Measurements of Photon Mass Attenuation Coefficients for Ge and BGO Crystals at 10 Me V

The photon mass attenuation coefficients of the important materials for γ-ray detection, Ge and BGO (Bi₄Ge₃O₁₂) crystals, have been measured for 10.0 MeV γ-rays. The measurement system using the laser-Compton backscattering γ-rays and the high-resolution high-energy photon spectrometer has been developed and utilized. The effectiveness of the system achieving the total systematic uncertainties of 0.5% for the measurements of the photon mass attenuation coefficients was demonstrated. It was shown that the measured photon mass attenuation coefficients, 318.1 ± 1.7 [cm²/g] for the Ge crystal and 425.2 ± 2.4 [cm²/g] for the BGO crystal, agree within the achieved experimental uncertainties with the evaluated values including atomic and nuclear processes at 10.0 MeV.     

Effective Characterization of DNA Ligation Kinetics by High-Resolution Melting Analysis

High-resolution melting (HRM) analysis has been improved and applied for the first time to quantitative analysis of enzymatic reactions. By using the relative ratios of peak intensities of substrates and products, the quantitativity of conventional HRM analysis has been improved to allow detailed kinetic analysis. As an example, the ligation of sticky ends through the action of T4 DNA ligase has been kinetically analyzed, with comprehensive data on substrate specificity and other properties having been obtained. For the first time, the kinetic parameters (k_obs and apparent K_m) of sticky-end ligation were obtained for both fully matched and mismatched sticky ends. The effect of ATP concentration on sticky-end ligation was also investigated. The improved HRM method should also be applicable to versatile DNA-transforming enzymes, because the only requirement is that the products have T_m values different enough from the substrates.     

Growth mechanism and gas-sensing characteristics of organic-additive-free zinc oxide of various shapes

Zinc oxide is widely used in gas sensors, solar cells, and photocatalysts because of its wide bandgap and exciton binding energy of 60 meV in various metal oxides. To use ZnO as a gas sensor, it is necessary to synthesize it with surface defects and a large specific surface area. In this study, hydrothermal synthesis without surfactants was employed to obtain organic-additive-free ZnO. For morphology control, we varied the ratio of the hydroxide ion concentration to the zinc ion concentration. To confirm the growth mechanism of ZnO, we performed X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses. Raman spectroscopy and photoluminescence measurements were performed to analyze the surface properties. The Brunauer–Emmett–Teller method and probe stations were used to measure the specific surface area and sensitivity of the gas sensor, respectively. The results confirmed that flower-shaped ZnO is the most suitable gas-sensing material.     

印刷电子领域的高分辨导电布线技术

综述了印刷电子领域的高分辨导电布线的研究现状,具体分析了目前印刷电子领域中实现高分辨导电布线的有效途径以及影响印刷分辨率的重要因素。     

Development of an HRTEM image analysis method to quantify carbon nanostructure

An analytical method for analyzing high-resolution transmission electron microscopy (HRTEM) images is presented. The method is composed of two major parts: digital image processing and lattice fringe characterization. The digital image processing is composed of the following operations: negative transformation, region of interest (ROI) selection, contrast enhancement, Gaussian lowpass filter, top-hat transformation (used to correct uneven illumination across an image), thresholding to obtain a binary image, morphological modification, clearing fringes on the ROI border, skeletonization, and removing short fringes that lack physical meaning. These operations are defined by equations with effects illustrated by images. The lattice fringe characterization generates statistics on fringe length, tortuosity, and separation based on the skeletons of the graphene layers. Fringe length and tortuosity are obtained automatically from the features of the skeletons, while fringe separation is obtained by analyzing manually selected fringe pairs. The algorithms are implemented within MATLAB, and demonstrated upon an exemplary HRTEM image of carbonaceous material. The image analysis algorithm permits quantitative HRTEM, here specifically addressing nanostructure of carbonaceous materials.     

In vivo lipolysis induced by heparin injection or fasting: a proton MR spectroscopy analysis of human plasma

The impact of induced lipolysis on the composition of plasma lipids is analyzed by proton magnetic resonance spectroscopy (MRS) in humans. The variations of the methylene and methyl resonances from lipids in lipoproteins are studied under two sets of lipolytic conditions: acute endovascular lipolysis induced by an intravenous injection of heparin and subacute lipolysis induced by short fasting. During acute lipolysis, the degradation of the very low density lipoproteins structures is well correlated to the modifications observed in the areas of CH₂ and CH₃ MRS signals. The comparison of regular spectra, spectra with water signal suppression, and spectra recorded with a spin-echo sequence provides information on the behavior of the different parts of the lipoproteins, that is, the neutral core, little affected by heparine-induced lipoprotein lipase (LPL) activation, and the surface layer supplying substrates to LPL. During 48 h of fasting, only limited modifications occur on the MR spectra, and lipolysis cannot be documented in details.Address for correspondence: CRMBM-CNRS, Faculté de Médecine, 27, bd Jean Moulin, 13005 Marseille, France.     

MR high-resolution imaging of arterial intimal hyperplasia at 1.5 T

Intimal hyperplasia is the earliest microscopic change detectable in the arterial wall in the development of arteriosclerosis and atherosclerosis. To enable high-resolution imaging of this, a standard 1.5-T machine was modified using inserted gradient coils of 30 cm internal diameter and surface radio-frequency coils. Six rabbit aorta specimens with injury-induced intimal hyperplasia and two normal rabbit aorta specimens were imaged using a spin-echo sequence of TE 40. Pixel sizes as small as 20 µ×20 µ could be obtained and the area of intimal hyperplasia could be measured at 80 µ×40 µ. The results were compared with those made by a computer-linked microscope. In the injured aortas, there was a low-signal region on magnetic resonance imaging which corresponded to the media of the vessel wall when compared with the histology.T ₁ andT ₂ constants for the media were determined and compared with those of a normal specimen. TheT ₁ constant was shorter for the media of the injured aorta than in the normal. This could be related to the disruption of the internal elastic lamina and migration of muscle cells to the intima which occurs following injury. The popliteal artery of four normal volunteers was imaged and the area of the wall could be measured at a pixel size of 312 µ×160 µ. This suggests thatin vivo studies of intimal hyperplasia arteriosclerosis and atherosclerosis could be made.     

一种低功耗高精度Sigma-Delta调制器

提出了一种改进的三阶单环Sigma-Delta调制器,噪声传递函数采用前馈方式实现极点,降低了积分器输出信号的幅度,从而降低功耗;采用局部反馈实现零点,从而优化了输出信噪比。采用0.35μm CMOS工艺设计了该调制器,过采样率128,信号带宽24kHz,分辨率16bit,在3.3V工作电压下,模拟电路部分功耗2.7mW,数字部分功耗0.5mW。电路用开关电容技术实现,在HSPICE中通过多工艺角验证。     

MSB-CAATI算法在多波束测深系统中的应用

计算到达角瞬态成像技术(CAATI)是多角测深侧扫声纳(MSBSS)采用的高分辨方位、幅度联合估计技术。本文将CAATI技术扩展到多波束测深声纳(MBBS),提出了一种新的多子阵波束域CAATI(MSB-CAATI)算法。仿真实验证明了该算法与CAATI技术相比具有更高的估计精度和更低的分辨力门限。海试数据的处理验证了MSB-CAATI能很好地应用到多波束测深系统中,使其兼备了FT(傅氏变换)和CAATI各自的优点,能在整个条带宽度内同时获得高分辨力的海底地形和地貌信息,且不易受到低信噪比和复杂地形环境的影响。     

High-Resolution ISAR Imaging Based on Sparse Iterative Covariance-Based Estimation

基于协方差稀疏迭代谱估计的ISAR高分辨成像

王勇^1，2，张荣政^1，2

(1.哈尔滨工业大学 电子工程技术研究所，哈尔滨 150001;

2. 对海监测与信息处理工业和信息化部重点实验室 哈尔滨 150001)

创新点说明：

提出一种基于协方差稀疏迭代谱估计（SPICE）的ISAR高分辨成像算法，具体创新性可说明如下：

1）首先在回波数量有限的情况下使用SPICE算法估计ISAR方位像上的多普勒谱，进而得到高分辨率的成像结果。

2）本文所用方法解决了传统方法处理回波数量有限或者转角很小的ISAR数据分辨率不够的问题，相比于主流的压缩感知方法，该方法不需要预先设置任何参数。对比同类的谱估计方法，该方法的分辨率更高。

3）为解决SPICE方法计算量大的问题，给出一种基于G-S分解的快速实现方法，降低了运算复杂度。

研究目的：

由于实际系统可能具有有限数量的回波或者一些回波受到强干扰，因此传统的基于FFT的距离多普勒算法的分辨率可能无法满足要求。当相干累积角度受到限制时，有必要使用高分辨率方法进行ISAR成像。本文提出一种基于协方差稀疏迭代谱估计（SPICE）的ISAR高分辨成像算法。该算法具有全局收敛性，不需要预先设置参数，能有效提高成像分辨率。针对SPICE方法计算量大的问题，本文提出了一种改进方法。

研究方法：

1）对回波数据进行解线性调频处理，对其得到的每一个一维距离像进行运动补偿消除平等分量。

2）将有效数据中每一个距离单元内的方位向数据视为一个稀疏的复合频率信号，使用改进的SPICE算法估计信号的频谱，将其作为方位向压缩的结果，从而得到清晰的成像结果。

研究结果：

1）文中进行了针对一维线谱数据的频谱仿真实验，说明了SPICE算法对于数据量很小的信号频谱估计的精确性。

2）文中使用IAA算法及SPICE算法进行了仿真MIG-25和Yak-42数据的小转角成像实验，实验结果说明，SPICE算法能够在获得回波很少的情况下获得清晰的目标图像，有效提高了成像的分辨率。

3）文中将使用SPICE算法的成像结果与IAA算法成像结果进行了定量对比，说明了SPICE算法的优越性。

结论：

1）本文提出的基于协方差稀疏迭代的ISAR高分辨成像算法在不需要设置任何参数的同时利用信号的稀疏性，有效地提高ISAR成像的分辨率。

2）为减少计算量，本文还介绍了基于G-S分解的SPICE算法的快速实现。仿真MIG-25和Yak-42实测数据的实验结果说明了SPICE算法的有效性。

关键词：ISAR，高分辨，SPICE，快速实现