速溶咖啡特征性指标的多元统计分析

该文对商品速溶咖啡进行调查统计的基础上,运用因子分析法中的主成分分析法的多元统计分析方法,对样本的特征性指标进行主分析。结果表明:速溶咖啡特征性指标中能量、蛋白质、脂肪和碳水化合物为同一类指标,钠为另一类指标。此结论基本上是正确合理的,对速溶咖啡的质量控制及其质量检验部门的初步检测等都具有一定的指导作用,可以减少检测步骤、提高检测效率、节约检测成本,为选用步骤少效率高低成本的检测对象来反应速溶咖啡质量提供了理论依据。     

Preparation and studies of new phosphorus‐containing diols as potential flame retardants

Several new phosphorus‐containing potential flame retardants (FRs) were prepared and evaluated for heat release reduction potential, by incorporation of the molecules into polyurethane samples, generated from methylene diphenyl diisocyanate and 1,3‐propane diol. The potential FRs were all prepared from commercial diisocyanates, with the phosphorus‐containing substructure introduced as a semicarbazone. All of the target structures were diols, to facilitate their incorporation into a polyurethane main chain. The polyurethane samples were prepared via copolymerization, and analysis clearly demonstrated that the potential FRs were chemically incorporated, prior to heat release testing. The heat‐release reduction potential of these substances was evaluated using the microcombustion calorimeter. Results demonstrated that both heat release reduction potential and char formation were structure dependent. Some of the compounds containing an aromatic core had more effect on char formation (higher char yields) and peak heat‐release rate (lowered heat release) than just phosphorus content alone.     

从学生需求看大学英语语言测试——以漓江学院非英语专业学生为例

本文通过访谈法和问卷调查法来了解漓江学院非英语专业学生对英语学习的需求。该研究旨在探寻学生需求和语言测试之间的关系。通过对收集数据的分析,我们发现学生需求和大学英语语言测试相互影响。     

注射模试模分析及改进策略

通过试模结果分析,找出试模不合格的各种原因,进行归类总结,并从进胶方式、塑件设计工艺性评估、模具设计和模具加工等4个方面进行了深入分析和相应地改进。     

The influence of laboratory test procedures on scale growth kinetics and microstructure during steam oxidation testing

Abstract

Laboratory exposures cannot reproduce all the features present in service conditions. The experimentalist is faced with the conflict between increasing the complexity of laboratory tests to replicate service more closely and keeping testing costs low by maintaining a simple procedure. The influence of various experimental parameters, which can be controlled in the laboratory, on the steam oxidation response of materials is reviewed and recommendations for best practice are proposed.     

Anomalous creep behaviour of 316 stainless steel at 550°C

The results offifteen constant-load creep tests at 550°C, with nominal stresses in the range 200 to 360 MPa and with test durations ofup to 14 000 h, are presented. The usual primary, secondary and tertiary creep behaviour was exhibited for nominal stresses greater than about 330 MPa. At lower stresses, ‘renewed’ primary and secondary creep regions were observed. The renewed secondary creep strain rates were found to be about an order of magnitude greater than the initial secondary creep strain rates. The results indicate that the occurrence ofthe renewed primary and secondary creep regions is associated with time-dependent exposure to a temperature of 550°C. The presence or magnitude of the prior stress level does not appear to have any significant effect.

The results are relevant to design procedures because extrapolation of short duration or high stress data to long-term design lifetimes is often required. Unless the possibility ofthe occurrence ofrenewed primary and secondary creep is taken into account, gross errors in strain predictions could occur.     

基于JC-5600ATE的单/双电源运算放大器测试方法

集成运算放大器具有成本低、功能多等优点,可广泛用于自动控制系统、测量仪表等其他电子设备中。近年来集成运放的指标在不断提高,性能也在不断提升,伴随着运算放大器的发展,对用来考核运算放大器指标的测试技术也提出了相应的要求,对测试系统(Automatic Testing Equipment,以下简称ATE)的性能要求也相应变高。阐述了单、双电源集成运算放大器在JC-5600ATE上的测试方法,并分析了两者的测试差异。     

Two decades of Web application testing—A survey of recent advances

Since its inception of just over two decades ago, the World Wide Web has become a truly ubiquitous and transformative force in our life, with millions of Web applications serving billions of Web pages daily. Through a number of evolutions, Web applications have become interactive, dynamic and asynchronous. The Web׳s ubiquity and our reliance on it have made it imperative to ensure the quality, security and correctness of Web applications. Testing is a widely used technique for validating Web applications. It is also a long-standing, active and diverse research area. In this paper, we present a broad survey of recent Web testing advances and discuss their goals, targets, techniques employed, inputs/outputs and stopping criteria.     

Mechanical properties of calcium silicate hydrate (C–S–H) at nano-scale: A molecular dynamics study

Calcium silicate hydrate (C–S–H) is the most important binding phase of cement paste and can determine the mechanical properties of cementitious material. The multi-scale nature of C–S–H gel brings about challenges in interpreting the mechanical properties of C–S–H. C–S–H models at the nano scales are commonly formulated by the aggregation of colloids that consist of layered molecular structures. In this study, the mechanical properties of C–S–H were investigated at the molecular level (∼5 nm). Uniaxial tension testing in the x, y, z directions was applied to the layered structure of C–S–H. The structural difference in the layer leads to heterogeneous mechanical properties in three directions. Particularly in the z direction, the C–S–H layer connected by H-bonds and Ca²⁺, has the weakest tensile strength. Resulting from the investigation, it can be concluded that the simulation can provide molecular insights into the linkage between molecular and larger scale structures.     

Acrylic Resins as Rate-Controlling Membranes in Novel Formulation of a Nine-Day 17β-Estradiol Transdermal Delivery System: In Vitro and Release Modifier Effect Evaluation

The feasibility of transdermal controlled delivery system of 17 β-estradiol was investigated by conducting in vitro release studies. Several new 17 β-estradiol unilaminate adhesive devices capable of releasing 17 β-estradiol in a controlled fashion over a 24-h, 36-h, 96-h, 104-h, 168-h, and 216-h period have been developed using acrylic resins (Eudragits E100, RSPO, and RLPO) as adhesive and rate-controlling polymers. The in vitro release profiles of 17 β-estradiol from various TDS unilaminate devices were characterized in a new developed dissolution tester vessel (total volume 200 ml), using a new paddle. The release of drug from different formulations was measured by a sensitive high-performance liquid chromatographic (HPLC) method. The release of drug from all prepared adhesive devices seems to obey zero-order kinetics (r > 0.98). The effect of two different plasticizers (acetyltributyl citrate [ATBC] and triethyl citrate [TEC]) on the release patterns of 17 β-estradiol from TDS formulations was studied, and they were almost identical. The effect of two different release modifiers, propylene glycol (PG) and myristic acid (MA), on the release pattern of 17 β-estradiol from prepared unilaminate devices was evaluated. It was shown that the use of these release modifiers significantly increased the release of 17 β-estradiol from a TDS unilaminate patch. Furthermore, these data clearly demonstrated that the acrylic resins are suitable polymers for the preparation of 17 β-estradiol TDS adhesive devices.