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     

SiH4激光等离子体内H谱线的线型研究

本文利用OMA-Ⅲ系统测量了脉冲TEA CO_2激光诱发的SiH_4等离子体发光谱内H巴耳末系的H_α、H_β和H_γ线的线型及线宽。通过理论及实验分析,认为这些谱线的主要加宽机制为Stark加宽。由实验线型和理论线型的拟合得到等离子体的电子温度T≈40000K和电子密度N≈10~(17)cm~(-3)。     

化工矿山预可行性研究计算机辅助设计系统

概略介绍了该系统的功能、结构、运行方式及控制逻辑结构,以及测试结果。     

川东地区长兴组缝洞型储层的识别

本文针对四川东部地区上二叠统长兴组(P_2~2)缝洞型储层的低孔、低渗及非均质性等特点,分析了影响这类储层识别的主要因素,提出了利用现有的地球物理测井手段定性识别储层的指标和定量综合识别储层的方法,这可望提高测试成功率。     

含H2S井完井液用除硫剂和缓蚀剂

含H_2S井完井液对井下金属管串具有腐蚀性。采用锌基或铁基螯合物除硫剂及咪唑啉缓蚀剂可有效地防止这种腐蚀的发生。本文对H_2S的腐蚀、除硫剂和缓蚀剂产品及其对产层的损害作了介绍与探讨。     

Tandem repeating of the expression cartridge--a novel strategy to enhance the expression efficiency of cloned gene in Escherichia coli

The aim of this study was to determine the actual prevalence of diabetes mellitus and to investigate the contribution of various risk factors to the diabetes mellitus among the population in a methyl mercury polluted area. The study was a population based cross sectional mass screening survey. A case-control study was designed to estimate the role of various risk factors including methyl mercury exposure for diabetes mellitus. The study was confined to a small rural town 10 km north of Minamata City; 1,087 persons older than 40 years were examined. Measurement of glucose metabolism was made on the basis of urine and haematological examinations. Data on risk factors were collected by questionnaire, and by measurement of body height and weight (obesity). The prevalence rate of the diabetes mellitus was 8.4% in males and 5.3% in females. The odds ratio of family history was significantly higher, 4.63. The odds ratio of residential history in a methyl mercury high polluted area was 0.58. The prevalence of the diabetes mellitus in this methyl mercury polluted area was not increased, contrary to what was expected based on the pathological findings.     

Robot Pose Estimation in Unknown Environments by Matching 2D Range Scans

A mobile robot exploring an unknown environment has no absolute frame of reference for its position, other than features it detects through its sensors. Using distinguishable landmarks is one possible approach, but it requires solving the object recognition problem. In particular, when the robot uses two-dimensional laser range scans for localization, it is difficult to accurately detect and localize landmarks in the environment (such as corners and occlusions) from the range scans.In this paper, we develop two new iterative algorithms to register a range scan to a previous scan so as to compute relative robot positions in an unknown environment, that avoid the above problems. The first algorithm is based on matching data points with tangent directions in two scans and minimizing a distance function in order to solve the displacement between the scans. The second algorithm establishes correspondences between points in the two scans and then solves the point-to-point least-squares problem to compute the relative pose of the two scans. Our methods work in curved environments and can handle partial occlusions by rejecting outliers.