Volatile metal complexes

Fundamental investigations of the chemical and physical properties of metal beta-diketonate complexes have revealed unusual volatility, as well as solvolytic and thermal stability and solubility in organic solvents. Certain general rules describing the volatility of metal beta-diketonates on the basis of ligand shell character and metal ion size have arisen from extensive gas chromatographic and vapor pressure studies. Several practical applications of volatile beta-diketonates teke advantage of their special properties. In ultratrace metal analysis by gas chromatography, use of these chelates has allowed the detection of smaller amounts of certain metals than can be detected by any other analytic method. Certain rare earth beta-diketonates have been found useful as antiknock additives in gasoline and as catalysts for the removal of carbonaceous deposits from the combustion chambers of internal combustion engines.     

Intermetallic compounds for high-temperature structural use

The next generation of efficient turbines and engines will require materials that can withstand operating temperatures approaching 2000 degrees C. Intermetallic compounds with high melting temperatures are candidates for this application, but the obstacle of their limited ductility must first be overcome. Because the available data on these materials is limited, a survey of the effects of chemistry and crystal structure must be performed. With the use of melting temperature and density as figures of merit, the most likely candidates have been identified for preliminary screening.     

长输管道防腐层的选择

综述了目前长输管道防腐层现状及常用防腐层材料的特点。从管道周围介质的腐蚀性、环境及防腐层施工等方面,分析了外界条件与防腐层失效的关系。防腐层失效的形式主要有：防腐层的剥离、破裂、穿孔及变形。分析了导致防腐失效的原因,指出产生剥离的原因与防腐层性质、钢管表面的处理,阴极保护电流有关;而破裂与土壤应力,外力及材料老化有关;穿孔是施工不当或外力造成的,介绍并评价了国内外常用的几种防腐层的性能特点,提出长     

加氢反应器裙座支撑结构的有限元分析

加氢反应器裙座支撑结构部位的机械应力和温差应力均较大,应力状况较为恶劣。对加氢反应器裙座支撑局部结构进行了温度场分析,采用间接分析法将所得温度场施加到结构上进行热应力分析。根据不同温度点的单向拉伸试验得到材料在各温度点下的应力一应变曲线,采用线弹性和弹塑性两种材料本构分别对加氢反应器裙座支撑结构进行有限元计算。将计算结果进行对比分析,表明弹塑性有限元计算结果更加精确。此外,根据ASMEVIII-22007关于两种方法的失效评定内容对该结构局部失效的可能性进行了评定计算。对比研究表明,基于线弹性有限元计算结果虽可用于工程设计,但其最大应力部位与实际情况并不一致,因此分析设计计算方法仍有改进的空间。（图6,表1,参10）     

如何提高输油泵站柴油机组的使用寿命

输油泵站柴油机组使用寿命的长短，不但影响着机组的利用率和维护保养费用，而且影响着管道的安全运行和输送任务的完成。从柴油机组零部件的失效率、结构设计因素、使用管理方面着手分析，就柴油机摩擦副的耐腐性、零部件材料质量、热处理方法、表面加工质量、零部件之间的配合性质等提出了技术要求；在管理方法，提出了为机组建档、做日报工作、三化一位的科学管理方法；在使用方面，给出了初动转磨合期的操作程序及使用方法，并对     

不同墙体日光温室保温性能研究

为了确定合理的日光温室后墙材料与结构,2012年分别在睢宁、赣榆建造了不同墙体(普通空心砖墙、复合异质墙体、夹芯板墙体)构型的日光温室,并研究了不同墙体日光温室的增温、保温性能。结果表明:普通空心砖墙蓄热能力强,夜间保温效果好,但白天增温慢;夹芯板墙体热阻值大,白天升温较快,利于提高温室的最高温度,但夜间放热能力较弱,不利于夜间保温;复合异质墙体具有较好的热阻和蓄热能力,增温、保温性最佳。为使日光温室冬季获得较好增温保温效果,从节约成本方面考虑,建议选择1 cm内粉+24 cm空心砖+24 cm空心砖+10 cm聚苯乙烯泡沫塑料板+1 cm外粉为墙体的温室。     

埋地热油管道启输热力数值模拟

在综合考虑预热介质，管道，管道覆盖层以及半无穷大土壤的情况下，提出了埋地热油管道启输传热的数学模型，并在该模型中，将土壤物性参九视为随温度变化的函数，应用保角变换将半无究大土壤区域变换成有限矩形区域。由Keller盒式积分法构造出了问题的差分格式，采用广义阻尼牛顿－拉夫逊法求解非线性差分方程组，得到了问题的数值解，并由算例验证了所述方法的正确性。     

Quasars, blazars, and gamma rays

Before the launch of the Compton Gamma Ray Observatory (CGRO), the only source of >100-megaelectron volt (MeV) gamma radiation known outside our galaxy was the quasar 3C 273. After less than a year of observing, 13 other extragalactic sources have been discovered with the Energetic Gamma Ray Experiment Telescope (EGRET) on CGRO, and it is expected that many more will be found before the full sky survey is complete. All 14 sources show evidence of blazar properties at other wavelengths; these properties include high optical polarization, extreme optical variability, flat-spectrum radio emission associated with a compact core, and apparent superluminal motion. Such properties are thought to be produced by those few, rare extragalactic radio galaxies and quasars that are favorably aligned to permit us to look almost directly down a relativistically outflowing jet of matter expelled from a supermassive black hole. Although the origin of the gamma rays from radio jets is a subject of much controversy, the gamma-ray window probed by CGRO is providing a wealth of knowledge about the central engines of active galactic nuclei and the most energetic processes occurring in nature.     

三种主要管道覆盖层的应用比较

介绍了三种最常用的管道覆盖层的性能,即煤焦油类覆盖层,熔结环氧覆盖层和聚烯烃覆盖层,对这三种覆盖层的应用及适用范围进行了分析比较。分析了具体管道工程项目选择管道涂料时应考虑的诸多因素,并对这三种涂料在覆盖层特性方面进行了综合评价。     

Thermoclines: a solar thermal energy resource for enhanced hydroelectric power production

The solar thermal energy stored in hydroelectric reservoir thermoclines is very large and greatly exceeds the gravitational hydroenergy of the surface water, even after limitations arising from the second law of thermodynamics have been taken into account. Greatly enhanced power production can be obtained at present hydroelectric facilities if heat engines are adapted to exploit this large thermal energy resource.     

O2 activation by nonheme iron complexes: A monomeric Fe(III)-Oxo complex derived from O2

Iron species with terminal oxo ligands are implicated as key intermediates in several synthetic and biochemical catalytic cycles. However, there is a dearth of structural information regarding these types of complexes because their instability has precluded isolation under ambient conditions. The isolation and structural characterization of an iron(III) complex with a terminal oxo ligand, derived directly from dioxygen (O2), is reported. A stable structure resulted from placing the oxoiron unit within a synthetic cavity lined with hydrogen-bonding groups. The cavity creates a microenvironment around the iron center that aids in regulating O2 activation and stabilizing the oxoiron unit. These cavities share properties with the active sites of metalloproteins, where function is correlated strongly with site structure.     

隐形网页资源产生原因与开发利用

隐形网页资源是因特网上重要的信息资源,充分高效地利用这些资源是广大网络用户非常重视和急需解决的问题。文章对隐形网页的现状、隐形网页产生的原因、研究隐形网页重要性等方面进行了多角度、全方位的论述。最后重点探讨了隐形网页资源开发利用的措施和途径。     

Conducting organic materials

Some of the current directions of scientific research on electrically conducting organic solids are reviewed. Both molecular charge transfer salts and polymers are included, with emphasis on the present level of understanding of the novel solid-state properties of these materials in terms of their chemistry and structure. For the charge transfer salts the various types of metal-to-insulator phase transitions which dominate the properties of most of these materials are discussed. Also described are the superconducting and magnetic states which have been found recently. In the case of the polymers the chemistry and physics of the conduction mechanism is examined and contrasted with that of their classical inorganic counterparts.     

Polarized gamma-ray emission from the crab

Pulsar systems accelerate particles to immense energies. The detailed functioning of these engines is still poorly understood, but polarization measurements of high-energy radiation may allow us to locate where the particles are accelerated. We have detected polarized gamma rays from the vicinity of the Crab pulsar using data from the spectrometer on the International Gamma-Ray Astrophysics Laboratory satellite. Our results show polarization with an electric vector aligned with the spin axis of the neutron star, demonstrating that a substantial fraction of the high-energy electrons responsible for the polarized photons are produced in a highly ordered structure close to the pulsar.     

High-temperature structural ceramics

The unique properties of ceramics based on silicon carbide and silicon nitride make them prime candidates for use in advanced energy conversion systems. These compounds are the bases for broad families of engineering materials, whose properties are reviewed. The relationships between processing, microstructure, and properties are discussed. A review and assessment of recent progress in the use of these materials in high-temperature engineering systems, and vehicular engines in particular, is presented.     

Scanning tunneling microscopy and atomic force microscopy: application to biology and technology

The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are scanning probe microscopes capable of resolving surface detail down to the atomic level. The potential of these microscopes for revealing subtle details of structure is illustrated by atomic resolution images including graphite, an organic conductor, an insulating layered compound, and individual adsorbed oxygen atoms on a semiconductor. Application of the STM for imaging biological materials directly has been hampered by the poor electron conductivity of most biological samples. The use of thin conductive metal coatings and replicas has made it possible to image some biological samples, as indicated by recently obtained images of a recA-DNA complex, a phospholipid bilayer, and an enzyme crystal. The potential of the AFM, which does not require a conductive sample, is shown with molecular resolution images of a nonconducting organic monolayer and an amino acid crystal that reveals individual methyl groups on the ends of the amino acids. Applications of these new microscopes to technology are demonstrated with images of an optical disk stamper, a diffraction grating, a thin-film magnetic recording head, and a diamond cutting tool. The STM has even been used to improve the quality of diffraction gratings and magnetic recording heads.     

Nanominerals, mineral nanoparticles, and Earth systems

Minerals are more complex than previously thought because of the discovery that their chemical properties vary as a function of particle size when smaller, in at least one dimension, than a few nanometers, to perhaps as much as several tens of nanometers. These variations are most likely due, at least in part, to differences in surface and near-surface atomic structure, as well as crystal shape and surface topography as a function of size in this smallest of size regimes. It has now been established that these variations may make a difference in important geochemical and biogeochemical reactions and kinetics. This recognition is broadening and enriching our view of how minerals influence the hydrosphere, pedosphere, biosphere, and atmosphere.     

An assessment of the performance and requirements for "adiabatic" engines

A review of research on low heat rejection engines, on cooperative efforts in the United States and abroad to incorporate ceramics in intermittent combustion engines, and on the use of ceramics in these engines is presented. The reduction of heat loss from the combustion chamber of diesel engines improves fuel efficiency only 3 or 4 percent. Some other gains may be possible from a smaller cooling system, recovery of exhaust energy, and improvements in aerodynamics. It is judged that designs of low heat rejection engines will have the greatest initial impact on armored combat vehicles. Organization, coordination, planning, and cooperation on R&D for the use of ceramics in intermittent combustion engines appear to be greater abroad than in the United States.     

Direct imaging of reconstructed atoms on TiO2 (110) surfaces

Determining the atomic structures of oxide surfaces is critical for understanding their physical and chemical properties but also challenging because the breaking of atomic bonds in the formation of the surface termination can involve complex reconstructions. We used advanced transmission electron microscopy to directly observe the atomic structure of reduced titania (TiO2) (110) surfaces from directions parallel to the surface. In our direct atomic-resolution images, reconstructed titanium atoms at the top surface layer are clearly imaged and are found to occupy the interstitial sites of the TiO2 structure. Combining observations from two orthogonal directions, the three-dimensional positioning of the Ti interstitials is identified at atomic dimensions and allows a resolution of two previous models that differ in their oxygen stoichiometries.     

电弧喷涂3Cr13强化秸秆压块机模块试验研究

针对秸秆压块机模块磨损失效问题,分析了模块失效机理,提出了采用电弧喷涂3Cr13丝材对秆压块机模块表面进行强化和修复新工艺。采用正交试验和极差分析法研究了喷涂电流、喷涂电压、喷涂距离、喷涂气压对涂层耐磨性的影响规律,优化了压块机模块电弧喷涂3Cr13工艺参数,测试了3Cr13涂层的摩擦系数。结果表明:涂层摩擦系数为0.36,远低于铸钢摩擦系数0.8,涂层具有优异的耐磨性。