Preparation of new poly(amide–imide)s with chiral architectures via direct polyamidation reaction

N‐trimellitylimido‐L ‐methionine ( 3 ) was prepared by reaction of trimellitic anhydride ( 1 ) with ‐L ‐methionine ( 2 ) in acetic acid solution at refluxing temperature. This diacid was reacted with thionyl chloride, and N‐trimellitylimido‐L ‐methionine diacid chloride ( 4 ) was obtained in quantitative yield. The resulting diacid chloride was reacted with p‐aminobenzoic acid in dry acetone and bis(p‐aminobenzoic acid)‐N‐trimellitylimido‐L ‐methionine ( 5 ) was obtained as a novel optically active amide–imide diacid monomer in high yield. The direct polycondensation of amide–imide diacid monomer 5 with several aromatic diamines was carried out with tosyl chloride (TsCl)/pyridine (Py)/dimetheylformamide (DMF) system. The resulting thermally stable poly(amide–imide)s (PAIs) were obtained in good yields and inherent viscosities ranging between 0.24 and 0.46 dL g^?1 and were characterized with FTIR, ¹H NMR, CHN, and TGA techniques. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1248–1254, 2007     

Shear Strength of Pressure Sensitive Adhesives and its Correlation to Mechanical Properties

Correlations between shear resistance and the mechanical properties of pressure sensitive adhesives are studied by measuring the deformation behaviour in the static and the dynamic shear test and determining the dynamic shear modulus of the adhesive. For polymers with low or moderate viscosities, the shear strain vs. time characteristics in a static shear test and, accordingly, the static shear strength, can be evaluated from the master curves of the dynamic shear modulus or the dynamic viscosity. The dynamic shear strength also can be calculated. These exact calculations cannot be applied to highly viscous or slightly crosslinked polymers. On the basis of the model experiments, empirical correlations between shear strength and the dynamic shear modulus are established which seem to be generally valid.     

稀疏卷积非负矩阵分解的语音增强算法

非平稳噪声和低信噪比条件下提高增强语音质量一直以来都是语音增强研究的难题。近年来,卷积非负矩阵分解在语音增强算法中成功应用,本文进一步考虑语音信号在时频域的稀疏性,提出了稀疏卷积非负矩阵分解(Sparse Convolutive Nonnegative Matrix Factorization, SCNMF)的语音增强算法。该算法包括训练和增强两个阶段。训练阶段通过SCNMF算法分别对纯净语音和噪声的频谱进行训练,得到纯净语音和噪声字典,并将其作为增强阶段的先验信息。增强阶段首先通过SCNMF算法对带噪语音的频谱进行分解,然后利用纯净语音和噪声联合字典对语音编码矩阵进行估计,重构增强语音。本文通过实验仿真分析了稀疏因子对增强语音质量的影响。实验结果表明,在非平稳噪声和低信噪比条件下,本文算法增强效果均优于多带谱减、非负矩阵分解、卷积非负矩阵分解等传统的算法。     

基于四元数和增广矩阵束的MIMO雷达角度估计算法

通过研究多输入多输出（Multiple input and multiple out, MIMO）雷达的角度估计算法,基于收发共址的十字阵MIMO雷达系统,将四元数理论应用到 MIMO雷达角度中,提出了一种新的参数估计算法。通过构造四元数模型,结合增广矩阵束（ Matrix enhancement and matrix pencil, MEMP）方法构造增广矩阵,并证明该矩阵的秩 等于目标总数,且不受目标相干性的影响,结合ESPRIT算法实现了对MIMO相干目标的角度估 计。算法无需谱峰搜索,能够实现参数的自动配对,同时降低了运算复杂度。仿真实验进一 步验证了算法的有效性。     

高档水基油墨粘度影响因素的研究

为获得高固低粘的油墨配方体系,通过油墨的分散实验,探讨了分散树脂和乳液及其助剂对水基油墨体系粘度的影响规律,润湿分散剂对水基油墨粘度的影响,胺化剂对水基油墨粘度的影响机理。研究表明,乳液聚合物具有高固低粘特性,拼混使用不同的聚合物可获得理想粘度和应用性能;润湿分散剂能改变体系的表面张力和润湿性能,从而降低水基油墨体系的粘度;拼混使用不同的胺化剂可以获得粘度稳定的水基油墨体系。     

Viscosity of Porous Glasses

Viscosity of porous glasses has been derived from the elastic stress analysis, using the viscous analogy. Viscosity as a function of porosity has been estimated for spherical as well as for arbitrary pore geometry. Since the pore geometry changes during sintering, a shape factor that varies with pore geometry has been considered to predict the viscosity–porosity relationship. Viscosity as a function of porosity was measured on cordierite-type glass by isothermal sinter-forging experiments and data showed good agreement with the analysis. Experimental data from literature on viscosity as a function of porosity on two other glasses also show good agreement with the analysis.     

吐温—20增稳浊度法快速测定水泥中三氧化硫

本文研究了一种以非离子表面活性剂吐温－20为介质，硫酸钡浊度法侧定水泥中三氧化硫的新方法。吐温-20的引入使硫酸钡颗粒分散均匀，体系稳定性提高。本文选420nm为测定波长，SO2-4含量在50～500μg／25ml范围内线性关系良好，可很好地适用于水泥样品的分析。     

Synthesis of tetramethyl-p-silphenylenesiloxanedimethylsiloxane triblock copolymer by employing living anionic polymerization

Dimethylsiloxane-tetramethyl-p-silphenylenesiloxane-dimethylsiloxane (DMS-TMPS-DMS) triblock copolymer was synthesized by employing living anionic polymerization of hexamethylcyclotrisiloxane (D₃). Two synthetic methods were carried out for the polymerization. One of those methods was the anionic polymerization of D₃ initiated at the silanolate anion which was prepared from the terminal hydroxyl group of silanol-terminated TMPS prepolymer by reaction with n-butyllithium (method 1). The other was the coupling reaction of vinyl-terminated TMPS prepolymer with hydrosilyl-terminated DMS prepolymer obtained from the anionic polymerization of D₃ by using diphenylmethylsilanolate anion as initiator (method 2). In method 1, DMS contents of the copolymers ranged from 25.8 to 72.5 wt% and the values agreed with the ratio of D₃ to TMPS prepolymer. The weight-average molecular weights ranged from 1.36×10⁴ to 19.4×10⁴ and were close to the predicted values calculated from the $\text{M}\text{?}{}_{\mathrm{v}}$ of the TMPS prepolymer and the amount of D₃ added. In the case of method 2, weight-average molecular weights ranged from 19.5×10⁴ to 24.2×10⁴. The high molecular weight copolymer could thus be obtained by method 2. Intrinsic viscosity values of the triblock copolymers agreed with calculated values obtained by considering the copolymer as a binary mixture of these homopolymers. Differential scanning calorimetry and thermogravimetry were carried out on the triblock copolymers. The equilibrium melting temperatures of each of the copolymers were very close to that of poly-TMPS (160°C). The glass transition temperature and heat of fusion were decreased as the DMS content was increased. The thermogravimetric curves for the copolymers indicated that the thermal stability of the triblock copolymer was intermediate between the DMS and TMPS homopolymers.     

Evaporative Heat Transfer of Annular Two-phase Flow of Air-water in a Small Vertical Tube

The evaporative heat transfer of the non-boiling annular two-phase flow of air-water in a small vertical tube with uniform wall heat flux was studied both theoretically and experimentally. A simplified two-phase flow boundary layer model was used to calculate the thickness of the water film attached to the wall, and from the liquid film thickness the evaporative heat transfer coefficients of the annular two-phase flow were obtained. Theoretical equations and semi-theoretical equations were proposed for predicting the evaporative heat transfer of the annular two-phase flow of air-water in a small vertical tube. The semi-theoretical prediction agrees well with the experimental data. The mechanism of the heat transfer enhancement is the evaporation of the thin liquid film attached on the wall.     

强化单螺杆挤出机内层流混合的方法

综述了单螺杆挤出机内聚合物熔体层流混合机理的研究进展，对提高混合的措施进行了分析总结，指出了进一步强化混合效果的方法。