海面与上方目标复合电磁散射的矩量法研究

采用Monte Carlo方法模拟了一维PM谱海面.运用矩量法研究了一维PM谱海面及其上方二维矩形截面导体柱的复合电磁散射特性,并将计算结果与FDTD结果进行了比对,验证了该算法的正确性。数值计算得到了复合散射系数随散射角的变化曲线,讨论了海面风速、矩形截面柱尺寸和倾角、矩形截面柱中心距离粗糙面的高度对复合散射系数的影响。结果表明,矩形截面柱参数对非镜向复合散射散射系数影响显著,而对镜向散射系数较小。     

广东电网自动发电控制分区控制策略研究

针对传统的自动发电控制(automatic generation control,AGC)策略己不能满足电网运行控制要求的问题,结合广东电网实际运行情况,通过对电网内AGC机组调节特性、负荷变化特性的全面研究,提出了适应节能调度模式的广东电网AGC分区控制策略。该策略在保证电网各个稳定断面不越限的前提下,实现了AGC机组对电网负荷的有效跟踪调整,使高效节能机组尽可能多发电,提高了电网运行的经济性。     

钢芯铝型线绞线与钢芯铝绞线的主要性能对比

提出了导线截面利用率的概念,基于S、Z铝型线导体,给出了几种与常用规格圆线同心绞钢芯铝绞线对应的型线同心绞钢芯铝型绞线,将两者的部分基本参数和特性作了对比。结果表明:型线同心绞的钢芯铝型线绞线比圆线同心绞钢芯铝绞线的导体截面利用率约高15%,若截面积相等,钢芯铝型线绞线的直径约减小9%,其他性能几乎相同;若两者直径相等,则钢芯铝型线绞线的导体截面积、单位质量和抗拉力较大,同时直流电阻减小而载流量增大。钢芯铝型线绞线的安装可采用常规金具,具有一定的缓覆冰性能和较好的弧垂特性,将是输电线路使用中的一种重要线种。     

Radar cross-section measurement method using a spatial filtering within a near zone

A spatial filtering is a useful method for suppressing unwanted reflection from undesired scatters on radar cross-section (RCS) measurements. Highly accurate RCS measurements for stealth-designed targets are generally performed by using full-scale models. However, it is difficult to carry out a measurement of a large full-scale target, because a vast RCS measurement site which satisfies the far-field criterion without undesired scatters is required. In this paper, we have applied the filtering method to RCS measurements in a near field and investigated the validity of that method by varying the scanning angular span. First, a distribution of scattering sources including undesired scatters is predicted from near-field spherical- or cylindrical-scanning data. Next, undesired scatters are suppressed using the spatial filtering. Finally, RCS values of the test target are calculated by taking the Fourier transform of the filtered scattering source distribution. Using electromagnetic simulations, we have validated the RCS measurement method by comparing predicted RCS with reference data as far-field RCS of the test target. As a result, predicted RCS profiles closely matched with reference data. In conclusion, the proposed method is useful for RCS measurements within the unsuitable near zone. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Application of BIB polishing technology in cross-section preparation of porous,layered and powder materials: A review

For the accuracy of experimental results, preparing a high quality polished surface and cross-section of the materials for further analysis using electron backscattered diffraction (EBSD), electron probe microanalysis (EPMA), and scanning probe microscopy (SPM) is extremely important. Broad ion beam (BIB) polishing, a method based on the principle of ion bombardment, has irreplaceable advantages. It makes up for the drawbacks and limitations of traditional polishing methods such as mechanical polishing, electrochemical polishing, and chemical polishing. The ions will not leave the bombardment area during polishing, which makes the BIB method suitable for porous materials. The energy of the ion beam can be adjusted according to the sample to reduce the deformation and strain of the polishing area, especially for fragile, soft, and hard materials. The conditions that need to be controlled during BIB polishing are simple. This paper demonstrated the unique advantages of BIB polishing technology in porous, layered and powder materials characterization through some typical application examples, and guided more researchers to understand and utilize BIB polishing technology in the development of new applications.     

层拉平技术在地震解释中的深化应用

从地震解释角度看,层拉平是一种古地表重建技术。由于技术本身的局限性,地震层拉平无法精确恢复倾斜地层厚度、压实地层厚度和地层水平伸缩量。为此,从地震层拉平的技术原理出发,首先将该技术与其他恢复技术进行对比、分析,然后通过增加地质条件约束或对原有技术方案进行改进,最大限度地降低恢复误差对恢复结果的影响,使地震层拉平技术更好地应用于地震解释的各个环节。并得出如下结论：①在楔状层序顶、底界面夹角小于15°、地层间隔厚度小于1000m的条件下,可利用沿层切片近似代替地层切片预测薄储层; ②当不整合面上、下地层压实作用差异较小时,可先利用地震层拉平技术恢复剥蚀地层厚度,进而利用修正的残余厚度法恢复古地貌;③对于一般地区而言,恢复主成藏期的古构造形态不用再做压实校正,在提高恢复精度的同时,也增强了古构造恢复的油气地质意义;④针对构造变形不甚强烈地区,可利用地震层拉平技术近似代替平衡剖面分析构造演化。这些结论可进一步促进地震层拉平技术在油气勘探领域中的深化应用。     

Ion mobility mass spectrometry in the omics era: Challenges and opportunities for metabolomics and lipidomics

Researchers worldwide are taking advantage of novel, commercially available, technologies, such as ion mobility mass spectrometry (IM-MS), for metabolomics and lipidomics applications in a variety of fields including life, biomedical, and food sciences. IM-MS provides three main technical advantages over traditional LC-MS workflows. Firstly, in addition to mass, IM-MS allows collision cross-section values to be measured for metabolites and lipids, a physicochemical identifier related to the chemical shape of an analyte that increases the confidence of identification. Second, IM-MS increases peak capacity and the signal-to-noise, improving fingerprinting as well as quantification, and better defining the spatial localization of metabolites and lipids in biological and food samples. Third, IM-MS can be coupled with various fragmentation modes, adding new tools to improve structural characterization and molecular annotation. Here, we review the state-of-the-art in IM-MS technologies and approaches utilized to support metabolomics and lipidomics applications and we assess the challenges and opportunities in this growing field.     

Measurements of thermal-neutron capture cross-section of Cesium-135 by applying mass spectrometry

ABSTRACT

The thermal-neutron capture cross-section (σ₀) and resonance integral (I₀) were measured for the ¹³⁵Cs(n,γ)¹³⁶Cs reaction by an activation method and mass spectrometry. Because of difficulty in the preparation of pure ¹³⁵Cs samples, we used ¹³⁵Cs contained as an impurity in a normally available ¹³⁷Cs standard solution. An isotope ratio of ¹³⁵Cs and ¹³⁷Cs in a standard ¹³⁷Cs solution was measured by mass spectrometry to quantify ¹³⁵Cs. Cesium-135 impurity along with the ¹³⁷Cs standard solution was irradiated at the hydraulic conveyer of the research reactor in the Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott’s indices at an irradiation position. A gadolinium filter was used to measure the σ₀, and a value of 0.133 eV was taken as the cut-off energy. Gamma-ray spectroscopy was used to measure induced activities of ¹³⁷Cs, ¹³⁶Cs and monitor wires. On the basis of Westcott’s convention, the σ₀ and I₀ values were derived as 8.57 ± 0.25 barn, and 45.3 ± 3.2 barn, respectively. The value of σ₀ obtained in the present study agreed within the limits of uncertainties with the past-reported value of 8.3 ± 0.3 barn.     

求解复杂轴扭振动力特性的一种近似分析方法

应用模态摄动法求解非均质变截面复杂轴的扭转振动的模态特性。在这一方法中,选择与复杂轴约束条件相同、等截面均匀轴的扭转振动解析模态函数作为近似分析的基函数,采用Ritz展开和摄动分析相结合的方法,把复杂轴扭振的变系数微分方程的求解,转化为一组代数方程组的求解。虽然这一方法应用了结构振动分析中常用的Ritz展开原理,但避免了关于模态广义坐标的特征值问题的求解,通过代数方程组的求解,可逐一求得复杂轴的扭转振动的模态特性,简化了求解的难度。通过2个算例的分析表明,该方法简单实用,且具有较高的精度。     

Deflections of Timoshenko beam with varying cross-section

Closed form solutions are presented for bending beams with linearly and (in the binomial form) parabolically varying depth and for bending beams with linearly varying width along the beam's length. The solutions are developed taking into account the shear deformation of the beam. The solutions are achieved, in an original way, by transforming the fourth-order differential equations with variable coefficients into fourth-order differential equations with constant coefficients. Though the solutions presented refer to three recurrent variations in the beam cross-section shape, the procedure outlined can be applied to beams with binomial variation (with any exponent) in the depth or width of the cross-section. Moreover, the solutions can be achieved for polynomial, exponential and sinusoidal load conditions. The solutions can be utilized to obtain the stiffness factors and the flexibility coefficients of beams in the analysis of frames. Closed form solutions for longitudinal displacements are also presented. The analytical solutions are applied to four recurrent beams commonly used in civil engineering practice and a comparison with a numerical procedure is made.