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51.
52.
Experimental investigations of the functional morphology of dragonfly wings 总被引:1,自引:0,他引:1
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Nowadays, the importance of identifying the flight mechanisms of the dragonfly, as an inspiration for designing flapping wing vehicles, is well known. An experimental approach to understanding the complexities of insect wings as organs of flight could provide significant outcomes for design purposes. In this paper, a comprehensive investigation is carried out on the morphological and microstructural features of dragonfly wings. Scanning electron microscopy (SEM) and tensile testing are used to experimentally verify the functional roles of different parts of the wings. A number of SEM images of the elements of the wings, such as the nodus, leading edge, trailing edge, and vein sections, which play dominant roles in strengthening the whole structure, are presented. The results from the tensile tests indicate that the nodus might be the critical region of the wing that is subjected to high tensile stresses. Considering the patterns of the longitudinal corrugations of the wings obtained in this paper, it can be supposed that they increase the load-bearing capacity, giving the wings an ability to tolerate dynamic loading conditions. In addition, it is suggested that the longitudinal veins, along with the leading and trailing edges, are structural mechanisms that further improve fatigue resistance by providing higher fracture toughness, preventing crack propagation, and allowing the wings to sustain a significant amount of damage without loss of strength. 相似文献
53.
Yoon Tae Kim 《随机分析与应用》2013,31(5):973-997
Abstract By using the white noise theory for a fractional Brownian sheet, we derive an Itô formula for the generalized functionals for the fractional Brownian sheet with arbitrary Hurst parameters H 1, H 2 ∈ (0,1). As an application, we give the integral representations for two versions of local times of a fractional Brownian sheet, respectively. 相似文献
54.
Alexander Gersten 《Foundations of Physics Letters》1998,11(2):165-178
By applying projection operators to state vectors of coordinates, we obtain subspaces in which these states are no longer normalized according to Dirac's delta function but normalized according to what we call incomplete delta functions. We show that this class of functions satisfy identities similar to those satisfied by the Dirac delta function. The incomplete delta functions may be employed advantageously in projected subspaces and in the link between functions defined on the whole space and the projected subspace. We apply a similar procedure to finite-dimensional vector spaces for which we define incomplete Kronecker deltas. Dispersion relations for the momenta are obtained and sums over poles are defined and obtained with the aid of differences of incomplete delta functions. 相似文献
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Deng Liezheng Shi Wenbo Wang Xiangdan Yang Heping Qu Lishen Sha Guohe 《化学物理学报(中文版)》2004,17(4):378-384
The absolute O2 (1Δ)concentration measurement performed for a singlet oxygen generator(SOG)by using the infrared radiation-calorimetry method is reported with a detailed discussion of its principle and related technique. The influence of O2 (1Δ)gas temperature variation is considered and the corresponding correction has been made,which is neglected by the previous researchers and may cause a significant error in the case of measurement for the large O2 (1Δ)flowrate. Furthermore,an automatically balanced Wheatstone bridge circuit,which is necessary for O2 (1Δ)detection on the SOG of short operation period,is designed and tested by measuring the heat capacity of oxygen. The final error analyses give out a total relative error of ±16% for the O2 (1Δ)concentration,which mainly arises from the measurements of infrared radiation,pressure and temperature at the optical cell. 相似文献
58.
Dan Archdeacon Charles J. Colbourn Isidoro Gitler J. Scott Provan 《Journal of Graph Theory》2000,33(2):83-93
A graph is YΔY‐reducible if it can be reduced to a vertex by a sequence of series‐parallel reductions and YΔY‐transformations. Terminals are distinguished vertices, that cannot be deleted by reductions and transformations. In this article, we show that four‐terminal planar graphs are YΔY‐reducible when at least three of the vertices lie on the same face. Using this result, we characterize YΔY‐reducible projective‐planar graphs. We also consider terminals in projective‐planar graphs, and establish that graphs of crossing‐number one are YΔY‐reducible. © 2000 John Wiley & Sons, Inc. J Graph Theory 33: 83–93, 2000 相似文献
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The contributions of two-photon exchange in the process e~+ + e~-→p +(p) including N and △ intermediate states are estimated in a simple hadronic model. The corrections to the unpolarized cross section as well as to the polarized observables P_x and P_z are evaluated. The results show the corrections to unpolarized cross section are small and the angle dependence becomes weak at small s after considering the N and △(1232) contributions simultaneously, while the correction to P_z is enhanced. 相似文献
60.
用原子荧光光谱法测定了贝壳沙中As元素含量,研究了As在黄河三角洲贝壳堤岛贝壳沙中的空间分布规律,分析了贝壳沙中As与其他营养元素的相关性,并对影响其含量与空间分布的因素进行探讨。结果表明:贝壳沙样品中As的含量范围为0.78~8.76 mg·kg-1,平均值为3.11 mg·kg-1,整体上处于清洁的水平。贝壳沙中As含量有随剖面深度增加而增大的趋势,贝壳沙粒径大小也影响贝壳沙中As的含量,贝壳沙粒径越小,As含量越高,且不同粒径贝壳沙中As含量差异显著(p≤0.05)。贝壳沙中As与全磷(total phosphor,TP)和全钾(total potassium,TK)以及Cu, Zn, Mn均具有极显著的正相关关系,与全氮(total nitrogen,TN)和Fe的相关性不显著。综合分析认为,贝壳沙中As主要来自于风化后的贝壳沙对环境中As元素的吸附与固定而非贝壳形成过程中对该元素的富集作用。 相似文献