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51.
Summary The synthesis of telechelic monodispersed diols produced from the radical telomerization of an excess of undecylenol with commercialy available , -dithiols HSC2H4XC2H4SH (X=0, S or CH2) initiated by peroxides is presented. In each case, the diols were obtained selectively and quantitatively and they were characterized by both 1H and 13C NMR. Their physical characteristics (Tg, Tm and decomposition temperatures) were determined. Such compounds are thermally more stable than polydispersed telechelic commercially available diols. 相似文献
52.
Jean-Pierre Montheard Bernard Boinon Ahmed Belfkira Abderahim Sadel Quang-Tho Pham 《Polymer Bulletin》1992,28(6):615-620
Summary Vinylidene cyanide has been copolymerized in solution by radical reaction with equal initial mole fraction of para substituted acetoxystyrenes. The copolymers have been characterized by means of DSC, TGA and GPC. These products are stable up to 220° and have no visible glass transition temperature. The microstructure of these new copolymers has been studied by 13CNMR; they have an alternating structure and monomers units are arranged in head-to-tail placements. 相似文献
53.
The purpose of this paper is to evaluate theoretically and experimentally the transient electric field in anemp simulator. Using a time domain analysis, the mechanism of the field deformation can be analysed and consequently modifications can be introduced in the conception of new simulators (for example: rhombic simulator). 相似文献
54.
55.
Adya P. Singh Anni Ratz Bernard S. W. Dawson 《Journal of Coatings Technology and Research》2007,4(2):207-210
A new method was developed which enabled us to obtain high-resolution images of the distribution of an oil-borne stain in
a saw-textured plywood surface. The method involved treating 90 μm thick plywood sections, which had been cut transversely
through the wood-coating interface using a sliding microtome, with osmium tetroxide (OsO4) prior to examination with a field-emission scanning electron microscope (FE-SEM) operating in backscattered electron imaging
(BEI) mode. The combination of OsO4 staining and use of FE-SEM-BEI afforded excellent contrast differentiation between the coating and wood cell walls, revealing
coating penetration into even nano-size cell wall cracks and delaminations formed during band-sawing of the plywood. The novel
technique described adds a new dimension to probing wood–coating interface. 相似文献
56.
Michel Renou Bernard Lalanne-Cassou Didier Michelot Ginette Gordon Jean-Christophe Doré 《Journal of chemical ecology》1988,14(4):1187-1215
Female-emitted pheromones and sex attractants of Noctuidae were investigated using a specific computer procedure to analyze data collected from the literature. Correspondence analysis was used to survey the structure-activity relationships of sex pheromones in seven subfamilies. Structural, stereochemical, and functional features of active molecules were related to taxonomy. This multidimensional analysis revealed that the prevalent chemical frame of noctuid moth pheromones was a monounsaturated acetate withZ stereochemistry and a double bond on the fifth carbon closest to the nonfunctional branch of the molecule. Possible phylogenetic relationships within Noctuidae and between Noctuidae and other families are discussed in light of the sex pheromone biochemistry. Female sex pheromones appeared to be an additional character to be considered in the classification of noctuid moths. 相似文献
57.
Complex Phase Equilibria in Refractories Design and Use 总被引:2,自引:0,他引:2
William E. Lee Bernard B. Argent Shaowei Zhang 《Journal of the American Ceramic Society》2002,85(12):2911-2918
The current applications of phase diagrams and thermodynamic calculations to studies of refractories are reviewed highlighting links to microstructural analyses. Improved understanding of microstructural evolution and chemical corrosion mechanisms has resulted from such work. The limitation of the calculations/diagrams to thermodynamic equilibria has led to imaginative attempts to incorporate some dynamic aspect in them so they are more relevant to practical conditions. These include varying temperature to model a temperature gradient, P O2 to model atmosphere permeation into a brick, slag/refractory ratio to model slag penetration and altering the slag composition after reaction with the fine matrix phases. The potential future development of such techniques is discussed. 相似文献
58.
Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic,
myristic, and oleic groups. Synthesis yields were 15–20% based on initial maltose present, and structural confirmation was
obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface
tensions in the range of 34–36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10−5–10−6 mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude
over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change
in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C,
and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their
applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these
surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable,
economical carbohydrates and lipids and may provide an excellent alternative to pertrochemical-derived products. 相似文献
59.
The electrochemical behaviour of polysulphur nitride was studied by cyclic voltametry in alkaline and silver salt acetonitrile solutions. In an alkaline salt solution during the cathodic polarization, superficial degradation of (SN)x probably gives S7N? ions. In a silver perchlorate solution silver deposition was observed. It can be dissolved anodically. During the first anodic polarization, oxidation pic occurs. The quantity of electricity involved during this reaction is a function of the association constant of the electrolyte. 相似文献
60.
We address the problem of adaptive output-feedback stabilization of general first-order hyperbolic partial integro-differential equations (PIDE). Such systems are also referred to as PDEs with non-local (in space) terms. We apply control at one boundary, take measurements on the other boundary, and allow the system’s functional coefficients to be unknown. To deal with the absence of both full-state measurement and parameter knowledge, we introduce a pre-transformation (which happens to be based on backstepping) of the system into an observer canonical form. In that form, the problem of adaptive observer design becomes tractable. Both the parameter estimator and the control law employ only the input and output signals (and their histories over one unit of time). Prior to presenting the adaptive design, we present the non-adaptive/baseline controller, which is novel in its own right and facilitates the understanding of the more complex, adaptive system. The parameter estimator is of the gradient type, based on a parametric model in the form of an integral equation relating delayed values of the input and output. For the closed-loop system we establish boundedness of all signals, pointwise in space and time, and convergence of the PDE state to zero pointwise in space. We illustrate our result with a simulation. 相似文献