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排序方式: 共有3615条查询结果,搜索用时 31 毫秒
971.
常温常压下吡咯及其衍生物的镍催化加氢反应考察   总被引:1,自引:0,他引:1  
为进一步研究常温常压下及其衍生物的镍催化加氢反应,我们对试剂吡咯、吡咯烷和吡咯烷酮做了相应的催化加氢实验。并采用电镜(TEM-HREM)、X射线衍射(XRD)对Ni基催化剂的形貌、结构、加氢活性和超声波对其影响进行了检测,同时不用紫外吸收光谱、气相色谱等对加氢产物进行了分析考察。结果表明超声波能促进镍催化剂活性,使镍微晶(111)晶面间距增大1.5%,并保持高分状态。常温常压下纳米镍基催化剂对吡咯、吡咯烷和吡咯烷酮的加氢反应显示一定的催化活性;吡咯加氢首先生成吡咯烷,进而使环打开生成低碳烃、氨等产物,总反应为零级,符合表面接触反应特征。  相似文献   
972.
对照中药材红外光谱数据库的研制与应用   总被引:7,自引:0,他引:7  
在选定的化学处理条件下 ,测定了对照中药材的红外光谱。采用现代电子科学技术 ,建立了对照中药材红外光谱数据库 ,应用于中药材的品种鉴别。该数据库对照中药材样品具有各自比较鲜明的红外光谱指纹特征 ,可以通过拉丁学名进行检索 ,快速鉴别中药材以及区分中药材真伪品 ,为中药材鉴定技术标准化、规范化探索了一条新途径  相似文献   
973.
对槲寄生中的有效成分高圣草素-7-O-β-D-葡萄糖苷进行了分离和结构鉴定,并对其含量进行了分析。色谱条件:C18柱(200 mm×4.6 mm i.d., 5 μm),流动相为乙腈-0.5%冰醋酸水溶液(体积比为18∶82),流速为1.0 mL/min,柱温为30 ℃,检测波长为284 nm,进样量为10 μL。结果表明,高圣草素-7-O-β-D-葡萄糖苷的峰面积与其质量浓度有良好的线性关系,相关系数r为0.9997;方法的加标回收率为96.0%~100.1%。该方法简便、快速、准确,精密度好,可作为槲寄生质量控制的一个有效方法。  相似文献   
974.
在气动外形优化中, 采用近似模型管理结构(AMF)方法,对变可信度模型进行组织和管理.这样能够充分利用低可信度模型,将主要计算量集中在低可信度模型的优化迭代过程中.同时,采用高可信度模型监控优化过程,使最终的优化解收敛到高可信度模型上.最后,设计了零阶变可信度气动特性优化管理结构与搜索算法,对某飞翼型无人机的翼型进行了气动优化.优化外形的气动性能与初始外形比有所提高.实际结果表明所提出的方法具有良好的可行性和适用性.  相似文献   
975.
吴志猛  雷青松  耿新华  赵颖  孙建  奚建平 《中国物理》2006,15(11):2713-2717
This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (SiH\sj{*}, H微晶硅 VHF-PECVD 发射光谱学 薄膜物理学microcrystalline silicon, VHF-PECVD, optical emission spectroscopy2005-11-092005-11-092005-12-12This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (Sill^*, H^* and H^*β) are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6%. The SiH^* intensity increases with silane concentration, while the intensities of H^*α and H^*β increase first and then decrease. When the substrate temperature increases, the SiH^* intensity decreases and the intensities of H^*α and H^*β are constant. The correlation between the intensity ratio of IH^*α/ISiH^* and the crystalline volume fraction (Xc) of films is confirmed.  相似文献   
976.
The near-threshold highly bound states of all three stable isotopic variants of molecular hydrogen have been studied. Numerous perturbations and unexpected transitions are observed as far as 1cm\sj{-1} just below the second dissociation threshold. This complex structure may arise from a combination of nonadiabatic coupling between B, B', C electronic states, perturbations due to fine and hyperfine interactions, and strong shape resonances. The perturbed near-threshold states and vibrational continuum exhibit finegrained structure, differing greatly between isotopes because of varying nonadiabatic coupling.  相似文献   
977.
A single microscopic magnetic trap for neutral atoms using planar current-carrying wires was proposed and studied theoretically by Weinstein et al.In this paper,we propose three structures of composite current-carrying wires to provide 1D,2D and 3D arrays of microscopic magnetic traps for cold alkali atoms.The spatial distributions of magnetic fields generated by these structures are calculated and the field gradient and curvature in each single microtrap are analysed.Our study shows that arrays of microscopic magnetic traps can be used to provide 1D,2D or 3D atomic magnetic lattices,and even to realize 1D,2D and 3D arrays of magneto-optical traps,and so on.  相似文献   
978.
印建平  高伟建  王海峰  龙全  王育竹 《中国物理》2002,11(11):1157-1169
We report on a new experimental result to generate dark hollow beams by using a geometric optical method. We propose two new methods to produce focused and localized hollow laser beams by using π-phase plates. Using Monte-Carlo simulations, we have studied the Sisyphus cooling of alkali atoms in pyramidal hollow beam gravito-optical traps. We discuss some potential applications of the dark hollow beams in atom optics and the preparation of an all optically-cooled and optically-trapped atomic Bose-Einstein condensation (BEC). Our research shows that an ultracold atomic sample with a temperature of ~ 2μK can be obtained in the pyramidal hollow beam dipole trap and an all optical-type BEC may be realized in a far blue-detuned, hollow beam trap.  相似文献   
979.
邓联忠  夏勇  印建平 《中国物理》2007,16(3):707-717
This paper proposes a scheme to guide cold polar molecules by using a single charged wire half embanked in an insulating substrate and a homogeneous bias electric field, which is generated by a plate capacitor composed of two infinite parallel metal plates. The spatial distributions of the electrostatic field produced by the combination of the charged wire and the plate capacitor and the corresponding Stark potentials (including dipole forces) for metastable CO molecules are calculated, the relationships between the electric field and the parameters of our charged-wire layout are analysed. It also studies the influences of the insulator on the electric field distribution and the discharge effect. This study shows that the proposed scheme can be used to guide cold polar molecules in the weak-field -- seeking states, and to form various molecule-optical elements, such as molecular funnel, molecular beam-splitters and molecule interferometer, even to construct a variety of integrated molecule-optical elements and their molecule chips.  相似文献   
980.
This paper explores the potential of controlling quantum systems by introducing ancillary systems and then performing unitary operation on the resulting composite systems. It generalizes the concept of pure state controllability for quantum systems and establishes the link between the operator controllability of the composite system and the generalized pure state controllability of its subsystem. It is constructively demonstrated that if a composite quantum system can be transferred between any pair of orthonormal pure vectors, then its subsystem is generalized pure-state controllable. Furthermore, the unitary operation and the coherent control can be concretely given to transfer the system from an initial state to the target state. Therefore, these properties may be potentially applied in quantum information, such as manipulating multiple quantum bits and creating entangled pure states. A concrete example has been given to illustrate that a maximally entangled pure state of a quantum system can be generated by introducing an ancillary system and performing open-loop coherent control on the resulting composite system.  相似文献   
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