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1.
Abdelkrim Chakib Touria Ghemires Abdeljalil Nachaoui 《Mathematical Methods in the Applied Sciences》2002,25(6):473-489
In this paper, the flow problem of incompressible liquid through an inhomogeneous porous medium (say dam), with permeability allowing parametrization of the free boundary by a graph of continuous unidimensional function, is considered. We propose a new formulation on an optimal shape design problem. We show the existence of a solution of the optimal shape design problem. The finite element method is used to obtain numerical results which show the efficiency of the proposed approach. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
The new ternary pnictides, Ti(1-delta)Mo(1+delta)Pn4 (Pn = As, Sb), were uncovered during our search for novel thermoelectric materials. Both compounds crystallize in the OsGe2 type in the monoclinic space group C2/m, with lattice dimensions of a = 10.1222(9) A, b = 3.6080(3) A, c = 8.1884(8) A, beta = 120.230(2) degrees , and V = 258.38(7) A3 (Z = 2) for Ti(0.79(1))Mo(1.21)Sb4 and a = 9.1580(2) A, b = 3.3172(1) A, c = 7.6666(1) A, beta = 119.496(1) degrees , and V = 202.720(4) A3 (Z = 2) for Ti(0.86(2))Mo(1.14)As4. The electronic structure calculations predicted metallic behavior for these compounds, which was in agreement with the measured temperature dependence of the electrical conductivity and Seebeck coefficient. 相似文献
3.
Derakhshan S Assoud A Kleinke KM Dashjav E Qiu X Billinge SJ Kleinke H 《Journal of the American Chemical Society》2004,126(26):8295-8302
The new binary antimonide Ti(2)Sb was found to crystallize in a distorted variant of the La(2)Sb type, which contains a square planar La net with short La-La bonds. In the Ti(2)Sb structure, the corresponding Ti net is deformed to squares and rhombs in order to enhance Ti-Ti bonding, as proven by single-crystal X-ray investigation in combination with the real-space pair distribution function technique utilizing both X-ray and neutron powder diffraction data. Electronic structure calculations revealed a lowering of the total energy caused by the disorder, the major driving force being strengthened Ti-Ti interactions along the diagonal of the Ti(4) rhombs. 相似文献
4.
The sulfide-tellurides Ba(3)Cu(17-x)(S,Te)(11) and Ba(3)Cu(17-x)(S,Te)(11.5) were synthesized from the elements in stoichiometric ratios heated to 1073 K, followed by slow cooling to 873 K over 100 h. Ba(3)Cu(17-x)(S,Te)(11) is isostructural to Ba(3)Cu(17-x)(Se,Te)(11) when [S] > [Te], space group R ?3m, with lattice dimensions of a = 12.009(1) ?, c = 27.764(2) ?, V = 3467.6(5) ?(3), for Ba(3)Cu(15.7(4))S(7.051(5))Te(3.949) (Z = 6). The structure is composed of Cu atoms forming paired hexagonal antiprisms, capped on the two outer hexagonal faces, where each Cu atom is tetrahedrally coordinated by four Q (= S, Te) atoms. The new variant is formed when [Te] > [S]; then Ba(3)Cu(17-x)(S,Te)(11.5) adopts space group Fm3?m with a = 17.2095(8) ?, V = 5096.9(4) ?(3), for Ba(3)Cu(15.6(2))S(5.33(4))Te(6.17) (Z = 8). This structure consists of eight Te-centered Cu(16) icosioctahedra per cell interconnected by cubic Cu(8) units centered by Q atoms. Electronic structure calculations and property measurements illustrate that these compounds behave as extrinsic p-type semiconductors-toward metallic behavior for the latter compound. With standard oxidation states Ba(2+), Cu(+), and Q(2-), the electron precise formulas are Ba(3)Cu(16)Q(11) and Ba(3)Cu(17)Q(11.5). 相似文献
5.
Yu X Mailman A Dube PA Assoud A Oakley RT 《Chemical communications (Cambridge, England)》2011,47(16):4655-4657
The alternating ABABAB π-stacked bis-1,2,3-dithiazolyl radical 2a (2, R(2)=Ph) has a conductivity σ of 3×10(-5) S cm(-1) at 300 K, and orders as a spin-canted antiferromagnet (T(N)=4.5 K) which undergoes a spin-flop transition to a field-induced ferromagnetic state saturating (at 2 K) at H ~20 kOe. 相似文献
6.
In this work we consider some eigenvalue problems for p-Laplacian with variable domain. Eigenvalues of this operator are taken as a functional of the domain. We calculate the first
variation of this functional, using the obtained formula investigate behavior of the eigenvalues when the domain varies. Then
we consider one shape optimization problem for the first eigenvalue, prove the necessary condition of optimality relatively
domain, offer an algorithm for the numerical solution of this problem. 相似文献
7.
The title compounds were prepared from the elements between 600 and 800 degrees C in evacuated silica tubes. Both tellurides, Ba7Au2Te14 and Ba6.76Cu2.42Te14, form ternary variants of the NaBa6Cu3Te14 type, space group P63/mcm, with a = 14.2593(7) A, c = 9.2726(8) A, and V = 1632.8(2) A3 (Z = 2) for Ba7Au2Te14 and a = 14.1332(4) A, c = 9.2108(6) A, and V = 1593.3(1) A3 (Z = 2) for Ba6.76Cu2.42Te14. The Na site is filled with a Ba atom (deficient in case of the Cu telluride) and the Cu site with 66.5(3)% Au and 61.7(8)% Cu. An additional site is filled with 9.5(7)% Cu in the structure of Ba6.76Cu2.42Te14. These structures are comprised of bent Te32- units and AuTe4/CuTe4 tetrahedra, forming channels filled with Ba cations. The BaTe9 polyhedra are connecting the channels to a three-dimensional structure. According to the formulations (Ba2+)7(Au+)2(Te32-)3(Te2-)5 and (Ba2+)6.76(Cu+)2.42(Te32-)3(Te2-)5, the materials are electron-precise with 16 positive charges equalizing the 16 negative charges. Correspondingly, both tellurides are semiconductors, as experimentally confirmed, with calculated band gaps of 0.7 and 1.0 eV, respectively. 相似文献
8.
Bineta Keita Essadik Abdeljalil François Girard Sophie Gerschwiler Louis Nadjo Roland Contant Christian Haut 《Journal of Solid State Electrochemistry》1999,3(7-8):446-456
New oxide films have been electrodeposited from [P2Mo18O62]6− by potential cycling in mildly acidic aqueous media. To obtain an adherent and persistent film, it is necessary that more
than six electrons/molecule be fixed on the framework of the heteropolyanion. The film is then studied in pure supporting
electrolyte. In this medium, a remarkable current increase is observed during the potential cycling. Whether the film is deposited
on a glassy carbon electrode or on the gold electrode of an electrochemical quartz crystal microbalance (EQCM), exactly the
same steady current increase up to a maximum is obtained in cyclic voltammetric measurements. The EQCM reveals a steady mass
increase during the continuous cycling of the film in the supporting electrolyte. This behaviour is interpreted as featuring
an irreversible water and electrolyte intake into the film, up to a maximum, after which the phenomena observed during reduction
and oxidation processes are taken as featuring intercalation/deintercalation, respectively. This behaviour is much the same
as described in the literature for WO3 and MoO3 bronzes, except that the present films seem very stable and have shown no tendency to dissolve or deactivate.
Received: 2 December 1998 / Accepted: 26 January 1999 相似文献
9.
The telluride Ba(2)Cu(7-x)Te(6) was synthesized from the elements in stoichiometric ratios, heated to 1073 K, followed by slow cooling to 873 K over 120 h. Ba(2)Cu(7-x)Te(6) crystallizes in space group P2(1)/m with lattice dimensions of a = 6.8591(7) ?, b = 12.1439(12) ?, c = 9.0198(9) ?, β = 110.7509(14)°, V = 702.58(12) ?(3), and Z = 2. The structure is comprised of Cu atoms forming a six-membered ring and triangles, interconnected to an infinite ribbon of Cu atoms. The ribbons are connected to each other via Cu-Te bonds to yield a three-dimensional structure, wherein each Cu atom is tetrahedrally coordinated by four Te atoms. A special feature of this telluride is the occurrence of a quasi-linear Te atom chain, which causes one-dimensional metallic properties, in accordance with electronic structure calculations and property measurements. 相似文献
10.
Abdeljalil Assoud 《Journal of solid state chemistry》2006,179(8):2707-2713
The title compounds were prepared from the elements in the stoichiometric ratio at 800 °C under exclusion of air. Tl6Si2Te6 crystallizes in the space group P1¯, isostructural with Tl6Ge2Te6, with , , , α=89.158(2)°, β=96.544(2)°, γ=100.685(2)°, (Z=2). Its structure is composed of dimeric [Si2Te6]6− units with a Si-Si single bond, while the Tl atoms are irregularly coordinated by five to six Te atoms. Numerous weakly bonding Tl-Tl contacts exist. Both title compounds are black semiconductors with small band gaps, calculated to be 0.9 eV for Tl6Si2Te6 and 0.5 eV for Tl6Ge2Te6. The Seebeck coefficients are +65 μV K−1 in case of Tl6Si2Te6 and +150 μV K−1 in case of Tl6Ge2Te6 at 300 K, and the electrical conductivities are 5.5 and 3 Ω−1 cm−1, respectively. 相似文献