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The upgrade project of the Beijing Electron Positron Collider (BEPCII) and its injector linac is working well. The linac upgrade aims at a higher injection rate of 5OmA/min into the storage ring, which requires an injected beam with low emittance, low energy spread and high beam orbit and energy stabilities. This goal is finally reached recently by upgrading the linac components and by dealing with rich and practical beam physics, which are described in this study. 相似文献
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Hang Xu Shi-Jun Liao Xiang-Cheng You 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):1152-1156
In this paper, the time fractional partial differential equations are investigated by means of the homotopy analysis method. This technique is extended to study the partial differential equations of fractal order for the first time. The accurate series solutions are obtained. This indicates the validity and great potential of the homotopy analysis method for solving nonlinear fractional partial differential equations. 相似文献
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一维链状配位聚合物{[Pb(PTCP)(2,5-pydc)]_2·H_2O}_n的水热合成、晶体结构和发光性质研究(英文) 总被引:1,自引:1,他引:0
A new metal-organic coordination compound framework formulated {[Pb(PTCP)(2,5-pydc)]2·H2O}n (1) (PTCP=2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]-phenanthrene, H2pydc=pyridine-2,5-dicarboxylic acid) has been prepared in the hydrothermal condition and characterized by single-crystal X-ray diffraction, elemental analysis, IR and TG. It crystallizes in monoclinic, space group C2/c with a=2.129 2(4) nm, b=1.111 2(2) nm, c=2.049 4(4) nm, β=105.02(3)°, V=4.683 2(16) nm3, Z=4, Pb2C52H32N10O9, Mr=1 355.26, Dc=1.922 g·cm-3, F(000)=2 600, S= 0.825, R1=0.056 2 and wR2=0.168 9. In the crystal, the Pb atom is five-coordinated by three N and two O atoms. The complex forms a one-dimensional zigzag polymeric chain along the b axis which is stacked to furnish a two- dimensional supramolecular layer structure via aromatic π-π interactions in the ab plane. In addition, hydrogen bonds are observed in the compound which play an important role in forming the final structure. Solid-state fluorescence spectrum of 1 exhibits the maximum emission peak at 621 nm. 相似文献
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A new type of magnetic core-shell Ni–Ce nanocomposite particles (15–50 nm) is presented. SEM observations suggest the particles are strongly ferromagnetic, interacting with ordered chain-like features. Typical HR-TEM images demonstrate that many planar defects (nanotwins and stacking faults) exist in the surface shell and large Ni core zone (10–40 nm) of the particles; the inner shell layers (4–6 nm) consist of NiCe alloy and the outermost shell is NiO. Nano-diffraction patterns show an indication of well-defined spots characteristic of nanocomposite materials, of which certain crystal facet orientation relationships between orthorhombic [111] of NiCe and cubic [311] of Ni2Ce, face-center crystal [222] of NiO, cubic [111] of nickel have been identified. This confirms the nature of this core-shell nanocomposite particle. 相似文献
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Molecular oxygen is a radical scavenger in both conventional and controlled radical polymerization(CRP), resulting in many time-consuming methods for physically removing oxygen before the polymerization. Different approaches have been developed to have oxygen tolerance by chemically consuming or converting molecular oxygen into non-initiating species to address this issue. Recently, we propose another approach called oxygen initiation that directly transforms molecular oxygen into the initiating... 相似文献
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In this paper, the laminar film condensation of saturated stream on an isothermal vertical plate is studied. The boundary layer equations of momentum and thermal energy are reduced to two ordinary differential equations by means of a set of similarity transformations. The problem is then solved analytically using the homotopy analysis method (HAM). The dual solutions are obtained for a range of values of the parameter ηδ. However, it should be noted that the second branch solution of the considered problem has only mathematical meanings. The present work shows the validity and the great potentiality of the proposed technique for the nonlinear problems with multiple solutions. 相似文献
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木糖转化到糠醛一般包括两步: 首先在酶、碱或路易斯(L)酸的催化作用下异构化木糖到木酮糖, 接下来木酮糖在酸的作用下脱水得到糠醛. 针对木糖水相脱水一步制备糠醛, 利用十六烷基三甲基溴化铵(CTAB)为模板剂, 借助软模板合作策略制备了一种抗水的新型固体酸催化剂, 介孔磷酸铌, 并利用X射线衍射(XRD)、N2吸脱附、透射电镜(TEM)、氨气程序升温脱附(NH3-TPD)和吡啶吸附傅里叶变换红外(Py-FTIR)光谱对材料的结构和酸性质进行了表征. 研究发现介孔磷酸铌不仅具有很高的比表面积(>200 m2·g-1), 比较窄的孔径分布(3.5nm), 同时还具有很强的L酸性和布朗斯特(B)酸性. 通过L酸催化的木糖异构化为木酮糖/来苏糖和B酸催化的木酮糖/来苏糖进一步脱水得到糠醛, 实现了一步由木糖到糠醛的高效转化. 为了优化反应条件, 考察了水溶液中反应温度、投料质量比及反应时间对木糖转化率和糠醛收率的影响, 在最佳的反应条件下, 木糖的转化率为96.5%, 糠醛的收率达49.8%. 进一步地, 为了提高收率且易于分离, 利用4-甲基-2-戊酮(MIBK)/NaCl水溶液(体积比为7:3)作为反应混合溶剂, 使糠醛收率提高到68.4%. 相似文献