1,855 research outputs found
Dynamics of structural defects and plasticity: models and numerical implementation for dynamical problems
We report the plasticity model with explicit description of kinetics of the material defects (dislocations, grain boundaries). This method becomes especially effective for computation of the dynamical deformation of materials at high strain rates because it allows for a simple accounting of the strain rate effects. The equation system is written out and discussed; its implementation is demonstrated for the problem of the plastic flow localization
Generalized Green Functions and current correlations in the TASEP
We study correlation functions of the totally asymmetric simple exclusion
process (TASEP) in discrete time with backward sequential update. We prove a
determinantal formula for the generalized Green function which describes
transitions between positions of particles at different individual time
moments. In particular, the generalized Green function defines a probability
measure at staircase lines on the space-time plane. The marginals of this
measure are the TASEP correlation functions in the space-time region not
covered by the standard Green function approach. As an example, we calculate
the current correlation function that is the joint probability distribution of
times taken by selected particles to travel given distance. An asymptotic
analysis shows that current fluctuations converge to the process.Comment: 46 pages, 3 figure
Exact Domain Integration in the Boundary Element Method for 2D Poisson Equation
Boundary value problems for Poisson equation often
appear in electrical engineering applications, such as magnetic
and electric field modeling and so on. In such context, effective
techniques of solving such equations are subject of continuous
development. This article reports an exact formula for domain
integral in boundary-integral form of 2D Poisson Equation. This
formula is derived for rectangle domain element
Statistics of layered zigzags: a two-dimensional generalization of TASEP
A novel discrete growth model in 2+1 dimensions is presented in three
equivalent formulations: i) directed motion of zigzags on a cylinder, ii)
interacting interlaced TASEP layers, and iii) growing heap over 2D substrate
with a restricted minimal local height gradient. We demonstrate that the
coarse-grained behavior of this model is described by the two-dimensional
Kardar-Parisi-Zhang equation. The coefficients of different terms in this
hydrodynamic equation can be derived from the steady state flow-density curve,
the so called `fundamental' diagram. A conjecture concerning the analytical
form of this flow-density curve is presented and is verified numerically.Comment: 5 pages, 4 figure
Total coloring of 1-toroidal graphs of maximum degree at least 11 and no adjacent triangles
A {\em total coloring} of a graph is an assignment of colors to the
vertices and the edges of such that every pair of adjacent/incident
elements receive distinct colors. The {\em total chromatic number} of a graph
, denoted by \chiup''(G), is the minimum number of colors in a total
coloring of . The well-known Total Coloring Conjecture (TCC) says that every
graph with maximum degree admits a total coloring with at most colors. A graph is {\em -toroidal} if it can be drawn in torus such
that every edge crosses at most one other edge. In this paper, we investigate
the total coloring of -toroidal graphs, and prove that the TCC holds for the
-toroidal graphs with maximum degree at least~ and some restrictions on
the triangles. Consequently, if is a -toroidal graph with maximum degree
at least~ and without adjacent triangles, then admits a total
coloring with at most colors.Comment: 10 page
Mechanical characteristics, as well as physical-and-chemical properties of the slag-filled concretes, and investigation of the predictive power of the metaheuristic approach
Our article is devoted to development and verification of the metaheuristic optimisation algorithm in the course of selection of the compositional proportions of the slag-filled concretes. The experimental selection of various compositions and working modes, which ensure one and the same fixed level of a basic property, is the very labour-intensive and time-consuming process. This process cannot be feasible in practice in many situations, for example, in the cases, where it is necessary to investigate composite materials with equal indicators of resistance to aggressive environments or with equal share of voids in the certain range of dimensions. There are many similar articles in the scientific literature. Therefore, it is possible to make the conclusion on the topicality of the above-described problem. In our article, we will consider development of the methodology of the automated experimental-and-statistical determination of optimal compositions of the slag-filled concretes. In order to optimise search of local extremums of the complicated functions of the multi-factor analysis, we will utilise the metaheuristic optimisation algorithm, which is based on the concept of the swarm intelligence. Motivation in respect of utilisation of the swarm intelligence algorithm is conditioned by the absence of the educational pattern, within which it is not necessary to establish a certain pattern of learning as it is necessary to do in the neural-network algorithms. In the course of performance of this investigation, we propose this algorithm, as well as procedure of its verification on the basis of the immediate experimental verification. Open Access. © 2019 K. Borodin and N. Zhangabayuly Zhangabay, published by De Gruyter
Temperature, pressure and density of Venus' atmosphere according to measurement data of the AIS Venera-4
Atmospheric temperature, pressure, and density of Venus according to measurements obtained by AIS Venera-
Changing Bases: Multistage Optimization for Matroids and Matchings
This paper is motivated by the fact that many systems need to be maintained
continually while the underlying costs change over time. The challenge is to
continually maintain near-optimal solutions to the underlying optimization
problems, without creating too much churn in the solution itself. We model this
as a multistage combinatorial optimization problem where the input is a
sequence of cost functions (one for each time step); while we can change the
solution from step to step, we incur an additional cost for every such change.
We study the multistage matroid maintenance problem, where we need to maintain
a base of a matroid in each time step under the changing cost functions and
acquisition costs for adding new elements. The online version of this problem
generalizes online paging. E.g., given a graph, we need to maintain a spanning
tree at each step: we pay for the cost of the tree at time
, and also for the number of edges changed at
this step. Our main result is an -approximation, where is
the number of elements/edges and is the rank of the matroid. We also give
an approximation for the offline version of the problem. These
bounds hold when the acquisition costs are non-uniform, in which caseboth these
results are the best possible unless P=NP.
We also study the perfect matching version of the problem, where we must
maintain a perfect matching at each step under changing cost functions and
costs for adding new elements. Surprisingly, the hardness drastically
increases: for any constant , there is no
-approximation to the multistage matching maintenance
problem, even in the offline case
Finding the Median (Obliviously) with Bounded Space
We prove that any oblivious algorithm using space to find the median of a
list of integers from requires time . This bound also applies to the problem of determining whether the median
is odd or even. It is nearly optimal since Chan, following Munro and Raman, has
shown that there is a (randomized) selection algorithm using only
registers, each of which can store an input value or -bit counter,
that makes only passes over the input. The bound also implies
a size lower bound for read-once branching programs computing the low order bit
of the median and implies the analog of for length oblivious branching programs
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