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1.
Analysis of the forces acting on the saltating particles in the coupled wind-sand-electricity fields
Based on the theoretical model describing the saltation of sand particles in the coupled wind-sand-electricity fields, the
numerical simulations of the forces acting on saltating particles, such as the aerodynamic drag force, Magnus effect, Saffman
force and electrostatic force, are analyzed in comparison to the gravity force of the particles in the steady windblown sand
movement. Furthermore, the laws of the above forces vary with the friction velocity, the diameter of the sand particle, the
initial angular velocity and the lift-off velocity are discussed.
Supported by the National Natural Science Foundation of China (Grant Nos. 10772075 and 10772074), the Key Project of the National
Natural Science Foundation of China (Grant No.10532040), and the Program for New Century Excellent Talents in University (Grant
No. NCET-04-0979) 相似文献
2.
The dust emission models to date cannot describe the relation between the transport rate of different sized grains and their
grain size composition in soil surface, so Aeolian grain transport on a soil-like bed composed of fine sand and silt powder
was measured in a wind tunnel. Six types of soil-like beds with different silt fractions have been tested in this experiment.
The mass flux profiles of silt dust and sand grains are much different due to their different motion modes. Analysis of the
vertical distribution of the powder and sand grains reveals that for a given soil bed, the ratio of the horizontal dust flux
to the horizontal sand flux is directly proportional to their mass ratio in the bed. The dust flux is closely linked to the
sand flux by the bombardment mechanism. For a given wind velocity and grain size of the bed, the slopes of the vertical mass
flux profiles of sand grains larger than 100 μm are nearly equal in a log-linear plot and the ratio between the fraction of
transport rate of each size group to the whole transport rate and the mass fraction of each size group in the bed is a constant
only dependent on grain size. With this law, the transport rate of dust and different sized grains can be related with the
grain size composition in the soil surface.
Supported by the National Natural Science Foundation of China (Grant No. 50706031) and the Natural Science Foundation of Shanxi
Province of China (Grant No. 2008021005) 相似文献
3.
DPTM simulation of aeolian sand ripple 总被引:1,自引:1,他引:1
Aeolian sand ripple and its time evolution are simulated by the discrete particle tracing method (DPTM) presented in this
paper. The difference between this method and the current methods is that the former can consider the three main factors relevant
to the formation of natural aeolian sand ripples, which are the wind-blown sand flux above the sand bed formed by lots of
sand particles with different diameters, the particle-bed collision and after it the rebound and ejection of sand particles
in the sand bed, the saltation of high-speed sand particles and the creep of low-speed sand particles, respectively. The simulated
aeolian sand ripple is close to the natural sand ripple not only in basic shape and characteristic, particle size segregation
and stratigraphy, but also in formation stages. In addition, three important speeds can be obtained by this method, which
are the propagation speed of the saturated aeolian sand ripple and the critical frictional wind speeds of emergence and disappearance
of sand ripple.
Supported by the Key Project of the National Natural Science Foundation of China (Grant No. 10532040) 相似文献
4.
In a wind-blown sand layer, it has been found that wind transport of
particles is always associated with separation of electric charge. This
electrification in turn produces some electrostatic forces in addition to
the gravitational and fluid friction forces that affect the movement of
saltating sand particles, further, the wind-blown sand saltation. To
evaluate this effect quantitatively, this paper presents a simulation of
evolution of wind-blown sand grains after the electrostatic forces exerted
on the grains are taken into account in the wind feedback mechanism of
wind-blown saltation. That is, the coupling interaction between the wind
flow and the saltating sand particles is employed in the simulation to the
non-stationary wind and sand flows when considering fluid drag, gravitation,
and a kind of electrostatic force generated from a distribution of electric
field changing with time in the evolution process of the sand saltation. On
the basis of the proposed simulation model, a numerical program is given to
perform the simulation of this dynamic process and some characteristic
quantities, e.g., duration of the system to reach the steady state, and
curves of the saltating grain number, grain transport rate, mass-flux
profile, and wind profile varying with time during the non-stationary
evolution are displayed. The obtained numerical results exhibit that the
electrostatic force is closely related to the average charge-to-mass ratio
of sand particles and has obvious influence on these characteristic
quantities. The obtained results also show that the duration of the system
to reach the steady state, the sand transport rate and the mass flux profile
coincide well with experimental results by Shao and Raupach (1992) when the
average charge-to-mass ratio of sand particles is 60 μC/kg for the sand
particles with average diameter of 0.25 mm. When the average charge-to-mass
ratios of sand particles are taken as some other certain values, the
calculation results still show that the mass flux profiles are well in
agreement with the experimental data by Rasmussen and Mikkelsen (1998) for
another category of sand particles, which tell us that the electrostatic
force is one of main factors that have to be considered in the research of
mechanism of wind-blown sand saltation. 相似文献
5.
The field of medical photonics is rapidly expanding, and a wide variety of optical technologies and instruments have recently
been developed for diagnostic, therapeutic and basic science applications in medicine. This review presents the recent advances
and application of medical photonics, and the obtained results from our laboratory are highlighted. Finally, the challenges
and future prospects for the transition from technological exploration to clinical studies are discussed.
Supported by the National Natural Science Foundation of China (Grant No. 60678054), the PhD Program Foundation of Ministry
of Education (Grant No. 200803940001), the Key Grants from Ministry of Education (Grant No. 209063), and the Fujian Provincial
Natural Science Foundation (Grant No. 2008J0001) 相似文献
6.
The probability of successful controlled teleportation of an unknown qubit using a general three-particle state is investigated.
The analytic expressions of maximal probabilities via several kinds of tripartite states are given, including a tripartite
Greenberger-Horne-Zeilinger state and a tripartite W-state.
Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology
Research of Ministry of Education of China (Grant No. 207011), and the Natural Science Foundation of Hebei Province, China
(Grant No. 07M006) 相似文献
7.
With the method of large-eddy simulation, the equation of spherule motion and the method of immersed boundary condition, numerical
simulations of three-dimensional turbulent aeolian motion and the formation of sand ripples under three-dimensional turbulent
wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that
is flat on the upwind side and steep on the leeward, which is identical to the sand ripples in nature. We also realized the
self-restoration process of three-dimensional sand ripples, which shows the correctness of the method of numerical simulation
and the models of saltation and creeping. Finally, We analyzed the influence of sand ripples on the three-dimensional turbulent
wind field, and found that due to the appearance and development of sand ripples, in the normal direction of ground there
exists stronger energy exchange, and moreover, there is close correspondence between the forms of sand ripples and the vorticity
close to the ground surface.
Supported by the Key Project of National Natural Science Foundation of China (Grant No. 10532040) 相似文献
8.
Saltation is one of the important transport modes in the movement of wind-blown grains. Its evolution was considered to be
a wind-particle self-regulating process. Recent researches indicate that the particle mid-air collision greatly influences
the sand movement, thus the mid-air collision mechanism may highly contribute to the evolution of wind-sand flow. A theoretical
model is suggested to mathematically describe the evolution of wind-sand flow by considering the exiting wind-particle feedback
mechanism as well as the particle mid-air collision mechanism. Based on this model, the time of the entire process to reach
a steady state, the variation curves of the sand transport rate with time and the mid-air collision probability with time
are calculated. The results show that the mid-air collision mechanism also contributes significantly to the stabilization
of the saltation process. 相似文献
9.
A protocol of quantum secret sharing between multiparty and multiparty with four states was presented. It was shown that this
protocol can nullify the Trojan horse attack with a multi-photon signal, the fake-signal attack with Einstein-Podolsky-Rosen
pairs, the attack with single photons, and the attack with invisible photons. In addition, the upper bounds of the average
success probabilities were given for dishonest agent eavesdropping encryption using the fake-signal attack with any two-particle
entangled states.
Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology
Research of Education Ministry of China (Grant No. 207011) and the Natural Science Foundation of Hebei Province, China (Grant
Nos. A2005000140 and 07M006) 相似文献
10.
The electronic structure of stressed CrSi2 was calculated using the first-principle methods based on plane-wave pseudo-potential theory. The calculated results showed
that, under the uniaxial compression, the energy level of CrSi2 shifted toward high energy and its energy gap became wider with the increasing uniaxial stress, while the gap became narrower
under the negative uniaxial stress. When the negative uniaxial stress was up to −18.5 GPa, CrSi2 was converted into a direct-gap semiconductor with the band gap of 0.32 eV.
Supported by the National Natural Science Foundation of China (Grant No. 60566001), the Specialized Research Fund for the
Doctoral Program of Higher Education of China (Grant No. 20050657003), the Scientific Research Foundation for the Returned
Overseas Chinese Scholars, Ministry of Education of China (Grant No. (2005)383), the Program for the Excellent Young Talents
of Guizhou Province (Grant No. 20050528), the Specialized Nomarch Research Fund for the Excellent Science and Technology and
Education Talent’s Projects of Guizhou Province, Scientific and Technological Projects for the Returned Overseas Chinese Scholars,
the Guizhou Province (Grant No. (2004)03), and the Top Talent’s Scientific Research Project of Organization Department of
Guizhou Province 相似文献
11.
Using the first principle methods based on the plane-wave pseudo-potential theory, band structure, density of states and optical
properties of CrSi2 were studied. The calculation of band structure shows that CrSi2 is an indirect semiconductor whose band gap is 0.353 eV. Density of states is mainly composed of 3d electron of Cr and 3p
electron of Si. Dielectric function, refractive index, reflectivity, and absorption coefficient of CrSi2 are also calculated. The calculation results of optical properties are in agreement with the experiments.
Supported by the National Natural Science Foundation of China (Grant No. 60566001), the Specialized Research Fund for the
Doctoral Program of Higher Education of China (Grant No. 20050657003), the Scientific Research Foundation for the Returned
Overseas Chinese Scholars, Ministry of Education of China (Grant No. (2005)383), the Program for Excellent Young Talents of
Guizhou Province (No. 20050528), the Specialized Nomarch Research Fund for the Excellent Science and Technology and Education
Talent’s Projects of Guizhou Province, the Scientific and Technological Projects for the Returned Overseas Chinese Scholars,
Guizhou Province (Grant No. (2004)03), and the Top Talent’s Scientific Research Project of Organization Department of Guizhou
Province. 相似文献
12.
Previously the perihelion advance in binary system was computed approximately. We will present an exact analytical solution
to nonlinear differential equation of perihelion advance by method of Jacobian elliptic function and the advanced angle between
successive perihelions.
Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars from Ministry of Education,
China (Grant No. [2004]527) and the Natural Science Foundation of Hunan Province, China (Grant No. 06JJ2026) 相似文献
13.
With the discrete element method (DEM), employing the diameter distribution of natural sands sampled from the Tengger Desert,
a mixed-size sand bed was produced and the particle-bed collision was simulated in the mixed-size wind sand movement. In the
simulation, the shear wind velocity, particle diameter, incident velocity and incident angle of the impact sand particle were
given the same values as the experimental results. After the particle-bed collision, we collected all the initial velocities
of rising sand particles, including the liftoff angular velocities, liftoff linear velocities and their horizontal and vertical
components. By the statistical analysis on the velocity sample for each velocity component, its probability density functions
were obtained, and they are the functions of the shear wind velocity. The liftoff velocities and their horizontal and vertical
components are distributed as an exponential density function, while the angular velocities are distributed as a normal density
function.
Supported by the Key Project of the National Natural Science Foundation of China (Grant No. 10532040) 相似文献
14.
Algebraic dynamics approach and algebraic dynamics algorithm for the solution of nonlinear partial differential equations
are applied to the nonlinear advection equation. The results show that the approach is effective for the exact analytical
solution and the algorithm has higher precision than other existing algorithms in numerical computation for the nonlinear
advection equation.
Supported by the National Natural Science Foundation of China (Grant Nos. 90503008 and 10775100), the Doctoral Program Foundation
from the Ministry of Education of China, and the Center of Theoretical Nuclear Physics of HIRFL of China 相似文献
15.
A new concept and its methodology for studying human meridians are presented based on rigorous and scientific observation
on the objective existence of human meridians in view of biomedical optics. According to this methodology, the infrared radiant
characteristics of acupuncture meridians over human body and the optical transport properties of light propagating along the
meridian are reported. This study, thus, confirms the existence of acupuncture meridians, sheds new light on an approach to
investigation of human meridians and offers a new perspective in understanding the potential meridian functions such as energy
and information transfer and physiological regulation.
Supported by the National Key Basic Research Program of China (Grant No. 2006CB504505), the National Natural Science Foundation
of China (Grant Nos. 60578056 and 30572309), the Science Research Foundation of Ministry of Health & United Fujian Provincial
Health and Education Project for Tackling the Key Research of China (Grant No. WKJ2005-2-004), the Young Scientists and Technicians
Innovation Project of Fujian Province (Grant No. 2007F3026), and the Fund from Fujian Normal University (Grant No. 2008100218) 相似文献
16.
By using quantum bang-bang control technique, we studied the suppression of amplitude damping, or energy dissipation, in a
three-level atom in various configurations. We have explicitly given the bang-bang control groups in three different configurations,
and the pulse sequences for these bang-bang control operations.
Supported by the National Natural Science Foundation of China (Grant No. 10547003), the Key Project of Chinese Ministry of
Education (Grant No. 306020) and Chifeng College Scientific Research Fund (Grant No. ZRZD200604) 相似文献
17.
An efficient quantum secure direct communication protocol is presented over the amplitude damping channel. The protocol encodes
logical bits in two-qubit noiseless states, and so it can function over a quantum channel subjected to collective amplitude
damping. The feature of this protocol is that the sender encodes the secret directly on the quantum states, the receiver decodes
the secret by performing determinate measurements, and there is no basis mismatch. The transmission’s safety is ensured by
the nonorthogonality of the noiseless states traveling forward and backward on the quantum channel. Moreover, we construct
the efficient quantum circuits to implement channel encoding and information encoding by means of primitive operations in
quantum computation.
Supported by the National Natural Science Foundation of China (Grant Nos. 60873191 and 60821001), the Specialized Research
Fund for the Doctoral Program of Higher Education (Grant No. 200800131016), the Natural Science Foundation of Beijing (Grant
No. 4072020), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), and
the ISN Open Foundation 相似文献
18.
Phase-averaged waveforms of Reynolds stress in wall turbulence during the burst events of coherent structures 总被引:1,自引:0,他引:1
The time sequence signals of instantaneous longitudinal and normal velocity components at different vertical locations in
the turbulent boundary layer over a smooth flat plate have been finely measured by constant temperature anemometry of model
IFA-300 and X-shaped hot-wire sensor probe in a wind tunnel. The longitudinal and normal velocity components have been decomposed
into multi-scales by wavelet transform. The upward eject and downward sweep motions in a burst process of coherent structure
have been detected by the maximum energy criterion of identifying burst event in wall turbulence through wavelet analysis.
The relationships of phase-averaged waveforms among longitudinal velocity component, normal velocity component and Reynolds
stress component have been studied through a correlation function method. The dynamics course of coherent structures and their
effects on statistical characteristics of turbulent flows are analyzed.
Supported by the National Natural Science Foundation of China (Grant No. 10472081), the Program for New Century Excellent
Talents in Universities of Ministry of Education of China, and Tianjin Science and Technology Development Plan (Grant No.
06TXTJJC13800) 相似文献
19.
Single-bubble sonoluminescence (SBSL) is achieved with strong stability in sulfuric acid solutions. Bubble dynamics and the
SBSL spectroscopy in the sulfuric acid solutions with different concentrations are studied with phase-locked integral stroboscopic
photography method and a spectrograph, respectively. The experimental results are compared with those in water. The SBSL in
sulfuric acid is brighter than that in water. One of the most important reasons for that is the larger viscosity of sulfuric
acid, which results in the larger ambient radius and thus the more contents of luminous material inside the bubble. However,
sonoluminescence bubble’s collapse in sulfuric acid is less violent than that in water, and the corresponding blackbody radiation
temperature of the SBSL in sulfuric acid is lower than that in water.
Supported by the National Natural Science Foundation of China (Grant Nos. 10434070 and 10704037) and the Ministry of Education
Priorities Project of China (Grant No. 103078) 相似文献
20.
CdS/α-Fe2O3 hierarchical nanostructures, where the CdS nanorods grow irregularly on the side surface of α-Fe2O3 nanorods, were synthesized via a three-step process. The diameters and lengths of CdS nanorods can be tuned by changing the
ethylenediamine (EDA) and Cd ion concentrations. The magnetic investigations by superconducting quantum interference device
indicate that the hierarchical nanostructures have an Morin transition at lower temperature (230 K) than that of the single
bulk α-Fe2O3 materials (263 K). Importantly, the hierarchical nanostructures exhibit weakly ferromagnetic characteristics at 300 K. A
sharp peak assigned to the surface trap induced emission are observed in room temperature PL spectra. Combining with the optoelectronic
properties of CdS, the CdS/α-Fe2O3 hierarchical nanostructures may be used as multi-functional materials for optoelectronic and magnetic devices.
Supported by the National Natural Science Foundation of China (Grant Nos. 50772025 and 50872159), the Ministry of Science
and Technology of China (Grant No. 2008DFR20420), the China Postdoctoral Science Foundation (Grant Nos. 20060400042 and 200801044),
the Natural Science Foundation of Heilongjiang Province, China (Grant No. F200828), the Specialized Research Fund for the
Doctoral Program of Higher Education of China (Grant No. 20070217002), and the Innovation Foundation of Harbin City (Grant
No. RC2006QN017016) 相似文献