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Steering the energy sharing of electrons in nonsequential double ionization with orthogonally polarized two-color field
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作者 樊光琦 杨志杰 +4 位作者 孙烽豪 郑金梅 韩云天 黄明谦 刘情操 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第8期248-252,共5页
Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)la... Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)laser field is theoretically studied.And the dynamics in two typical collision pathways,recollision-impact-ionization(RII)and recollisionexcitation with subsequent ionization(RESI),is systematically explored.Our results reveal that the V-shaped structure in the correlated momentum distribution is mainly caused by the RII mechanism when the relative amplitude of the OTC laser field is zero,and the first ionized electrons will quickly skim through the nucleus and share few energy with the second electron.As the relative amplitude increases,the V-shaped structure gradually disappears and electrons are concentrated on the diagonal in the electron correlation spectrum,indicating that the energy sharing after electrons collision is symmetric for OTC laser fields with large relative amplitudes.Our studies show that changing the relative amplitude of the OTC laser field can efficiently control the electron–electron collisions and energy exchange efficiency in the NSDI process. 展开更多
关键词 nonsequential double ionization correlated electron–electron momentum distribution energy sharing of electrons orthogonally polarized two-color field laser field semiclassical ensemble models
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Controlling the contributions to high-order harmonic generation from different nuclei of N_2 with an orthogonally polarized two-color laser field 被引量:3
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作者 杜慧 潘雪飞 +4 位作者 刘海凤 张宏丹 张军 郭静 刘学深 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第9期303-309,共7页
The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model.We show that the control of ... The generation of high-order harmonic and the attosecond pulse of the N2 molecule with an orthogonally polarized two-color laser field are investigated by the strong-field Lewenstein model.We show that the control of contributions to high-order harmonic generation(HHG) from different nuclei is realized by properly selecting the relative phase.When the relative phase is chosen to be φ= 0.4π,the contribution to HHG from one nucleus is much more than that from another.Interference between two nuclei can be suppressed greatly; a supercontinuum spectrum of HHG appears from 40 e V to125 e V.The underlying physical mechanism is well explained by the time–frequency analysis and the semi-classical threestep model with a finite initial transverse velocity.By superposing several orders of harmonics,an isolated attosecond pulse with a duration of 80 as can be generated. 展开更多
关键词 high-order harmonic generation orthogonally polarized two-color laser field attosecond pulse
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External-cavity birefringence feedback effects of microchip Nd:YAG laser and its application in angle measurement 被引量:2
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作者 任成 谈宜东 张书练 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第8期3438-3443,共6页
External-cavity birefringence feedback effects of the microchip Nd:YAG laser are presented. When a birefringence element is placed in the external feedback cavity of the laser, two orthogonally polarized laser beams ... External-cavity birefringence feedback effects of the microchip Nd:YAG laser are presented. When a birefringence element is placed in the external feedback cavity of the laser, two orthogonally polarized laser beams with a phase difference are output. The phase difference is twice as large as the phase retardation in the external cavity along the two orthogonal directions. The variable extra-cavity birefringence, caused by rotation of the external-cavity birefringenee element, results in tunable phase difference between the two orthogonally polarized beams. This means that the roll angle information has been translated to phase difference of two output laser beams. A theoretical analysis based on the Fabry-Perot cavity equivalent model and refractive index ellipsoid is presented, which is in good agreement with the experimental results. This phenomenon has potential applications for roll angle measurement. 展开更多
关键词 microchip laser external-cavity birefringence feedback orthogonally polarized lasers angle measurement
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Fuzzy Stability of the Orthogonal Cauchy Functional equations
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作者 BI Lv-qing DAI Song-song HU BO 《Chinese Quarterly Journal of Mathematics》 2018年第3期302-312,共11页
In this paper, we establish fuzzy stability of the orthogonal Cauchy functional equations f(x + y) = f(x) + f(y), x ⊥ y and the orthogonal Cauchy functional of P exider type f(x + y) = g(x) + h(y), x ⊥ y in which ⊥... In this paper, we establish fuzzy stability of the orthogonal Cauchy functional equations f(x + y) = f(x) + f(y), x ⊥ y and the orthogonal Cauchy functional of P exider type f(x + y) = g(x) + h(y), x ⊥ y in which ⊥ is the orthogonality in the sense of Rtz. 展开更多
关键词 FUZZY NORMED SPACE Hyers-Ulam STABILITY orthogonally CAUCHY functionalequation orthogonally CAUCHY functional Pexider equation orthogonALITY SPACE
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Flow of micropolar fluid between two orthogonally moving porous disks 被引量:1
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作者 司新辉 郑连存 +1 位作者 张欣欣 司新毅 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2012年第8期963-974,共12页
The unsteady, laminar, incompressible, and two-dimensional flow of a mi- cropolar fluid between two orthogonally moving porous coaxial disks is considered. The extension of von Karman's similarity transformations is ... The unsteady, laminar, incompressible, and two-dimensional flow of a mi- cropolar fluid between two orthogonally moving porous coaxial disks is considered. The extension of von Karman's similarity transformations is used to reduce the governing partial differential equations (PDEs) to a set of non-linear coupled ordinary differential equations (ODEs) in the dimensionless form. The analytical solutions are obtained by employing the homotopy analysis method (HAM). The effects of various physical param- eters such as the expansion ratio and the permeability Reynolds number on the velocity fields are discussed in detail. 展开更多
关键词 homotopy analysis method (HAM) expansion ratio orthogonally movingporous disk
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Orthogonality and Quintic Functional Equations 被引量:1
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作者 Choonkil PARK Jian Lian CUI Madjid Eshaghi GORDJI 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2013年第7期1381-1390,共10页
Using the fixed point method, we prove the Hyers Ulam stability of an orthogonally quintic functional equation in Banach spaces and in non-Archimedean Banach spaces.
关键词 Hyers-Ulam stability orthogonally quintic functional equation fixed point orthogonalityspace non^Archimedean Banach space
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A novel orthogonally linearly polarized Nd:YVO_4 laser
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作者 闫兴鹏 柳强 +3 位作者 陈海龙 付星 巩马理 王东生 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第8期395-400,共6页
We presented a novel orthogonally linearly polarized Nd:YVO4 laser. Two pieces of a-cut grown-together composite YVO4/Nd:YVO4 crystals were placed in the resonant cavity with the c-axis of the two crystals orthogona... We presented a novel orthogonally linearly polarized Nd:YVO4 laser. Two pieces of a-cut grown-together composite YVO4/Nd:YVO4 crystals were placed in the resonant cavity with the c-axis of the two crystals orthogonally. The polarization and power performance of the orthogonally polarized laser were investigated. A 26.2-W orthogonally linearly polarized laser was obtained. The power ratio between the two orthogonally polarized lasers was varied with the pump power caused by the polarized mode coupling. The longitudinal modes competition and the corresponding variable optical beats were also observed from the orthogonally polarized laser. We also adjusted the crystals with their c-axis parallele to each other, and a 40.7-W linearly polarized TEM00 laser was obtained, and the beam quality factors were Mx^2 = 1.37 and My^2 = 1.25. 展开更多
关键词 orthogonally linearly polarized laser composite Nd:YVO4 optical beat frequency
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A General Model for Analysis of Sound Radiation from Orthogonally Stiffened Laminated Composite Plates
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作者 金叶青 庞福振 +1 位作者 杨飞 李光明 《China Ocean Engineering》 SCIE EI CSCD 2014年第4期457-470,共14页
A general theoretical model is developed to investigate the sound radiation from an infinite orthogonally stiffened plate under point excitation force. The plate can be metallic or composite, and fluid loading is also... A general theoretical model is developed to investigate the sound radiation from an infinite orthogonally stiffened plate under point excitation force. The plate can be metallic or composite, and fluid loading is also considered in the research. The first order shear deformation theory is used to account for the transverse shear deformation. The motion of the equally spaced stiffeners is examined by considering their bending vibrations and torsional movements. Based on the periodic structure theory and the concepts of the equivalent dynamic flexibility of the plate, the generalized vibro-acoustic equation of the model is obtained by applying the Fourier transform method. The generalized model that can be solved numerically is validated by comparing model predictions with the existing results. Numerical calculations are performed to investigate the effects of the location of the excitation, the spacing of the stiffeners, the plate thickness, the strengthening form and the fiber orientation on the sound radiation characteristic of the orthogonaUy stiffened plate, and some practical conclusions are drawn from these parameter studies. 展开更多
关键词 sound radiation orthogonally stiffened plates first order shear deformation theory wavenumber analysis equivalent dynamic flexibility
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Generation of non-integer high-order harmonics and significant enhancement of harmonic intensity 被引量:1
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作者 Chang-Long Xia Yue-Yue Lan Xiang-Yang Miao 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第4期221-225,共5页
High-order harmonics from helium atom in the orthogonally two-color(OTC) laser field are investigated by solving the two-dimensional time-dependent Schrodinger equation.Non-integer high-order harmonics are obtained in... High-order harmonics from helium atom in the orthogonally two-color(OTC) laser field are investigated by solving the two-dimensional time-dependent Schrodinger equation.Non-integer high-order harmonics are obtained in some ratio of frequencies of two components.Pure odd and even harmonics from atoms could be separated in two components by adjusting the ratio of frequencies in OTC scheme,and the resolution of harmonics is improved at the same time.The physical mechanism is explained by the periodicity of dipole.With the same intensity of the incident laser,the intensity of the high-order harmonics from the OTC field scheme is improved by three orders of magnitude compared to the monochromatic laser field scheme.A theoretical scheme is provided for experimentally achieving improving energy resolution and separation of pure odd and even harmonics in atoms.Also,we provide a means for improving harmonic intensity. 展开更多
关键词 non-integer high-order harmonic generation the orthogonally two-color laser field the enhancement of harmonic intensity
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A Stable Wavelength Operation Ho:YAG Laser with Orthogonally Polarized Pump 被引量:1
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作者 Jing-Liang Liu Xin-Yu Chen +2 位作者 Rui-Ming Wang Chun-Ting Wu Guang-Yong Jin 《Chinese Physics Letters》 SCIE CAS CSCD 2019年第2期12-14,共3页
A stable wavelength operation Ho:YAG laser dual-pumped by two orthogonally polarized Tm:YLF lasers is reported. Under the cw operation mode, a laser output power of 24 W is measured. The corresponding opticaloptical c... A stable wavelength operation Ho:YAG laser dual-pumped by two orthogonally polarized Tm:YLF lasers is reported. Under the cw operation mode, a laser output power of 24 W is measured. The corresponding opticaloptical conversion efficiency is 44.75% and the slope efficiency is 50.12%. Under the Q-switched operation mode,the output maximum average power is 22.8 W at the re-frequency of 6 kHz. The corresponding optical-optical conversion efficiency and slope efficiency are 42.64% and 48.01%, respectively. The output central wavelength is 2090.73 nm, the linewidth is 0.40 nm, and the beam quality is M^2< 1.6. Moreover, the shift of the output central wavelength is less than 0.01 nm, and the linewidth shift is also less than 0.01 nm. 展开更多
关键词 YAG length Ho A STABLE WAVELENGTH Operation HO:YAG LASER with orthogonally POLARIZED PUMP
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Controlling nonadiabatic spectral redshift of high-order harmonic using two orthogonally polarized laser fields
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作者 Hongmei Wu Shengjun Yue +3 位作者 Jinbin Li Silin Fu Bitao Hu Hongchuan Du 《Chinese Optics Letters》 SCIE EI CAS CSCD 2018年第4期11-15,共5页
We investigate the nonadiabatic spectral redshift of high-order harmonic of He driven by two time-delayed orthogonally polarized laser fields. It is found that the nonadiabatic spectral redshift can be observed by pro... We investigate the nonadiabatic spectral redshift of high-order harmonic of He driven by two time-delayed orthogonally polarized laser fields. It is found that the nonadiabatic spectral redshift can be observed by properly adjusting the time delay of the two laser fields when the controlling pulse is added in the raising part of the driving pulse in the vertical direction. That is because the controlling pulse in the vertical direction prevents the ionized electrons from returning to the vicinity of parent ions and then reduces the recombination probability. This leads to the high-order harmonic generated mainly in the falling part of the driving pulse. Meanwhile,we also find that the quantity of redshift can be effectively controlled through accommodating the positive time delays. In addition, this scheme can also be used to produce nonadiabatic spectral blueshift. 展开更多
关键词 Controlling nonadiabatic spectral redshift of high-order harmonic using two orthogonally polarized laser fields
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Ultrafast photoionization of ions and molecules by orthogonally polarized intense laser pulses: Effects of the time delay
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作者 Si-Qi Zhang Zhi-Jie Yang +5 位作者 Zhi-Xian Lei Wei Feng Sheng-Peng Zhou Kai-Jun Yuan Xue-Shen Liu Jing Guo 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第1期207-214,共8页
We present the photoelectron momentum distributions(PMDs) and the photoelectron angular distributions(PADs) of He+ ions, aligned H2+ molecules and N2 molecules by intense orthogonally polarized laser pulses. Simulatio... We present the photoelectron momentum distributions(PMDs) and the photoelectron angular distributions(PADs) of He+ ions, aligned H2+ molecules and N2 molecules by intense orthogonally polarized laser pulses. Simulations are performed by numerically solving the corresponding two-dimensional time-dependent Schr?dinger equations(TDSEs) within the single-electron approximation frame. Photoelectron momentum distributions and photoelectron angular distributions present different patterns with the time delays Td, illustrating the dependences of the PMDs and PADs on the time delays by orthogonally polarized laser pulses. The evolution of the electron wavepackets can be employed to describe the intensity of the PADs from the TDSE simulations for N2 molecules. 展开更多
关键词 photoelectron momentum distributions photoelectron angular distributions intense orthogonally polarized laser pulses ultrafast photoionization model
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Security enhancement for double-random phase encryption using orthogonally encoded image and electronically synthesized key data
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作者 In-Ho Lee Myungjin Cho 《Chinese Optics Letters》 SCIE EI CAS CSCD 2015年第1期22-26,共5页
We prot)ose a security-enhanced double-random phase encryption (DRPE) scheme using orthogonally encoded image and electronically synthesized key data to cope with the security problem of DRPE technique caused by fi... We prot)ose a security-enhanced double-random phase encryption (DRPE) scheme using orthogonally encoded image and electronically synthesized key data to cope with the security problem of DRPE technique caused by fixed double-random phase masks for eneryption. In the proposed scheme, we adopt the electronically synthesized key to frequently update the phase mask using a spatial light modulator, and also employ the orthogonal encoding technique to encode the image and electronically synthesized key data, which can enhance the security of both data. We provide detailed procedures for eneryption and decryption of the proposed scheme, and provide the simulation results to show the eneryption effects of the proposed scheme. 展开更多
关键词 DATA Security enhancement for double-random phase encryption using orthogonally encoded image and electronically synthesized key data
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Cavity tuning characteristics of orthogonally polarized dual-frequency He-Ne laser at 1.15 μm
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作者 赵正启 张书练 +1 位作者 谈宜东 李岩 《Chinese Optics Letters》 SCIE EI CAS CSCD 2012年第2期48-51,共4页
The cavity tuning characteristics of orthogonally polarized dual-frequency HeiNe laser at 1.15 μm are presented. Vectorial-extension model based on semi-classical laser theory reveals that cavity tuning characteristi... The cavity tuning characteristics of orthogonally polarized dual-frequency HeiNe laser at 1.15 μm are presented. Vectorial-extension model based on semi-classical laser theory reveals that cavity tuning characteristics are related to beat frequency, relative excitation, and type of Ne isotope. Distortions of cavity tuning curves become moderate with the increase of beat frequency because of the weakening of the cross- saturation effect. Distortions are enhanced with the increase of relative excitation because of the combined action of the self-saturation and cross-saturation effects. By adopting dual-isotope Ne instead of monoisotoplie Ne, distortions are reduced because of the misalignment between peaks of the self-saturation and net gain coefficients. The theoretical calculations are in good agreement with the corresponding experimental results. 展开更多
关键词 Cavity tuning characteristics of orthogonally polarized dual-frequency He-Ne laser at 1.15
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Efficient semi-analytical methods for the vibration response of and acoustic radiation from a periodical orthogonally rib-stiffened plate
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作者 ZHOU Haian WANG Xiaoming +2 位作者 WU Huayong MENG Jianbing LI Lijun 《Chinese Journal of Acoustics》 CSCD 2019年第3期309-330,共22页
In order to theoretically predict and analyze the vibration response and acoustic radiation characteristics of a periodical orthogonally rib-stiffened plate,its vibro-acoustic equations of an underwater infinite model... In order to theoretically predict and analyze the vibration response and acoustic radiation characteristics of a periodical orthogonally rib-stiffened plate,its vibro-acoustic equations of an underwater infinite model are established.The rib-stiffened plate is stimulated by a harmonic plane pressure.By using the Fourier transforms,Poisson’s summation formula and space harmonic method,the structural vibration response and acoustic radiation pressure are expressed as functions of displacement harmonic components.Efficient semi-analytical methods are proposed in this work,and then approximate solutions for finite terms of the harmonic components are obtained by employing the truncation technique.Effects of the vibration response,rib spacing and torsional moment of the ribs on the radiation pressure are examined,and the validity of the present methods is also verified.Theoretical results show that the torsional moment of the ribs affects the modal frequencies of the stiffened plate,which should not be neglected in engineering applications with high precision requirement.With attachment of the ribs to the thin plate,its far field radiation pressure can be reduced in the low frequency range by adjusting rib spacing and cross sectional size of the ribs. 展开更多
关键词 EFFICIENT SEMI-ANALYTICAL methods for the vibration response of and acoustic RADIATION from a PERIODICAL orthogonally rib-stiffened PLATE
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极大纠缠态的LOCC可靠区分
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作者 曹怀信 李欢 《安康学院学报》 2014年第4期95-97,113,共4页
在阐述LOCC测量和LOCC可靠区分定义的基础上,分析了极大纠缠态的有关性质,研究了复合系统中相互正交的极大纠缠态LOCC可靠区分的条件以及中相互正交的极大纠缠态LOCC可靠区分与其酉算子之间的关系,得出结论:在中,总存在个相互正交的极... 在阐述LOCC测量和LOCC可靠区分定义的基础上,分析了极大纠缠态的有关性质,研究了复合系统中相互正交的极大纠缠态LOCC可靠区分的条件以及中相互正交的极大纠缠态LOCC可靠区分与其酉算子之间的关系,得出结论:在中,总存在个相互正交的极大纠缠态是LOCC可靠区分的。 展开更多
关键词 LOCC测量 LOCC可靠区分 正交性 极大纠缠态
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酚酸类物质的抑草效应分析 被引量:40
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作者 何华勤 梁义元 +4 位作者 贾小丽 宋碧清 郭玉春 梁康迳 林文雄 《应用生态学报》 CAS CSCD 2004年第12期2342-2346,共5页
运用正交旋转回归试验设计分析 5种常见的化感物质替代物水杨酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸对田间伴生杂草稗草的抑制效应 .结果表明 ,肉桂酸对稗草根长抑制率的影响最显著 ,其关系函数的二次项系数为 - 6 18,达极显著水... 运用正交旋转回归试验设计分析 5种常见的化感物质替代物水杨酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸对田间伴生杂草稗草的抑制效应 .结果表明 ,肉桂酸对稗草根长抑制率的影响最显著 ,其关系函数的二次项系数为 - 6 18,达极显著水平 .水杨酸、对羟基苯甲酸和阿魏酸对稗草根长的抑制效应趋势与肉桂酸相同 ,效应曲线均为“∩”形抛物线 ;而香草酸的效应曲线则为“∪”形抛物线 .当水杨酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸浓度水平分别为 0 0 6、0 6 0、0 2 4、0 0 2和 0 0 2mmol·L-1时 ,混合物对稗草根长的抑制率最大 ,达到 78 6 5 % . 展开更多
关键词 化感物质 酚酸 抑草效应 正交旋转回归设计
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南瓜多糖超声提取工艺的优化 被引量:26
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作者 孙俊 邓红 仇农学 《西北农业学报》 CAS CSCD 北大核心 2007年第2期198-202,共5页
试验优选了超声波提取南瓜多糖的最佳提取条件。采用三因素二次回归旋转组合试验设计,以液料比(X1)、提取时间(X2)、提取温度(X3)为考察因素,借助紫外分光光度法测定提取液中南瓜多糖的含量,并最终确定了提取的最佳条件。结果表明,影响... 试验优选了超声波提取南瓜多糖的最佳提取条件。采用三因素二次回归旋转组合试验设计,以液料比(X1)、提取时间(X2)、提取温度(X3)为考察因素,借助紫外分光光度法测定提取液中南瓜多糖的含量,并最终确定了提取的最佳条件。结果表明,影响超声波提取南瓜多糖的因素主次关系为液料比>提取温度>提取时间;最佳工艺条件为提取时间30 min,提取温度50℃,液料比1∶52。通过DPS分析软件所建立的数学模型Y=0.68701+0.16744X1+0.05313X2+0.08872X3-0.08485X12-0.085021X22-0.08768X32+0.03987X1X3与试验吻合。在上述最佳提取条件下,粗多糖的得率为6.45%,优化工艺较稳定,提取率也较高。 展开更多
关键词 二次回归旋转组合设计 超声波 南瓜多糖 提取
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地铁隧道正交穿越地裂缝的相互作用机制试验研究 被引量:19
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作者 李凯玲 门玉明 +1 位作者 严静平 李寻昌 《岩石力学与工程学报》 EI CAS CSCD 北大核心 2011年第3期556-563,共8页
以西安地铁隧道为工程背景,利用地铁隧道正交穿越地裂缝应力模型试验,分析在地裂缝活动环境下的地铁隧道与地裂缝的相互作用关系。在地裂缝上、下盘发生相对错动时,对模型结构的纵向应变、结构底部的相对位移以及结构外围土压力等进行... 以西安地铁隧道为工程背景,利用地铁隧道正交穿越地裂缝应力模型试验,分析在地裂缝活动环境下的地铁隧道与地裂缝的相互作用关系。在地裂缝上、下盘发生相对错动时,对模型结构的纵向应变、结构底部的相对位移以及结构外围土压力等进行监测。数据分析结果表明:地铁隧道穿越地裂缝时其荷载传递机制涉及结构的刚度效应、下卧土体的支承作用、隧道与土体之间的摩阻作用以及裂缝处上下盘的接触效应4个方面。根据隧道结构变形特征及应变变化规律,构建隧道与土体底部脱空状态下相互作用力学模型,为西安地铁穿越地裂缝的隧道结构设计提供参考。通过对不同断面隧道的应变及变形比较分析,提出地铁隧道正交穿越地裂缝带时宜采用马蹄形隧道断面,以提高结构的整体刚度;加强位于地裂缝下盘的隧道混凝土的裂缝控制,做好防水处理。 展开更多
关键词 隧道工程 相互作用 地裂缝 模型试验 正交穿越
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我国大陆干旱指数及其年际变化 被引量:18
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作者 江剑民 《大气科学》 CSCD 北大核心 1991年第1期43-52,共10页
本文应用正交旋转主分量分析方法,计算分析了我国大陆1952—1987年间大气干旱指数s=ΔT/σ_T-ΔR/σ_R的地域相关和年际变化特征。结果表明,可以将我国大陆上旱涝异常的变化大致按43°N和30°N为分界线划分成三个基本相关的纬带... 本文应用正交旋转主分量分析方法,计算分析了我国大陆1952—1987年间大气干旱指数s=ΔT/σ_T-ΔR/σ_R的地域相关和年际变化特征。结果表明,可以将我国大陆上旱涝异常的变化大致按43°N和30°N为分界线划分成三个基本相关的纬带。1954—1957年间和1963、1969年前后大部分地区相对湿润多雨。70年代以来,长江以北相对少雨干旱,气候变化的大趋势与撒亥勒(Sahel),以及英格兰中部和威尔士等地区相类似。年度干旱指数年际变化的短周期大部分地区以2—3年为主,具有准两年振荡的特点。 展开更多
关键词 中国 大陆 干旱 指数 年际变化
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