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1.
Results of an experimental observation of the voltage oscillations associated with a discrete tunneling of holes in porous silicon at room temperature are presented. The noise characteristics of diode structures with a porous silicon interlayer formed on heavily boron-doped silicon single crystals are studied. Peaks of excessive noise are observed at frequencies of ~1 MHz, at which single-electron oscillations should be expected. The peak noise power is found to increase with current according to the ~2.5 power law and, at a current density of 0.15 A/cm2, to exceed the noise power of the receiver by three to four orders of magnitude. The complex shape of the noise spectrum and its extension to the higher frequency region with increasing current are explained by the three-dimensionality of the system of nanometer-sized silicon grains embedded in insulating silicon dioxide of porous silicon. 相似文献
2.
LetN = (G, T, c, a) be a network, whereG is an undirected graph,T is a distinguished subset of its vertices (calledterminals), and each edgee ofG has nonnegative integer-valuedcapacity c(e) andcost a(e). Theminimum cost maximum multi(commodity)flow problem (*) studied in this paper is to find ac-admissible multiflowf inG such that: (i)f is allowed to contain partial flows connecting any pairs of terminals, (ii) the total value off is as large as possible, and (iii) the total cost off is as small as possible, subject to (ii). This generalizes, on one hand, the undirected version of the classical minimum cost maximum flow problem (when |T| = 2), and, on the other hand, the problem of finding a maximum fractional packing ofT-paths (whena 0). Lovász and Cherkassky independently proved that the latter has a half-integral optimal solution.A pseudo-polynomial algorithm for solving (*) has been developed earlier and, as its consequence, the theorem on the existence of a half-integral optimal solution for (*) was obtained. In the present paper we give a direct, shorter, proof of this theorem. Then we prove the existence of a half-integral optimal solution for the dual problem. Finally, we show that half-integral optimal primal and dual solutions can be designed by a combinatorial strongly polynomial algorithm, provided that some optimal dual solution is known (the latter can be found, in strongly polynomial time, by use of a version of the ellipsoid method).This work was partially supported by Chaire municipale, Mairie de Grenoble, France. 相似文献
3.
We consider a certain combinatorial game on a digraph for two cases of the price function. For one case the game in question extends the cyclical game studied in Ehrenfeucht and Mycielski (1979) and Gurvitch, Karzanov and Khachiyan (1988) which, in its turn, is a generalization of the well-known problem of finding a minimum mean cycle in an edge-weighted digraph. We prove the existence of optimal uniform stationary strategies for both cases and give algorithms to find such strategies.This work was partially supported by Chaire municipale, Mairie de Grenoble. 相似文献
4.
Let Q be a convex solid in
n
, partitioned into two volumes u and v by an area s. We show that s>min(u,v)/diam Q, and use this inequality to obtain the lower bound n
-5/2 on the conductance of order Markov chains, which describe nearly uniform generators of linear extensions for posets of size n. We also discuss an application of the above results to the problem of sorting of posets.Computing Center of the USSR Academy of Sciences USSR 相似文献
5.
be a network, where is an undirected graph with nodes and edges, is a set of specified nodes of , called terminals, and each edge of has a nonnegative integer capacity . If the total capacity of edges with one end at is even for every non-terminal node , then is called inner Eulerian. A free multiflow is a collection of flows between arbitrary pairs of terminals such that the total flow through each edge
does not exceed its capacity.
In this paper we first generalize a method in Karzanov [11] to find a maximum integer free multiflow in an inner Eulerian network, in time, where is the complexity of finding a maximum flow between two terminals. Next we extend our algorithm to solve the so-called laminar locking problem on multiflows, also in time.
We then consider analogs of the above problems in inner balanced directed networks, which means that for each non-terminal node , the sums of capacities of arcs entering and leaving are the same. We show that for such a network a maximum integer free multiflow can be constructed in time, and then extend this result to the corresponding locking problem.
Received: March 24, 1997 相似文献
6.
A. V. Karzanov 《Combinatorica》1985,5(4):325-335
A family ℱ of cuts of an undirected graphG=(V, E) is known to have the weak MFMC-property if (i) ℱ is the set ofT-cuts for someT⊆V with |T| even, or (ii) ℱ is the set of two-commodity cuts ofG, i.e. cuts separating any two distinguished pairs of vertices ofG, or (iii) ℱ is the set of cuts induced (in a sense) by a ring of subsets of a setT⊆V. In the present work we consider a large class of families of cuts of complete graphs and prove that a family from this class
has the MFMC-property if and only if it is one of (i), (ii), (iii). 相似文献
7.
A. V. Karzanov 《Mathematical Programming》1985,32(2):183-198
Suppose thatG is an undirected graph whose edges have nonnegative integer-valued lengthsl(e), and that {s 1,t 1},?, {s m ,t m } are pairs of its vertices. Can one assign nonnegative weights to the cuts ofG such that, for each edgee, the total weight of cuts containinge does not exceedl(e) and, for eachi, the total weight of cuts ‘separating’s i andt i is equal to the distance (with respect tol) betweens i andt i ? Using linear programming duality, it follows from Papernov's multicommodity flow theorem that the answer is affirmative if the graph induced by the pairs {s 1,t 1},?, {s m ,t m } is one of the following: (i) the complete graph with four vertices, (ii) the circuit with five vertices, (iii) a union of two stars. We prove that if, in addition, each circuit inG has an even length (with respect tol) then there exists a suitable weighting of the cuts with the weights integer-valued; moreover, an algorithm of complexity O(n 3) (n is the number of vertices ofG) is developed for solving such a problem. Also a class of metrics decomposable into a nonnegative linear combination of cut-metrics is described, and it is shown that the separation problem for cut cones isNP-hard. 相似文献
8.
E. S. Demidov N. E. Demidova V. V. Karzanov K. A. Markov V. V. Sdobnyakov 《Physics of the Solid State》2009,51(10):2007-2013
Experimental data obtained in the study of transverse current transport in a number of nanosized grained or similar media,
such as porous silicon layers, anodic silicon oxide layers, and silicon nitride layers prepared by ion implantation of nitrogen
into silicon, have been analyzed within the theory of discrete tunneling. It has been demonstrated that the measurements of
current-voltage characteristics of diode structures with dielectric interlayers and embedded grains make it possible to obtain
useful information on the character and sizes of grains or quantum dots in the nanosized grained medium. Amorphous dielectrics
can be considered a grained medium with nanosized composition fluctuations. The current-voltage characteristics of real structures
are determined by both the current nonlinearity associated with the charge carrier injection and the field nonlinearity caused
by the Coulomb blockade of tunneling. 相似文献
9.
10.
It is pointed out that in the partial oxidation of porous silicon (PS) formed on heavily doped crystals, the topology of the
pores can result in the formation of an anisotropic material with strings of nanometersized silicon granules embedded in insulating
silicon dioxide SiO2. In this range of granule sizes the correlation effects in the tunneling of electrons (holes) are strong on account of their
Coulomb interaction. This should be manifested as discrete electron and hole tunneling at temperatures comparable to room
temperature. The room-temperature current-voltage characteristics of n
+-PSp
+-p
+ diode structures with a PS interlayer on p
+-Si, which exhibit current steps on the forward and reverse branches, are presented. The current steps are attributed to discrete
hole tunneling along the silicon strings in SiO2.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 794–797 (25 May 1998) 相似文献