溶液共混法制备高强度淀粉基完全生物降解塑料薄膜

利用一步溶液共混法，将预糊化的淀粉糊与PvA溶液共混，用乙二醛进行交联，制备淀粉／聚乙烯醇（PVA）完全生物降解塑料薄膜。研究不同乙二醛和甘油的用量对薄膜性能的影响。薄膜的力学性能、热性能和微观形态表征表明，淀粉／PvA体系具有较好的相容性和较高的力学性能，薄膜的拉伸强度和断裂伸长率分别可达到28．52MPa和307．5％。     

Effect of styrene–isopren–styrene addition on the recycled polycarbonate/acrylonitrile–butadiene–styrene polymer blends

Interfacial agents as compatibilizers have recently been introduced into polymer blends to improve microstructure and mechanical properties of thermoplastics. In this way, it is possible to prepare a mixture of polymeric materials that can have superior mechanical properties over a wide temperature range. In this study, an incompatible blend of Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) Copolymer were made compatible by addition of 5, 10, and 20% Styrene–Isopren–Styrene Copolymer (SIS). The mixing operation was conducted using a twin‐screw extruder. The morphology and the compatibility of the mixtures were examined by SEM and DSC techniques. Furthermore, the elastic modulus, tensile and yield strengths, percentage elongation, hardness, melt flow index, Izod impact resistance, heat deflection temperature (HDT), Vicat softening point values of polymer alloys of various ratios were determined. It was found that addition of SIS to the structures decreased the tensile strength, yield strength, elastic modulus, and hardness, whereas it increased Izod impact strength and percentage elongation values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 559–566, 2006     

Straightforward modeling of dynamic I–V characteristics for microwave FETs

This work presents a straightforward approach aimed at modeling the dynamic I–V characteristics of microwave active solid‐state devices. The drain‐source current generator represents the most significant source of nonlinearity in a transistor and, therefore, its correct modeling is fundamental to predict accurately the current and voltage waveforms under large‐signal operation. The proposed approach relies on using a small set of low‐frequency time‐domain waveform measurements combined with numerical optimization‐based estimation of the nonlinear model parameters. The procedure is applied to a gallium nitride HEMT and silicon FinFET. The effectiveness of the modeling procedure in terms of prediction accuracy and generalization capability is demonstrated by validation of the extracted models under operating conditions different than the ones used for the parameters estimation. Good agreement between measurements and model simulations is achieved for both technologies and in both low‐ and high‐frequency range. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:109–116, 2014.     

UNIT ROOTS IN PERIODIC AUTOREGRESSIONS

Abstract. This paper analyzes the presence and consequences of a unit root in periodic autoregressive models for univariate quarterly time series. First, we consider various representations of such models, including a new parametrization which facilitates imposing a unit root restriction. Next, we propose a class of likelihood ratio tests for a unit root, and we derive their asymptotic null distributions. Likelihood ratio tests for periodic parameter variation are also proposed. Finally, we analyze the impact on unit root inference of misspecifying a periodic process by a constant-parameter model.     

Blends of i‐PP and SBS. I. Influence of the in situ compatibilization on the morphology

This article concerns the in situ compatibilization of immiscible isotactic polypropylene/butadiene‐styrene‐butadiene triblock copolymer blends (i‐PP/SBS) by means of a reactive mixture. For this purpose, maleated PP (PP‐MAH) and SBS (SBS‐MAH) were used as functionalized polymers and 4,4′‐diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends i‐PP/SBS, nonreactive ternary blends i‐PP/PP‐MAH/SBS, and reactive ternary blends i‐PP/PP‐MAH/SBS‐MAH with varying diamine and anhydride molar ratios were prepared. Torque measurements suggest a graft copolymerization during the melt blending for ternary reactive blends, but the extension of the grafting does not vary with the diamine and anhydride molar ratio, but with the elastomer concentration. The morphology of the blends was investigated by scanning electron microscopy. The morphology of binary and ternary nonreactive blends is similar, exhibiting elastomer domains disperse in the i‐PP matrix, whose sizes increase with elastomer concentration. On the other hand, the elastomer domain size in the ternary reactive blends is practically independent of the blends composition and of the diamine and anhydride molar ratio. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 847–855, 2002     

A DISTANCE MEASURE FOR CLASSIFYING ARIMA MODELS

Abstract. In a number of practical problems where clustering or choosing from a set of dynamic structures is needed, the introduction of a distance between the data is an early step in the application of multivariate statistical methods. In this paper a parametric approach is proposed in order to introduce a well-defined metric on the class of autoregressive integrated moving-average (ARIMA) invertible models as the Euclidean distance between their autoregressive expansions. Two case studies for clustering economic time series and for assessing the consistency of seasonal adjustment procedures are discussed. Finally, some related proposals are surveyed and some suggestions for further research are made.     

无患子表面活性物及其复配体系的性质研究

对天然植物原料无患子提取物中的表面活性物的性质（临界胶束浓度、表面张力和起泡性能）及其影响因素（温度、pH、水硬度和盐度等）进行了系统的研究，结果表明无患子表面活性物具有很低的cmc和γcmc，且在一定范围内受一些因素的影响也不大，是一种理想的香波原料；同时也研究了无患子活性物与其他温和型的阴离子表面活性剂的复配体系，表明具有明显的协同增效效果。