Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

A set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η ], translational diffusion D and flotation in a centrifugal field s ) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses M _sD were determined. The Mark–Kuhn–Houwink equations for the range of M _sD from 2240 to 15 300 g mol^?1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry     

Synthesis and Characterization of Polysiloxane Grafted Polyamide‐Amine Surfactants

Dendritic‐linear surfactants 1G PAMAM–Si and 2G PAMAM–Si were prepared by grafting the single epoxy terminated polydimethylsiloxane (SEPDMS) onto the 1G and 2G dendritic polyamide‐amine (PAMAM), respectively. SEPDMS was synthesized by hydrogen‐terminated polydimethylsiloxane and allyl glycidyl ether in chloroplatinic acid. The optimum grafting conditions were obtained by single‐factor experiments when the mole ratio of SEPDMS and PAMAM was 0.95:1, the reaction temperature was 60 °C, the reaction time was 5 h and the solvent percentage was 60%. The molecular structure of PAMAM–Si was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatograph and potentiometric acid‐base titration. Furthermore, the stability, surface activity and emulsifying ability of the prepared surfactants were studied. The results showed that PAMAM–Si has high stability against dilution, acids, alkalies and salts. PAMAM–Si surfactants can significantly reduce the surface tension of water. And 2G PAMAM–Si is superior to 1G PAMAM–Si at the ability of emulsifying oil.     

Stability of gravitationally unstable double diffusive transient boundary layers with variable viscosity in porous media

We study the double diffusive convection (DDC) in porous media through linear stability analysis (LSA) and direct numerical simulations (DNS). Unlike the previous studies that assume static solutal or thermal fields, the developed model is able to capture the transient behavior of both fields. We show that under the assumption of static field, the role of Lewis number cannot be distinguished. Under transient fields, we conclude that higher Lewis numbers result in earlier instability of the boundary layers. Moreover, the effect of viscosity contrast is explained in terms of the mobility of the boundary layer. The DNS results confirm the validity of LSA predictions. We also obtain the critical Rayleigh number and show that in the presence of viscosity contrast, it can be much smaller than the conventional limit of 4π². This study provides a better understanding of the transient nature of DDC in the presence of viscosity variations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2471–2482, 2017     

PE-LLD-g-(GMA-co-St)的反应挤出及应用

采用反应挤出方法,制备了甲基丙烯酸缩水甘油酯(GMA)和苯乙烯(St)接枝改性的线型低密度聚乙烯(PE-LLD)产品[PE-LLD-g-(GMA-co-St)]。研究了St用量和反应时间对PE-LLD-g-(GMA-co-St)接枝率和熔体流动速率(MFR)的影响。结果表明,当St与GMA质量比为5︰9,反应时间为120 s时,所制备试样接枝率达到1.69%,MFR(190℃,2.16 kg)达0.69 g/10 min。将制备的PE-LLD-g-(GMA-co-St)和PE-LLD-g-MAH作为相容剂应用于聚乙烯无卤阻燃电缆料,对比了水煮老化前后的拉伸性能。结果表明,与PE-LLD-g-MAH为相容剂的电缆料试样相比,以PE-LLD-g-(GMA-co-St)为相容剂的电缆料试样虽然拉伸强度较低,但具有较高的断裂伸长率和较高的耐水煮老化性能,其拉伸强度和断裂伸长率分别为13.9 MPa和231%,水煮10 h后的保留率分别为84.9%和85.7%,满足电缆行业应用标准要求。     

反离子对部分电荷中和的聚乙烯亚胺接枝介质的蛋白质色谱行为的影响

前期研究表明部分电荷中和的聚乙烯亚胺接枝琼脂糖介质FF-PEI-R440具有较高静态吸附容量和快速传质速率。本文选取硫氰酸根离子、氯离子、磷酸氢根离子以及硫酸根离子这4种反离子,在离子强度为0.03、0.06 mol·L^-1下,研究其对FF-PEI-R440吸附与洗脱行为的影响。结果表明：在两种离子强度下,饱和吸附容量的增加顺序均为SCN^- < SO₄^2- < HPO₄^2- < Cl^-;在低离子强度下,除SCN^-外,反离子种类对传质速率和动态结合容量没有显著影响;在高离子强度下,传质速率的增加顺序为SCN^- < SO₄^2- ≈ Cl^- < HPO₄^2-,而动态结合容量的增加顺序与饱和吸附容量序列一致;两种离子强度下Cl^-均保持最高的动态结合容量;反离子种类对蛋白质洗脱行为没有显著影响。上述结果说明反离子主要影响FF-PEI-R440的吸附性能,而不影响洗脱,且流动相中选择Cl^-为反离子最利于FF-PEI-R440的实际柱色谱操作。     

竹炭改性涤纶机织物远红外性能的测试与分析

为了研究竹炭改性涤纶织物的远红外性能及相关影响因素,将7种不同规格的竹炭纤维机织物进行了远红外发射率的测试与分析,并采用正交方法探究了影响竹炭织物远红外功能的因素。结果表明:随着织物中竹炭纤维含量的增加,织物的远红外发射率增大;竹炭纤维织物中经、纬纱的竹炭纤维含量对其远红外发射率的影响是非常显著的,纱线的线密度对织物的远红外发射率影响也是显著的,而织物组织对织物的远红外发射率几乎没有影响。     

基于正交试验设计的聚羧酸高效陶瓷减水剂性能

以马来酸酐(MA)、丙烯酸(AA)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为单体,采用水溶液聚合法制备了一种线型MA/AA/AMPS聚羧酸高效陶瓷减水剂。通过正交试验,研究了各反应条件对添加了0.35%(相对绝干料浆)线型MA/AA/AMPS聚羧酸高效陶瓷减水剂的陶瓷坯体料浆流动时间的影响,并进一步利用FT-IR和XRD等手段分别对线型MA/AA/AMPS聚羧酸高效陶瓷减水剂的官能团结构和晶相结构进行表征,分别用POM和SEM照片观察陶瓷坯体料浆的分散情况和陶瓷坯体试样的断面形貌。结果表明,线型MA/AA/AMPS聚羧酸高效陶瓷减水剂最佳合成条件为：聚合温度为80 ℃、引发剂用量占聚合单体总质量的9%、n(MA)∶n(AA)∶n(AMPS)=1.0∶3.5∶1.5和聚合时间为4 h。当线型MA/AA/AMPS聚羧酸高效陶瓷减水剂掺量为0.35%(相对绝干料浆)时,陶瓷坯体料浆体系的黏度从689.5 mPa穝降低到56.8 mPa穝。     

MODELING SIMULATION AND CONTROL OF THE WOOD DRYING PROCESS Part 3. Programming and Computer Solutions

Abstract

In this paper, the programming and computer subroutines of wood drying process (WDP) are studied. This WDP is represented by the set of non-linear partial differential equations which are decomposed into fast and slow subsystems. Moreover, a few procedures have been used to estimate piecewise linear parameters and to reconstruct the real parameter distributions along the drying kiln. Several aspects including estimating stepsize, tuning sensitivity of the operating functions, and general solutions of the internal model (M) are discussed and illustrated     

Nonparametric testing against restricted alternatives under progessive censoring

Nonparametric testing procedures under progressive censoring schemes are often adopted in clinical trials and life testing experimentations. In a variety of situations, a null hypothesis (of the homogeneity of distributions) may be tested against a restricted viz., orthant or ordered alternative. Though such tests in a general setup have been considered in a complete sample or a single point censored (or truncated) experimental scheme, there has not been much progress with these tests in a progressively censored setup. Genuinely distribution free tests based on simple linear rank statistics and the classical union intersection principle are considered. The theory of such time sequential tests rests heavily on some basic invariance principles, and these are studied as well. The case of proportional hazard models is also treated briefly. The main emphasis is laid on the development of the relevant asymptotic theory, and in this context, some (sub) martingale characterizations of progressively censored rank statistics have been incorporated.     

A Comparison of Linear with Nonlinear Viscoelastic Solutions for Shear Stress Concentration in Double Lap Joints

The correspondence principle based on the Maxwell model and a nonlinear viscoelastic solution involving an iterative scheme are used to describe the time dependent variation of the adhesive maximum shear stress in adhesively bonded double lap joints. The results indicate that if the correspondence principle is applied, the use of Maxwell chain is necessary to approximate the continuous change in the relaxation time and to coincide with the results calculated using the nonlinear viscoelastic theory.