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Symplectic partitioned Runge-Kutta method based onthe eighth-order nearly analytic discrete operator and its wavefield simulations 被引量:3
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作者 张朝元 马啸 +1 位作者 杨磊 宋国杰 《Applied Geophysics》 SCIE CSCD 2014年第1期89-106,117,118,共20页
We propose a symplectic partitioned Runge-Kutta (SPRK) method with eighth-order spatial accuracy based on the extended Hamiltonian system of the acoustic waveequation. Known as the eighth-order NSPRK method, this te... We propose a symplectic partitioned Runge-Kutta (SPRK) method with eighth-order spatial accuracy based on the extended Hamiltonian system of the acoustic waveequation. Known as the eighth-order NSPRK method, this technique uses an eighth-orderaccurate nearly analytic discrete (NAD) operator to discretize high-order spatial differentialoperators and employs a second-order SPRK method to discretize temporal derivatives.The stability criteria and numerical dispersion relations of the eighth-order NSPRK methodare given by a semi-analytical method and are tested by numerical experiments. We alsoshow the differences of the numerical dispersions between the eighth-order NSPRK methodand conventional numerical methods such as the fourth-order NSPRK method, the eighth-order Lax-Wendroff correction (LWC) method and the eighth-order staggered-grid (SG)method. The result shows that the ability of the eighth-order NSPRK method to suppress thenumerical dispersion is obviously superior to that of the conventional numerical methods. Inthe same computational environment, to eliminate visible numerical dispersions, the eighth-order NSPRK is approximately 2.5 times faster than the fourth-order NSPRK and 3.4 timesfaster than the fourth-order SPRK, and the memory requirement is only approximately47.17% of the fourth-order NSPRK method and 49.41% of the fourth-order SPRK method,which indicates the highest computational efficiency. Modeling examples for the two-layermodels such as the heterogeneous and Marmousi models show that the wavefields generatedby the eighth-order NSPRK method are very clear with no visible numerical dispersion.These numerical experiments illustrate that the eighth-order NSPRK method can effectivelysuppress numerical dispersion when coarse grids are adopted. Therefore, this methodcan greatly decrease computer memory requirement and accelerate the forward modelingproductivity. In general, the eighth-order NSPRK method has tremendous potential value forseismic exploration and seismology research. 展开更多
关键词 SYMPLECTIC partitioned RUNGE-KUTTA method nearly ANALYTIC DISCRETE OPERATOR Numerical dispersion Wavefield simulation
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具有处处非零Killing向量场的nearly Khler流形 被引量:1
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作者 张留伟 李兴校 贾志刚 《河南师范大学学报(自然科学版)》 CAS CSCD 北大核心 2010年第4期33-35,共3页
研究了在nearly Khler流形上某种处处非零Killing向量场的存在性与流形的拓扑和几何之间的联系.并且得到了下面的主要结论及其推论:设(M2n,g,J)是一个2n维的近复流形.如果在M上存在一个处处非零的Killing向量场ξ,使得ξ*∧Jξ*是闭2... 研究了在nearly Khler流形上某种处处非零Killing向量场的存在性与流形的拓扑和几何之间的联系.并且得到了下面的主要结论及其推论:设(M2n,g,J)是一个2n维的近复流形.如果在M上存在一个处处非零的Killing向量场ξ,使得ξ*∧Jξ*是闭2次形式,则M局部微分同胚于M1×M2,其中M1和M2分别是分布V∶=span{ξ,Jξ}和分布H:=span{ξ,Jξ}⊥的极大积分子流形. 展开更多
关键词 nearly Khler流形 KILLING向量场 闭2次形式
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nearly和almost的语料研究 被引量:3
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作者 王庆新 刘欣 《山东外语教学》 2002年第6期75-77,共3页
语言的研究越来越强调语料的真实性和客观性.计算机空前迅速地发展,使得包含广泛自然语料的语料库的建立成为可能,这种语料库同时也为语言研究提供了可靠依据.本文对nearly和almost的研究,就是根据英国兰卡斯特大学的Spoken English语... 语言的研究越来越强调语料的真实性和客观性.计算机空前迅速地发展,使得包含广泛自然语料的语料库的建立成为可能,这种语料库同时也为语言研究提供了可靠依据.本文对nearly和almost的研究,就是根据英国兰卡斯特大学的Spoken English语料库的语料进行的.这一研究,对nearly和almost在自然语言中的应用提供了一个真实客观的依据. 展开更多
关键词 nearly ALMOST 语料库语言学 语料研究 语义 英语
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Nearly Sasak流形的半不变子流形的测地性 被引量:1
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作者 万勇 《长沙电力学院学报(自然科学版)》 2004年第1期1-3,共3页
给出了NearlySasak流形的半不变子流形测地的几个充要条件.
关键词 nearly Sasak流形 半不变子流形 测地性 张量结构
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Nearly Sasak流形上分布D{ξ}的可积性
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作者 万勇 《长沙理工大学学报(自然科学版)》 CAS 2007年第2期72-74,共3页
给出了Nearly Sasak流形上分布D{ξ}可积的几个充要条件,推广了Bejancu的结论.
关键词 nearly Sasak流形 半不变子流形 分布 联络 可积
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SOME METRIC AND TOPOLOGICAL PROPERTIES OF NEARLY STRONGLY AND NEARLY VERY CONVEX SPACES
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作者 Zihou ZHANG Vicente MONTESINOS Chunyan LIU 《Acta Mathematica Scientia》 SCIE CSCD 2020年第2期369-378,共10页
We obtain characterizations of nearly strong convexity and nearly very convexity by using the dual concept of S and WS points,related to the so-called Rolewicz’s property(α).We give a characterization of those point... We obtain characterizations of nearly strong convexity and nearly very convexity by using the dual concept of S and WS points,related to the so-called Rolewicz’s property(α).We give a characterization of those points in terms of continuity properties of the identity mapping.The connection between these two geometric properties is established,and finally an application to approximative compactness is given. 展开更多
关键词 Banach spaces nearly strongly convex spaces nearly very convex spaces Kadec property Radon-Riesz property approximative compactness
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almost与nearly有何区别?
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作者 杜淑萍 《英语知识》 2012年第3期46-46,共1页
【问】[518]在学习中经常会遇到almost与nearly这两个非常活跃的副词,它们都能表示“几乎,差不多”,请问它们之间有何异同点?
关键词 nearly ALMOST 学习
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SUPER EFFICIENCY IN THE NEARLY CONE-SUBCONVEXLIKE VECTOR OPTIMIZATION WITH SET-VALUED FUNCTIONS 被引量:14
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作者 徐义红 刘三阳 《Acta Mathematica Scientia》 SCIE CSCD 2005年第1期152-160,共9页
Some properties for convex cones are discussed, which are used to obtain an equivalent condition and another important property for nearly cone-subconvexlike set-valued functions. Under the nearly cone-subconvexlikene... Some properties for convex cones are discussed, which are used to obtain an equivalent condition and another important property for nearly cone-subconvexlike set-valued functions. Under the nearly cone-subconvexlikeness, some characterizations of the super efficiency are given in terms of scalarization and Lagrangian multipliers. Related results are generalized. 展开更多
关键词 nearly cone-subconvexlikeness convex cones super efficiency SCALARIZATION Lagrangian multipliers
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BENSON PROPER EFFICIENCY IN THE NEARLY CONE-SUBCONVEXLIKE VECTOR OPTIMIZATION WITH SET-VALUED FUNCTIONS 被引量:16
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作者 XuYihong LiuSanyang 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2003年第1期95-102,共8页
Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearl... Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearly cone-subconvexlikeness,a Lagrangian multiplier theorem on Benson proper efficiency is presented. Related results are generalized. 展开更多
关键词 nearly cone-subconvexlikeness convex cones Benson proper efficiency Lagrangian multiplier theorem.
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Nearly Free Electron State in Graphane Nanoribbon Superlattice
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作者 刘巧鸿 李震宇 杨金龙 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2011年第1期22-24,I0003,共4页
Nearly free electron (NFE) state has been widely studied in low dimensional systems. Based on first-principles calculations, we identify two types of NFE states in graphane nanoribbon superlattice, similar to those ... Nearly free electron (NFE) state has been widely studied in low dimensional systems. Based on first-principles calculations, we identify two types of NFE states in graphane nanoribbon superlattice, similar to those of graphene nanoribbons and boron nitride nanoribbons. Effect of electron doping on the NFE states in graphane nanoribbon superlattice has been studied, and it is possible to open a vacuum transport channel via electron doping. 展开更多
关键词 GRAPHANE nearly free electron Electronic structure
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Estimation for nearly unit root processes with GARCH errors 被引量:4
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作者 YUAN Yu-ze ZHANG Rong-mao Department of Mathematics, Zhejiang University, Hangzhou 310027, China 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2010年第3期297-306,共10页
In this paper the limiting distribution of the least square estimate for the autoregressive coefficient of a nearly unit root model with GARCH errors is derived. Since the limiting distribution depends on the unknown ... In this paper the limiting distribution of the least square estimate for the autoregressive coefficient of a nearly unit root model with GARCH errors is derived. Since the limiting distribution depends on the unknown variance of the errors, an empirical likelihood ratio statistic is proposed from which confidence intervals can be constructed for the nearly unit root model without knowing the variance. To gain an intuitive sense for the empirical likelihood ratio, a small simulation for the asymptotic distribution is given. 展开更多
关键词 nearly unit root GARCH error least square estimation Ornstein-Uhlenbeck process empirical likelihood.
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Vibration analysis and active control of nearly periodic two-span beams with piezoelectric actuator/sensor pairs 被引量:2
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作者 Fengming LI Zhiguang SONG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2015年第3期279-292,共14页
The piezoelectric materials are used to investigate the active vibration control of ordered/disordered periodic two-span beams. The equation of motion of each sub-beam with piezoelectric patches is established based o... The piezoelectric materials are used to investigate the active vibration control of ordered/disordered periodic two-span beams. The equation of motion of each sub-beam with piezoelectric patches is established based on Hamilton's principle with an assumed mode method. The velocity feedback control algorithm is used to design the controller. The free and forced vibration behaviors of the two-span beams with the piezoelectric actuators and sensors are analyzed. The vibration properties of the disordered two-span beams caused by misplacing the middle support are also researched. In addition, the effects of the length disorder degree on the vibration performances of the disordered beams are investigated. From the numerical results, it can be concluded that the disorder in the length of the periodic two-span beams will cause vibration localizations of the free and forced vibrations of the structure, and the vibration localization phenomenon will be more and more obvious when the length difference between the two sub-beams increases. Moreover, when the velocity feedback control is used, both the forced and the free vibrations will be suppressed. Meanwhile, the vibration behaviors of the two-span beam are tuned. 展开更多
关键词 nearly periodic beam vibration localization active vibration control piezoelectric material
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Signed total domination in nearly regular graphs 被引量:2
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作者 康丽英 单而芳 《Journal of Shanghai University(English Edition)》 CAS 2006年第1期4-8,共5页
A function f: V( G)→{1,1} defined on the vertices of a graph G is a signed total dominating function (STDF) if the sum of its function values over any open neighborhood is at least one. An STDF f is minimal if t... A function f: V( G)→{1,1} defined on the vertices of a graph G is a signed total dominating function (STDF) if the sum of its function values over any open neighborhood is at least one. An STDF f is minimal if there does not extst a STDF g: V(G)→{-1,1}, f≠g, for which g ( v )≤f( v ) for every v∈V( G ). The weight of a STDF is the sum of its function values over all vertices. The signed total domination number of G is the minimum weight of a STDF of G, while the upper signed domination number of G is the maximum weight of a minimal STDF of G, In this paper, we present sharp upper bounds on the upper signed total domination number of a nearly regular graph. 展开更多
关键词 signed total domination nearly regular graph bounds.
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Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil 被引量:1
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作者 李保忠 蔡袁强 《Journal of Zhejiang University Science》 EI CSCD 2003年第6期694-701,共8页
Biot' s two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturat... Biot' s two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasitransverse wave (QSV) and the anti-plane transverse wave (SH) . Numerical results are given to illustrate theinfluence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering. 展开更多
关键词 SATURATION Transversely isotropic nearly saturated DISPERSION ATTENUATION
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Initial Rifting Age of the Nearly N–S Rifts in Southern Tibetan Plateau:New Evidence from the Age limit of the Early Sediments 被引量:2
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作者 HA Guanghao WU Zhonghai +1 位作者 HE Lin WANG Shubing 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2017年第2期739-740,共2页
Objective The nearly parallel N-S-trending rifts in southern Tibet represent the E-W extension of the Tibet Plateau. Most data which constrained the age of the extensional deformation come from isotopic dating of the... Objective The nearly parallel N-S-trending rifts in southern Tibet represent the E-W extension of the Tibet Plateau. Most data which constrained the age of the extensional deformation come from isotopic dating of the dikes probably related to the activity of the nearly N-S faulting and micas from hydrothermal activity and the low- temperature thermochronology of plateau uplift. Previous research shows that there are at least three different ideas about the age of the rifts: (1) older than 16-12 Ma, (2) 14- 10 Ma, and (3) 8-4 Ma (Fig. la). For the old sedimentary strata represented the beginning of the rifting, the dating of the sediments helps to better define the initial rifting age. 展开更多
关键词 Initial Rifting Age of the nearly N S Rifts in Southern Tibetan Plateau:New Evidence from the Age limit of the Early Sediments
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Nearly N-矩阵
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作者 侯素梅 《广东工业大学学报》 CAS 1999年第4期87-90,共4页
给出了nearly N- 矩阵的定义,并得到了nearly N- 矩阵的一些性质.
关键词 nearly N-矩阵 主子式 行列式 N-矩阵
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Unsplit-field higher-order nearly PML for arbitrary media in EM simulation 被引量:1
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作者 JIANG Haolin XIE Yongjun +2 位作者 WU Peiyu ZHANG Jianfeng NIU Liqiang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2021年第1期1-6,共6页
An unsplit-field higher order nearly perfectly matched layer(NPML)based on the auxiliary differential equation approach is introduced in three-dimensional finite-difference timedomain lattices.The proposed scheme has ... An unsplit-field higher order nearly perfectly matched layer(NPML)based on the auxiliary differential equation approach is introduced in three-dimensional finite-difference timedomain lattices.The proposed scheme has the advantage of both the NPML scheme and the higher order concept in terms of the improved absorbing performance and considerable computational efficiency.By incorporating with the generalized material independent concept,the proposed implementation is indepen dent of the material’s type.Thus,it has the advantages of terminating arbitrary media without changing the updated equations in the PML regions.Its effectiveness and efficiency is further demonstrated through numerical examples. 展开更多
关键词 finite-difference time-domain(FDTD) electromagnetic(EM)simulation nearly perfectly matched layer(NPML) higher order perfectly matched layer(HO-PML)
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Auxiliary transportation mode in a fully-mechanized face in a nearly horizontal thin coal seam 被引量:2
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作者 Wang Chen Tu Shihao +2 位作者 Zhang Lei Yang Qianlong Tu Hongsheng 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2015年第6期963-968,共6页
On fully-mechanized faces in nearly horizontal thin coal seams (NHTCS), the selection of the auxiliary transportation mode is difficult. Generally, auxiliary transportation mainly includes trackless or rail transpor... On fully-mechanized faces in nearly horizontal thin coal seams (NHTCS), the selection of the auxiliary transportation mode is difficult. Generally, auxiliary transportation mainly includes trackless or rail transportation. Combined with a familiar NHTCS fully-mechanized face, a multi-attribute decision- making model was set up for the decision. The index weight was objectively determined with the fuzzy number and entropy method. The priority order of auxiliary transportation modes was obtained from the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE). The results show that: the net flow of the mode can be expressed by the function of the surrounding rock deformation of the roadway, the dimension of equipment and the thickness of the coal seam; Based on the cost type index, there is a positive correlation between the net flow with the height and width of the trackless auxiliary transportation equipment, respectively. The trackless auxiliary transportation equipment selection principle should be "height first then width". Combined with the field application of the trackless auxil- iary transportation in Liangshuijing coal mine, the proper method to achieve the safe and high-efficient exploitation of a NHTCS fully-mechanized face is trackless tvred vehicle auxiliary transportation. 展开更多
关键词 nearly horizontalTrackless transportationRail transportationPROMETHEEEntropy methodEquipment selection
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almost与nearly的用法辨析
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作者 郝艳萍 《中小学英语教学与研究》 北大核心 2020年第1期76-78,共3页
在英语中,almost与nearly这两个词都是副词,都有“几乎”“差不多”之意,但用法不尽相同。现分别辨析如下。―、almost与nearly可以互换使用的情况1.在all、always、every和every-构成的复合词之前,almost与nearly可以换用。例如:Almost... 在英语中,almost与nearly这两个词都是副词,都有“几乎”“差不多”之意,但用法不尽相同。现分别辨析如下。―、almost与nearly可以互换使用的情况1.在all、always、every和every-构成的复合词之前,almost与nearly可以换用。例如:Almost(Nearly)all the guests are here.差不多所有的客人都到了。Almost(Nearly)all of the people believed Tom because he was a very good man.因为汤姆为人很好,几乎所有的人都相信他。 展开更多
关键词 nearly 用法辨析 EVERY ALMOST 复合词
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NearlySasak流形的半不变子流形
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作者 万勇 吴世枫 刘雪峰 《长沙电力学院学报(自然科学版)》 2002年第4期1-2,共2页
给出了Nearly Sasak流形的半不变子流形一定平凡.
关键词 nearly Sasak流形 半不变子流型 Levi-Civita联络 第二基本形式 张量结构 诱导联络
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