共查询到20条相似文献,搜索用时 483 毫秒
1.
两类带有确定潜伏期的SEIS传染病模型的分析 总被引:2,自引:0,他引:2
通过研究两类带有确定潜伏期的SEIS传染病模型,发现对种群的常数输入和指数输入会使疾病的传播过程产生本质的差异.对于带有常数输入的情形,找到了地方病平衡点存在及局部渐近稳定的阈值,证明了地方病平衡点存在时一定局部渐近稳定,并且疾病一致持续存在.对于带有指数输入的情形,发现地方病平衡点当潜伏期充分小时是局部渐近稳定的,当潜伏期充分大时是不稳定的. 相似文献
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科学合理的规模结构不仅是实现规模经济的基本条件,而且是提高经济效益、降低交易成本、获得较高的企业竞争力的重要保证.基于规模理论,从生产规模、资本规模、市场规模以及效益规模四大因素入手,提出了一套基于规模的企业竞争力评价指标体系,运用蜘蛛图法建立了基于规模的企业竞争力评价模型,并结合具体的数据分析说明了企业竞争力的大小强弱.此种方法具有直观形象、定量化、可操作性强的特点. 相似文献
3.
Zhang Jule 《东北数学》1998,(1)
in this paper, new characteristic properties of strongly regular rings are' given.Relations between certain generalizations of duo rings are also considered. The followingconditions are shown to be equivalent: (1) R is a strongly regular ring; (2) R is a left SFring such that every product of two independent closed left ideals of R is zero; (3) R is aright SF-ring such that every product of two independent closed left ideals of R is zero; (4)R is a left SF-ring whose every special left annihilator is a quasi-ideal; (5) R is a right SFring whose every special left annihilator is a quasi-ideal; (6) R is a left SF-ring whose everymaximal left ideal is a quasi-ideal; (7) R is a right SF-ring whose every maximal left ideal isa quasi-ideal; (8) R is a left SF-ring such that the set N(R) of all nilpotent elements of R isa quasi-ideal; (9) R is a right SF-ring such that N(R) is a quasi-ideal. 相似文献
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The independence polynomial of a graph is the generating function of the numbers of independent sets of each size. A graph of order is very well-covered if every maximal independent set has size . Levit and Mandrescu conjectured that the independence polynomial of every very well-covered graph is unimodal (that is, the sequence of coefficients is nondecreasing, then nonincreasing). In this article we show that every graph is embeddable as an induced subgraph of a very well-covered graph whose independence polynomial is unimodal, by considering the location of the roots of such polynomials. 相似文献
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整环R称为ω-凝聚整环,是指R的每个有限型理想是有限表现型的.本文证明了ω-凝聚整环是v-凝聚整环,且若(RDTF,M)是Milnor方图,则在Ⅰ型情形,R是ω-凝聚整环当且仅当D和T都是ω-整环,且T_M是赋值环;对于Ⅱ-型情形,R是ω-凝聚整环当且仅当D是域,[F:D]<∞,M是R的有限型理想,T是ω-凝聚整环,且R_M是凝聚整环. 相似文献
7.
Malin Palö Forsström 《Stochastic Processes and their Applications》2018,128(11):3880-3896
In a recent paper by Jonasson and Steif, definitions to describe the volatility of sequences of Boolean functions, were introduced. We continue their study of how these definitions relate to noise stability and noise sensitivity. Our main results are that the set of volatile sequences of Boolean functions is a natural way “dense” in the set of all sequences of Boolean functions, and that the set of non-volatile Boolean sequences is not “dense” in the set of noise stable sequences of Boolean functions. 相似文献
8.
Xu Xiang 《数学年刊B辑(英文版)》1995,16(2):255-260
POINTEDREPRESENTATIONSOFINFINITEDIMENSIONALLIEALGEBRAS¥XUXIANGAbstract:AcontravariedbilinearpairingXoneveryM(ρ)×M(ρθ)isdeterm... 相似文献
9.
Ferenc Bencs 《Discrete Mathematics》2018,341(12):3321-3330
The independence polynomial of a graph is where denotes the number of independent sets of of size (note that ). In this paper we show a new method to prove real-rootedness of the independence polynomials of certain families of trees.In particular we will give a new proof of the real-rootedness of the independence polynomials of centipedes (Zhu’s theorem), caterpillars (Wang and Zhu’s theorem), and we will prove a conjecture of Galvin and Hilyard about the real-rootedness of the independence polynomial of the so-called Fibonacci trees. 相似文献
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In this work we analyze some topological properties of the remainder of the semialgebraic Stone–Cěch compactification of a semialgebraic set in order to ‘distinguish’ its points from those of M. To that end we prove that the set of points of that admit a metrizable neighborhood in equals where is the largest locally compact dense subset of M and is the closure in M of the set of 1-dimensional points of M. In addition, we analyze the properties of the sets and of free maximal ideals associated with formal and semialgebraic paths. We prove that both are dense subsets of the remainder ?M and that the differences and are also dense subsets of ?M. It holds moreover that all the points of have countable systems of neighborhoods in . 相似文献
12.
The paper investigates the properties of a class of resource allocation algorithms for communication networks: if a node of this network has requests to transmit and is idle, it tries to access the channel at a rate proportional to . A stochastic model of such an algorithm is investigated in the case of the star network, in which nodes can transmit simultaneously, but interfere with a central node 0 in such a way that node 0 cannot transmit while one of the other nodes does. One studies the impact of the log policy on these interacting communication nodes. A fluid scaling analysis of the network is derived with the scaling parameter being the norm of the initial state. It is shown that the asymptotic fluid behavior of the system is a consequence of the evolution of the state of the network on a specific time scale . The main result is that, on this time scale and under appropriate conditions, the state of a node with index is of the order of , with , where is a piecewise linear function. Convergence results on the fluid time scale and a stability property are derived as a consequence of this study. 相似文献
13.
Xiaoan Zhou Junfeng Lan Shuisheng Qiu 《Communications in Nonlinear Science & Numerical Simulation》1999,4(4):292
A kind of chaotic synchronization method is presented in the paper. In the transmitter, part signals are transformed by wavelet and the detail information is removed. In the receiver, the component with low frequency is reconstructed and discrete feedback is used, we show that synchronization of two identical structure chaotic systems is attained. The effect of feedback on chaotic synchronization is discussed. Using the synchronous method, the transmitting signal is transported in compressible way, system resource is saved, the component with high frequency is filtered and the effect of disturbance on synchronization is reduced. The synchronization method is illustrated by numerical simulation experiment. 相似文献
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It is trivial that every 3-polytope has a face of degree at most 5, called minor. The height of a face is the maximum degree of the vertices incident with . It follows from the partial double -pyramids that can be arbitrarily large for each if a 3-polytope is allowed to have faces of types or .In 1996, M. Horňák and S. Jendrol’ proved that every 3-polytope without faces of types and has a minor face of height at most 39 and constructed such a 3-polytope satisfying for all minor faces .The purpose of this paper is to prove that every 3-polytope without faces of types and has a minor face of height at most 30, which bound is tight due to the Horňák–Jendrol’ construction. 相似文献
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Let be a finite simple graph. For , the difference of , where is the neighborhood of and is called the critical difference of . is called a critical set if equals the critical difference and is the intersection of all critical sets. is the union of all critical independent sets. An independent set is an inclusion minimal set with if no proper subset of has positive difference.A graph is called a König–Egerváry graph if the sum of its independence number and matching number equals .In this paper, we prove a conjecture which states that for any graph the number of inclusion minimal independent set with is at least the critical difference of the graph.We also give a new short proof of the inequality .A characterization of unicyclic non-König–Egerváry graphs is also presented and a conjecture which states that for such a graph , the critical difference equals , is proved.We also make an observation about using Edmonds–Gallai Structure Theorem as a concluding remark. 相似文献
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Takahiko Hara 《Annals of the Institute of Statistical Mathematics》1988,40(2):395-406
This paper is concerned with two kinds of multiple outlier problems in multivariate regression. One is a multiple location-slippage problem and the other is a multiple scale-inflation problem. A multi-decision rule is proposed. Its optimality is shown for the first problem in a class of left orthogonally invariant distributions and is also shown for the second problem in a class of elliptically contoured distributions. Thus the decision rule is robust against departures from normality. Further the null robustness of the decision statistic which the rule is based on is pointed out in each problem. 相似文献
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DP-coloring of a simple graph is a generalization of list coloring, and also a generalization of signed coloring of signed graphs. It is known that for each , every planar graph without is 4-choosable. Furthermore, Jin et al. (2016) showed that for each , every signed planar graph without is signed 4-choosable. In this paper, we show that for each , every planar graph without is 4-DP-colorable, which is an extension of the above results. 相似文献
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This paper deals with the Cayley graph , where the generating set consists of all block transpositions. A motivation for the study of these particular Cayley graphs comes from current research in Bioinformatics. As the main result, we prove that is the product of the left translation group and a dihedral group of order . The proof uses several properties of the subgraph of induced by the set . In particular, is a -regular graph whose automorphism group is
has as many as maximal cliques of size , and its subgraph whose vertices are those in these cliques is a 3-regular, Hamiltonian, and vertex-transitive graph. A relation of the unique cyclic subgroup of of order with regular Cayley maps on is also discussed. It is shown that the product of the left translation group and the latter group can be obtained as the automorphism group of a non--balanced regular Cayley map on . 相似文献
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Let be a purely discontinuous additive functional of a subordinate Brownian motion . We give a sufficient condition on the non-negative function that guarantees that finiteness of implies finiteness of its expectation. This result is then applied to study the relative entropy of and the probability measure induced by a purely discontinuous Girsanov transform of the process . We prove these results under the weak global scaling condition on the Laplace exponent of the underlying subordinator. 相似文献