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《中国科学: 物理学 力学 天文学》英文版第6期在线发布
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《中国科学: 物理学 力学 天文学》英文版第6期在线发布
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SCIENCE CHINA Physics, Mechanics & Astronomy 2014, Volume 57, Issue 6 have been published online on 22 April, 2014, in this issue, some articles maybe interest: Shell model calculations for the allowed Gamow-Teller β-decays of light nuclei PDF, is contributed by Prof. REN ZhongZhou (Associate Editor) from Nanjing University. Herein they use shell model calculations to calculate the allowed Gamow-Teller β-decay information of Li, Be, B, C, and N isotopes which are of interest and compare to determined experimental results; Plasmonic-enhanced two-photon fluorescence with single gold nanoshell PDF, is contributed by Prof. GONG QiHuang (Associate Editor in-Chief) from Peking University, a paper proposed a configuration consisting of single plasmonic nanoshell and fluorescent emitters to efficiently achieve high two-photon fluorescence; A high-efficiency aerothermoelastic analysis method PDF, is contributed by Prof. YANG Chao from Beihang University, by using two-way coupling form and unified hypersonic lifting surface theory, a new aerothermoelastic analysis method with high efficiency and accuracy is established; Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed PDF, is contributed by Prof. ZHANG Xin from Northwestern Polytechnical University, has developed a novel plasma actuator to improve the plasma authority at high wind speed and explored the flow separation control of an Unmanned Aerial Vehicle (UAV) at the wind speed of 100 m/s; Competition of the multiple Görtler modes in hypersonic boundary layer flows PDF,is contributed by Prof. FU Song (Associate Editor in-Chief) from Tsinghua University, by using the linear stability theory (LST) and parabolized stability equation (PSE), this paper propose a competition mechanism of the multiple Görtler modes in hypersonic boundary layer flows, and the study is a guidance for future studies of the secondary instability of Görtler vortices and flow transition in hypersonic boundary flows; Double-peaked decay of transient photovoltage in nanoporous ZnO/n-Si photodetector PDF, is contributed by Prof. ZHAO Kun from China University of Petroleum, by using a nanoporous ZnO/n-Si heterojunction structure, a new type of photo-energy detector of infrared pulsed laser has been proposed. Anyway, we think all of the articles in this issue are equally important and worth reading, we hope these articles are benifit to your research work. We really appreciate your kindly citing for the papers from SCIENCE CHINA Physics, Mechanics & Astronomy when you submit your papers to other journals! Outside China please click http://link.springer.com/journal/11433 for the fulltext PDF.
Best wishes, Editorial Office SCIENCE CHINA Physics, Mechanics & Astronomy | |
| SCIENCE CHINA Physics, Mechanics & Astronomy 2014, Volume 57, Issue 6 Home | Current Issue | All Past Issues | Search | |
| Article | |
| 1005 | Shell model calculations for the allowed Gamow-Teller β-decays of light nuclei PDF (777KB) |
| Cite | LI HanTao, REN ZhongZhou. Shell model calculations for the allowed Gamow-Teller β-decays of light nuclei. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1005-1012. | |
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| The allowed Gamow-Teller β-decay information of Li, Be, B, C, and N isotopes under the frame work of nuclear shell model is calculated herein. Theoretical results of Q values, half-lives, excitation energies, log ft values, branching fractions, and β-delayed proton/neutron emission probabilities are tabulated and compared with experimental data. The deviations from the observations are also analyzed. The 11Be nucleus is well known for its anomaly ground state Jπ=1/2+. Thus, we compared the theoretical energy levels with the experimental data and the agreements for low excitation states are consistent. The quenching factor is also evaluated and discussed. | |
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| 1013 | The Brillouin zones and band gaps of a two-dimensional phononic crystal with parallelogram lattice structure PDF (1205KB) |
| Cite | HU JiaGuang, XU Wen. The Brillouin zones and band gaps of a two-dimensional phononic crystal with parallelogram lattice structure. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1013-1019. | |
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| We present a detailed theoretical study on the acoustic band structure of two-dimensional (2D) phononic crystal. The 2D phononic crystal with parallelogram lattice structure is considered to be formed by rigid solid rods embedded in air. For the circular rods, some of the extrema of the acoustic bands appear in the usual high-symmetry points and, in contrast, we find that some of them are located in other specific lines. For the case of elliptic rods, our results indicate that it is necessary to study the whole first Brillouin zone to obtain rightly the band structure and corresponding band gaps. Furthermore, we evaluate the first and second band gaps using the plane wave expansion method and find that these gaps can be tuned by adjusting the side lengths ratio R, inclined angle θ and filling fraction F of the parallelogram lattice with circular rods. The results show that the largest value of the first band gap appears at θ=90° and F=0.7854. In contrast, the largest value of the second band gap is at θ=60° and F=0.9068. Our results indicate that the improvement of matching degree between scatterers and lattice pattern, rather than the reduction of structural symmetry, is mainly responsible for the enhancement of the band gaps in the 2D phononic crystal. | |
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| 1020 | Velocity field of wave-induced local fluid flow in double-porosity media PDF (1790KB) |
| Cite | BA Jing, ZHANG Lin, SUN WeiTao, HAO ZhaoBing. Velocity field of wave-induced local fluid flow in double-porosity media. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1020-1030. | |
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| Under the excitation of elastic waves, local fluid flow in a complex porous medium is a major cause for wave dispersion and attenuation. When the local fluid flow process is simulated with wave propagation equations in the double-porosity medium, two porous skeletons are usually assumed, namely, host and inclusions. Of them, the volume ratio of inclusion skeletons is low. All previous studies have ignored the consideration of local fluid flow velocity field in inclusions, and therefore they can not completely describe the physical process of local flow oscillation and should not be applied to the situation where the fluid kinetic energy in inclusions cannot be neglected. In this paper, we analyze the local fluid flow velocity fields inside and outside the inclusion, rewrite the kinetic energy function and dissipation function based on the double-porosity medium model containing spherical inclusions, and derive the reformulated Biot-Rayleigh (BR) equations of elastic wave propagation based on Hamilton's principle. We present simulation examples with different rock and fluid types. Comparisons between BR equations and reformulated BR equations show that there are significant differences in wave response characteristics. Finally, we compare the reformulated BR equations with the previous theories and experimental data, and the results show that the theoretical results of this paper are correct and effective. | |
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| 1031 | Sound propagation from the shelfbreak to deep water PDF (1669KB) |
| Cite | QIN JiXing, ZHANG RenHe, LUO WenYu, PENG ZhaoHui, LIU JianJun, WANG DeJun. Sound propagation from the shelfbreak to deep water. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1031-1037. | |
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| Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at shallower depths, we study sound propagation from the transitional area (shelfbreak) to deep water. Numerical simulations with different source depths are first performed, from which we reach the following conclusions. When the source is located near the sea surface, sound will be strongly attenuated by bottom losses in a range-independent oceanic environment, whereas it can propagate to a very long range because of the continental slope. When the source is mounted on the bottom in shallow water, acoustic energy will be trapped near the sound channel axis, and it converges more evidently than the case where the source is located near the sea surface. Then, numerical simulations with different source ranges are performed. By comparing the relative energy level in the vertical direction between the numerical simulations and the experimental data, the range of the air-gun source can be approximated. | |
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| 1038 | Plasmonic-enhanced two-photon fluorescence with single gold nanoshell PDF (1179KB) |
| Cite | ZHANG TianYue, LU GuoWei, SHEN HongMing, Perriat P, Martini M, Tillement O, GONG QiHuang. Plasmonic-enhanced two-photon fluorescence with single gold nanoshell. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1038-1045. | |
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| Single gold nanoshell with mutilpolar plasmon resonances is proposed to enhance two-photon fluorescence efficiently. The single emitter single nanoshell configuration is studied systematically by employing the finite-difference time-domain method. The emitter located inside or outside the nanoshell at various positions leads to a significantly different enhancement effect. The fluorescent emitter placed outside the nanoshell can achieve large fluorescence intensity given that both the position and orientation of the emission dipole are optimally controlled. In contrast, for the case of the emitter placed inside the nanoshell, it can experience substantial two-photon fluorescence enhancement without strict requirements upon the position and dipole orientations. Metallic nanoshell encapsulating many fluorescent emitters should be a promising nanocomposite configuration for bright two-photon fluorescence label. The results provide a comprehensive understanding about the plasmonic-enhanced two-photon fluorescence behaviors, and the nanocomposite configuration has great potential for optical detecting, imaging and sensing in biological applications. | |
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| 1046 | Deformation study of bicrystalline and nano-polycrystalline structures using phase field crystal method PDF (21118KB) |
| Cite | LONG Jian, ZHANG Shuai, ZHAO YuLong, LONG QingHua, YANG Tao, CHEN Zheng. Deformation study of bicrystalline and nano-polycrystalline structures using phase field crystal method. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1046-1056. | |
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| Deformation behaviors of bicrystalline and nano-polycrystalline structures of various tilt angles and inclination angles in two dimensions are investigated in detail using a two-mode phase field crystal model. The interaction between grain boundary (GB) and dislocation is also examined in bicrystals and nano-polycrystals that both contain asymmetric and symmetric tilt GBs, with energy analysis being carried out to analyze these processes. During deformation simulations, we assume the volume of each simulation cell at every time step is coincident with that of the initial state just before deformation. Our simulation results show that the behaviors of symmetric and asymmetric GBs in bicrystals and nano-polycrystals differ from each other depending on tilt angle and inclination angle. A new dislocation emission mechanism of interest is observed in bicrystals which contain low angle symmetric tilt GBs. Low angle GB has a higher mobility relative to high angle GB in both bicrystalline and nano-poly-crystalline structures, as does asymmetric GB to symmetric GB. The generation, motion, pileup and annihilation of dislocations, grain rotation and grain coalescence are observed, which is consistent with the simulation results obtained by molecular dynamics. These simulation results can provide strong guidelines for experimentation. | |
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| 1057 | Spin filtering magnetic modulation and spin-polarization switching in hybrid ferromagnet/semiconductor structures PDF (725KB) |
| Cite | XU HuaiZhe, WANG LiYing, YAN QiQi, ZHANG YaPing, ZHANG ShiChao. Spin filtering magnetic modulation and spin-polarization switching in hybrid ferromagnet/semiconductor structures. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1057-1062. | |
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| Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device. The dependencies of electron spin-polarization on the strip's magnetization strength, width and position have been systematically investigated. A novel magnetic control spin-polarization switch is proposed by inserting a ferromagnetic metal (FM) strip eccentric in relation to off the center of the spin filter, which produces the first energy level spin-polarization reversal. It is believed to be of significant importance for the realization of semiconductor spintronics multiple-value logic devices. | |
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| 1063 | Modulation of Fano resonances in symmetry-broken gold-SiO2-gold nanotube dimers PDF (758KB) |
| Cite | WU DaJian, YU HaiQun, JIANG ShuMin, WU XueWei, LIU XiaoJun. Modulation of Fano resonances in symmetry-broken gold-SiO2-gold nanotube dimers. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1063-1067. | |
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| Fano resonances in the symmetry-broken gold-SiO2-gold (BGSG) nanotubes and the associated dimers have been investigated based on the finite element method. In the BGSG nanotube, the symmetry breaking induced the interactions of the inner gold core and outer gold nanoshell plasmons of all multipolar orders and hence the red-shifts of the plasmon resonance modes and the enhanced quadrupole mode peaks were observed. The interference of the quadrupole mode peak with the subradiant dipole mode caused a Fano-dip in the scattering spectrum. By increasing the core offset-value in the BGSG nanotube, the Fano dip with low energy showed a red-shift and became deeper. Unexpectedly the plasmon coupling between a GSG nanotube and a BGSG nanotube can lead to two strong Fano dips in the scattering spectra of the dimer. It was further noted that the thin side of the BGSG nanotube located at two sides of the dimer gap can lead to the strong near-field coupling between two BGSG nanotubes and hence a deeper and broader Fano dip. | |
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| 1068 | Wave dispersion and attenuation in viscoelastic isotropic media containing multiphase flow and its application PDF (926KB) |
| Cite | YANG Lei, YANG DingHui, NIE JianXin. Wave dispersion and attenuation in viscoelastic isotropic media containing multiphase flow and its application. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1068-1077. | |
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| In this paper, we introduce the complex modulus to express the viscoelasticity of a medium. According to the correspondence principle, the Biot-Squirt (BISQ) equations in the steady-state case are presented for the space-frequency domain described by solid displacements and fluid pressure in a homogeneous viscoelastic medium. The effective bulk modulus of a multiphase flow is computed by the Voigt formula, and the characteristic squirt-flow length is revised for the gas-included case. We then build a viscoelastic BISQ model containing a multiphase flow. Through using this model, wave dispersion and attenuation are studied in a medium with low porosity and low permeability. Furthermore, this model is applied to observed interwell seismic data. Analysis of these data reveals that the viscoelastic parameter tand is not a constant. Thus, we present a linear frequency-dependent function in the interwell seismic frequency range to express tand. This improves the fit between the observed data and theoretical results. | |
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| 1078 | Elastic stress fields caused by a dislocation in GexSi1-x/Si film-substrate system PDF (2619KB) |
| Cite | WANG HuYi, YU Yong, YAN ShunPing. Elastic stress fields caused by a dislocation in GexSi1-x/Si film-substrate system. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1078-1089. | |
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| The elastic stress fields caused by a dislocation in GexSi1-x epitaxial layer on Si substrate are investigated in this work. Based on the previous results in an anisotropic bimaterial system, the image method is further developed to determine the stress field of a dislocation in the film-substrate system under coupled condition. The film-substrate system is firstly transformed into a bimaterial system by distributing image dislocation densities on the position of the free surface. Then, the unknown image dislocation densities are solved by using boundary conditions, i.e., traction free conditions on the free surface. Numerical simulation focuses on the Ge0.1Si0.9/Si film-substrate system. The effects of layer thickness, position of the dislocation and crystallographic orientation on the stress fields are discussed. Results reveal that both the stresses σxx, σxz at the free surface and the stress σxy, σyy, σyz on the interface are influenced by the layer thickness, but the former is stronger. In contrast to the weak dependence of stress field on the crystallographic orientation the stress field was strongly affected by dislocation position. The stress fields both in the film-substrate system and bimaterial system are plotted. | |
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| 1090 | Fuel-optimal trajectory design using solar electric propulsion under power constraints and performance degradation PDF (1417KB) |
| Cite | ZHANG Peng, LI JunFeng, GONG ShengPing. Fuel-optimal trajectory design using solar electric propulsion under power constraints and performance degradation. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1090-1097. | |
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| The fuel-optimal transfer trajectories using solar electric propulsion are designed considering the power constraints and solar array performance degradation. Three different performance degradation models including linear, positive and negative ex-ponential degradations are used in the analysis of three typical rendezvous missions including Apophis, Venus and Ceres, respectively. The optimal control problem is formulated using the calculus of variations and Pontryagin's maximum principle, which leads to a bang-bang control that is solved by indirect method combined with a homotopic technique. In demonstrating the effects of the power constraints and solar array performance degradation on the power budget and fuel consumption, the time histories of the power profile and the fuel consumptions are compared for the three missions. This study indicates that it is necessary to consider the power constraints and solar array performance degradation for the SEP-based low-thrust trajectory design, espacially for long-duration outbound flights. | |
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| 1098 | Multi-pulse homoclinic orbits and chaotic dynamics of a parametrically excited nonlinear nano-oscillator with coupled cubic nonlinearities PDF (3491KB) |
| Cite | ZHANG Wei, HUANG YuTong, YAO MingHui. Multi-pulse homoclinic orbits and chaotic dynamics of a parametrically excited nonlinear nano-oscillator with coupled cubic nonlinearities. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1098-1110. | |
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| In this paper, the complicated dynamics and multi-pulse homoclinic orbits of a two-degree-of-freedom parametrically excited nonlinear nano-oscillator with coupled cubic nonlinearities are studied. The damping, parametrical excitation and the nonlinearities are regarded as weak. The averaged equation depicting the fast and slow dynamics is derived through the method of multiple scales. The dynamics near the resonance band is revealed by doing a singular perturbation analysis and combining the extended Melnikov method. We are able to determine the criterion for the existence of the multi-pulse homoclinic orbits which can form the Shilnikov orbits and give rise to chaos. At last, numerical results are also given to illustrate the nonlinear behaviors and chaotic motions in the nonlinear nano-oscillator. | |
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| 1111 | A high-efficiency aerothermoelastic analysis method PDF (2262KB) |
| Cite | WAN ZhiQiang, WANG YaoKun, LIU YunZhen, YANG Chao. A high-efficiency aerothermoelastic analysis method. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1111-1118. | |
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| In this paper, a high-efficiency aerothermoelastic analysis method based on unified hypersonic lifting surface theory is established. The method adopts a two-way coupling form that couples the structure, aerodynamic force, and aerodynamic thermo and heat conduction. The aerodynamic force is first calculated based on unified hypersonic lifting surface theory, and then the Eckert reference temperature method is used to solve the temperature field, where the transient heat conduction is solved using Fourier's law, and the modal method is used for the aeroelastic correction. Finally, flutter is analyzed based on the p-k method. The aerothermoelastic behavior of a typical hypersonic low-aspect ratio wing is then analyzed, and the results indicate the following: (1) the combined effects of the aerodynamic load and thermal load both deform the wing, which would increase if the flexibility, size, and flight time of the hypersonic aircraft increase; (2) the effect of heat accumulation should be noted, and therefore, the trajectory parameters should be considered in the design of hypersonic flight vehicles to avoid hazardous conditions, such as flutter. | |
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| 1119 | Investigation of the unstable flow phenomenon in a pump turbine PDF (2024KB) |
| Cite | YIN JunLian, WANG DeZhong, WALTERS D. Keith, WEI XianZhu. Investigation of the unstable flow phenomenon in a pump turbine. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1119-1127. | |
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| Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes. For investigating this phenomenon, a numerical model based on the dynamic sliding mesh method (DSSM) is presented and used to numerically solve the 3D transient flow which is characterized by the variable rotation speed of runner. The method is validated by comparison with measured data for a load rejection process in a prototype pump turbine. The results show that the calculated rotation speed agrees well with the experimental data. Based on the validated model, simulations were performed for the runaway process using an artificially assumed operating condition under which the unstable rotation speed is expected to appear. The results confirm that the instability of runner rotational speed can be effectively captured with the proposed method. Presented results include the time history profiles of unit flow rate and unit rotating speed. The internal flow characteristics in a typical unstable period are discussed in detail and the mechanism of the unstable hydraulic phenomenon is explained. Overall, the results suggest that the method presented here can be a viable alternative to predict the dynamic characteristics of pump turbines during transient processes. | |
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| 1128 | Large-eddy simulation of the generation and propagation of internal solitary waves PDF (3005KB) |
| Cite | ZHU Hai, WANG LingLing, TANG HongWu. Large-eddy simulation of the generation and propagation of internal solitary waves. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1128-1136. | |
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| A modified large-eddy simulation model, the dynamic coherent eddy model (DCEM) is employed to simulate the generation and propagation of internal solitary waves (ISWs) of both depression and elevation type, with wave amplitudes ranging from small, medium to large scales. The simulation results agree well with the existing experimental data. The generation process of ISWs is successfully captured by the DCEM method. Shear instabilities and diapycnal mixing in the initial wave generation phase are observed. The dissipation rate is not equal at different locations of an ISW. ISW-induced velocity field is analyzed in the present study. The structure of the bottom boundary layer (BBL) of internal wave packets is found to be different from that of a single ISW. A reverse boundary jet instead of a separation bubble exists behind the leading internal wave while separation bubbles appear in other parts of the wave-induced velocity field. The boundary jet flow resulting from the adverse pressure gradients has distinctive dynamics compared with free shear jets. | |
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| 1137 | Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera PDF (1345KB) |
| Cite | ZHANG Yang, WANG Yuan, JIA Pan. Measuring the kinetic parameters of saltating sand grains using a high-speed digital camera. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1137-1143. | |
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| A high-speed digital camera is used to record the saltation of three sand samples (diameter range: 300-500, 200-300 and 100-125 μm). This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains. The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport. Moreover, the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory, and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air. | |
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| 1144 | Study on the dynamic characteristics of flow over building cluster at high Reynolds number by large eddy simulation PDF (7735KB) |
| Cite | WANG BoBin, WANG ZhiShi, CUI GuiXiang, ZHANG ZhaoShun. Study on the dynamic characteristics of flow over building cluster at high Reynolds number by large eddy simulation. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1144-1159. | |
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| In this paper, the dynamic characteristics of building clusters are simulated by large eddy simulation at high Reynolds number for both homogeneous and heterogeneous building clusters. To save the computational cost a channel-like flow model is applied to the urban canopy with free slip condition at the upper boundary. The results show that the domain height is an important parameter for correct evaluation of the dynamic characteristics. The domain height must be greater than 8h (h is the average building height) in order to obtain correct roughness height while displacement height and roughness sublayer are less sensitive to the domain height. The Reynolds number effects on the dynamic characteristics and flow patterns are investigated. The turbulence intensity is stronger inside building cluster at high Reynolds number while turbulence intensity is almost unchanged with Reynolds number above the building cluster. Roughness height increases monotonously with Reynolds number by 20% from Re*=103 to Re*=105 but displacement height is almost unchanged. Within the canopy layer of heterogeneous building clusters, flow structures vary between buildings and turbulence is more active at high Reynolds number. | |
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| 1160 | Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed PDF (2211KB) |
| Cite | ZHANG Xin, HUANG Yong, WANG WanBo, WANG XunNian, LI HuaXing. Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1160-1168. | |
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| The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle (UAV) at high wind speeds. The plasma actuator was based on Dielectric Barrier Discharge (DBD) and operated in a steady manner. The flow over a wing of UAV was performed with smoke flow visualization in the Φ0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized. A full model of the UAV was experimentally investigated in the Φ3.2 m low speed wind tunnel using a six-component internal strain gauge balance. The effects of the key parameters, including the locations of the plasma actuators, the applied voltage amplitude and the operating frequency, were obtained. The whole test model was made of aluminium and acted as a cathode of the actuator. The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds. It was found that the maximum lift coefficient of the UAV was increased by 2.5% and the lift/drag ratio was increased by about 80% at the wind speed of 100 m/s. The control mechanism of the plasma actuator at the test configuration was also analyzed. | |
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| 1169 | Lagrangian coherent structures analysis of gas-liquid flow in a bubble column PDF (6183KB) |
| Cite | WU Qin, WANG GuoYu, HUANG Biao, Bai ZeYu. Lagrangian coherent structures analysis of gas-liquid flow in a bubble column. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1169-1177. | |
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| The objective of this paper is to apply a new identifying method to investigating the gas-liquid two-phase flow behaviors in a bubble column with air injected into water. In the numerical simulations, the standard k-ε turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Finite-Time Lyapunov Exponent (FTLE) and Lagrangian Coherent Structures (LCS) are applied to analyze the vortex structures in multiphase flow. Reasonable agreements are obtained between the numerical and experimental data. The numerical results show that the evolution of gas-liquid in the column includes initial and periodical developing stages. During the initial stage, the bubble hose is forming and extending along the vertical direction with the vortex structures formed symmetrically. During the periodical developing stage, the bubble hose starts to oscillate periodically, and the vortexes move along the bubble hose to the bottom of column alternately. Compared to the Euler-system-based identification criterion of a vortex, the FTLE field presents the boundary of a vortex without any threshold defined and the LCS represents the divergence extent of infinite neighboring particles. During the initial stage, the interfaces between the forward and backward flows are highlighted by the LCS. As for the periodical developing stage, the LCS curls near the vortex centers, providing a method of analyzing a flow field from a dynamical system perspective. | |
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| 1178 | Competition of the multiple Görtler modes in hypersonic boundary layer flows PDF (1167KB) |
| Cite | REN Jie, FU Song. Competition of the multiple Görtler modes in hypersonic boundary layer flows. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1178-1193. | |
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| Competition of multiple Görtler modes in hypersonic boundary layer flows are investigated with the local and marching methods. The wall-layer mode (mode W) and the trapped-layer mode (mode T) both occur in the compressible boundary layer where there exists a temperature adjustment layer near the upper edge. The mode T has the largest growth rate at a lower Görtler number while the mode W dominates at larger Görtler numbers. These two modes are both responsible for the flow transition in the hypersonic flows especially when Görtler number is in the high value range in which the crossover of these two modes takes place. Such high Görtler numbers are virtually far beyond the neutral regime. The nonparallel base flows, therefore, cease to influence the stability behavior of the Görtler modes. The effects of the Mach number on the multiple Görtler modes are studied within a chosen Mach number of 0.95, 2, 4 and 6. When the flow Mach number is sufficiently large, e.g.,Ma≥q4, the growth rate crossover of the mode T and mode W occurs both in the conventional G-β map as well as on the route downstream for a fixed wavelength disturbance. Four particular regions (Region T, T-W, W-T and W) around the crossover point are highlighted with the marching analysis and the result matches that of the local analysis. The initial disturbance of a normal mode maintains the shape in its corresponding dominating region while a shape-transformation occurs outside this region. | |
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| 1194 | On the non-synchronous rotation of binary systems PDF (596KB) |
| Cite | LI ZhiXiong, HUANG RunQian, WANG ShuMin. On the non-synchronous rotation of binary systems. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1194-1200. | |
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| During the evolution of the binary system, many physical processes occur, which can influence the orbital angular velocity and the spin angular velocities of the two components, and influence the non-synchronous or synchronous rotation of the system. These processes include the transfer of masses and angular momentums between the component stars, the loss of mass and angular momentum via stellar winds, and the deformation of the structure of component stars. A study of these processes indicates that they are closely related to the combined effects of tide and rotation. This means, to study the synchronous or non-synchronous rotation of binary systems, one has to consider the contributions of different physical processes simultaneously, instead of the tidal effect alone. A way to know whether the rotation of a binary system is synchronous or non-synchronous is to calculate the orbital angular velocity and the spin angular velocities of the component stars. If all of these angular velocities are equal, the rotation of the system is synchronous. If not, the rotation of the system is non-synchronous. For this aim, a series of equations are developed to calculate the orbital and spin angular velocities. The evolutionary calculation of a binary system with masses of 10M⊙+6M⊙ shows that the transfer of masses and angular momentums between the two components, and the deformation of the components structure in the semidetached or in the contact phase can change the rotation of the system from synchronous into non-synchronous rotation. | |
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| 1201 | Investigating the abundance enrichment pattern of heavy elements in the only observed CEMP-r/s star J004441.04-732136.4 of the SMC PDF (108KB) |
| Cite | CUI WenYuan, ZHANG Bo, ZHAO Gang. Investigating the abundance enrichment pattern of heavy elements in the only observed CEMP-r/s star J004441.04-732136.4 of the SMC. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1201-1205. | |
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| The post-AGB star J004441 is the first and the only one CEMP-r/s star found in SMC. Herein, we investigate the observed abundance pattern of the heavy elements using our parametric model. A consistent fitting results was obtained for the sample star. Based on the low r=0.08, the s-process nucleosynthesis occurred in the interior is supposed to belong to the single neutron-exposure event. The median value of τ0=0.44(T9/0.348)1/2 mbarn-1 supports a higher efficiency of the s-process nucleosynthesis relative to J004441 than that of the solar system, however, the value is not sufficiently high to favor the formation of a lead star. Thus, J004441 does not belong to lead star group. The large Cs value of J004441 supports the intrinsic characteristic of the s-enrichment. The Cr value is similar with that found in halo CEMP-r/s stars, which indicates that the r-process contributions is critical during heavy element enrichment. This star has a metallicity of [Fe/H]=-1.34, which is larger than that of Galaxy halo CEMP-r/s stars. The reason may be because of the different history of metallicity enrichment between the SMC and the Galaxy halo. | |
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| 1206 | Double-peaked decay of transient photovoltage in nanoporous ZnO/n-Si photodetector PDF (787KB) |
| Cite | LIU Hao, FU Cheng, ZHAO Kun. Double-peaked decay of transient photovoltage in nanoporous ZnO/n-Si photodetector. SCIENCE CHINA Physics, Mechanics & Astronomy, 2014, 57 (6): 1206-1208. | |
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| In the present work, a nanoporous ZnO/n-Si structure has been proposed as a new type infrared photodetector. Triggered by one laser pulse with wavelength of 1064 nm, this structure exhibits a double-peak decay of transient photovoltage. Also, the time interval between these two peaks increases linearly with the increase of irradiated pulsed energy, indicating the promising application of this hetero-junction in photo-energy detection of infrared pulsed laser. A possible mechanism for this particular photoresponse has been discussed. | |
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