Extracting nanobelt mechanical properties from nanoindentation

A three-spring-in-series model is proposed for the nanobelt (NB) indentation test. Compared with the previous two-spring-in-series model, which considers the bending stiffness of atomic force microscope cantilever and the indenter/NB contact stiffness, this model adds a third spring of the NB/substrate contact stiffness. NB is highly flexural due to its large aspect ratio of length to thickness. The bending and lift-off of NB form a localized contact with substrate, which makes the Oliver-Pharr method [W. C. Oliver and G. M. Pharr, J. Mater. Res. 7, 1564 (1992)] and Sneddon method [I. N. Sneddon, Int. J. Eng. Sci. 3, 47 (1965)] inappropriate for NB indentation test. Because the NB/substrate deformation may have significant impact on the force-indentation depth data obtained in experiment, the two-spring-in-series model can lead to erroneous predictions on the NB mechanical properties. NB in indentation test can be susceptible to the adhesion influence because of its large surface area to volume ratio. NB/substrate contact and adhesion can have direct and significant impact on the interpretation of experimental data. Through the three-spring-in-series model, the influence of NB/substrate contact and adhesion is analyzed and methods of reducing such influence are also suggested. (C) 2010 American Institute of Physics. [doi:10.1063/1.3432748]

Non-relativistic conformal symmetries in fluid mechanics

The symmetries of a free incompressible fluid span the Galilei group, augmented with independent dilations of space and time. When the fluid is compressible, the symmetry is enlarged to the expanded Schrodinger group, which also involves, in addition, Schrodinger expansions. While incompressible fluid dynamics can be derived as an appropriate non-relativistic limit of a conformally invariant relativistic theory, the recently discussed conformal Galilei group, obtained by contraction from the relativistic conformal group, is not a symmetry. This is explained by the subtleties of the non-relativistic limit.

Molybdenum L-shell X-ray production by 350-600 keV Xeq+ (q=25-30) ions

Molybdenum L-shell X-rays were produced by Xeq+ (q = 25-30) bombardment at low energies from 2.65 to 4.55 keV/amu (350-600 keV). We observed a kinetic energy threshold of Mo L-shell ionization down to 2.65-3.03 keV/amu (350-400 keV). The charge state effect of the incident ions was not observed which shows that the ions were neutralized, reaching an equilibrium charge state and losing their initial charge state memory before production of L-shell vacancies resulted in X-ray production. The experimental ionization cross sections were compared with those from Binary Encounter Approximation theory. Taking into account projectile deflection in the target nuclear Coulomb field, the ionization cross section of Mo L-shell near the kinetic energy threshold was well described. (C) 2010 Published by Elsevier B.V.

Design optimization of the APF DTL in the SSC-linac

A linear accelerator as a new injector for the SSC (Separated Sector Cyclotron) of the HIRFL (Heavy ton Research Facility Lanzhou) is being designed. The DTL (Drift-Tube-Linac) has been designed to accelerate U-238(34+) from 0.140 MeV/u to 0.97 MeV/u. To the first accelerating tank which accelerates U-238(34+) to 0.54 MeV/u, the approach of Alternating-Phase-Focusing (APF) is applied. The phase array is obtained by coupling optimization software Dakota and beam optics code LINREV. With the hybrid of Multi-objective Genetic Algorithm (MOGA) and a pattern search method, an optimum array of asynchronous phases is determined. The final growth, both transversely and longitudinally, can meet the design requirements. In this paper, the deign optimization of the APF DTL is presented.

《景观生态学原理与方法》简介

由国际著名景观生态学家、国际生态学会秘书长、意大利Ｌｕｎｉｇｉａｎａ自然博物馆主任法瑞纳（ＡｌｍｏＦａｒｉｎａ）博士撰写的又一部景观生态学力作《景观生态学原理与方法》（Ｐｒｉｎｃｉｐｌｅａｎｄｍｅｔｈｏｄｓｉｎｌａｎｄｓｃａｐｅｅｃｏｌｏｇｙ）已于１...

长白山地区蒙古栎光合特性

基于单叶尺度上的光强-光合响应以及CO2-光合响应测定,对长白山地区蒙古栎成树和幼树的光合特性分别进行了研究.结果表明,蒙古栎成树的光补偿点Lcp为21μmol/(m2·s),光饱和点Lsp为1564μmol/(m2·s),表观量子效率α为0·045;幼树的Lcp、Lsp、α以及CO2补偿点、饱和点分别为29μmol/(m2·s)、1581μmol/(m2·s)、0·049、73μmol/mol、625μmol/mol.幼树和成树具有相似的光响应特征,但前者的光合同化能力要高于后者.蒙古栎具有典型的喜光性,但对高光的利用效率要低于弱光.

脲酶抑制剂/硝化抑制剂对植稻土壤中尿素N行为的影响

采用自制根盒试验 ,主要研究了脲酶抑制剂氢醌 (HQ)、硝化抑制剂双氰胺 (DCD)及二者组合对离水稻根际不同距离处 NH+ 4-N和 NO- 3 -N分布的影响。结果表明 ,DCD及其与 HQ组合均能显著促进稻株地上部分生长 ,始终显著降低水稻根际与近根际土中 NH+ 4-N含量直至施肥后 60 d。施肥后 2 0 d时 ,DCD及其与 HQ组合可使非根际土中 NH+ 4-N含量显著增加。随后 ,却出现相反现象。施肥后 2 0 d时 ,距根际不同距离的土壤中 ,配施 DCD或 DCD+HQ处理均能显著降低NO- 3 -N含量。随后 ,近根际和非根际仍保持上述现象直至施肥后 40 d;同未施 DCD处理相比 ,根际土壤却较早出现NO- 3 -N含量高峰 ,正好与水稻 N营养需求时期相一致。因此 ,DCD及其与 HQ组合可减少水稻根际环境下尿素 N损失潜势。通过不种稻土壤和距根际 3 cm处的土壤中尿素无机氮形态分布的差异 ,充分显示了研究水稻根际土壤氮素转化及相关抑制剂对其影响时 ,以取离根际 3 cm外的土壤作为非根际明显优于不种稻土壤。

Guest inducing p-sulfonatocalix[4] arene into three-dimensional capsule architecture and a mixed A-B double layer framework

The reactions of sodium p-sulfonatocalix[4]arene (Na5L) and terbium/europium(III) chloride in the presence of pyrazine-N,N'-dioxide (PNNO) in aqueous solutions gave the crystalline complexes 1 and 2. Both structures contain molecular capsules of p-sulfonatocalix[4] arene with PNNO as guest molecules in the cavity of the calix[4]arenes. The molecular capsules are connected through sodium and terbium (or europium) centers forming a three-dimensional framework.