Relay作为LTE-Advanced系统关键技术之一,可以为运营商提供灵活、快捷的网络部署手段,提高网络的覆盖和容量。本文在分析比较各种Relay技术方案的基础上,着重分析了3GPP对于Type I Relay和Type II Relay的定义及功能,并结合3GPP Rel.10...Relay作为LTE-Advanced系统关键技术之一,可以为运营商提供灵活、快捷的网络部署手段,提高网络的覆盖和容量。本文在分析比较各种Relay技术方案的基础上,着重分析了3GPP对于Type I Relay和Type II Relay的定义及功能,并结合3GPP Rel.10标准化进展,重点介绍Type IRelay在LTE-Advanced系统中的方案设计。展开更多
The paper is devoted to the study of the gravitational collapse within the framework of the spherically symmetric problem in the Newton theory and general relativity on the basis of the pressure-free model of the cont...The paper is devoted to the study of the gravitational collapse within the framework of the spherically symmetric problem in the Newton theory and general relativity on the basis of the pressure-free model of the continuum. In application to the Newton gravitation theory, the analysis consists of three stages. First, we assume that the gravitational force is determined by the initial sphere radius and constant density and does not change in the process of the sphere collapse. The obtained analytical solution allows us to find the collapse time in the first approximation. Second, we construct the step-by-step process in which the gravitational force at a given time moment depends on the current sphere radius and density. The obtained numerical solution specifies the collapse time depending on the number of steps. Third, we find the exact value of the collapse time which is the limit of the step-by-step solutions and study the collapse and the expansion processes in the Newton theory. In application to general relativity, we use the space model corresponding to the special four-dimensional space which is Euclidean with respect to space coordinates and Riemannian with respect to the time coordinate only. The obtained solution specifies two possible scenarios. First, sphere contraction results in the infinitely high density with the finite collapse time, which does not coincide with the conventional result corresponding to the Schwarzschild geometry. Second, sphere expansion with the velocity which increases with a distance from the sphere center and decreases with time.展开更多
In the present article,we introduce a completely new regular model for static,spherically symmetric celestial fluid spheres in embedding classⅠspacetime.In this regard,needfully,we propose a new suitable metric poten...In the present article,we introduce a completely new regular model for static,spherically symmetric celestial fluid spheres in embedding classⅠspacetime.In this regard,needfully,we propose a new suitable metric potential e^(λ(r))to generate the present model.The various analyses on energy density,pressure,anisotropic factor,mass,compactness parameter,redshift,and energy condition make sure the model is physically viable on the ground of model stars Vela X-1,Cen X-3,SMC X-4,and LMC X-4.The reported solutions also respect the equilibrium state by satisfying the Tolman-Oppenheimer-Volkoff(TOV)equation and ensure stability by satisfying the causality condition,condition on the adiabatic index,and Harrison-Zeldovich-Novikov condition.The generated M-R graph matches the ranges of masses and radii for the model compact stars.Additionally,this study provides estimates of the moment of inertia based on the I-M graph.展开更多
Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in f...Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in flow hydraulic and creates an interaction between the main channel and floodplains, resulting in an apparent shear stress and a transverse momentum transfer. The amount of such a stress plays an important role in many river engineering measures [1]. Due to the flow complexity, the common approximate analytical methods are not enough to identify the flow profile. The FLOW3D Software with its great features in three-dimensional analysis of flow field is used as a tool to investigate the shear stress in a direct symmetrical compound rectangular channel. After the simulation of models, it is found that an increase in the relative width and relative depth parameters decreases the percentage of apparent shear stress and an increase in the relative roughness causes it to be increased [2].展开更多
An association rules mining method based on semantic relativity is proposed to solve the problem that there are more candidate item sets and higher time complexity in traditional association rules mining.Semantic rela...An association rules mining method based on semantic relativity is proposed to solve the problem that there are more candidate item sets and higher time complexity in traditional association rules mining.Semantic relativity of ontology concepts is used to describe complicated relationships of domains in the method.Candidate item sets with less semantic relativity are filtered to reduce the number of candidate item sets in association rules mining.An ontology hierarchy relationship is regarded as a directed acyclic graph rather than a hierarchy tree in the semantic relativity computation.Not only direct hierarchy relationships,but also non-direct hierarchy relationships and other typical semantic relationships are taken into account.Experimental results show that the proposed method can reduce the number of candidate item sets effectively and improve the efficiency of association rules mining.展开更多
The principles of special relativity and Einstein’s simple derivation of the Lorentz transformation are reviewed. A new simple derivation of the Lorentz transformation is developed in this paper, by a new approach of...The principles of special relativity and Einstein’s simple derivation of the Lorentz transformation are reviewed. A new simple derivation of the Lorentz transformation is developed in this paper, by a new approach of light-pulse observation or time-dilation observation. Therefore, under the two principles of special relativity, there exist two equivalent simple derivations of or two equivalent approaches to the Lorentz transformation. Einstein’s approach emphasizes or highlights relativity of space while our approach emphasizes or highlights relativity of time. This research reveals, in a particular way, the equivalence of relativity of space and relativity of time in special relativity. Combination of Einstein’s approach and the approach developed in this paper makes the methodology of simple derivation of the Lorentz transformation complete and perfect.展开更多
Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse...Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages： absolute orienta- tion and depth recovery. In the first stage, Umeyama＇s algorithm is used to fit the three-dimensional （3D） model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoreti- cal analysis and mathematical simulation.展开更多
文摘Relay作为LTE-Advanced系统关键技术之一,可以为运营商提供灵活、快捷的网络部署手段,提高网络的覆盖和容量。本文在分析比较各种Relay技术方案的基础上,着重分析了3GPP对于Type I Relay和Type II Relay的定义及功能,并结合3GPP Rel.10标准化进展,重点介绍Type IRelay在LTE-Advanced系统中的方案设计。
文摘第三代合作伙伴计划(3rd Generation Partnership Project,3GPP)非地面网络(non-terrestrial network,NTN)通过对5G新空口(new radio,NR)协议进行增强设计以适应卫星通信场景,可深度融合地面网络与非地面网络优势,并具备持续演进能力,是实现天地互联的关键技术方向。为应对星地传输功率与频谱资源的限制以及对广覆盖与高容量的双重需求,Rel-19 NR NTN工作组针对下行覆盖增强与上行容量/吞吐量增强两大子议题开展了标准化研究。基于此,首先概述了NTN传输的技术挑战,继而系统分析了上述议题的技术方案及标准化进展,最后展望了Rel-20 NR NTN潜在的传输增强技术演进方向。
文摘The paper is devoted to the study of the gravitational collapse within the framework of the spherically symmetric problem in the Newton theory and general relativity on the basis of the pressure-free model of the continuum. In application to the Newton gravitation theory, the analysis consists of three stages. First, we assume that the gravitational force is determined by the initial sphere radius and constant density and does not change in the process of the sphere collapse. The obtained analytical solution allows us to find the collapse time in the first approximation. Second, we construct the step-by-step process in which the gravitational force at a given time moment depends on the current sphere radius and density. The obtained numerical solution specifies the collapse time depending on the number of steps. Third, we find the exact value of the collapse time which is the limit of the step-by-step solutions and study the collapse and the expansion processes in the Newton theory. In application to general relativity, we use the space model corresponding to the special four-dimensional space which is Euclidean with respect to space coordinates and Riemannian with respect to the time coordinate only. The obtained solution specifies two possible scenarios. First, sphere contraction results in the infinitely high density with the finite collapse time, which does not coincide with the conventional result corresponding to the Schwarzschild geometry. Second, sphere expansion with the velocity which increases with a distance from the sphere center and decreases with time.
文摘In the present article,we introduce a completely new regular model for static,spherically symmetric celestial fluid spheres in embedding classⅠspacetime.In this regard,needfully,we propose a new suitable metric potential e^(λ(r))to generate the present model.The various analyses on energy density,pressure,anisotropic factor,mass,compactness parameter,redshift,and energy condition make sure the model is physically viable on the ground of model stars Vela X-1,Cen X-3,SMC X-4,and LMC X-4.The reported solutions also respect the equilibrium state by satisfying the Tolman-Oppenheimer-Volkoff(TOV)equation and ensure stability by satisfying the causality condition,condition on the adiabatic index,and Harrison-Zeldovich-Novikov condition.The generated M-R graph matches the ranges of masses and radii for the model compact stars.Additionally,this study provides estimates of the moment of inertia based on the I-M graph.
文摘Compound section is referred to a section the surface of which is made of several sub-sections with different flow characteristics. The difference in the hydraulic and geometry characteristics causes a complexity in flow hydraulic and creates an interaction between the main channel and floodplains, resulting in an apparent shear stress and a transverse momentum transfer. The amount of such a stress plays an important role in many river engineering measures [1]. Due to the flow complexity, the common approximate analytical methods are not enough to identify the flow profile. The FLOW3D Software with its great features in three-dimensional analysis of flow field is used as a tool to investigate the shear stress in a direct symmetrical compound rectangular channel. After the simulation of models, it is found that an increase in the relative width and relative depth parameters decreases the percentage of apparent shear stress and an increase in the relative roughness causes it to be increased [2].
基金The National Natural Science Foundation of China(No.50674086)Specialized Research Fund for the Doctoral Program of Higher Education(No.20060290508)the Science and Technology Fund of China University of Mining and Technology(No.2007B016)
文摘An association rules mining method based on semantic relativity is proposed to solve the problem that there are more candidate item sets and higher time complexity in traditional association rules mining.Semantic relativity of ontology concepts is used to describe complicated relationships of domains in the method.Candidate item sets with less semantic relativity are filtered to reduce the number of candidate item sets in association rules mining.An ontology hierarchy relationship is regarded as a directed acyclic graph rather than a hierarchy tree in the semantic relativity computation.Not only direct hierarchy relationships,but also non-direct hierarchy relationships and other typical semantic relationships are taken into account.Experimental results show that the proposed method can reduce the number of candidate item sets effectively and improve the efficiency of association rules mining.
文摘The principles of special relativity and Einstein’s simple derivation of the Lorentz transformation are reviewed. A new simple derivation of the Lorentz transformation is developed in this paper, by a new approach of light-pulse observation or time-dilation observation. Therefore, under the two principles of special relativity, there exist two equivalent simple derivations of or two equivalent approaches to the Lorentz transformation. Einstein’s approach emphasizes or highlights relativity of space while our approach emphasizes or highlights relativity of time. This research reveals, in a particular way, the equivalence of relativity of space and relativity of time in special relativity. Combination of Einstein’s approach and the approach developed in this paper makes the methodology of simple derivation of the Lorentz transformation complete and perfect.
基金Program for Changjiang Scholars and Innovative Research Team in University (IRT0520)Ph.D.Programs Foundation of Ministry of Education of China (20070213055)
文摘Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range ren- dezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages： absolute orienta- tion and depth recovery. In the first stage, Umeyama＇s algorithm is used to fit the three-dimensional （3D） model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoreti- cal analysis and mathematical simulation.
