bluuebunny/crossref_metadata_2025_split huggingface dataset:
Building and navigating a network of local minima
Authors: Kim Seung‐Woo , Boley Daniel 
Published: August 2002

AbstractWe present a novel method that constructs and navigates a network of local minima of potential fields defined over multidimensional spaces. Though motivated by problems of motion planning for robotic manipulators, similar techniques have been proposed for use in other domains such as molecular chemistry and drug design. The method is based on building a roadmap of paths connecting local minima of a potential function. The novel approach consists of an up‐hill search strategy used to climb out of local minima and find new nearby local minima, without doubling back on previous local minima. With this up‐hill search strategy, one can find local minima otherwise difficult to encounter, and one can focus the search to specific local minima and specific directions from those local minima. The construction of the roadmap can be done in parallel with very little communication. We present extensive simulation results. © 2001 John Wiley & Sons, Inc.
Robustness of time‐scale learning of robot motions to uncertainty in acquired knowledge
Authors: Cheah C.C. 
Published: August 2002

AbstractA disadvantage of present iterative learning control algorithms is that they are generally applicable only in cases where a certain task is performed over and over again. Consequently, if knowledge or control inputs acquired from learning a task can be used on similar tasks, learning will be more efficient. Recently, several methods for constructing the control input of a new motion based on the control inputs acquired from previous learning of similar tasks have been proposed. However, these methods assumed that the perfect control inputs could be obtained from the previous learning. In practice, the control inputs could never be obtained exactly from learning in the presence of certain uncertainties such as disturbance and measurement noises. In addition, it is also not known for sure how the basic motion patterns should be chosen for learning. In this article, the robustness problem of the time‐scale learning control to uncertainty in the acquired learning control inputs is formulated and solved. From the analysis, certain new insights such as its implication to choices of basic motion patterns for time‐scale learning will be discussed. Simulation results of a 3‐link robot are presented to illustrate the analysis. © 2001 John Wiley & Sons, Inc.
Achieving a cooperative behavior in a dual‐arm robot system via a modular control structure
Authors: Caccavale Fabrizio , Natale Ciro , Siciliano Bruno , Villani Luigi 
Published: August 2002

AbstractIn this paper the problem of achieving a cooperative behavior in a dual‐arm robot system is addressed. A control strategy is conceived in which one robot is position controlled and devoted to task execution, whereas a suitable compliance is conferred to the end effector of the other robot to cope with unavoidable misalignment between the two arms and task planning inaccuracies. A modular control structure is adopted that allows the selection of the proper operating mode for each robot, depending on the task requirements. The proposed approach is experimentally tested in two different tasks involving the two robots in the laboratory setup. First, a parts‐mating task of peg‐in‐hole type is executed; the robot carrying the peg is position controlled, whereas the robot holding the hollow part is controlled to behave as a mechanical impedance. Then, a pressure‐forming task is executed, in which a disk‐shaped tool is required to align with a flat surface while exerting a desired pressure; in this case, the robot carrying the disk is position controlled, whereas the robot holding the surface is force controlled. © 2001 John Wiley & Sons, Inc.
Spatial variability of biotic and abiotic factors of the aquatic habitat in French Guiana
Authors: Tejerina‐Garro Francisco Leonardo , De Mérona Bernard 
Published: August 2002

AbstractResearch on tropical fish ecology in South America is focused mainly on the effect of environmental variables on aquatic organisms. Physical, chemical and biological characteristics of water measured at a local scale (local variables) are used, although geomorphological and hydrological factors measured at a regional scale (regional variables), as well as temporal and spatial heterogeneity, can also be considered. However, the use of this multi‐scale approach increases the perceived complexity, heterogeneity and variability of rivers. Thus, it is important to determine the magnitude of habitat variability and those parameters having the greatest influence on it. In this study, 28 stations distributed on 16 different rivers in French Guiana were sampled during high water at a meso spatial scale. Physical features of the rivers were sampled along an 800‐m stretch, where nine transversal transects were established on the main channel. At each river, 17 local and six regional variables were measured. Local variables relating to the physical characteristics of the channel bank and main channel and regional variables characterizing the whole basin and the position of the station in the basin were qualitatively and quantitatively described. All variables were submitted to multivariate analysis in order to determine their relative contribution to total variance. Two quantitative regional variables (drainage area upstream from stationandriver drainage basin), five quantitative local variables (channel width,water temperature,channel depth,Secchi transparencyandconductivity) and one qualitative local variable (channel substrate) were shown to differentiate the 16 rivers sampled. This result shows the poor contribution of qualitative variables compared with quantitative ones. Gradual change in qualitative variables is probably responsible for this poor contribution to the total variance; thus, the use of such variables is not possible for spatial habitat differentiation in this study. Copyright © 2001 John Wiley & Sons, Ltd.
Approximation algorithms for the covering Steiner problem
Authors: Konjevod Goran , Ravi R. , Srinivasan Aravind 
Published: August 2002

AbstractThe covering Steiner problem is a generalization of both thek‐MST and the group Steiner problems: given an edge‐weighted graph, with subsets of vertices called the groups, and a nonnegative integer value (called the requirement) for each group, the problem is to find a minimum‐weight tree spanning at least the required number of vertices of every group. When all requirements are equal to 1, this becomes the group Steiner problem, while if there is only one group which contains all vertices of the graph the problem reduces tok‐MST withkequal to the requirement of this unique group. We discuss two different (but equivalent) linear relaxations of the problem for the case when the given graph is a tree and construct polylogarithmic approximation algorithms based on randomized LP rounding of these relaxations. By using a probabilistic approximation of general metrics by tree metrics due to Bartal, our algorithms also solve the covering Steiner problem on general graphs with a further polylogarithmic worsening in the approximation ratio. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20:465–483, 2002
The scaling window of the 2‐SAT transition
Authors: Bollobás Béla , Borgs Christian , Chayes Jennifer T. , Kim Jeong Han , Wilson David B. 
Published: August 2002

AbstractWe consider the random 2‐satisfiability (2‐SAT) problem, in which each instance is a formula that is the conjunction ofmclauses of the formx∨y, chosen uniformly at random from among all 2‐clauses onnBoolean variables and their negations. Asmandntend to infinity in the ratiom/n→α, the problem is known to have a phase transition at αc=1, below which the probability that the formula is satisfiable tends to one and above which it tends to zero. We determine the finite‐size scaling about this transition, namely the scaling of the maximal windowW(n, δ)=(α−(n,δ), α+(n,δ)) such that the probability of satisfiability is greater than 1−δ for α<α−and is less than δ for α>α+. We show thatW(n,δ)=(1−Θ(n−1/3), 1+Θ(n−1/3)), where the constants implicit in Θ depend on δ. We also determine the rates at which the probability of satisfiability approaches one and zero at the boundaries of the window. Namely, form=(1+ε)n, where ε may depend onnas long as |ε| is sufficiently small and |ε|n1/3is sufficiently large, we show that the probability of satisfiability decays like exp(−Θ(nε3)) above the window, and goes to one like 1−Θ(n−1|ε|−3below the window. We prove these results by defining an order parameter for the transition and establishing its scaling behavior innboth inside and outside the window. Using this order parameter, we prove that the 2‐SAT phase transition is continuous with an order parameter critical exponent of 1. We also determine the values of two other critical exponents, showing that the exponents of 2‐SAT are identical to those of the random graph. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 18: 201–256 2001
Avoiding a giant component
Authors: Bohman Tom , Frieze Alan 
Published: August 2002

AbstractLete1, e′1;e2, e′2;…;ei, e′i;⋅⋅⋅ be a sequence of ordered pairs of edges chosen uniformly at random from the edge set of the complete graphKn(i.e. we sample with replacement). This sequence is used to form a graph by choosing at stagei,i=1,…, one edge fromei,e′ito be an edge in the graph, where the choice at stageiis based only on the observation of the edges that have appeared by stagei. We show that these choices can be made so thatwhpthe size of the largest component of the graph formed at stage 0.535nis polylogarithmic inn. This resolves a question of Achlioptas. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19, 75–85, 2001
Rain attenuation statistics from rain cell diameters and heights
Authors: Bryant G. H. , Adimula I. , Riva C. , Brussaard G. 
Published: August 2002

AbstractThe prediction of satellite link attenuation is generally based on the point rainfall rate for 0.01 per cent of the year. The physical quantity used to determine attenuation is rain rate, whereas the 0.01 per cent point is a more complex parameter, not obviously related to the dynamics of rain structure. The dynamics of the horizontal and vertical structure of rain are directly related to rain rate, rainfall volume, local geology and climate. If attenuation is to be predicted from rain rate it would be better to use a single parameter that remains substantially the same in most environments. This is not the case with the 0.01 per cent point. It is argued in this paper that a breakpoint in the rain‐rate exceedances occurs close to 105 mm/h. Rain can be divided at the breakpoint into two broad classes: below this point it is more uniformly distributed over the area of rainfall; above, it has an increasingly more complex horizontal varaiability, with intense rain columns embedded in a background of less intense rain. By replacing the climatic zone dependent 0.01 per cent point rain rate with the fixed rain rate of 105 mm/h, a model for attenuation calculation can be derived that relates the mechanics of the physical processes to rain rate and elevation angle. The model has been developed and tested against the ITU‐R model using the full measured rain‐rate exceedances for each site in the ITU‐R data bank. Attenuation exceedances have been shown to depend on the shape of the rain‐rate exceedance curve, whereas the ITU‐R model generates the same curve shape for all sites, because it uses only one rain rate,R0.01. The new model performs at least as well as the ITU‐R model for temperate climates and considerably better for tropical climates. For sites with no measured rain rate it is recommended that a generalized rain‐rate exceedance curve be used, especially for tropical regions. Copyright © 2001 John Wiley & Sons, Ltd.
Doppler spread characteristics of satellite personal communication channels
Authors: Frigyes I. , Molnár B. G. , Vallet R. , Herczku Z. , Bodnár Z. 
Published: August 2002

AbstractThe paper presents a general description of Doppler characteristics of the complex LEO satellite (low earth orbit) to ground terminal channel of S‐PCS (satellite personal communication system). The difference between the terrestrial and satellite PCS radio channels is pointed out. It is shown that in the latter there is a nonzero (average) Doppler shift and a spread being independent of the radial speed of the satellite; this is in contrast to terrestrial situations in which the average Doppler shift is zero. It is also shown that in contrast to terrestrial situations there is no unique relation between the incoming ray angle of arrival and Doppler shift. Doppler spectrum is computed for a realistic distribution of scatterers close to the ground terminal; the spectral density is proportional to 1/ν3if the ground terminal is stationary, whereνdenotes the Doppler frequency. Copyright © 2001 John Wiley & Sons, Ltd.
Topological design, routing and capacity dimensioning for ISL networks in broadband LEO satellite systems
Authors: Werner Markus , Frings Jochen , Wauquiez Frédéric , Maral Gérard 
Published: August 2002

AbstractThis paper considers the network design of intersatellite link (ISL) networks in broadband LEO satellite systems, where the major challenge is the topology dynamics. First, a general method to design convenient ISL topologies for connection‐oriented operation is presented, and a reference topology for numerical studies is derived. A permanent virtual topology is then defined on top of the orbiting physical one, thus forming a framework for discrete‐time dynamic traffic routing. On this basis, heuristic and optimization approaches for the combined routing and dimensioning task, operating on discrete time steps, are presented and their performance is numerically compared. It is shown that minimizing the worst‐case link capacity is an appropriate target function, which can be formulated as linear optimization problem with linear constraints. Using linear programming (LP) techniques, the dimensioning results are clearly better than with simple heuristic approaches. Copyright © 2001 John Wiley & Sons, Ltd.
Propagation considerations and fading countermeasures for mobile multimedia services
Authors: Jahn Axel 
Published: August 2002

AbstractThis paper presents a summary of land mobile satellite (LMS) channel characteristics derived from several measurement campaigns. Narrowband and wideband measurements allow a broad interpretation of the LMS channels. Channel models and its parameters have been derived from the measured data as well. Furthermore, the impact of the LMS channel on the communication service is investigated and possible countermeasures are discussed. Link margins, power control schemes and satellite diversity can compensate the fading on the transmission links. The benefit of adaptive receivers and the dependence on the signal bandwidth are investigated, too. Copyright © 2001 John Wiley & Sons, Ltd.
Posture estimation based on motion and structure models
Authors: Ogaki Kenichi , Iwai Yoshio , Yachida Masahiko 
Published: August 2002

AbstractSensing of human motion is very important for human–computer interactive applications such as virtual reality, gesture recognition, and communication. A vision system is suitable for human–computer interaction since this involves passive sensing and the system can estimate the motion of the user without any discomfort for the user. In this paper, we propose an algorithm for fast posture estimation of the user from an image sequence by using the position information of the hands and head. Our algorithm is founded on a model‐based method. The parameters of a geometric model are calculated from human kinematics. It is inadequate to obtain a unique solution from the image information such as position of the head and hands. The unknown parameters are predicted by the motion models and the previous posture parameters, then the unknown parameters are adjusted by a minimization method. We present experimental results to evaluate our proposed method in simulation and with real images. © 2001 Scripta Technica, Syst Comp Jpn, 32(4): 48–58, 2001
A color image compression scheme based on the adaptive orthogonalized transform, accelerated by improvement of the dictionary
Authors: Miura Takashi 
Published: August 2002

AbstractThe paper proposes an improvement of coding performance for a color image compression scheme based on the adaptive orthogonalized transform (AOT). The paper proposes that the performance of the coder will be accelerated by reducing the dictionary size to 25% and by maintaining the approximation gain of the LBG algorithm by virtue of the fact that the AOT increases the approximation gain of the dictionary. The effectiveness of the proposal is confirmed by numerical experiments. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(8): 1–8, 2002; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/scj.10218
Analysis and recognition of a human head's movement from an image sequence
Authors: Abe Yuichi , Hagiwara Masafumi 
Published: August 2002

AbstractIn this paper, we propose a method to analyze and recognize human head movements from monocular image sequences based on few constraints. First, the background image photographed beforehand is used to extract the human region from the image sequence. Next, the skin‐colored regions are extracted, and the low brightness and low saturation pixels are set as the candidate eye regions. Then the face region is determined from the multiple skin‐colored regions and the hair region is extracted based on the face region. Finally, the left and right eye regions are determined from the candidate eye regions. Thus, effective information for posture estimation such as the eye positions, face region, and hair region is extracted from the input image. A genetic algorithm (GA) is applied to fit the extracted information to a 3D head model and estimate the head posture. By creating an approximate 3D head model, the system adapts to an indeterminate large number of humans. Since an image sequence is input, the information in the previous image can be used. Thus, the possible human movements and the angles of the joints area prioriknowledge and are reflected in the parameters. The lack of information for the 3D posture estimation problem from a monocular image sequence is alleviated. © 2001 Scripta Technica, Syst Comp Jpn, 32(5): 36–45, 2001
3D space coding using virtual object surface
Authors: Takano Takahide , Naemura Takeshi , Harashima Hiroshi 
Published: August 2002

AbstractVisual information in 3D space has become the subject of much research in fields like 3D image communications and virtual reality. The huge amount of visual information in 3D space, however, makes the establishment of an efficient compression technique indispensable. In this regard, the authors have already proposed the concept of “space coding” that makes use of the redundancy in space itself, and have been investigating a specific coding technique that uses a multidimensional discrete cosine transform (DCT). In this paper, we extend this technique and propose a new coding technique that takes the structural characteristics of the object into account. To be more specific, we propose the concept of a “virtual object surface” as a technique for describing an object in structural terms taking compression rate into account, and attempt to improve coding efficiency with this technique. We also describe experiments performed to compare this technique with other techniques, and demonstrate the feasibility of the proposed technique on the basis of the results obtained. In addition, we examine a coding technique for performing high‐speed image synthesis from compressed data. © 2001 Scripta Technica, Syst Comp Jpn, 32(12): 47–59, 2001
Development of a diagnostic supporting tool for a circulatory system model of living body
Authors: Asami Ken'ichi , Kitamura Tadashi 
Published: August 2002

AbstractThe purpose of this research is to develop a computer‐aided tool for diagnostic and educational support of the living‐body circulatory system using the Human model devised by Coleman. The Human model is a dynamic model described by simultaneous differential equations, and consists of 25 physiological modules, such as the cardiovascular system, respiratory control, and kidney function, whose variables are exchanged with each other in order to emulate human‐body circulatory phenomena. For application of the human model to diagnosis and education, the supporting tool should have the capability of qualitative analysis to explain the causal relationships of numerical values of relevant variables in the model. We develop a supporting function to analyze the hierarchical structure of variables and parameters. The tool can be used to diagnose the causes of an unusual variable by path tracking in the human model. Furthermore, this supporting tool provides for editing of mathematical expressions for the purpose of validating the model. © 2001 Scripta Technica, Syst Comp Jpn, 32(14): 1–11, 2001
A temporal link mechanism for hypermedia broadcasting
Authors: Sumiya Kazutoshi , Noda Reiko , Tanaka Katsumi 
Published: August 2002

AbstractWe propose in this paper a time‐dependent link scheme for hypermedia. The management of the links accompanying updates in hypermedia is a major subject; in particular, it is an important problem in hypermedia dealing with content which depends on time. This scheme will realize the dynamic creation and expiration functions of links as well as the automatic link control function. We have packaged a prototype system called Mille‐feuille using the proposed time‐dependent link scheme and have confirmed the scheme's validity. This scheme can also be realized by using the extensible markup language (XML). © 2001 Scripta Technica, Syst Comp Jpn, 32(14): 54–66, 2001
A group learning support system enhancing the externalization of thinking
Authors: Kusunoki Fusako , Sugimoto Masanori , Hashizume Hiromichi 
Published: August 2002

AbstractThis paper discusses a group learning support system that promotes the externalization of thinking and sharing of understanding. The proposed system has the following two features. (1) Game characteristics are introduced in order to motivate the participation of the learners. (2) By combining a board game with computer simulation, externalization of thinking and sharing of understanding are supported. The effectiveness of the proposed system was evaluated experimentally in a primary school. The results confirmed the effectiveness of the proposed system. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(6): 93–100, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1136
Part of speech tagging with min‐max modular neural networks
Authors: Ma Qing , Lu Bao‐Liang , Isahara Hitoshi , Ichikawa Michinori 
Published: August 2002

AbstractA parts of speech (POS) tagging system using neural networks has been developed by Ma and colleagues. This system can tag unlearned data with a much higher accuracy than that of the Hidden Markov Model (HMM), which is the most popular method of POS tagging. It does so by learning a small Thai corpus on the order of 10,000 words that are ambiguous as to their POSs. However, the three‐layer perceptron used in the system has slow convergence and low learning accuracy even on such a small amount of data. It is therefore difficult to improve accuracy by incrementing the epoch of learning or by increasing the amount of learning data. To solve this problem, the tagging system of this paper makes use of the min‐max modular (M3) neural network of Lu and colleagues. This new system learns faster and has a higher learning accuracy compared with the old one, by decomposing large, complicated POS tagging problems into many smaller, easier problems. Learning accuracy can be improved by using the same learning data and larger data sets can be learned, which results in a much higher tagging accuracy. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(7): 30–39, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1139