High-resolution ISAR imaging of fast rotating targets based on pattern-coupled Bayesian strategy for multiple measurement vectors

Very high resolution inverse synthetic aperture radar (ISAR) imaging of fast rotating targets is a complicated task. There may be insufficient pulses or may introduce migration through range cells (MTRC) during the coherent processing interval (CPI) when we use the conventional range Doppler (RD) ISAR technique. With compressed sensing (CS) technique, we can achieve the high-resolution ISAR imaging of a target with limited number of pulses. Sparse representation based method can achieve the super resolution ISAR imaging of a target with a short CPI, during which the target rotates only a small angle and the range migration of the scatterers is small. However, traditional CS-based ISAR imaging method generally faced with the problem of basis mismatch, which may degrade the ISAR image. To achieve the high resolution ISAR imaging of fast rotating targets, this paper proposed a pattern-coupled sparse Bayesian learning method for multiple measurement vectors, i.e. the PC-MSBL algorithm. A multi-channel pattern-coupled hierarchical Gaussian prior is proposed to model the pattern dependencies among neighboring range cells and correct the MTRC problem. The expectation-maximization (EM) algorithm is used to infer the maximum a posterior (MAP) estimate of the hyperparameters. Simulation results validate the effectiveness and superiority of the proposed algorithm.     

Effect of sintering temperature on solidification and migration of non-volatile and volatile heavy metals in glass-ceramic

Using tailings as material to prepare glass-ceramic is an excellent way to achieve the resource utilization of solid waste. However, at present, researches on the solidification and migration of heavy metals are limited. Therefore, in this study, ten groups of samples were prepared by controlling sintering temperatures. The solidification, migration, and leaching behavior of non-volatile and volatile heavy metals were studied. The research showed that, with the increase of temperature, the properties of the samples were improved. Fe participated in the phase transformation and evolved into insoluble iron pyroxenes solid solution, while Pb was homogeneously distributed in the glass matrix of glass-ceramics. The leaching concentrations of Fe and Pb in the glass-ceramics were 0.055 mg/L ～0.087 mg/L and 0.074 mg/L ～0.140 mg/L, which were far below the threshold value. The results showed that heavy metals can be effectively solidified in glass-ceramics and have good environmental benefits.     

Alkylphenol and bisphenol A levels in rubber products

Levels of p-t-butylphenol (PTBP), p-t-octylphenol (PTOP), p-nonylphenol (NP) and bisphenol A (BPA) in rubber products in food-contact use, infant-related use and other uses are reported. Of 60 rubber products tested, PTOP was found in three in a concentration range of 2.2-37 μg g^-1, and NP in 15 in a concentration range of 2.6-513 μg g^-1. PTBP and BPA were not found in any sample. PTOP and NP were not detected in any infant-related sample, regardless of the material type. In contrast, among the samples with food contact and with other uses, the percentages containing PTOP or NP were 33 and 43%, respectively. A migration test was performed on eight samples containing NP and used in food-contact environments. The migration level of NP from spatulas to n-heptane was 0.83-1.52 μg ml^-1. The average migration rates to water, 20% ethanol and n-heptane were 0.03, 0.7 and 6.6%, respectively.     

包气带中不同示踪源层条件下核素迁移对比试验

为研究不同示踪源层材料对水份运移和核素迁移的影响，开展了以石英砂和黄土分别为示踪源层载体时Sr、Nd、Ce在包气带中迁移的对比试验。试验历时470d，在两种源层条件下各取土芯样4次。试验结果表明：在喷淋强度为5mm/h、3h/d条件下，Nd和Ce无论在石英砂示踪源层还是黄土示踪源层中浓度峰位均没有明显向下迁移；对于Sr，在黄土示踪源层中，470d后其峰位向下迁移约15cm(按质心计算为10cm左右)，而从石英砂示踪源层中向下迁移不明显（按质心计算，迁移约2.7cm），只是峰位有些展宽。上述结果表明，极薄（7mm）的细石英砂层也能对非饱和入渗水产生明显屏流作用，使得核素从石英砂示踪源层中向下迁移速度减慢。     

Influence of aggregate content on the migration coefficient of concrete materials using electrochemical method

In order to investigate the effect of coarse aggregate content on the chloride ion migration coefficient of concrete, specimens with different coarse aggregate volume fractions and two water/cement (w/c) ratios of mortar matrix were used. The chloride ion migration coefficient of concrete is obtained using the electrochemical technique to accelerate chloride ion migration in cement-based material and the experimental results were plotted as a function of the fine aggregate volume fraction. The results are analyzed comparing experimental results and theoretical models that represent the concretes as three-phase composite materials. The three phases are the mortar matrix, the coarse aggregate, and the interfacial transition zone between the two. The chloride ion migration coefficient is used to assess the dilution, tortuosity, interfacial transition zone (ITZ) and, percolation effects of coarse aggregate in concrete. It appears that the dilution and tortuosity effects are a dominant factor affecting the chloride ion migration coefficient of concrete in the low volume fraction of coarse aggregate. As the volume fraction of coarse aggregate increases to 40 and 20% in concrete of w/c ratio 0.35 and 0.45, respectively, the ITZ with percolation effects are significantly.     

RS/GIS支持下的柔鱼中心渔场时空动态迁移研究

根据1998-2001年的西北太平洋地区(35°N-45°N,140°E-170°W)巴特柔鱼资源调查与生产的实际情况对柔鱼捕捞作业中心的迁移路线进行研究,并利用同期的SST、SWiFs遥感反演资料,借助GIS的功能,分析了柔鱼中心渔场形成与表层水温、叶绿素a海洋要素场之间的关系,揭示西北太平洋柔鱼中心渔场的环境特征,以期为我国西北太平洋海区的鱿鱼生产服务。     

不同剂量BF^＋2注入多晶硅栅氟迁移特性的二次离子质谱分析

借助ＳＩＭＳ技术，系统地分析了８０ＫｅＶ，２．５×１０１４、５×１０１４、１×１０１５、２×１０１５和３×１０１５ｃｍ－２ＢＦ＋２注入多晶硅栅在９００℃、３０ｍｉｎ热退火条件下，氟在多晶硅栅中的分布剖面，并对氟在多晶硅和二氧化硅中的迁移特性进行了深入讨论。     

放射性核素迁移的实验室研究——Ⅱ.用混合裂变产物溶液研究核素在地质材料上的吸附

应用裂变产物混合物做为示踪剂研究了~(137)Cs,~(141,144)Ce,~(103,106)Ru,~(103,106)Ru,~(95)Zr,~(95)Nb,~(89,90)Sr在花岗岩、凝灰岩、页岩上的吸附行为。应用批式技术测定了吸附比。核素的γ放射性是用连有SCORPIO-3000多道计算机系统的Ce(Li)探测器测量的。β放射性~(89,90)Sr是放化分离后在G-M计数器上测量的。结果表明:凝灰岩、页岩能强烈吸附Ce,Nb,Zr;吸附Cs居中;吸附Sr,Ru较差;花岗岩的吸附性能都差。     

叠前深度偏移中的旅行时并行计算技术

旅行时计算技术是基于波动方程叠前深度偏移方法的核心内容，射线跟踪的数值计算精度和效率直接影响着介质成像质量和实用化。基于三维射线跟踪的微变网络方法和波前重建思路，提出一种适用于三维复杂介质地震波走时的快速算法。但它所需计算量巨大。采用并行计算技术，设计出基于“任务缓冲池”的动态负载平衡策略，在现有的分布式计算机上，实现了三维射线追踪和叠前深度偏移的并行计算。     

环境放射化学研究中几个问题的讨论

本文从辐射环境保护和公众辐射防护的角度，讨论了放射性核素在环境中的迁移行为，放射性核素与环境介质的相互作用和放射性核素在环境中的形态等涉及到环境放射化学研究方向的问题，并讨论了它们之间相互依存的关系。