Theoretical study of molecular hydrogen and spiltover hydrogen storage on two-dimensional covalent-organic frameworks

Molecular hydrogen and spiltover hydrogen storages on five two-dimensional （2D） covalent-organic frameworks （COFs） （PPy-COF, TP-COF, BTP-COF, COF-18 A, and HHTP-DPB COF） are investigated using the grand canonical Monte Carlo （GCMC） simulations and the density functional theory （DFT）, respectively. The GCMC simulated results show that HHTP-DPB COF has the best performance for hydrogen storage, followed by BTP-COF, TP-COF, COF-18 A, and PPy-COE However, their adsorption amounts at room temperature are all too low to meet the uptake target set by US Department of Energy （US-DOE） and enable practical applications. The effects of pore size, surface area, and isosteric heat of hydrogen on adsorption amount are considered, which indicate that these three factors are all the important factors for determining the H2 adsorption amount. The chemisorptions of spiltover hydrogen atoms on these five COFs represented by the cluster models are investigated using the DFT method. The saturation cluster models are constructed by considering all possible adsorption sites for these cluster models. The average binding energy of a hydrogen atom and the saturation hydrogen storage density are calculated. The large average binding energy indicates that the spillover process may pro- ceed smoothly and reversibly. The saturation hydrogen storage density is much larger than the physisorption uptake of H2 molecules at 298 K and 100 bar （1 bar = 105 Pa）, and is close to or exceeds the 2010 US-DOE target of 6 wt% for hydrogen storage. This suggests that the hydrogen storage capacities of these COFs by spillover may be significantly enhanced. Thus 2D COFs studied in this paper are suitable hydrogen storage media by spillover.     

Design optimization of highly efficient spectrum-splitting and beam-concentrating diffractive optical element for lateral multijunction solar cells

Two improved algorithms are proposed to extend a diffractive optical element （DOE） to work under the broad spec- trum of sunlight. An optimum design has been found for the DOE, with a weighted average optical efficiency of about 6.8% better than that of the previous design. The optimization of designing high optical efficiency DOEs will pave the way for future designs of high-efficiency, low-cost lateral multijunction solar cells based on such a DOE.     

质子和中子有“远亲”了

美国能源部费米国家加速器实验室国际费米碰撞探测器（CDF）合作组的科学家23日说，他们利用Tevatron对撞机，成功地发现了两种罕见的粒子．经过鉴定，这两种粒子是最常见的质子和中子的“远亲”．     

国际次声监测研讨会

全面核禁试条约第三届全球次声监测工作研讨会于1997年8月25至28日在美国新墨西哥州西班牙式的古城圣菲举行．会议云集了中国、美国、法国、俄罗斯、阿根廷、澳大利亚等5大洲12个国家61位活跃在次声学科领域的研究人员、政府官员以及联合国临时技术秘书等要员，围绕着全球次声监测中的7个专题进行报告和讨论，它们依次为：欢声阵的设计和信号处理，次声阵性能和减噪设备；法国欢声监测系统，国际次声监测系统60个站网的能力模型，对流层风对长距离次声传播的影响，高空风对次声同性能的影响，渗透管的特性以及对次声监测的减噪作用，欢声减噪器；爆炸检测，声遥感技术对爆炸源能量的估计，小当量地下，地面和近地面爆炸远距离声传     

译后记

<正>现在发表的这份文件是美国粒子物理学术界对未来10至20年的规划——P5文件的缩写版,也是对美国能源部和自然科学基金会投资和项目拨款的建议指南。这份文件充分体现了美国粒子物理学术界对将来发展的理念。它的关键在于,首先,所有研究是以"发现"新物理为驱动力的,这包括发现新粒子,新相互作用,新物理规律乃至新物理原则;其次,它强调了美国在世界范围的学术领导作用,这些拨款要保证美     

磁热效应与磁冰箱

冰箱是日常生活中必不可少的家用电器，原来的普通冰箱大都以氟里昂为工作介质，采用气体压缩式制冷，这种致冷技术不仅工效低，噪声大，而且会排出大量的温室气体，对环境造成难以恢复的危害．能否找到一种更好的替代品呢72001年12月，美国能源部科研人员在艾奥瓦州立大学埃姆斯实验室制成了世界上第一台能在室温下工作的磁冰箱．这是一种利用铁磁性制冷工质进出磁场引起温度变化而在室温范围进行制冷的新方法，无污染、无噪音、使用寿命长，是21世纪最具发展前景的制冷技术．下面简要介绍一下磁制冷冰箱的工作原理．     

真没想到,热收缩膜离我们这么近

美国能源部科学办公室出版的《Accelerators for America’s Future》中有这样一段描述:感恩节能吃上新鲜肥嫩的烤火鸡,别忘了感恩粒子加速器,因为几十年来美国食品加工商一直使用经粒子加速器辐照交联处理后的塑料薄膜--热收缩膜来包装火鸡。热收缩膜?听起来陌生,却已深深渗透到我们的生活之中。     

Aggregation Behavior of Metal-Ethylene Complexes and Its Effect on Hydrogen Storage Capacity

The aggregation of Li, Ti decorated ethylene molecules and its effect on hydrogen storage capacity have been thoroughly studied using a first-principles calculation. The results indicate that the aggregation of C2H4-metal complexes substantially impacts on the hydrogen storage capacity. The aggregation of C2H4-Li reduces the hydrogen storage capacity greatly and makes the hydrogen storage capacity of C2H4-Li complexes hardly meet the demands of the U.S. DOE. The C2H4Ti2 dimers can uptake hydrogen as much as 10 wt%, which suggests that the C2H4Ti2 dimer can be a promising candidate for practical applications.     

"冷聚变"重新获得美国能源部少量支持

1989年，S.庞斯（stanley Pons）和M.弗雷斯曼（Martin Fleischmann）宣布发现了“冷聚变”．2004年12月1日，美国能源部召开了对“冷聚变”的评审会，评审15年来从低能核反应获得能源的进展．结论是：15年来没有更多的令人信服的证据．     

磁冰箱的原理

 2001年12月7日，美国能源部在艾奥瓦州立大学埃姆斯实验室的科研人员制成了世界上第一台能在室温下工作的磁冰箱，他利用铁磁性制冷工质进出磁场制冷，其效率比普通冰箱高30%以上，且无污染、无噪音、使用寿命长，是一种绿色环保的、极具发展前景的制冷技术，我国也已将“磁制冷冰箱项目”列入国家863科技计划。下面简要介绍一下磁制冷冰箱的工作原理。