bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantization of the ab initio nonadiabatic coupling matrix: The C2H molecule as a case study
Authors: Baer Michael , Mebel Alexander M.
Published: August 2002

The observation that, for a given sub‐Hilbert space, diabatic potentials, just like adiabatic potentials, have to be single‐valued in configuration space led to the unavoidable conclusion that the relevant nonadiabatic coupling matrix (i.e., the matrix that contains the vectorial electronic nonadiabatic coupling terms) has to be quantized along any contour in configuration space. In the present article this statement is tested with respect to the three (excited) states of the C2H molecule, i.e., the 22A′, 32A′, and 42A′ states. For this purpose ab initio electronic nonadiabatic coupling matrices were calculated along various contours surrounding the relevant conical intersections (one conical intersection between the 22A′ and 32A′ states and two conical intersections between the 32A′ and 42A′ states). Employing the line‐integral technique it was shown that as long as the contour that surrounds the (2,3) conical intersection is close enough to the CI and avoids the two (3,4) conical intersections, the 2×2 nonadiabatic coupling matrices are quantized. However they fail to be quantized for contours that also surround one or two of the other conical intersections. In this case one is obliged to employ the three‐state nonadiabatic coupling matrix. Doing that, it was shown that it is the 3×3 matrices that satisfy the quantization condition. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
A mass spectrometric study of Al2O3‐SiO2 melts using a Knudsen cell
Authors: Björkvall Johan , Stolyarova Valentina L.
Published: August 2002

The thermodynamic activities of SiO2 in Al2O3‐SiO2 liquid slags were measured by the high‐temperature Knudsen cell mass spectromeric method in the present work. The measurements were carried out in the temperature range 1863–2169 K. Tungsten crucibles were used to hold the slags. The system was calibrated using a CaF2 standard. The mass spectra obtained for pure SiO2 were in agreement with earlier data. The activities of silica, measured in the present work at 2150 K, show a slight negative deviation at very low alumina mole fractions which changed to a positive deviation at higher alumina contents. The activity values are in reasonable agreement with the assessment carried out by Hillert et al. The results were analysed on the basis of a slag model developed earlier at KTH, Stockholm. The present results are found to be compatible with the phase diagram proposed by Klug et al. Copyright © 2001 John Wiley & Sons, Ltd.
Study of bradykinin metabolism in human and rat plasma by liquid chromatography with inductively coupled plasma mass spectrometry and orthogonal acceleration time‐of‐flight mass spectrometry
Authors: Marshall Peter , Heudi Olivier , Mckeown Stephen , Amour Augustin , Abou‐Shakra Fadi
Published: August 2002

Bradykinin is a small peptide that acts mainly as a hormone by activating specific receptors that confer protection against the development of hypertension. The efficacy of bradykinin is influenced by the activities of various kininases present in plasma and blood. In this study, both human and rat plasma were incubated with a labelled form of bradykinin (at 4 and 12.5 µM), that will be referred to as bromobradykinin. The metabolic fate of bromobradykinin was monitored by liquid chromatography coupled to an orthogonal acceleration time‐of‐flight mass spectrometer (oaTOF). Quantification measurements of the bromine‐containing metabolites were performed on‐line, via flow splitting, by inductively coupled plasma mass spectrometry (ICPMS). The data obtained highlighted that the mechanism(s) of bradykinin metabolism in human and rat plasma are different, with the metabolism of bradykinin in rat plasma being much more aggressive than that observed in human plasma. In addition to the known bradykinin metabolites, e.g. [1,5], [1,7] from ACE, [1,8] from carboxypeptidase and [2,9] from aminopeptidase activity, we have identified the presence of new bradykinin metabolites in both human and rat plasma. These have been identified as fragment [5], the amino acid phenylalanine, which was present in both the human and rat plasma and the fragments [2,8] and [4,8] in rat plasma. To our knowledge it is the first time that these fragments have been recorded in human and rat plasma. The occurrence of these new fragments provides evidence for the presence of potentially new enzymes and mechanisms of bradykinin metabolism.

The method described here provides a powerful technique for monitoring the activity of the many kininases involved in bradykinin metabolism such as ACE (angiotensin I converting enzyme), carboxypeptidase N and aminopeptidase P. In addition, this procedure could be used as a screening assay for selecting and monitoring the actions of inhibitors of the enzymes implicated in bradykinin metabolism directly in plasma or serum. Copyright © 2002 John Wiley & Sons, Ltd.
Pyrolysis‐gas chromatography/mass spectrometry of fractions separated from a low‐temperature coal tar: an attempt to develop a general method for characterising structures and compositions of heavy hydrocarbon liquids
Authors: Islas C. A. , Suelves I. , Carter J. F. , Li W. , Morgan T. J. , Herod A. A. , Kandiyoti R.
Published: August 2002

A low‐temperature coal tar has been fractionated by column chromatography into acetonitrile, pyridine and 1‐methyl‐2‐pyrrolidinone‐ (NMP) solubles. The tar and its fractions have been examined by pyrolysis‐gas chromatography/mass spectrometry (GC/MS). Fractionation by planar chromatography was also carried out for purposes of comparison. Molecular masses of the fractions were estimated by size‐exclusion chromatography (SEC), and bulk structural characterisation was carried out by 13C‐NMR and UV‐fluorescence spectrometry. SEC showed that the fractions shifted to progressively shorter elution times (higher apparent masses) with diminishing solubility, i.e. from acetonitrile to NMP solubles. UV‐fluorescence spectra showed parallel shifts to longer wavelengths and lower fluorescence quantum yields, indicating increasing sizes of aromatic ring systems and increasingly complex molecules. GC/MS analysis of the tar showed alkanes from C10 to C32 and extensive series of alkylated aromatics, phenols, indenes, naphthalenes, phenanthrenes and fluoranthenes. Pyrolysis‐GC/MS results for the acetonitrile solubles closely resembled the data for the tar sample, with extensive series of alkylated benzenes, phenols and naphthalenes as well as alkanes from C16 to C28. The pyridine‐soluble fraction showed no significant aromatic pyrolysis products and only relatively weak signals for alkanes between C16 and C27. The NMP‐soluble fraction showed even less overall signal, with no significant aromatic components and weak signals for alkanes between C21 and C25, even though 13C‐NMR analyses showed that approximately half of the carbon detected was aromatic. The aliphatics are assumed to provide bridging structures between polycyclic aromatic (PCA) ring systems. Copyright © 2002 John Wiley & Sons, Ltd.
Gas chromatography/mass spectrometric assay of endogenous cellular lipid peroxidation products: quantitative analysis of 9‐ and 10‐hydroxystearic acids
Authors: Bertucci C. , Hudaib M. , Boga C. , Calonghi N. , Cappadone C. , Masotti L.
Published: August 2002

A sensitive, specific, accurate and reproducible gas chromatography/mass spectrometry method was developed for the assay of 9‐ and 10‐hydroxystearic acids in samples obtained as cell extracts. The preparation of the samples required specific procedures to allow the analysis of both the free and the conjugated hydroxy acids as the corresponding methyl esters. The quantification used propyl‐paraben as the internal standard and monitoring of a specific fragment of each isomeric hydroxy acid methyl ester, and allowed quantification of the conjugate and the free fractions of both 9‐ and 10‐hydroxystearic acids. This method is suitable for identification and quantification (LOQ 1.8 and 4.4 ng, respectively) of these important metabolites of lipid peroxidation. In particular the development of an assay for the free 9‐hydroxystearic acid methyl ester makes the method a reliable analytical tool for investigations of the role of this metabolite in the mechanisms of tumour cell proliferation. Copyright © 2002 John Wiley & Sons, Ltd.
Application to routine analysis of a method to determine multiclass pesticide residues in fresh vegetables by gas chromatography/tandem mass spectrometry
Authors: Vidal J. L. Martínez , Arrebola F. J. , Mateu‐Sánchez M.
Published: August 2002

The use of gas chromatography/tandem mass spectrometry (GC/MS/MS) applied to determine multiple pesticide residues in fresh vegetables has been thoroughly studied. A single injection method to detect, confirm and quantify 54 multiclass pesticides has been developed and applied in a routine analysis laboratory. The proposed method consists of a rapid extraction of 15 g of vegetable sample with dichloromethane. An additional clean‐up step is not necessary even when injecting 10 µL of extract. Instead the gas chromatograph was fitted with a carbofrit inserted into the glass liner and a guard column. In addition, the detection mode chosen (MS/MS) provides additional selectivity. The method has been validated and applied to 1300 samples in a routine laboratory following specified quality criteria. The recovery efficiencies obtained for all the pesticides ranged between 70.2 and 110.8% at two different fortification levels. The relative standard deviation for quantification (RSD) was lower than 16.7% for all the compounds. Important experimental parameters, such as the conditioning of carbofrit, overload of the analytical column, and cleanliness of the ion trap, were evaluated for their influence on the performance of the method. Copyright © 2002 John Wiley & Sons, Ltd.
A review of genetic differences between limited and extensively passaged human cytomegalovirus strains
Authors: Prichard M. N. , Penfold M. E. T. , Duke G. M. , Spaete R. R. , Kemble G. W.
Published: August 2002

The complete genetic content of human cytomegalovirus (HCMV) has been difficult to determine, since most strains studied in the laboratory have been extensively passaged in human fibroblast cultures which can change the genetic content as well as the biological properties of the virus. Approximately 13 kb of novel DNA sequences located near the right edge of the unique long (UL) component of the genome has been discovered in Toledo, clinical isolates and certain stocks of Towne. This region of novel sequence, designated the UL/b′ region, encodes several interesting proteins including vCXC‐1, a potent IL‐8 homologue, and UL144, a member of the TNF receptor family. This region is missing from the prototypic laboratory variants of Towne and AD169. In contrast to Toledo and other low passage isolates which have relatively small repeats bracketing the UL component, the Towne and AD169 laboratory variants contain large (>10 kb) b/b′ repeats. The large size of these repeats in AD169 and Towne appear to have arisen as compensation for the loss of sequences from the UL/b′ region that existed in less passaged variants of these strains. Consequently, many of the haploid genes at the left edge of the prototypic wild‐type (wt) UL component are diploid in AD169 and Towne. We hypothesise that this plasticity of the genome at the right edge of the UL component results from extensive passage and adaptation to replication in fibroblasts in vitro. Further work will be required to understand the complete genetic content of wt HCMV. Copyright © 2001 John Wiley & Sons, Ltd.
Global optimization for robust control synthesis based on the Matrix Product Eigenvalue Problem
Authors: Yamada Yuji , Hara Shinji
Published: August 2002

In this paper, we propose a new formulation for a class of optimization problems which occur in general robust control synthesis, called the Matrix Product Eigenvalue Problem (MPEP):Minimize the maximum eigenvalue of the product of two block‐diagonal positive‐definite symmetric matrices under convex constraints. This optimization class falls between methods of guaranteed low complexity such as the linear matrix inequality (LMI) optimization and methods known to be NP‐hard such as the bilinear matrix inequality (BMI) formulation, while still addressing most robust control synthesis problems involving BMIs encountered in applications.

The objective of this paper is to provide an algorithm to find a global solution within any specified tolerance ε for the MPEP. We show that a finite number of LMI problems suffice to find the global solution and analyse its computational complexity in terms of the iteration number. We prove that the worst‐case iteration number grows no faster than a polynomial of the inverse of the tolerance given a fixed size of the block‐diagonal matrices in the eigenvalue condition. Copyright 2001 © John Wiley & Sons, Ltd.
Constrained robust sampled‐data control for nonlinear uncertain systems
Authors: Hu Li‐Sheng , Cao Yong‐Yan , Shao Hui‐He
Published: August 2002

In industrial process control, computer control, which makes the closed‐loop system a sampled‐data one containing both continuous‐ and discrete‐time signals, is widely used. In contrast with traditional approximation methods, sampled‐data synthesis, a direct digital controller design procedure without approximation, has received increasing attention during the past few years. However, many of the existing results cannot be applied to sampled‐data control design for the uncertain systems. In this paper, a result of robust asymptotic stability of sampled‐data systems with constraints on the state is presented based on a result on practical stability for these systems. Then the robust sampled‐data control for a class of uncertain nonlinear systems with constraints on the output is developed. The problem is formulated from vehicle steering control with constraint on the side slip angle of body. The result is described by some matrix inequalities which could be solved by an iterative algorithm based on the linear matrix inequality technique. Finally, a numerical example is presented to demonstrate the result. Copyright © 2002 John Wiley & Sons, Ltd.
A new approach for estimating controllable and recoverable regions for systems with state and control constraints
Authors: Yfoulis C. A. , Muir A. , Wellstead P. E.
Published: August 2002

In this paper the problem of estimating controllable and recoverable regions for classes of nonlinear systems in the presence of uncertainties, state and control constraints is considered. A new computational technique is proposed based upon a ray‐gridding idea in contrast to the usual gridding techniques. The new technique is also based on the positive invariance principle and the use of piecewise linear (PL) Lyapunov functions to generate polytopic approximations to the controllable/recoverable region with arbitrary accuracy. Various types of stabilizing controllers achieving certain trade‐offs between robustness, performance and safety, while respecting state and control constraints, can be easily generated. The technique allows the approximation of nonlinear systems viapiecewise linear uncertainmodels which reduces the conservatism associated withlinear uncertainmodels. Copyright © 2002 John Wiley & Sons, Ltd.
Generalization of the Nyquist robust stability margin and its application to systems with real affine parametric uncertainties
Authors: Baab Charles T. , Cockburn Juan C. , Latchman Haniph A. , Crisalle Oscar D.
Published: August 2002

The critical direction theory for analysing the robust stability of uncertain feedback systems is generalized to include the case of non‐convex critical value sets, hence making the approach applicable for a much larger class of relevant systems. A redefinition of the critical perturbation radius is introduced, leading to the formulation of a Nyquist robust stability measure that preserves all the properties of the previous theory. The generalized theory is applied to the case of rational systems with an affine uncertainty structure where the uncertain parameters belong to a real rectangular polytope. Necessary and sufficient conditions for robust stability are developed in terms of the feasibility of a tractable linear‐equality problem subject to a set of linear inequalities, leading ultimately to a computable Nyquist robust stability margin. A systematic and numerically tractable algorithm is proposed for computing the critical perturbation radius needed for the calculation of the stability margin, and the approach is illustrated via examples. Copyright © 2001 John Wiley & Sons, Ltd.
Bilateral parallel force/position teleoperation control
Authors: Hashtrudi‐Zaad Keyvan , Salcudean Septimiu E.
Published: August 2002

The extension of parallel force/position control to teleoperation systems is considered in this article. In the proposed four‐channel bilateral controller, higher priority is granted to position control at the master side and to force control at the slave side. The primary goal of this control architecture is the enhancement of force and position tracking performance in the presence of uncertainties in the system and environment. The stability and performance of the proposed controller is investigated by analyzing the three decoupled single‐degree‐of‐freedom systems obtained from decoupling and projecting the closed‐loop system dynamics onto the slave task‐space orthogonal directions. Experimental results demonstrate significant improvement in transparency. © 2002 Wiley Periodicals, Inc.
Robust tracking control of mobile robots in the presence of uncertainties in the dynamical model
Authors: Corradini M. L. , Orlando G.
Published: August 2002

In this article, the robust trajectory tracking problem for the dynamical model of a wheeled mobile robot has been solved using sliding mode control. The presence of bounded uncertainties (parameter variations and input disturbances) has been considered. The control policy makes use of two nonlinear sliding surfaces, able to ensure the robust asymptotic vanishing of the three tracking errors. The control law has been tested by simulation. The reported results show the effectiveness of the proposed control law. © 2001 John Wiley & Sons, Inc.
Using soft computing techniques for improving foot trajectories in walking machines
Authors: Garcia Elena , Gonzalez‐de‐Santos Pablo
Published: August 2002

Walking machines have been investigated during the last 40 years and some basic techniques of this field are already well known. However, some aspects still need to be optimized. For instance, speed seems to be one of the major shortcomings of legged robots; thus, improving leg speed has been chosen as the main aim of this work. Although some algorithms for optimizing trajectory control of robot manipulators already exist, we propose a more computationally efficient method that employs fuzzy set theory to involve real dynamic effects over leg motion instead of an inaccurate mathematical model. In this article, we improve leg speed by automatically tuning the acceleration of legs. For this purpose, we define fuzzy rules based on experiments and we find the optimal acceleration for every given trajectory. A simple fuzzy inference system is used to compute the required acceleration. It is based on five rules using three linguistic variables. Final results show that foot acceleration tuning for straight trajectory generation is a suitable method for achieving accurate, smooth and fast foot movements. Also it is shown that under some conditions average leg speed can be increased up to 100% using the control methods herein proposed. © 2001 John Wiley & Sons, Inc.
Development and application of wire‐actuated haptic interfaces
Authors: Melchiorri Claudio , Vassura Gabriele
Published: August 2002

Haptic devices are being used in ever more applications, ranging from training to education, entertainment, design, space experiments, and so on. In this paper, alternative solutions are presented for the mechanical design of such devices, different from the classical ones based on “rigid” kinematic chains. These solutions adopt actuated wires, and present some features that can be very useful in particular applications. Due to their mechanical construction, these devices offer some peculiar control problems, which must be properly addressed for their use. These aspects (and other possible applications) are discussed, and an example of such a device for visually impaired persons is illustrated. © 2001 John Wiley & Sons, Inc.
Haptic display for human interaction with virtual dynamic environments
Authors: Ruspini Diego , Khatib Oussama
Published: August 2002

Haptics is an emerging technology that permits direct “hands‐on” interaction with a virtual environment. A haptic device uses mechanical actuators to physically push a user's finger or hand to give the sensation that he or she would have when interacting with a real physical environment. These force feedback systems have many applications, from training a surgeon to perform an operation, to assisting a child in understanding the behavior of a lever or pulley. In this paper we discuss methods and techniques to allow realistic and robust haptic interactions between a human and a complex dynamic virtual environment. Beyond modeling object penetration constraints, this work demonstrates how shading, friction, texture, and dynamics can be generated to create compelling and realistic virtual worlds. © 2001 John Wiley & Sons, Inc.
Cube Ramsey numbers are polynomial
Authors: Lingsheng Shi
Published: August 2002

Let R(G) be the least integer p such that for all bicolorings of the edges of complete graph Kp, at least one of the monochromatic subgraphs contains a copy of G. We show that for any positive constant c and bipartite graph G=(U, V; E) of order n where the maximum degree of vertices in U is at most $c\,{\rm log}\,n,\,R(G) < n^{1+(c+\sqrt{c^2+4c})/2+o(1)}.$ In particular, this shows that the Ramsey number of the n‐cube Qn satisfies $R(Q_n)<2^{(3+\sqrt{5}n/2+o(n)}$ which improves the bound 2cn log n due to Graham, Rödl, and Ruciński. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 99–101, 2001
IP routing issues in satellite constellation networks
Authors: Wood L. , Clerget A. , Andrikopoulos I. , Pavlou G. , Dabbous W.
Published: August 2002

The growth in use of Internet‐based applications in recent years has led to telecommunication networks transporting an increasingly large amount of Internet Protocol (IP)‐based traffic. Proposed broadband satellite constellation networks, currently under development, will be required to transport IP traffic. A case can be made for implementing IP routing directly within the constellation network, in order to transport IP traffic well and to provide good support for IP multicast and for emerging IP‐based quality of service (QoS) guarantees. This paper examines strategies for implementing and operating IP routing effectively within satellite constellation networks, given known constraints on the constellation resulting from satellite mobility, global visibility, routing and addressing. Copyright © 2001 John Wiley & Sons, Ltd.
A new opportunity for EHF propagation experiments: the EXPRESS campaign with the satellite STENTOR
Authors: Lemorton Joël , Castanet Laurent , Huot Valéry , Marsault Thierry
Published: August 2002

STENTOR is a collaborative programme between CNES, France Telecom, Alcatel Space and Astrium Space. The STENTOR satellite is planned to be launched in the autumn of 2001. Apart from the Ku‐band telecommunication payload designed to test active antennas and digital transponders, an EHF payload funded by DGA (Délégation Générale pour l'Armement=French Ministry of Defence) will be devoted to propagation and transmission experiments. The transmission mission uses a 44/20 GHz transparent repeater and is aimed to test new signal processing methods in the context of future military satellite telecommunication systems. The propagation mission will consist of two high‐frequency beacons, the first one at 20.7 GHz and the second one at 41.4 GHz with a European and an Equatorial coverage. The propagation experiment called EXperimentation of PRopagation in the EHF‐band from STENTOR Satellite (EXPRESS) will be devoted to the evaluation of the influence of propagation impairments on future satellite communication systems and will provide a new opportunity for EHF experimenters. The objective of this paper is to give the information available on this project. Copyright © 2001 John Wiley & Sons, Ltd.
The distinction between key ideas in teaching school physics and key ideas in the discipline of physics
Authors: Deng Zongyi
Published: August 2002

The distinction between key ideas in teaching a high school science and key ideas in the corresponding discipline of science has been largely ignored in scholarly discourse about what science teachers should teach and about what they should know. This article clarifies this distinction through exploring how and why key ideas in teaching high school physics differ from key ideas in the discipline of physics. Its theoretical underpinnings include Dewey's (1902/1990) distinction between the psychological and the logical and Harré's (1986) epistemology of science. It analyzes how and why the key ideas in teaching color, the speed of light, and light interference at the high school level differ from the key ideas at the disciplinary level. The thesis is that key ideas in teaching high school physics can differ from key ideas in the discipline in some significant ways, and that the differences manifest Dewey's distinction. As a result, the article challenges the assumption of equating key ideas in teaching a high school science with key ideas in the corresponding discipline of science, and the assumption that having a college degree in science is sufficient to teach high school science. Furthermore, the article expands the concept of pedagogical content knowledge by arguing that key ideas in teaching high school physics constitute an essential component. © 2001 John Wiley & Sons, Inc. Sci Ed 85:263–278, 2001.
Application of reinforcement learning based on on‐line EM algorithm to balancing of acrobot
Authors: Yoshimoto Junichiro , Ishii Shin , Sato Masa‐aki
Published: August 2002

The acrobot is a two‐link robot, actuated only at the joint between the two links. It is a difficult task in reinforcement learning (RL) to control the acrobot because it has nonlinear dynamics and continuous state and action spaces. In this article, we discuss applying the RL to the task of balancing control of the acrobot. Our RL method has an architecture similar to the actor‐critic model. The actor is a controller that yields a control signal for the current state. The critic predicts the expected return in the future. The actor and the critic are approximated by normalized Gaussian networks, which are trained by an on‐line EM algorithm. We also introduce a new method to promote the critic's learning. Our computer simulation shows that our method is able to acquire fairly good control through a small number of learning trials. © 2001 Scripta Technica, Syst Comp Jpn, 32(5): 12–20, 2001
Keyword spotting using F0 contour information
Authors: Yamashita Yoichi , Iwahashi Daisuke , Mizoguchi Riichiro
Published: August 2002

Generally, keyword spotting is based on the phonemic information. Consequently, if the input speech contains a phoneme sequence which is similar to the keyword, it may be incorrectly detected as the keyword, even though the prosodic pattern such as accent differs greatly. In order to avoid such a false alarm, this paper presents a method where not only the phonemic information, but also the F0 information, are both used to determine the likelihood of the input speech as the keyword. The F0 contour of the keyword is registered beforehand as the template. The F0 contour of the input speech and the template are compared by DP matching, and the likelihood as the keyword is evaluated by the obtained dissimilarity and the phonemic likelihood. Based on an experiment using news broadcasts, it is seen that the false alarm rate is reduced by 30 to 50%, for the equivalent detection rate. © 2001 Scripta Technica, Syst Comp Jpn, 32(7): 52–61, 2001
Obstacle location estimation using planar projection stereopsis method
Authors: Onoguchi Kazunori , Takeda Nobuyuki , Watanabe Mutsumi
Published: August 2002

This paper presents a method in which moving obstacles such as pedestrians, bicycles, and automobiles are detected from a moving vehicle using images, and the locations of the obstacles are calculated stably in relation to the vehicle. In the proposed method, stereoptic images are projected on the estimated road plane, and a free‐space map is constructed without attempting matching between the stereoptic images. Then, the vanishing point of the motion (FOE) is estimated from the optical flow, and the moving obstacle area is extracted from the image based on the residual error. By projecting the moving obstacle area onto the free‐space map, the location of the moving obstacle relative to the moving vehicle is determined. In this method, neither tracking between frames nor matching search between stereoptic images is needed, and the location can be determined stably, even for objects with rapidly varying size in the image, or nonrigid objects with continuously changing shape. An experiment was performed in which the locations of moving obstacles such as pedestrians, bicycles, and automobiles were determined from the input image sequence obtained from a camera on a moving vehicle. The effectiveness of the proposed method was demonstrated. © 2001 Scripta Technica, Syst Comp Jpn, 32(14): 67–76, 2001
Tree‐based clustering for gaussian mixture HMMs
Authors: Kato Tsuneo , Kuroiwa Shingo , Shimizu Tohru , Higuchi Norio
Published: August 2002

Tree‐based clustering is an effective method for sharing the state of an HMM in which clustering is applied to a set of context‐dependent models with the phoneme context as the splitting condition. In past papers, the method has been restricted to the single Gaussian HMM. The single Gaussian HMM, however, is insufficient for representing the acoustic features, and an adequate topology (sharing of HMM state) will not necessarily be realized. Furthermore, in order to arrive at a state‐sharing model with the desired number of mixtures, the process of doubling the number of mixtures and the embedded training must be iterated after the tree‐based clustering, which increases the time for training. Consequently, this paper proposes a method in which the tree‐based clustering algorithm for the single Gaussian HMM is extended to the clustering of the mixed Gaussian HMM. The proposed method reduces the training time to approximately one‐third that of the conventional method of handling the single Gaussian HMM. A recognition experiment using a phone typewriter and a recognition experiment for continuous word demonstrate that the recognition rate is improved by one to two points. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(4): 40–49, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1118
Detection of moving objects using observer motion‐based optical flow estimation
Authors: Ebine Takumi , Hamada Nozomu
Published: August 2002

A scheme for detecting a moving object in a three‐dimensional environment from observed dynamic images by optical flow, based on the state of the motion of the observing system, is proposed in this paper. The usual optical flow constraint equations defined in an image coordinate system do not sufficiently satisfy the assumptions made in deriving them when the observing system is in motion. In this paper, optical flow constraint equations considering the motion of the observing system are first derived. In order to do this, a mapping converting the motion of a stationary environment image to linear trajectory signals is derived. The uniform velocity property of motion and the isotropic property of motion within a proximal area, which are basic assumptions of the block gradient method, can be satisfied by these. Next, a method of expressing the optical flow constraint equations after mapping by the gradient in the time dimension before mapping is presented. Finally, the residuals of the optical flow constraint equations are proposed as the evaluation quantity for the extraction of a moving object and their efficacy is shown. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(6): 83–92, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1135
A proposal of 2D artificial cellular neural network including nonvolatile unit
Authors: Hiratsu Daisuke , Nagao Tomoharu
Published: August 2002

We have investigated the evolutional optimization of the Artificial Cellular Neural Network (ACNN). ACNN is a kind of neural network model. Neural units in ACNN are placed on a lattice grid, connections in ACNN are allowed only between neighborhood units, and connection weights and threshold parameters can be set independently of other units. In ACNN, connection between far units does not exist. Thus, ACNN architecture is suitable for building as hardware. We have suggested an optimization method of ACNN using a genetic algorithm (GA). In this paper, we introduce the “nonvolatile” attribute into partial units of a 2D ACNN in order to get the ACNN to output suitable data in a certain situation that has a causal relationship with past input. As its exercise, we used Sutton's maze problem, which is well known in the field of reinforcement learning. We prepared a simulation environment in which a 2D ACNN makes decisions of action in Sutton's maze to demonstrate that a 2D ACNN which includes nonvolatile units has better signal processing ability than the usual 2D ACNN. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(7): 40–49, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1140
Improvement of numeral recognition using personal handwriting characteristics based on clustering
Authors: Hotta Yoshinobu , Naoi Satoshi , Suwa Misako
Published: August 2002

Correctly recognizing characters with peculiarities for each writer is a difficult problem. The process of absorbing variations in individual writing by creating an individual dictionary is also difficult when a writer is not specified and the total number of writers is large. In this paper the authors propose a method to improve the results of isolated character recognition in forms in which the same writer writes many characters by taking the characteristics of the writer's writing on a form as a character distribution in a character feature space. In concrete terms, the authors first perform isolated character recognition on all characters on the same form. Then, based on the results of isolated character recognition, clustering of input character groups is performed for each character category. Clusters which are very likely to include misrecognized characters from isolated character recognition are extracted based on the results of clustering. Then character categories in the extracted cluster are automatically amended based on the distance from all clusters in other categories. In the same fashion, automatic amending is performed for rejected characters. Based on experiments to evaluate handwritten numerals on OCR forms, the authors show that the precision of numeral recognition is improved by using this approach as a form of postprocessing for isolated character recognition. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(7): 104–113, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1146
Social and ecological destruction in the first class: a plausible social development scenario
Authors: Kaivo‐oja Jari
Published: August 2002

In a previous issue of Sustainable Development (Kaivo‐oja, 1999) some alternative scenarios of social development were presented. The following scenarios were discussed: (i) the deep ecology scenario, (ii) the strong sustainable development scenario, (iii) the weak sustainable development scenario, (iv) the boomsday scenario, (v) the doomsday scenario and (vi) the World Bank ‘policy tunnel’ scenario. In this article a plausible, seventh social development scenario is presented: ‘social and ecological destruction in the first class’. The basic idea of this scenario is presented in this paper. The author argues that this scenario should also be taken into consideration in the strategic discussion of potential sustainable development paths. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment.
Catalytic cooperation at the interface of physical mixtures of CaO and MgO catalysts during steam gasification of naphthalene
Authors: Alarcón Nelson , García Ximena , Centeno Miguel , Ruiz Patricio , Gordon Alfredo
Published: August 2002

Oxides CaO, MgO and a physical mixture of 10% CaO + 90% MgO were used as catalysts for the steam gasification of naphthalene. A synergistic effect in the conversion was observed with the mixture. Catalysts were characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and XPS techniques. Basicity was significant for CaO as compared to MgO and the mixture, but did not correlate with catalytic activity. Bidentate carbonate‐type formation, which remained even in the presence of steam at high temperature (1033 K), was observed on CaO. Carbonates on MgO and on the mixture are unidentate and disappeared when steam was present. Formates, carboxylic and aldehydic groups also were formed, at 723 K on MgO and at 423 K on the mixture and on CaO. These species disappeared at 873 and 1033 K for the mixture and CaO, respectively, thus indicating their greater stability on CaO than on the mixture and on the MgO. Deposition of carbonaceous matter on solids was observed. The order of the deposited content is mixture < MgO < CaO. No indication of mutual contamination by the metal composing the oxides was observed. A higher carbonate removal and less carbonaceous matter deposition were observed in CaO when in the mixture, as compared with CaO alone, suggesting a beneficial effect of MgO in the mixture. The synergistic effect observed using the 10% CaO + 90% MgO mixture was related to the inhibition of carbonaceous matter and carbonate formation on the catalysts. This inhibition is due to a catalytic cooperation between both oxides, as two separate phases. The presence of MgO is assumed to avoid the formation of stable bidentate carbonates on CaO, promoting instead unidentate species formation; this facilitates the gasification of naphthalene by steam. Copyright © 2001 John Wiley & Sons, Ltd.
Multivariate image analysis methods applied to XPS imaging data sets
Authors: Artyushkova Kateryna , Fulghum Julia E.
Published: August 2002

Recent improvements in imaging photoelectron spectroscopy enhance lateral and vertical characterization of heterogeneous samples at the cost of increasing complexity in the XPS data sets acquired. These imaging data sets require more sophisticated analysis methods than visual inspection if the data are to be interpreted effectively. Multivariate analysis (MVA) methods are increasingly utilized in surface spectroscopies to aid the analyst in interpreting the vast amount of information resulting from these multidimensional data set acquisitions.

In this work, image processing analysis methods are tested on XPS data sets acquired from polymer blends. Images from the blends, acquired as a function of composition, time or energy, provide multidimensional data sets for algorithm evaluation. Multivariate image analysis (MIA) methods such as scatter diagrams, principal component analysis (PCA) and classification methods are used to extract maps of pure components from degradation and images‐to‐spectra data sets. In some cases the MVA results can be compared directly with the XPS spectra or images, which provide a critical reference point. This work will demonstrate that additional information can result from the application of MIA methods, even when direct spectral or image interpretation is possible. Copyright © 2002 John Wiley & Sons, Ltd.
Estimation of an errors‐in‐variables regression model when the variances of the measurement errors vary between the observations
Authors: Kulathinal S. B. , Kuulasmaa Kari , Gasbarra Dario
Published: August 2002

It is common in the analysis of aggregate data in epidemiology that the variances of the aggregate observations are available. The analysis of such data leads to a measurement error situation, where the known variances of the measurement errors vary between the observations. Assuming multivariate normal distribution for the ‘true’ observations and normal distributions for the measurement errors, we derive a simple EM algorithm for obtaining maximum likelihood estimates of the parameters of the multivariate normal distributions. The results also facilitate the estimation of regression parameters between the variables as well as the ‘true’ values of the observations. The approach is applied to re‐estimate recent results of the WHO MONICA Project on cardiovascular disease and its risk factors, where the original estimation of the regression coefficients did not adjust for the regression attenuation caused by the measurement errors. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of failure time hierarchical data in the presence of competing risks with application to oral contraceptive pill use in Egypt
Authors: Ali Mohamed M. , Babiker Abdel G. , Cleland John G.
Published: August 2002

Problems of practical interest in the analysis of data on contraceptive use, from Demographic and Health Surveys (DHS), include the estimation of the cause‐specific probability of discontinuation by timet(the cumulative incidence function), in the presence of other competing causes and the evaluation of the effect of covariates on the cause‐specific hazards of discontinuation. Methods of analysis of failure time data with competing risks are by now fairly well developed in the case of a simple random sample. However, the data from the DHS are clustered by geographical areas and include multiple episodes per woman. For a marginal (population average) approach, we propose using methods developed for simple random samples with standard errors calculated using a double bootstrap to take account of the clustered hierarchical nature of the data. In the conditional approach, the cause‐specific hazards are modelled as log‐linear functions of the covariates conditional on random effects of clusters and women, using a three‐level multinomial discrete‐time logit model. The methods are applied to data from Egypt 1992 DHS on the oral contraceptive pill use. Copyright © 2001 John Wiley & Sons, Ltd.
Sure outcomes of random events: a model for clinical trials
Authors: Bouckaert A. , Mouchart M.
Published: August 2002

We consider the outcomes of a clinical trial as determined by one, or several, possibly hidden causes. This paper proposes a statistical model that allows such a distinction of causes not only for the main, or therapeutic, effects but also for the side, or toxic, effects. More specifically, we focus on trials where the effects are naturally dichotomized, that is, where the health of a patient has improved or not, and where a specific adverse effect has occurred or not. A case study provides an example of the way this model can help to solve some problems of suspected drug toxicity. Finally, the model is shown to be a part of a hierarchy of models and the way to select a best model is investigated. Copyright © 2001 John Wiley & Sons, Ltd.
Modelling survival data with a cured fraction using frailty models
Authors: Price Dionne L. , Manatunga Amita K.
Published: August 2002

Cure models have historically been utilized to analyse time‐to‐event data with a cured fraction. We consider the use of frailty models as an alternative approach to modelling such data. An attractive feature of the models is the allowance for heterogeneity in risk among those individuals experiencing the event of interest in addition to the incorporation of a cured component. Utilizing maximum likelihood techniques, we fit models to data concerning the recurrence of leukaemia among patients receiving autologous transplantation treatment. The analysis suggests that the gamma frailty mixture model and the compound Poisson improve on the fit of the leukaemia data as compared to the standard cure model. Copyright © 2001 John Wiley & Sons, Ltd.
Testing for elevated disease rates using smoothed estimates
Authors: Downer Robert G.
Published: August 2002

A method of testing for elevated disease rates using smoothed estimates is introduced for counts aggregated to a specific administrative level. A test statistic is developed based on an approximation to the smoothed estimate from a penalized multinomial likelihood and an approximate critical value is derived. Empirical investigation reveals that smoothing can increase the ability to detect elevated rates. The methods are applied to data on gastric cancer in Nova Scotia, Canada. Copyright © 2001 John Wiley & Sons, Ltd.
An alternative parameterization of the general linear mixture model for longitudinal data with non‐ignorable drop‐outs
Authors: Fitzmaurice Garrett M. , Laird Nan M. , Shneyer Lucy
Published: August 2002

This paper considers the mixture model methodology for handling non‐ignorable drop‐outs in longitudinal studies with continuous outcomes. Recently, Hogan and Laird have developed a mixture model for non‐ignorable drop‐outs which is a standard linear mixed effects model except that the parameters which characterize change over time depend also upon time of drop‐out. That is, the mean response is linear in time, other covariates and drop‐out time, and their interactions. One of the key attractions of the mixture modelling approach to drop‐outs is that it is relatively easy to explore the sensitivity of results to model specification. However, the main drawback of mixture models is that the parameters that are ordinarily of interest are not immediately available, but require marginalization of the distribution of outcome over drop‐out times. Furthermore, although a linear model is assumed for the conditional mean of the outcome vector given time of drop out, after marginalization, the unconditional mean of the outcome vector is not, in general, linear in the regression parameters. As a result, it is not possible to parsimoniously describe the effects of covariates on the marginal distribution of the outcome in terms of regression coefficients. The need to explicitly average over the distribution of the drop‐out times and the absence of regression coefficients that describe the effects of covariates on the outcome are two unappealing features of the mixture modelling approach. In this paper we describe a particular parameterization of the general linear mixture model that circumvents both of these problems. Copyright © 2001 John Wiley & Sons, Ltd.