Energy consumption and economic growth in China: A multivariate causality test

This study takes a fresh look at the direction of causality between energy consumption and economic growth in China during the period from 1972 to 2006, using a multivariate cointegration approach. Given the weakness associated with the bivariate causality framework, the current study performs a multivariate causality framework by incorporating capital and labor variables into the model between energy consumption and economic growth based on neo-classical aggregate production theory. Using the recently developed autoregressive distributed lag (ARDL) bounds testing approach, a long-run equilibrium cointegration relationship has been found to exist between economic growth and the explanatory variables: energy consumption, capital and employment. Empirical results reveal that the long-run parameter of energy consumption on economic growth in China is approximately 0.15, through a long-run static solution of the estimated ARDL model, and that for the short-run is approximately 0.12 by the error correction model. The study also indicates the existence of short-run and long-run causality running from energy consumption, capital and employment to economic growth. The estimation results imply that energy serves as an important source of economic growth, thus more vigorous energy use and economic development strategies should be adopted for China.     

ATG地空通信业务分析与策略研究

随着中国民航“空中手机开机”时代的到来,乘客对于空中上网的需求日益强烈。相对于更适用于跨国、越洋航线的卫星接入方案,通过飞机搭载通信设备接入地面专用网络的方案具有改造成本低、速率快、时延小等优势,将成为80%为窄体机的国内航班接入互联网的主流方式。本文通过业务预测、频率和干扰分析,为地空通信业务发展和网络部署提供了有效的策略和建议.     

电液系统位置压力非线性自适应双闭环控制

随着技术的不断发展电液伺服系统的用途越来越广泛,电液伺服系统在工业设备工程机械、冶金机械、机械制造等领域占据着举足轻重的地位.本文建立位置压力非线性自适应双闭环控制,通过李雅普诺夫函数算法的稳定性探索闭环系统的稳定性.通过李雅普诺夫函数逐步分析算法的半负定.根据半负定判定该算法的稳定性,若为半负定则此时的函数为渐近稳定的.若不是半负定则不是渐进稳定的.采用李雅普诺夫函数算法的稳定性的控制方法,可以使系统的误差逐渐减小,从而使系统趋于稳定状态.从结果分析可以看出采用非线性自适应双闭环控制对跟踪位置压力的期望值有明显的提高,并且误差值也越来越小.     

Sulfonated poly(ether ether ketone)/polybenzimidazole oligomer/epoxy resin composite membranes in situ polymerization for direct methanol fuel cell usages

A diamine-terminated polybenzimidazole oligomer (o-PBI) has been synthesized for introducing the benzimidazole groups (BI) into sulfonated poly(ether ether ketone) (SPEEK) membranes. SPEEK/o-PBI/4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes in situ polymerization has been prepared for the purpose of improving the performance of SPEEK with high ion-exchange capacities (IEC) for the usage in the direct methanol fuel cells (DMFCs). The composite membranes with three-dimensional network structure are obtained through a cross-linking reaction between PBI oligomer and TMBP and the acid-base interaction between sulfonic acid groups and benzimidazole groups. Resulting membranes show a significantly increasing of all of the properties, such as high proton conductivity (0.14 S cm⁻¹ at 80 °C), low methanol permeability (2.38 × 10⁻⁸ cm² s⁻¹), low water uptake (25.66% at 80 °C) and swelling ratio (4.11% at 80 °C), strong thermal and oxidative stability, and mechanical properties. Higher selectivity has been found for the composite membranes in comparison with SPEEK. Therefore, the SPEEK/o-PBI/TMBP composite membranes show a good potential in DMFCs usages.     

Prediction of tensile capacity based on cohesive zone model of bond anchorage for fiber-reinforce dpolymer tendon

In this paper, analytical solutions based on a cohesive zone model (CZM) are developed for the bond fiber-reinforce dpolymer (FRP) tendon anchorage under axial load. With bilinear cohesive laws, the analytical solutions of tensile capacity of anchorages are derived. The concept of the minimum relative interface displacement s_m is introduced and used as the fundamental variable to express all other parameters, such as external tensile load. Experimental and analytical results show that the thickness of the anchoring material is main factor affecting tensile capacity. The characteristic bond strength depends mainly on the properties of the bonding agent-anchoring material, the geometry and surface conditions of the tendon, and the radial stiffness of the confining medium. A comparison of the calculated and experimental results showed good agreement. Formulas based on fracture energy of the tension load capacity derived in the present work can be directly used in the design of FRP tendon anchorage.     

Fabrication of mesoporous dendritic silica nanofibers by using dendritic polyaniline templates

A new method to prepare dendritic inorganic nanofibers by using dendritic polyaniline (PANI) nanofibers as templates was described. Dendritic PANI/silica composite nanofibers were synthesized via a self-assembly sol–gel progress. Both the organic and the inorganic phases were co-continuous and interpenetrated each other forming interpenetrating polymer network (IPN) structure. Mesoporous dendritic silica fibers were derived after removing the PANI component from the IPN structured PANI/silica fibers by calcinations. The diameters of the as-prepared silica fibers are tunable since the diameters of the PANI fibers could be controlled easily by changing the synthetic conditions. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption/desorption isotherms experiments were employed to characterize the as-prepared nanomaterials.     

EPC网络及其在制造业中的应用分析

EPC网络是基于互联网和RFID技术发展起来的一种自动识别系统。本文介绍了EPC网络的组成、工作原理及其特点。阐述了EPC网络在制造业中的应用并且详尽地分析了EPC网络在制造业中应用的优点和前途景。     

Benzocyclobutene-functionalized poly(m-phenylene): A novel polymer with low dielectric constant and high thermostability

A novel benzocyclobutene-functionalized poly(m-phenylene) was synthesized. This polymer showed good solubility and film-forming ability. When being heated at high temperature, the polymer film converted to an insoluble cross-linked network structure and did not show any cracks. Thermogravimetric analysis of the polymer film exhibited a weight loss of 5% at 547 °C and a char yield of 71% at 1000 °C in nitrogen. Moreover, the cured film had good dielectric and mechanical properties. In a range of frequencies from 0.10 MHz to 30 MHz, the cured film showed dielectric constant of less than 2.7, which was comparable with these of polyimides, polycyanates and the SILK resins. On a nano indenter system, the cured film showed an average hardness of 1.05 GPa and a Yong's modulus of 39.18 GPa. Those data imply that the polymer could be used as the varnish for enameled wire, sizing agents for high performance carbon-fiber, and encapsulation resins in microelectronic industry.     

Characteristics of the functionally graded coating fabricated by plasma transferred arc centrifugal cladding

Iron-based powders were deposited on the internal wall of a cylinder by means of plasma transferred arc centrifugal cladding. The as-fabricated coating was a functionally graded triple layer coating with microstructures varying from hypereutectic firstly to near eutectic, and then to hypoeutectic structures along the radial direction. Significant enrichment of carbides [M₇C₃ and M₂₃(C, B)₆] was observed in the inner layer. The centrifugal force was responsible for the chemical composition gradient which resulted in the microstructures gradient. Theoretical analysis revealed that Cr, C and B atoms moved toward the inner layer whereas Fe, W and Mo atoms moved toward the outer layer under the effect of centrifugal force, which was confirmed by the quantitative analysis and line-scan profile. Wear resistance of the inner layer of the coating was fairly higher than that of the substrate.