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741.
In the present paper a method is presented for the analysis of rock interface. The mechanical response of rock interface involves
nonlinear unilateral phenomena as debonding and slip along the interface. Under the usual simplifying assumption of shear-normal
stress decoupling, the problem has been studied in [1,2] by means of variational and hemivariational inequalities formulations.
This assumption is here dropped and the problem is formulated in the form of a system of inequalities. Using Leray-Schauder
degree theory together with regularization techniques based on mollifiers, we develop a mathematical theory applicable to
the analysis of the aforementioned problem.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
742.
在间歇反应器中 ,反应温度为 30~ 6 0℃ ,硝酸初始浓度 30~ 5 4 % ,磷矿初始粒径 0 .375~ 1.0 75毫米 ,搅拌强度 4 0 0转 分的条件下研究了硝酸分解磷矿的反应过程机理及宏观动力学。结果表明 ,磷矿分解速率及转化率随着搅拌强度、反应温度、硝酸浓度和颗粒细度的增加而增加 ;氢离子通过液膜的扩散传质是该过程的速率控制步骤。应用固体粒径减小的缩芯模型 ,将上述各影响因素的实验数据回归得到如下的宏观动力学模型 :1- (1-xB) 2 3=8.36 6exp - 6 .198× 10 3RT c1 .31 1AO R- 0 .1 0 91S lnτ活化能Ea=6 .198kJ mol,属液膜扩散传质控制 相似文献
743.
A lot of granitoid rocks occur in Panxi area, SW China, which were formed during Jinningnian-Chengjiangnian, Hercynian-Indosinian and Yenshanian. According to their trace elements geochemical and petrochemical characteristics, they can be divided into calc-alkaline and alkaline granites. The petrogenesis and magma sources of these granitoid rocks are different. The Jinningnian-Chengjiangnian granitoid rocks include Mopanshan granite body, Moshaying granite body and Lugu granite body. The Mopanshan body might be formed by partial melting of the lower crust and due to refusion of basic volcanic rocks. The magma source of the Moshaying and the Lugu bodies might be formed by partial melting of the upper crust. The Hongge-Ailanghe granites belonging to the Hercynian-Indosinian may be products of complex melting from the crust-mantle materials caused by the increase of temperature during rifting stage in the area. The Cida and Taihe alkaline granites belonging to the Hercynian-Indosinian might be derived from 相似文献
744.
745.
Summary A combined cation-exchange separation-spectrophotometric procedure has been worked out for the accurate determination of traces
of copper in silicate rocks. Silicates are opened up with sulfuric and hydrofluoric acids. The residue is taken up into a
0.5 M hydrochloric acid −0.05 M oxalic acid −1% hydrogen peroxide solution and loaded on a strongly acidic cation-exchange
resin column. Polyvalent ions including ferric ions do not adsorb on the column, while copper (II) retains together with divalent
metal ions as well as aluminum (III). Copper (II) can selectively be eluted by a small volume of 0.05 M thiosulfate solution.
This fraction is sufficiently pure to allow a direct spectrophotometric determination of copper with Na-DDTC without the addition
of tartrate and EDTA as masking agents. Quantitative results are quoted for the determination of copper in international standard
rocks of the Geological Survey of Japan (GSJ) and the U.S. Geological Survey (USGS). 相似文献
746.
747.
Francisco G.Emmerich Alfredo G.Cunha Carlos M.A.Girelli Arnobio I.Vassem 《Acta Mechanica Solida Sinica》2008,21(4):333-336
A characteristic of the fracture and cleavage experiments is that they are usually intrinsically destructive. Cracks do not completely heal in an unstressed system, even in crystals such as mica. Here, we used magnetic solids composed of magnetic strips for the non-destructive cleavage and brittle fracture experiments. Between the magnetic strips materials with different mechanical characteristics can be inserted, such as Teflon or foam strips, to change the mechanical properties of the solid. For the cleavage experiments, we developed an apparatus where parameters such as the main involved force can be measured easily. By inserting flaws, the magnetic solid can be used in dynamic fracture experiments, with the advantages of simulating macroscopically a non-destructive experiment in an easier way, that happen in real materials with much higher velocities. The apparatus and the used magnetic solid may be useful for demonstrations of fractures in classes. 相似文献
748.
The relation between chain structure and ductile–brittle transition (DBT) in polyestercarbonates (PEC) was investigated by measuring the fracture energy and observing the fracture surfaces of a homologous series of PEC containing phthalate units. DBTs were determined in terms of various test conditions including specimen thickness, test speed, and notch-tip radius. With an increase in the phthalate content, transition was found to shift to a thinner specimen, a lower test speed, and a higher notch-tip radius. It was concluded that the DBT is directly affected by the extent of entanglement in these copolymers. 相似文献
749.
J. T. A. Kierkels C.‐L. Dona T. A. Tervoort L. E. Govaert 《Journal of Polymer Science.Polymer Physics》2008,46(2):134-147
Mechanical rejuvenation is known to dramatically alter the deformation behavior of amorphous polymers. Polystyrene (PS)—for example, typically known as a brittle polymer—can be rendered ductile by this treatment, while a ductile polymer like polycarbonate (PC) shows no necking anymore and deforms homogeneously in tensile deformation. The effects are only of temporary nature, as because of physical aging the increasing yield stress, accompanied by intrinsic strain softening, renders PS brittle after a few hours, while for PC necking in tensile testing returns in a few months after the mechanical rejuvenation treatment. In this study, it is found that physical aging upon rejuvenation in both PS and PC can be delayed in two different ways: (1) by reducing the molecular mobility through antiplasticization and (2) by applying toughening agents (rubbery core–shell particles). For the first route, even though progressive aging is found to decrease with increasing amounts of antiplasticizer added, dilution of the entanglement network results in enhanced brittleness. Besides antiplasticization effects, also some typical plasticization effects are observed, like a reduction in matrix Tg. For the second route, traditional rubber toughening using acrylate core–shell modifiers also results in a reduced yield stress recovery, and ductile tensile deformation behavior is observed even 42 months after mechanical rejuvenation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 134–147, 2008 相似文献
750.
Sang‐Soo Lee Kilwon Cho Joonkyung Kim 《Journal of Polymer Science.Polymer Physics》2001,39(21):2635-2643
The deformation behavior of bisphenol A polycarbonate containing only a small amount of oligoionomeric additives in the range of a few parts per hundred parts of resin was examined. The impact strength of polycarbonate markedly decreased as the content of additive increased, and brittle fracture of polycarbonate was observed in tensile tests when the concentration of additive was above 2.5 phr. The ductile‐to‐brittle transition that was determined using a comparison of the critical shear yield stress and the critical craze stress appeared to exist in the range of 2.5–3.5 phr of additive. The measured entanglement density was also found to decrease significantly with the addition of a few parts per hundred parts of resin of additives, and the change of the dominant deformation mechanism from ductile to brittle failure was recognized as a result of the change of the entanglement density of polycarbonate. Therefore, it was concluded that the presence of a small amount of ionomeric additives caused the loss of entanglement density that induced transition of the deformation mechanism of polycarbonate from ductile to brittle failure and led to the corresponding deterioration of impact strength. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2635–2643, 2001 相似文献