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91.
We give counterexamples to the following conjecture of Auslander: given a finitely generated module M over an Artin algebra Λ, there exists a positive integer nM such that for all finitely generated Λ-modules N, if ExtΛi(M,N)=0 for all i?0, then ExtΛi(M,N)=0 for all i?nM. Some of our examples moreover yield homologically defined classes of commutative local rings strictly between the class of local complete intersections and the class of local Gorenstein rings. 相似文献
92.
It can be conjectured that the colored Jones function of a knot can be computed in terms of counting paths on the graph of
a planar projection of a knot. On the combinatorial level, the colored Jones function can be replaced by its weight system.
We give two curious formulas for the weight system of a colored Jones function: one in terms of the permanent of a matrix
associated to a chord diagram, and another in terms of counting paths of intersecting chords.
Electronic supplementary material to this article is available at and is accessible to authorized users.
* S. G. was partially supported by an NSF and by an Israel-US BSF grant.
† M. L. was partly supported by GAUK 158 grant and by the Project LN00A056 of the Czech Ministry of Education. 相似文献
93.
We study a class of shape optimization problems for semi-linear elliptic equations with Dirichlet boundary conditions in smooth
domains in ℝ2. A part of the boundary of the domain is variable as the graph of a smooth function. The problem is equivalently reformulated
on a fixed domain. Continuity of the solution to the state equation with respect to domain variations is shown. This is used
to obtain differentiability in the general case, and moreover a useful formula for the gradient of the cost functional in
the case where the principal part of the differential operator is the Laplacian.
Online publication 23 January 2004. 相似文献
94.
95.
J. L. Hernández–Pastora O. V. Manko V. S. Manko J. Martín E. Ruiz 《General Relativity and Gravitation》2004,36(4):781-797
The extended quadruple–Kerr metric is used to consider equilibrium states of four collinear Kerr particles. We explain our previous failure to solve numerically the full set of the balance equations, and we derive a self–consistent system of the axis conditions leading to the equilibrium of all four constituents which can be black holes or hyperextreme objects. The equilibrium configurations obtained in this paper exhibit similar features with those occurring in the systems of two Kerr particles, for instance, the balance of four Kerr black holes with positive masses does not seem possible. Equilibrium states of two identical compound Kerr objects are also discussed. 相似文献
96.
J. Mlynár J. Ongena The EFDA JET Contributions I. Duran M. Hron R. Pánek V. Petržílka F. Žáček 《Czechoslovak Journal of Physics》2004,54(3):C28
JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years. 相似文献
97.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels. 相似文献
98.
Hamid R. Memarian Mohammad Bagheri Dietrich D?pp 《Monatshefte für Chemie / Chemical Monthly》2004,42(3):833-838
In continuation of previous work some novel 3,5-diacetyl-1,4-dihydropyridine derivatives were synthesized and their photochemical behavior was studied under oxygen and argon atmosphere. Oxidation of the dihydropyridine ring and formation of pyridine derivatives was the result of the reaction. The presence of oxygen affects not only on the rate of oxidation, but also the formation of some unidentified by-products was observed on irradiation under this atmosphere. 相似文献
99.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献
100.
E. García-Matres N. Stüßer M. Hofmann M. Reehuis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):35-42
The magnetic structures of Mn1-xFexWO4 with x
= 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase
diagram could be completed in the coexistence range of different magnetic structures up to x
= 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector
= (±1/4, 1/2, 1/2) was found for x
⩽ 0.22 while the magnetic spins order with
= (1/2, 0, 0) for x
≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with
= (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x
= 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽
x
⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed
to a spin arrangement with
= (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed
Mn2+- and Fe2+-ions in the coexistence range 0.12 ⩽
x
⩽ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
Received 9 October 2002 Published online 14 March 2003 相似文献