ON THE ROBUST GLOBAL STABILIZATION OF nth-ORDER REACTIONS

In this paper, we employ a nonlinear adaptive mechanism to globally stabilize n^th-order reactions.     

Flow stress of high density polyethylene and nylon 66 at high rates of strain

Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 10³ s^?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 10³s^?1.     

Effects of Working Fluid,Tubeside Enhancement and Bundle Depth on the Optimized Fin Geometry of a Horizontal Condenser Tube

A theoretical study has been made to optimize the fin geometry of a horizontal finned tube which is to be usedfor condensers that handle the vapor load of a liquid phase change cooling module.Systematic numerical calcu-lations of the vapor to coolant heat transfer have been performed for parametric values of fin height,fin spacing,vertical bundle depth and tubeside heat transfer coefficient.Three dielectric fluids (R-113,FC-72,and FC-87)at atmospheric pressure were selected as the working fluids.For a single tube with optimized fin geometry,theaverage heat flux increased in the order of FC-87,R-113 and FC-72.Both the optimum fin height and optimumfin spacing increased with increasing vertical bundle depth.     

A Model for Flooding Prediction in Circular Tubes

Flooding phenomenon limits the stability and the flow of a liquid film falling along the walls of a channel in which a gas is flowing upwards.As known, the entrainment effect can completely prevent the liquid to fall from its natural flow. The present work proposes a new mechanistic model for the prediction of the onset of flooding in vertical and inclined pipes in the presence of obstructions, as well as taking into account the viscosity effect. The good performance of the model in the different geometrical conditions and for variable viscosities of the liquid component assesses the validity of the hypothesis that the instability of a wavelike disturbance limits the countercurrent flow in a channel.     

Adhesive Dispensing Process Analysis: Steady-State Dispensing of One-Component Adhesives

The process of dispensing one-component heat-cure adhesives was investigated in order to understand current application processes and to guide new process development. Typical one-component adhesives exhibit non-Newtonian rheological behavior, and hence Newtonian fluid mechanics does not adequately describe the dispensing process. In the present study, the adhesives were modeled as Bingham fluids possessing a yield stress and a steady state viscosity. The model of the dispensing apparatus includes four major flow sections connected in a serial configuration. The fluid mechanics equations derived for Bingham fluids in the individual flow sections were solved by numerical methods in order to understand the interrelationships between the material variables (e.g. yield stress, viscosity, temperature dependencies) and process variables (e.g. pressure, flow geometry, temperature, output). The concept of the model is generic and the details of the model can be modified for any forced-flow adhesive application process.

The adhesive flow properties significantly influence the process output. Dispensing temperature, among the process variables, has the strongest effect on process output. A ± 1.0·C perturbation in the dispensing temperature can cause as much as a 14% variation in the bead size for the range of adhesives studied. Differences in flow characteristics result in differences in processability and non-linear temperature/pressure sensitivity. The non-linear sensitivity can be eliminated by operating the dispensing process isothermally. Finally, the process limits for one-component adhesives, which are susceptible to chemical instability induced by viscous heating during processing, are defined and discussed in terms of a modified Brinkman number that takes into account viscous dissipation, heat conduction and convection, and chemical stability of the material during processing.     

锥形凸台成形的一种叠加滑移线场力学模型

分析了锥形凸台在不同体积成形工艺中的成形机理，基于模块化思想将锥形凸台的成形过程划分为挤压成形与角部充满两个特征时段；将上述两个特征时段的滑移线场力学模型有机联结，构建了锥形凸台成形过程的一种叠加滑移线场力学模型；介绍了叠加滑移线场力学模型的应力场与变形力的求解方法。该模型丰富了金属体积成形过程的特征单元库，可套用于局部成形的应力场与变形力求解，实现局部成形的模具优化设计。     

轮式工程机械轮边减速器优化模型与方法

论述了重构轮式工程机械轮边减速器优化设计数学模型的必要性,给出了精确化的目标函数,全面化和准确化的设计变量、基于并行设计的约束条件;介绍了对优化解适用性评价的方法和手段。巧妙地解决了优化解中离散变量的圆整问题,提供了基于MATLAB的求解反渐开线函数的M文件。     

钢纤维聚合物混凝土抗压本构关系

钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料，它的力学行为不仅依赖于聚合物混凝土基体的行为，而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关，本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。     

A novel direct aerodynamically assisted threading methodology for generating biologically viable microthreads encapsulating living primary cells

In a recent discovery, coaxial electrospinning was explored to encapsulate living organisms within a continuous bio‐polymeric microthread from which active biological scaffolds were fabricated (Townsend‐Nicholson and Jayasinghe, Biomacromolecules 2006, 7, 3364). The cells were demonstrated to have gone through all expected cellular activity without their viability being compromised. These biologically active threads and scaffolds have direct and tremendous applicability from regenerative to therapeutic medicine. Currently these post‐processed cells as composite threads and scaffolds are being investigated in‐depth at a cellular level to establish if the processing methodology has any affect on the cellular make‐up. We now demonstrate a competing non‐electric field driven approach for fabricating composite threads and scaffolds influenced only by a differential pressure. We refer to this novel composite thread to scaffold fabrication methodology as coaxial aerodynamically assisted bio‐threading (CAABT). Our investigations firstly, demonstrate that this technique can process handle living organisms without biologically perturbing them in anyway. Secondly the process is elucidated as possessing the ability to form composite active threads from which biologically viable scaffolds are formed. Finally our study employs florescent activated cell sorting (FACScan), a method by which the cellular dynamics and viability are quantified on control and threaded cellular samples at two prescribed time points. In parallel with FACScan, optical comparison of cellular morphology at three time points within a period of three weeks is carried out to photographically observe any changes in the post‐processed cellular phenotype. Our developmental investigations into this novel aerodynamically assisted threading methodology has unearthed a unique biomicrofabrication approach, which joins cell electrospinning in the cell threading to scaffold fabrication endeavor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008