Synthesis and characterization of new thermally stable poly(ester‐imide)s derived from 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl and various aromatic dihydroxy compounds

A series of new alternating aromatic poly(ester‐imide)s were prepared by the polycondensation of the preformed imide ring‐containing diacids, 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl (2a) and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl (2b) with various aromatic dihydroxy compounds in the presence of pyridine and lithium chloride. A model compound (3) was also prepared by the reaction of 2b with phenol, its synthesis permitting an optimization of polymerization conditions. Poly(ester‐imides) were fully characterized by FTIR, UV‐vis and NMR spectroscopy. Both biphenylene‐ and binaphthylene‐based poly(ester‐imide)s exhibited excellent solubility in common organic solvents such as tetrahydrofuran, m‐cresol, pyridine and dichloromethane. However, binaphthylene‐based poly(ester‐imide)s were more soluble than those of biphenylene‐based polymers in highly polar organic solvents, including N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide and dimethyl sulfoxide. From differential scanning calorimetry thermograms, the polymers showed glass‐transition temperatures between 261 and 315 °C. Thermal behaviour of the polymers obtained was characterized by thermogravimetric analysis, and the 10 % weight loss temperatures of the poly(ester‐imide)s was in the range 449–491 °C in nitrogen. Furthermore, crystallinity of the polymers was estimated by means of wide‐angle X‐ray diffraction. The resultant poly(ester‐imide)s exhibited nearly an amorphous nature, except poly(ester‐imide)s derived from hydroquinone and 4,4′‐dihydroxybiphenyl. In general, polymers containing binaphthyl units showed higher thermal stability but lower crystallinity than polymers containing biphenyl units. Copyright © 2005 Society of Chemical Industry     

Physicochemical and Functional Properties of Freeze-Dried and Oven Dried Corn Gluten Meals

The physicochemical and functional properties of convection oven- and freeze-dried gluten meals of two corn varieties were evaluated. The physicochemical properties (water solubility index, water absorption index, Hunter color parameters, and bulk density) and functional properties (water absorption, oil absorption, least gelation concentration, protein solubility, and emulsification properties) of convection-oven and freeze-dried corn gluten meals were compared with each other and soy flour. Freeze-dried corn gluten meals was observed to have lower bulk density (0.244-0.263 kg/m³) and was lighter in color (high L and ΔE) compared to their counterpart convection oven-dried gluten meals. Freeze-dried gluten meals from both corn varieties showed significantly higher oil absorption, water absorption, pH, emulsification, and protein solubility compared to oven-dried corn gluten meals. The gluten meals from both corn varieties had lower water absorption and bulk density but higher oil absorption than soy flour, suggesting the hydrophobic nature of corn proteins. Corn gluten meals formed thin (pourable) emulsions compared to soy flour emulsions, which were thick salad dressing type. Freeze- and convection oven-dried corn gluten meals showed significantly lower protein solubility measured at different pH than soy flour.     

Synthesis and characterization of an interpenetrating polymer network composed of poly(methacrylic acid) and poly(vinyl alcohol)

Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry     

Synthesis,characterization and ion exchange properties of zirconium(IV) tungstoiodophosphate,a new cation exchanger

Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L⁻¹ sodium tungstate, potassium iodate and 1 mol L⁻¹ orthophosphoric acid to aqueous solution of 0·1 mol L⁻¹ zirconium(IV) oxychloride. Its ion exchange capacity for Na⁺ and K⁺ was found to be 2·20 and 2·35 meq g⁻¹ dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb²⁺ from other metal ions.     

IPv6过渡机制讨论

本文在简要地介绍Ngtrans工作组提出的大多数过渡机制的基础上，尝试对它们进行区分、分类，并对每一种过渡机制的优缺点进行分析。另外．还对这些机制的布置以及一部分支持这些机制的产品平台进行讨论。     

Synthesis of LiFePO4 with fine particle by co-precipitation method

LiFePO₄ is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO₄ because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe²⁺ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO₄ is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO₄ fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.     

A new iterative order reduction (IOR) method for eigensolutions of large structures

Order reduction is a computationally efficient method to estimate some lowest eigenvalues and the corresponding eigenvectors of large structural systems by reducing the order of the original model to a smaller one. But its accuracy is limited to a small range of frequencies that depends on the selection of the retained degrees of freedom. This paper proposes a new iterative order reduction (IOR) technique to obtain accurately the eigensolutions of large structural systems. The technique retains all the inertia terms associated with the removed degrees of freedom. This hence leads to the reduced mass matrix being in an iterated form and the reduced stiffness matrix constant. From these mass and stiffness matrices, the eigensolutions of the reduced system can be obtained iteratively. On convergence the reduced system reproduces the eigensolutions of the original structure. A proof of the convergence property is also presented. Applications of the method to a practical GARTEUR structure as well as a plate have demonstrated that the proposed method is comparable to the commonly used Subspace Iteration method in terms of numerical accuracy. Moreover, it has been found that the proposed method is computationally more efficient than the Subspace Iteration method. Copyright © 2003 John Wiley & Sons, Ltd.     

Study of liquid injection impact on the performance of new refrigerant mixtures

In this paper, the test results of liquid injection impact on the performance of new alternative refrigerant mixtures such as: R-410A, R-507, R-407C and R-404A are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE standards. The performance data demonstrated that as liquid injection ratio increases, compressor head pressure and discharge temperature decrease. This has a positive effect in protecting the compressor. The effect of liquid injection on mixture behaviour varies from one mixture to another depending upon the mixture's composition. Furthermore, liquid injection appears to have a significant influence on R-410A behaviour compared to the other mixtures in question. Copyright © 2002 John Wiley & Sons, Ltd.     

RanGen: A Random Network Generator for Activity-on-the-Node Networks

In this paper, we describe RanGen, a random network generator for generating activity-on-the-node networks and accompanying data for different classes of project scheduling problems. The objective is to construct random networks which satisfy preset values of the parameters used to control the hardness of a problem instance. Both parameters which are related to the network topology and resource-related parameters are implemented. The network generator meets the shortcomings of former network generators since it employs a wide range of different parameters which have been shown to serve as possible predictors of the hardness of different project scheduling problems. Some of them have been implemented in former network generators while others have not.     

熔融碳酸盐燃料电池阴极材料的导电性

通过交流阻抗方法研究了熔融碳酸盐燃料电池阴极材料锂镍氧化物、锂钴氧化物和锂铁氧化物的导电性能。结果表明:锂镍氧化物电极的导电性最好,锂钴氧化物电极的导电性次之,锂铁氧化物电极的导电性最差;它们的导电性都随着温度的升高而按指数规律增加;在合成锂钴氧化物(或锂铁氧化物)的过程中,使Li2CO3轻微过量,可以提高锂钴氧化物(或锂铁氧化物)电极的导电性,而且在同一温度下,随着nLi∶nCo(或nLi∶nFe,摩尔比)值的增大,锂钴氧化物(或锂铁氧化物)电极的导电性显著增加。