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861.
Gang‐Yin Shi Xue‐Zhi Tang Cai‐Yuan Pan 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2390-2401
The tadpole‐shaped amphiphilic copolymers with cyclic polystyrene as the head and a linear poly(N‐isopropylacrylamide) as the tail have been successfully synthesized by combination of reversible addition‐fragmentation chain transfer (RAFT) polymerization and “click” reaction. The synthesis involves two main steps: (1) preparation of a linear acetylene‐terminated PNIPAAM‐b‐PS with a side azido group anchored at the junction between two blocks; (2) intramolecular cyclization reaction to produce the cyclic PS block using “click” chemistry under high dilution. The structures, molecular weights, and molecular weight distributions of the resulted intermediates and the target polymers were characterized by their 1H NMR, FTIR, and gel permeation chromatography. The difference of surface property between tadpole‐shaped polymer and its linear precursor was observed, and the water contact angles on the former surface are larger than that of the latter surface. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2390–2401, 2008 相似文献
862.
In this paper, we derive non-exponential asymptotic forms for solutions of defective renewal equations. These include as special
cases asymptotics for compound geometric distribution and the convolution of a compound geometric distribution with a distribution
function. As applications of these results, we study the Gerber-Shiu discounted penalty function in the classical risk model
and the reliability of a two-unit cold standby system in reliability theory.
相似文献
863.
This paper is concerned with the large time behavior of solutions to two types of nonlinear diffusion equations with nonlinear boundary sources on the exterior domain of the unit ball. We are interested in the critical global exponent q0 and the critical Fujita exponent qc for the problems considered, and show that q0=qc for the multi-dimensional porous medium equation and non-Newtonian filtration equation with nonlinear boundary sources. This is quite different from the known results that q0<qc for the one-dimensional case. 相似文献
864.
This paper presents an experimental study of microscopic explosive boiling introduced by a pulsed laser. The violent explosive
boiling was observed in the liquid film, and the vapor bubbles together with liquid droplets were expelled from the platinum
film. It is found that the apparent bubble nucleation temperature is a strong function of the heating rate. The pressure signal
appears as continuous oscillation and is intensified as laser power density increases. 相似文献
865.
866.
867.
The multiple-objective resource allocation problem (MORAP) seeks for an allocation of resource to a number of activities such that a set of objectives are optimized simultaneously and the resource constraints are satisfied. MORAP has many applications, such as resource distribution, project budgeting, software testing, health care resource allocation, etc. This paper addresses the nonlinear MORAP with integer decision variable constraint. To guarantee that all the resource constraints are satisfied, we devise an adaptive-resource-bound technique to construct feasible solutions. The proposed method employs the particle swarm optimization (PSO) paradigm and presents a hybrid execution plan which embeds a hill-climbing heuristic into the PSO for expediting the convergence. To cope with the optimization problem with multiple objectives, we evaluate the candidate solutions based on dominance relationship and a score function. Experimental results manifest that the hybrid PSO derives solution sets which are very close to the exact Pareto sets. The proposed method also outperforms several representatives of the state-of-the-art algorithms on a simulation data set of the MORAP. 相似文献
868.
Tribromomethylarenes were prepared efficiently, at room temperature, from trifluoromethylarenes with boron tribromide as the
brominating reagent. The present process is applicable to the preparation of various substituted benzotribromide derivatives
from substituted benzotrifluoride compounds. p-Substituted benzotrifluoride compounds were found to be more reactive than o-substituted isomers under the given reaction conditions. 相似文献
869.
Gang‐Yin Shi Cai‐Yuan Pan 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2620-2630
A series of well‐defined θ‐shaped copolymers composed of polystyrene (PS) and poly(ε‐caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP), and the “click” chemistry. The synthetic process involves two steps: (1) synthesis of AB2 miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (α,α′‐diacetylene‐PCL) (ω‐azido‐PS)2, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB2 miktoarm star copolymers to produce well‐defined pure θ‐shaped copolymers using “click” chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta‐shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620–2630, 2009 相似文献
870.