The crack propagation for a cohesive zone model within an elastic-plastic material under small-scale yielding conditions is simulated numerically. The resulting crack growth resistance curves show local instabilities, so-called pop-ins even for homogeneous cohesive properties if the cohesive strength lies sufficiently close to the maximum stress of the corresponding blunting solution. The formation of secondary cracks and unloading zones in front of the actual crack tip is identified as the underlying mechanism. It is found that the shape of the cohesive law has a considerable influence on the crack arrest behavior. Furthermore, requirements to the mesh resolution are derived. 相似文献
Self-assembly of a ferrocene-appended polymer bearing an antigen fragment and lactate oxidase on a cyclodextrin-modified surface provides a highly sensitive, easy-to-operate and self-sufficient immunosensor. 相似文献
The zinc(II) and cadmium(II) 2,4-dichlorophenoxyacetate salts were synthesized in mixed water–methanol environment and characterized
by elemental analysis, IR spectrometry and thermal analysis coupled with mass spectrometry. The crystal structures were determined
by X-ray crystallography (compound 1, [C18H18Cl4O8Zn]n: monoclinic, P21/c, a = 19.094, b = 7.378, c = 8.008, α = 90.00, β = 101.134, γ = 90.00, V = 1106.95; compound 2, [C16H14Cl4O8Cd]n: monoclinic, P21/c, a = 17.730, b = 7.293, c = 8.060, α = 90.00, β = 95.18, γ = 90.00, V = 1037.9). The structural and some thermal data about the presented cadmium salt were previously reported (Song et al. Acta
Crystallogr E 62:m2397, 2006; Kobylecka et al. Thermochim Acta 482:49, 2009). 相似文献
Selected C-H acids react with difluorocarbene generated from chlorodifluoromethane with concentrated aqueous solution of sodium hydroxide, and a catalyst, benzyltriethylammonium chloride (TEBAC) in benzene or THF affording C-difluoromethyl substituted derivatives. This process is restricted to C-H acids of pKa ≅ 16.3-19.1. The observed facts are rationalized. 相似文献
Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay.
Journal of Thermal Analysis and Calorimetry - An use of a polymerization lamp to irradiate chemically hardened glass-ionomer materials may improve their properties and accelerate the setting time.... 相似文献
Two new methods for the synthesis of orthoesters and compounds containing an orthoester moiety (dihydroisoxazoles) are presented. Mixed orthoesters of general formulas RC(OR1)(OR2)2 and RC(OR1)(OR2)(OR3) were prepared via addition of ROH (R = Bu or m-methylphenyl) to O-allyl acetals (acrolein acetals: diethyl or cyclic, i.e., 2-vinyl-1,3-dioxanes or dioxolanes). The catalytic systems for these reactions were generated from [RuCl2(PPh3)3] and Na2CO3; {[RuCl2(COD)]x} or {[OsCl2(1,5-COD)]x}, PPh3, and Na2CO3. Compounds containing an orthoester moiety (dihydroisoxazoles) were prepared via tandem isomerization of O-allyl acetals (to O-vinyl acetals) catalyzed by ruthenium complexes followed by cycloaddition to in situ-generated 2,6-dichlorophenylnitrile oxide. 相似文献