Pattern search algorithms for nonlinear inversion of high-frequency Rayleigh-wave dispersion curves

Inversion of Rayleigh wave dispersion curves is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this paper, we implemented and tested a Rayleigh wave dispersion curve inversion scheme based on GPS Positive Basis 2N, a commonly used pattern search algorithm. Incorporating complete poll and complete search strategies based on GPS Positive Basis 2N into the inverse procedure greatly enhances the performance of pattern search algorithms because the two steps can effectively locate the promising areas in the solution space containing the global minima and significantly reduce the computation cost, respectively.The proposed inverse procedure was applied to nonlinear inversion of fundamental-mode Rayleigh wave dispersion curves for a near-surface shear (S)-wave velocity profile. The calculation efficiency and stability of the inversion scheme are tested on three synthetic models and a real example from a roadbed survey in Henan, China. Effects of the number of data points, the reduction of the frequency range of the considered dispersion curve, errors in P-wave velocities and density, the initial S-wave velocity profile as well as the number of layers and their thicknesses on inversion results are also investigated in the present study to further evaluate the performance of the proposed approach.Results demonstrate that pattern search algorithms applied to nonlinear inversion of high-frequency surface wave data should be considered good not only in terms of accuracy but also in terms of the computation effort due to their global and deterministic search process.     

Exact integration in the boundary element method for two-dimensional elastostatic problems

This paper derives the exact integrations for the integrals in the boundary element analysis of two-dimensional elastostatics. For facilitation, the derivation is based on the simple forms of the fundamental functions by taking constant, discontinuous linear and discontinuous quadratic elements as examples. The efficiency and accuracy of the derived exact integrations are verified against five benchmark problems; the results indicate that the derived exact integrations significantly reduces the CPU time for forming the matrices of the boundary element analysis and solving the internal displacements.     

在65t/h锅炉上应用小型集散控制系统

针对湘钢６５ｔ／ｈ链条钢炉气煤混烧特点，设计了给水、燃烧、汽温调节，应用美国Ｈｏｎеｙｗеｌｌ９０００系列小型集散控制系统，保证了锅炉安全、经济运行，达到了节能目的。     

分割电极片状压电致动器——(二)位移特性及狭缝宽度对其影响的实验研究

研究了悬臂梁式分割电极片状压电致动器的位移特性。理论分析表明，分割电极狭缝宽度会减小致动器自由端的位移输出，但当狭缝宽度小于致动器电极宽度的１０％时，可忽略狭缝宽度的影响。致动器端部位移的测试结果大于理论计算值。与现有磁头悬浮臂尺寸相近的致动器，在２０Ｖ～５０Ｖ的电压驱动下均可获得１μｍ～２μｍ的致动位移。对９８５０道／厘米的密度磁盘，该位移能覆盖至少一个磁道宽度，满足磁头定位两级伺服系统对第二级致动器位移的基本要求。     

Acoustical tomography based on the second-order Born transformperturbation approximation

Reconstruction algorithms and their numerical examples of acoustical tomography based on the second-order Born transform perturbation approximation are presented. The reconstruction algorithms in the second-order Born approximation are similar in form to those in the first-order Born approximation. Replacing the angular spectrum of the scattered wave in the first-order case by the result of applying a first-order operator to the angular spectrum of the scattered wave or applying a second-order operator to the angular spectrum of the incident wave leads to the second-order reconstruction algorithms. Also, comparisons of reconstruction algorithms of the first- and second-order Born approximations are given, and they show that the second-order Born approximation algorithms have a distinct advantage over the first-order approximations in many cases     

SIMILARITY LAW OF FLUCTUATING PRESSURE WITHIN HYDRAULIC JUMP AREA

Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law.     

^60Coγ射线对刚地弓形虫缓殖子感染性的影响

应用不同剂量的~(60)Coγ射线照射含NT株弓形虫包囊的鼠脑匀浆后,以0.4％胰蛋白酶液消化,使弓形虫缓殖子从包囊中释放出来,并用生理盐水作连续10倍稀释,使成为含不同数量缓殖子的悬液,将此悬液接种小鼠,用生物检测方法确定其感染性。另设未经照射处理的缓殖子悬液感染小鼠的对照组。结果表明,γ射线0.55kGy剂量为控制鼠脑中NT株弓形虫感染性的最小有效剂量。γ射线0.1kGy剂量对弓形虫缓殖子感染性无明显影响,而0.45kGy照射后,其感染性较前者下降了10~4倍。     

Observation of atomic steps on CaCO3 crystal surface

By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed.