以LCD为目标的自动定焦判据选择

在光学综合自动测量中 ,使用液晶显示屏作为分划板可以大大简化结构 ,提高效率 ,真正地实现自动测量。由于液晶显示具有对比度低、噪声大等特点 ,所以根据液晶的这些特点以及图像处理和CCD信号接收的特点选择两种适用的判据进行了分析和试验比较 ,并给出了结果。结果表明 ,这两种判别函数都适用于以液晶显示屏为目标和用图像处理方法进行光学参数测量的系统 ,其中锐度判别函数更优于信息熵判别函数 ,前者具有更好的抗干扰性和稳定性 ,而且其判定结果更接近目视清晰度判别     

Towards a naturally small cosmological constant from branes in 6D supergravity

We investigate the possibility of self-tuning of the effective 4D cosmological constant in 6D supergravity, to see whether it could naturally be of order 1/r⁴ when compactified on two dimensions having Kaluza–Klein masses of order 1/r. In the models we examine supersymmetry is broken by the presence of non-supersymmetric 3-branes (on one of which we live). If r were sub-millimeter in size, such a cosmological constant could describe the recently-discovered dark energy. A successful self-tuning mechanism would therefore predict a connection between the observed size of the cosmological constant, and potentially observable effects in sub-millimeter tests of gravity and at the Large Hadron Collider. We do find self-tuning inasmuch as 3-branes can quite generically remain classically flat regardless of the size of their tensions, due to an automatic cancellation with the curvature and dilaton of the transverse two dimensions. We argue that in some circumstances six-dimensional supersymmetry might help suppress quantum corrections to this cancellation down to the bulk supersymmetry-breaking scale, which is of order 1/r. We finally examine an explicit realization of the mechanism, in which 3-branes are inserted into an anomaly-free version of Salam–Sezgin gauged 6D supergravity compactified on a 2-sphere with nonzero magnetic flux. This realization is only partially successful due to a topological constraint which relates bulk couplings to the brane tension, although we give arguments why these relations may be stable against quantum corrections.     

Revêtements modérés et groupe fondamenttal de graphe de groupes

Let R be a discrete complete valuation ring, with algebraically closedresidue field. Let X be a semi-stable R-curve, with smooth generic fibre. In this paper we study tame coverings of X.     

Flutter instability in imperfect structural systems

The periodic oscillations of discrete structural systems with follower-force loading are studied in the region of the critical point. The case in which small initial geometric imperfections exist in the structure is also examined. Flutter instability is found to be much less sensitive to initial imperfections than is static instability. Critical loads are destabilized (or stabilized) in either a linear or parabolic fashion with imperfection amplitude. The postcritical characteristics of the flutter exhibited cannot be altered by initial imperfections.     

Generalized covering designs and clique coverings

Inspired by the “generalized t‐designs” defined by Cameron [P. J. Cameron, Discrete Math 309 (2009), 4835–4842], we define a new class of combinatorial designs which simultaneously provide a generalization of both covering designs and covering arrays. We then obtain a number of bounds on the minimum sizes of these designs, and describe some methods of constructing them, which in some cases we prove are optimal. Many of our results are obtained from an interpretation of these designs in terms of clique coverings of graphs. © 2011 Wiley Periodicals, Inc. J Combin Designs 19:378‐406, 2011     

Solvent Effects on the piezochromism of molybdenum(IV) and tungsten(IV) anions [M(CN)3O(diimine)]−

Solvatochromism of the [Mo(CN)₃O(phen)]⁻ ion has been studied. Solvent effects on pressure dependence (up to 1.25 kbar) of wavelengths of maximum absorption for charge-transfer bands of several molybdenum(IV) and tungsten(IV) complexes, [M(CN)₃O(diimine)]⁻ (M = Mo or W), are described. The effects of applied pressure are larger for less polar unstructured solvents than for highly polar hydrogen-bonded solvents. This revised version was published online in June 2006 with corrections to the Cover Date.     

On the importance of specific solvent effects in electron trransfer reactions

The intramolecular electron transfer reaction within the binuclear complex formed between tetraamminepyrazinecarboxylatocobalt(III) and aquopentacyanoferrate(II) ions is studied in various binary aqueous media at different temperatures. Results could not be explained on the basis of a primitive model. Experimental data were fitted by using a multiparameter regression which shows the important role played by specific interactions on reactivity. © 1993 John Wiley & Sons, Inc.     

Solvation of molybdenum(O)-diimine-tetracarbonyl complexes

Summary Solubilities of molybdenum(O)-diimine-tetracarbonyl complexes containing pyridyl-primary amine Schiff base or substituted 1,4-diazabutadiene ligands are reported, for a variety of non-aqueous solvents, and for toluene + heptane, toluene + methanol, and methanol-rich methanol + water mixed solvents. Enthalpies and entropies of solution for several of these complexes in a selection of solvents have been derived from temperature variation of solubilities. These results, together with new data on solvent effects on infrared and n.m.r. (¹H, ¹³C, ⁹⁵Mo) spectra and published data on solvatochromism of this family of compounds, are discussed in relation to solvation of these complexes in pure and mixed solvents.