共查询到20条相似文献,搜索用时 0 毫秒
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Nondegenerate plane congruences in the four-dimensional complex projective space with degenerate general focal conic are classified by using the focal method due to Corrado Segre. 相似文献
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本文主要研究线性差分方程 $A_n(z)f(z+n)+\cdots+A_1(z)f(z+1)+A_0(z)f(z)=0$亚纯解的增长级.当上述方程的系数中没有起控制作用的系数时,我们给出了一些约束条件,得到了一些结果,所得结果部分回答了I. Laine和杨重骏的一个问题. 相似文献
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Deborah Evelyn 《The Journal of the Operational Research Society》1979,30(12):1136-1136
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A successful experimental synthesis of pure crystalline β- and α-C3N4 films on Si(100) substrate was carried out by bias-assisted hot filament chemical vapor deposition (bias-HFCVD). It is found
that a mixed-phase C3-I-SixNy buffer layer was formed between the Si substrate and the C-N film. A “lattice match selection” was proposed to study the
growth mechanism of C3N4 clusters composed of many crystal columns with hexagonal facets.
Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences. 相似文献
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We show that for any computably enumerable (c.e.) set A and any set L, if L is low and , then there is a c.e. splitting such that . In Particular, if L is low and n‐c.e., then is n‐c.e. and hence there is no low maximal n‐c.e. degree. 相似文献
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W. Brüggemann K. Fischer H. Jahnke 《Journal of Mathematical Modelling and Algorithms》2003,2(2):121-151
The meaning of the term problem in operations research (OR) deviates from the understanding in the theoretical computer sciences: While an OR problem is often conceived to be stated or represented by model formulations, a computer-science problem can be viewed as a mapping from encoded instances to solutions. Such a computer-science problem turns out to be rather similar to an OR model formulation. This ambiguity may cause difficulties if the computer-science theory of computational complexity is applied in the OR context. In OR, a specific model formulation is commonly used in the analysis of the underlying problem and the results obtained for this model are simply lifted to the problem level. But this may lead to erroneous results, if the model used is not appropriate for such an analysis of the problem.To resolve this issue, we first suggest a new precise formal definition of the term problem which is identified with an equivalence class of models describing it. Afterwards, a new definition is suggested for the size of a model which depends on the assumed encoding scheme. Only models which exhibit a minimal size with respect to a reasonable encoding scheme finally turn out to be suitable for the model-based complexity analysis of an OR problem. Therefore, the appropriate choice (or if necessary the construction) of a suitable representative of an OR problem becomes an important theoretical aspect of the modelling process. 相似文献
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G. G. Stephenson 《The Journal of the Operational Research Society》1970,21(2):221-245
In any large diverse company, organizational divisions are necessary to enable management to manage efficiently. The use of models in planning enables activities to be cohesively planned, but divisions must still be drawn. This paper describes the system of models developed for planning in one division of I.C.I. It sets out a philosophy of approach to modelling, covering many individual case studies which have forced the problem of divisions to be tackled. The solutions chosen appear to work well in one management environment. 相似文献
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A connected, finite two-dimensional CW-complex with fundamental group isomorphic toG is called a [G, 2]
f
-complex. LetL⊲G be a normal subgroup ofG. L has weightk if and only ifk is the smallest integer such that there exists {l
1,…,l
k}⊆L such thatL is the normal closure inG of {l
1,…,l
k}. We prove that a [G, 2]
f
-complexX may be embedded as a subcomplex of an aspherical complexY=X∪{e
1
2
,…,e
k
2
} if and only ifG has a normal subgroupL of weightk such thatH=G/L is at most two-dimensional and defG=defH+k. Also, ifX is anon-aspherical [G, 2]
f
-subcomplex of an aspherical 2-complex, then there exists a non-trivial superperfect normal subgroupP such thatG/P has cohomological dimension ≤2. In this case, any torsion inG must be inP. 相似文献
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V. A. Steklov Mathematics Institute, USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 82, No. 2, pp. 163–177. February, 1990. 相似文献
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V. N. Kublanovskaya 《Journal of Mathematical Sciences》2006,132(2):214-223
The paper continues the investigation of methods for factorizing q-parameter polynomial matrices and considers their applications
to solving multiparameter problems of algebra. An extension of the AB-algorithm, suggested earlier as a method for solving
spectral problems for matrix pencils of the form A - λB, to the case of q-parameter (q ≥ 1) polynomial matrices of full rank
is proposed. In accordance with the AB-algorithm, a finite sequence of q-parameter polynomial matrices such that every subsequent
matrix provides a basis of the null-space of polynomial solutions of its transposed predecessor is constructed. A certain
rule for selecting specific basis matrices is described. Applications of the AB-algorithm to computing complete polynomials
of a q-parameter polynomial matrix and exhausting them from the regular spectrum of the matrix, to constructing irreducible
factorizations of rational matrices satisfying certain assumptions, and to computing “free” bases of the null-spaces of polynomial
solutions of an arbitrary q-parameter polynomial matrix are considered. Bibliography: 7 titles.
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Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 309, 2004, pp. 127–143. 相似文献