Full-potential LMTO study on the electronic structure of heavy-fermion compound LiV2O4

The electronic structure of heavy fermion compound LiV2O4 has been calculated using a self-consistent full-potential LMTO method. The results show that the conduction bands in this com pound are formed from V 3 d states with a bandwidth of 2.5 eV. The symmetric characteristics of con duction bands are of t2g in principle. The energy gap between conduction bands and fully occupied oxygen 2 p bands is 1.9 eV. The band dispersions near Fermi energy display complicated structures.Furthermore, the N(EF) and γcal are 11.1 (states/eV/f. u. ) and 26.7 mJ/mol@ K2 determined numer ically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4 from plain LDA calculations. In addition to the above LDA calculation, we also found a LSDA solution of LiV2O4 that is lower in total energy than that of LDA calculation. Similarly, LSDA + GGA calculation yields almost the identical result as that in LSDA. We conclude that the mechanism responsible for heavy fermion properties in LiV2O4 might be somewhat different from the plain Kondo mechanism in conventional 4 f and 5 f heavy fermion compounds and perhaps the quantum transition might play an adequate role in heavy-fermion behaviors in LiV2O4.     

On K1 and K2 of Algebraic Surfaces

In this paper we study higher Chow groups of smooth, projective surfaces over a field k of characteristic zero, using some new Hodge theoretic methods which we develop for this purpose. In particular we investigate the subgroup of CH ^r+1 (X,r) with r = 1,2 consisting of cycles that are supported over a normal crossing divisor Z on X. In this case, the Hodge theory of the complement forms an interesting variation of mixed Hodge structures in any geometric deformation of the situation. Our main result is a structure theorem in the case where X is a very general hypersurface of degree d in projective 3-space for d sufficiently large and Z is a union of very general hypersurface sections of X. In this case we show that the subgroup of CH ^r+1 (X,r) we consider is generated by obvious cycles only arising from rational functions on X with poles along Z. This can be seen as a generalization of the Noether–Lefschetz theorem for r = 0. In the case r = 1 there is a similar generalization by Müller-Stach, but our result is more precise than it, since it is geometric and not only cohomological. The case r = 2 is entirely new and original in this paper. For small d, we construct some explicit examples for r = 1 and 2 where the corresponding higher Chow groups are indecomposable, i.e. not the image of certain products of lower order groups. In an appendix Alberto Collino constructs even more indecomposable examples in CH ³ (X,2) which move in a one-dimensional family on the surface X.Contribution to appendix.     

Liquid structure of undercooled Cu70Ni30 alloy

Experiments of X-ray diffraction for liquid Cu₇₀Ni₃₀ alloy above and below its liquidus (l 230°C) have been carried out. By the analysis of experimental results, it is discovered that difference between structures of liquid and undercooled Cu₇₀Ni₃₀ alloy is their cluster sizes. The correlation radius of cluster is 1.125 nm and the atom number of cluster is 403 at l 250—l 400°C, and they are 1.3 nm and 704 respectively at the undercooled liquid state (1 200°C). The structure of liquid Cu₇₀Ni₃₀ alloy is fcc short order and its solid structure, fcc, is kept from liquid fcc short order.     

Laminar flamelet modeling of a turbulent CH4/H2/N2 jet diffusion flame using artificial neural networks

The laminar flamelet concept is used in the prediction of mean reactive scalars in a non-premixed turbulent CH₄/H₂/N₂ flame. First, a databank for temperature and species concentrations is developed from the solutions of counter-flow diffusion flames. The effects of flow field on flamelets are considered by using mixture fraction and scalar dissipation rate. Turbulence-chemistry interactions are taken into account by integrating different quantities based on a presumed probability density function (PDF), to calculate the Favre-averaged values of scalars. Flamelet library is then generated. To interpolate in the generated library, one artificial neural network (ANN) is trained where the mean and variance of mixture fraction and the scalar dissipation rate are used as inputs, and species mean mass fractions and temperature are selected as outputs. The weights and biases of this ANN are implemented in a CFD flow solver code, to estimate mean values of the scalars. Results reveal that ANN yields good predictions and the computational time has decreased as compared to numerical integration for the estimation of mean thermo-chemical variables in the CFD code. Predicted thermo-chemical quantities are close to those from experimental measurements but some discrepancies exist, which are mainly due to the assumption of non-unity Lewis number in the calculations.     

Effect of Mg and C contents in MgCNi3, and structure and superconductivity of MgCNi3- x -Co x

The effect of Mg and C contents on T_C in MgCN₃, and structure and superconductivity of MgCNi_3-x Co _x were studied. It is found that the excess of Mg and C in initial material mixture is favorable to improvement inT _c and helps to obtain single-phase samples. For preparing MgCNi₃ superconductor, the optimum composition of starting materials is MgC_1.45Ni₃ with excess of Mg (20 wt.%) of the stoichiometric composition. In gCNi_3-x Co _x system, a continuous solid solution is formed, lattice parameter decreases slightly andT _c decreases obviously with increasingx. A suppression of superconductivity is observed due to the substitution of Co (Mn) for Ni. The suppression effect is smaller for the substitution of Co than that of Mn     

Synchrotron radiation photoemission spectrum study on K3C60 film

K₃C₆₀, single crystal film was prepared on the cleaved (111) surface of C₆₀, single crystal. Synchrotron radiation angle-resolved photoemission spectra were measured at normal emission with sample temperature at × 150K. Up to four subpeaks of LUMO-derived band were observed. These sub-peaks exhibit distinct energy dispersions which resemble in general the theoretical ones calculated for K₃C₆₀ at low temperature with the so-called one-dimensional disordered structure. But there is large deviation of experimental sub-band intervals from the theoretical values. This result is meaningful for the studies of the physical properties of alkali-doped C₆₀ solids, e.g. the mechanism for superconductivity.     

Powers of ideals associated to (C4,2K2)-free graphs

Let G be a $(C_4,2K_2)$-free graph with edge ideal $I(G)?\mathbb{k}[x_1,\dots ,x_n]$. We show that $I{(G)}^s$ has linear resolution for every $s\ge 2$. Also, we show that every power of the vertex cover ideal of G has linear quotients. As a result, we describe the Castelnuovo–Mumford regularity of powers of $I{(G)}^{\vee }$ in terms of the maximum degree of G.     

具有H2引燃的CH4，煤油超声速混合的三维数值研究

用双流体模型和分区算法,气相多组分N－S方程和液相Euler方程分别用迎风TVD格式和NND格式进行数值求解,相间相互作用项方程用二阶Runge-Kutta法求解,并首次对H2引燃的CH4和煤油横向喷射,混合问题进行了数值研究,结果表明：与喷射加碘空气的PLIF结果相比,本文和实验结果符合得很好,对直通道,后面喷嘴的穿透深度大,煤油较气态 穿透深度大,但难以被卷吸到喷嘴前的回流区内,流场出现无煤油区,H2和CH4均可扩散到回流区内,CH4和煤油引燃机理不同,对后台阶直通道,存在两个回流区,H2可扩散到这两个回流区,但CH4只能被卷吸到其喷嘴前的回流区,后台阶直通道增强混合的效果和引燃点火的可靠性更好。     

Approximating term structure of interest rates using cubic L1 splines

Classical spline fitting methods for estimating the term structure of interest rates have been criticized for generating highly fluctuating fitting curves for bond price and discount function. In addition, the performance of these methods usually relies heavily on parameter tuning involving human judgement. To overcome these drawbacks, a recently developed cubic L₁ spline model is proposed for term structure analysis. Cubic L₁ splines preserve the shape of the data, exhibit no extraneous oscillation and have small fitting errors. Cubic L₁ splines are tested using a set of real financial data and compared with the widely used B-splines.     

A conjecture of Abe-Iiyori and the Ree groups 2F4(q), II

In this paper the author has solved a problem of Abe and liyori for the finite simple groups ² F ₄(q) and ² F ₄(2)′.     

On the structure of the K2 of the ring of integers in a number field

For any prime p, the p-primary part of the tame and the wild kernel of a number field F is described in terms of ideal class groups of p-power cyclotomic extensions of F.     

Generalizations of Whipple's theorem on the sum of a 3F2

Thirty-eight summation closely related to Whipple's theorem, in the theory of the generalized hypergeometric series, are obtained. Some limiting cases are also considered.     

Differential-geometric Newton method for the best rank-(R1, R2, R3) approximation of tensors

An increasing number of applications are based on the manipulation of higher-order tensors. In this paper, we derive a differential-geometric Newton method for computing the best rank-(R ₁, R ₂, R ₃) approximation of a third-order tensor. The generalization to tensors of order higher than three is straightforward. We illustrate the fast quadratic convergence of the algorithm in a neighborhood of the solution and compare it with the known higher-order orthogonal iteration (De Lathauwer et al., SIAM J Matrix Anal Appl 21(4):1324–1342, 2000). This kind of algorithms are useful for many problems. This paper presents research results of the Belgian Network DYSCO (Dynamical Systems, Control, and Optimization), funded by the Interuniversity Attraction Poles Programme, initiated by the Belgian State, Science Policy Office. The scientific responsibility rests with its authors. Research supported by: (1) Research Council K.U.Leuven: GOA-Ambiorics, CoE EF/05/006 Optimization in Engineering (OPTEC), (2) F.W.O.: (a) project G.0321.06, (b) Research Communities ICCoS, ANMMM and MLDM, (3) the Belgian Federal Science Policy Office: IUAP P6/04 (DYSCO, “Dynamical systems, control and optimization”, 2007–2011), (4) EU: ERNSI. M. Ishteva is supported by a K.U.Leuven doctoral scholarship (OE/06/25, OE/07/17, OE/08/007), L. De Lathauwer is supported by “Impulsfinanciering Campus Kortrijk (2007–2012)(CIF1)” and STRT1/08/023.     

First-principles calculations on electronic, chemical bonding and optical properties of tetragonal SrHfO3

Electronic, chemical bonding and optical properties of tetragonal SrHfO₃ were investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT). The optimized equilibrium lattice parameters of tetragonal SrHfO₃ are in good agreement with experimental values. Band structure, densities of states (DOS), charge densities and molecular-orbital bonding structure of tetragonal SrHfO₃ have been obtained. The band structure shows that tetragonal SrHfO₃ has direct band gap. The DOS and charge densities indicate that bonding between Hf and O is mainly covalent due to Hf 5d and O 2p hybridization and that bonding between Sr and O is mainly ionic. The complex dielectric function, absorption coefficient, energy-loss spectrum, complex conductivity function and reflectivity of tetragonal SrHfO₃ have been predicted. The imaginary and real parts of the calculated complex dielectric functions are consistent with the experimental observations.     

K2 of a Ring via the G-Construction

We interpret the Steinberg symbols x_i,j(a) as homotopies contracting the elementary matrices e_i,j(a), the latters being represented by certain arcs in a simplicial model of the K-theory. We further prove the Steinberg relations for these homotopies. This provides an explicit map from K₂ of a ring, defined classically as ker(St(R) → GL(R)), to π₂ of the G-construction assigned to R. Though the two groups are known to be isomorphic, a certain work is to be done to prove that this explicit map is an isomorphism. Mathematics Subject Classification 1991: Primary 19B99, 19D99; secondary 18E10, 18F25.     

Quasirecognizability by the Set of Element Orders for Groups 3D4(q) and F4(q), for q Odd

It is proved that if L is one of the simple groups ³D₄(q) or F₄(q), where q is odd, and G is a finite group with the set of element orders as in L, then the derived subgroup of G/F(G) is isomorphic to L and the factor group G/G′ is a cyclic {2, 3}-group. __________ Translated from Algebra i Logika, Vol. 44, No. 5, pp. 517–539, September–October, 2005. Supported by RFBR grant No. 04-01-00463.     

The Region of Values of the System {f(z1), f(z2), f(z3)} on the Class of Typically Real Functions

The paper determines the region of values of the system occurring in the title on the class T of functions f(z) = z + ⋯ regular in the unit disk and satisfying the condition