Amazing ageing property and in situ comparative study of field emission from tungsten oxide nanowires

In this work, needle-shaping of tungsten oxide nanowires occurred during field emission characterization. Compared with nanowires with a flat apex, needle-shaped emitters showed a lower threshold field of 11.9 V μm(-1) for 1 mA cm(-2) and a higher emission current of 1120 μA at 16.2 V μm(-1). Most notably, the measured ageing current dramatically increased by more than four times until it slightly decreased, tending towards stability. In addition, the samples showed striking difference in their nonlinear Fowler-Nordheim plot before and after ageing tests. Selected area diffraction and transmission electron microscope characterizations were used to further study these amazing results.     

GISAXS analysis of 3D nanoparticle assemblies--effect of vertical nanoparticle ordering

We report on grazing-incidence small-angle x-ray scattering (GISAXS) study of 3D nanoparticle arrays prepared by two different methods from colloidal solutions-layer-by-layer Langmuir-Schaefer deposition and spontaneous self-assembling during the solvent evaporation. GISAXS results are evaluated within the distorted wave Born approximation (DWBA) considering the multiple scattering effects and employing a simplified multilayer model to reduce the computing time. In the model, particular layers are represented by nanoparticle chains where the positions of individual nanoparticles are generated following a model of cumulative disorder. The nanoparticle size dispersion is considered as well. Three model cases are distinguished-no shift between the neighboring chains (AA stacking), a shift equal to half of the mean interparticle distance (AB stacking) and random shift between the chains. The first two cases correspond to vertically correlated nanoparticle positions across different chains. A comparison of the experimental GISAXS patterns with the model cases enabled us to distinguish important differences between the 3D arrays prepared by the two methods. In particular, laterally ordered layers without vertical correlation of the nanoparticle positions were found in the nanoparticle multilayers prepared by the Langmuir-Schaefer method. On the other hand, the solvent evaporation under particular conditions produced highly ordered 3D nanoparticle assemblies where both laterally and vertically correlated nanoparticle positions were found.     

Electronic fingerprints of DNA bases on graphene

We calculate the electronic local density of states (LDOS) of DNA nucleotide bases (A,C,G,T), deposited on graphene. We observe significant base-dependent features in the LDOS in an energy range within a few electronvolts of the Fermi level. These features can serve as electronic fingerprints for the identification of individual bases in scanning tunneling spectroscopy (STS) experiments that perform image and site dependent spectroscopy on biomolecules. Thus the fingerprints of DNA-graphene hybrid structures may provide an alternative route to DNA sequencing using STS.     

Accurate measurement of magnesium content in alphaolefins by laser induced breakdown spectroscopy （LIBS） technique

In this paper,results are presented on first application of laser-induced breakdown spectroscopy(LIBS) technique for quantitative determination of Mg concentration in alpha-olefins. It is demonstrated that this technique gives accuracies in Mg concentrations which are comparable with those of traditional methods,as ICP-OES,in short times and without need for sample preparation. Limits of detection for Mg of the order of 500 ppb are demonstrated. Moreover,a brief discussion about the realization of proper calibration curves and the definition of the limit of detection(LOD) is reported.     

A glucose-specific metric to assess predictors and identify models

In diabetes, the mean square error (MSE) metric is extensively used for assessing glucose prediction methods and identifying glucose models. One limitation of this metric is that, by equally treating errors in hypo-, eu-, and hyperglycemia, it is not able to weight the different clinical impact of errors in these three situations. In this paper, we propose a new cost function, which overcomes this limitation and can be used in place of MSE for several scopes, in particular for assessing the quality of glucose predictors and identifying glucose models. The new metric called glucose-specific MSE (gMSE) modifies MSE with a Clark error grid inspired penalty function, which penalizes overestimation in hypoglycemia and underestimation in hyperglycemia, i.e., the most harmful conditions on a clinical perspective. From a mathematical point of view, gMSE retains sensitivity of MSE and inherits some of its important mathematical features, in particular it has no local minima, simplifying the optimization. This makes it suitable for model identification purposes also. First, the goodness of it is demonstrated by means of three experiments, designed ad hoc to evidence its sensitivity to accuracy, precision, and distortion in glucose predictions. Second, a prediction assessment problem is presented, in which two real prediction profiles are compared. Results show that the MSE chooses the worst clinical situation, while gMSE correctly selects the situation with less clinical risk. Finally, we also demonstrate that models identified minimizing gMSE are more accurate in potentially harmful situations (hypo- and hyperglycemia) than those obtained by MSE.     

X射线荧光光谱法测定海水中铀

本文讨论了X射线光谱测定海水中铀的方法。提出了两种富集铀的技术:①加铁(II)作载体,用1-吡咯烷二硫代氨基甲酸铵(APDC)蝥合试剂进行沉淀,②与APDC生成螯合物后,用活性炭吸咐。本文报道了用这两种富集方法测定海水中铀的最好pH范围及其它最佳条件。     

保加利亚铀矿勘探史例和新的铀矿勘探地区

保加利亚于1945年开始找铀,并于50年代后期发现了第一批铀矿床。1946年成立了保加利亚-苏联联合开发公司。经过45年的勘探,对整个保加利亚领土(11万km~3)均进行了盖格米勒计数器航空伽玛测量。对80％的领土进行了地面伽玛测量,总共打了1800多万米钻孔和640km的平巷工程。在45年期间由于进行了上述工作,结果共发现了35个矿床。其中某些矿床,如Buhovo、Eleshnitza和Momino可以说是矿区,由几个矿床组成。这些矿区是由中等规模矿床组成,已计算的储量为5000—20000tU。其余的32个矿床为小矿床,储量不超过5000tU。有7个矿床处于勘探阶段,14个正在开采,14个已采完。位于保加利亚西南部的2个水冶厂处理来自Buhovo脉型矿床的矿石和Eleshnitza砂岩型矿床的矿石。2个水冶厂的生产能力足以处理全部开采的矿石以及来自原地浸出的载铀树脂。在保加利亚原地浸出技术应用很广泛,7(?)的铀是用这一方法回收的。75％的储量赋存于砂岩型矿床中。从Buhovo、Partisanska Poliana、Beli Iskar、Smolian等脉型矿床中开采的是高品位矿石。保加利亚的铀储量、矿山和水冶厂的生产能力足以满足6个核电站(总装机容量3.54GW)对铀燃料的需要。     

英国南部内陆地区的噪声控制

所有的机器运行时均向外界传播能量,大部分能量以热的形式,偶尔以光的形式,极小部分以声的形式散逸出去。声音由各种压力波组成,压力波可以通过任何介质传送。声音由声强、频率(特性)、波长、渡形来定义。把工业生产产生的声音归为噪声,它是任意特性和品质的多种声音的组合。     

Application wavelet of the analysis for identification of acoustic issue’s signals

Acoustic issue at deformation and destruction of materials carries initself weight of theinformation onthe physical processes happeningin structure of a material , mechanisms ,to energy of destruction,intensi-ty ,speed of deformation,etc . The Majority of researches inthe given areais devoted to the analysis of setof signals during tests of materials and designs .Few works are devoted to the analysis of structure of indi-vidual signals with the purpose of identification origin.It is connected …     

尾矿发泡输送技术

泡沫技术对地面尾矿库尾砂处理与充填的创新提供了可能性 ,它具有费用低、环境安全之特点 ,是一种替代传统方法的尾砂处理技术