Grid method: Application to the characterization of cracks

In this paper we present an application of the grid method to the assessment of crack initiation and growth in brittle materials. It is shown that a grid deposited on the surface of a structure can be utilized to characterize the crack location and opening. Furthermore, one single picture only is required to carry out a control over a predefined area. First, the principle of the method is introduced, showing that a periodical pattern encoding a cracked surface can be analyzed by signal processing. The phase modulation of the grid can be calculated very accurately for any small deformation of the structure. Discontinuities due to cracks are easily detected on the phase field and the crack width is proportional to the amplitude of the discontinuity. Secondly, the performances of the method are presented, mainly depending on the spatial frequency of both the pattern and the sampling. It is shown that good results can generally be obtained with few setting difficulties and equipment investment. Finally, we sum up some basic recommendations for the practical use of the technique.     

铷蒸气密度对光抽运讯号的影响

在铷蒸气密度为1×10~(10)～3.4×10~(11)cm~(-3)的范围内,测量了光抽运讯号。随着密度的增加,讯号先是增大然后减小,并在密度为5.3×10~(10)cm~(-3)时达到最大值。当密度增加到26.7×10~(10)cm~(-3)时,讯号出现负值。     

利用光纤和F-P标准具测量激光的波长和谱线宽度

本文提出了用光纤传输激光进行Ｆ－Ｐ标准具实验的方法，测量了激光的波长和谱线宽度．     

Soft mode dynamics of perovskite type crystals

The soft mode dynamics and related properties of perovskite, ABO₃-type crystals have been studied using the operator form of the model Hamiltonian proposed by Pytte. The correlations have been evaluated using the double time thermal Green’s function technique and Dyson’s equation. Without any decoupling, the higher order correlations, appearing in the dynamical equation, have been evaluated using the renormalized Hamiltonian. The dielectric properties are directly related to the optical soft mode. The phonon width and shift have been calculated for different structural phases. The analysis of the temperature dependence of microwave loss tangent and dielectric constant explains the experimental results.     

Modeling of terrain impact caused by tracked vehicles

Analytical models that can predict the terrain impact caused by tracked vehicles on a horizontal plane were developed and tested. The models included a disturbed width model and an impact severity model. Inputs of the terrain impact models included vehicle static properties, vehicle dynamic properties, and terrain properties. The tested vehicles included an M1A1 tank, an M577 Armored Personal Carrier (APC), and an M548 cargo carrier. The models were verified with field tests conducted in Yakima Training Center in Yakima, WA, Fort Riley, KS, and Camp Atterbury, Indiana. The average percentage errors of the disturbed width model for the M1A1, M577, and the M548 were 10.0%, 27.3%, and 8.5%, respectively. The average percentage errors of the impact severity model of the M1A1 and M577 were 25.0% and 21.4%, respectively.     

Adsorption of the anionic surfactant sodium dodecyl sulfate on a C18 column under micellar and high submicellar conditions in reversed‐phase liquid chromatography

Micellar liquid chromatography makes use of aqueous solutions or aqueous‐organic solutions containing a surfactant, at a concentration above its critical micelle concentration. In the mobile phase, the surfactant monomers aggregate to form micelles, whereas on the surface of the nonpolar alkyl‐bonded stationary phases they are significantly adsorbed. If the mobile phase contains a high concentration of organic solvent, micelles break down, and the amount of surfactant adsorbed on the stationary phase is reduced, giving rise to another chromatographic mode named high submicellar liquid chromatography. The presence of a thinner coating of surfactant enhances the selectivity and peak shape, especially for basic compounds. However, the risk of full desorption of surfactant is the main limitation in the high submicellar mode. This study examines the adsorption of the anionic surfactant sodium dodecyl sulfate under micellar and high submicellar conditions on a C₁₈ column, applying two methods. One of them uses a refractive index detector to obtain direct measurements of the adsorbed amount of sodium dodecyl sulfate, whereas the second method is based on the retention and peak shape for a set of cationic basic compounds that indirectly reveal the presence of adsorbed monomers of surfactant on the stationary phase.     

用指数型整函数的最佳限制逼近

我们研究了由仅有实零点的代数多项式导出的微分算子确定的广义Sobolev类利用指数型整函数作为逼近工具的最佳限制逼近问题.利用Fourier变换和周期化等方法,得到在L_2(R)范数下的广义Sobolev光滑函数类的相对平均宽度和最佳限制逼近的精确常数,以及当0是这个代数多项式的一个至多2重的零点时,得到最佳限制逼近在L_1(R)范数和一致范数下的广义Sobolev类的精确到阶的结果.     

Linear Clique‐Width for Hereditary Classes of Cographs

The class of cographs is known to have unbounded linear clique‐width. We prove that a hereditary class of cographs has bounded linear clique‐width if and only if it does not contain all quasi‐threshold graphs or their complements. The proof borrows ideas from the enumeration of permutation classes.     

Matching Extension Missing Vertices and Edges in Triangulations of Surfaces

Let G be a 5‐connected triangulation of a surface Σ different from the sphere, and let be the Euler characteristic of Σ. Suppose that with even and M and N are two matchings in of sizes m and n respectively such that . It is shown that if the pairwise distance between any two elements of is at least five and the face‐width of the embedding of G in Σ is at least , then there is a perfect matching M₀ in containing M such that .