期刊文献+
共找到114篇文章
< 1 2 6 >
每页显示 20 50 100
Selection rules for electric multipole transition of triatomic molecule in scattering experiments 被引量:1
1
作者 Hong-Chun Tian Long-Quan Xu Lin-Fan Zhu 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第4期258-263,共6页
In the electron or x-ray scattering experiment,the measured spectra at larger momentum transfer are dominated by the electric dipole-forbidden transitions,while the corresponding selection rules for triatomic molecule... In the electron or x-ray scattering experiment,the measured spectra at larger momentum transfer are dominated by the electric dipole-forbidden transitions,while the corresponding selection rules for triatomic molecules have not been clearly elucidated.In this work,based on the molecular point group,the selection rules for the electric multipolarities of the electronic transitions of triatomic molecules are derived and summarized into several tables with the variation of molecular geometry in the transition process being considered.Based on the summarized selection rules,the electron energy loss spectra of H2O,CO2,and N2O are identified,and the momentum transfer dependence behaviors of their valence-shell excitations are explained. 展开更多
关键词 electric multipole transition selection rule molecular point group electron scattering
下载PDF
Nonlinear Propagation of Coupling Optical Pulse under Compton Scattering in Laser Medium 被引量:1
2
作者 HAO Dong-shan ZHANG Xiao-fu 《Semiconductor Photonics and Technology》 CAS 2006年第3期178-183,204,共7页
After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse und... After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides, the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium. 展开更多
关键词 Laser amplifying medium Compton scattering group velocity dispersion Gain distribution
下载PDF
Selection rules for electric multipole transition of diatomic molecule in scattering experiments
3
作者 朱林繁 田红春 +2 位作者 刘亚伟 康旭 刘国兴 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第4期1-5,共5页
The knowledge of the energy level structures of atoms and molecules is mainly obtained by spectroscopic experiments. Both photoabsorption and photoemission spectra are subject to the electric dipole selection rules (... The knowledge of the energy level structures of atoms and molecules is mainly obtained by spectroscopic experiments. Both photoabsorption and photoemission spectra are subject to the electric dipole selection rules (also known as optical selection rules). However, the selection rules for atoms and molecules in the scattering experiments are not identical to those in the optical experiments. In this paper, based on the theory of the molecular point group, the selection rules are derived and summarized for the electric monopole, electric dipole, electric quadrupole, and electric octupole transitions of diatomic molecules under the first Born approximation in scattering experiments. Then based on the derived selection rules, the electron scattering spectra and x-ray scattering spectra of H2, N2, and CO at different momentum transfers are explained, and the discrepancies between the previous experimental results measured by different groups are elucidated. 展开更多
关键词 selection rule molecular point group electron scattering x-ray scattering
下载PDF
A UNIFIED APPROACH FOR DEALING WITH THE EM SCATTERING FROM SYMMETRIC AND ANTI-SYMMETRIC STRUCTURES
4
作者 郭英杰 《Journal of Electronics(China)》 1990年第4期377-381,共5页
It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group the... It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group theory is presented to deal with the EM scattering fromsymmetric and anti-symmetric structures. 展开更多
关键词 EM scattering SYMMETRIC and anti-symmetric STRUCTURES generalized image METHOD group theory INTEGRAL EQUATIONS METHOD
下载PDF
中非铜矿带恩古巴群铜多金属矿床地质特征与找矿潜力
5
作者 汤钰御 刘高杰 +5 位作者 陈向平 谢建平 王鹏飞 王纪昆 王建青 冀建军 《矿产勘查》 2024年第8期1445-1455,共11页
中非铜矿带是世界上最重要的以沉积岩为容矿岩石的铜钴多金属成矿区,本文通过对中非铜矿带恩古巴群典型铜多金属矿床的地质特征、地球化学特征、成矿作用和矿床规模、矿石品位等几个方面进行对比分析,获得以下认识:(1)恩古巴群存在多个... 中非铜矿带是世界上最重要的以沉积岩为容矿岩石的铜钴多金属成矿区,本文通过对中非铜矿带恩古巴群典型铜多金属矿床的地质特征、地球化学特征、成矿作用和矿床规模、矿石品位等几个方面进行对比分析,获得以下认识:(1)恩古巴群存在多个具有重要经济价值的铜(锌铅银)多金属矿床,以Kamoa-Kakula、Fishtie、Lonshi和Kipushi等为典型代表,这些矿床规模大、品位高,表明恩古巴群也是本区重要的含矿层位之一;(2)恩古巴群典型矿床多位于同沉积断层附近,新元古代加丹加盆地中温、高盐度的氧化性含矿流体通过底辟作用在恩古巴群底部沉积形成层状矿体;(3)恩古巴群地层在中非铜矿带分布广泛,前陆盆地、穹隆区域外围均是良好的找矿地段,具有巨大的资源潜力和找矿前景。 展开更多
关键词 恩古巴群 含矿层位 铜(锌铅银)多金属矿床 中非铜矿带
下载PDF
基于组稀疏学习与AVOA-XGBoost的轴承故障分级诊断
6
作者 张吉祥 张孟健 +1 位作者 王德光 杨明 《振动与冲击》 EI CSCD 北大核心 2024年第18期96-105,共10页
针对工业设备中轴承振动信号在噪声环境下故障分级诊断准确率低的问题,提出一种基于组稀疏学习与非洲秃鹫优化算法优化极端梯度提升树(African vultures optimization algorithm-extreme gradient boosting,AVOA-XGBoost)的轴承故障分... 针对工业设备中轴承振动信号在噪声环境下故障分级诊断准确率低的问题,提出一种基于组稀疏学习与非洲秃鹫优化算法优化极端梯度提升树(African vultures optimization algorithm-extreme gradient boosting,AVOA-XGBoost)的轴承故障分级诊断方法。首先,利用组稀疏学习对轴承振动信号进行重构,以降低噪声水平并更有效地表征故障脉冲。然后,对重构后的信号提取时域、频域和熵值特征并构建特征集。最后,利用AVOA自适应优化XGBoost超参数以建立稳健的XGBoost模型,进而高效实现轴承故障分级诊断。试验结果表明,经过组稀疏学习重构的信号具备更强故障特征表示能力,相较于传统机器学习模型,采用AVOA-XGBoost模型进行分类能够取得更高准确率,所提方法能够有效诊断轴承故障类型及故障程度。 展开更多
关键词 轴承故障诊断 组稀疏学习 特征提取 非洲秃鹫优化算法 XGBoost
下载PDF
Where Is Phase Velocity in Minkowski Space?
7
作者 Antony J. Bourdillon 《Journal of Modern Physics》 2024年第10期1555-1566,共12页
In the special theory of relativity, massive particles can travel at neither the speed of light c nor faster. Meanwhile, since the photon was quantized, many have thought of it as a point particle. How pointed? The id... In the special theory of relativity, massive particles can travel at neither the speed of light c nor faster. Meanwhile, since the photon was quantized, many have thought of it as a point particle. How pointed? The idea could be a mathematical device or physical simplification. By contrast, the preceding notion of wave-group duality has two velocities: a group velocity vg and a phase velocity vp. In light vp = vg = c;but it follows from special relativity that, in massive particles, vp > c. The phase velocity is the product of the two best measured variables, and so their product constitutes internal motion that travels, verifiably, faster than light. How does vp then appear in Minkowski space? For light, the spatio-temporal Lorentz invariant metric is s2=c2t2−x2−y2−z2, the same in whatever frame it is viewed. The space is divided into 3 parts: firstly a cone, symmetric about the vertical axis ct > 0 that represents the world line of a stationary particle while the conical surface at s = 0 represents the locus for light rays that travel at the speed of light c. Since no real thing travels faster than the speed of light c, the surface is also a horizon for what can be seen by an observer starting from the origin at time t = 0. Secondly, an inverted cone represents, equivalently, time past. Thirdly, outside the cones, inaccessible space. The phase velocity vp, group velocity vg and speed of light are all equal in free space, vp = vg = c, constant. By contrast, for particles, where causality is due to particle interactions having rest mass mo > 0, we have to employ the Klein-Gordon equation with s2=c2t2−x2−y2−z2+mo2c2. Now special relativity requires a complication: vp.vg = c2 where vg c and therefore vp > c. In the volume outside the cones, causality due to light interactions cannot extend beyond the cones. However, since vp > c and even vp >> c when wavelength λ is long, extreme phase velocities are then limited in their causal effects by the particle uncertainty σ, i.e. to vgt ± σ/ω, where ω is the particle angular frequency. This is the first time the phase range has been described for a massive particle. 展开更多
关键词 Event Horizon scattering Range Wave Packet Phase Velocity group Velocity Dispersion Dynamics Quantum Physics
下载PDF
A series solution for surface motion amplification due to underground group cavities:Incident P waves 被引量:3
8
作者 LIANG Jian-wen(梁建文) ZHANG Hao(张浩) Vincent W Lee 《Acta Seismologica Sinica(English Edition)》 CSCD 2004年第3期296-307,共12页
A series solution for surface motion amplification due to underground group cavities for incident plane P waves is derived by Fourier-Bessel series expansion method. It is shown that underground group cavities signifi... A series solution for surface motion amplification due to underground group cavities for incident plane P waves is derived by Fourier-Bessel series expansion method. It is shown that underground group cavities significantly am-plify the surface ground motion nearby. It is suggested that the effect of subways on ground motion should be con-sidered when the subways are planned and designed. 展开更多
关键词 underground group cavities surface motion plane P wave scattering series solution CLC number: P315.3 Document code: A
下载PDF
Transmission Eigenvalues and the Riemann Zeta Function in Scattering Theory for Automorphic Forms on Fuchsian Groups of Type Ⅰ
9
作者 Fioralba CAKONI Sagun CHANILLO 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2019年第6期987-1010,共24页
We introduce the concept of transmission eigenvalues in scattering theory for automorphic forms on fundamental domains generated by discrete groups acting on the hyperbolic upper half complex plane. In particular, we ... We introduce the concept of transmission eigenvalues in scattering theory for automorphic forms on fundamental domains generated by discrete groups acting on the hyperbolic upper half complex plane. In particular, we consider Fuchsian groups of Type Ⅰ. Transmission eigenvalues are related to those eigen-parameters for which one can send an incident wave that produces no scattering. The notion of transmission eigenvalues, or non-scattering energies, is well studied in the Euclidean geometry, where in some cases these eigenvalues appear as zeros of the scattering matrix. As opposed to scattering poles,in hyperbolic geometry such a connection between zeros of the scattering matrix and non-scattering energies is not studied, and the goal of this paper is to do just this for particular arithmetic groups.For such groups, using existing deep results from analytic number theory, we reveal that the zeros of the scattering matrix, consequently non-scattering energies, are directly expressed in terms of the zeros of the Riemann zeta function. Weyl's asymptotic laws are provided for the eigenvalues in those cases along with estimates on their location in the complex plane. 展开更多
关键词 TRANSMISSION EIGENVALUES Fuchsian groups RIEMANN ZETA function scattering theory
原文传递
Structural and Chemical Characteristic of Tourmaline, and Mineralogy of Associated Micas from Tourmaline Bearing Quartzite of KombéII (Bafia Group, Central Africa Fold Belt);Implication on the Metamorphic Conditions
10
作者 Ganwa Alembert Alexandre Klötzli Urs +3 位作者 Tchakounté Numbem Jacqueline Klötzli Eva Ertl Andreas Djom Bernard 《International Journal of Geosciences》 CAS 2022年第10期882-904,共23页
Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had be... Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na<sub>0.95</sub>[]<sub>0.05</sub>)Y(Mg<sub>2.39</sub>Fe<sub>0.61</sub>)Z(Al<sub>5.10</sub>Mg<sub>0.90</sub>)(BO<sub>3</sub>)<sub>3</sub>T[Si<sub>6</sub>O<sub>18</sub>](OH)<sub>3</sub>[(O,OH)<sub>0.88</sub>F<sub>0.12</sub>]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750&#8451;. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825&#8451;. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area. 展开更多
关键词 Fe-Dravite Structure Refinement Accessory Mineral Metamorphic Condition Kombé II Bafia group Central african Fold Belt
下载PDF
三重冲击下农业企业如何实现供应链韧性提升?--以温氏为例 被引量:4
11
作者 朱战国 张彤 《南京农业大学学报(社会科学版)》 CSSCI 北大核心 2023年第5期178-190,共13页
面对环境规制、非洲猪瘟疫情与新冠疫情的三重叠加冲击,维护生猪供应链稳定运行、培育生猪供应链韧性是推动生猪产业持续健康发展的重要基础。在引导养殖户衔接农业现代化发展的进程中,温氏立足“公司+农户”模式的存续与创新,实现了三... 面对环境规制、非洲猪瘟疫情与新冠疫情的三重叠加冲击,维护生猪供应链稳定运行、培育生猪供应链韧性是推动生猪产业持续健康发展的重要基础。在引导养殖户衔接农业现代化发展的进程中,温氏立足“公司+农户”模式的存续与创新,实现了三重冲击下生猪供应链韧性的提升。本文基于纵向时序嵌入式单案例研究法,分析温氏生猪供应链的调整过程,揭示温氏生猪供应链韧性策略的形成机制,以及不同冲击发生期韧性策略间的互动过程。研究发现:温氏基于“准备、反应、恢复、适应”四个阶段,构建了生猪供应链韧性策略;强化“公司+农户”模式合作紧密性以提升供应链整合强度,是供应链延伸发展后经济产出提升的基础;多重冲击的叠加能够促进温氏生猪供应链双元性能力的形成,前一冲击发生期“适应阶段”的生猪供应链韧性策略,在延续至下一冲击发生期的同时,也为下一冲击发生期“恢复阶段”韧性策略的实施奠定基础;同时,特定制度因素会促进或阻碍关键资源向生猪供应链韧性的转变,也会促进或阻碍供应链韧性对生猪供给分布与供给总量的作用过程。据此,本文提出缓解生猪供应链韧性重要约束,基于“公司+农户”模式继续推动生猪供应链持续健康发展的政策建议。 展开更多
关键词 生猪供应链韧性 环境规制 非洲猪瘟 多重冲击 温氏
下载PDF
中非走滑裂谷盆地群石油地质特征与勘探方向 被引量:2
12
作者 何文渊 王利 +5 位作者 汪望泉 肖坤叶 杜业波 吴亚东 马明福 潘春孚 《中国石油勘探》 CAS CSCD 北大核心 2023年第3期90-99,共10页
中非走滑裂谷盆地群是在中非剪切带影响下形成的中、新生代陆相裂谷盆地,构造复杂多样且勘探程度较低,成藏规律认识不清制约了该区的油气勘探发现。基于盆地构造、沉积、成藏组合特征和已发现油气田解剖,总结盆地油气富集规律和主控因素... 中非走滑裂谷盆地群是在中非剪切带影响下形成的中、新生代陆相裂谷盆地,构造复杂多样且勘探程度较低,成藏规律认识不清制约了该区的油气勘探发现。基于盆地构造、沉积、成藏组合特征和已发现油气田解剖,总结盆地油气富集规律和主控因素,并分析了勘探潜力和方向。研究认为,中非走滑裂谷盆地群在早白垩世以来经历了多期伸展、走滑和反转等构造活动,对沉积地层、构造特征和油气成藏具有较强的控制作用;受储盖组合和构造演化的影响,中非走滑裂谷盆地群不同盆地的油气发现和成藏组合有较大差异,总体表现为“西富东贫、下稀上稠”的特点;油气富集的主控因素是有效生烃灶、构造活动和断层;西部Doba盆地油气最为富集,发育多套成藏组合,上、下白垩统均已经获得规模发现,未来主要勘探方向包括下白垩统岩性圈闭和基岩圈闭;中部Doseo盆地上白垩统缺乏有效盖层,主要勘探目标为下白垩统砂泥岩组合,圈闭类型为走滑形成的断背斜、断块圈闭,基岩潜山是潜在的勘探目的层;东部的Salamat盆地尚未证实有效的成藏组合,勘探潜力有限。 展开更多
关键词 中非走滑裂谷盆地群 储盖组合 构造演化 Doba盆地 Doseo盆地
下载PDF
亚硝态氮胁迫对斑节对虾(非洲群体)氧化应激、能量代谢和渗透调节的影响 被引量:1
13
作者 刘吉丹 刘洪军 +5 位作者 樊英 唐学玺 王晓璐 王友红 盖春蕾 叶海斌 《水产学报》 CAS CSCD 北大核心 2023年第4期40-50,共11页
为研究亚硝态氮(NO2-N)对斑节对虾(非洲群体)氧化应激、能量代谢和渗透平衡的影响,实验选取体长(3.0±0.5)cm的斑节对虾,设置0(对照组)、5、10和15 mg/L(3个胁迫组)的亚硝态氮浓度梯度,进行了为期72 h的急性胁迫。实验结果显示,肝... 为研究亚硝态氮(NO2-N)对斑节对虾(非洲群体)氧化应激、能量代谢和渗透平衡的影响,实验选取体长(3.0±0.5)cm的斑节对虾,设置0(对照组)、5、10和15 mg/L(3个胁迫组)的亚硝态氮浓度梯度,进行了为期72 h的急性胁迫。实验结果显示,肝胰腺氧化应激因子活性(或含量)随着胁迫时间发展而变化。超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)以及一氧化氮合酶(NOS)活性先升高后下降,24 h,SOD和GSH-Px、NOS活性达到最大值,10 mg/L胁迫组的SOD、GSH-Px活性和15 mg/L胁迫组的NOS活性显著高于其他3组;丙二醛(MDA)含量变化相反,24 h胁迫组的MDA含量最小,其中10 mg/L胁迫组显著低于其他3组;48 h,CAT活性达到最大值,10 mg/L胁迫组显著高于其他3组;一氧化氮(NO)含量随着胁迫时间的延长而逐渐升高,72 h,NO含量最高,15 mg/L胁迫组显著高于其他3组。血清能量代谢指标中脂肪酶(LPS)活性先上升后下降,48 h,LPS活性达到最大值,其中10 mg/L胁迫组显著高于其他3组;而己糖激酶(HK)、磷酸果糖激酶(PFK)、丙酮酸激酶(PK)活性和甘油三酯(TG)含量明显下降,72 h,HK、PFK、PK活性和TG含量达到最小值,15 mg/L胁迫组显著低于其他3组。鳃丝中渗透调节参数——Na^(+)、K^(+)-ATP酶(Na^(+)、K^(+)-ATPase)活性在胁迫过程中始终下降,经过72 h的亚硝态氮胁迫,Na^(+)、K^(+)-ATPase活性达到最小值,15 mg/L胁迫组显著低于其他3组。研究表明,斑节对虾可通过提高抗氧化能力,增强对脂质吸收和利用,调节原有渗透平衡来应对亚硝态氮胁迫,这种作用的发挥具有一定的时间和浓度限制。本实验将为进一步探索亚硝态氮胁迫的分子机制提供数据支持。 展开更多
关键词 斑节对虾(非洲群体) 亚硝态氮 抗氧化应激 能量代谢 离子渗透
下载PDF
基于中子均方位移守恒的平均散射角余弦计算
14
作者 秦帅 李云召 +2 位作者 贺清明 曹良志 吴宏春 《哈尔滨工程大学学报》 EI CAS CSCD 北大核心 2023年第12期2208-2215,共8页
使用蒙特卡罗方法计算均匀化群常数时,一般以中子标通量为权重计算平均散射角余弦,会引入额外的计算误差。针对该问题,本文从中子均方位移和平均散射角余弦的关系出发,根据中子均方位移的统计结果,计算得到保证该物理量守恒的平均散射... 使用蒙特卡罗方法计算均匀化群常数时,一般以中子标通量为权重计算平均散射角余弦,会引入额外的计算误差。针对该问题,本文从中子均方位移和平均散射角余弦的关系出发,根据中子均方位移的统计结果,计算得到保证该物理量守恒的平均散射角余弦。基于蒙特卡罗粒子输运计算程序NECP-MCX,并使用各向异性较强的快中子反应堆问题对该方法进行了测试。相比于传统方法,反应堆有效增殖因子的偏差由588×10^(-5)~796×10^(-5)降低为-31×10^(-5)~266×10^(-5),相对裂变反应率分布的最大相对偏差由3.754%~4.675%降低为-0.990%~0.920%,均方根偏差由1.864%~2.444%降低为0.569%~0.612%。结果表明:本文方法可以可以有效降低传统方法的计算偏差,具有一定的应用价值。 展开更多
关键词 均方位移 平均散射角余弦 群常数 蒙特卡罗方法 NECP-MCX 各向异性 反应堆物理 两步法计算
下载PDF
原位液体室透射电镜观察二氧化硅纳米颗粒的合并生长
15
作者 杨天旭 徐旭荣 唐睿康 《材料科学与工程学报》 CAS CSCD 北大核心 2023年第1期6-12,38,共8页
利用原位液体室透射电子显微镜实时观察硅酸钠溶液中二氧化硅纳米颗粒的生长过程,同时使用动态光散射对纳米颗粒尺寸分布进行原位监测。通过对该动态过程的定量分析,研究了二氧化硅纳米颗粒的生长机理。结果表明,硅酸钠溶液中二氧化硅... 利用原位液体室透射电子显微镜实时观察硅酸钠溶液中二氧化硅纳米颗粒的生长过程,同时使用动态光散射对纳米颗粒尺寸分布进行原位监测。通过对该动态过程的定量分析,研究了二氧化硅纳米颗粒的生长机理。结果表明,硅酸钠溶液中二氧化硅纳米颗粒主要是通过合并的方式进行生长。在合并的过程中,颗粒会自发地进行连续合并或发生形状改变,以降低单位体积表面能。进一步的结果分析显示,二氧化硅纳米颗粒的合并生长符合基于Smoluchowski速率方程的动力学,接近于受反应控制的聚集生长,其化学本质是颗粒表面羟基间的脱水缩合反应。 展开更多
关键词 二氧化硅纳米颗粒 原位液体室透射电镜 合并生长 动态光散射 羟基
下载PDF
The group theory for solving electromagnetic scattering problems with geometric symmetric structure
16
作者 朱峰 杨海川 任朗 《Science China(Technological Sciences)》 SCIE EI CAS 1997年第2期206-213,共8页
It is a very important issue to reduce computer storage and calculation time for matrix in solving scattering field by making use of geometric and physical symmetric features of a scattering body. A general definition... It is a very important issue to reduce computer storage and calculation time for matrix in solving scattering field by making use of geometric and physical symmetric features of a scattering body. A general definition for the symmetric and anti-symmetric structure is given by applying the group theory in mathematics and a general method for treating the electromagnetic scattering problems with symmetry is proposed. An example for applying the theory mentioned above is also given. 展开更多
关键词 direct product group CHARACTERISTIC sub-group ELECTROMAGNETIC scattering.
原文传递
Group Theory Approach for the Stimulated Raman Scattering in Fiber
17
作者 YangBojun GuoWanwen 《The Journal of China Universities of Posts and Telecommunications》 EI CSCD 1995年第1期55-58,共4页
The symmetry of rotation vibration spectra of molecule SiO_2 is described by means of group U(5). Grouptheory approach is adopted to give the matrix elements of stimulated Raman scattering in fiber. The cross sections... The symmetry of rotation vibration spectra of molecule SiO_2 is described by means of group U(5). Grouptheory approach is adopted to give the matrix elements of stimulated Raman scattering in fiber. The cross sectionsand gain coefficients of stimulated Raman scattering are given. The results are in good agreement with the experi-mental values. 展开更多
关键词 U(5) model stimulated Raman scattering transition matrix elements group theory approach
原文传递
不同重均相对分子质量和氨基含量壳聚糖的制备及测定 被引量:5
18
作者 李沁华 陈光炜 +3 位作者 屠美 陈文心 王赟 黄耀熊 《暨南大学学报(自然科学与医学版)》 CAS CSCD 2002年第3期89-92,共4页
目的 :制备出不同 -NH2 质量分数和不同重均相对分子质量的精细壳聚糖制品 ,利用激光散射仪测定在不同脱乙酰条件下所获得的壳聚糖重均相对分子质量 .方法 :利用反应温度为 14 0℃ ,反应时间为 1~ 4h和反应温度为 30℃ ,反应时间为 7d... 目的 :制备出不同 -NH2 质量分数和不同重均相对分子质量的精细壳聚糖制品 ,利用激光散射仪测定在不同脱乙酰条件下所获得的壳聚糖重均相对分子质量 .方法 :利用反应温度为 14 0℃ ,反应时间为 1~ 4h和反应温度为 30℃ ,反应时间为 7d这两种不同方法 ,制备不同 -NH2 质量分数和不同重均相对分子质量的精细壳聚糖制品 ,用酸碱滴定法测定壳聚糖 -NH2 质量分数 ,用激光散射仪测定壳聚糖的重均相对分子质量 .结果 :所制得壳聚糖的 -NH2 质量分数分别为 :6 1%、74 %、82 %、86 %、99% ,对应的重均相对分子质量分别为 :8 0 4× 10 6 、7 5 8× 10 6 、8 6 0× 10 6 、5 91× 10 6 、3 2 2×10 6 .利用室温、反应时间为 7d的制备方法所得的壳聚糖 -NH2 质量分数较高且重均相对分子质量大 .结论 :反应温度为 14 0℃、反应时间为 1~ 4h可获得 -NH2 质量分数高而重均相对分子质量小的壳聚糖制品 ;反应温度为 30℃、反应时间为 7d可获得 -NH2 质量分数较高而重均相对分子质量大的壳聚糖制品 。 展开更多
关键词 制备 壳聚糖 氨基质量分数 重均相对分子质量 激光散射仪 含量测定
下载PDF
地下洞室群对地面运动影响问题的级数解答——P波入射 被引量:23
19
作者 梁建文 张浩 Vincent W Lee 《地震学报》 CSCD 北大核心 2004年第3期269-280,共12页
采用波函数展开法 ,给出了平面P波入射下半空间中洞室群对地面运动影响问题的一个级数解答 .数值结果表明 ,地下洞室群对附近地面运动具有显著的放大作用 .建议地铁等地下工程在规划和设计时 ,考虑工程建设后对沿线地面运动的影响 .
关键词 地下洞室群 地面运动 平面P波 散射 级数解答
下载PDF
平面P波入射下地下洞室群动应力集中问题解析解 被引量:34
20
作者 梁建文 张浩 Vincent WLEE 《岩土工程学报》 EI CAS CSCD 北大核心 2004年第6期815-819,共5页
采用波函数展开法给出了半空间中洞室群在平面P波入射下动应力集中问题的一个解析解,数值结果表明,当洞室之间距离较近时,洞室之间的相互作用对地下洞室群的动应力集中具有显著的放大作用,动应力集中系数可能达到单个洞室的3.5倍以上,... 采用波函数展开法给出了半空间中洞室群在平面P波入射下动应力集中问题的一个解析解,数值结果表明,当洞室之间距离较近时,洞室之间的相互作用对地下洞室群的动应力集中具有显著的放大作用,动应力集中系数可能达到单个洞室的3.5倍以上,动应力集中系数峰值位于两个洞室相对的区域。 展开更多
关键词 动应力集中 解析解 展开法 波函数 系数 平面 半空间 地下洞室群 P波 峰值
下载PDF
上一页 1 2 6 下一页 到第
使用帮助 返回顶部