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Hot Paper More»   
Estimation of lunar titanium content: Based on absorption features of Chang’E-1 interference imaging spectrometer (IIM)
LIU FuJiang, QIAO Le, LIU Zheng, YANG Rong, SHI JinPing, ZHANG Ying & WU WeiLong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2136-2144
Origin of pit chains in the floor of lunar Copernican craters
XIAO ZhiYong, ZENG ZuoXun, XIAO Long, FA WenZhe & HUANG Qian
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2145-2159
Global absorption center map of the mafic minerals on the Moon as viewed by CE-1 IIM data
WU YunZhao, ZHANG Xia, YAN BoKun, GAN FuPing, TANG ZeSheng, XU AoAo, ZHENG YongChun & ZOU YongLiao
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2160-2171
Preparation of genuine Yeo-Chua entangled state and teleportation of two-atom state via cavity QED
ZHANG Wen, LIU YiMin, ZUO XueQin & ZHANG ZhanJun
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2232-2237
 
 
SCIENCE CHINA Physics, Mechanics & Astronomy
2010, Vol. 53, No. 12
Online Publication Date: 01 December 2010


 
   
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Preface | Astrometry

Preface: Joint researches are benefiting the Chang’E-1 comprehensive lunar scientific studies which probe ever deeper

PING JinSong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2135-2135 | doi:10.1007/s11433-010-4178-8
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Payloads of the first Chinese lunar mission Chang’E-1 obtained fruitful scientific data which cover a wide range of disciplines and fields. From 2007, many domestic research teams have been working hard on calibrating and validating these data cautiously and carefully. They have made out a lot of outstanding presentations and publications in various scientific meetings and journals. Recently, these Chinese lunar science pioneers found many more deep research results by means of collaborations between/among teams, by combining the data from the new lunar missions.

Research Papers | Astrometry

Estimation of lunar titanium content: Based on absorption features of Chang’E-1 interference imaging spectrometer (IIM) Hot!

LIU FuJiang, QIAO Le, LIU Zheng, YANG Rong, SHI JinPing, ZHANG Ying & WU WeiLong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2136-2144 | doi:10.1007/s11433-010-4165-0
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Two linear regression models based on absorption features extracted from CE-1 IIM image data are presented to discuss the relationship between absorption features and titanium content. We computed five absorption parameters (Full Wave at Half Maximum (FWHM), absorption position, absorption area, absorption depth and absorption asymmetry) of the spectra collected at Apollo 17 landing sites to build two regression models, one with FWHM and the other without FWHM due to the low relation coefficient between FWHM and Ti content. Finally Ti content measured from Apollo 17 samples and Apollo 16 samples was used to test the accuracy. The results show that the predicted values of the model with FWHM have many singular values and the result of model without FWHM is more stable. The two models are relatively accurate for high-Ti districts, while seem inexact and disable for low-Ti districts.

Show PACS: 93.85.Pq, 95.75.Mn, 96.20.Dt, 07.87.+v, 02.50.Sk
Research Papers | Astrometry

Origin of pit chains in the floor of lunar Copernican craters Hot!

XIAO ZhiYong, ZENG ZuoXun, XIAO Long, FA WenZhe & HUANG Qian
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2145-2159 | doi:10.1007/s11433-010-4174-z
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There are small pit chains in the floor of lunar Copernican craters. They are usually so small in scale that there are few lunar spacecrafts to detect their detailed morphology. Combining camera data from Lunar Orbiter, Lunar Reconnaissance Orbiter (LRO), Kaguya and Chang’e-1 missions, 5 representative large Copernican craters on various terrains of the lunar surface are chosen to study the origin of the pit chains in the crater floor. The morphology and distribution characteristic of the pit chains are referred by the high resolution images in this research. It is suggested that it is the magma activities from the subsurface magma layer combining with the existence of fractures and faults under the crater floor that leaded the formation of the pit chains. The model is further verified and discussed using the regolith thickness data in the crater floor. Our model suggests that the pit chains are still developing in the floor of the Copernican craters and the Moon may not be totally cold. Finally, the model limitation and potential future work are discussed based on available data.

Show PACS: 96.15.Bc, 96.15.Lb, 96.15.Nd, 96.12.Xy
Research Papers | Astrometry

Global absorption center map of the mafic minerals on the Moon as viewed by CE-1 IIM data Hot!

WU YunZhao, ZHANG Xia, YAN BoKun, GAN FuPing, TANG ZeSheng, XU AoAo, ZHENG YongChun & ZOU YongLiao
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2160-2171 | doi:10.1007/s11433-010-4169-9
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Determining the global distribution of minerals on the Moon has been an important goal of lunar science. Hyperspectral remote sensing is an important approach to acquiring minerals on the Moon on the global scale. The wavelength of the absorption band center is the key parameter for identifying minerals with reflectance spectra as well as remote sensing data. The global absorption center map of the mafic minerals of the Moon was produced for the first time with the Chang’E-1 IIM data. This map shows the global distribution of mafic minerals such as orthopyroxenes, clinopyroxenes, and olivine and even plagioclase feldspar of the Moon. The validation for some representative areas indicates that the global map is reliable and even more detailed than the results derived from Clementine-data. Moreover, our method is insensitive to the topography and viewing and illumination geometries. The global absorption band center map not only contributes to the lunar science research, but also has other implications to be further studied. Moreover, the preprocessing methods such as calibration and correction introduced in this study can be useful in other research with IIM data.

Show PACS: 96.12.Ma, 91.60.Mk, 95.55.Pe
Research Papers | Astrometry

Research on water ice content in Cabeus crater using the data from the microwave radiometer onboard Chang’e-1 satellite

MENG ZhiGuo, CHEN ShengBo, Edward Matthew OSEI Jnr, WANG ZiJun & CUI TengFei
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2172-2178 | doi:10.1007/s11433-010-4159-y
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The existence, formation and content of water ice in the lunar permanently shaded region is one of the important questions for the current Moon study. On October 9, 2009, the LCROSS mission spacecraft impacted the Moon, and the initial result verified the existence of water on the Moon. But the study on formation and content of water ice is still under debate. The existence of water ice can change the dielectric constants of the lunar regolith, and a microwave radiometer is most sensitive to the dielectric parameters. Based on this, in this paper, the radiation transfer model is improved according to the simulation results in high frequency. Then the mixture dielectric constant models, including Odelevsky model, Wagner and landau-Lifshitz model, Clau-sius model, Gruggeman-Hanai model, etc., are analyzed and compared. The analyzing results indicate that the biggest difference occurs between Lichtenecker model and the improved Dobson model. The values estimated by refractive model are the second biggest in all the models. And the results from Odelevsky model, strong fluctuation model, Wagner and Landau –Lifshitz model, Clausius model and Bruggeman-Hanai model are very near to each other. Thereafter, the relation between volume water ice content and microwave brightness temperature is constructed with Odelevsky mixing dielectric model and the improved radiative transfer simulation, and the volume water ice content in Cabeus crater is retrieved with the data from microwave radiometer onboard Chang’e-1 satellite. The results present that the improved radiative transfer model is proper for the brightness temperature simulation of the one infinite regolith layer in high frequency. The brightness temperature in Cabeus crater is 69.93 K (37 GHz), and the corresponding volume water ice content is about 2.8%.

Show PACS: 98.70.Sa, 90.50.sb, 13.85.Tp
Research Papers | Astrometry

Geologic investigation and mapping of the Sinus Iridum quadrangle from Clementine, SELENE, and Chang’e-1 data

CHEN ShengBo, MENG ZhiGuo, CUI TengFei, LIAN Yi, WANG JingRan & ZHANG XuQing
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2179-2187 | doi:10.1007/s11433-010-4160-5
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The objectives of lunar satellite remote sensing are to study lunar surface characteristics, inner structure, and its evolution history. The contents of TiO2 and FeO are assessed from Clementine UV/VIS data for Sinus Iridum. The geologic stratigraphic units and crates are interpreted visually based on SELENE Terrain Camera (TC) images and the spatial resolution of which is up to 10 m. And the geologic ages of different stratigraphic units are calculated by the crater size-frequency distributions measurements. The gravity anomaly is generated from SELENE gravity model (SGM90d) to show its difference from Mare Imbrium. Furthermore, the thickness of lunar regolith is also derived from microwave radiometer data of Chang’e-1 satellite. Integrating these results, it shows that the Sinus Iridum is different from the Mare Imbrium in inner structure and surface sedimentation. And its history of subsidence, deposition, volcanism, and impact is described. It makes sense to the future soft-landing and sampling at potential Sinus Iridum by remote sensing geologic analysis.

Show PACS: 95.55.Pe, 95.85.-e, 96.20.Dt, 96.20.Br
Research Papers | Astrometry

Results obtained by geodetic instruments of SELENE (KAGUYA)

KAWANO Nobuyuki, LIU QingHui, PING JinSong, CHEN Ming, VRAD/RSAT Team & LALT Team
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2188-2193 | doi:10.1007/s11433-010-4161-4
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Japanese lunar explorer SELENE (KAGUYA) was equipped with 14 instruments for various measurements of the Moon. Three of these instruments took geodetic measurements of the Moon. These were two sub-satellites and a laser altimeter. The main results obtained by the instruments are: (1) precise orbit determination with an accuracy of ten meters by Doppler and same-beam VLBI; (2) the first precise gravity fields on the lunar far side by 4-way Doppler measurements; (3) the first topography in latitudes higher than 86 degrees; (4) a global map of the gravity anomaly by using the global topography and the global gravity fields; (5) a global map of the lunar crustal thickness and (6) an illumination rate map in the north and south polar regions.

Show PACS: 96.12.Bc, 96.12.Qr, 95.10.Eg, 95.75.De
Research Papers | Theoretical physics

On the fundamental equation of nonequilibrium statistical physics—Nonequilibrium entropy evolution equation and the formula for entropy production rate

XING XiuSan
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2194-2215 | doi:10.1007/s11433-010-4188-6
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In this paper the author presents an overview on his own research works. More than ten years ago, we proposed a new fundamental equation of nonequilibrium statistical physics in place of the present Liouville equation. That is the stochastic velocity type’s Langevin equation in 6N dimensional phase space or its equivalent Liouville diffusion equation. This equation is time-reversed asymmetrical. It shows that the form of motion of particles in statistical thermodynamic systems has the drift-diffusion duality, and the law of motion of statistical thermodynamics is expressed by a superposition of both the law of dynamics and the stochastic velocity and possesses both determinism and probability. Hence it is different from the law of motion of particles in dynamical systems. The stochastic diffusion motion of the particles is the microscopic origin of macroscopic irreversibility. Starting from this fundamental equation the BBGKY diffusion equation hierarchy, the Boltzmann collision diffusion equation, the hydrodynamic equations such as the mass drift-diffusion equation, the Navier-Stokes equation and the thermal conductivity equation have been derived and presented here. What is more important, we first constructed a nonlinear evolution equation of nonequilibrium entropy density in 6N, 6 and 3 dimensional phase space, predicted the existence of entropy diffusion. This entropy evolution equation plays a leading role in nonequilibrium entropy theory, it reveals that the time rate of change of nonequilibrium entropy density originates together from its drift, diffusion and production in space. From this evolution equation, we presented a formula for entropy production rate (i.e. the law of entropy increase) in 6N and 6 dimensional phase space, proved that internal attractive force in nonequilibrium system can result in entropy decrease while internal repulsive force leads to another entropy increase, and derived a common expression for this entropy decrease rate or another entropy increase rate, obtained a theoretical expression for unifying thermodynamic degradation and self-organizing evolution, and revealed that the entropy diffusion mechanism caused the system to approach to equilibrium. As application, we used these entropy formulas in calculating and discussing some actual physical topics in the nonequilibrium and stationary states. All these derivations and results are unified and rigorous from the new fundamental equation without adding any extra new assumption.

Show PACS: 05.10.Gg, 05.20.-y, 05.40.-a, 05.70.Ln
Research Papers | Acoustics

Method of coupled mode for long-range bottom reverberation

GAO Bo, YANG ShiE, PIAO ShengChun & HUANG YiWang
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2216-2222 | doi:10.1007/s11433-010-4162-3
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The theory of coupled mode is used for modeling the long-range bottom reverberation in shallow water caused by bottom roughness. The distant bottom reverberation level and spatial coherence of impulsive source are both derived. The results agree with those from the classical reverberation model, and are compared with the experimental data. The influence of source bandwidth and the distance between sources and receivers on the intensity of bottom reverberation are particularly discussed. The method is shown to be available for both the mono- and the bi-static cases.

Show PACS: 43.30.Bp, 43.30.Gv, 43.30.Hw
Research Papers | Condensed Matter Physics

Electrochemical corrosion and oxidation resistances of Zr60Ni21Al19 bulk amorphous alloys

JING Qin, ZHANG Bing, ZHANG Jin, MA MingZhen & LIU RiPing
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2223-2226 | doi:10.1007/s11433-010-4185-9
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Electrochemical corrosion and oxidation resistances of Zr60Ni21Al19 amorphous alloy were studied. The ternary amorphous alloy exhibits greater positive potential than its crystalline counterpart and 0Cr19Ni9Ti stainless steel. Its weight loss result measured in 2 mol/L HCl solution is in agreement with the potentiodynamic curve. But there is no obvious difference in the oxidation resistances between Zr60Ni21Al19 amorphous and its crystalline alloys. They both exhibit high oxidation resistance.

Show PACS: 61.43.Dq, 82.45.Bb, 81.65.Mq
Research Papers | Quantum Physics

Quantum communications with an anonymous receiver

WANG TianYin, WEN QianYan & ZHU FuChen
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2227-2231 | doi:10.1007/s11433-010-4109-8
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A new protocol for the anonymous communication of quantum information is proposed. The anonymity of the receiver and the privacy of the quantum information are perfectly protected except with exponentially small probability in this protocol. Furthermore, this protocol uses single photons to construct anonymous entanglement instead of multipartite entangled states, and therefore it reduces quantum resources compared with the pioneering work.

Show PACS: 03.67.Hk, 03.67.Dd, 03.67.-a, 03.65.Ud
Research Papers | Quantum Physics

Preparation of genuine Yeo-Chua entangled state and teleportation of two-atom state via cavity QED Hot!

ZHANG Wen, LIU YiMin, ZUO XueQin & ZHANG ZhanJun
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2232-2237 | doi:10.1007/s11433-010-4170-3
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We first propose a scheme for preparing the genuine Yeo-Chua 4-qubit entangled state via cavity QED. Using the genuine Yeo-Chua atomic state, we further propose a cavity QED scheme for teleporting an arbitrary two-atom state. In two schemes the large-detuning is chosen and the necessary time is designed to be much shorter than Rydberg-atom’s lifespan. Both schemes share the distinct advantage that cavity decay and atom decay can be neglected. As for the interaction manipulation, our preparation scheme is more feasible than a recent similar one. Compared with the Yeo and Chua’s scheme, our teleportation scheme has significantly reduced the measuring difficulty.

Show PACS: 03.67.Dd, 03.67.Hk
Research Papers | Quantum Physics

Quantum secret sharing between multiparty and multiparty with Bell states and Bell measurements

SHI RunHua, HUANG LiuSheng, YANG Wei & ZHONG Hong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2238-2244 | doi:10.1007/s11433-010-4181-0
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We present a quantum secret sharing scheme between multiparty (m members in Group 1) and multiparty (n members in Group 2), and analyze its security. This scheme takes EPR pairs in Bell states as quantum resources. In order to obtain the shared key, all members only need to perform Bell measurements, rather than perform any local unitary operation. The total efficiency in this scheme approaches 100% as the classical information exchanged is not necessary except for the eavesdropping checks.

Show PACS: 03.67.Dd, 03.67.Ac
Research Papers | Quantum Physics

Small is beautiful, and dry

ZHENG QuanShui, LV CunJing, HAO PengFei & SHERIDAN John
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2245-2259 | doi:10.1007/s11433-010-4172-1
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Thousands of plant and animal species have been observed to have superhydrophobic surfaces that lead to various novel behaviors. These observations have inspired attempts to create artificial superhydrophobic surfaces, given that such surfaces have multitudinous applications. Superhydrophobicity is an enhanced effect of surface roughness and there are known relationships that correlate surface roughness and superhydrophobicity, based on the underlying physics. However, while these examples demonstrate the level of roughness they tell us little about the independence of this effect in terms of its scale. Thus, they are not capable of explaining why such naturally occurring surfaces commonly have micron-submicron sizes. Here we report on the discovery of a new relation, its physical basis and its experimental verification. The results reveal that scaling-down roughness into the micro-submicron range is a unique and elegant strategy to not only achieve superhydrophobicity but also to increase its stability against environmental disturbances. This new relation takes into account the previously overlooked but key fact that the accumulated line energy arising from the numerous solid-water-air intersections that can be distributed over the apparent contact area, when air packets are trapped at small scales on the surface, can dramatically increase as the roughness scale shrinks. This term can in fact become the dominant contributor to the surface energy and so becomes crucial for accomplishing superhydrophobicity. These findings guide fabrication of stable super water-repellant surfaces.

Show PACS: 47.55.np, 47.55.dr, 68.08.Bc, 68.03.Cd, 87.15.La
Research Papers | Applied Physics

Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement

SHEN ChangLe, XIE WenJun & WEI BingBo
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2260-2265 | doi:10.1007/s11433-010-4125-8
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A type of non-axisymmetric oscillations of acoustically levitated drops is excited by modulating the ultrasound field at proper frequencies. These oscillations are recorded by a high speed camera and analyzed with a digital image processing method. They are demonstrated to be the third mode sectorial oscillations, and their frequencies are found to decrease with the increase of equatorial radius of the drops, which can be described by a modified Rayleigh equation. These oscillations decay exponentially after the cessation of ultrasound field modulation. The decaying rates agree reasonably with Lamb’s prediction. The rotating rate of the drops accompanying the shape oscillations is found to be less than 1.5 rounds per second. The surface tension of aqueous ethanol has been measured according to the modified Rayleigh equation. The results agree well with previous reports, which demonstrates the possible application of this kind of sectorial oscillations in noncontact measurement of liquid surface tension.

Show PACS: 68.03.Cd, 43.25.Uv, 07.05.Pj
Research Papers | Solid Mechanics

A macro-mechanical constitutive model for shape memory polymer

ZHOU Bo, LIU YanJu & LENG JinSong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2266-2273 |
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It is of theoretical and engineering interest to establish a macro-mechanical constitutive model of the shape memory polymer (SMP), which includes the mechanical constitutive equation and the material parameter function, from the viewpoint of practical application. In this paper, a new three-dimensional macro-mechanical constitutive equation, which describes the mechanical behaviors associated with the shape memory effect of SMP, is developed based on solid mechanics and the viscoelasticity theorem. According to the results of the DMA test, a new material parameter function is established to express the relationship of the material parameters and temperature during the glass transition of SMP. The new macro-mechanical constitutive equation and material parameter function are used to numerically simulate the process producing the shape memory effect of SMP, which includes deforming at high temperature, stress freezing, unloading at low temperature and shape recovery. They are also used to investigate and analyze the influences of loading rate and temperature change rate on the thermo-mechanical behaviors of SMP. The numerical results and the comparisons with Zhou’s material parameter function and Tobushi’s mechanical constitutive equation illustrate that the proposed three-dimensional macro-mechanical constitutive model can effectively predict the thermo-mechanical behaviors of SMP under the state of complex stress.

Show PACS: 46.35.+z, 46.05.+b, 46.25.Hf
Research Papers | Solid Mechanics

Investigation on coaxial stability of nano-bearing under two axis-deviation perturbations

YAO Yin & HUANG ZaiXing
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2274-2283 | doi:10.1007/s11433-010-4175-y
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A spatial cylindrical model on nano-bearing constructed by double-walled carbon nano-tube (DWCNT) is established. Two motion equations are advanced to characterize the eccentric and deflective mode of the nano-bearing, respectively. On the basis of these equations, the coaxial stability of the nano-bearing under two axis-deviation perturbations is investigated. A characteristic parameter λ* governing the coaxial stability of the nano-bearing is determined. The influences of the angular velocity, interlayer spacing and axial length of the nano-bearing on the characteristic parameter λ* are analyzed and discussed in detail. It is found that when the angular velocity or interlayer spacing is smaller than a certain critical value, the parameter λ* keeps negative, and the coaxial stability of the nano-bearing is maintained. However, the axial length has very insignificant influence on λ*. In addition, for the two non-coaxial modes, the eccentric mode occurs more easily than the deflective one. The results of this paper provide a further insight into the coaxial stability of nano-bearing via the spatial model.

Show PACS: 62.25.+g, 85.35.Kt, 45.80.+r
Research Papers | Computational Mechanics

A computational investigation on random packings of sphere-spherocylinder mixtures

LU Peng, LI ShuiXiang, ZHAO Jian & MENG LingYi
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2284-2292 | doi:10.1007/s11433-010-4190-z
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Random packings of binary mixtures of spheres and spherocylinders with the same volume and the same diameter were simulated by a sphere assembly model and relaxation algorithm. Simulation results show that, independently of the component volume fraction, the mixture packing density increases and then decreases with the growth of the aspect ratio of spherocylinders, and the packing density reaches its maximum at the aspect ratio of 0.35. With the same volume particles, results show that the dependence of the mixture packing density on the volume fraction of spherocylinders is approximately linear. With the same diameter particles, the relationship between the mixture packing density and component volume fraction is also roughly linear for short spherocylinders, but when the aspect ratio of spherocylinders is greater than 1.6, the curves turn convex which means the packing of the mixture can be denser than either the sphere or spherocylinder packing alone. To validate the sphere assembly model and relaxation algorithm, binary mixtures of spheres and random packings of spherocylinders were also simulated. Simulation results show the packing densities of sphere mixtures agree with previous prediction models and the results of spherocylinders correspond with the simulation results in literature.

Show PACS: 45.10.Na, 45.70.Cc, 81.05.Rm
Research Papers | Astromechanics

Modeling earthquake indexes derived from the earthquake warning system upon the planet earth

LI Yong
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2293-2299 | doi:10.1007/s11433-010-4164-1
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By studying the correlation between historical earthquake data and the distributional characteristics of parameters of solid earth tides in the earthquake epicenter, we are able to design a forecasting function of earthquake probability. We put forward a design method for the Earthquake Warning System. The model could theoretically simulate and be used to predict the probability of strong earthquakes that could occur anywhere at any time. In addition, the system could also conveniently obtain global or partial Modeling Earthquake Indexes to finally combine the precise pointing prediction and forecast of partial indexes. The literature quotes global data values, provided by NEIC, of 1544 M ≥ 6.5 earthquakes. It also gives examples of instantaneous earthquake indexes of the whole world and Taiwan Area on 1st January 2010, UT=0:00 and the average earthquake index near the Taiwan Area. According to the 10-year pointing prediction of strong earthquakes in San Francisco, the literature provides the average earthquake index on 24th June 2015 (± 15 days), in its neighborhood.

Show PACS: 91.10.Tq, 91.30.pd, 96.15.Wx, 91.30.Ab
Research Papers | Astrometry

A virtual reference satellite differential method for relative correction of satellite ephemeris errors

CAI ChengLin, LI XiaoHui & WU HaiTao
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2300-2306 | doi:10.1007/s11433-010-4101-3
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In order to solve the problems that the novel wide area differential method on the satellite clock and ephemeris relative correction (CERC) in the non-geostationary orbit satellite constellation, a virtual reference satellite (VRS) differential principle using relative correction of satellite ephemeris errors is proposed. It is referred to be as the VRS differential principle, and the elaboration is focused on the construction of pseudo-range errors of VRS. Through qualitative analysis, it can be found that the impact of the satellite’s clock and ephemeris errors on positioning can basically be removed and the users’ positioning errors are near zero. Through simulation analysis of the differential performance, it is verified that the differential method is universal in all kinds of satellite navigation systems with geostationary orbit (GEO) constellation, Medium orbit (MEO) constellation or hybrid orbit constellation, and it has insensitivity to abnormal aspects of a satellite ephemeris and clock. Moreover, the real time positioning accuracy of differential users can be maintained within several decimeters after the pseudo-range measurement noise is effectively weakened or eliminated.

Show PACS: 06.30.Bp, 06.30.Ft
Research Papers | Galaxy and Cosmology

Narrow line Seyfert 1 galaxies: where are the broad line regions? Hot!

MAO WeiMing, HU Chen, WANG JianMin, BIANWeiHao, ZHANG Shu & ZHAOGang
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2307-2311 | doi:10.1007/s11433-010-4158-z
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A sample consisting of 211 narrow line Seyfert 1 galaxies (NLS1s) with high quality spectra from the Sloan Digital Sky Survey (SDSS) is selected to explore where broad line regions are in these objects. We find that the Hβ profile can be fitted well by three (narrow, intermediate and broad) Gaussian components, and the FWHM ratios of the broad to the intermediate components hold a constant of 3.0 roughly for the entire sample. If the broad components originate from the region scaled by the well-determined Hβ reverberation mapping relation, we find that the intermediate components originate from the inner edge of the torus, which is scaled by dust K-band reverberation. We find that the IC and the BC are strongly linked dynamically, but the relation of their covering factors is much more relaxed, implying that both regions are clumpy.

Show PACS: 04.70.-s, 98.54.-h, 98.54.Aj
Brief report | Astrometry

Design of a search and rescue terminal based on the dual-mode satellite and CDMA network

ZHAO JunPing, ZHANG Xuan, ZHENG Bing, ZHOU YuBin, SONG Hao, SONG Wei, ZHANG MeiKui, LIU TongZe & ZHOU Li
SCIENCE CHINA Physics, Mechanics & Astronomy, 2010, 53(12): 2312-2314 | doi:10.1007/s11433-010-4177-9
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The current goal is to create a set of portable terminals with GPS/BD2 dual-mode satellite positioning, vital signs monitoring and wireless transmission functions. The terminal depends on an ARM processor to collect and combine data related to vital signs and GPS/BD2 location information, and sends the message to headquarters through the military CDMA network. It integrates multiple functions as a whole. The satellite positioning and wireless transmission capabilities are integrated into the motherboard, and the vital signs sensors used in the form of belts communicate with the board through Bluetooth. It can be adjusted according to the headquarters' instructions. This kind of device is of great practical significance for operations during disaster relief, search and rescue of the wounded in wartime, non-war military operations and other special circumstances.

Show PACS: 07.90.+c
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