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Optimization of Linear Antenna Arrays Based on Genetic Algorithms
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作者 王宏建 高本庆 刘瑞祥 《Journal of Beijing Institute of Technology》 EI CAS 2002年第2期180-183,共4页
The methods of moment and genetic algorithm (GA) are combined to optimize the Yagi Uda antenna array and Log periodic dipole antenna (LPDA) array. The element lengths and spacing are optimized for the Yagi Uda arra... The methods of moment and genetic algorithm (GA) are combined to optimize the Yagi Uda antenna array and Log periodic dipole antenna (LPDA) array. The element lengths and spacing are optimized for the Yagi Uda array; while the ratio factor of spacing to length as well as the ratio of length to diameter of the elements are optimized for LPDA array. The results show that the main parameters, such as gain and pattern, have been improved apparently; and the high back lobe level of LPDA can be reduced greatly, therefore, GA is a very competent method for optimizing the linear array as well as in other fields. 展开更多
关键词 GAIN front to back ratio genetic algorithm OPTIMIZATION Yagi Uda antenna Log periodic dipole antenna
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Cosmological Constant and Stability of the Cosmological Models 被引量:1
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作者 WANGYong-Jiu TANGZhi-Ming 《Communications in Theoretical Physics》 SCIE CAS CSCD 2002年第6期667-670,共4页
The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters and were discussed respectively. Near , the cosmological model is unstable with t... The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters and were discussed respectively. Near , the cosmological model is unstable with the change of , and near , the cosmological model is unstable with the change of . So when we consider the stable cosmological model, we must consider the nonzero cosmological constant. 展开更多
关键词 COSMOLOGY cosmological models general relativity
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Holography,UV/IR Relation,Causal Entropy Bound,and Dark Energy 被引量:2
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作者 CAI Rong-Gen HU Bin ZHANG Yi 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第5期954-960,共7页
The constraint on the total energy in a given spatial region is given from holography by the mass of a black hole that just fits in that region, which leads to an UV/IR relation: the maximal energy density in that re... The constraint on the total energy in a given spatial region is given from holography by the mass of a black hole that just fits in that region, which leads to an UV/IR relation: the maximal energy density in that region is proportional to Mp^2/L^2, where Mp is the Planck mass and L is the spatial scale of that region under consideration. Assuming the maximal black hole in the universe is formed through gravitational collapse of perturbations in the universe, then the "Jeans" scale of the perturbations gives a causal connection scale RCC. For gravitational perturbations, RCC^-2= Max (H+ 2H^2, -H) for a fiat universe. We study the cosmological dynamics of the corresponding vacuum energy density by choosing the causal connection scale as the IR cutoff in the UV/IR relation, in the cases of the vacuum energy density as an independently conserved energy component and an effective dynamical cosmological constant, respectively. It turns out that only the case with the choice RCC^-2 = H+ 2H^2, could be consistent with the current cosmological observations when the vacuum density appears as an independently conserved energy component. In this case, the model is called holographic Ricci scalar dark energy model in the literature. 展开更多
关键词 holography of gravity dark energy and cosmology
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Dark Energy Model with Non-Minimal Coupling and Cosmological Constant Boundary
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作者 张晓菲 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第12期1167-1170,共4页
In this paper,we study a kind of dark energy models in the framework of the non-minimal coupling.With this kind of models,dark energy could cross the cosmological constant boundary,and at early time,dark energy could ... In this paper,we study a kind of dark energy models in the framework of the non-minimal coupling.With this kind of models,dark energy could cross the cosmological constant boundary,and at early time,dark energy could have 'tracking' behavior. 展开更多
关键词 dark energy model non-minimal coupling
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Null Geodesics in Brane World Scenarios
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作者 ZHANGLi-Feng ZHANGYuan-Zhong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2004年第1期48-50,共3页
We study the null bulk geodesic motion in the brane world in which the bulk metric has an un-stabilized extra spatial dimension. We find that the null bulk geodesic motion as observed on the 3-brane with Z<SUB>2... We study the null bulk geodesic motion in the brane world in which the bulk metric has an un-stabilized extra spatial dimension. We find that the null bulk geodesic motion as observed on the 3-brane with Z<SUB>2</SUB> symmetry would be a timelike geodesic motion even though there exists an extra non-gravitational force in contrast with the case of the stabilized extra spatial dimension. In other words the presence of the extra non-gravitational force would not violate the Z<SUB>2</SUB> symmetry. 展开更多
关键词 brane universe null geodesic
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Statefinder Parameters for Coupled Quintessence Scenario in a Power Law Case
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作者 ZHANG Xin 《Communications in Theoretical Physics》 SCIE CAS CSCD 2005年第3X期573-576,共4页
We investigate a coupled quintessence scenario, which can provide a natural solution to the cosmic coincidence problem. We assume that the mass of dark matter particles depends on a power law function of the scalar fi... We investigate a coupled quintessence scenario, which can provide a natural solution to the cosmic coincidence problem. We assume that the mass of dark matter particles depends on a power law function of the scalar field associated to dark energy and meanwhile the scalar field evolves in a power law potential. Since the dynamics of this system is dominated by an attractor solution, the mass of dark matter particles is forced to change with time as to ensure that the ratio between the energy densities of dark matter and dark energy becomes a constant at late times,and one thus solves the cosmic coincidence problem naturally. We then apply a statefinder diagnostic to this coupled quintessence scenario. It is shown that the evolving trajectory of this scenario in the s-r diagram is quite different from those of other dark energy models. 展开更多
关键词 coupled quintessence scenario power-law case attractor solution statefinder diagnostic
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A Journey into Fermat's Equation 被引量:1
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作者 Mario De Paz Enzo Bonacci 《Journal of Mathematics and System Science》 2012年第9期539-544,共6页
As expounded in some recent mathematical conferences, this research on that amazing source of algebraic ideas known as Fermat's equation is aimed to prove how Fermat triples can be limited until the impossible existe... As expounded in some recent mathematical conferences, this research on that amazing source of algebraic ideas known as Fermat's equation is aimed to prove how Fermat triples can be limited until the impossible existence through a criterion of incompatible parities related to unexplored properties of the binomial coefficients. In this paper, the authors use a technique based on the analysis of four numbers and their internal relations with three basic compulsory factors. It leads to the practical impossibility to find any triple of natural numbers candidate to satisfy Fermat's equation, because when the authors try to meet a condition between parity and range the authors are compelled to violate the other one, so that they are irreducibly alternative. In particular, there is a parity violation when the authors choose all the basic factors in the allowed range and the authors obtain exceeding values of one of the involved variables when the authors try to restore the parity. Since Fermat's last theorem would consequently be demonstrated, many readers could recall the never found elementary proof of FLT (Fermat's last theorem) claimed by Pierre de Fermat. The authors are not encouraging such an interpretation because this paper is intended as a journey into Fermat's equation and the reader's attitude should be towards the algebraic achievements here proposed, with their possible hidden flaws and future developments, rather than to legendary problems like Fermat's riddle. 展开更多
关键词 Fermat's equation binomial coefficients incompatible parities Fermat's last theorem Fermat's little theorem.
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Nonequilibrium Thermodynamics of Dark Energy on Cosmic Apparent Horizon 被引量:1
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作者 WANG Gang LIU Wen-Biao 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第8期383-384,共2页
In recent several years,some works have been done on cosmic thermodynamics.The apparent horizonwas regarded as the key characteristic supersurface where thermodynamics can be built on perfectly.However,if theirreversi... In recent several years,some works have been done on cosmic thermodynamics.The apparent horizonwas regarded as the key characteristic supersurface where thermodynamics can be built on perfectly.However,if theirreversible process is considered,the proper position for building thermodynamics will not be the apparent horizonanymore.The new position is related to dark energy state equation and the irreversible process parameters. 展开更多
关键词 COSMOLOGY dark energy linear nonequilibrium thermodynamics ENTROPY apparent horizon
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Phantom-Like Effects on Warped DGP Brane
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作者 Kourosh Nozari Tahereh Azizi 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第10期773-780,共8页
We study phantom-like effect on the DGP brane embedded in a five-dimensional AdS bulk. We show that this effect can be realized without phantom matter on this warped DGP brahe. We investigate the role played by the bu... We study phantom-like effect on the DGP brane embedded in a five-dimensional AdS bulk. We show that this effect can be realized without phantom matter on this warped DGP brahe. We investigate the role played by the bulk cosmological constant on the phantom-like effect on the brane and we show that it tends to reduce this effect. Also, warped compactification of the bulk manifold increases the values of the effective and total equation of state parameters of the model relative to the case with Minkowski bulk. We extend our study to the ease that induced curvature on the brahe is modified in the spirit of the f(R)-gravity. 展开更多
关键词 Braneworld cosmology dark energy models warped DGP scenario modified gravity
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Thermodynamics of Third Order Lovelock-Born-Infeld Black Holes
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作者 李鹏 岳瑞宏 邹德成 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第11期845-850,共6页
We here explore black holes in the third order Lovelock gravity coupling with nonlinear Born-Infeld electro- magnetic field. Considering special second and third order coefficients (&g = 363 = a2), we analyze the t... We here explore black holes in the third order Lovelock gravity coupling with nonlinear Born-Infeld electro- magnetic field. Considering special second and third order coefficients (&g = 363 = a2), we analyze the thermodynamics of third order Lovelock-Born-Infeld black holes and, in 7-dimensional AdS space-time, discuss the stability of black holes in different event horizon structures. We find that the cosmological constant A plays an important role in the distribution of black hole stable regions. 展开更多
关键词 third order Lovelock gravity BORN-INFELD THERMODYNAMICS STABILITY
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Determining Topographic Shielding from Digital Elevation Models for Cosmogenic Nuclide Analysis:a GIS Approach and Field Validation 被引量:8
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作者 LI Ying-kui 《Journal of Mountain Science》 SCIE CSCD 2013年第3期355-362,共8页
Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates. Traditionally, this parameter is measured in the field and uncertaint... Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates. Traditionally, this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators. This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models (DEMs). This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface. The DEM-derived parameters using this method were validated with field measurements in central Tian Shan. Results indicate that DEM-derived shielding factors are consistent with field-measured values. It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenie nuclide results. 展开更多
关键词 Cosmogenic nuclides Topographicshielding ARCGIS PYTHON Digital elevation models(DEMs)
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Decoding the Information of Life 被引量:1
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作者 ShantilalG. Goradia 《Journal of Physical Science and Application》 2015年第3期191-195,共5页
We link nuclear force with gravity. We use statistical entropy to link fine-structure constant (ct) and cosmological constant, showing mystical number 137 (as reciprocal of increasing entropy of the universe) as n... We link nuclear force with gravity. We use statistical entropy to link fine-structure constant (ct) and cosmological constant, showing mystical number 137 (as reciprocal of increasing entropy of the universe) as negative entropy needed for life to exist. If our computational route applies to the physical universe, it should apply to life. Molecular biology is searching for the fundamental source of information that would link to the information in DNA. 展开更多
关键词 3rd law of thermodynamics fine-structure constant cosmological constant strong coupling information.
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Interference Phase of Neutrino Oscillation in Schwarzschild-de Sitter Space-Time
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作者 任军 耿金鹏 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第4期665-668,共4页
We study the mass neutrino interference phase in Schwarzschild-de Sitter space time along the null trajectory and the geodesic line and obtain the effects of cosmological constant A on the neutrino oscillation. Firstl... We study the mass neutrino interference phase in Schwarzschild-de Sitter space time along the null trajectory and the geodesic line and obtain the effects of cosmological constant A on the neutrino oscillation. Firstly, in the high energy limit, we find that the phase along the geodesic keeps the double of that along the null. Secondly, we calculate the phase on the condition that the cosmological constant, A, is a small quantity. The correction of the phase due to A is given. Finally, we calculate the proper oscillation length in Schwarzschild-de Sitter space-time, which increases because of the existence of A, compared with the result in Schwarzschild space-time. All of our results can be reduced to those in Schwarzschild space-time as A approaches to zero. 展开更多
关键词 gravitational field Schwarzschild-de Sitter space time neutrino interference phase cosmological constant geodesic line
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Inflation Scheme Derived from Universal Wave Function Interpretation of String Theory
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作者 Dr. Zhi Gang Sha Rulin Xiu 《Journal of Physical Science and Application》 2017年第4期33-37,共5页
Inflation is the most commonly accepted theory in cosmology to explain why the universe appears flat, homogeneous, and isotropic, as well as the origin of the large-scale structure of the cosmos and why no magnetic mo... Inflation is the most commonly accepted theory in cosmology to explain why the universe appears flat, homogeneous, and isotropic, as well as the origin of the large-scale structure of the cosmos and why no magnetic monopoles have been detected. However, so far, the origin of the inflation epoch and what is the hypothetical field, the inflation, giving rise to inflation, remains unknown. String theory is one of the promising candidates for the grand unification theory. Grand unification theory is to use one mathematic formula to describe everything. In this work, we study the inflation scheme in a new development in string theory, UWFIST (universal wave function interpretation of string theory). We show that from UWFIST we can derive from the fundamental theory that the long-range vibration is the possible candidate of inflation. We estimate the vacuum energy created by the long-range vibration and show that it can indeed drive the inflation. 展开更多
关键词 INFLATION string theory universal wave function interpretation of string theory grand unification theory.
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Dark Energy Accretion onto a Black Hole in an Expanding Universe
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作者 SUN Cheng-Yi 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第9期441-444,共4页
By using the solution describing a black hole embedded in the FLRW universe,we obtain the evolvingequation of the black hole mass expressed in terms of the cosmological parameters.The evolving equation indicates thati... By using the solution describing a black hole embedded in the FLRW universe,we obtain the evolvingequation of the black hole mass expressed in terms of the cosmological parameters.The evolving equation indicates thatin the phantom dark energy universe the black hole mass becomes zero before the Big Rip is reached. 展开更多
关键词 black hole dark energy accretion FRW universe
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A Note on Black Hole Information Paradox in de Sitter Spacetimes
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作者 Cosimo Bambi 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第7期78-80,共3页
The possibility of stable or quasi-stable Planck mass black hole remnants as solution to the black hole information paradox is commonly believed phenomenologically unacceptable. Since we need a black hole remnant for ... The possibility of stable or quasi-stable Planck mass black hole remnants as solution to the black hole information paradox is commonly believed phenomenologically unacceptable. Since we need a black hole remnant for every possible initial state, the number of remnants is expected to be infinite and that would lead to remnant pair production in any physical process with a total available energy roughly exceeding the Planck mass. In this note I point out that a positive cosmological constant of the Universe would naturally lead to an upper bound on the number of possible remnants. 展开更多
关键词 black hole information theory evaporation cosmological constant
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Cosmological Constraints on the Sign-Changeable Interactions 被引量:1
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作者 韦浩 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第11期972-980,共9页
Recently, Cai and Su [Phys. Rev. D 81 (2010) 103514] found that the sign of interaction Q in'the dark sector changed in the approximate redshift range of 0.45 ≤ z ≤0.9, by using a modeMndependent method to deal w... Recently, Cai and Su [Phys. Rev. D 81 (2010) 103514] found that the sign of interaction Q in'the dark sector changed in the approximate redshift range of 0.45 ≤ z ≤0.9, by using a modeMndependent method to deal with the observational data. In fact, this result raises a remarkable problem, since most of the familiar interactions cannot change their signs in the whole cosmic history. Motivated by the work of Cai and Su, we have proposed a new type of interaction in a previous work [H. Wei, Nucl. Phys. B 845 (2011) 381]. The key ingredient is the deceleration parameter q in the interaction Q, and hence the interaction Q can change its sign when our universe changes from deceleration (q 〉0) to acceleration (q 〈 0). In the present work, we consider the cosmologicai constraints on this new type of sign-changeable interactions, by using the latest observational data. We find that the cosmological constraints on the model parameters are fairly tight. In particular, the key parameter β can be constrained to a narrow range. 展开更多
关键词 dark energy sign-changeable interaction cosmological constraint
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ADM Mass for Asymptotically de Sitter Space-Time
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作者 黄仕明 岳瑞宏 贾冬燕 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第9期473-476,共4页
In this paper,an ADM mass formula for asymptotically de Sitter(dS) space-time is derived from theenergy-momentum tensor.We take the vacuum dS space as the background and investigate the ADM mass of the(d + 3)-dimensio... In this paper,an ADM mass formula for asymptotically de Sitter(dS) space-time is derived from theenergy-momentum tensor.We take the vacuum dS space as the background and investigate the ADM mass of the(d + 3)-dimensional sphere-symmetric space with a positive cosmological constant,and find that the ADM mass ofasymptotically dS space is based on the ADM mass of Schwarzschild field and the cosmological background brings somesmall mass contribution as well. 展开更多
关键词 ADM mass asymptotically de Sitter space-time cosmological constant
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Metric Expansion from Microscopic Dynamics in an Inhomogeneous Universe
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作者 Sascha Vongehr 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第9期477-483,共7页
Theories with ingredients like the Higgs mechanism, gravitons, and inflaton fields rejuvenate the idea that relativistic kinematics is dynamically emergent. Eternal inflation treats the Hubble constant H as depending ... Theories with ingredients like the Higgs mechanism, gravitons, and inflaton fields rejuvenate the idea that relativistic kinematics is dynamically emergent. Eternal inflation treats the Hubble constant H as depending on location. Microscopic dynamics implies that H is over much smaller lengths than pocket universes to be understood as a local space reproduction rate. We illustrate this via discussing that even exponential inflation in TeV-gravity is slow on the relevant time scale. In our on small scales inhomogeneous cosmos, a reproduction rate H depends on position. We therefore discuss Einstein-Strauss vacuoles and a Lindquist-Wheeler like lattice to connect the local rate properly with the scaling of an expanding cosmos. Consistency allows H to locally depend on Weyl curvature similar to vacuum polarization. We derive a proportionality constant known from Kepler's third law and discuss the implications for the finiteness of the cosmological constant. 展开更多
关键词 general relativity metric expansion black hole infinite Lindquist-Wheeler lattice
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Multiverse Spacetime 被引量:2
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作者 K_haled (Moh'dKhalaf) Suleiman Alnobani 《Journal of Energy and Power Engineering》 2017年第9期584-588,共5页
A theological train of reasoning is avoided in this paper. The properties of the equal operator presented earlier by Alnobani are given here. A view of the present time is given. As a consequence of the presence of ti... A theological train of reasoning is avoided in this paper. The properties of the equal operator presented earlier by Alnobani are given here. A view of the present time is given. As a consequence of the presence of time state, the verses are arranged in couples and every verse including in which we live is a live verse in the same context of human life. This paper interferes with and changes the procedures and philosophy of mathematics itself. Space, mass and time are parts of one whole which is called simply time. The aim of this paper is to make the knowledge of its subject public, so other researchers can contribute to it. The concept of a gate between verses is investigated. 展开更多
关键词 TIME SPACE MULTIVERSE gate.
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