Bio-Inspired Aggregation Control of Carbon Nanotubes for Ultra-Strong Composites

High performance nanocomposites require well dispersion and high alignment of the nanometer-sized components, at a high mass or volume fraction as well. However, the road towards such composite structure is severely hindered due to the easy aggregation of these nanometer-sized components. Here we demonstrate a big step to approach the ideal composite structure for carbon nanotube (CNT) where all the CNTs were highly packed, aligned, and unaggregated, with the impregnated polymers acting as interfacial adhesions and mortars to build up the composite structure. The strategy was based on a bio-inspired aggregation control to limit the CNT aggregation to be sub 20--50 nm, a dimension determined by the CNT growth. After being stretched with full structural relaxation in a multi-step way, the CNT/polymer (bismaleimide) composite yielded super-high tensile strengths up to 6.27--6.94 GPa, more than 100% higher than those of carbon fiber/epoxy composites, and toughnesses up to 117--192 MPa. We anticipate that the present study can be generalized for developing multifunctional and smart nanocomposites where all the surfaces of nanometer-sized components can take part in shear transfer of mechanical, thermal, and electrical signals

就业机会是政府必须提供的一种公共产品吗?

就业机会不具备公共产品的非竞争性、非排他性的基本特征,它是私人产品;在市场经济里,就业机会主要是由市场或企业家提供的,而不是政府;尽管政府可以通过提供法律制度、基础设施以及宏观政策等促进就业,但提供就业机会的基本力量仍然是市场。长时间的政府非理性干预以及市场经济体制不完善是现阶段我国失业的主要原因

The EFFect of Preparation Conditions on the Properties of SnO_2/Si

研究了沉积温度、SnCl4溶液的浓度、掺Pd等对SnO2/SI光电压的影响，测量了SnO2/SI的光电压谱，得出最佳的制备条件，进行了有关计算和分析。Some tin oxide Films are deposited by CVD method on single crystal silicons.The eFFect of diFFerent deposition conditions, such as diFFerent substrate temperatures, SnCI4 solutions and Pd doping,on photovoltaic properties of the Films are studied.The best preparation conditions are obtained.Relative parameters is calculated From the photovoltaic spectra.国家自然科学基金;福建省自然科学基

An Electrochemical Study of DDTC Adsorption Jamesonite

　通过循环伏安法、交流阻抗法研究了二乙基二硫代氨基甲酸钠(以D表示)与脆硫锑铅矿的相互作用.在不同的电位条件下呈现出不同的电极过程.从-178～472mV(相对于标准氢电极),脆硫锑铅矿表面主要是DDTC,PbD2,S0等疏水性物质的吸附,界面电容也比较小.当电极电位高于472mV时,由于PbD2,S0等疏水性物质被氧化成Pb2+,SO32-,SO42-,PbSO4等亲水性产物,脆硫锑铅矿表面是亲水的.由此推测用DDTC做捕收剂浮选脆硫锑铅矿的电位范围为-178～472mV,最佳电位范围为60～222mV.The interactions of jamesonite with diethyl dithiocarbamate (DDTC) were studied by AC impedance measurement and cyclic voltammetry. Several electrode processes under different potential conditions were observed. There mainly is the absorption of hydrophobic DDTC. PbD_2, S~0 etc on the surface of jamesonite mineral from -178 mV to 472 mV (vs. SHE) and the interfacial capacitance also is small. When the electrode potential is over 472 mV, the surface of jamesonite mineral is of hydrophilicity due to the fact that hydrophobic PbD_2,S~0 etc are oxidized into hydrophilic products such as Pb~(2+), SO_3~(2-) ,SO_4~(2-), PbSO_4. So it was deduced that the potential range of jamesonite flotation using diethyl dithiocarbmate as a collector is from -178 mV to 472 mV, and its optimum potential range is between 122 mV and 222 mv due to the passive action by the hydrophobic species.作者联系地址：中南大学资源加工与生物工程学院,中南大学资源加工与生物工程学院,中南大学资源加工与生物工程学院,中南大学资源加工与生物工程学院 湖南长沙410083 衡阳师范学院化学与材料科学系湖南衡阳421008 ,湖南长沙410083 ,湖南长沙410083 ,湖南长沙410083Author's Address: *1,2, HU Yue-hua~1, QIU Guan-zhou~1, QIN Wen-qing~1 1.School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China 2.Department of Chemistry and Material Science, Hengyang Normal University, Hengyang 421008, Chin

系统性金融风险与预算软约束

中国非金融企业的高杠杆率是整个国民经济杠杆率持续保持高位的主要推动力量。其中,非金融国有企业的杠杆率最高,是非金融企业中发生金融风险的主要所在。究其原因,非金融国企杠杆率高企在于:(1)充裕的流动性;(2)债务融资为主的融资结构;(3)影子银行规模的过度扩张;(4)国有企业的软预算约束和向国有企业倾斜的贷款分配机制。通过对不同领域的金融风险的表现分析,本文认为中国系统性金融风险的根源在于地方政府(国有企业)的预算软约束。在此基础上,本文通过中国季度宏观经济模型(CQMM),在国有企业预算软约束和预算硬约束两种不同情境下分别模拟分析逐步收紧货币供应量的数量型"去杠杆"政策可能产生的宏观经济效应,模拟结果显示,在国有企业预算软约束条件下降低M2增速无法实现预期的政策目标。基于上述政策模拟结果,课题组建议:必须转变以保增长为中心的发展思路;尽快建立现代财税制度,形成地方政府(国有企业)的预算硬约束;下决心从制度上消除土地财政;逐步收回超发的货币;合理控制货币总供应量,充分利用金融手段降低非金融国有企业的负债率;加大对影子银行的监管力度,回归金融的优化经济资源配置和利用职能。国家社会科学基金重大项目“需求结构转换背景下提高消费对经济增长贡献研究”(项目编号:15ZDC011)；国家社会科学基金一般项目“知识产权保护对中国企业创新和企业绩效的影响机理及政策选择研究”(项目编号:17BJY086)；中央高校基本科研业务费专项资金资助“中国实践背景现代宏观经济理论与政策”(项目编号:20720151037)；教育部哲学社会科学重大课题攻关项目“地方债发行机制与监管研究”(项目编号:14JZD011)

发展中国家资本项目可兑换的模式比较及其借鉴

由于初始国情、经济形势和监管能力的差异,发展中国家资本项目可兑换开放的速度和顺序也不尽相同,形成了与之相关的不同模式。通过比较和借鉴,本文认为渐进式、正向式模式应该是我国资本项目可兑换开放的现实选择。同时从国际收支的角度提出了相应的政策建议,并指出对资本项目开放的设想不应该有确切的时间表

2008年持续低温降雪冻雨对梁子湖流域鸟类的影响调查

2008年1月,梁子湖流域遭遇历时罕见的持续低温降雪冻雨极端天气,304km2梁子湖冰冻封湖15 d。地面持续冰雪覆盖,导致鸟类生境结构破坏,生境资源不可利用,最终因长时间食物匮乏和冷害的双重影响出现严重灾害性死亡。涉及鸟类22科42种,流域内数量损失30万～40万只