AbstractThe local atomic structure in aluminium monatomic metallic glass is studied using molecular dynamics simulations combined with the embedded atom method (EAM). We have used a variety of analytical methods to characterise the atomic configurations of our system: the Pair Distribution Function (PDF), the Common Neighbour Analysis (CNA) and the Voronoi Tessellation Analysis. CNA was used to investigate the order change from liquid to amorphous phases, recognising that the amount of icosahedral clusters increases with the decrease of temperature. The Voronoi analysis revealed that the icosahedral-like polyhedral are the predominant ones. It has been observed that the PDF function shows a splitting in the second peak, which cannot be attributed to the only ideal icosahedral polyhedron 〈0, 0, 12, 0〉, but also to the formation of other Voronoi polyhedra 〈0, 1, 10, 2〉 . Further, the PDFs were then integrated giving the cumulative coordination number in order to compute the fractal dimension (df). 相似文献
There are two symmetry-independent formula units of the title compound, dimethyl 3-benzyl-2-(4-methyl-2,5-dioxoimidazolidin-1-yl)butanedioate, C17H20N2O6, per cell. The two symmetry-independent molecules differ in their configuration and are diastereomers. This structural study confirms a new side reaction during the synthesis of seven-membered cyclopeptides. The stereochemistry of both diastereomers has been established. 相似文献
Coupled laminar natural convection with radiation in air-filled square enclosure heated from below and cooled from above is
studied numerically for a wide variety of radiative boundary conditions at the sidewalls. A numerical model based on the finite
difference method was used for the solution of mass, momentum and energy equations. The surface-to-surface method was used
to calculate the radiative heat transfer. Simulations were performed for two values of the emissivities of the active and
insulated walls (ɛ1=0.05 or 0.85, ɛ2=0.05 or 0.85) and Rayleigh numbers ranging from 103 to 2.3×106 . The influence of those parameters on the flow and temperature patterns and heat transfer rates are analyzed and discussed
for different steady-state solutions. The existing ranges of these solutions are reported for the four different cases considered.
It is founded that, for a fixed Ra, the global heat transfer across the enclosure depends only on the magnitude of the emissivity
of the active walls. The oscillatory behavior, characterizing the unsteady-state solutions during the transitions from bicellular
flows to the unicellular flow are observed and discussed. 相似文献
We have used the real-space Migdal-Kadanoff renormalization group technique on d-dimensional hypercubic lattice to study the mixed spin-1/2 and spin-2 Blume-Capel model. First, we indicate a critical dimension dC ≈?2.05, above and below which different topologies of phase diagrams occur. The phase diagrams have been plotted in the (crystal field, temperature) plane around dC, in which there is a second-order phase transition. Moreover, using the variation of the free energy at low temperatures, we have established the ground-state phase diagrams in the (?/J, C/J) plane for d?<?dC and d?≥?dC. In particular, we have seen the appearance of two first-order transitions at very low temperatures by the use of the free energy and its isotherm derivative. A detailed analysis of fixed points and flow diagrams indicates that there is no tricritical point.
Condensation of N‐p‐nitrophenyl‐C‐ethoxycarbonylnitrilimine with 2‐methylthio‐4‐phenyl‐3H‐1,5‐benzodiazepine leads to the title compound, C26H23N5O4S. It has been established that 1,3‐dipolar cycloaddition occurs on the C4 =N5 double bond of the 1,5‐benzodiazepine. 相似文献
Fluid flow and heat and mass transfer induced by double-diffusive natural convection in a horizontal porous layer subjected
to vertical gradients of temperature and concentration are studied analytically and numerically using the Brinkman-extended
Darcy model. Both cases of rigid and free horizontal boundaries are examined in the present study. The parameters governing
the problem are the Rayleigh number RT, the Lewis number Le, the buoyancy ratio N, the Darcy number Da and the aspect ratio Ar. The analytical solution is based on the parallel flow approximation. The critical
Rayleigh number corresponding to the onset of the parallel flow in this system is determined analytically as a function of
Le, N and Da. For sufficiently small Da, both free and rigid boundaries yield results which are identical to those predicted by
the Darcy model. The present investigation shows that there exists a region in the plane (N, Le) where the convective flow is not possible in the layer regardless of the Rayleigh and Darcy numbers considered.
Received on 21 December 1998 相似文献
The synthesis of25-[2-(ethoxy-1-p-toluene-sulfonate)phenyl]-26,27,28-trihydroxy calix[4]arene3 as a byproduct of the preparation of 1,3-dialkylated25,27-di-[2-(ethoxy-1p-toluene-sulfonate)phenyl]-26,28-dihydroxy calix[4]arene 2 is reported. Compound 3 is a monoalkylatedcalix[4]arene in the cone conformation. The X-ray structure of 3 showed that this conformation is stabilized by intramolecular hydrogen bonding. 相似文献
The natural convection heat transfer in inclined rectangular enclosures with perfectly conducting fins attached to the heated wall is numerically studied. The parameters governing this problem are the Rayleigh number (102≤Ra≤2×105), the aspect ratio of the enclosures (2.5≤A=H′/L′≤∞), the dimensionless lengths of the partitions (0≤B=?′/L′≤1), the aspect ratio of micro-cavities (A≤C=h′/L′≤0.33), the inclination angle (0≤φ≤60°) and the Prandtl number (Pr=0.72). The results indicate that the heat transfer through the cover is considerably affected by the presence of the fins. At low Rayleigh numbers, the heat transfer regime is dominated by conduction. When B≈0.75 and C≈0.33, the heat transfer through the cold wall decreases considerably. This trend is enhanced when the enclosure is inclined. Useful engineering correlations are derived for practical applications. 相似文献
The crystal structure of calix[4]biscrown-7, 1, (C52H68O14), (triclinic,space group P1, Z = 2, a = 11.115 (5), b = 11.710 (5), c = 18.990 (7)Å, = 85.12 (4), = 93.11 (5), = 91.01 (5)4°,V = 2458.9 Å3, Rw = 0.0737 for 4170 observed, I 3 (I),reflections) has been determined. It is suggested that the polyether loopswith a radius of ca. 2.1 Å are too shallow to efficiently complex theCs+ cation (radius = 1.69 Å). 相似文献