共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Esen A. T. Tüzemen M. Ozdemir 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(4):117
We study the equilibration of an initial surface of conic shape that consists of concentric circular monolayers by Kinetic
Monte Carlo (KMC) method. The kinetic processes of attachment and/or detachment of particles to/from steps, diffusion of particles
on the surface, along a step or cluster edges are considered. The difference between an up hill and down hill motion of a
particle at a step are taken into account through the Ehrlich-Schwoebel (ES) barrier. The height of the cone evolves as h(0) − h(t) ~ t
1/α
where h(0) is the initial height of the surface and α is approximately 2. The ES barrier slows down the equilibration of the surface but the time dependence remains as given above.
The exponent α depends neither on ES barrier nor on the temperature. The equilibration is found also to be independent of energy barrier
to the motion of particles along the step edges. The number of particles in each layer except the top two circular layers
is found to decrease as t
0.57. 相似文献
2.
The substantial drop of the plasma temperature along magnetic field lines with increasing plasma density is one of the main features in tokamak divertors. As a result the temperature gradient at the divertor plates becomes very steep and the boundary condition normally applied for the parallel Mach number M at the target, Mt = 1, cannot be satisfied. In this case the value of Mt based on the general form of the Bohm criterion, Mt 1, has to be determined from the continuity of plasma parameters.In the present paper a new approach to resolve the Mach number at the target for such a situation is proposed. This method avoids the singularity problem that arises by treating the particle balance and parallel motion equations in a differential form. Instead, the integral representation of the equations is formulated for an arbitrary form of particle and momentum sources. The approach can also take into account transport perpendicular to the magnetic field lines.The proposed method is demonstrated on the example of a one-dimensional stationary model for the scrape-off layer (SOL) plasma and includes the continuity-, parallel momentum- and heat transfer equations. The recycled neutrals are described in the diffusion approximation. In the case of low density the normal condition Mt = 1 is satisfied and the results are in agreement with the two-point model. At high enough plasma density solutions with the supersonic flow at the divertor plates, Mt > 1, are found. These states correspond to a partially detached plasma with a temperature of a few eV. 相似文献
3.
M. Carvajal F. Willaert J. Demaison I. Kleiner 《Journal of Molecular Spectroscopy》2007,246(2):158-166
We have reinvestigated the laboratory spectrum for the methylformate HCOOCH3 molecule involving both the ground and first excited torsional states.We have fitted within almost experimental accuracy a data set for this molecule consisting of 3496 vt=0 and 774 vt=1 microwave lines, using the so-called “rho axis method” (RAM) and a model extended to include perturbation terms through eighth order. The previously published microwave lines covering the J values up to 43 in the ground state and up to 18 in the first excited state have been extended by 434 new measurements from Lille in the 567–669 GHz spectral range, corresponding to transitions with Jmax=62, Kmax=22 in vt=0. The final fit requires only 49 parameters to achieve a unitless weighted standard deviation of 1.43 for a total of 4270 lines for the whole fit. This result represents an improvement over the previous fit which achieved a standard deviation of 1.96 for 3862 lines using 69 parameters. A calculation of the line strengths of torsion–rotation transitions up to J = 60 needed for the astronomical survey is also provided. 相似文献
4.
Maria Jarzyńska 《Central European Journal of Physics》2007,5(4):586-598
The research problem presented in this work concerns modification of the Kedem-Katchalsky (K-K) equation for volume flow (J
v
) through system (h|M|l), consisting of a membrane M and boundary layers h and l. Such boundary layers appear in the vicinity of the membrane on both sides due to the lack of mixing of solutions. This paper
also includes the derivation of the equation for volume flow (J
vr
) dissipated on concentration boundary layers h and l. The derivation of these equations concerns the case in which the substance transport through the membrane is generated by
the osmotic pressure gradient
. On the basis of the equations for the volume flows (J
v
) and (J
vr
), some calculations for a nephrophane membrane, used in medicine, and for aqueous glucose solutions have been carried out.
In order to test the equations for (J
v
) and (J
vr
), we have also carried out calculations for the volume flow (J′
v
) that is transferred through the membrane in the case of mixed solutions on both sides of the membrane. This volume flux
has been calculated on the basis of the original (K-K) equation. The results are presented in Fig. 2.
相似文献
5.
This paper is concerned with the asymptotic behavior solutions of stochastic differential equations dy
t
=dω
t
−∇Γ(y
t
) dt, y
0=0 and d=2. Γ is a 2 &\times; 2 skew-symmetric matrix associated to a shear flow characterized by an infinite number of spatial scales
Γ12=−Γ21=h(x
1), with h(x
1)=∑
n
=0
∞γ
n
h
n
(x
1/R
n
), where h
n
are smooth functions of period 1, h
n
(0)=0, γ
n
and
R
n
grow exponentially fast with n. We can show that y
t
has an anomalous fast behavior (?[|y
t
|2]∼t
1+ν with ν > 0) and obtain quantitative estimates on the anomaly using and developing the tools of homogenization.
Received: 1 June 2001 / Accepted: 11 January 2002 相似文献
6.
Wen-Xin Qin 《Communications in Mathematical Physics》2012,311(2):513-538
In this paper we are mainly concerned with existence and modulation of uniform sliding states for particle chains with damping
γ and external driving force F. If the on-site potential vanishes, then for each F > 0 there exist trivial uniform sliding states x
n
(t) = n
ω + ν
t + α for which the particles are uniformly spaced with spacing ω > 0, the sliding velocity of each particle is ν = F/γ, and the phase α is arbitrary. If the particle chain with convex interaction potential is placed in a periodic on-site potential,
we show under some conditions the existence of modulated uniform sliding states of the form
xn(t)=nw+nt+a+u(nw+nt+a),x_n(t)=n\omega+\nu t+\alpha+u(n\omega+\nu t+\alpha), 相似文献
7.
Christopher D. Thompson Evan G. Robertson Ivana Aleksic Don McNaughton 《Journal of Molecular Spectroscopy》2005,230(2):81
The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm−1. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν4 (1200.7341 cm−1) and ν13 (1223.3 cm−1) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν4 (Jmax = 86, Ka max = 50) and 2921 lines to ν13 (Jmax = 60, Ka max = 54). Effective rotational and centrifugal distortion constants were determined for ν4, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν13 band. 相似文献
8.
R.M. Lees Reba-Jean Murphy Adriana Predoi-Cross D.R.T. Appadoo R.R.J. Goulding 《Journal of Molecular Spectroscopy》2009,256(1):91-98
The high-resolution Fourier transform spectrum of the ν8 CO-stretching band of CH318OH between 900 and 1100 cm−1 has been recorded at the Canadian Light Source (CLS) synchrotron facility in Saskatoon, and the majority of the torsion-rotation structure has been analyzed. For the νt = 0 torsional ground state, subbands have been identified for K values from 0 to 11 for A and E torsional symmetries up to J values typically well over 30. For νt = 1, A and E subbands have been assigned up to K = 7, and several νt = 2 subbands have also been identified. Upper-state term values determined from the assigned transitions using the Ritz program have been fitted to J(J + 1) power-series expansions to obtain substate origins and sets of state-specific parameters giving a compact representation of the substate J-dependence. The νt = 0 subband origins have been fitted to effective molecular constants for the excited CO-stretching state and a torsional barrier of 377.49(32) cm−1 is found, representing a 0.89% increase over the ground-state value. The vibrational energy for the CO-stretch state was found to be 1007.49(7) cm−1. A number of subband-wide and J-localized perturbations have been seen in the spectrum, arising both from anharmonic and Coriolis interactions, and several of the interacting states have been identified. 相似文献
9.
We obtain an asymptotic expansion for the solution of the Cauchy problem for the Korteweg-de Vries (KdV) equation
10.
Consider a general strictly hyperbolic, quasilinear system, in one space dimesion
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