Colossal dielectric response and relaxation behavior in novel system of Zr4+ and Nb5+ co-substituted CaCu3Ti4O12 ceramics

In this work, we developed a novel system of isovalent Zr⁴⁺ and donor Nb⁵⁺ co-doped CaCu₃Ti₄O₁₂ (CCTO) ceramics to enhance dielectric response. The influences of Zr⁴⁺ and Nb⁵⁺ co-substituting on the colossal dielectric response and relaxation behavior of the CCTO ceramics fabricated by a conventional solid-phase synthesis method were investigated methodically. Co-doping of Zr⁴⁺ and Nb⁵⁺ ions leads to a significant reduction in grain size for the CCTO ceramics sintered at 1060 °C for 10 h. XRD and Raman results of the CaCu₃Ti_3.8-xZr_xNb_0.2O₁₂ (CCTZNO) ceramics show a cubic perovskite structure with space group Im-3. The first principle calculation result exhibits a better thermodynamic stability of the CCTO structure co-doped with Zr⁴⁺ and Nb⁵⁺ ions than that of single-doped with Zr⁴⁺ or Nb⁵⁺ ion. Interestingly, the CCTZNO ceramics exhibit greatly improved dielectric constant (~10⁵) at a frequency range of 10²–10⁵ Hz and at a temperature range of 20–210 °C, indicating a giant dielectric response within broader frequency and temperature ranges. The dielectric properties of CCTZNO ceramics were analyzed from the viewpoints of defect-dipole effect and internal barrier layer capacitance (IBLC) model. Accordingly, the immensely enhanced dielectric response is primarily ascribed to the complex defect dipoles associated with oxygen vacancies by co-doping Zr⁴⁺ and Nb⁵⁺ ions into CCTO structure. In addition, the obvious dielectric relaxation behavior has been found in CCTZNO ceramics, and the relaxation process in middle frequency regions is attributed to the grain boundary response confirmed by complex impedance spectroscopy and electric modulus.     

小型无线场强探测传感器研究

近年来,微波加热因其高效性和清洁无污染等优点广泛应用于各个领域。然而,微波加热的不均匀性限制了微波作为高效加热能源的应用。通过测量和分析加热腔中的电场分布情况可以帮助设计人员改进微波加热腔体设计,提高微波加热的均匀性。现有的场强测量设备均为有线设备,应用场景极为有限。因此,本文提出了一种由探头、接收机和上位机三部分组成的无线场强探测传感器。介绍了无线场强探测传感器的结构和原理,采用横电磁波小室进行校准。通过一系列测量实验表明实测值与标准场强仪测量值一致性较好,可满足工程测量需求。     

An agile model for the eco-design of electric vehicle Li-ion batteries

Numerous design choices need to be made at several levels when designing high-tech products: technology, processes, architecture, components, materials… and these choices need to be made in relation to the product life cycle with the corresponding experts for each stage of the life cycle. At the same time, to ensure product sustainability, a specific focus on the future potential environmental impacts is highly recommended. In this research, an agile model is proposed to help designers make decisions while monitoring environmental performance indicators of high-tech solutions. The concept of Critical Product Life Cycle Parameters had to be introduced to facilitate the eco-design of the final product. The approach is illustrated by the Electric Vehicle Li-Ion Batteries case study.     

Assessing the cost-effectiveness of electric vehicles in European countries using integrated modeling

Electric vehicles (EVs) are considered alternatives to internal combustion engines due to their energy efficiency and contribution to CO₂ mitigation. The adoption of EVs depends on consumer preferences, including cost, social status and driving habits, although it is agreed that current and expected costs play a major role. We use a partial equilibrium model that minimizes total energy system costs to assess whether EVs can be a cost-effective option for the consumers of each EU27 member state up to 2050, focusing on the impact of different vehicle investment costs and CO₂ mitigation targets. We found that for an EU-wide greenhouse gas emission reduction cap of 40% and 70% by 2050 vis-à-vis 1990 emissions, battery electric vehicles (BEVs) are cost-effective in the EU only by 2030 and only if their costs are 30% lower than currently expected. At the EU level, vehicle costs and the capability to deliver both short- and long-distance mobility are the main drivers of BEV deployment. Other drivers include each state’s national mobility patterns and the cost-effectiveness of alternative mitigation options, both in the transport sector, such as plug-in hybrid electric vehicles (PHEVs) or biofuels, and in other sectors, such as renewable electricity.     

CO2 abatement and CH4 recovery at vehicle exhausts: Comparison and characterization of Ru powder and pellet catalysts

The catalytic conversion of CO₂ to CH₄ (Sabatier reaction) has been studied to develop an after-treatment process at vehicles exhausts. Three different formulations of Ru commercial catalysts, two in powder and one in pellets shape, were tested and characterized by means of X-ray powder diffraction, scanning electron microscopy (SEM-EDX), N₂ adsorption at −196 °C and temperature-programmed reduction (TPR).Experimental results show a high CO₂ conversion (X_CO2 = 0.96 @ T = 280 °C) for one powder catalyst formulation whereas the other one has maximum CO₂ conversion = 0.69. In both cases a high CH₄ selectivity is measured. High CO₂ conversion (X_CO2 = 0.92 @ T = 300 °C) is obtained also with pellet catalysts but only at lower GHSV values. The different behavior of the catalysts was ascribed to the different physicochemical properties and the key parameters for the application development of the process were identified. In particular, the possibility to use pellets or monolithic reactors, thus minimizing the pressure drops in the reactor, makes possible a commercial application in the treatment of vehicles exhausts.     

智能型电子式变频电动执行器及其应用

针对原有电动执行器只有以低速运行，通过极强的微调才能修正微小偏差这一缺点，提出智能型电动执行器与各种阀体譬合，利用数字化变频技术，改造目前采用模拟技术的电动执行器，使之具有变速运行、动态响应块，调节定位精度高、稳定性好，故障率低、使用寿命长和应用场合广泛的特点。     

The hydrogen economy, fuel cells, and electric cars

Hopes have again been raised about developing a “hydrogen economy”, in which hydrogen could be expected to replace oil and natural gas for most uses, including transportation and heating. It is again being claimed that hydrogen will be a widely available, clean, safe fuel. This article argues that such expectations are almost certainly illusory. Hydrogen, like electricity, is not an energy resource but an energy carrier. It takes more energy to extract hydrogen from water than burning the hydrogen can ever provide. There are also inevitable losses in storage, transmission, and final mechanical or heating applications. The question then turns on the efficiency—and safety—of the entire chain of conversion, from the energy source (fossil, solar, or other) to the final use. Moreover, energy sources (preferably renewable, for the long term) can be used for the direct creation of electricity, which can be introduced into the existing grid without requiring a vast investment in a new hydrogen distribution system. In addition, a hydrogen-based system would be unacceptably dangerous. This report will present a detailed technical and economic analysis of the problems with the proposed hydrogen economy and the advantages of some alternatives, principally electricity-based. A hypothetical case of what would be required for a hydrogen filling station serving the general public is closely examined.     

硅钢片模具设计及其线切割加工

论述了电磁铁铁芯 (硅钢片 )模具的设计要点及其线切割加工的技巧 ,提出了提高模具加工精度和使用寿命的有效措施。     

激光加电磁场诱变滇稻“三角大香糯”的育种初探

用He-Ne激光(1.5 mW,632.8 nm)辐照加电场磁场(电场强度1.2×106 m/V,2.0×106 m/V;磁感应强度4.8 T)激发处理了云南姚安三角大香糯稻种.通过育种和田间试验发现,多数处理种子仅产生非基因变异的表型变化,仅有5株发生性状变异.     

微型计算机的接触电流和接地线电流的测量

介绍了微型计算机的两种不同类型的泄漏电流的危害及其测量方法。