A unilateral self-locking mechanism(USM) was proposed to increase the tractive ability of the inchworm in-pipe robots for pipeline inspection.The USM was basically composed of a cam,a torsional spring and an axis.The ...A unilateral self-locking mechanism(USM) was proposed to increase the tractive ability of the inchworm in-pipe robots for pipeline inspection.The USM was basically composed of a cam,a torsional spring and an axis.The self-locking and virtual work principles were applied to studying the basic self-locking condition of the USM.In order to make the cooperation between the crutch and telescopic mechanism more harmonical,the unlocking time of the USM was calculated.A set of parameters were selected to build a virtual model and fabricate a prototype.Both the simulation and performance experiments were carried out in a pipe with a nominal inside diameter of 160 mm.The results show that USM enables the robot to move quickly in one way,and in the other way it helps the robot get self-locking with the pipe wall.The traction of the inchworm robot can rise to 1.2 kN,beyond the limitation of friction of 0.497 kN.展开更多
A parameterized internal tide dissipation term and self-attraction and loading(SAL) tide term are introduced in a barotropic numerical model to investigate the dynamics of semidiurnal tidal constituents M_2 and S_2 in...A parameterized internal tide dissipation term and self-attraction and loading(SAL) tide term are introduced in a barotropic numerical model to investigate the dynamics of semidiurnal tidal constituents M_2 and S_2 in the Bohai Sea, Yellow Sea and East China Sea(BYECS). The optimal parameters for bottom friction and internal dissipation are obtained through a series of numerical computations. Numerical simulation shows that the tide-generating force contributes 1.2% of M_2 power for the entire BYECS and up to 2.8% for the East China Sea deep basin. SAL tide contributes 4.4% of M_2 power for the BYECS and up to 9.3% for the East China Sea deep basin. Bottom friction plays a major role in dissipating tidal energy in the shelf regions, and the internal tide eff ect is important in the deep water regions. Numerical experiments show that artifi cial removal of tide-generating force in the BYECS can cause a signifi cant dif ference(as much as 30 cm) in model output. Artifi cial removal of SAL tide in the BYECS can cause even greater diff erence, up to 40 cm. This indicates that SAL tide should be taken into account in numerical simulations, especially if the tide-generating force is considered.展开更多
Traditionally, the optimization algorithm based on physics principles has some shortcomings such as low population diversity and susceptibility to local extrema. A new optimization algorithm based on kinetic-molecular...Traditionally, the optimization algorithm based on physics principles has some shortcomings such as low population diversity and susceptibility to local extrema. A new optimization algorithm based on kinetic-molecular theory(KMTOA) is proposed. In the KMTOA three operators are designed: attraction, repulsion and wave. The attraction operator simulates the molecular attraction, with the molecules moving towards the optimal ones, which makes possible the optimization. The repulsion operator simulates the molecular repulsion, with the molecules diverging from the optimal ones. The wave operator simulates the thermal molecules moving irregularly, which enlarges the searching spaces and increases the population diversity and global searching ability. Experimental results indicate that KMTOA prevails over other algorithms in the robustness, solution quality, population diversity and convergence speed.展开更多
Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driv...Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driveline gear ratio and battery parameters are determined. And then a two-level optimization problem is formulated based on analytical target cascading (ATC). At the system level, the optimization of the whole vehicle fuel economy is carried out, while the tractive performance is defined as the constraints. The optimized parameters are cascaded to the subsystem as the optimization targets. At the subsystem level, the final drive and transmission design are optimized to make the ratios as close to the targets as possible. The optimization result shows that the fuel economy had improved significantly, while the tractive performance maintains the former level.展开更多
Gauge theory of gravity is formulated based on principle of local gauge invariance. Because the model hasstrict local gravitational gauge symmetry, and gauge theory of gravity is a perturbatively renormalizable quantu...Gauge theory of gravity is formulated based on principle of local gauge invariance. Because the model hasstrict local gravitational gauge symmetry, and gauge theory of gravity is a perturbatively renormalizable quantum model.However, in the original model, all gauge gravitons are massless. We want to ask whether there exist massive gravitonsin Nature. In this paper, we will propose a gauge model with massive gravitons. The mass term of gravitational gaugefield is introduced into the theory without violating the strict local gravitational gauge symmetry. Massive gravitons canbe considered to be possible origin of dark energy and dark matter in the Universe.展开更多
In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is giv...In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is given by the first term of quantum Wilson loop (w) through two-point Green's function of the connection. At the same time using the tree diagram propagators of gravitons, the lowest order (k^4) correction to (w) is also calculated through the graviton self-energy in the term. Under the accuracy condition up to order k^4, we have obtained a complete expression of the excitation contributed from the leading term (w^(2))of (w).展开更多
A cosmological model based on gauge theory of gravity is proposed in thispaper. Combining cosmological principle and field equation of gravitational gauge field, dynamicalequations of the scale factor R(t) of our univ...A cosmological model based on gauge theory of gravity is proposed in thispaper. Combining cosmological principle and field equation of gravitational gauge field, dynamicalequations of the scale factor R(t) of our universe can be obtained. This set of equations has threedifferent solutions. A prediction of the present model is that, if the energy density of theuniverse is not zero and the universe is expanding, the universe must be space-fiat, the totalenergy density must be the critical density ρ_c of the universe. For space-Bat case, this modelgives the same solution as that of the Friedmann model. In other words, though they have differentdynamics of gravitational interactions, general relativity and gauge theory of gravity give the samecosmological model.展开更多
Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confine...Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confinement within the constant energy charge of a moving thermodynamical body. Zero energy-momentum gravitons provide dissipative self-heating and spiral fall of massive stars on gravitating centers. Computed self-heating of the pulsar PSR B1913+16 quantitatively describes its period decay without an outward emission of metric waves in question. Deviation of warm bodies from geodesic trajectories of cold point matter complies with Einstein's directives toward pure field physics of material space plenum without metric singularities.展开更多
Two spherically symmetric non-singular black hole solutions in Moiler tetrad theory of gravitation have been obtained. Although the two solutions have the same form of metric (spherically symmetric nonsingular black ...Two spherically symmetric non-singular black hole solutions in Moiler tetrad theory of gravitation have been obtained. Although the two solutions have the same form of metric (spherically symmetric nonsingular black hole), their energy contents are different. We use another method given by Gibbons and Hawking to calculate the energy content of these solutions. We also obtained different value of energy. Study the requirements of a satisfactory energymomentum complex given by Moiler we find that the second solution, which behaves as 1/√r, is not transformed as a four-vector under Lorentz transformation.展开更多
The Hawking radiation via tunneling from the dilaton black hole in de Sitter universe is investigated using Parikh Wilczek's method. We show that if the self-gravitational interaction and energy conservation are take...The Hawking radiation via tunneling from the dilaton black hole in de Sitter universe is investigated using Parikh Wilczek's method. We show that if the self-gravitational interaction and energy conservation are taken into account, the modified radiation spectrum deviates from exact thermal spectrum and satisfies the unitary theory.展开更多
By employing three typical equations of states (EOSs) of the crust matter, the effect of the crust on the structure and properties are investigated, where the core matter is described by the MDIxl model and the non-...By employing three typical equations of states (EOSs) of the crust matter, the effect of the crust on the structure and properties are investigated, where the core matter is described by the MDIxl model and the non-Newtonian gravity (described by the Yukawa contribution) is considered. It is shown that the EOSs of the crust matter have a notable effect on the mass-radius relation and the moment of inertia.展开更多
Gravity and electromagnetism are two sides of the same coin, which is the clue of this unification. Gravity and electromagnetism are represented by two mathematical structures, symmetric and antisymmetric respectively...Gravity and electromagnetism are two sides of the same coin, which is the clue of this unification. Gravity and electromagnetism are represented by two mathematical structures, symmetric and antisymmetric respectively. Einstein gravitational field equation is the symmetric mathematical structure. Electrodynamics Lagrangian is three parts, for electromagnetic field, Dirac field and interaction term. The definition of canonical energy momentum tensor was used for each term in Electrodynamics Lagrangian to construct the antisymmetric mathematical structure; symmetric and antisymmetric gravitational field equations are two sides of the same Lagrangian.展开更多
Disk burst accidents sometimes happen in aeroengines.To avoid tragic consequences,aeroengine casings must have sufficient containment capability.Experiments and simulations need to be conducted to study the impact,dis...Disk burst accidents sometimes happen in aeroengines.To avoid tragic consequences,aeroengine casings must have sufficient containment capability.Experiments and simulations need to be conducted to study the impact,distortion,and perforation caused by disk burst and which may give important clues to potential failure mechanisms.This paper presents some containment tests of high-speed rotating disk fragments,in which the original disks were burst into three equal fragments within a predetermined rotating speed range.The failure modes of the containment casing varied significantly with the thickness of the containment casing.Shearing,tearing,tensile fracture,and large plastic stretching deformation occurred in a thin-walled containment casing,while a thick-walled casing could contain disk fragments and withstand large plastic deformation.Numerical simulations were carried out to study the impact process and failure modes further.Good agreement was found between the results of the simulations and the tests.展开更多
Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm ch...Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm characteristics depend on an indi- vidual's ability to cope with oxidative stress. Carotenoids are known for their antioxidant properties and carotenoid-based orna- ments might represent honest signals as these pigments can be traded offbetween the investment in sexual ornamentation, sperm function as well as immune response. In this study, we examined the relationship between sexual ornamentation (breeding colo- ration) and sperm characteristics (e.g., velocity and morphology) in the three-spined stickleback Gasterosteus aeuleatus, an ex- ternally fertilising fish species, in which sperm competition commonly occurs. During the breeding season males are sperm limi- ted and develop a conspicuous carotenoid-based coloration, which is under strong pre-copulatory sexual selection due to female mate choice and male-male competition. The results of the present study show that the expression of stickleback male breeding coloration is significantly positively associated with the linearity of sperm movement, whereas sperm morphology (head length to tail length ratio) is significantly negatively related to the trajectory of sperm movement. Moreover, there is some support for the phenotype-linked fertility hypothesis as the intensity of male red breeding coloration is significantly positively correlated with sperm velocity, which is supposed to be an important determinant of fertilisation success in external fertilisers, indicating the honesty of the sexually selected nuptial red coloration.展开更多
The solutions of the Schrodinger equation with quantum mechanical gravitational potential plus harmonic oscillator potential have been presented using the parametric Nikiforov-Uvarov method. The bound state energy eig...The solutions of the Schrodinger equation with quantum mechanical gravitational potential plus harmonic oscillator potential have been presented using the parametric Nikiforov-Uvarov method. The bound state energy eigen values and the corresponding un-normalized eigen functions are obtained in terms of Laguerre polynomials. Also a special case of the potential has been considered and its energy eigen values are obtained.展开更多
Forecasting exchange rate is undoubtedly an attractive and challenging issue that has been of interest in different domains for many years. The singular spectrum analysis (SSA) technique has been used as a promising...Forecasting exchange rate is undoubtedly an attractive and challenging issue that has been of interest in different domains for many years. The singular spectrum analysis (SSA) technique has been used as a promising technique for time series forecasting including exchange rate series. The SSA technique is based upon two main choices: Window length, L, and the number of singular values, r. These values are very important for the reconstruction stage and forecasting purposes. Here the authors consider an optimum version of the SSA technique for forecasting exchange rates. The forecasting performances of the SSA technique for one-step-ahead forecast of six exchange rate series are used to find the best L and r.展开更多
Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a resul...Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a result of mistaking different geometrical, physical ob jects as one and the same. It is also pointed out that in a curved spacetime, the sum vector of matter energy-momentum over a finite hyper-surface can not be defined. In curvilinear coordinate systems conservation of matter energy-momentum is not the continuity equations for its components. Conservation of matter energy-momentum is the vanishing of the covariant divergence of its density-flux tensor field. Introducing gravitational energy-momentum to save the law of conservation of energy-momentum is unnecessary and improper. After reasonably defining "change of a particle's energy-momentum", we show that gravitational field does not exchange energy-momentum with particles. And it does not exchange energy-momentum with matter fields either. Therefore, the gravitational field does not carry energy-momentum, it is not a force field and gravity is not a natural force.展开更多
This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, ...This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, with high stability lasers and various techniques for suppressing noise. Sect. 1 of this paper presents a review of the acoustic properties of test masses. Sect. 2 reviews the technology of the amorphous dielectric coatings which are currently universally used for the mirrors in advanced laser interferometers, but for which lower acoustic loss would be very advantageous. In sect. 3 a new generation of crystalline optical coatings that offer a substantial reduction in thermal noise is reviewed. The optical properties of test masses are reviewed in sect. 4, with special focus on the properties of silicon, an important candidate material for future detectors. Sect. 5 of this paper presents the very low noise, high stability laser technology that underpins all advanced and next generation laser interferometers.展开更多
In the standard model of particle physics, photons are massless particles with a particular dispersion relation. Tests of this claim at different scales are both interesting and important. Experiments in territory lab...In the standard model of particle physics, photons are massless particles with a particular dispersion relation. Tests of this claim at different scales are both interesting and important. Experiments in territory labs and several exterritorial tests have put some upper limits on photon mass, e.g., torsion balance experiment in the lab shows that photon mass should be smaller than 1.2 x 10-51g. In this work, this claim is tested at a cosmological scale by looking at strong gravitational lensing data available and an upper limit of 8.71 x 10-39g on photon mass is given. Observations of energy-dependent gravitational lensing with not yet available higher accuracy astrometry instruments may constrain photon mass better.展开更多
基金Project(2007AA04Z256) supported by the National High-Tech Research and Development Program of China
文摘A unilateral self-locking mechanism(USM) was proposed to increase the tractive ability of the inchworm in-pipe robots for pipeline inspection.The USM was basically composed of a cam,a torsional spring and an axis.The self-locking and virtual work principles were applied to studying the basic self-locking condition of the USM.In order to make the cooperation between the crutch and telescopic mechanism more harmonical,the unlocking time of the USM was calculated.A set of parameters were selected to build a virtual model and fabricate a prototype.Both the simulation and performance experiments were carried out in a pipe with a nominal inside diameter of 160 mm.The results show that USM enables the robot to move quickly in one way,and in the other way it helps the robot get self-locking with the pipe wall.The traction of the inchworm robot can rise to 1.2 kN,beyond the limitation of friction of 0.497 kN.
基金Supported by the National Natural Science Foundation of China(Nos.40676009,40606006)the Qingdao Science and Technology Basic Research Program(No.11-1-4-98-jch)
文摘A parameterized internal tide dissipation term and self-attraction and loading(SAL) tide term are introduced in a barotropic numerical model to investigate the dynamics of semidiurnal tidal constituents M_2 and S_2 in the Bohai Sea, Yellow Sea and East China Sea(BYECS). The optimal parameters for bottom friction and internal dissipation are obtained through a series of numerical computations. Numerical simulation shows that the tide-generating force contributes 1.2% of M_2 power for the entire BYECS and up to 2.8% for the East China Sea deep basin. SAL tide contributes 4.4% of M_2 power for the BYECS and up to 9.3% for the East China Sea deep basin. Bottom friction plays a major role in dissipating tidal energy in the shelf regions, and the internal tide eff ect is important in the deep water regions. Numerical experiments show that artifi cial removal of tide-generating force in the BYECS can cause a signifi cant dif ference(as much as 30 cm) in model output. Artifi cial removal of SAL tide in the BYECS can cause even greater diff erence, up to 40 cm. This indicates that SAL tide should be taken into account in numerical simulations, especially if the tide-generating force is considered.
基金Project(61174140)supported by the National Natural Science Foundation of ChinaProject(13JJA002)supported by Hunan Provincial Natural Science Foundation,ChinaProject(20110161110035)supported by the Doctoral Fund of Ministry of Education of China
文摘Traditionally, the optimization algorithm based on physics principles has some shortcomings such as low population diversity and susceptibility to local extrema. A new optimization algorithm based on kinetic-molecular theory(KMTOA) is proposed. In the KMTOA three operators are designed: attraction, repulsion and wave. The attraction operator simulates the molecular attraction, with the molecules moving towards the optimal ones, which makes possible the optimization. The repulsion operator simulates the molecular repulsion, with the molecules diverging from the optimal ones. The wave operator simulates the thermal molecules moving irregularly, which enlarges the searching spaces and increases the population diversity and global searching ability. Experimental results indicate that KMTOA prevails over other algorithms in the robustness, solution quality, population diversity and convergence speed.
文摘Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driveline gear ratio and battery parameters are determined. And then a two-level optimization problem is formulated based on analytical target cascading (ATC). At the system level, the optimization of the whole vehicle fuel economy is carried out, while the tractive performance is defined as the constraints. The optimized parameters are cascaded to the subsystem as the optimization targets. At the subsystem level, the final drive and transmission design are optimized to make the ratios as close to the targets as possible. The optimization result shows that the fuel economy had improved significantly, while the tractive performance maintains the former level.
文摘Gauge theory of gravity is formulated based on principle of local gauge invariance. Because the model hasstrict local gravitational gauge symmetry, and gauge theory of gravity is a perturbatively renormalizable quantum model.However, in the original model, all gauge gravitons are massless. We want to ask whether there exist massive gravitonsin Nature. In this paper, we will propose a gauge model with massive gravitons. The mass term of gravitational gaugefield is introduced into the theory without violating the strict local gravitational gauge symmetry. Massive gravitons canbe considered to be possible origin of dark energy and dark matter in the Universe.
基金The project partially supported by Fund of the Education Department of Hubei Province of China under Grant No. D200534001
文摘In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is given by the first term of quantum Wilson loop (w) through two-point Green's function of the connection. At the same time using the tree diagram propagators of gravitons, the lowest order (k^4) correction to (w) is also calculated through the graviton self-energy in the term. Under the accuracy condition up to order k^4, we have obtained a complete expression of the excitation contributed from the leading term (w^(2))of (w).
文摘A cosmological model based on gauge theory of gravity is proposed in thispaper. Combining cosmological principle and field equation of gravitational gauge field, dynamicalequations of the scale factor R(t) of our universe can be obtained. This set of equations has threedifferent solutions. A prediction of the present model is that, if the energy density of theuniverse is not zero and the universe is expanding, the universe must be space-fiat, the totalenergy density must be the critical density ρ_c of the universe. For space-Bat case, this modelgives the same solution as that of the Friedmann model. In other words, though they have differentdynamics of gravitational interactions, general relativity and gauge theory of gravity give the samecosmological model.
文摘Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confinement within the constant energy charge of a moving thermodynamical body. Zero energy-momentum gravitons provide dissipative self-heating and spiral fall of massive stars on gravitating centers. Computed self-heating of the pulsar PSR B1913+16 quantitatively describes its period decay without an outward emission of metric waves in question. Deviation of warm bodies from geodesic trajectories of cold point matter complies with Einstein's directives toward pure field physics of material space plenum without metric singularities.
文摘Two spherically symmetric non-singular black hole solutions in Moiler tetrad theory of gravitation have been obtained. Although the two solutions have the same form of metric (spherically symmetric nonsingular black hole), their energy contents are different. We use another method given by Gibbons and Hawking to calculate the energy content of these solutions. We also obtained different value of energy. Study the requirements of a satisfactory energymomentum complex given by Moiler we find that the second solution, which behaves as 1/√r, is not transformed as a four-vector under Lorentz transformation.
基金supported by the Natural Science Foundation of Zhanjiang Normal University
文摘The Hawking radiation via tunneling from the dilaton black hole in de Sitter universe is investigated using Parikh Wilczek's method. We show that if the self-gravitational interaction and energy conservation are taken into account, the modified radiation spectrum deviates from exact thermal spectrum and satisfies the unitary theory.
基金Supported by the National Natural Science Foundation of China under Grant No.10947023the Fundamental Research Funds for the Central Universities under Grant No.2009ZM0193the SRP of SCUT under Grant No.D210632w
文摘By employing three typical equations of states (EOSs) of the crust matter, the effect of the crust on the structure and properties are investigated, where the core matter is described by the MDIxl model and the non-Newtonian gravity (described by the Yukawa contribution) is considered. It is shown that the EOSs of the crust matter have a notable effect on the mass-radius relation and the moment of inertia.
文摘Gravity and electromagnetism are two sides of the same coin, which is the clue of this unification. Gravity and electromagnetism are represented by two mathematical structures, symmetric and antisymmetric respectively. Einstein gravitational field equation is the symmetric mathematical structure. Electrodynamics Lagrangian is three parts, for electromagnetic field, Dirac field and interaction term. The definition of canonical energy momentum tensor was used for each term in Electrodynamics Lagrangian to construct the antisymmetric mathematical structure; symmetric and antisymmetric gravitational field equations are two sides of the same Lagrangian.
基金Project supported by the Chinese Aviation Propulsion Technology Development Program (No. APTD-11)the Zhejiang Provincial Natural Science Foundation of China (No. Y1090245)
文摘Disk burst accidents sometimes happen in aeroengines.To avoid tragic consequences,aeroengine casings must have sufficient containment capability.Experiments and simulations need to be conducted to study the impact,distortion,and perforation caused by disk burst and which may give important clues to potential failure mechanisms.This paper presents some containment tests of high-speed rotating disk fragments,in which the original disks were burst into three equal fragments within a predetermined rotating speed range.The failure modes of the containment casing varied significantly with the thickness of the containment casing.Shearing,tearing,tensile fracture,and large plastic stretching deformation occurred in a thin-walled containment casing,while a thick-walled casing could contain disk fragments and withstand large plastic deformation.Numerical simulations were carried out to study the impact process and failure modes further.Good agreement was found between the results of the simulations and the tests.
文摘Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm characteristics depend on an indi- vidual's ability to cope with oxidative stress. Carotenoids are known for their antioxidant properties and carotenoid-based orna- ments might represent honest signals as these pigments can be traded offbetween the investment in sexual ornamentation, sperm function as well as immune response. In this study, we examined the relationship between sexual ornamentation (breeding colo- ration) and sperm characteristics (e.g., velocity and morphology) in the three-spined stickleback Gasterosteus aeuleatus, an ex- ternally fertilising fish species, in which sperm competition commonly occurs. During the breeding season males are sperm limi- ted and develop a conspicuous carotenoid-based coloration, which is under strong pre-copulatory sexual selection due to female mate choice and male-male competition. The results of the present study show that the expression of stickleback male breeding coloration is significantly positively associated with the linearity of sperm movement, whereas sperm morphology (head length to tail length ratio) is significantly negatively related to the trajectory of sperm movement. Moreover, there is some support for the phenotype-linked fertility hypothesis as the intensity of male red breeding coloration is significantly positively correlated with sperm velocity, which is supposed to be an important determinant of fertilisation success in external fertilisers, indicating the honesty of the sexually selected nuptial red coloration.
文摘The solutions of the Schrodinger equation with quantum mechanical gravitational potential plus harmonic oscillator potential have been presented using the parametric Nikiforov-Uvarov method. The bound state energy eigen values and the corresponding un-normalized eigen functions are obtained in terms of Laguerre polynomials. Also a special case of the potential has been considered and its energy eigen values are obtained.
基金supported by a grant from Payame Noor University, Tehran-Iran
文摘Forecasting exchange rate is undoubtedly an attractive and challenging issue that has been of interest in different domains for many years. The singular spectrum analysis (SSA) technique has been used as a promising technique for time series forecasting including exchange rate series. The SSA technique is based upon two main choices: Window length, L, and the number of singular values, r. These values are very important for the reconstruction stage and forecasting purposes. Here the authors consider an optimum version of the SSA technique for forecasting exchange rates. The forecasting performances of the SSA technique for one-step-ahead forecast of six exchange rate series are used to find the best L and r.
文摘Based on a general variational principle, Einstein–Hilbert action and sound facts from geometry, it is shown that the long existing pseudotensor, non-localizability problem of gravitational energy-momentum is a result of mistaking different geometrical, physical ob jects as one and the same. It is also pointed out that in a curved spacetime, the sum vector of matter energy-momentum over a finite hyper-surface can not be defined. In curvilinear coordinate systems conservation of matter energy-momentum is not the continuity equations for its components. Conservation of matter energy-momentum is the vanishing of the covariant divergence of its density-flux tensor field. Introducing gravitational energy-momentum to save the law of conservation of energy-momentum is unnecessary and improper. After reasonably defining "change of a particle's energy-momentum", we show that gravitational field does not exchange energy-momentum with particles. And it does not exchange energy-momentum with matter fields either. Therefore, the gravitational field does not carry energy-momentum, it is not a force field and gravity is not a natural force.
基金financial support during The Next Detectors for Gravitational Wave Astronomy workshop in Beijing in 2015
文摘This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, with high stability lasers and various techniques for suppressing noise. Sect. 1 of this paper presents a review of the acoustic properties of test masses. Sect. 2 reviews the technology of the amorphous dielectric coatings which are currently universally used for the mirrors in advanced laser interferometers, but for which lower acoustic loss would be very advantageous. In sect. 3 a new generation of crystalline optical coatings that offer a substantial reduction in thermal noise is reviewed. The optical properties of test masses are reviewed in sect. 4, with special focus on the properties of silicon, an important candidate material for future detectors. Sect. 5 of this paper presents the very low noise, high stability laser technology that underpins all advanced and next generation laser interferometers.
文摘In the standard model of particle physics, photons are massless particles with a particular dispersion relation. Tests of this claim at different scales are both interesting and important. Experiments in territory labs and several exterritorial tests have put some upper limits on photon mass, e.g., torsion balance experiment in the lab shows that photon mass should be smaller than 1.2 x 10-51g. In this work, this claim is tested at a cosmological scale by looking at strong gravitational lensing data available and an upper limit of 8.71 x 10-39g on photon mass is given. Observations of energy-dependent gravitational lensing with not yet available higher accuracy astrometry instruments may constrain photon mass better.