Power of a Unit‐Root Test and the Initial Condition

Abstract. It is now well known that how the initial observation is generated can have a significant effect on the power of a unit‐root test. In this article, we show that by taking a simple data‐dependent weighted average of the initial condition‐robust test of Elliott and Müller [Journal of Econometrics (2006), forthcoming] and the standard augmented Dickey–Fuller test, we are able to produce a new unit‐root test that can improve power, both asymptotically and in finite samples, over a wide range of possibilities governing the generation of the initial observation.     

气液并流吸收过程中液相近界面浓度分布的全息干涉测量

1 INTRODUCTION Mass transfer across free interface of gas-liquid flow is of extensive importance and is encountered in most industrial applications. A close investigation of concentration distribution near the interface is helpful to understand mass transfer phenomena, to guide the development of transport theories, and to optimize the design of gas-liquid contact equipment. Laser holographic interference technique provides a precise and noncontact measurement method for measuring the tran…     

啮合型同向旋转双螺杆挤塑机熔体输送机理研究

本文提出了描述啮合型同向旋转双螺杆挤塑机中非等温三维熔体输送流场的理论模型。借助罚函数有限无及边界无法对该流场进行了求解。此后计算和分析了熔体输送段的重要工作特性参数。计算结果和实验结果的良好吻合证明所采用的模型合理、计算方法可行、计算结果可靠。     

Estimation in Random Coefficient Autoregressive Models

Abstract. We propose the quasi‐maximum likelihood method to estimate the parameters of an RCA(1) process, i.e. a random coefficient autoregressive time series of order 1. The strong consistency and the asymptotic normality of the estimators are derived under optimal conditions.     

Simulation of continuous solid‐phase polymerization of nylon 6,6. III. Simplified model

Solid‐phase polymerization (SPP) reactors are used to increase the degree of polymerization (DP) during nylon 6,6 production. In previous articles, a reactor model with partial differential equations (PDEs) in time and two spatial dimensions was developed to describe dynamic changes in polymer property profiles (DP, temperature, and moisture content) over the height of the reactor and within the polymer particles. In the current article, a simplified model is developed by deriving appropriate expressions for heat‐ and mass‐transfer coefficients and performing a lumped heat‐ and mass‐transfer analysis. Using this approach, the radial dimension is removed from the PDEs, so that the effort required to solve the model equations is substantially reduced. Predictions of the complex and simplified models are compared through simulation of two different start‐up processes. Good agreement between simplified and complex models is obtained, indicating that the simplified model can be used in place of the complex model if the polymer properties profiles within individual particles are not of particular concern to the model user. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3701–3712, 2003     

太阳能吸热功能膜材质

材质中电子能级和振转能级决定光谱的选择性。     

Preparation and characterization of new photoactive polyamides containing 4‐(4‐dimethylaminophenyl)urazole units

4‐(4‐dimethylaminophenyl)‐1,2,4‐triazolidine‐3,5‐dione ( DAPTD ) was prepared from 4‐dimethylaminobenzoic acid in five steps. The compound DAPTD was reacted with excess acetyl chloride in N,N‐dimethylacetamide (DMAc) solution and gave 1,2‐bisacetyl‐4‐[4‐(dimethylaminophenyl)]‐1,2,4‐triazolidine‐3,5‐dione as a model compound. Solution polycondensation reactions of monomer with succinyl chloride (SucC), suberoyl chloride (SubC), and sebacoyl chloride (SebC) were performed under conventional solution polymerization techniques in the presence of triethylamine and pyridine as a catalyst in N‐methylpyrrolidone (NMP) and led to the formation of novel aliphatic polyamides. These novel polyamides have inherent viscosities in the range of 0.09–0.21 dL/g in N,N‐dimethylformamide (DMF) at 25°C. Fluorimetric studies of the model compound as well as polymers were performed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 947–954, 2007     

A Semi‐Batch Process for Nitroxide Mediated Radical Polymerization

Summary: A semi‐batch process using nitroxide mediated polymerization, was explored for the design of low molecular weight solvent‐borne coatings, typical of those used in the automotive industry. While living radical polymerization (LRP) offers many advantages in the control of polymer chain microstructure that may confer important physical and chemical property benefits to coatings, adapting LRP to a semi‐batch process poses significant challenges in the design and operation of the process. Using styrene monomer, various two‐component initiating systems (free radical initiator, 4‐hydroxy‐TEMPO) were studied to understand the effects of different initiators on the course of polymerization. In addition, an alkoxyamine was synthesized and used as the initiating source. The initiators Luperox 7M75 and Luperox 231 give higher polymerization rates and reasonable control over polymerization, while benzoyl peroxide (BPO), Vazo 67, and the alkoxyamine are less effective. The number of polymer chains in the final product is always less than the theoretical value, reflecting poor initiation efficiency, probably resulting from undesirable termination reactions that become important due to the nature of the semi‐batch process. Adding camphorsulfonic acid (CSA) or charging initiator concurrently with monomer during semi‐batch feed, can increase the polymerization rate while maintaining the living character of the polymerization. The copolymerization of styrene and butyl acrylate is also shown to exhibit living character.

Schematic representation of the exchange reaction to produce N‐TEMPO capped polymer chains.     

β晶型成核剂改性聚丙烯纤维研究

研究了含 0 .2 5 %β晶型成核剂 (酰胺化合物 )的聚丙烯 Z3 0 S及其纤维的力学性能、晶型结构和微观形态。通过纺丝 -拉伸实验和力学性能测试、广角 X射线衍射分析、SEM观察 ,发现成核改性后生成了β晶型聚丙烯 (K值约为 75 .3 % ) ,抗冲性能大幅度提高。β晶型聚丙烯在纺丝卷绕过程中发生了β晶型→α晶型转变 ,纤维中产生约 10 %微孔隙 ,改性纤维的力学性能有所降低。