夹套容器焊缝射线照相管电压的选择

射线检测夹套容器焊缝时,由于工件表面至胶片的距离比相同情况下单壁透照大的多,为提高底片的清晰度和对比度,必须合理选择透照参数。文章通过理论分析和实验分析,阐述了夹套容器焊缝射线检测时,选择管电压,增大其射线照相对比度,提高了小缺陷检出率。     

A novel semi-analytic method for the analysis of scattering by dielectric objects immersed in uniform media

The method for the solution of scattering problems with homogeneous dielectric scatterers based on a single coordinate multipole expansion, the Stratton-Chu integral and Maxwell's equations in the integral form is proposed in this paper. Its convergence is proved. The sources of ill-conditionality of constitutive algebraic systems are established. The method of their regularization based on the use of a scalar control parameter is suggested. For the sake of validation, the numerical analysis is performed for different testing objects.     

A New Method of Simulating Bright Temperature of Snow Cover based on Snow Grain Size Evolution Process

This research used HUT model, DMRT model and MEMLS model to simulate interactions(absorption and extinction) between snow grainsfor different wave bands (18.7 GHz and 36.5 GHz) of microwave which were used for radiative transfer model. Obtaining the snow grain size is always a difficulty. So this research used Jordan91 snow grain size evolution model to evolve snow grain size which was regarded as input parameter of radiative transfer model, and used measured data to simulate spaceborne brightness temperature for 18.7 GHz horizontal polarization and 36.5 GHz horizontal polarization in a mixed pixel. The results showed that the bias of simulation brightness temperature using extinction coefficient of HUT model, DMRT model and MEMLS model for 18.7 GHz horizontal polarization were -3.6 K、-1.8 K and -0.7 K respectively, and for 36.5 GHz horizontal polarization were 4.0 K、10.4 K and 14.4 K respectively. For 18.7 GHz horizontal polarization and 36.5 GHz horizontal polarization, the bright temperature simulation based on effective snow grain size shows a good linear relationship with the brightness temperature simulation basedon snow grain size evolution process. Therefore, the method based on the snow grain size evolution process is a suitable method for obtaining the snow grain size parameter in the radiative transfer model.     

Internal Defect Measurement of Scattering Media by Optical Coherence Microscopy

Optical coherence microscopy is applied to measure scattering media‘s internal defect, which based on low coherence interferometry and confocal microscopy. Optical coherence microscopy is more effective in the rejection of out of focus and multiple scattered photons originating further away of the focal plane. With the three-dimension scanning, the internal defect is detected by measuring the thickness of different points on the sample. The axial resolution is 6μm and lateral resolution is 1.2μm. This method is possessed of the advantages over the other measurement method of scattering media, such as non-destruction and high-resolution.     

Mental health services in Louisiana school-based health centers post-Hurricanes Katrina and Rita.

Following Hurricanes Katrina and Rita, Louisiana school-based health centers (SBHCs) were called on to respond to a sharp increase in mental health needs, especially for displaced students coping with grief, loss, trauma, and uncertainty. To assess the impact of the hurricanes on the students and the needs of SBHC mental health providers (MHPs), we surveyed MHPs in each of the SBHCs under the auspices of the Louisiana Department of Health and Hospitals, Office of Public Health. SBHC practitioners from around the state reported that mental health service utilization rose during the 2005-2006 school year, but utilization of services increased most significantly in schools receiving the majority of displaced students. Anxiety and adjustment problems were noted as increasing the most following the hurricanes. A multitude of other conditions was also reported. By the time of this survey in April 2006, the reported prevalence of most symptoms had declined, but all remained above their pre-hurricane levels. Self-reported needs of SBHC MHPs are also discussed in light of the major natural disasters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modelling of light extinction by soot particles

A simplified model for the prediction of light extinction through combustion generated smoke is presented. The model builds upon existing theory and available experimental data to account for the principal factors that influence light extinction in participating media, including wavelength, primary particle size distribution and morphological structure of particle aggregation as well as multiple scattering among particles within a particle aggregation. Good agreement is demonstrated between the model predictions and experimental data in the visible and IR ranges. The model illustrates that as the mean particle size increases, the integral optical property of a soot cloud approaches that of monodisperse particles. It is postulated in the current study that the number of particles participating in multiple scattering is around 20 regardless of the real size of particle aggregation.     

Simulation of quantum-ballistic nanoswitches

A two-dimensional model based on the solution of the Schrödinger-Poisson system in effective-mass formulation is proposed for the calculation of quantum-ballistic transport processes in nanoswitch structures. The method is appropriate to properly describe the strong confinement of the electrons in the heterostructure. Using scattering boundary conditions an energy-dependent transmission matrix is calculated that allows us to determine the total charge density of all electrons injected into the device by integration over energy. In this approach space charge effects are self-consistently taken into account. The practicality of the model for numerical simulation is demonstrated with reference to measured data for various device geometries. We find that for device structures such as the Y-branch switch non-linear effects are of crucial importance.     

用碳氧比测井确定喇嘛甸油田的气液界面

碳氧比（Ｃ／Ｏ）测井主要用于计算储集层中的含油饱和度，进而判断油水层，用Ｃ／Ｏ测井确定气液界面是Ｃ／Ｏ测井应用的一个新的尝试，本介绍了用Ｃ／Ｏ测井确定气液界面的原理和在喇嘛甸油田的实际应用，说明用Ｃ／Ｏ测井确定气液界面无论在原理上还是在实际应用上都是切实可行的。     

有限频率选择表面电磁散射特性的分析方法

针对有限频率选择表面的电磁散射特性难以用一般方法进行分析的难题 ,提出了两种行之有效的适合不同情况的高效处理方法 :谱域伽略金法和基于平面波谱 (PWS)分解逼近的方法 ,大大节约了CPU的计算时间和内存空间。     

Analysis of setting errors in precision ballscrew machining and the automatic adjustable center

Generally, in machining precision machine elements such as ballscrews, machining errors could occur for various reasons. In this research, the influence of improper setting errors in ballscrew machining, such as misalignment between centers, runout of spindle, and unsuitable contact conditions between the center and the center hole, was analyzed. From the analysis, among the setting errors, the misalignment between centers was found to be an important one. An automatic adjustable center for 2D arbitrary positioning was designed and manufactured to eliminate the alignment error in machining workpieces supported by two centers. This adjustment system could be practically applied to reduce machining errors.