bluuebunny/crossref_metadata_2025_split huggingface dataset:
MICROSTRUCTURAL CHARACTERISATION OF NON-MAGNETIC Ni-BASED BIAXIALLY TEXTURED SUBSTRATES FOR HTS COATED CONDUCTOR APPLICATIONS
Authors: VILLA E. , TUISSI A. , TOMOV R. , EVETTS J. E. 
Published: May 2003

For the production of HTS coated conductor devices, NiV and NiCr (Ni-based alloys) are the most important, non-magnetic, high strength and biaxially textured substrates developed from pure Ni. The Ni 88 V 12 and Ni 85 Cr 15 (at. %) alloys have been melted in Plasma Arc Furnace and textured tapes have been prepared, after heavy cold rolling, by recrystallization heat treatment under high vacuum. The suitable working conditions have been found to obtain not only the {100} <001> cube texture but also the correct grain shape and size for the following deposition process. Out of plane orientation of these substrates has been investigated by θ-2θ X-ray diffraction measurements and in plane orientation study has been completed by pole figures. The microstructure has been observed by optical microscopy: it has been carried out on samples obtained after an annealing treatment (Grain Size Adjustment) and on recrystallized samples in different conditions. As preliminary mechanical investigation the microhardness values have been detected for each step of the working procedure. The accuracy of the cubic texture and the grain structure are affected by the processing condition, in particular the temperature of the GSA seems a very important parameter which influences the final characteristics of the tapes.
RECTANGLE AND BOX VISIBILITY GRAPHS IN 3D
Authors: FEKETE SÁNDOR R. , MEIJER HENK 
Published: May 2003

We discuss rectangle and box visibility representations of graphs in 3-dimensional space. In these representations, vertices are represented by axis-aligned disjoint rectangles or boxes. Two vertices are adjacent if and only if their corresponding boxes see each other along a small axis-parallel cylinder. We concentrate on lower and upper bounds for the size of the largest complete graph that can be represented. In particular, we examine these bounds under certain restrictions: What can be said if we may only use boxes of a limited number of shapes? Some of the results presented are as follows: • There is a representation of K8 by unit boxes. • There is no representation of K10 by unit boxes. • There is a representation of K56, using 6 different box shapes. • There is no representation of K184 by general boxes. A special case arises for rectangle visibility graphs, where no two boxes can see each other in the x- or y-directions, which means that the boxes have to see each other in z-parallel direction. This special case has been considered before; we give further results, dealing with the aspects arising from limits on the number of shapes.
AN IMPROVED HYPERCUBE BOUND FOR MULTISEARCHING AND ITS APPLICATIONS
Authors: ATALLAH MIKHAIL J. 
Published: May 2003

We give a result that implies an improvement by a factor of log log n in the hypercube bounds for the geometric problems of batched planar point location, trapezoidal decomposition, and polygon triangulation. The improvements are achieved through a better solution to the multisearch problem on a hypercube, a parallel search problem where the elements in the data structure S to be searched are totally ordered, but where it is not possible to compare in constant time any two given queries q and q′. Whereas the previous best solution to this problem took O( log n( log log n)3) time on an n-processor hypercube, the solution given here takes O( log n( log log n)2) time on an n-processor hypercube. The hypercube model for which we claim our bounds is the standard one, SIMD, with O(1) memory registers per processor, and with one-port communication. Each register can store O( log n) bits, so that a processor knows its ID.
OPTIMAL LINE BIPARTITIONS OF POINT SETS
Authors: DEVILLERS OLIVIER , KATZ MATTHEW J. 
Published: May 2003

Let S be a set of n points in the plane. We study the following problem: Partition S by a line into two subsets Sa and Sb such that max{f(Sa), f(Sb)} is minimal, where f is any monotone function defined over 2S. We first present a solution to the case where the points in S are the vertices of a convex polygon and apply it to some common cases — f(S′) is the perimeter, area, or width of the convex hull of S′⊆S — to obtain linear solutions (or O(n log n) solutions if the convex hull of S is not given) to the corresponding problems. This solution is based on an efficient procedure for finding a minimal entry in matrices of some special type, which we believe is of independent interest. For the general case we present a linear space solution which is in some sense output sensitive. It yields solutions to the perimeter and area cases that are never slower and often faster than the best previous solutions.
IMMOBILIZING A SHAPE
Authors: CZYZOWICZ JUREK , STOJMENOVIC IVAN , URRUTIA JORGE 
Published: May 2003

Let shape P be any simply-connected set in the plane, bounded by a Jordan curve, that is not a circular disk. We say that a set of points I on the boundary of P immobilize the shape if any rigid motion of P in the plane causes at least one point of I to penetrate the interior of P. We prove that four points always suffice to immobilize any shape. For a large class of shapes, which includes polygons without parallel edges, three points are sufficient to immobilize. An O(n log n) algorithm is given that finds a set 3 points that immobilize a given polygon without parallel edges. The algorithm becomes linear for convex polygons. Some results are generalized for d-dimensional polytopes, where 2d points are always sufficient and sometimes necessary to immobilize.
THE OBJECT COMPLEXITY MODEL FOR HIDDEN-SURFACE REMOVAL
Authors: GROVE EDWARD F. , MURALI T. M. , VITTER JEFFREY SCOTT 
Published: May 2003

We define a new model of complexity, called object complexity, for measuring the performance of hidden-surface removal algorithms. This model is more appropriate for predicting the performance of these algorithms on current graphics rendering systems than the standard measure of scene complexity used in computational geometry. We also consider the problem of determining the set of visible windows in scenes consisting of n axis-parallel windows in ℝ3. We present an algorithm that runs in optimal Θ(n log n) time. The algorithm solves in the object complexity model the same problem that Bern3 addressed in the scene complexity model.
ON PIERCING SETS OF AXIS-PARALLEL RECTANGLES AND RINGS
Authors: SEGAL MICHAEL 
Published: May 2003

We consider the p-piercing problem for axis-parallel rectangles. We are given a collection of axis-parallel rectangles in the plane and wish to determine whether there exists a set of p points whose union intersects all the given rectangles. We present efficient algorithms for finding a piercing set (i.e, a set of p points as above) for values of p=1,2,3,4,5. The result for 4 and 5-piercing improves an existing result of O(n log 3 n) and O(n log 4 n) to O(n log n) time. The result for 5-piercing can be applied find an O(n log 2 n) time algorithm for planar rectilinear 5-center problem, in which we are given a set S of n points in the pane, and wish to find 5 axis-parallel congruent squares of smallest possible size whose union covers S. We improve the existing algorithm for general (but fixed) p to O(np-4 log n) running time, and we also extend our algorithms to higher dimensional space. We also consider the problem of piercing a set of rectangular rings.
SKEW VORONOI DIAGRAMS
Authors: AICHHOLZER OSWIN , AURENHAMMER FRANZ , CHEN DANNY Z. , LEE D. T. , PAPADOPOULOU EVANTHIA 
Published: May 2003

On a tilted plane T in three-space, skew distances are defined as the Euclidean distance plus a multiple of the signed difference in height. Skew distances may model realistic environments more closely than the Euclidean distance. Voronoi diagrams and related problems under this kind of distances are investigated. A relationship to convex distance functions and to Euclidean Voronoi diagrams for planar circles is shown, and is exploited for a geometric analysisis and a plane-sweep construction of Voronoi diagrams on T. An output-sensitive algorithm running in time O(n log h) is developed, where n and h are the numbers of sites and non-empty Voronoi regions, respectively. The all nearest neighbors problem for skew distances, which has certain features different from its Euclidean counterpart, is solved in O(n log n) time.
3-PIERCING OF d-DIMENSIONAL BOXES AND HOMOTHETIC TRIANGLES
Authors: ASSA EYAL , KATZ MATTHEW J. 
Published: May 2003

In the p-piercing problem, a set [Formula: see text] of nd-dimensional objects is given, and one has to compute a piercing set for [Formula: see text] of size p, if such a set exists. We consider several instances of the 3-piercing problem that admit linear or almost linear solutions: (i) If [Formula: see text] consists of axis-parallel boxes in ℛd, then a piercing triplet for [Formula: see text] can be found (if such a triplet exists) in O(n log n) time, for 3 ≤ d ≤ 5, and in [Formula: see text] time, for d ≥ 6. Based on the solutions for 3 ≤ d ≤ 5, efficient solutions are obtained to the corresponding 3-center problem — Given a set [Formula: see text] of n points of ℛd, compute the smallest edge length λ such that [Formula: see text] can be covered by the union of three axis-parallel cubes of edge length λ. (ii) If [Formula: see text] consists of homothetic triangles in the plane, or of 4-oriented trapezoids in the plane, then a piercing triplet can be found in O(n log n) time.
ON HAMILTONIAN TRIANGULATIONS IN SIMPLE POLYGONS
Authors: NARASIMHAN GIRI 
Published: May 2003

An n-vertex simple polygon P is said to have a Hamiltonian Triangulation if it has a triangulation whose dual graph contains a hamiltonian path. Such triangulations are useful in fast rendering engines in Computer Graphics. We give a new characterization of polygons with hamiltonian triangulations and use it to devise O(n log n)-time algorithms to recognize such polygons. We also give efficient algorithms for several related problems.
ON COMPUTING TRANSLATIONAL SWEPT VOLUMES
Authors: BAEK NAKHOON , SHIN SUNG-YONG , CHWA KYUNG-YONG 
Published: May 2003

A swept volume is a nice tool for solving various types of interference problems. Previous investigations have concentrated on sweeping an object along an arbitrary path that results in complex algorithms. We study the most fundamental motion, which is translation along a linear path. After analyzing the structure of the swept volume, we present an incremental algorithm for constructing a swept volume. Our algorithm takes O(n2α(n)+T c ) time where n is the number of vertices in the original object and T c is the time for handling face cycles. When the object is monotone with respect to the sweeping path, we show that its swept volume can be calculated in O(n) time after O(n log n+k) time preprocessing, where k is the number of regions in the arrangement of the projected image of the object.
AUTOMATIC RECONSTRUCTION OF 3D CAD MODELS FROM DIGITAL SCANS
Authors: BERNARDINI FAUSTO , BAJAJ CHANDRAJIT L. , CHEN JINDONG , SCHIKORE DANIEL R. 
Published: May 2003

We present an approach for the reconstruction and approximation of 3D CAD models from an unorganized collection of points. Applications include rapid reverse engineering of existing objects for use in a virtual prototyping environment, including computer aided design and manufacturing. Our reconstruction approach is flexible enough to permit interpolation of both smooth surfaces and sharp features, while placing few restrictions on the geometry or topology of the object. Our algorithm is based on alpha-shapes to compute an initial triangle mesh approximating the surface of the object. A mesh reduction technique is applied to the dense triangle mesh to build a simplified approximation, while retaining important topological and geometric characteristics of the model. The reduced mesh is interpolated with piecewise algebraic surface patches which approximate the original points. The process is fully automatic, and the reconstruction is guaranteed to be homeomorphic and error bounded with respect to the original model when certain sampling requirements are satisfied. The resulting model is suitable for typical CAD modeling and analysis applications.
A VISIBILITY-BASED PURSUIT-EVASION PROBLEM
Authors: GUIBAS LEONIDAS J. , LATOMBE JEAN-CLAUDE , LAVALLE STEVEN M. , LIN DAVID , MOTWANI RAJEEV 
Published: May 2003

This paper addresses the problem of planning the motion of one or more pursuers in a polygonal environment to eventually "see" an evader that is unpredictable, has unknown initial position, and is capable of moving arbitrarily fast. This problem was first introduced by Suzuki and Yamashita. Our study of this problem is motivated in part by robotics applications, such as surveillance with a mobile robot equipped with a camera that must find a moving target in a cluttered workspace. A few bounds are introduced, and a complete algorithm is presented for computing a successful motion strategy for a single pursuer. For simply-connected free spaces, it is shown that the minimum number of pursuers required is Θ( lg n). For multiply-connected free spaces, the bound is [Formula: see text] pursuers for a polygon that has n edges and h holes. A set of problems that are solvable by a single pursuer and require a linear number of recontaminations is shown. The complete algorithm searches a finite graph that is constructed on the basis of critical information changes. It has been implemented and computed examples are shown.
INTERSECTION PROBLEMS ON SEGMENTS UNDER BOUNDARY UPDATES WITH APPLICATION TO PERSISTENT LISTS
Authors: D'AMORE FABRIZIO , GIACCIO ROBERTO 
Published: May 2003

We consider some intersection problems on segments of [Formula: see text] in the partially dynamic setting called boundary update, where updates occur at the boundary of a given region. In particular, we maintain a set S of line segments under (boundary) insertions and deletions, such that, given a line segment ℓ either of fixed slope or originating from a fixed point and given a point p∈S∩ℓ, we can efficiently and orderly report all segments intersecting ℓ; insertions/deletions of segments occur at the boundaries of a vertical infinite slab. We provide practical algorithms requiring [Formula: see text] space, [Formula: see text] time per update and [Formula: see text] time per query, where k is the number of reported segments. Our results allow both modeling a moving window over a larger data set and answering segment intersection queries at an extra query cost of [Formula: see text]; also, they provide a methodology for designing access methods to temporal databases as well as a new kind of partially persistent lists.
DATA GENERATION FOR GEOMETRIC ALGORITHMS ON NON-UNIFORM DISTRIBUTIONS
Authors: MILLER GARY L. , TALMOR DAFNA , TENG SHANG-HUA 
Published: May 2003

We study the geometric properties of point sets that arise in the generation of bounded aspect-ratio meshes and present a constructive formulation to define distributions that allow arbitrary refinements. This formulation can be used to define distributions with one or more singularities, which do not occur in the uniform case but do occur in mesh generation for real-world applications. We give an efficient algorithm for the generation of a point set from these distributions. This work is in part motivated by the following observation: The Poisson distribution, points placed uniformly and randomly in a fixed dimension, is one of the most commonly used classes of data sets in the experimental evaluation of geometric algorithms and their implementation. However, despite its importance and interest to computational geometry, the Poisson distribution fails to be good test data for triangulation algorithms and software for mesh generation. Consequently, many implemented sequential and parallel algorithms are tuned to work efficiently for the uniform distribution, but fail to be efficient for nonuniform distributions. Even though the focus of our work is on the generation of data for Delaunay-based mesh algorithms, we hope that it will motivate further theoretical investigations on the generation of data for other geometric algorithms and software.
CALCULATION OF THE POWER LAW INDEX FOR A TIME SERIES BY MEANS OF ITS FRACTAL DIMENSION
Authors: YASUE SHINICHI , MUNAKATA KAZUOKI , KATO MASASHIGE , MORI SATORU 
Published: May 2003

The relationship between the power-law index for a time series and the fractal dimensions for both the original and the integrated time series, is investigated by using a numerical experiment. This relationship is extended and applied to the cosmic ray time series recorded at the deep underground site at Matsushiro. It is shown that we can use the present method in order to obtain the stable and reliable value of the power-law index of a time series, even if the time series has relatively large statistical fluctuations.
PERCOLATED CRACKS IN A SOLID CONTAINING MANY INITIAL DEFECTS
Authors: NISHIUMA SABUROU , HASEGAWA YUTAKA , MIYAZIMA SASUKE 
Published: May 2003

Hydrogen-induced fracture of steel is characterized by the formation of internal voids caused by hydrogen precipitation at an inclusion-matrix interface, followed by the formation of microcrack array under the superposed action of internal hydrogen pressure and external forces. The propagation of the hydrogen-induced fracture is considerably random and the fracture develops by stepwise linking of the microcracks. Crack growth in a solid containing many initial defects is studied by Monte Carlo simulation on a square lattice. Each initial defect is assumed to have two crack tips like the Griffith crack and percolated crack patterns in homogeneous medium are investigated. The effect of the density of the initial defects and the lattice size on percolation characteristics is also studied.
CAN STATISTICAL PHYSICS CONTRIBUTE TO THE SCIENCE OF ECONOMICS?
Authors: STANLEY MICHAEL H. R. , AMARAL LUÍS A. N. , BULDYREV SERGEY V. , HAVLIN SHLOMO , LESCHHORN HEIKO , MAASS PHILLIPP , SALINGER MICHAEL A. , EUGENE STANLEY H. 
Published: May 2003

In recent years, a breakthrough in statistical physics has occurred. Simply put, statistical physicists have determined that physical systems which consist of a large number of interacting particles obey universal laws that are independent of the microscopic details. This progress was mainly due to the development of scaling theory. Since economic systems also consist of a large number of interacting units, it is plausible that scaling theory can be applied to economics. To test this possibility we study the dynamics of firm size. This may help to build a more complete characterization of the nature and processes behind firm growth. To date, the study of firm dynamics has primarily focused on whether small firms on average have higher growth rates than large firms. To a lesser extent, attention has been placed on the relationship between firm size and variation in growth rate. Our research goes beyond these questions by looking at the relationship between numerous firm characteristics and the entire distribution of growth rates. Thus, it may provide a better understanding of the mechanisms behind firm dynamics. In contrast to previous studies, this research analyzes data over many time scales, instead of just a single time interval. From a scientific standpoint, this work could be useful because it will affect the formulation of firm modeling—one of the basic building blocks of all economic analysis. In addition, this work will have practical applications. For example, there are Federal policies that are designed to encourage small businesses. While such policies might be justified on grounds other than their contribution to growth, any systematic difference in the growth rates of small and large firms might be relevant for evaluating such policies. Also, there has traditionally been a concern that an excessive amount of economic activity might become concentrated in a small number of firms. A more detailed understanding of the firm growth process will provide evidence for whether such concerns have any scientific foundation.
Ice Cubes and Hot Water Bottles
Authors: Vrobel Susie 
Published: May 2003

Can the arrow of time we seem to perceive be explained by an overall increase in entropy? Several models suggest that the one macroscopic arrow of time which is associated with an overall increase in entropy may be identical to the arrows of time which are subject to our empirical knowledge. These models turn out to be difficult to maintain if one considers a freeze-frame picture (or one containing a minimal period of time) of nested systems of decreasing and increasing entropy. An observer who determines an arrow of time by measuring an increase or decrease in entropy must obviously be located somewhere. This observer position is in no case arbitrary — the individual situation of the observer determines, in each case, the outcome of the measurement. A fractal model suggests that the direction-generating agent is not to be found in a system's increase in entropy, but rather in the choice of the observer's position. A thought experiment involving infinitely nested ice cubes and hot water bottles leads to the conclusion that for such freeze-frames involving a minimal time span, the concepts of isolated and open systems (which otherwise are indispensable concepts for the discussion of entropy) are unsuitable. If one considers observers placed within different nested levels of the ice cube and hot water bottle universe, it will be impossible for these observers to determine whether the embedding systems add up to a total increase or decrease of entropy: we will never know whether the "outermost embedding nest" is an ice cube or a hot water bottle. An identification of the arrows of time which are subject to our empirical knowledge with an overall increase in entropy would not be plausible since there is no conceivable observer capable of monitoring the system as a whole. A fractal nested model suggests that there are nested arrows of time with differing directions. What direction we experience depends, in each case, entirely on the observer position chosen, i.e., the system we participate in. The only way to find out which arrow of time we are experiencing at the moment, say, in an ice cube, is to make contact with an observer in a hot water bottle — either with an observer in the hot water bottle embedding my ice cube or with one in the hot water bottle nested in my ice cube. The question: "Is there a way out?" must be discussed elsewhere. The arrow of time defined by an overall increase in entropy is not congruent with the arrows of time of our empirical knowledge.
Strange Attractors in an Antiferromagnetic Ising Model
Authors: Ananikian N. S. , Dallakian S. K. , Izmailian N. Sh. , Oganessyan K. A. 
Published: May 2003

The three-site antiferromagnetic Ising model on Husimi tree is investigated in an external magnetic field. The full bifurcation diagram, including chaos, of the magnetization is exhibited. With the "thermodynamic formalism", we investigate the antiferromagnetic Ising model in the case of fully developed chaos and describe the chaotic properties of this statistical mechanical system via the invariants characterizing a strange attractor. It is shown that this system displays in the chaotic region a phase transition at a positive "temperature" whereas in a class of maps close to x→ 4x(1-x), the phase transitions occur at negative "temperatures". The Frobenius-Perron recursion equation is numerically solved and the density of the invariant measure is obtained.