts. MoCl5- as well as WCl6-based catalysts were effective for the cyclopolymerization of BTBH. The polymer structure was analyzed to have conjugated backbone and recurring 5-membered ring by various spectroscopes. The polymer showed good solubility in common organic solvents. The polymer had good thermal stability and mechanical property. The oxygen permeability coefficient (PO2) and permselectivity of oxygen to nitrogen (PO2/PN2) of poly(BTBH) with bulky and rigid t-butyl benzoyl group were 23.2 barrer and 4.63, respectively. 相似文献
94.
Yu-Ming KuoJenq-Gong Duh 《Applied Surface Science》2011,257(15):6387-6390
High permeability magnetic films can enhance the inductance of thin-film inductors in DC-DC converters. In order to obtain high permeability, the uniaxial anisotropy and coercivity should be as low as possible. This study employed dc reactive magnetron sputtering to fabricate nanocrystalline FeHfN thin films. The influence of the nitrogen flow on the composition, microstructure, and permeability characteristics, as well as magnetic properties was investigated. Increasing the nitrogen content can alter FeHfN films from amorphous-like to crystalline phases. The magnetic properties and permeability depend on variations in the microstructure. With the optimum N2/Ar flow ratio of 4.8% (N2 flow: 1.2 sccm), low anisotropy (HK = 18 Oe), low coercivity (HC = 1.1 Oe) and high permeability (μ′ > 600 at 50 MHz) were obtained for fabrication of a nanocrystalline FeHfN film with a thickness of around 700 nm. Such as-fabricated FeHfN films with a permeability of over 600 should be a promising candidate for high-permeability ferromagnetic material applications. 相似文献
95.
Samaila Bawa Waje Mansor Hashim Ismayadi Ismail 《Journal of magnetism and magnetic materials》2011,323(11):1433-1439
Nanoparticle-sized Co0.2Ni0.3Zn0.5Fe2O4 was prepared using mechanical alloying and sintering. The starting raw materials were milled in air and subsequently sintered at various temperatures from 600 to 1300 °C. The effects of sintering temperature on physical, magnetic and electrical characteristics were studied. The complex permittivity and permeability were investigated in the frequency range 10 MHz to 1.0 GHz. The results show that single phase Co0.2Ni0.3Zn0.5Fe2O4 could not be formed during milling alone and therefore requires sintering. The crystallization of the ferrite sample increases with increasing sintering temperature; which decrease the porosity and increase the density, crystallite size and the shrinkage of the material. The maximum magnetization value of 83.1 emu/g was obtained for a sample sintered at 1200 °C, while both the retentivity and the coercivity decrease with increasing the sintering temperature. The permeability values vary with both the sintering temperature and the frequency and the absolute value of the permeability decreased after the natural resonance frequency. The real part of the permittivity was constant within the measured frequency, while the loss tangent values decreased gradually with increasing frequency. 相似文献
96.
Sorption and permeability measurements have been performed to determine the transport parameters of carbon dioxide through dense homogeneous PEEKWC membranes. The enthalpy of solution of CO2 is exothermic. The concentration dependence of diffusion has been measured. Permeability coefficients obtained from sorption data have been compared with the experimental values, obtaining a good agreement. 相似文献
97.
Jie Dai Chuan-Ling Li Ye-Zhong Zhang Qi Xiao Ke-Lin Lei Yi Liu 《Thermochimica Acta》2008,470(1-2):77-82
The effect of lanthanum on mitochondria isolated from hybrid rice Fengyou 559 (Oryza sativa L.) was investigated. Through in vivo culture, low-dose La3+ promoted, but higher dose La3+, restrained mitochondrial heat production. However, through in vitro incubation, La3+ manifested only inhibitory action on mitochondrial energy turnover, the concentration required for 50% and 100% inhibition being 50.9 and 230.2 μM (57.6 nmol/mg protein), respectively. In addition, La3+, like Ca2+, induced rice mitochondrial swelling and decreased membrane potential (Δψ), which was inhibited by the specific permeability transition inhibitor cyclosporine A (CsA). The induction approached a constant limitation while mitochondrial metabolism was completely prevented by La3+, and microscopy observation showed a high disruption of inner mitochondrial membrane in this state. These results demonstrated that lanthanum influenced rice mitochondria in vivo and in vitro via different action pathways, and the latter involved the opening of rice mitochondrial permeability. 相似文献
98.
Scott D. Kelman Brandon W. Rowe Christopher W. Bielawski Steven J. Pas Anita J. Hill D.R. Paul B.D. Freeman 《Journal of membrane science》2008,320(1-2):123-134
Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) has been crosslinked using 3,3′-diazidodiphenylsulfone to improve its solvent resistance and physical stability. This study reports the influence of crosslinking on N2, O2 and CH4 gas permeabilities and fractional free volume (FFV) as a function of time. Crosslinking PTMSP renders it insoluble even in excellent solvents for the uncrosslinked polymer. The gas permeability and FFV of uncrosslinked and crosslinked PTMSP decreased over time, so crosslinking PTMSP does not arrest physical aging. The addition of 10 wt.% polysiloxysilsesquioxanes (POSS) nanoparticles decreased the permeability of PTMSP by 55%, and the permeability and FFV values were stable over time for PTMSP films containing 10 wt.% POSS nanoparticles. The permeability of PTMSP at a given FFV was greater than that of other substituted polyacetylenes, polysulfones or polycarbonates, which is consistent with differences in the arrangement of free volume in these polymers, as probed by positron annihilation lifetime spectroscopy (PALS). Ellipsometry was used to characterize physical aging of thin (400 nm) uncrosslinked and crosslinked PTMSP films supported on silicon wafers. The ellipsometry results showed that crosslinking does not markedly slow physical aging of thin PTMSP films. 相似文献
99.
Chitosan macroporous membranes with asymmetric morphology were obtained by using an inorganic porogen agent (SiO2). Chitosan/silica ratios used were 1:1, 1:3, and 1:5 w/w. A methodology to obtain asymmetric membranes with control of porosity and average pore size was proposed. The porous membranes were obtained taking advantage of the opposite solubility characteristics of chitosan and silica (4–20 μm). The membranes were characterized by SEM and water sorption capacity. The porosity was calculated by the relationship between dense and macroporous membranes. The SEM images of both surfaces and cross-section of the membranes confirmed their asymmetric morphology. Using a double-cell method, the permeability coefficients of two model drugs (sodium sulfamerazine and sulfametoxipyridazine) were determined. The effects of porous layer, drug type, concentration and temperature were evaluated. The results revealed that the increase in porosity results in significant differences in permeability and that the effects of drug concentration and bath temperature become less pronounced as porosity increases. The mass transport was analyzed in terms of pore-flow mechanism and the solution-diffusion mechanism. The results showed that the methodology was very efficient to yield asymmetric membranes with good mechanical resistance, control of porous size and dense layer thickness and that these membranes can potentially be used to the transport of drugs. 相似文献
100.
Poly(vinylalcohol)/poly(ethyleneglycol)/poly(ethyleneimine) blend membranes were prepared by solution casting followed by
solvent evaporation. The chemical structure of the prepared membranes was analyzed by FTIR and DSC. The sorption behavior
as well as the permeabilities of the membranes for pure CO2 and N2 were investigated. The results show that the PVA/PEI/PEG membranes possess a higher permeability of CO2 and a lower permeability of N2. The membrane displays a CO2 permeability of 27 Barrer, and a N2 permeability of 3 Barrer at 25°C and 1 bar. CO2 sorption behavior of the composite membrane, which can be classified as a dual-mode sorption model, and N2 sorption behavior of the copolymeric membrane is in agreement with the Fickian diffusion model.
相似文献