高能原电子对铝和金射程的表达式

根据原电子的射程与入射能量和能量幂次的关系,用ESTAR程序分别计算出高能原电子对铝射程的能量幂次约为1.72,对金射程的能量幂次约为1.62。分别根据高能原电子对铝和金的射程与入射能量的关系,用实验数据计算出常数其能量幂次,然后分别推导了高能原电子对铝的射程的表达式和对金的射程的表达式。用推导出的表达式分别计算出一些高能原电子对铝和金的射程计算值,与现有实验值相符较好。

射程法测量低能电子加速器能量方法比较研究

为了准确、方便地测量辐射加工用低能电子加速器能量,采用射程法测量电子束能量,设计加工了两种不同类型的聚苯乙烯材料的楔形模体和叠层模体,结合辐射变色薄膜剂量计测量装置,利用两种能量测量模体同时测量标称能量为0.65MeV的加速器电子束能量,结果表明,设计的楔形模体可以测量能量低至0.65MeV的电子束能量。相比于叠层能量测量方法,楔形模体测量方法更为方便,效率更高,引入的不确定度更小。实践中射程法测量0.65MeV以上低能电子束能量时,推荐楔形能量测量模体测量电子束能量。

DZ-12/4多能量档电子直线加速器辐照关键参数测试

中国原子能科学研究院建立了一台DZ-12/4多能量档电子直线加速器,该装置主要用作辐射加工级电子束辐照实验平台。为了检测该电子束辐照实验平台辐照工艺控制参数,本文利用中国原子能科学研究院FJL-02型辐射变色薄膜剂量计对DZ-12/4多能量档电子直线加速器关键参数能量进行了测量,并对研制的束流监测系统法拉第筒的可靠性进行了验证。结果表明,DZ-12/4多能量档电子直线加速器能量在4~12 MeV范围可调,运行参数准确可靠;日常运行中,加速器运行人员通过监测设备和调节加速器参数可有效控制并估计辐照剂量,具有非常好的实用性和简便性。

皮尔斯电子枪非迭代综合法的修正

对Tiwary非迭代综合法进行了整理分析,根据阴极半锥角大小的不同范围对其计算公式做出了相应修正,使得计算结果与Vaughan迭代综合法的计算结果相吻合,二者之间相差可以实现小于1°;对阳极半径公式也做了合理的修正,使阳极与阴极之间的间隙及电子枪射程的计算精度也与迭代综合法相当。采用非迭代法的修正方法计算精度受阴极半锥角大小的影响大大减小,扩大了其应用范围。

高精度测量射线荧光转换屏YAG晶体的点扩散函数

从理论和实验两方面研究了伽马射线荧光转换屏YAG晶体的空间分辨的影响因素,建立了高精度直接测量射线荧光转换屏点扩散函数的新方法.理论分析了伽马射线与YAG晶体作用产生次级电子对空间分辨的影响,采用蒙特卡罗程序计算了伽马射线荧光转换屏的空间分辨.使用高灵敏度图像记录系统记录了伽马射线与荧光转换屏YAG晶体作用产生次级电子在出射面上的投影.采用双针孔准直屏蔽体组成的等效超细长厚针孔对钴辐射源进行准直屏蔽,形成了准平行点辐射源射线束,直接获得了射线荧光转换屏的点扩散函数.测得的点扩散函数在半径为12 mm处,相对强度急剧下降为0.1%,并在半径为40 mm位置处逐渐降低为0.08%.

Characterization of Catalytic Cracking Catalysts Regenerated by Gasifying Deposited Coke

Partially or fully regenerated catalytic cracking catalysts were prepared by gasifying the coke deposited on coked catalysts with a gaseous mixture of oxygen and steam in a fixed fluidized bed （FFB）. The resultant samples were characterized by different methods such as the nitrogen adsorption-desorption analysis, the X-ray diffractometry, the infrared spectroscopy, the ammonia temperature-programmed desorption （NH3-TPD） method, the X-ray fluorescence （XRF） analysis, the transmission electron microscopy and energy dispersive X-ray spectroscopy （TEM-EDX）, the thermal-gravimetric analysis （TGA） and the differential thermal analysis （DTA）. The results showed that exposure of catalyst to steam for about 10 minutes at temperature ≥ 800 ℃ could not cause too much destruction of the catalysts, and an amount of coke equating to about 0.27 m% was enough to block approximately all acid sites in micro-pores of the zeolite catalyst. Coke didn＇t show equal reactivity during coke burning-off that could be accelerated by the catalytic action of nearby metal atoms. However, when the carbon content on the catalyst reached about 2.44 m%, the catalytic action of metals on the catalyst was not evident. The severe thermal and hydrothermal environment during exposure of the catalyst to steam at a temperature in the range of about 860--880 ℃ for 30 minutes could lead to collapse of pore structure and transformation of crystal phase and consequently decrease of the surface area and acid amount on the catalyst.

J/ψ and φ Electro-production in Pomeron Exchange Model

Based on Pomeron exchange model, J/ψ and φ production in electro-proton interaction are investigated with both linear and non-linear Pomeron trajectory. The experimental differential cross sections measured as a function of the kinematic variable Q^2,W and t are reproduced successfully in the model. Our conclusions are that the Pomeron exchange model is a successful description of J/ψ and φ electro-productions on the proton, and that the linear trajectory is a good approximation to non-linearity of the Pomeron trajectory.

Oxidation of Mercaptans from Light Oil Sweetening by Fe_2O_3/MgO/Al_2O_3 Supported CoPcS Catalyst

MgO/Al2O3 and Fe2O3/MgO/Al2O3 solid bases were prepared through mixing method. After sulfonated cobalt phthalocyanine （CoPcS） being supported on these solid bases, the catalytic performance of these catalysts was evaluated by means of mercaptan oxidation reaction. The samples were characterized by X-ray diffraction （XRD）, CO2 temperature-programmed desorption （CO2-TPD）, FTIR spectroscopy, and X-ray photoelectron spectroscopy （XPS）. Investigation was focused on the effect of Fe2O3 on activity, crystal structure, basicity, and stability of the catalyst and also on the role of Fe2O3 in the mercaptan oxidation processes. Test results have shown that the Fe2O3/MgO/Al2O3- CoPcS catalyst has a higher initial activity and a much longer service life than the MgO/Al2O3-CoPcS catalyst. The increased types of basic sites coupled with an enhanced oxidation ability resulted from the addition of Fe2O3 have contributed to the improvement of the catalytic activity of the MgO/Al2O3-CoPcS catalyst.

Performance of Ni/Nano-ZrO_2 Catalysts for CO Preferential Methanation

Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller （BET）, transmission electron microscope （TEM）, X-ray dif- fraction （XRD） and temperature-programmed reduction （TPR）. The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% （by mass） Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low.

Nested Bethe Ansatz for Spin Ladder Model with Open Boundary Conditions

The nested Bethe ansatz (BA) method is applied to find the eigenvalues and the eigenvectors of the transfer matrix for spin-ladder model with open boundary conditions. Based on the reflection equation, we find the general diagonal solution, which determines the generalboundary interaction in the Hamiltonian. We introduce the spin-ladder model with open boundary conditions. By finding the solution K± of the reflection equation which determines the nontrivial boundary terms in the Hamiltonian, we diagonalize the transfer matrix of the spin-ladder model with open boundary conditions in the framework of nested BA.

Study on effect of feed ratio on controlled cross-linking polymerization process

A controlled cross-linking polymerization containing intra- and intermolecular reactions was designed based on random coil morphology of macromolecules in solution. The soluble intramolecular cross-linked maeromolecule （ICM） was successfully synthesized in the system with PVA and MDI. We found an especial dissolving phenomenon, namely the semi-soluble phenomenon when some gels dissolved in DMF. The chain growth process of ICMs was investigated by Transmission electron microscopy （TEM） pictures of samples at different reacting times, in addition, TEM pictures show ICMs have three kinds of styles in structure, viz. ＂globule structure＂, ＂nubby structure＂ and the intervenient between the above two structures, and the efflux time of the ICMs was measured by an Ubbelohde viscosimeter, it was found that the efflux time decreases with the degree ofcrosslink increasing.

Calculation of the Energy Distribution of Electrons Emitted from Tungsten

The numerical calculation of the energy distribution of electrons emitted by the tungsten, for a triangular barrier and given reflection images, has been carried out. It is shown that the numerical solution of Schrodinger equation is the most effective method of calculation of the transparency of potential barrier among those used in work. I-V characteristics, which were calculated by the application of this method under different conditions, match the experimental data the best. The application of the numerical solution of Schrodinger equation for the calculation of transparency of the potential barrier enables the in-depth analysis of the tunnels phenomena and allows forecasting the effects which can not be received by application of Wentzel-Kramers-Brillouin approximation.

Microstructure Evolution at Different Cooling Rates of Low Carbon Microalloyed Steels

In low carbon microalloyed steels （C 〈 0.1%）, the content of V, Nb and Ti affects the phases transformation kinetic during cooling in the rolling process. The final microstructure determines the required mechanical properties such as high formability, high toughness and adequate strength. For this reason it is relevant to identify and determine the volume fraction of the ferrite, bainite and martensite present in the structure. The microalloying elements： V, Nb and Ti promote carbides precipitation during cooling. The precipitates control the grain size refinement during hot rolling process and the mechanical properties of the steel. In this sense it is necessary to increase the knowledge on the microstructure evolution at different cooling rates. In this paper, the results obtained on two low carbon microalloyed steels （with C contents between 0.11%-0.06%） are reported. An integrated methodology including dilatometry in combination with microscopy techniques was applied. By EBSD （Electron Backscatter Diffraction） technique and microhardness measurements, the structural study was completed. Through a thermodynamic simulation using Fact Sage the type of precipitates in the studied steels structure at the temperature range between 950 ℃ and 450 ℃, were predicted. The information on the evolution of the steel structure at rolling process conditions is relevant to consider changes in processing conditions.

Gold Supported on Metal Oxides for Carbon Monoxide Oxidation

Au has been loaded （1% wt.） on different commercial oxide supports （CuO, La2O3, Y2O3, NiO） by three different methods： double impregnation （DIM）, liquid-phase reductive deposition （LPRD）, and ultrasonication （US）. Samples were characterised by N2 adsorption at -196℃, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging （Z-contrast）, X-ray diffraction, and temperature programmed reduction. CO oxidation was used as a test reaction to compare the catalytic activities. The best results were obtained with Au loaded by DIM on the NiO support, with an activity of 7.2 × 10^（-4） molco·gAu^（-1）·s^（-1） at room temperature. This is most likely related to the Au nanoparticle size being the smallest in this catalyst （average 4.8 nm）, since it is well known that gold particle size determines the catalytic activity. Other samples, having larger Au particle sizes （in the 2-12 nm range, with average sizes ranging from 4.8 to 6.8 nm）, showed lower activities. Nevertheless, all samples prepared by DIM had activities （from 1.1 × 10^（-4） to 7.2 × 10^（-4） molco·gAu^（-1）·S^（-1）, at room temperature） above those reported in the literature for gold on similar oxide supports. Therefore, this method gives better results than the most usual methods of deposition-precipitation or co-precipitation.

Atomic process of oxidative etching in monolayer molybdenum disulfide

The microscopic process of oxidative etching of two-dimensional molybdenum disulfide(2D MoS_2) at an atomic scale is investigated using a correlative transmission electron microscope(TEM)-etching study.MoS_2 flakes on graphene TEM grids are precisely tracked and characterized by TEM before and after the oxidative etching. This allows us to determine the structural change with an atomic resolution on the edges of the domains, of well-oriented triangular pits and along the grain boundaries. We observe that the etching mostly starts from the open edges, grain boundaries and pre-existing atomic defects.A zigzag Mo edge is assigned as the dominant termination of the triangular pits, and profound terraces and grooves are observed on the etched edges. Based on the statistical TEM analysis, we reveal possible routes for the kinetics of the oxidative etching in 2D MoS_2, which should also be applicable for other 2D transition metal dichalcogenide materials like MoSe_2 and WS_2.

Photo-enhanced field electron emission of cadmium sulfide nanowires

The response of field electron emission of cadmium sulfide (CdS) nanowires (NWs) to visible light has been investigated.It is found that,upon light illumination,the turn-on voltage drops,emission current increases obviously,and the Fowler-Nordheim behavior deviates from a straight line.A process of field emission coupled with semiconducting properties of CdS NWs is proposed.Photon-excited electron transition from the valence band to the conductance band of CdS nanowires increases the quantity of emitting electrons,and the photoemission decreases the effective work function of CdS emitters,which largely enhances the field emission performance.The response of field emission of CdS NWs to light illumination suggests an approach for tuning field emission of semiconductor emitters.

Distribution and characteristics of telocytes as nurse cells in the architectural organization of engineered heart tissues

Interstitial Cajal-like cells are a distinct type of interstitial cell with a wide distribution in mammalian organs and tissues,and have been given the name"telocytes".Recent studies have demonstrated the potential roles of telocytes in heart development,renewal,and repair.However,further research on the functions of telocytes is limited by the complicated in vivo environment.This study was designed to construct engineered heart tissue(EHT)as a three-dimensional model in vitro to better understand the role of telocytes in the architectural organization of the myocardium.EHTs were constructed by seeding neonatal cardiomyocytes in collagen/Matrigel scaffolds followed by culture under persistent static stretch.Telocytes in EHTs were identified by histology,toluidine blue staining,immunofluorescence,and transmission electron microscopy.The results from histology and toluidine blue staining demonstrated widespread putative telocytes with compact toluidine blue-stained nuclei,which were located around cardiomyocytes.Prolongations from the cell bodies showed a characteristic dichotomous branching pattern and formed networks in EHTs.Immunofluorescence revealed positive staining of telocytes for CD34 and vimentin with typical moniliform prolongations.A series of electron microscopy images further showed that typical telocytes embraced the cardiomyocytes with their long prolongations and exhibited a marked appearance of nursing cardiomyocytes during the construction of EHTs.This finding highlights the great importance of telocytes in the architectural organization of EHTs.It also suggests that EHT is an appropriate physical and pathological model system in vitro to study the roles of telocytes during heart development and regeneration.

Anelasticity of twinned CuO nanowires

The mechanical behavior of CuO nanowires （NWs） was investigated by in situ transmission electron microscopy. During compression, the NWs exhibited high bending capabilities associated with high mechanical stress. Interestingly, anelasticity was consistently observed after stress release. Further investigations indicate that the anelasticity is intrinsic to the CuO NWs, although electron- beam irradiation was proved capable of accelerating the shape recovery. A mechanism based on the cooperative motion of twin-associated atoms is proposed to account for this phenomenon. The results provide insight into the mechanical properties of CuO NWs, which are promising materials for nanoscale damping systems.

Microstructure Evolution of Zr_(50)Cu_(18)Ni_(17)Al_(10)Ti_5 Bulk Metallic Glass during Cold-rolling

Zr5018Nil1AlTi10Ti5 bulk metallic glass has been rolled at room temperature up to 95% in thickness reduction, and the dependence of microstructure on the strain was investigated. With increasing thickness reduction, the full width at half maximum （FWHM） and crystallization enthalpy decrease gradually till 80%, and then increase evidently at 95%. It is revealed that the reversible transition between the ordered and disordered atomic configurations was found in the metallic glass as the deformation proceeds, which is further verified by the high-resolution transmission electron microscopy images. The final microstructure in metallic glass during cold-rolling is the net result of two competing processes between shear-induced disordering and diffusion controlled reordering.

Evolution of the ductile shear zone of the Paishanlou gold deposits,western Liaoning,China

The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction(EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event.The E-W-striking ductile shear zone,accompanied by compressional and dextral shear slip,was shear-cut by the NE-striking shear zones,accompanied by compressional-sinistral shear slip and sinistral-normal shear slip,successively.An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures,accompanied by abundant microstructures,including microlayering between a polycrystal quartz belt and mica,and quartz deformation was depended on cylinder(10-10) or <c> glide.The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian.The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures,accompanied by typical microstructures,including polycrystal quartz aggregation and quartz subgrain rotation recrystallization,etc.,and quartz deformation was depended on prismatic(1011) glide.The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels,yielding to a pre-existing NE-striking shear zone,accompanied by abundant microstructures,including low-temperature quartz grain boundary migration and bulging recrystallization.The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma,and this shear event resulted directly in the mineralization in the Paishanlou region.