关于利用散射能谱法测定煤灰份的研究

通过对利用反散射能谱法测定煤灰份的可行性研究，提出了全新的测试方案，研制了先进的 Ｈ Ｃ Ｙ－ １

强脉冲X射线场中散射能谱获取方法

通过对X射线与物质相互作用后产生的散射能谱的分析,可实现物质原子序数的提取,并可用于核材料等违禁品的探测。然而,高能X射线的特性对探测系统的屏蔽和时间响应提出了要求。该文提出了一种能够对脉冲X射线的散射能谱进行采集的实验方案:以LaBr3(Ce)晶体为X射线探测器来实现<100ns的散射光子分辨时间,以减少在5μs脉冲出束时间内的脉冲堆积问题;利用120MHz/14位的高采样率ADC(analog-digital converter)电路来采集前放电路的输出脉冲波形,并设计相应的离线算法将该波形数据重建为散射能谱;设计了合适的屏蔽结构,减少了来自加速器靶点的直接透射X射线和环境散射X射线对探测器的影响。利用该方案对11种具有不同原子序数的物质进行了测量,得到了它们的散射能谱,在511keV峰能量分辨率可达到5%左右。

小口径散射伽玛能谱测井仪

介绍散射伽玛能谱测井仪的组成工作原理、探测系统、探测技术、数据采集、处理及传输技术,能谱探测电路、数据采集电路及编制实时数据采集程序。并针对散射伽玛能谱测井在解决复杂岩性地层地质问题,确定空隙度、解释煤层气、裂隙带等方面的独具特点以及在煤田地质勘探中开展散射伽能谱测井的必要性进行了讨论。

医用电子直线加速器机头散射X射线的分析

本文介绍了一种用于医用电子直线加速器机头的结构部件上产生的散射X射线能量注量分布的解析计算方法。该方法是在蒙特卡罗模拟计算得到的初级X射线能谱的基础上,通过康普顿散射的Klein—Nishina公式计算得到的。考虑的主要散射源为机头内的初级准直器和均整块。我们用这个方法研究了北京医疗器械研究所生产的6MeV BJ-6加速器的机头散射情况并和实验测量结果进行了比较。比较的结果还包括均整块和初级准直器的散射与射野大小及离开X射线源距离之间的关系。比较结果表明:该解析计算方法对计算机头散射问题是可行的。

两维位置灵敏探测器的能量和动量响应函数刻度

用弹性散射对多通道(e,2e)谱仪两维位置灵敏探测器的能量和动量响应函数进行了刻度,从位置灵敏探测器输出的两维位置信息中获得了弹性散射的能谱和角度谱,估计了在当前实验条件下的能量分辨和角度分辨。同时,我们用正交多项式的最小二乘法拟合得到了谱仪单路的能量和动量响应函数。

耐Cd^(2+)假单胞菌富集Cd^(2+)的研究

从安徽某冶炼厂污染土壤中分离出一株能高度耐Cd2+和富集Cd2+的菌株J5。通过光学显微镜、透射电镜、扫描电镜观察到,菌株J5在含2.0mmol/LCd2+的液体培养基和75.0mmol/LCd2+固体培养基上多以聚集成团块形式逐渐富集Cd2+;液体培养基中菌株J5多以四角形的晶体结构存在,而在固体培养基上则以胞外聚集物存在;菌株细胞壁内外密布含Cd2+的颗粒。菌株J5对1.0mmol/LCd2+的积累率为99.1%,菌株内Cd2+质量分数可达32%。

一种新的散射光能谱法测量颗粒粒径的方法

基于光散射原理，提出了一种新的测量颗粒粒径大小及分布的方法。与传统的光散射式激光测粒仪不同，本方法以白色光为光源，仅采集一个空间立体角内的散射光能信号，经反演算后求得被测颗粒的粒径及其分布。给出了这一方法的理论分析、数值模拟以及实验研究。

梯度氮化铁的制备试验

叙述了受梯度功能材料的启发 ,利用对向靶薄膜溅射仪制备梯度氮化铁薄膜的试验 ,对解决钢铁的耐腐蚀问题 。

激光同步辐射源特性分析

激光同步辐射源(Laser Synchrotron Source,简称LSS)是利用强激光与相对论电子束散射,产生准单色、能量可调的高质量X射线的新型X射线源,具有一些现有X射线源所不具备的优点,因而具有广泛的应用前景,用康普顿散射原理分析了激光同步辐射源的原理特性,推导了出射X射线的粒子通量,分析了电子束和激光束的横向分布对粒子通量的影响。

The effect of the support on the surface composition of PtCu alloy nanocatalysts: In situ XPS and HS-LEIS studies

Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area Ti〇2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribu-tion, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 sur-face and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk com-position were plotted and compared for the supported and unsupported materials.

基于蒙特卡洛模拟的肺癌患者体内光子能谱和散射次级电子能谱研究

目的放射治疗是恶性肿瘤的重要治疗手段,且治疗的精准度越来越高。针对患者的个体化生物特征,设计更精准的个体化放疗方案已引起研究人员的重视。该文研究放疗中高能光子束进入患者肿瘤及正常组织后光子能谱和散射次级电子能谱规律,为放射生物剂量个体化计算奠定理论基础。方法将患者的CT图像序列经重采样,体元尺寸为2. 54 mm×2. 54 mm×2. 5 mm,并将体元的CT值转换成材料的元素组成密度。利用蒙特卡洛模拟方法计算各受照射体元的光子能谱和散射次级电子能谱,并分析能谱规律。结果能谱在250～300 ke V达到峰值,平均能量范围为900～1150 ke V,不同入射深度处的光子能谱具有较好的一致性。散射次级电子能谱可分为两种类型:①高密度区域(肿瘤组织),散射次级电子平均能量较高(平均能量约为909. 58 ke V)且能谱存在展宽;②低密度区域,散射次级电子平均能量较低(平均能量为536 ke V)且能谱无展宽。结论该研究给出了肺癌患者体内光子能谱和散射次级电子能谱的具体分布规律和表达,为在细胞及DNA层面研究放射生物剂量计算模型奠定了基础。

Shot Noise in Ferromagnetic Superconductor Tunnel Junctions

In this paper, the superconducting order parameter and the energy spectrum of the Bogoliubov excitations are obtained from the Bogoliubov-de Gennes （BdG） equation for a ferromagnetic superconductor （FS）. Taking into account the rough interface scattering effect, we calculate the shot noise and the differential conductance of the normalmetal insulator ferromagnetic superconductor junction. It is shown that the exchange energy Eh in FS can lead to splitting of the differential shot noise peaks and the conductance peaks. The energy difference between the two splitting peaks is equal to 2Eh. The rough interface scattering strength results in descent of conductance peaks and the shot noise-to-current ratio but increases the shot noise.

Ignition-proof mechanism of ZM5 magnesium alloy added with rare earth

The ignition-proof mechanism of ZM5 magnesium alloy added with 0.1% （mass fraction） rare earth （RE） was investigated. The oxide scales and substrates were characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, energy dispersive spectrometer （EDS） and tensile test. And an oxidation model of ZM5 alloy with RE was established. The results show that the ignition temperature of ZM5 alloy is particularly elevated from 654 to 823 ℃, the microstructure is refined, and the tensile strength is slightly improved from 168.2 to 174.6 MPa by adding 0.1% RE. A double-layer oxidation film formed on the alloy surface under high temperature mainly consists of MgO, RE203 and A1203, which is 2.5-3.5 μm in thickness. It is found that the forming of protective oxidation film on the thermodynamics is attributed to RE elements congregating on the surface of molten Mg alloy.

Performance of engineered cementitious composite containing stone slurry powder waste

Most of the materials used in engineered cementitious composite are fine in size to achieve ductile nature.Stone slurry powder(SSP)is an inert material obtained from stone industries as by-product which may cause hazardous impact on environment.In this research work,partial replacement of silica sand(SS)and fine sand(FS)by SSP with different contents(25%and 50%each)for making engineered cementitious composite has been explored.The performance was evaluated on the basis of strength,tensile strain,mid span deflection capacity,ultra-sonic pulse velocity and microstructure.Mechanical strength was found to be increased at 25%SSP in both replacements;whereas,strength decreased slightly at 50%replacement.Tensile strain,mid span deflection and quality of concrete were enhanced with increase in SSP content.Using SSP formed denser cementitious composite can help to save the natural resources and contribute in making green cementitious composite.

Absorption and Recurrence Spectra of Li Rydberg Atom in Perpendicular Electric and Magnetic Fields

We develop the semi-closed orbit theory from two degrees of freedom to three non-separable degrees of freedom and put forward a new model potential for the Li Rydberg atom, which reduces the study of the system to an effective one-particle problem. Using this model potential and the closed orbit theory for three degrees of freedom, we caiculate the recurrence spectra of Li Rydberg atom in perpendicular electric and magnetic fields. The closed orbits in the corresponding classicai system have also been obtained. The Fourier transformed spectra of Li atom have ailowed direct comparison between the resonance peaks and the scaied action values of closed orbits, whereas the nonhydrogenic resonance can be explained in terms of the new orbits created by the core scattering. Our result is in good agreement with the quantum spectra, which suggests that our calculation is correct.

Preparation of calcium phosphate coatings on Mg-1.0Ca alloy

The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.

Detecting Magma Mixing Processes Using Scanning Electron Microscopy Method

This review work explains some of the most important techniques to detect the occurrence of magma mixing phenomena in the volcanic rocks by using SEM （scanning electron microscope）. In particular, the most useful methods related to the different types of mixing are reviewed： complete mixing （blending） or incomplete mixing （mingling）. For blending, backscattered electron images and EDS （energy dispersive spectroscopy） are the most accurate methods： an example taken from a sample of ash of the 2007 Stromboli volcano eruption was used. For mingling, the best method is given by X-ray elemental mapping （in particular of Ca and Si）, as explained through the example taken from a sample of the 2003 explosive eruption of Soufriere Hills volcano. The aim of this work was to establish whereas would be useful to use backscattered eletron images, EDS, or X-ray elemental mapping techniques, according to the different types of mixing that occur very often in magmatic systems.

同步辐射核共振振动能谱学(上)：原理篇

核共振振动能谱学(简称核振能谱)是一种以同步辐射为实验基础的新型的振动能谱学方法。与红外、拉曼等传统的振动光谱学方法相比,核振能谱在理论上和实验上具有一系列突出的特点和优越性,从而在各学科,特别是在铁基化学和铁基生物化学的研究中有着广泛的应用。文章分为上下两篇,上篇介绍核振能谱的基本概念、基本理论、实验方法和实验条件等基础内容,并以简单的四氯化铁离子([FeCl4]-)为例,演示由原始核振能谱到振动态密度函数(PVDOS)的分析流程。在选材上,文章侧重先进性、代表性和实用性;在叙述上,考虑到非同步辐射专业研究者的阅读需要,文章突出实验科学和应用科学的内容,力求简单明了、通俗易懂。下篇将系统介绍该能谱学方法在化学与生物化学中的应用实例。

The critical role of electrochemically activated adsorbates in neutral OER

Developing efficient electrocatalysts for the oxygen evolution reaction(OER)under neutral conditions is important for microbial electrolysis cells(MECs).However,the OER kinetics in neutral electrolytes at present are extremely sluggish,resulting in high overpotentials that greatly limit the energy conversion efficiencies of MECs.Previous studies failed to probe the adsorbates on surface metal sites of catalysts at the atomic scale and elucidate their influence on the catalytic activities,which has impeded the rational design of efficient neutral OER catalysts with optimal surface structures.Here,using in situ transmission electron microscopy(TEM),in situ X-ray photoelectron spectroscopy(XPS)and in situ low-energy ion scattering studies,we have identified,for the first time,that the electrochemically activated adsorbates on surface metal sites play a critical role in boosting the neutral OER activities of Ru-Ir binary oxide(RuxIryO2)catalysts.The adsorbate-activated RuxIryO2on a glassy carbon electrode achieved a low overpotential of 324 m V at10 m A cm-2in neutral electrolyte,with a 36-fold improvement in turnover frequency compared with that of Ir O2benchmark.Upon application in an MEC system,the resulting full cell showed a decreased voltage of 1.8 V,200 m V lower than the best value reported to date,facilitating efficient synthesis of poly(3-hydroxybutyrate)from bioelectrochemical CO2reduction.Density functional theory(DFT)studies revealed that the enhanced OER activity of RuxIryO2catalyst arose from local structural distortion of adjacent adsorbate-covered Ru octahedra at the catalyst surface and the consequently decreased adsorption energies of OER intermediates on Ir active center.

A Study on the Interaction Mechanism between Thermal Radiation and Materials

From the viewpoint of field synergy principle and dipole radiation theory, the interaction between the incident thermal radiation wave and materials is analyzed to reveal the mechanism of selective absorption of incident thermal radiation. It is shown that the frequency of the incident thermal radiation and the damping constant of damping oscillators in materials are of vital importance for the thermal radiation properties (reflectivity, absorptivity, transmissivity, etc.) of materials.