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排序方式: 共有284条查询结果,搜索用时 15 毫秒
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Vyacheslav V. Sentyurin Oleg A. Levitskiy Tatiana V. Magdesieva 《Current Opinion in Electrochemistry》2020
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications. 相似文献
3.
The Dantzig-Wolfe reformulation principle is presented based on the concept of generating sets. The use of generating sets allows for an easy extension to mixed integer programming. Moreover, it provides a unifying framework for viewing various column generation practices, such as relaxing or tightening the column generation subproblem and introducing stabilization techniques. 相似文献
4.
F. Blanchini 《Journal of Optimization Theory and Applications》1991,71(3):465-484
The linear state feedback synthesis problem for uncertain linear systems with state and control constraints is considered. We assume that the uncertainties are present in both the state and input matrices and they are bounded. The main goal is to find a linear control law assuring that both state and input constraints are fulfilled at each time. The problem is solved by confining the state within a compact and convex positively invariant set contained in the allowable state region.It is shown that, if the controls, the state, and the uncertainties are subject to linear inequality constraints and if a candidate compact and convex polyhedral set is assigned, a feedback matrix assuring that this region is positively invariant for the closed-loop system is found as a solution of a set of linear inequalities for both continuous and discrete time design problems.These results are extended to the case in which additive disturbances are present. The relationship between positive invariance and system stability is investigated and conditions for the existence of positively invariant regions of the polyhedral type are given.The author is grateful to Drs. Vito Cerone and Roberto Tempo for their comments. 相似文献
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The stabilization of polyolefins against γ-sterilization has been studied with single or binary additive system. The present attempt is to utilize synergistic mixtures of stabilizers which are approved for food contact applications. Ethylene-propylene (EP) copolymer has been melt-mixed with hindered amine stabilizers (HAS), phenolic antioxidants and organo-phosphites (hydroperoxide decomposer). Samples were sterilized with different doses of γ-radiation. Stabilization was characterized in terms of changes in the functional groups (oxidation products), tensile properties, yellowing and surface morphology by FTIR spectroscopy, Instron, colorimetry (reflectance) and scanning electron microscopy (SEM), respectively. Results were discussed by comparing the stabilizing efficiency of mixtures with and without phenol system. Among phenol containing systems, where we mostly observe discoloration due to the oxidation of hindered phenol and the combination of secondary HAS, tertiary HAS, organo-phosphite and hindered phenol exhibited improved stabilization efficiency than single or binary additive systems. The mixture of secondary HAS and tertiary HAS, has shown antagonistic effect of stabilization whereas their combination with organo-phosphite has exhibited synergistic effect of stabilization even at higher doses of γ-sterilization. The effects have been explained through the interaction between the stabilizers. 相似文献
7.
A review of heat treatment on polyacrylonitrile fiber 总被引:3,自引:0,他引:3
Developing carbon fiber from polyacrylonitrile (PAN) based fiber is generally subjected to three processes namely stabilization, carbonization, and graphitization under controlled conditions. The PAN fiber is first stretched and simultaneously oxidized in a temperature range of 200-300 °C. This treatment converts thermoplastic PAN to a non-plastic cyclic or a ladder compound. After oxidation, the fibers are carbonized at about 1000 °C in inert atmosphere which is usually nitrogen. Then, in order to improve the ordering and orientation of the crystallites in the direction of the fiber axis, the fiber must be heated at about 1500-3000 °C until the polymer contains 92-100%. High temperature process generally leads to higher modulus fibers which expel impurities in the chain as volatile by-products. During heating treatment, the fiber shrinks in diameter, builds the structure into a large structure and upgrades the strength by removing the initial nitrogen content of PAN precursor and the timing of nitrogen. With better-controlled condition, the strength of the fiber can achieve up to 400 GPa after this pyrolysis process. 相似文献
8.
本文中用紫外光敏化的方法对低密度聚乙烯进行了交联,并利用ESCA和ATR-IR等手段研究了交联后材抖的光稳定性及其改进办法。 相似文献
9.
Joseph C. P. Koo Janice S. W. Lam Gregory A. Chass Ladislaus L. Torday Andras Varro Julius Gy. Papp 《Journal of Molecular Structure》2003,620(2-3):231-255
The sidechain conformational potential energy hypersurfaces (PEHS) for the γL, βL, αL, and αD backbone conformations of N-acetyl-
-aspartate-N′-methylamide were generated. Of the 81 possible conformers initially expected for the aspartate residue, only seven were found after geometric optimizations at the B3LYP/6-31G(d) level of theory. No stable conformers could be located in the δL, L, γD, δD, and D backbone conformations. The ‘adiabatic’ deprotonation energies for the endo and exo forms of N-acetyl-
-aspartic acid-N′-methylamide were calculated by comparing their optimized relative energies against those found for the seven stable conformers of N-acetyl-
-aspartate-N′-methylamide. Sidechain conformational PEHSs were also generated for the estimation of ‘vertical’ deprotonation energies for both endo and exo forms of N-acetyl-
-aspartic acid-N′-methylamide. All backbone–sidechain (N–H−O–C) and backbone–backbone (N–HO=C) hydrogen bond interactions were analyzed. A total of two backbone–backbone and four backbone–sidechain interactions were found for N-acetyl-
-aspartate-N′-methylamide. The deprotonated sidechain of N-acetyl-
-aspartate-N′-methylamide may allow the aspartyl residue to form strong hydrogen bond interactions (since it is negatively charged) which may be significant in such processes as protein–ligand recognition and ligand binding. As a primary example, the molecular geometry of the aspartyl residue may be important in peptide folding, such as that in the RGD tripeptide. 相似文献
10.
In the present study, the recyclability of the post-use milk pouches (50/50 LDPE–LLDPE blend) was evaluated with or without adding stabilizer. Thoroughly washed and dried post-use milk pouch films were extruded five times at high temperature (483–513 K) in the open atmosphere. The mode of degradation during extrusion operation was studied by melt flow index (MFI), rheological properties, gel content and FT-IR analysis. The differential scanning calorimetry (DSC) analysis was carried out to evaluate the thermal stability of the stabilized and un-stabilized recycled mass from post-use milk pouch under this investigation. Mechanical properties (tensile strength, % elongation at break, tensile modulus and hardness) of the un-stabilized extruded material were significantly affected as a result of thermooxidative degradation during extrusion in presence of air. After all, stabilization with 0.4% anti-oxidant satisfactorily retains all the initial properties of the recycled material. 相似文献