Role of adsorption and diffusion pathways on the CO2/N2 separation performance of nanocomposite (B)-MFI-alumina membranes

This work reports a detailed study of CO₂ and N₂ adsorption and diffusion pathways on MFI-alumina hollow fibres and their role on both pure and mixture CO₂/N₂ permeation. The hollow fibres have been prepared by pore-plugging hydrothermal synthesis starting from a clear solution with molar composition 1 SiO₂: 0.45 TPAOH: 27·8H₂O: xB(OH)₃ (x=0–0.02), showing a final nanocomposite architecture. A comprehensive screening has been performed to select the most suitable model for describing CO₂ and N₂ adsorption and pure permeation in the (B)-MFI-alumina hollow fibres. The classical Ideal Adsorption Solution Theory (IAST) has been implemented to different permeation models to account for binary CO₂/N₂ permeation within the fibres.     

基于人体感应技术交流电源连接器的设计与制作

很多时候,当人们离开用电场所由于没有及时切断电源,会造成电能的浪费甚至引发火灾事故。所以,运用较为成熟的红外感应及无线收发射技术,在电源与用电设备之间,研究设计了一种具有自动断电保护功能的交流电源连接装置。经过实际试用表明,这种连接器确有节电保安效果,具有实际推广应用的价值。     

Continuous electrochemical reduction of carbon dioxide into formate using a tin cathode: Comparison with lead cathode

Electrochemical reduction has been pointed out as a promising method for CO₂ valorisation into useful chemicals. This paper studies the influence of key variables on the performance of an experimental system for continuous electro-reduction of CO₂ to formate, when a tin plate is used as working electrode. Particular emphasis is placed on comparing the performance of Sn and Pb as cathodes. As was previously found with Pb, the influence of current density (“j”) using Sn was particularly noteworthy, and when j was raised up to a limit value of 8.5 mA cm⁻², important increases of the rate of formate production were observed at the expense of lowering the Faradaic efficiency. However, unlike what was found with Pb, the performance using Sn improved when the electrolyte flow rate/electrode area ratio was increased within the range studied (0.57–2.3 mL min⁻¹ cm⁻²). In this way, the use of Sn as cathode allowed achieving rates of formate production that were 25% higher than the maximum rates obtained with Pb, together with Faradaic efficiencies close to 70%, which were 15 points higher than those with Pb. These results reinforce the interest in Sn as electrode material in the electro-reduction of CO₂ to formate.     

CO2焊逆变式电源电子电抗的变结构控制仿真研究

介绍了一种适合用于CO2焊逆变式电源的电子电抗变结构控制方法.运用该方法和Matlab仿真工具,建立了电子电抗变结构控制仿真模型,并对电子电抗变结构控制的逆变式电源-电孤动态系统进行仿真.对比线性电子电抗控制和变结构电子电抗控制的不同结果,获得短路阶段电流初始上升率和后期上升率的不同,以及燃弧电流初始下降率和后期下降率的不同的电流波形,有效限制短路峰值电流,提高燃弧能量.试焊结果表明,电子电抗变结构控制的CO2焊逆变式电源对减小焊接飞溅和改善焊缝成形有着明显效果.     

信源可信度对核电公众接受影响的研究

公众对核电的态度受各种信息的影响,信息源可信度是说服力的重要决定因素.在我国,核安全监管机构、核电企业和专家是主要的核信息发布源,研究不同信息源可信度对公众核电态度的影响对核电的可持续发展十分重要.本研究基于源可信度理论,考察了公众对不同信源的可信度认知,构建了核电公众接受回归模型并开展实证研究.研究发现,不同源的可信...     

Oxidation behavior of three dimensional C/SiC composites in air and combustion gas environments

A three dimensional C/SiC composite was prepared and flexural strengths during combustion atmosphere and weight changes in air were investigated. When oxidized in air, the C/SiC composite gained weight above the cracking temperature, and lost weight below the cracking temperature. The weight loss reached its maxumum value at about 700°C. When oxidized during combustion atmosphere, the composite always lost weight due to the large temperature gradient along the specimen. The strengths were lowest at the area close to the nozzle wall where the flame temperature was about 700°C. There were four oxidation zones along the specimens. There was an unoxidized zone (I) at the surporting end. Close to this was the cracking-oxidation zone (II). At the high-temperature end was the coating-oxidation zone (IV). Between the coating-oxidation and cracking-oxidation zones was the transition zone (III). Uniform, non-uniform and superficial oxidation regimes were observed which were considered to be responsible for the weight changes in air and strength changes during combustion atmosphere.     

Electrospinning preparation and dye adsorption capacity of TiO2@Carbon flexible fiber

TiO₂@carbon flexible fiber was prepared by combining electrostatic spinning technology and hydrothermal synthesis method. The XRD, SEM, TEM and Zeta potential techniques were used to characterize the phase, microstructure and surface charge properties of the samples. The growth mechanism of TiO₂ nanoarray on carbon flexible fiber with different morphologies was studied, and the dye adsorption capacity of the samples was evaluated by methylene blue (MB) degradation effect. The results showed that proper doping amounts of TiO₂ particles improved the flexibility and the hydrophilic property of carbon fiber significantly, which was conducive to the deposition and growth of TiO₂ on the carbon fiber. With the increase of hydrothermal time, the TiO₂ nanoarray grew denser gradually along the [110] crystal surface. The negative charge on the surface of carbon fiber increased, which was benefited to the removal of MB. The dye adsorption capacity of TiO₂@carbon fiber was resulted from the synergistic effect of physical adsorption (carbon fiber) and photocatalysis (TiO₂) process.     

给水管网的分形

从管网生长的物理机制角度入手,对管网生长的分形特性进行了探讨,介绍了管网生长的动力源、速度、自组织生长过程,分析了管网形态各异的原因及其自仿射性,阐述了分形理论用于管网优化的前景,以期促进分形理论在管网工程中的应用。     

Thermodynamic investigation of methanol and dimethyl ether synthesis from CO2 Hydrogenation

The thermodynamics involved in the catalytic hydrogenation of CO₂ have been examined extensively. By assuming that methanol and dimethyl ether (DME) are the main products, two reaction systems each consisting of two pararell reactions were analyzed and compared in terms of the equilibrium yield and selectivity of the useful products, methanol and DME. The calculation results demonstrated that the production of DME allows much higher oxygenate yield and selectivity than that of methanol.     

Size dependence of energy gaps in small carbon clusters: the origin of broadband luminescence

The visible broadband luminescence from carbon-related films has recently been attributed to the band-tail states caused by the variations in the energy gap of individual sp² carbon clusters due to their difference in size and/or shape. In this paper, these band-tail states are classified into two parts: localized and confined. The localized states result from the structural deviation from graphite-like configuration, and the associated luminescence may be described by using the conventional theory for amorphous materials. The confined states are generated due to the existence of stable graphite-like local structures with various sizes and are the main factor for giving efficient, room-temperature luminescence. Our calculations of a series of small hexagonal carbon clusters with first-principle and semi-empirical methods demonstrate that the energy-gap distribution, due to the difference in size, is considerably broad, which may explain the broadband feature of luminescence. Calculations for some tetrahedral clusters were also made for comparison.