Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector （MPGD）, thick GEM with electrodes made of a resistive material （RETGEM） is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar＋CO2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

氯原子在Cu(111)表面的吸附结构和电子态

密度泛函理论(DFT)总能计算研究了不同覆盖度下氯原子在Cu(111)表面的吸附结构和表面电子态。计算结果表明,清洁Cu(111)表面自由能 为15.72 ,表面功函数φ为4.753eV。在1/4ML和1/3ML覆盖度下,每个氯原子在Cu(111)表面fcc谷位的吸附能分别等于3.278eV/atom和3.284eV/atom。在1/2ML覆盖度下,两个紧邻氯原子分别吸附于fcc和hcp谷位,氯原子的平均吸附能为2.631eV/atom。在1/3ML覆盖度下,fcc和hcp两个位置每个氯原子吸附能的差值约为2meV/atom,与正入射X光驻波实验结合蒙特卡罗方法得到结果(<10meV/atom)基本一致。在1/4ML、1/3ML和1/2ML覆盖度下,吸附后Cu(111)表面的功函数依次为5.263eV、5.275eV和5.851eV。吸附原子和衬底价轨道杂化形成的局域表面电子态位于费米能级以下约1.2eV、3.6eV和4.5eV等处。吸附能和电子结构的计算结果表明,氯原子间的直接作用和表面铜原子紧邻氯原子数目是决定表面结构的两个重要因素。     

Magnetically confined discharge CO laser

Under the condition of magnetic confinement, the paper analyzes the following discharge processes from CO gas: (1) the variation of electron energy distribution; (2) the impact excitation rates of electron for the vibrational CO molecules; and (3) the vibrational-state population of CO molecule and small-signal gain. Our results show that, by adding magnetic field, the electron density increases greatly in the energy region corresponding to the maximum electron cross sections of CO molecule, while the electron impact on excitation rates also increases. At the same time, the vibrational-state population of CO molecule and the laser small-signal gain of every vibrational level are also higher than that without magnetic field.     

超临界CO2-DME混合物竖直圆管内传热特性数值研究

本文采用RNG k-ε湍流模型对超临界CO₂/DME(二甲醚)二元混合工质在竖直圆管内的传热特性进行了数值模拟研究。管径4 mm,管长为1000 mm;CO₂/DME浓度配比分别为97/3、95/5、92/8、90/10、85/15、以及70/30;质量流速为125～200 kg·m^-2.s^-1;热流密度为15～30 kW.m^-2,入口温度295～308 K,入口压力8～15 MPa。不同浓度配比的混合工质在各自临界压力下应用时,随着DME浓度的增加,换热系数的峰值逐渐减低,但在温度大于310 K时混合工质的换热系数会高于纯CO₂。压力相同时,随着DME浓度的增大,拟临界温度升高,换热系数峰值点也随之向温度升高的方向移动。混合工质的换热系数随质量流速的增大而增大。在拟临界点前,增大热流密度及降低压力对管内传热有利,而在拟临界点之后,换热系数随热流密度的升高以及压力的降低而降低。     

超临界CO2布雷登循环热电联供系统多目标优化

本文研究了以超临界CO₂布雷登循环为原动机的热电联供系统,对系统主要运行参数进行了分析,得到运行参数对于系统热力学性能和经济性能的影响规律。同时,以一次能源利用率和单位输出成本作为目标函数,采用多目标遗传算法对系统进行了优化;在优化结果的基础上,通过TOPSIS法决策出最优解,并与单目标最优解进行对比。结果表明,透平进口温度、透平进口压力和压缩机进口温度的增大有利于系统效率的提高;作为代价,成本也相应增加。在热电比0~4范围内,尽可能增大热电比能够最大程度上降低系统的单位输出成本,提高能源的利用率。     

燃气-蒸汽联合循环余热回收系统性能研究

燃气发电是我国城市供电的主要形式之一,针对LNG接收站一体的电厂发电模式进行研究,提出一种新型燃气-蒸汽联合循环热电联供系统,利用超临界CO2布雷顿循环结合有机朗肯循环(ORC)辅助发电,将LNG作为冷源,对烟气余热进行三级利用.通过构建热力学和经济模型,以Aspen Plus软件模拟值为基础,结果表明:在消耗燃料1....     

高温吸热管内超临界CO2传热特性的数值模拟

研究超临界CO2在高温吸热管内的传热特性是将其应用于聚光太阳能热发电技术中的基础.本文对此进行了数值模拟研究,分析了流体温度、流动方向、系统压力、质量流率和热流密度对对流传热系数和Nu数的影响.结果表明:高温区(800—1050 K)的对流传热系数和Nu数受流动方向和系统压力的影响均很小,但都随着质量流率的增大以及热流...     

Electronic structures of CO adsorbed Pt-skin surface on Pt–Co and Pt–Ni alloys

By using angle resolved photoemission spectroscopy, we investigate the electronic structures of Pt-skin layer of Pt–Co and Pt–Ni alloys with CO molecules on the surface. Measured Fermi surface maps and band dispersions reflect the signatures of chemical bonding between Pt-skin layer and CO molecules. Furthermore, the degree of chemical bonding strength of CO molecules, estimated from the energy shift of the participating bands, is found to be reduced on both Pt bimetallic alloys. Our results show how the surface band structure of Pt bimetallic alloys is modified with molecular orbitals of CO molecules on the surface, revealing the important role of the electronic structure in the determination of chemical properties of bimetallic alloys.     

The electrochemical reduction of CO2 on a copper electrode in 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF4) monitored by surface‐enhanced Raman scattering (SERS)

The electrochemical conversion of CO₂ into value‐added products using room temperature ionic liquids as solvent/electrolyte has been proposed as an alternative to minimize the environmental effects of CO₂ emissions. A key issue in the design of electrochemical systems for the reduction of CO₂ is the in situ identification of intermediate surface species as well as reaction products. Copper electrodes, besides being used as cathodes in the electrochemical reduction of CO₂, present surface‐enhanced Raman scattering (SERS) when properly activated. In this sense, the electrochemical reduction of CO₂ over a copper electrode in the room temperature ionic liquids 1‐n‐butyl‐3‐methyl imidazolium tetrafluoroborate (BMI.BF₄) was investigated by cyclic voltammetry and by in situ SERS. The cyclic voltammetries have shown that the presence of CO₂ on the BMI.BF₄ anticipates the reduction of BMI⁺ to the corresponding carbene. Fourier‐transform‐SERS spectra excited at 1064 nm and SERS spectra excited at 632.8 nm have shown vibrational signals from adsorbed CO. These SERS results indicated that CO adsorbs on the copper surface at two different surface sites. The observation of a 2275 cm⁻¹ vibration in the SERS spectra also confirmed the presence of chemically adsorbed CO₂. Other products of CO₂ reduction in BMI.BF₄, besides CO, were identified, including BMI carbene and the BMI‐CO₂ adduct. The SERS results also suggest that the presence of a thin film of Cu₂O on the copper surface anticipates the reduction of CO₂ to CO, an important component of syngas. Copyright © 2016 John Wiley & Sons, Ltd.     

CO+分子离子彗尾带系在近红外区域的光谱研究

CO 分子离子是一种重要的瞬态自由基分子,许多研究者对该带系进行了大量的研究。文章采用光外差-磁旋转-速度调制光谱技术测量了12C16O 分子离子彗尾带系(A2Πi-X2Σ )在近红外区域的3个支带(0,3),(1,4)和(3,6)的振转吸收光谱。利用最小二乘法拟合,得到了上态A2Πi(ν′=0,1,3)的精确的分子常数。进一步验证了光外差-磁旋转-速度调制光谱技术在吸收光谱测量中的优越性。