Transient-thermal and isothermal studies of thermo-sensitive polymer solution with ultrasound resonator technology

High resolution and high sensitivity ultrasound resonator technology offers unique possibilities for the investigation of polymer precipitation. Exemplarily, the aggregation of poly(N-isopropylacrylamide) units in block copolymers with poly(styrene sulfonate) is investigated. Long term changes, over hours and days, of both the ultrasound velocity and the attenuation were detected during isothermal studies at temperatures in the vicinity (below as well as above) of the critical solution temperature. Apparent activation free energies of the precipitation and re-dissolution of the poly(N-isopropylacrylamide) block have been determined for the first time. The apparent activation energies are in the order of up to a few thousands kJ/mol, which can be explained by a high cooperativity of the precipitation process.     

Solutions approximatives pour l'absorption dans un solide poreux

The adsorption of a solute by porous solid particles can be represented with good accuracy by a simple approximate formula of the “penetration” type. The corresponding “kinetic” model makes use of average lumped concentrations of the two phases. It can be applied, by introduction of the fluid—solid slip velocity, either to the agitated vessel, or to the co- or counter-current moving bed. With the external specific area of the particle sample, the formula also represents correctly the, absorption by particles of any shape and any size distribution.     

An effectiveness trial of a dissonance-based eating disorder prevention program for high-risk adolescent girls.

Efficacy trials indicate that an eating disorder prevention program involving dissonance-inducing activities that decrease thin-ideal internalization reduces risk for current and future eating pathology, yet it is unclear whether this program produces effects under real-world conditions. The present effectiveness trial tested whether this program produced effects when school staff recruit participants and deliver the intervention. Adolescent girls with body image concerns (N = 306; M age = 15.7, SD = 1.1) randomized to the dissonance intervention showed significantly greater decreases in thin-ideal internalization, body dissatisfaction, dieting attempts, and eating disorder symptoms from pretest to posttest than did those assigned to a psychoeducational brochure control condition, with the effects for body dissatisfaction, dieting, and eating disorder symptoms persisting through 1-year follow-up. Effects were slightly smaller than those observed in a prior efficacy trial, suggesting that this program is effective under real-world conditions, but that facilitator selection, training, and supervision could be improved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new model for springback prediction in which the Bauschinger effect is considered

Springback prediction is an important issue for the sheet metal forming industry. Most sheet metal elements undergo a complicated cyclical deformation history during the forming process. For an accurate prediction of springback, the Bauschinger effect must be considered to determine accurately the internal stress distribution within the sheet metal after deformation. Based on the foundations for isotropic hardening and kinematic hardening, Mroz multiple surface model, plane strain assumptions, and experimental observations, a new incremental method and hardening model is proposed in this paper. This new model compares well with the experimental results for aluminum sheet metal undergoing multiple-bending processes. As is well known, aluminum is one of the most difficult sheet metals to simulate. The new hardening model proposed in this paper is not only a generic model for springback prediction but also a hardening model for sheet metal forming process simulation.     

Optimal short‐term scheduling of shunt compensators via a decomposition algorithm

Abstract

The short term (one day) scheduling of VAr controllers involves the setting of shunt compensators, EHV taps and generator voltages. A decomposition approach is presented to solve the problem of optimal short‐term scheduling of shunt compensators in this paper. The entire problem is decomposed into two levels: the master and the slave levels. The master level deals with minimization of the depreciation cost of compensators in order to reduce the control actions for compensators while satisfying operating constraints. The slave level treats minimization of capitalized MW losses while satisfying system security constraints by adjusting generator voltages and taps. These two levels interact through linear constraints in the iteration process. The IEEE 30‐bus and a practical 265‐bus systems, namely Taiwan Power System, are used to serve as samples to show the applicability of the presented approach.     

Extremely Efficient Cross‐Coupling of Benzylic Halides with Aryltitanium Tris(isopropoxide) Catalyzed by Low Loadings of a Simple Palladium(II) Acetate/Tris(p‐tolyl)phosphine System

Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O‐i‐Pr)₃] catalyzed by a simple palladium(II) acetate/tris(p‐tolyl)phosphine [Pd(OAc)₂/ P(p‐tolyl)₃] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2 mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electron‐withdrawing cyano (CN) or trifluoromethyl (CF₃) substituents, the reactions require a higher catalyst loading of 1 mol%, or the reactions are carried out at 60 °C. The catalytic system also tolerates (1‐bromoethyl)benzene bearing β‐hydrogen atoms while using a catalyst loading of 1 mol% to afford the coupling product in a 70% yield.     

Selection of an optimal set of cutting-tool sizes for 21/2D pocket machining

The availability of high speed automatic tool change mechanisms in modem CNC machining centers is making it practical to consider the use of multiple cutting-tool (specifically, flat end-mill) sizes to reduce the total time for machining a 21/2D) pocket. However, current CAD/CAM systems do not support pocket machining using multiple cutting-tool sizes. In this paper, we describe a two-phase methodology for selecting an optimal set of cutting-tool sizes to machine a 21/2D pocket. In the first phase, we employ a new concept called the Voronoi mountain in order to calculate the material volume that can be removed by a specific cutting-tool size, the material volume that will subsequently remain to be machined, and the cutter-paths (and corresponding processing times) for each cutting-tool. In the second phase, we apply a dynamic programming approach for optimal selection of cutting-tool sizes on the basis of the processing time. Our computational experiments indicate that substantial savings in processing time can be achieved by using multiple cutting-tool sizes to machine 21/2D pockets.     

GSM数字移动通信系统的越区切换

切换技术是GSM数字移动通信系统保证移动中用户通信质量的一个重要手段。本文简要说明切换及其起因、启动标准和类型 ,并阐述基站决定切换启动的三个不同阶段的算法和要求 ,最后重点介绍网络系统中各种不同范围切换控制的信令关系及其实现过程。     

CORIS®: Literatur-Datenbank

CORIS™: Literature database The literature database integrated in the CORIS system supports the user with additional information. It includes about 70 000 abstracts which come from the DECHEMA e.V., NACE and METADEX. The DECHEMA Corrosion Thesaurus is also implemented in German and English. The user can initiate a full text search as well as a field specific search. A data input form (mask) is programmed for the user's own data implementation.