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1.
The function and physical mechanism of heat flow and the viscous stress in the velocity distribution function expanded by
Maxwellian distribution are presented. With the introduction of effective temperature T
f
, incoherent scatter spectra from plasma for electromagnetic wave in arbitrary line of sight are given. The effect of asymmetry
and anisotropy provided by heat flow and the viscous stress on power spectra is discussed. Radar spectra are calculated for
different cases of electric field, direction, collision frequency and temperature. The effect of heat flow and the viscous
stress on inversion results is analyzed. With a large electric field, the character of non-Maxwellian must be considered.
Supported by the National Natural Science Foundation of China (Grant No. 40310223) 相似文献
2.
The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to
20 GPa. The calculation finds a pressure-induced softening of the transverse acoustic phonon mode and the mode frequency reaching
zero at about 14 GPa, which indicate breaking of the symmetry and formation of a new phase under high pressure.
Supported by the National Natural Science Foundation of China (Grant No. 50771090), the State Key Program for Basic Research
of China (Grant No. 2005CB724404) and the Program for Changjiang Scholars and Innovative Team (Grant No. IRT0650) 相似文献
3.
Zhang ZhenBin Wang JianZhong Qi JinGang Wang Bing He LiJia Cang DaQiang 《中国科学E辑(英文版)》2008,51(3):302-307
Based on the electric dipole theory, the coupled field distribution of pulse electric field (PEF) with electric dipole field
around the cluster in superheated molten alloy is simulated under the effect of PEF. For the difference of electro-migration,
the atom of solute and solution will accumulate around the cluster, and then the smaller cluster may reorganize and grow up
under the action of the coupled field. We also apply the electrostatic induction theory to analyze the bearing behavior of
the half side of the cluster. The bigger the cluster is, the stronger the electrostatic force is, therefore, the bigger cluster’s
stability is weak apparently. The study indicates that the cluster in the superheated molten has the homogeneous tendency
under the effect of PEF.
Supported jointly by the National Natural Science Foundation of China (Grant No. 50674054), and the College Key Laboratory
Open Fund of Liaoning Province (Grant No. 200516203) 相似文献
4.
JinBin Cao JunYing Yang ShiGan Yuan XuHui Shen YuanMo Liu ChunXiao Yan WenZhen Li Tao Chen 《中国科学E辑(英文版)》2009,52(7):2112-2118
Using the data from STAFF/TC-1, this paper for the first time analyzes the electromagnetic interferences of Chinese scientific
satellite. The electromagnetic interference of satellite exists mainly below 30 Hz, but can extend to 190 Hz with an obviously
decreasing power spectral density. The electromagnetic interferences at frequencies below 190 Hz have good correlation with
the solar aspect angle. The electromagnetic interferences at frequencies between 190 and 830 Hz have also correlation with
solar aspect angle. However, the electromagnetic interferences at frequencies above 830 Hz have no correlation with the solar
aspect angle. The correlation coefficient between solar aspect angel and electromagnetic interferences is around 0.90. The
larger the solar aspect angle, the stronger the satellite electromagnetic interference. When the solar aspect angle increases
from 90.6° to 93.6°, the electromagnetic interferences at frequencies <10 Hz increase by 8 times and those at frequencies
190–830 Hz increase by 60%. This close association of electromagnetic interferences with the solar aspect angle indicates
that the solar aspect angle is the main factor to determine the electromagnetic interferences. The electromagnetic interferences
of satellite in sunlight are larger than those in eclipse. The electromagnetic interference produced by solar panel occupies
about 87% in the low frequency band (<100 Hz) and 94% in the high frequency band (>100 Hz) of the total electromagnetic interference
produced by satellite. These in flight observations of electromagnetic radiation of satellites will be very helpful to the
designs of future satellites of space sciences or earthquake sciences.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2008AA12A216), the
National Science & Technology Supporting Program during the Eleventh Five-Year Plan, the National Natural Science Foundation
of China (Grant No. 40523006), the National Basic Research Program of China (“973” Project) (Grant No. 2006CB806305), and
the Specialized Research Fund for State Key Laboratories 相似文献
5.
The mechanical oscillatory behaviors of multiwall carbon nanotube oscillators in gaseous environment are investigated using
the molecular dynamics method. The effects of ambient gas and temperature on intertube frictional force and oscillation frequency
are analyzed. It is found that the intertube frictional force increases with the ambient gas density and temperature. Higher
gas density and higher temperature cause a more rapid decay in the oscillation amplitude and an increase of the oscillation
frequency. Compared to the vacuum environmental condition, the collision between gas atoms and the nanotube walls is a main
ingredient leading to the increase of the energy dissipation. Gas damping may be the main reason for the failure of carbon
nanotube oscillators working in gas environment. The ambient temperature also has an important effect on oscillations and
low temperature is advantageous to sustain oscillations.
Supported by the National Basic Research Program of China (“973”) (Grant No. 2006CB300404), the National Natural Science Foundation
of China (Grant Nos. 50676019, 50775017), the Jiangsu Province Natural Science Foundation (Grant Nos. BK2006510, BK2007113),
and the Research Funding for the Doctor Program from Chinese Educational Ministry (Grant No. 20050286019) 相似文献
6.
With the rapid development of functional magnetic resonance imaging (fMRI) technology, the spatial resolution of fMRI data
is continuously growing. This provides us the possibility to detect the fine-scale patterns of brain activities. The established
univariate and multivariate methods to analyze fMRI data mostly focus on detecting the activation blobs without considering
the distributed fine-scale patterns within the blobs. To improve the sensitivity of the activation detection, in this paper,
multivariate statistical method and univariate statistical method are combined to discover the fine-grained activity patterns.
For one voxel in the brain, a local homogenous region is constructed. Then, time courses from the local homogenous region
are integrated with multivariate statistical method. Univariate statistical method is finally used to construct the interests
of statistic for that voxel. The approach has explicitly taken into account the structures of both activity patterns and existing
noise of local brain regions. Therefore, it could highlight the fine-scale activity patterns of the local regions. Experiments
with simulated and real fMRI data demonstrate that the proposed method dramatically increases the sensitivity of detection
of fine-scale brain activity patterns which contain the subtle information about experimental conditions.
Supported by Chair Professors of Changjiang Scholars Program and CAS Hundred Talents Program, National Program on Key Basic
Research Projects (Grant No. 2006CB705700), National High-Tech R&D Program of China (Grant No.2006AA04Z216), National Key
Technology R&D Program (Grant No. 2006BAH02A25), Joint Research Fund for Overseas Chinese Young Scholars (Grant No.30528027),
National Natural Science Foundation of China (Grant Nos.30600151, 30500131 and 60532050), and Natural Science Foundation of
Beijing (Grant Nos. 4051002 and 4071003) 相似文献
7.
Yue XinAn Wan WeiXing Liu LiBo Ning BaiQi Zhao BiQiang Zhang ManLian 《中国科学E辑(英文版)》2008,51(3):308-322
The TIME-IGGCAS (Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences)
has been developed recently on the basis of previous works. To test its validity, we have made comparisons of model results
with other typical empirical ionospheric models (IRI, NeQuick-ITUR, and TItheridge temperature models) and multi-observations
(GPS, Ionosondes, Topex, DMSP, FORMOSAT, and CHAMP) in this paper. Several conclusions are obtained from our comparisons.
The modeled electron density and electron and ion temperatures are quantitatively in good agreement with those of empirical
models and observations. TIME-IGGCAS can model the electron density variations versus several factors such as local time,
latitude, and season very well and can reproduce most anomalistic features of ionosphere including equatorial anomaly, winter
anomaly, and semiannual anomaly. These results imply a good base for the development of ionospheric data assimilation model
in the future. TIME-IGGCAS underestimates electron temperature and overestimates ion temperature in comparison with either
empirical models or observations. The model results have relatively large deviations near sunrise time and sunset time and
at the low altitudes. These results give us a reference to improve the model and enhance its performance in the future.
Supported by the KIP Pilot Project of CAS (Grant No. kzcx2-yw-123), National Natural Science Foundation of China (Grant Nos.
40636032 and 40725014), and National Key Basic Research Project of China (Grant No. 2006CB806306) 相似文献
8.
Based on the empirical electron theory of solids and molecules (EET), the phase valence electron structure parameters of Al-22%Si
alloy are calculated, and the sensitivity of the bond network of Al-Si alloy melt to temperature (energy) and the effect of
the sensitivity on the morphology are studied. The results show that the Si-Si clusters with larger n
A in the slightly superheated Al-Si alloy melt supply the nucleation core to the primary silicon phase in the hypereutectic
Al-22%Si alloy, and strongly generate the drag-like effect for the Al-Si clusters around them; that the variation of temperature
significantly affects the stability of bonds of the core so that the solidified structure is changed; that the electric pulse
applied to the alloy melt can irrecoverably alter the stability of Si-Si clusters, then the modification of the solidified
structure morphology of alloys is generated; that the higher the energy of the electric pulse, the less stable the Si-Si clusters,
and the more significant the electric pulse modification.
Supported by the National Natural Science Foundation of China (Grant No. 50674054), and the College Key Laboratory Open Fund
of Liaoning Province(Grant No. 200516203) 相似文献
9.
In this paper, we propose a method to simulate the three-line rail traffic. The aim is to evaluate the carrying capacity of
the three-line rail traffic by studying the rail traffic flow when the passenger flow is unsymmetrical. The simulation results
demonstrate that under the unsymmetrical condition, the three-line rail traffic system has almost the same carrying capacity
as that of a four-line rail traffic system. Compared with the four-line rail traffic system, the three-line rail traffic system
has better utilization of rail line. As a result, building the three-line rail traffic system is a more economical and rational
selection.
Supported by the National Basic Research Program of China (Grant No. 2006CB705500), the Changjiang Scholars and Innovative
Research Team in University (Grant No. IRT0605), the National Natural Science Foundation of China (Grant No. 60634010), New
Century Excellent Talents in University (Grant No. NCET-06-0074), and the Key Project of Chinese Ministry of Education (Grant
No. 107007) 相似文献
10.
Risk assessment method of major unsafe hydroelectric project 总被引:4,自引:3,他引:1
Based on the characteristics of major unsafe hydroelectric projects and the data from field detection, in situ monitoring,
and regular safety inspection, the fundamental principles of operation risk assessment are proposed in this paper. Meanwhile,
a three layer hierarchical system is constructed, and an improved analytical hierarchical process combining genetic algorithm
and analytical hierarchical process is established, with corresponding program. The operation risk of some unsafe dam was
assessed with the principles, method and program presented in this paper and the major factors which would affect the operation
of the dam were pointed out.
Supported by Key Project of NNSF and Yalongjiang Hydroelectric Development Joint Research Fund (Grant No. 50539110), Science
and Technology Support Plan (Grant No. 20006BAC14B03), National Natural Science Foundation Major Project (Grant Nos. 50539010,
50539030) and National Natural Science Foundation of China (Grant No. 50579010) 相似文献
11.
The development of Hydro-Informatic Modelling System (HIMS) provides an integrated platform for hydrological simulation. To
extend the application of HIMS, an ecohydrological modeling system named ecohydrological assessment tool (EcoHAT) has been
developed. Integrating parameter-management tools, RS (remote sensing) inversion tools, module-design tools and GIS analysis
tools, the EcoHAT provides an integrated tool to simulate ecohydrological processes on regional scale, which develops a new
method on sustainable use of water. EcoHAT has been applied to several case studies, such as, the Yellow River Basin, the
acid deposition area in Guizhou province and the riparian catchment of Guanting reservoir in Beijing. Results prove that EcoHAT
can efficiently simulate and analysis the ecohydrological processes on regional scale and provide technical support to integrated
water resources management on basin scale.
Supported by the National Key Technology R&D Program in the 11th Five-year Plan of China (Grant No. 2006BAB06B07), the National
Natural Science Foundation of China (Grant No. 40671123), the National Basic Research Program of China (“973” Project) (Grant
Nos. 2005CB422207, G19990436), and the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No.
2006AA12Z145) 相似文献
12.
Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins (trusses) into a foam matrix to create
a truss-like network reinforced foam core. Upon loading, the pins deform predominantly by local stretching whilst the deformation
of foam is governed by local bending. This paper presents a theoretical study on the thermoelasticity of pin-reinforced foam
sandwich cores. To calculate the effective thermoelastic properties of pin-reinforced foam cores, the energy-based homogenization
approach is employed to develop a micromechanicsbased model, calibrated by the existing experimental data. It is found that
the stiffness of the sandwich core is mainly governed by pin reinforcements: the foam matrix contributes little to sandwich
stiffness. Compared with traditional foam cores without pin reinforcements, the changes in in-plane thermal expansion coefficients
are not vigorous as a result of pin reinforcements, while the throughthickness thermal expansion coefficient changes significantly.
It is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under
such a context.
Supported by the National Basic Research Program of China (Grant No. 2006CB601202), the National Natural Science Foundation
of China (Grant Nos. 10572111, 10632060), the National 111 Project of China (Grant No. B06024), the National High Technology
Research Development Program (Grant No. 2006AA03Z519), the NPU Foundation for Fundamental Research, the Open Foundation of
State Key Laboratory of Structural Analysis of Industrial Equipment (Grant No. GZ0701), and the NPU Foundation for Scientific
Innovation 相似文献
13.
The understanding of hydrological cycle is the core of hydrology and the scientific base of water resources management. Meanwhile,
simulation of hydrological cycle has long been regarded as an important tool for the assessment, utilization and protection
of water resources. In this paper, a new tool named Hydro-Informatic Modelling System (HIMS) has been developed and introduced
with case studies in the Yellow River Basin in China and 331 catchments in Australia. The case studies showed that HIMS can
be employed as an integrated platform for hydrological simulation in different regions. HIMS is a modular based framework
of hydrological model designed for different utilization such as flood forecasting, water resources planning and evaluating
hydrological impacts of climate change and human activities. The unique of HIMS is its flexibility in providing alternative
modules in the simulation of hydrological cycle, which successfully overcome the difficulties in the availability of input
data, the uncertainty of parameters, and the difference of rainfall-runoff processes. The modular based structure of HIMS
makes it possible for developing new hydrological models by the users.
Supported by the National Natural Science Foundation of China (Grant No. 40671031), National Key Basic Research Development
Program of China (Grant Nos. G1999043601 and 2006CB403407) and National Key Technology R&D Program (Grant No. 2006BAB06N07) 相似文献
14.
HuiMin Xie ZhenXing Hu FuLong Dai YanJie Li PengWan Chen QingMing Zhang FengLei Huang 《中国科学E辑(英文版)》2009,52(7):2048-2053
This paper proposes a new method that reconstructs the information of specimen by using random phase shift step in digital
holographic microscopy (DHM). The principles of the method are described and discussed in detail. In practical experiment,
because the phase shifter is neither perfectly linear nor calibrated, digital holograms with inaccurate phase shift step are
recorded by the charge-coupled device (CCD). The phase could be accurately reconstructed from the recorded digital holograms
by using the random phase-shifting algorithm, which makes up for reconstructed phase error caused by ordinary phase-shifting
algorithm. The phase aberration compensation is also discussed. In order to verify the flexibility of the proposed method,
numerical simulation of random phase-shifting DHM was carried out. The simulation results illustrated that the presented method
is effective when the phase shift step is unknown or random in DHM.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2004CB619304), the National Natural Science
Foundation of China (Grant Nos. 10625209, 10472050, 10732080), the Project of Beijing Natural Sciences Foundation (Grant No.
3072007), the Program for New Century Excellent Talents (NCET) in Chinese University Ministry of Education (Grant No. NCET-05-0059),
and the Opening Funds from the State Key Laboratory of Explosion Science and Technology 相似文献
15.
High performance 1.3 μm InGaAsN superluminescent diodes (SLDs) were fabricated with Schottky contact. The structure was grown by metal organic chemical vapor deposition (MOCVD). Output power of 3 mW was obtained in continuous wave (CW) mode at room temperature. The full width at half maximum (FWHM) of the emission spectrum was 30 nm. The devices operated up to 100℃. 相似文献
16.
Flexible, large area electronics using various organic and inorganic materials are beginning to show great promise. During
manufacture and service, large deformation of these hybrid materials will pose significant challenges in terms of high performance
and reliability. A deep understanding of the ductility or flexibility of macroelectronics becomes one of the major issues
that must be addressed urgently. This paper describes the current level of understanding on the thin-film ductility, both
free-standing and substrate-supported, and relevant influencing factors.
Supported by the National Basic Research Program of China (Grant No. 2004CB619303), the 111 Project of China (Grant No. B06025),
and the Science and Technology Key Project from Ministry of Education of China (Grant Nos. 02182, 03182) 相似文献
17.
Reconstruction of a continuous time signal from its periodic nonuniform samples and multi-channel samples is fundamental for
multi-channel parallel A/D and MIMO systems. In this paper, with a filterbank interpretation of sampling schemes, the efficient
interpolation and reconstruction methods for periodic nonuniform sampling and multi-channel sampling in the fractional Fourier
domain are presented. Firstly, the interpolation and sampling identities in the fractional Fourier domain are derived by the
properties of the fractional Fourier transform. Then, the particularly efficient filterbank implementations for the periodic
nonuniform sampling and the multi-channel sampling in the fractional Fourier domain are introduced. At last, the relationship
between the multi-channel sampling and the filterbank in the fractional Fourier domain is investigated, which shows that any
perfect reconstruction filterbank can lead to new sampling and reconstruction strategies.
Supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104), the National
Natural Science Foundation of China (Grant Nos. 60890072, 60572094) and the National Key Basic Research Program Founded by
MOST (Grant No. 2009CB724003) 相似文献
18.
Based on the empirical electron theory of solids and molecules (EET), the statistical values of valence electron structure
parameters Sn
A and SE
A which can characterize the properties of alloy phases are calculated, and influences of alloying elements (e.g., V, Nb, Mo,
Hf, Zr, Fe, Mn, Co, Cr, Si, and so on) on the phase transition temperature and eutectoid reaction of titanium alloy are discussed
with the statistical values of valence electron structure parameters. The research results agree well with real situations.
Supported by the National Natural Science Foundation of China (Grant No. 50471022, 50741004) and National Key Basic Research
Program of China (“973”) (Grant No. 2007CB613807) 相似文献
19.
A macro-micro dual-drive positioning system showing good potential for high acceleration and high precision positioning required
in IC packaging applications is devised in this paper. The dual-drive positioning stage uses a VCM (voice coil motor) driven
macro positioning stage and a PZT piezo-electric driven micro positioning stage. The coupling characteristics of the system
are analyzed to produce a control structure with a micro positioning stage that can dynamically compensate for the positioning
error produced by the macro positioning stage. Models of the two positioning stages are described. The models cover both the
mechanism and the actuator. For the macro positioning stage, friction characteristics are taken into account, and a controller
with an LQG (linear-quadratic-Gaussian) control algorithm combining a feed-forward compensation algorithm is derived. A PID
controller is used to control the micro positioning stage. Detailed designs are derived for the proposed approach, and the
performance is validated by simulation.
Supported by the National Natural Science Foundation of China (Grant No. 50705027), the National High Technology Research
and Development Program of China (“863” Program) (Grant No. 2007AA04Z315) and Self-Planned Task of State Key Laboratory of
Robotics and System (HIT) (Grant No. SKLRS200804B) 相似文献
20.
Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of
bridge wind engineering, and the structural health monitoring system (SHMS) employed in many long-span bridges provide a research
basis for the field measurement. In order to provide reliable basis for wind resistant evaluation of Runyang Suspension Bridge
(RSB), two anemometers and 85 accelerometers were installed in the SHMS of RSB. In August 2005, Typhoon Matsa crossed over
Jiangsu, the SHMS timely recorded the typhoon and structural vibration responses. In this paper by using the time-frequency
technique and statistical theory, the recorded data were analyzed to obtain the strong wind characteristics, the buffeting
response characteristics of the cable and deck, and the variation of buffeting response RMS versus wind speed. Results obtained
in this study can be employed to validate the credibility of current buffeting response analysis theory techniques, and provide
reference values for wind resistant evaluation of other long-span bridges.
Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA04Z416), the
Key Project of the National Natural Science Foundation of China (Grant No. 50538020) and the Outstanding Youth Fund of the
National Natural Science Foundation of China (Grant No. 50725828) 相似文献