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71.
Summary This paper treats new effects, such as transcritical bifurcation and extinction, exhibited by the solution branches of buckled states of nonlinearly elastic columns. The general models used are intimately related to the three-dimensional theory of nonlinear elasticity. These new effects are caused by the interaction of the nonlinearity of material response, the lack of symmetry in the cross-section, the nature of boundary conditions, and the nonuniformity of the rod. Although a variety of sophisticated analytic tools are used to treat local and global branching of solutions, the main emphasis is placed on the mechanics that underlies the form of the governing equations.Dedicated to Prof. Klaus Kirchgässner on the occasion of his sixtieth birthday  相似文献   
72.
Bounded knapsack sharing   总被引:1,自引:0,他引:1  
A bounded knapsack sharing problem is a maximin or minimax mathematical programming problem with one or more linear inequality constraints, an objective function composed of single variable continuous functions called tradeoff functions, and lower and upper bounds on the variables. A single constraint problem which can have negative or positive constraint coefficients and any type of continuous tradeoff functions (including multi-modal, multiple-valued and staircase functions) is considered first. Limiting conditions where the optimal value of a variable may be plus or minus infinity are explicitly considered. A preprocessor procedure to transform any single constraint problem to a finite form problem (an optimal feasible solution exists with finite variable values) is developed. Optimality conditions and three algorithms are then developed for the finite form problem. For piecewise linear tradeoff functions, the preprocessor and algorithms are polynomially bounded. The preprocessor is then modified to handle bounded knapsack sharing problems with multiple constraints. An optimality condition and algorithm is developed for the multiple constraint finite form problem. For multiple constraints, the time needed for the multiple constraint finite form algorithm is the time needed to solve a single constraint finite form problem multiplied by the number of constraints. Some multiple constraint problems cannot be transformed to multiple constraint finite form problems.  相似文献   
73.
We consider algebras with one binary operation · and one generator (monogenic) and satisfying the left distributive lawa·(b·c)=(a·b)·(a·c). One can define a sequence of finite left-distributive algebrasAn, and then take a limit to get an infinite monogenic left-distributive algebraA. Results of Laver and Steel assuming a strong large cardinal axiom imply thatAis free; it is open whether the freeness ofAcan be proved without the large cardinal assumption, or even in Peano arithmetic. The main result of this paper is the equivalence of this problem with the existence of a certain algebra of increasing functions on natural numbers, called anembedding algebra. Using this and results of the first author, we conclude that the freeness ofAis unprovable in primitive recursive arithmetic.  相似文献   
74.
Hearing sensitivity was measured in a bottlenose dolphin before and after exposure to an intense 20-kHz fatiguing tone in three different experiments. In each experiment, hearing was characterized using both the auditory steady-state response (ASSR) and behavioral methods. In experiments 1 and 2, ASSR stimuli consisted of seven frequency-modulated tones, each with a unique carrier and modulation frequency. The tones were simultaneously presented to the subject and the ASSR at each modulation rate measured to determine the effects of the sound exposure at the corresponding carrier frequency. In experiment 3 behavioral thresholds and ASSR input-output functions were measured at a single frequency before and after three exposures. Hearing loss was frequency-dependent, with the largest temporary threshold shifts occurring (in order) at 30, 40, and 20 kHz. ASSR threshold shifts reached 40-45 dB and were always larger than behavioral shifts (19-33 dB). The ASSR input-output functions were represented as the sum of two processes: a low threshold, saturating process and a higher threshold, linear process, that react and recover to fatigue at different rates. The loss of the near-threshold saturating process after exposure may explain the discrepancies between the ASSR and behavioral threshold shifts.  相似文献   
75.
Transformation of 2D Au nanoparticle (NP) arrays into large scale, ordered, and oriented nanorod/nanowire arrays supported on a transferrable polymer film has been accomplished. E-beam irradiation followed by room temperature aging of a suspended Au NP/polymethylmethacrylate (PMMA) polymer close packed monolayer results in one-dimensional nanoparticle aggregation, reorientation, and sintering into a high density array of oriented Au nanowires with coherent single-crystal-like interfaces. Molecular dynamics simulations of alkane-thiol capped Au NPs, interacting through the Vincent potential and undergoing 2D Poisson compression, account semiquantitatively for the qualitative features of the transformation. This fabrication approach should be extendable to directing 1D aggregation of highly anisotropic nanostructures in arbitrary NP systems.  相似文献   
76.
The first targeted inhibitors of an essential M. tuberculosis cell wall lipase, Rv3802c, are described. Lead compounds exhibited nanomolar inhibition of the enzyme, and encouraging antibacterial activity against M. tuberculosis in vitro, supporting Rv3802c as a novel TB drug target.  相似文献   
77.
Synthesis and self-assembly of structurally related mercapto- and isocyanoazulenes, including novel 2-mercapto-1,3-dicyanoazulene (4) and 2-isocyano-1,3-dicyanoazulene (5), are reported. Exposing 5 adsorbed on Au(111) to a solution of 4 displaces the isocyanoazulene monolayer with that of the mercaptoazulene as judged by ν(C≡N) signatures of these films.  相似文献   
78.
We present quantitative analysis of image sequences of multi-stream injection nozzle flows with several different injection geometries in an experiment simulating mixing in a chemical oxygen-iodine laser. To visualize mixing, image sequences were acquired with planar laser-induced fluorescence (PLIF) in iodine that was injected into the main flow. The injection nozzle consisted of a slot, ejector, and injector block, with rows of ejector and injector holes along the slot length. The ejector flow exits in an underexpanded state so that upon expanding it forces the slot and injector flows together to enhance mixing. For this study, the diameter and geometry of ejector holes were varied to assess their effect on mixing. Two configurations of ejector holes were used, each with two different diameters for a total of four cases with data collected at downstream stations. We carry out a quantitative mixing analysis for these configurations, using two methods to quantify the mixing. The first method considers the statistics of the PLIF image intensity histograms, which are bimodal for poorly-mixed flows and have a single peak in well-mixed flows. The second method quantifies the properties of the mixing interface. Our analysis shows that two injection schemes significantly enhance mixing by stretching the mixing interface.  相似文献   
79.
80.
An efficient synthetic route to 1,6- and 1,7-dibromo-3-aminoisoquinoline was devised. These intermediates served as ideal templates for the preparation of 3-aminoisoquinoline analogues functionalized at C(6) or C(7).  相似文献   
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