MVM材料轴对称平面应力问题的弹塑性解

采用MVM屈服准则,用相关联流动法则建立材料的本构关系;在平面应力条件下,对轴对称问题进行弹塑性分析,给出了应力场解;采用Prayer假设给出位移场,通过数值计算考察SD效应对结构的影响.     

精骛八极 心游万仞——论丝织图案创作中的艺术想象

本文论述了艺术想象在丝织图案创作中的重要作用,并以心理学为指导,以实践为基础,总结概括了艺术想象中提炼概括、打散构成、变形三种类型的创造性想象活动,并且强调了艺术家深入生活的重要意义。     

GC determination of synthetic hydrocarbon-based thermal heating fluid in vegetable oils

A combination of alumina column chromatography and GC procedures was developed for the determination of synthetic hydrocarbon-based thermal heating fluid (trademarked as Therminol 55^™) in vegetable oils. In each run, 3 g of sample solution was loaded onto the alumina (50 g) column and was eluted with 200 mL hexane. The eluate was then concentrated to 1 mL with the aid of a nitrogen stream prior to GC analysis. The GC chromatogram of the thermal heating fluid was characterized by the presence of a bell-shaped hump that could not be resolved into individual peaks. The lowest detection limit based on various spiked palm olein samples was 20 μg/g. The CV obtained were 6.5–8.9% for the intra-day study and 8.1–9.7% for the inter-day study. Overall recoveries of these samples ranged from 68.0 to 85.7% and the method was found to be good enough for quality control purposes.     

MoO2Br2体系催化合成1,2—聚丁二烯—催化活性和聚合物分子量

催化体系活性的高低与主助催化剂(Mo与AL)及单体(D真)的加料方式有关,以Bd-Al-Mo的加料顺序为最佳。在固定Mo/Bd=7.0×10~(-5),与MoCl_4、MoCl_6和MoO_2Br_2体系相比,MoO_2Br_2体系催化活性最高,催化体系中Br代Cl真后,Mn和[η]的时间变化率,△Mn/△t和△[η]/△t,增大约1.5倍,Mn较其他钼系高约2倍,1,2—键节含量约98％,亦高于含Cl帽体系。     

γ-丁内酯制备α-乙酰-γ-丁内酯的探讨

探讨了在醇钠的催化作用下,以γ-丁内酯(GBL)和醋酸乙酯缩合制取α-乙酰-γ-丁内酯(ABL)的可行性。在带搅拌的间隙式反应釜中,用正交试验设计和单因素试验研究了反应温度、进料摩尔比和反应时间以及醇钠用量对ABL收率的影响,获得了主要工艺参数。结果表明:在相同条件下,影响收率的主要因素是反应温度和反应时间。     

Linear or branched structure? Probing molecular architectures of fullerene-styrene copolymers by size exclusion chromatographs with online right-angle laser-light scattering and differential viscometric detectors

The poly(C₆₀-co-styrene)s prepared by radical copolymerizations of C₆₀ and styrene in bulk were characterized by multiple-detector size-exclusion chromatographs consisting of a refractometer, a differential viscometer, and/or a right-angle laser-light scattering photometer. The multidetector systems enabled the determinations of reliable, absolute molecular weights of the copolymers. The plots of intrinsic viscosity vs. molecular weight and radius of gyration vs. molecular weight offered valuable information about the molecular architectures of the copolymers. The slopes of the plots reveal that the structure of the copolymer changes with its C₆₀ content: the copolymer with a low C₆₀ content of 0.58 wt% possesses a linear structure, whereas its conger with a high C₆₀ content of 1.14 wt% possesses a branched structure.     

Studies on the hydrodynamic and heat transfer in a vapor-liquid-solid flow boiling system with a CCD measuring technique

The vapor-liquid-solid (V-L-S) flow boiling evaporator has the features of fouling preventing and heat-transfer enhancing. However, the mechanisms of flow and heat-transfer are still not well understood due to the system complex and the limitation of the measuring methods due to the characteristic of opaque of the system in practice. In this paper, a charge coupled device (CCD) measuring system is developed to investigate the hydrodynamic characteristics including the axial profiles of solid holdup and of solid velocity in a V-L-S three-phase natural circulating flow boiling system. The CCD measuring technique makes the three-phase qualitative observation and quantitative research possible. The heat-transfer characteristic of this system is also studied. The main results are as follows. The distributions of solid holdup and velocity are not uniform along the axial direction of the heating tube and both in liquid-solid two-phase region and in V-L-S three-phase region; however, the particle velocity in V-L-S three-phase region is much higher than that in liquid-solid two-phase region in heating tube. When increasing the heat flux, the solid holdup first increases and then decreases and the solid velocity gradually increases in heating tube. But in circulating tube, both the solid holdup and the solid velocity gradually increase. With the increase of the volume of added solid particles, the measured local solid holdup increases in both tubes; however, the variation of the solid velocity with the increase of the solid particles shows a characteristic of the wave and the general tendency is climbing for both tubes. The solid particles holdup in heating tube is always larger than that in circulating tube and the solid velocity in heating tube is lower than that in circulating tube. The presence of solid particles enhances the boiling evaporation process. The heat-transfer coefficient of the system increases with the increase of the heat flux and the volume of added solid particles. These research results provide some valuable references for the academic interest and for the industry application of this fouling preventing and heat-transfer enhancing installation.     

A Novel Temperature Stable Microwave Dielectric Ceramic with Garnet Structure: Sr2NaMg2V3O12

A garnet vanadate ceramic Sr₂NaMg₂V₃O₁₂ was prepared by the conventional solid‐state route, and the sinterability, microwave dielectric properties, and its chemical compatibility with Ag electrodes were investigated. Sr₂NaMg₂V₃O₁₂ sample could be well sintered at 900°C for 4 h with a relative density of 96.1%. X‐ray diffraction data showed that Sr₂NaMg₂V₃O₁₂ ceramics crystallized into a cubic garnet structure with a space group Ia‐3d over the sintering temperature range (830°C–930°C). The Sr₂NaMg₂V₃O₁₂ ceramic sintered at 900°C obtained the optimum microwave dielectric properties with a relative permittivity of 11.7, a Q×f of 37 950 GHz (at 11.0 GHz), and a almost zero τ_f value of ?2.9 ppm/°C. Chemical compatibility experiments showed no reaction between Sr₂NaMg₂V₃O₁₂ ceramics and Ag electrodes.     

Chelation of chitosan derivatives with zinc ions. II. Association complexes of Zn2+ onto O,N‐carboxymethyl chitosan

The chelation of zinc ions onto O,N‐carboxymethyl chitosan (ONCMCh) was characterized using a Fourier transform infrared (FTIR) spectrophotometer and a scanning electron microscope (SEM). From the FTIR spectra, little change in the absorption intensities and frequencies at 3300–3600 cm⁻¹ of Zn²⁺ ONCMCh chelated specimens suggested that  OH and  NH₂ groups were not participating in the chelation reaction. The absence of absorption bands at 1755–1700 cm⁻¹ suggested that the carboxyl group CO was not ionized, and the ionized CO bands were observed at 1400–1600 cm⁻¹ for chelated specimens. Thus, the chelation sites took place at the carboxyl group rather than at the  OH and NH₂ groups. It also confirmed that water‐insoluble chelates, which were formed through the Zn O and Zn N bonds, presented a tetrahedral structure. The water‐soluble complexes where zinc ions connected with oxygen of CO and water molecules were only due to electron attraction. Formation of different microstructures on the surfaces, as revealed by SEM, provided evidence to distinguish different chelating mechanisms between water‐soluble and water‐insoluble complexes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1476–1485, 2001     

气相色谱法测定三氯乙酰氯的含量

介绍了用无水乙醇作衍生反应试剂,采用5％PEG－12000填充柱和PID检测器,对三氯乙酰氯的衍生物进行分离,以草酸二乙酯为内标物,进行了内标法定量,实现了三氯乙酰氯的简便,快速,无腐蚀气相色谱分析。