Minireview: Methodology and instrumentation to evaluate critical pressure and temperature parameters

Critical parameters, such as critical temperatures, pressures, and densities, are basic in the development of supercritical fluid technology. However, the number of compounds for which critical parameters has been determined and has been limited by the current technology and the sensitivity of compound information to the external environment in a critical state. This paper provides an overview of the principles, key equipment, and methodologies to measure the critical parameters of compounds. The reliability of various determination methods is discussed, and future research into methods to determine critical compound parameters is suggested.     

Generation of simultaneous H+ and He+ band EMIC waves in the nightside radiation belt

Science China Technological Sciences - Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere. Here we report obliquely propagating H+ and He+...     

珠江三角洲设计产业现状及前景预测

准确地说,“珠江三角洲”已不再是一个纯粹意义上的地理概念,在中国市场经济稳定发展的今天,它早已成为“活跃的民营经济”的代名词。在广东经济发展过程中,珠三角一直扮演着十分重要的角色,自上世纪80年代以来,其国内生产总值一直占广东省国内生产的70％以上。珠三角经济的迅速腾飞有以下一些特点：     

下向胶结充填采矿法的采准布置与回采技术

本文简述了该采矿法在我国金属矿山的应用与发展；对采准工程布置和进路布置、进路断面形状与尺寸、进路回采方式、凿岩爆岩破、采场出矿和支护等作了详细叙述；对光面爆破、无掏槽爆破等适用技术亦作了详细介绍；最后对该方法的应用进行了简要的评价，对今后发展提出一些建议。     

高压无功集中补偿自动控制

我国供电系统使用的高压集中无功补偿装置，绝大部分是人工操作常常在需要补偿时不能及时投运，而过补偿时又不能及时断开，没有达到提高功率因数、降低电能的作用。     

天井钻机的发展现状与前瞻

本文综述了国外天井钻机发展概况和主要厂家的产品特色，国内天井钻机研制情况和系列产品类型，并对产品类型，并对今后我国天井钻机发展中应着重解决的问题提出了看法。     

Differentiated Electric Behaviors of La2/3Cu3Ti4O12 Ceramics Prepared by Different Methods

Microstructure and electric behaviors of La_2/3Cu₃Ti₄O₁₂ (LCTO) ceramics prepared by the sol‐gel method (SG) and solid‐state method (SS) have been systemically investigated. The results indicated that LCTO‐SG ceramics sintered at 1105°C for 15 h showed larger grain size, higher density, and especially higher dielectric constant up to about 0.9–1.6 × 10⁴ at 10²~10⁵ Hz compared to LCTO‐SS ceramics. The higher dielectric constant of the LCTO‐SG ceramics might be due to the stronger internal barrier layer capacitor (IBLC) effect. More notably, compared with LCTO‐SS ceramics, two kinds of dielectric anomalies, one conduction activation energy value and same activation energies for the conduction and relaxation process in LCTO‐SS ceramics, the LCTO‐SG ceramics showed three kinds of dielectric anomalies, two values of conduction activation energy, and decrease in conduction activation energy with increasing temperature. The activation energies for the conduction and relaxation process in LCTO‐SG ceramics showed great difference below about 210°C, suggesting that the mechanism of electrical conduction and dielectric relaxation seem to be different in LCTO‐SG ceramics. These remarkable differences in electric behaviors of LCTO ceramics prepared by sol‐gel and solid‐state methods were firstly found and analyzed.     

Modified Pechini Synthesis of Proton‐Conducting Ba(Ce,Ti)O3 and Comparative Studies of the Effects of Acceptors on its Structure,Stability, Sinterability,and Conductivity

The phase structure, chemical stability, sinterability, and electrical performance of the proton‐conducting Ba(Ce,Ti)O₃ solid solution with a series of acceptors M (M = In, Y, Sm) synthesized by a modified Pechini method were systematically investigated. The substitution of cerium with titanium was proved as an effective way to improve the stability of BaCeO₃. Especially for the BaCe_0.95Ti_0.05O_3?δ sample doped with In, no change in the phase was found even after treatment in the atmosphere containing both CO₂ and H₂O at 700°C for 10 h. Thanks to the highly sinteractive powders with particle size of ~100 nm, dense ceramics were easily acquired. Moreover, compared with the undoped BaCe_0.95Ti_0.05O₃ sample, In, Y, and Sm dopants further improved the sinterability of the solid solution. In particular, In played a role of sintering aid and led to the largest linear shrinkage of the ceramics. As to the electrical performance, the transport properties of the samples under various atmospheres were analyzed and compared. The impedance tests demonstrated the best electrical performance of the Y‐doped samples.     

A New Ferroelectric Phase of YMnO3 Induced by Oxygen‐Vacancy Ordering

Manganese oxides are good candidates of strongly correlated electron materials due to the uniqueness of electronic structure of manganese and the mobility of oxygen among lattice sites under external impacts. Here, we used electron beam as the excitation source to explore the structural evolution of YMnO₃ and identified a new phase under the radiation of electron beam in the transmission electron microscope. Analyses of the electron energy‐loss spectra reveal that this phase originates from ordered oxygen vacancy. We applied the first principles calculation to pick out the optimized stable structure with a lower polarization, and verified its correctness by electron diffraction and image simulations. Analyses of density of states indicate that weak Y–O covalence is favorable for the existence of ferroelectricity, supporting the electrostatic nature of ferroelectricity in the YMnO₃.     

Perfluorosulfonated ionomers membranes: Melt‐processing and characterization for ion exchange applications

Perflurosulfonated ionomers membranes with different ionic‐exchange capacity were successfully fabricated via melt‐extruding and casting of their –SO₂F precursors. A systematical investigation of the thermal stability, crystallinity, and rheological properties of the precursors was performed to secure their optimized processing conditions. The tensile properties of acid‐form membranes are found to increase with base‐hydrolysis time, where a tensile strength of 38.2 MPa is readily obtained after 24 h's base‐hydrolysis. The content of –SO₂F or –SO₃H containing side‐chains plays an important role in the thermal stability, rheological, and mechanical properties of the precursor or the acid‐form membranes. The strong ionic interactions, attributed to the –SO₃H groups, lead to decreased crystallinity and tensile strength for different IEC membranes. The acid‐form membranes exhibit good proton conductivity and low methanol crossover in comparison with reference Nafion membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39944.