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865

Setup cost and lead time reductions on stochastic inventory models with a service level constraint

The stochastic inventory models analyzed in this paper explore the problem of lead time associated with setup cost reductions for the continuous review and periodic review inventory models. For these two models with a mixture of backorders and lost sales, we respectively assume that their mean and variance of the lead time demand and protection interval (i.e., lead time plus review period) demand are known, but their probability distributions are unknown. We develop a minimax distribution free procedure to find the optimal solution-for each case

1436

Modelling tomographic cone-beam projection data from a polyhedral phantom

Analytical phantoms are used to generate projection data for testing reconstruction accuracy in computed axial tomography. A circular source locus (equivalent to rotating specimen with a fixed source) provides insufficient data for 'exact' reconstruction in cone-beam transmission tomography, thus phantom data are useful for studying the consequent errors and also for investigating alternative scanning loci and reconstruction techniques. We present an algorithm that can compute phantom cone-beam projection data from a phantom comprising geometrically defined polyhedra. Each polyhedron is defined as a set of polygons enclosing a volume of fixed linear attenuation coefficient. The algorithm works by projecting each polygon in turn onto the modelled detector array, which accumulates the product of source to polygon intersection distance (for the rays intersecting each detector element), linear attenuation coefficient and sign of projected polygon area (indicating whether rays enter or exit the polyhedron at this face). The phantom data are rotated according to the projection angle, whilst the source location and detector plane remain fixed. Polyhedra can be of simple geometric form, or complex surfaces derived from 3D images of real specimens. This algorithm is illustrated using a phantom comprising 989 238 polygons, representing an iso-surface generated from a microtomographic reconstruction of a piece of walrus tusk

978

On Implicit Euler for high-order high-index DAEs

The Implicit Euler method is seldom used to solve differential-algebraic equations (DAEs) of differential index r >or= 3, since the method in general fails to converge in the first r - 2 steps after a change of stepsize. However, if the differential equation is of order d = r - 1 >or= 1, an alternative variable-step version of the Euler method can be shown uniformly convergent. For d = r - 1, this variable-step method is equivalent to the Implicit Euler except for the first r - 2 steps after a change of stepsize. Generalization to DAEs with differential equations of order d > r - 1 >or= 1, and to variable-order formulas is discussed

616

An overview of modems

This paper describes cursory glance of different types of modems classified for application, range, line type, operating mode, synchronizing mode, modulation, etc., highly useful for all engineering students of communication, electrical, computer science and information technology students. This paper also describes the standards and protocols used and the future trend

69

Sensitivity calibration of ultrasonic detectors based using ADD diagrams

The paper considers basic problems related to utilization of ADD diagrams in calibrating sensitivity of ultrasonic detectors. We suggest that a convenient tool for solving such problems can be the software package ADD Universal. Version 2.1 designed for plotting individual ADD diagrams for normal and slanted transducers. The software is compatible with the contemporary operational system Windows-95(98). Reference signals for calibration are generated in a sample with cylindrical holes

653

Indexing-neglected and poorly understood

The growth of the Internet has highlighted the use of machine indexing. The difficulties in using the Internet as a searching device can be frustrating. The use of the term "python" is given as an example. Machine indexing is noted as "rotten" and human indexing as "capricious." The problem seems to be a lack of a theoretical foundation for the art of indexing. What librarians have learned over the last hundred years has yet to yield a consistent approach to what really works best in preparing index terms and in the ability of our customers to search the various indexes. An attempt is made to consider the elements of indexing, their pros and cons. The argument is made that machine indexing is far too prolific in its production of index terms. Neither librarians nor computer programmers have made much progress to improve Internet indexing. Human indexing has had the same problems for over fifty years

1206

The MAGNeT toolkit: design, implementation and evaluation

The current trend in constructing high-performance computing systems is to connect a large number of machines via a fast interconnect or a large-scale network such as the Internet. This approach relies on the performance of the interconnect (or Internet) to enable fast, large-scale distributed computing. A detailed understanding of the communication traffic is required in order to optimize the operation of the entire system. Network researchers traditionally monitor traffic in the network to gain the insight necessary to optimize network operations. Recent work suggests additional insight can be obtained by also monitoring traffic at the application level. The Monitor for Application-Generated Network Traffic toolkit (MAGNeT) we describe here monitors application traffic patterns in production systems, thus enabling more highly optimized networks and interconnects for the next generation of high-performance computing systems

1243

HPF/JA: extensions of High Performance Fortran for accelerating real-world applications

This paper presents a set of extensions on High Performance Fortran (HPF) to make it more usable for parallelizing real-world production codes. HPF has been effective for programs that a compiler can automatically optimize efficiently. However, once the compiler cannot, there have been no ways for the users to explicitly parallelize or optimize their programs. In order to resolve the situation, we have developed a set of HPF extensions (HPF/JA) to give the users more control over sophisticated parallelization and communication optimizations. They include parallelization of loops with complicated reductions, asynchronous communication, user-controllable shadow, and communication pattern reuse for irregular remote data accesses. Preliminary experiments have proved that the extensions are effective at increasing HPF's usability

94

Gearing up for CLS bank

Continuous-Linked Settlement, a dream of the foreign-exchange community for years, may finally become a reality by the end of 2002

985

Local activity criteria for discrete-map CNN

Discrete-time CNN systems are studied in this paper by the application of Chua's local activity principle. These systems are locally active everywhere except for one isolated parameter value. As a result, nonhomogeneous spatiotemporal patterns may be induced by any initial setting of the CNN system when the strength of the system diffusion coupling exceeds a critical threshold. The critical coupling coefficient can be derived from the loaded cell impedance of the CNN system. Three well-known 1D map CNN's (namely, the logistic map CNN, the magnetic vortex pinning map CNN, and the spiral wave reproducing map CNN) are introduced to illustrate the applications of the local activity principle. In addition, we use the cell impedance to demonstrate the period-doubling scenario in the logistic and the magnetic vortex pinning maps

552

Anatomy of the coupling query in a Web warehouse

To populate a data warehouse specifically designed for Web data, i.e. Web warehouse, it is imperative to harness relevant documents from the Web. In this paper, we describe a query mechanism called coupling query to glean relevant Web data in the context of our Web warehousing system called Warehouse Of Web Data (WHOWEDA). A coupling query may be used for querying both HTML and XML documents. Important features of our query mechanism are the ability to query metadata, content, internal and external (hyperlink) structure of Web documents based on partial knowledge, ability to express constraints on tag attributes and tagless segment of data, ability to express conjunctive as well as disjunctive query conditions compactly, ability to control execution of a Web query and preservation of the topological structure of hyperlinked documents in the query results. We also discuss how to formulate a query graphically and in textual form using a coupling graph and coupling text, respectively

1107

A knowledge-navigation system for dimensional metrology

Geometric dimensioning and tolerancing (GD&T) is a method to specify the dimensions and form of a part so that it will meet its design intent. GD&T is difficult to master for two main reasons. First, it is based on complex 3D geometric entities and relationships. Second, the geometry is associated with a large, diverse knowledge base of dimensional metrology with many interconnections. This paper describes an approach to create a dimensional metrology knowledge base that is organized around a set of key concepts and to represent those concepts as virtual objects that can be navigated with interactive, computer visualization techniques to access the associated knowledge. The approach can enable several applications. First is the application to convey the definition and meaning of GD&T over a broad range of tolerance types. Second is the application to provide a visualization of dimensional metrology knowledge within a control hierarchy of the inspection process. Third is the application to show the coverage of interoperability standards to enable industry to make decisions on standards development and harmonization efforts. A prototype system has been implemented to demonstrate the principles involved in the approach

1142

Fast and accurate leaf verification for dynamic multileaf collimation using an electronic portal imaging device

A prerequisite for accurate dose delivery of IMRT profiles produced with dynamic multileaf collimation (DMLC) is highly accurate leaf positioning. In our institution, leaf verification for DMLC was initially done with film and ionization chamber. To overcome the limitations of these methods, a fast, accurate and two-dimensional method for daily leaf verification, using our CCD-camera based electronic portal imaging device (EPID), has been developed. This method is based on a flat field produced with a 0.5 cm wide sliding gap for each leaf pair. Deviations in gap widths are detected as deviations in gray scale value profiles derived from the EPID images, and not by directly assessing leaf positions in the images. Dedicated software was developed to reduce the noise level in the low signal images produced with the narrow gaps. The accuracy of this quality assurance procedure was tested by introducing known leaf position errors. It was shown that errors in leaf gap as small as 0.01-0.02 cm could be detected, which is certainly adequate to guarantee accurate dose delivery of DMLC treatments, even for strongly modulated beam profiles. Using this method, it was demonstrated that both short and long term reproducibility in leaf positioning were within 0.01 cm (1 sigma ) for all gantry angles, and that the effect of gravity was negligible

1283

UPSILON: universal programming system with incomplete lazy object notation

This paper presents a new model of computation that differs from prior models in that it emphasizes data over flow control, has no named variables and has an object-oriented flavor. We prove that this model is a complete and confluent acceptable programming system and has a usable type theory. A new data synchronization primitive is introduced in order to achieve the above properties. Subtle variations of the model are shown to fall short of having all these necessary properties

693

Lifting factorization of discrete W transform

A general method is proposed to factor the type-IV discrete W transform (DWT-IV) into lifting steps and additions. Then, based on the relationships among various types of DWTs, four types of DWTs are factored into lifting steps and additions. After approximating the lifting matrices, we get four types of new integer DWTs (IntDWT-I, IntDWT-II, IntDWT-III, and IntDWT-IV) which are floating-point multiplication free. Integer-to-integer transforms (II-DWT), which approximate to DWT, are also proposed. Fast algorithms are given for the new transforms and their computational complexities are analyzed

1182

Optimization of the memory weighting function in stochastic functional self-organized sorting performed by a team of autonomous mobile agents

The activity of a team of autonomous mobile agents formed by identical "robot-like-ant" individuals capable of performing a random walk through an environment that are able to recognize and move different "objects" is modeled. The emergent desired behavior is a distributed sorting and clustering based only on local information and a memory register that records the past objects encountered. An optimum weighting function for the memory registers is theoretically derived. The optimum time-dependent weighting function allows sorting and clustering of the randomly distributed objects in the shortest time. By maximizing the average speed of a texture feature (the contrast) we check the central assumption, the intermediate steady-states hypothesis, of our theoretical result. It is proved that the algorithm optimization based on maximum speed variation of the contrast feature gives relationships similar to the theoretically derived annealing law

106

Quantum Zeno subspaces

The quantum Zeno effect is recast in terms of an adiabatic theorem when the measurement is described as the dynamical coupling to another quantum system that plays the role of apparatus. A few significant examples are proposed and their practical relevance discussed. We also focus on decoherence-free subspaces

945

Testing statistical bounds on entanglement using quantum chaos

Previous results indicate that while chaos can lead to substantial entropy production, thereby maximizing dynamical entanglement, this still falls short of maximality. Random matrix theory modeling of composite quantum systems, investigated recently, entails a universal distribution of the eigenvalues of the reduced density matrices. We demonstrate that these distributions are realized in quantized chaotic systems by using a model of two coupled and kicked tops. We derive an explicit statistical universal bound on entanglement, which is also valid for the case of unequal dimensionality of the Hilbert spaces involved, and show that this describes well the bounds observed using composite quantized chaotic systems such as coupled tops

143

An automated irradiation device for use in cyclotrons

Two cyclotrons are being operated at IPEN-CNEN/SP: one model CV-28, capable of accelerating protons with energies up to 24 MeV and beam currents up to 30 mu A, and three other particles; the other one, model Cyclone 30, accelerates protons with energy of 30 MeV and currents up to 350 mu A. Both have the objective of irradiating targets both for radioisotope production for use in nuclear medicine and general research. The development of irradiating systems completely automatized was the objective of this work, always aiming to reduce the radiation exposition dose to the workers and to increase the reliability of use of these systems

900

Mathematical models of functioning of an insurance company with allowance for the rate of return

Models of the functioning of insurance companies are suggested, when the free capital increases from interest at a certain rate. The basic characteristics of the capital of a company are studied in the stationary regime

592

Approximation theory of fuzzy systems based upon genuine many-valued implications - SISO cases

It is proved that the single input and single output (SISO) fuzzy systems based upon genuine many-valued implications are universal approximators. It is shown theoretically that fuzzy control systems based upon genuine many-valued implications are equivalent to those based upon t-norm implications, the general approach to construct fuzzy systems is given. It is also shown that defuzzifier based upon center of areas is not appropriate to the fuzzy systems based upon genuine many-valued implications

11

Does social capital determine innovation? To what extent?

This paper deals with two questions: Does social capital determine innovation in manufacturing firms? If it is the case, to what extent? To deal with these questions, we review the literature on innovation in order to see how social capital came to be added to the other forms of capital as an explanatory variable of innovation. In doing so, we have been led to follow the dominating view of the literature on social capital and innovation which claims that social capital cannot be captured through a single indicator, but that it actually takes many different forms that must be accounted for. Therefore, to the traditional explanatory variables of innovation, we have added five forms of structural social capital (business network assets, information network assets, research network assets, participation assets, and relational assets) and one form of cognitive social capital (reciprocal trust). In a context where empirical investigations regarding the relations between social capital and innovation are still scanty, this paper makes contributions to the advancement of knowledge in providing new evidence regarding the impact and the extent of social capital on innovation at the two decisionmaking stages considered in this study

54

Controls help harmonic spray do OK removing residues

Looks at how innovative wafer-cleaning equipment hit the market in a timely fashion thanks in part to controls maker Rockwell Automation

858

Recruiting and retaining women in undergraduate computing majors

This paper recommends methods for increasing female participation in undergraduate computer science. The recommendations are based on recent and on-going research into the gender gap in computer science and related disciplines. They are intended to work in tandem with the Computing Research Association's recommendations for graduate programs to promote a general increase in women's participation in computing professions. Most of the suggestions offered could improve the educational environment for both male and female students. However, general improvements are likely to be of particular benefit to women because women in our society do not generally receive the same level of support that men receive for entering and persisting in this field

1363

Heuristics for single-pass welding task sequencing

Welding task sequencing is a prerequisite in the offline programming of robot arc welding. Single-pass welding task sequencing can be modelled as a modified travelling salesman problem. Owing to the difficulty of the resulting arc-routing problems, effective local search heuristics are developed. Computational speed becomes important because robot arc welding is often part of an automated process-planning procedure. Generating a reasonable solution in an acceptable time is necessary for effective automated process planning. Several different heuristics are proposed for solving the welding task-sequencing problem considering both productivity and the potential for welding distortion. Constructive heuristics based on the nearest neighbour concept and tabu search heuristics are developed and enhanced using improvement procedures. The effectiveness of the heuristics developed is tested and verified on actual welded structure problems and random problems

1326

Verona Lastre: consolidation provides opening for a new plate vendor

Fewer companies than ever are manufacturing CTP plates. The market has become globalized, with just four big firms dominating the picture. To the Samor Group, however, globalization looked like an opportunity; it reasoned that many a national and local distributor would welcome a small, competitive, regional manufacturer. A couple of years ago it formed a company, Verona Lastre, to exploit that opportunity. Now Vela, as it's familiarly called, has launched its line of high-quality thermal plates and is busily lining up dealers in Europe and the Americas

773

Topology-reducing surface simplification using a discrete solid representation

This paper presents a new approach for generating coarse-level approximations of topologically complex models. Dramatic topology reduction is achieved by converting a 3D model to and from a volumetric representation. Our approach produces valid, error-bounded models and supports the creation of approximations that do not interpenetrate the original model, either being completely contained in the input solid or bounding it. Several simple to implement versions of our approach are presented and discussed. We show that these methods perform significantly better than other surface-based approaches when simplifying topologically-rich models such as scene parts and complex mechanical assemblies

736

The year of the racehorse [China Telecom]

Does China really offer the telecoms industry a route out of the telecoms slump? According to the Chinese government it has yet to receive a single application from foreign companies looking to invest in the country's domestic telecoms sector since the country joined the World Trade Organisation

1062

Fidelity of quantum teleportation through noisy channels

We investigate quantum teleportation through noisy quantum channels by solving analytically and numerically a master equation in the Lindblad form. We calculate the fidelity as a function of decoherence rates and angles of a state to be teleported. It is found that the average fidelity and the range of states to be accurately teleported depend on types of noises acting on quantum channels. If the quantum channels are subject to isotropic noise, the average fidelity decays to 1/2, which is smaller than the best possible value of 2/3 obtained only by the classical communication. On the other hand, if the noisy quantum channel is modeled by a single Lindblad operator, the average fidelity is always greater than 2/3

1027

Extracting straight road structure in urban environments using IKONOS satellite imagery

We discuss a fully automatic technique for extracting roads in urban environments. The method has its bases in a vegetation mask derived from multispectral IKONOS data and in texture derived from panchromatic IKONOS data. These two techniques together are used to distinguish road pixels. We then move from individual pixels to an object-based representation that allows reasoning on a higher level. Recognition of individual segments and intersections and the relationships among them are used to determine underlying road structure and to then logically hypothesize the existence of additional road network components. We show results on an image of San Diego, California. The object-based processing component may be adapted to utilize other basis techniques as well, and could be used to build a road network in any scene having a straight-line structured topology

70

IT security issues: the need for end user oriented research

Considerable attention has been given to the technical and policy issues involved with IT security issues in recent years. The growth of e-commerce and the Internet, as well as widely publicized hacker attacks, have brought IT security into prominent focus and routine corporate attention. Yet, much more research is needed from the end user (EU) perspective. This position paper is a call for such research and outlines some possible directions of interest

122

A formal framework for viewpoint consistency

Multiple viewpoint models of system development are becoming increasingly important. Each viewpoint offers a different perspective on the target system and system development involves parallel refinement of the multiple views. Viewpoint related approaches have been considered in a number of different guises by a spectrum of researchers. Our work particularly focuses on the use of viewpoints in open distributed processing (ODP) which is an ISO/ITU standardisation framework. The requirements of viewpoint modelling in ODP are very broad and, hence, demanding. Multiple viewpoints, though, prompt the issue of consistency between viewpoints. This paper describes a very general interpretation of consistency which we argue is broad enough to meet the requirements of consistency in ODP. We present a formal framework for this general interpretation; highlight basic properties of the interpretation and locate restricted classes of consistency. Strategies for checking consistency are also investigated. Throughout we illustrate our theory using the formal description technique LOTOS. Thus, the paper also characterises the nature of and options for consistency checking in LOTOS

961

Modular and visual specification of hybrid systems: an introduction to HyCharts

Visual description techniques are particularly important for the design of hybrid systems, because specifications of such systems usually have to be discussed between engineers from a number of different disciplines. Modularity is vital for hybrid systems not only because it allows to handle large systems, but also because it permits to think in terms of components, which is familiar to engineers. Based on two different interpretations for hierarchic graphs and on a clear hybrid computation model, we develop HyCharts. HyCharts consist of two modular visual formalisms, one for the specification of the architecture and one for the specification of the behavior of hybrid systems. The operators on hierarchic graphs enable us to give a surprisingly simple denotational semantics for many concepts known from statechart-like formalisms. Due to a very general composition operator, HyCharts can easily be composed with description techniques from other engineering disciplines. Such heterogeneous system specifications seem to be particularly appropriate for hybrid systems because of their interdisciplinary character

924

Dynamic testing of inflatable structures using smart materials

In this paper we present experimental investigations of the vibration testing of an inflated, thin-film torus using smart materials. Lightweight, inflatable structures are very attractive in satellite applications. However, the lightweight, flexible and highly damped nature of inflated structures poses difficulties in ground vibration testing. In this study, we show that polyvinylidene fluoride (PVDF) patches and recently developed macro-fiber composite actuators may be used as sensors and actuators in identifying modal parameters. Both smart materials can be integrated unobtrusively into the skin of a torus or space device forming an attractive testing arrangement. The addition of actuators and PVDF sensors to the torus does not significantly interfere with the suspension modes of a free-free boundary condition, and can be considered an integral part of the inflated structure. The results indicate the potential of using smart materials to measure and control the dynamic response of inflated structures

1046

A suggestion of fractional-order controller for flexible spacecraft attitude control

A controller design method for flexible spacecraft attitude control is proposed. The system is first described by a partial differential equation with internal damping. Then the frequency response is analyzed, and the three basic characteristics of the flexible system, namely, average function, lower bound and upper bound are defined. On this basis, a fractional-order controller is proposed, which functions as phase stabilization control for lower frequency and smoothly enters to amplitude stabilization at higher frequency by proper amplitude attenuation. It is shown that the equivalent damping ratio increases in proportion to the square of frequency

1003

Lob's theorem as a limitation on mechanism

We argue that Lob's Theorem implies a limitation on mechanism. Specifically, we argue, via an application of a generalized version of Lob's Theorem, that any particular device known by an observer to be mechanical cannot be used as an epistemic authority (of a particular type) by that observer: either the belief-set of such an authority is not mechanizable or, if it is, there is no identifiable formal system of which the observer can know (or truly believe) it to be the theorem-set. This gives, we believe, an important and hitherto unnoticed connection between mechanism and the use of authorities by human-like epistemic agents

881

Is diversity in computing a moral matter?

We have presented an ethical argument that takes into consideration the subtleties of the issue surrounding under-representation in computing. We should emphasize that there is nothing subtle about overt, unfair discrimination. Where such injustice occurs, we condemn it. Our concern is that discrimination need not be explicit or overt. It need not be individual-to-individual. Rather, it can be subtly built into social practices and social institutions. Our analysis raises ethical questions about aspects of computing that drive women away, aspects that can be changed in ways that improve the profession and access to the profession. We hope that computing will move towards these improvements

1347

A maximum-likelihood surface estimator for dense range data

Describes how to estimate 3D surface models from dense sets of noisy range data taken from different points of view, i.e., multiple range maps. The proposed method uses a sensor model to develop an expression for the likelihood of a 3D surface, conditional on a set of noisy range measurements. Optimizing this likelihood with respect to the model parameters provides an unbiased and efficient estimator. The proposed numerical algorithms make this estimation computationally practical for a wide variety of circumstances. The results from this method compare favorably with state-of-the-art approaches that rely on the closest-point or perpendicular distance metric, a convenient heuristic that produces biased solutions and fails completely when surfaces are not sufficiently smooth, as in the case of complex scenes or noisy range measurements. Empirical results on both simulated and real ladar data demonstrate the effectiveness of the proposed method for several different types of problems. Furthermore, the proposed method offers a general framework that can accommodate extensions to include surface priors, more sophisticated noise models, and other sensing modalities, such as sonar or synthetic aperture radar

1302

Dynamics of the firing probability of noisy integrate-and-fire neurons

Cortical neurons in vivo undergo a continuous bombardment due to synaptic activity, which acts as a major source of noise. We investigate the effects of the noise filtering by synapses with various levels of realism on integrate-and-fire neuron dynamics. The noise input is modeled by white (for instantaneous synapses) or colored (for synapses with a finite relaxation time) noise. Analytical results for the modulation of firing probability in response to an oscillatory input current are obtained by expanding a Fokker-Planck equation for small parameters of the problem-when both the amplitude of the modulation is small compared to the background firing rate and the synaptic time constant is small compared to the membrane time constant. We report the detailed calculations showing that if a synaptic decay time constant is included in the synaptic current model, the firing-rate modulation of the neuron due to an oscillatory input remains finite in the high-frequency limit with no phase lag. In addition, we characterize the low-frequency behavior and the behavior of the high-frequency limit for intermediate decay times. We also characterize the effects of introducing a rise time to the synaptic currents and the presence of several synaptic receptors with different kinetics. In both cases, we determine, using numerical simulations, an effective decay time constant that describes the neuronal response completely

757

Ultrafast compound imaging for 2-D motion vector estimation: application to transient elastography

This paper describes a new technique for two-dimensional (2-D) imaging of the motion vector at a very high frame rate with ultrasound. Its potential is experimentally demonstrated for transient elastography. But, beyond this application, it also could be promising for color flow and reflectivity imaging. To date, only axial displacements induced in human tissues by low-frequency vibrators were measured during transient elastography. The proposed technique allows us to follow both axial and lateral displacements during the shear wave propagation and thus should improve Young's modulus image reconstruction. The process is a combination of several ideas well-known in ultrasonic imaging: ultra-fast imaging, multisynthetic aperture beamforming, 1-D speckle tracking, and compound imaging. Classical beamforming in the transmit mode is replaced here by a single plane wave insonification increasing the frame rate by at least a factor of 128. The beamforming is achieved only in the receive mode on two independent subapertures. Comparison of successive frames by a classical 1-D speckle tracking algorithm allows estimation of displacements along two different directions linked to the subapertures beams. The variance of the estimates is finally improved by tilting the emitting plane wave at each insonification, thus allowing reception of successive decorrelated speckle patterns

712

Waiting-time distribution of a discrete-time multiserver queue with correlated arrivals and deterministic service times: D-MAP/D/k system

We derive the waiting-time distribution of a discrete-time multiserver queue with correlated arrivals and deterministic (or constant) service times. We show that the procedure for obtaining the waiting-time distribution of a multiserver queue is reduced to that of a single-server queue. We present a complete solution to the waiting-time distribution of D-MAP/D/k queue together with some computational results

839

Women in computing: what brings them to it, what keeps them in it?

Career stereotyping and misperceptions about the nature of computing are substantive reasons for the under representation of women in professional computing careers. In this study, 15 women who have work experience in several aspects of computing were asked about their reasons for entering computing, what they liked about working in computing, and what they disliked. While there are many common threads, there are also individual differences. Common reasons for choosing computing as a career included: exposure to computing in a setting which enabled them to see the versatility of computers; the influence of someone close to them; personal abilities which they perceived to be appropriate for a career in computing; and characteristics of such careers which appealed to them. Generally, women working in the field enjoy the work they are doing. Dislikes arising from their work experiences are more likely to be associated with people and politics than with the work they do-and they would like to have more female colleagues

804

Voltage control methods with grid connected wind turbines: a tutorial review

Within electricity grid networks it is conventional for large-scale central generators to both provide power and control grid node voltage. Therefore when wind turbines replace conventional power stations on a substantial scale, they must not only generate power, but also control grid node voltages. This paper reviews the basic principles of voltage control for tutorial benefit and then considers application of grid-connected wind turbines for voltage control. The most widely used contemporary wind turbine types are considered and further detail is given for determining the range of variables that allow control

841

Becoming a computer scientist

The focus of this report is pipeline shrinkage for women in computer science. We describe the situation for women at all stages of training in computer science, from the precollege level through graduate school. Because many of the problems discussed are related to the lack of role models for women who are in the process of becoming computer scientists, we also concern ourselves with the status of women faculty members. We not only describe the problems, but also make specific recommendations for change and encourage further study of those problems whose solutions are not yet well understood

1086

Some recent advances in validated methods for IVPs for ODEs

Compared to standard numerical methods for initial value problems (IVPs) for ordinary differential equations (ODEs), validated methods (often called interval methods) for IVPs for ODEs have two important advantages: if they return a solution to a problem, then (1) the problem is guaranteed to have a unique solution, and (2) an enclosure of the true solution is produced. We present a brief overview of interval Taylor series (ITS) methods for IVPs for ODEs and discuss some recent advances in the theory of validated methods for IVPs for ODEs. In particular, we discuss an interval Hermite-Obreschkoff (IHO) scheme for computing rigorous bounds on the solution of an IVP for an ODE, the stability of ITS and IHO methods, and a new perspective on the wrapping effect, where we interpret the problem of reducing the wrapping effect as one of finding a more stable scheme for advancing the solution

1457

A discontinuous Galerkin method for transient analysis of wave propagation in unbounded domains

A technique based on the discontinuous Galerkin finite element method is developed and applied to the derivation of an absorbing boundary condition for the analysis of transient wave propagation. The condition is exact in that only discretization error is involved. Furthermore, the computational cost associated with use of the condition is an order of magnitude lower than for conditions based on Green functions. The time-stepping scheme resulting from an implicit method in conjunction with this boundary condition appears to be unconditionally stable

1412

Arbortext: enabler of multichannel publishing

A company has a document-say, dosage instructions for a prescription drug or a troubleshooting sheet for a DVD drive. That document starts its life in a predictable format, probably Microsoft Word or WordPerfect, but then-to meet the needs of readers who nowadays demand access via multiple devices-the material has to be translated into many more formats: HTML, PageMaker, or Quark, possibly RTF, almost certainly PDF, and nowadays, next-generation devices (cell phones, handheld computers) also impose their own requirements. And what if, suddenly, the dosage levels change or new workarounds emerge to handle DVD problems? That's when a company should put in a call to Arbortext, a 20-year-old Ann Arbor, Michigan-based company that exists to solve a single problem: helping clients automate multichannel publishing

797

Adaptive wavelet methods. II. Beyond the elliptic case

This paper is concerned with the design and analysis of adaptive wavelet methods for systems of operator equations. Its main accomplishment is to extend the range of applicability of the adaptive wavelet-based method developed previously for symmetric positive definite problems to indefinite or unsymmetric systems of operator equations. This is accomplished by first introducing techniques (such as the least squares formulation developed previously) that transform the original (continuous) problem into an equivalent infinite system of equations which is now well-posed in the Euclidean metric. It is then shown how to utilize adaptive techniques to solve the resulting infinite system of equations. It is shown that for a wide range of problems, this new adaptive method performs with asymptotically optimal complexity, i.e., it recovers an approximate solution with desired accuracy at a computational expense that stays proportional to the number of terms in a corresponding wavelet-best N-term approximation. An important advantage of this adaptive approach is that it automatically stabilizes the numerical procedure so that, for instance, compatibility constraints on the choice of trial spaces, like the LBB condition, no longer arise

576

Application of Sugeno fuzzy-logic controller to the stator field-oriented doubly-fed asynchronous motor drive

This study deals with the application of the fuzzy-control theory to wound-rotor asynchronous motor with both its stator and rotor fed by two PWM voltage-source inverters, in which the system operates in stator field-oriented control. Thus, after determining the model of the machine, we present two types of fuzzy controller: Mamdani and Sugeno controllers. The training of the last one is carried out starting from the first. Simulation study is conducted to show the effectiveness of the proposed method

1123

A transactional asynchronous replication scheme for mobile database systems

In mobile database systems, mobility of users has a significant impact on data replication. As a result, the various replica control protocols that exist today in traditional distributed and multidatabase environments are no longer suitable. To solve this problem, a new mobile database replication scheme, the Transaction-Level Result-Set Propagation (TLRSP) model, is put forward in this paper. The conflict detection and resolution strategy based on TLRSP is discussed in detail, and the implementation algorithm is proposed. In order to compare the performance of the TLRSP model with that of other mobile replication schemes, we have developed a detailed simulation model. Experimental results show that the TLRSP model provides an efficient support for replicated mobile database systems by reducing reprocessing overhead and maintaining database consistency

1166

Embedding the outer automorphism group Out(F/sub n/) of a free group of rank n in the group Out(F/sub m/) for m > n

It is proved that for every n >or= 1, the group Out(F/sub n/) is embedded in the group Out(F/sub m/) with m = 1 + (n - 1)k/sup n/, where k is an arbitrary natural number coprime to n - 1

632

Modelling dependencies in paired comparison data a log-linear approach

In many Bradley-Terry models a more or less explicit assumption is that all decisions of the judges are independent. An assumption which might be questionable at least for the decisions of a given judge. In paired comparison studies, a judge chooses among objects several times, and in such cases, judgements made by the same judge are likely to be dependent. A log-linear representation for the Bradley-Terry model is developed, which takes into account dependencies between judgements. The modelling of the dependencies is embedded in the analysis of multiple binomial responses, which has the advantage of interpretability in terms of conditional odds ratios. Furthermore, the modelling is done in the framework of generalized linear models, thus parameter estimation and the assessment of goodness of fit can be obtained in the standard way by using e.g. GLIM or another standard software

677

Acts to facts catalogue

The paper shows a way to satisfy users' changing and specific information needs by providing the modified format-author-collaborators-title-series-subject (FACTS). catalogue instead of the traditional author-collaborator-title-series-subjects (ACTS) catalogue

1222

Mining the optimal class association rule set

We define an optimal class association rule set to be the minimum rule set with the same predictive power of the complete class association rule set. Using this rule set instead of the complete class association rule set we can avoid redundant computation that would otherwise be required for mining predictive association rules and hence improve the efficiency of the mining process significantly. We present an efficient algorithm for mining the optimal class association rule set using an upward closure property of pruning weak rules before they are actually generated. We have implemented the algorithm and our experimental results show that our algorithm generates the optimal class association rule set, whose size is smaller than 1/17 of the complete class association rule set on average, in significantly less time than generating the complete class association rule set. Our proposed criterion has been shown very effective for pruning weak rules in dense databases

1267

3D reconstruction from uncalibrated-camera optical flow and its reliability evaluation

We present a scheme for reconstructing a 3D structure from optical flow observed by a camera with an unknown focal length in a statistically optimal way as well as evaluating the reliability of the computed shape. First, the flow fundamental matrices are optimally computed from the observed flow. They are then decomposed into the focal length, its rate of change, and the motion parameters. Next, the flow is optimally corrected so that it satisfies the epipolar equation exactly. Finally, the 3D positions are computed, and their covariance matrices are evaluated. By simulations and real-image experiments, we test the performance of our system and observe how the normalization (gauge) for removing indeterminacy affects the description of uncertainty

919

Agents in e-commerce: state of the art

This paper surveys the state of the art of agent-mediated electronic commerce (e-commerce), especially in business-to-consumer (B2C) e-commerce and business-to-business (B2B) e-commerce. From the consumer buying behaviour perspective, the roles of agents in B2C e-commerce are: product brokering, merchant brokering, and negotiation. The applications of agents in B2B e-commerce are mainly in supply chain management. Mobile agents, evolutionary agents, and data-mining agents are some special techniques which can be applied in agent-mediated e-commerce. In addition, some technologies for implementation are briefly reviewed. Finally, we conclude this paper by discussions on the future directions of agent-mediated e-commerce

795

Approximation and complexity. II. Iterated integration

For pt. I. see ibid., no. 1, p. 289-95 (2001). We introduce two classes of real analytic functions W contained in/implied by U on an interval. Starting with rational functions to construct functions in W we allow the application of three types of operations: addition, integration, and multiplication by a polynomial with rational coefficients. In a similar way, to construct functions in U we allow integration, addition, and multiplication of functions already constructed in U and multiplication by rational numbers. Thus, U is a subring of the ring of Pfaffian functions. Two lower bounds on the L/sub infinity /-norm are proved on a function f from W (or from U, respectively) in terms of the complexity of constructing f

1385

Cache invalidation and replacement strategies for location-dependent data in mobile environments

Mobile location-dependent information services (LDISs) have become increasingly popular in recent years. However, data caching strategies for LDISs have thus far received little attention. In this paper, we study the issues of cache invalidation and cache replacement for location-dependent data under a geometric location model. We introduce a new performance criterion, called caching efficiency, and propose a generic method for location-dependent cache invalidation strategies. In addition, two cache replacement policies, PA and PAID, are proposed. Unlike the conventional replacement policies, PA and PAID take into consideration the valid scope area of a data value. We conduct a series of simulation experiments to study the performance of the proposed caching schemes. The experimental results show that the proposed location-dependent invalidation scheme is very effective and the PA and PAID policies significantly outperform the conventional replacement policies

1079

A novel robot hand with embedded shape memory alloy actuators

Describes the development of an active robot hand, which allows smooth and lifelike motions for anthropomorphic grasping and fine manipulations. An active robot finger 10 mm in outer diameter with a shape memory alloy (SMA) wire actuator embedded in the finger with a constant distance from the geometric centre of the finger was designed and fabricated. The practical specifications of the SMA wire and the flexible rod were determined on the basis of a series of formulae. The active finger consists of two bending parts, the SMA actuators and a connecting part. The mechanical properties of the bending part are investigated. The control system on the basis of resistance feedback is also presented. Finally, a robot hand with three fingers was designed and the grasping experiment was carried out to demonstrate its performance

806

Flow measurement - future directions

Interest in the flow of liquids and its measurement can be traced back to early studies by the Egyptians, the Chinese and the Romans. Since these early times the science of flow measurement has undergone a massive change but during the last 25 years or so (1977-2002) it has matured enormously. One of the principal reasons for this is that higher accuracies and reliabilities have been demanded by industry in the measurement of fiscal transfers and today there is vigorous interest in the subject from both the flowmeter manufacturer and user viewpoints. This interest is coupled with the development of advanced computer techniques in fluid mechanics together with the application of increasingly sophisticated electronics

843

An ACM-W literature review on women in computing

The pipeline shrinkage problem for women in computer science is a well-known and documented phenomenon where the ratio of women to men involved in computing shrinks dramatically from early student years to working years. During the last decade, considerable research ensued to understand the reasons behind the existence of the shrinking pipeline and in some cases to take action to increase the numbers of women in computing. Through the work of a National Science Foundation funded project, ACM's Committee on Women in Computing (ACM-W) has taken a first step towards pulling this research together. A large number of articles was gathered and processed on the topic of women in computing and the shrinking pipeline. The committee created a publicly available online database to organize the references of this body of work by topic, author, and reference information. The database, constantly being updated, is accessible through ACM-W's website <http://www.acm.org/women>. A final report is also available via the ACM-W Web site which covers current statistics on women in computing, summaries of the literature in the database, and a set of recommendations. The article is a brief synopsis of a subset of the literature review as of August 2001

1084

On quasi-linear PDAEs with convection: applications, indices, numerical solution

For a class of partial differential algebraic equations (PDAEs) of quasi-linear type which include nonlinear terms of convection type, a possibility to determine a time and spatial index is considered. As a typical example we investigate an application from plasma physics. Especially we discuss the numerical solution of initial boundary value problems by means of a corresponding finite difference splitting procedure which is a modification of a well-known fractional step method coupled with a matrix factorization. The convergence of the numerical solution towards the exact solution of the corresponding initial boundary value problem is investigated. Some results of a numerical solution of the plasma PDAE are given

1455

A wizard idea [Internet in finance]

New technology is set to become an ever-more important area of work for brokers. Lawrie Holmes looks at how the Internet is driving change and opportunity

1410

WAM!Net: private pipes for electronic media

"We are the digital version of FedEx. We offer storage and intelligent workflow." The United States military - especially during war time - is pretty careful about the way it handles its workflow and communications. Before a company is awarded a government contract, the company and its technology are screened and verified. If the technology or its creators aren't trustworthy and secure, chances are they aren't getting by Uncle Sam. Record companies and publishing houses tend to feel the same way. After all, security is just as important to a record executive as it is to a Navy commander. WAM!Net, a Wide-Area Media network (hence, the name) passes muster with both. The company, which employs about 320 employees around the world, has 15000 customers including the US Navy and a host of record labels, publishing companies, healthcare providers, and advertising agencies, all of whom use its network as a way to transport, store, and receive data. "We are the digital version of FedEx. We offer storage and intelligent workflow," says Murad Velani, executive vice president of sales and marketing for WAM!Net. "We started out as purely transport and we've become a digital platform."

1378

Development of an Internet-based intelligent design support system for rolling element bearings

This paper presents a novel approach to developing an intelligent agile design system for rolling bearings based on artificial intelligence (AI), Internet and Web technologies and expertise. The underlying philosophy of the approach is to use AI technology and Web-based design support systems as smart tools from which design customers can rapidly and responsively access the systems' built-in design expertise. The approach is described in detail with a novel AI model and system implementation issues. The major issues in implementing the approach are discussed with particular reference to using AI technologies, network programming, client-server technology and open computing of bearing design and manufacturing requirements

768

Critical lines identification on voltage collapse analysis

This paper deals with critical lines identification on voltage collapse analysis. It is known, from the literature, that voltage collapse is a local phenomenon that spreads around an initial neighborhood Therefore, identifying the system critical bus plays an important role on voltage collapse prevention. For this purpose, the system critical transmission lines should also be identified In this paper, these issues are addressed, yielding reliable results in a short computational time. Tests are done with the help of the IEEE-118 bus and the Southeastern Brazilian systems

1199

Quasi stage order conditions for SDIRK methods

The stage order condition is a simplifying assumption that reduces the number of order conditions to be fulfilled when designing a Runge-Kutta (RK) method. Because a DIRK (diagonally implicit RK) method cannot have stage order greater than 1, we introduce quasi stage order conditions and derive some of their properties for DIRKs. We use these conditions to derive a low-order DIRK method with embedded error estimator. Numerical tests with stiff ODEs and DAEs of index 1 and 2 indicate that the method is competitive with other RK methods for low accuracy tolerances

589

Hierarchical neuro-fuzzy quadtree models

Hybrid neuro-fuzzy systems have been in evidence during the past few years, due to its attractive combination of the learning capacity of artificial neural networks with the interpretability of the fuzzy systems. This article proposes a new hybrid neuro-fuzzy model, named hierarchical neuro-fuzzy quadtree (HNFQ), which is based on a recursive partitioning method of the input space named quadtree. The article describes the architecture of this new model, presenting its basic cell and its learning algorithm. The HNFQ system is evaluated in three well known benchmark applications: the sinc(x, y) function approximation, the Mackey Glass chaotic series forecast and the two spirals problem. When compared to other neuro-fuzzy systems, the HNFQ exhibits competing results, with two major advantages it automatically creates its own structure and it is not limited to few input variables

630

Score tests for zero-inflated Poisson models

In many situations count data have a large proportion of zeros and the zero-inflated Poisson regression (ZIP) model may be appropriate. A simple score test for zero-inflation, comparing the ZIP model with a constant proportion of excess zeros to a standard Poisson regression model, was given by van den Broek (1995). We extend this test to the more general situation where the zero probability is allowed to depend on covariates. The performance of this test is evaluated using a simulation study. To identify potentially important covariates in the zero-inflation model a composite test is proposed. The use of the general score test and the composite procedure is illustrated on two examples from the literature. The composite score test is found to suggest appropriate models

675

Application foundations [application servers]

The changing role of application servers means choosing the right platform has become a complex challenge

1220

Modeling discourse in collaborative work support systems: a knowledge representation and configuration perspective

Collaborative work processes usually raise a lot of intricate debates and negotiations among participants, whereas conflicts of interest are inevitable and support for achieving consensus and compromise is required. Individual contributions, brought up by parties with different backgrounds and interests, need to be appropriately structured and maintained. This paper presents a model of discourse acts that participants use to communicate their attitudes to each other, or affect the attitudes of others, in such environments. The first part deals with the knowledge representation and communication aspects of the problem, while the second one, in the context of an already implemented system, namely HERMES, with issues related to the configuration of the contributions asserted at each discourse instance. The overall work focuses on the machinery needed in a computer-assisted collaborative work environment, the aim being to further enhance the human-computer interaction

1265

Optimization of requantization parameter for MPEG transcoding

This paper considers transcoding in which an MPEG stream is converted to a low-bit-rate MPEG stream, and proposes a method in which the transcoding error can be reduced by optimally selecting the quantization parameter for each macroblock. In transcoding with a low compression ratio, it is crucial to prohibit transcoding with a requantization parameter which is 1 to 2 times the quantization parameter of the input stream. Consequently, as the first step, an optimization method for the requantization parameter is proposed which cares for the error propagation effect by interframe prediction. Then, the proposed optimization method is extended so that the method can also be applied to the case of a high compression ratio in which the rate-distortion curve is approximated for each macroblock in the range of requantization parameters larger than 2 times the quantization parameter. It is verified by a simulation experiment that the PSNR is improved by 0.5 to 0.8 dB compared to the case in which a 6 Mbit/s MPEG stream is not optimized by twofold recompression

1298

An analytical model for a composite adaptive rectangular structure using the Heaviside function

The objective of this article is to describe a mathematical model, based on the Heaviside function and on the delta -Dirac distribution, for a composite adaptive rectangular structure with embedded and/or bonded piezoelectric actuators and sensors. In the adopted structure model, the laminae are made up a configuration of rectangular nonpiezoelectric and piezoelectric patches. The laminae do not all have the same area nor do they present the same configuration, such that there are points where there is no material. The equations of motion and the boundary conditions, which describe the electromechanical coupling, are based on the Mindlin displacement field, on the linear theory of piezoelectricity, and on the Hamilton principle

688

Active vibration control of piezolaminated smart beams

This paper deals with the active vibration control of beam like structures with distributed piezoelectric sensor and actuator layers bonded on top and bottom surfaces of the beam. A finite element model based on Euler-Bernoulli beam theory has been developed. The contribution of the piezoelectric sensor and actuator layers on the mass and stiffness of the beam is considered. Three types of classical control strategies, namely direct proportional feedback, constant-gain negative velocity feedback and Lyapunov feedback and an optimal control strategy, linear quadratic regulator (LQR) scheme are applied to study their control effectiveness. Also, the control performance with different types of loading, such as impulse loading, step loading, harmonic and random loading is studied

574

A novel approach for the detection of pathlines in X-ray angiograms: the wavefront propagation algorithm

Presents a new pathline approach, based on the wavefront propagation principle, and developed in order to reduce the variability in the outcomes of the quantitative coronary artery analysis. This novel approach, called wavepath, reduces the influence of the user-defined start- and endpoints of the vessel segment and is therefore more robust and improves the reproducibility of the lesion quantification substantially. The validation study shows that the wavepath method is totally constant in the middle part of the pathline, even when using the method for constructing a bifurcation or sidebranch pathline. Furthermore, the number of corrections needed to guide the wavepath through the correct vessel is decreased from an average of 0.44 corrections per pathline to an average of 0.12 per pathline. Therefore, it can be concluded that the wavepath algorithm improves the overall analysis substantially

1121

Optimal bandwidth utilization of all-optical ring with a converter of degree 4

In many models of all-optical routing, a set of communication paths in a network is given, and a wavelength is to be assigned to each path so that paths sharing an edge receive different wavelengths. The goal is to assign as few wavelengths as possible, in order to use the optical bandwidth efficiently. If a node of a network contains a wavelength converter, any path that passes through this node may change its wavelength. Having converters at some of the nodes can reduce the number of wavelengths required for routing. This paper presents a wavelength converter with degree 4 and gives a routing algorithm which shows that any routing with load L can be realized with L wavelengths when a node of an all-optical ring hosts such a wavelength converter. It is also proved that 4 is the minimum degree of the converter to reach the full utilization of the available wavelengths if only one node of an all-optical ring hosts a converter

1164

Friedberg numberings of families of n-computably enumerable sets

We establish a number of results on numberings, in particular, on Friedberg numberings, of families of d.c.e. sets. First, it is proved that there exists a Friedberg numbering of the family of all d.c.e. sets. We also show that this result, patterned on Friedberg's famous theorem for the family of all c.e. sets, holds for the family of all n-c.e. sets for any n > 2. Second, it is stated that there exists an infinite family of d.c.e. sets without a Friedberg numbering. Third, it is shown that there exists an infinite family of c.e. sets (treated as a family of d.c.e. sets) with a numbering which is unique up to equivalence. Fourth, it is proved that there exists a family of d.c.e. sets with a least numbering (under reducibility) which is Friedberg but is not the only numbering (modulo reducibility)

549

Taking it to the max [ventilation systems]

Raising the volumetric air supply rate is one way of increasing the cooling capacity of displacement ventilation systems. David Butler and Michael Swainson explore how different types of diffusers can help make this work

1159

Sigma -admissible families over linear orders

Admissible sets of the form HYP(M), where M is a recursively saturated system, are treated. We provide descriptions of subsets M, which are Sigma /sub */-sets in HYP(M), and of families of subsets M, which form Sigma -regular families in HYP(M), in terms of the concept of being fundamental couched in the article. Fundamental subsets and families are characterized for models of dense linear orderings

120

Self-organized critical traffic in parallel computer networks

In a recent paper, we analysed the dynamics of traffic flow in a simple, square lattice architecture. It was shown that a phase transition takes place between a free and a congested phase. The transition point was shown to exhibit optimal information transfer and wide fluctuations in time, with scale-free properties. In this paper, we further extend our analysis by considering a generalization of the previous model in which the rate of packet emission is regulated by the local congestion perceived by each node. As a result of the feedback between traffic congestion and packet release, the system is poised at criticality. Many well-known statistical features displayed by Internet traffic are recovered from our model in a natural way

963

A computational model of learned avoidance behavior in a one-way avoidance experiment

We present a computational model of learned avoidance behavior in a one-way avoidance experiment. Our model employs the reinforcement learning paradigm and a temporal-difference algorithm to implement both classically conditioned and instrumentally conditioned components. The role of the classically conditioned component is to develop an expectation of future benefit that is a function of the learning system's state and action. Competition among the instrumentally conditioned components determines the overt behavior generated by the learning system. Our model displays, in simulation, the reduced latency of the avoidance behavior during learning with continuing trials and the resistance to extinction of the avoidance response. These results are consistent with experimentally observed animal behavior. Our model extends the traditional two-process learning mechanism of Mowrer (1947) by explicitly defining the mechanisms of proprioceptive feedback, an internal clock, and generalization over the action space

926

Experimental investigation of active vibration control using neural networks and piezoelectric actuators

The use of neural networks for identification and control of smart structures is investigated experimentally. Piezoelectric actuators are employed to suppress the vibrations of a cantilevered plate subject to impulse, sine wave and band-limited white noise disturbances. The neural networks used are multilayer perceptrons trained with error backpropagation. Validation studies show that the identifier predicts the system dynamics accurately. The controller is trained adaptively with the help of the neural identifier. Experimental results demonstrate excellent closed-loop performance and robustness of the neurocontroller

648

Study of ambiguities inherent to the spectral analysis of Voigt profiles-a modified Simplex approach

In pulsed spectrometries, temporal transients are often analyzed directly in the temporal domain, assuming they consist only of purely exponentially decaying sinusoids. When experimental spectra actually consist of Gaussian or Voigt profiles (Gauss-Lorentz profiles), we show that the direct methods may erroneously interpret such lines as the sum of two or more Lorentzian profiles. Using a Nelder and Mead Simplex method, modified by introducing new means to avoid degeneracies and quenchings in secondary minima, we demonstrate that a large number of different solutions can be obtained with equivalent accuracy over the limited acquisition time interval, with final peak parameters devoid of physical or chemical meaning

72

A three-tier technology training strategy in a dynamic business environment

As end-user training becomes increasingly important in today's technology-intensive business environment, progressive companies remain alert to find ways to provide their end users with timely training and resources. This paper describes an innovative training strategy adopted by one midsize organization to provide its end users with adequate, flexible, and responsive training. The paper then compares the three-tier strategy with other models described in technology training literature. Managers who supervise technology end users in organizations comparable to the one in the study may find the three-tier strategy workable and may want to use it in their own training programs to facilitate training and improve end-user skills. Researchers and scholars may find that the idea of three-tier training generates new opportunities for research

1258

Implementation and performance evaluation of a FIFO queue class library for time warp

The authors describe the implementation, use, and performance evaluation of a FIFO queue class library by means of a high-performance, easy-to-use interface employed for queuing simulations in parallel discrete simulations based on the time warp method. Various general-purpose simulation libraries and languages have been proposed, and among these some have the advantage of not requiring users to define anything other than the state vector, and not needing awareness of rollback under a platform which performs state control based on copies. However, because the state vectors must be defined as simple data structures without pointers, dynamic data structures such as a FIFO queue cannot be handled directly. Under the proposed class library, both the platform and the user can handle such structures in the same fashion that embedded data structures are handled. In addition, instead of all stored data, just the operational history can be stored and recovered efficiently at an effectively minimal cost by taking advantage of the first-in-first-out characteristics of the above data structures. When the kernel deletes past state histories during a simulation, garbage collection is also performed transparently using the corresponding method

1345

Infrared-image classification using hidden Markov trees

An image of a three-dimensional target is generally characterized by the visible target subcomponents, with these dictated by the target-sensor orientation (target pose). An image often changes quickly with variable pose. We define a class as a set of contiguous target-sensor orientations over which the associated target image is relatively stationary with aspect. Each target is in general characterized by multiple classes. A distinct set of Wiener filters are employed for each class of images, to identify the presence of target subcomponents. A Karhunen-Loeve representation is used to minimize the number of filters (templates) associated with a given subcomponent. The statistical relationships between the different target subcomponents are modeled via a hidden Markov tree (HMT). The HMT classifier is discussed and example results are presented for forward-looking-infrared (FLIR) imagery of several vehicles

1300

Will CPXe save the photofinishing market?

A consortium of film suppliers and electronics firms has proposed the Common Picture Exchange environment. It will let diverse providers cooperate via the Internet to sell digital-photo prints

755

Hardware and software platform for real-time processing and visualization of echographic radiofrequency signals

In this paper the architecture of a hardware and software platform, for ultrasonic investigation is presented. The platform, used in conjunction with an analog front-end hardware for driving the ultrasonic transducers of any commercial echograph, having the radiofrequency echo signal access, make it possible to dispose of a powerful echographic system for experimenting any processing technique, also in a clinical environment in which real-time operation mode is an essential prerequisite. The platform transforms any echograph into a test-system for evaluating the diagnostic effectiveness of new investigation techniques. A particular user interface was designed in order to allow a real-time and simultaneous visualization of the results produced in the different stages of the chosen processing procedure. This is aimed at obtaining a better optimization of the processing algorithm. The most important platform aspect, which also constitutes the basic differentiation with respect to similar systems, is the direct processing of the radiofrequency echo signal, which is essential for a complete analysis of the particular ultrasound-media interaction phenomenon. The platform completely integrates the architecture of a personal computer (PC) giving rise to several benefits, such as the quick technological evolution in the PC field and an extreme degree of programmability for different applications. The PC also constitutes the user interface, as a flexible and intuitive visualization support, and performs some software signal processing, by custom algorithms and commercial libraries. The realized close synergy between hardware and software allows the acquisition and real-time processing of the echographic radiofrequency (RF) signal with fast data representation

710

Optimal allocation of runs in a simulation metamodel with several independent variables

Cheng and Kleijnen (1999) propose a very general regression metamodel for modelling the output of a queuing system. Its main limitations are that the regression function is based on a polynomial and that it can use only one independent variable. These limitations are removed here. We derive an explicit formula for the optimal way of assigning simulation runs to the different design points

1044

Analogue realizations of fractional-order controllers

An approach to the design of analogue circuits, implementing fractional-order controllers, is presented. The suggested approach is based on the use of continued fraction expansions; in the case of negative coefficients in a continued fraction expansion, the use of negative impedance converters is proposed. Several possible methods for obtaining suitable rational approximations and continued fraction expansions are discussed. An example of realization of a fractional-order I/sup lambda / controller is presented and illustrated by obtained measurements. The suggested approach can be used for the control of very fast processes, where the use of digital controllers is difficult or impossible

1001

A conflict between language and atomistic information

Fred Dretske and Jerry Fodor are responsible for popularizing three well-known theses in contemporary philosophy of mind: the thesis of Information-Based Semantics (IBS), the thesis of Content Atomism (Atomism) and the thesis of the Language of Thought (LOT). LOT concerns the semantically relevant structure of representations involved in cognitive states such as beliefs and desires. It maintains that all such representations must have syntactic structures mirroring the structure of their contents. IBS is a thesis about the nature of the relations that connect cognitive representations and their parts to their contents (semantic relations). It holds that these relations supervene solely on relations of the kind that support information content, perhaps with some help from logical principles of combination. Atomism is a thesis about the nature of the content of simple symbols. It holds that each substantive simple symbol possesses its content independently of all other symbols in the representational system. I argue that Dretske's and Fodor's theories are false and that their falsehood results from a conflict IBS and Atomism, on the one hand, and LOT, on the other

883

On conflict-free executions of elementary nets

Deals with analysis of elementary Petri nets with respect to possibilities of avoiding conflicts during their executions. There are two main aims of the paper. The first is to find a method of checking if a net is conflict-avoidable (i.e., if it possesses a conflict-free fair run). The second is to find a method of rebuilding any net to a totally conflict-avoidable net (i.e., a net possessing a conflict-free fair run in every one process) with the same behaviour. The main results are the following: 1. The proof of decidability, for elementary nets, of the problem of existence of a conflict-avoidable fair process (and an algorithm producing all fair runs). 2. Construction, for an arbitrary given elementary net, of a totally conflict-avoidable net with the same behaviour. The net, completed this way, has the same behaviour as the original one. Moreover, it is totally conflict-avoidable, and its execution may be supervised (in order to ensure conflict-freeness) by the reduced case graph built by the algorithm of the former section

13

Stability analysis of the characteristic polynomials whose coefficients are polynomials of interval parameters using monotonicity

We analyze the stability of the characteristic polynomials whose coefficients are polynomials of interval parameters via monotonicity methods. Our stability conditions are based on Frazer-Duncan's theorem and all conditions can be checked using only endpoint values of interval parameters. These stability conditions are necessary and sufficient under the monotonicity assumptions. When the monotonicity conditions do not hold on the whole parameter region, we present an interval division method and a transformation algorithm in order to apply the monotonicity conditions. Then, our stability analysis methods can be applied to all characteristic polynomials whose coefficients are polynomials of interval parameters

56

New thinking on rendering

Looks at how graphics hardware solves a range of rendering problems

629

Calibrated initials for an EM applied to recursive models of categorical variables

The estimates from an EM, when it is applied to a large causal model of 10 or more categorical variables, are often subject to the initial values for the estimates. This phenomenon becomes more serious as the model structure becomes more complicated involving more variables. As a measure of compensation for this, it has been recommended in literature that EMs are implemented several times with different sets of initial values to obtain more appropriate estimates. We propose an improved approach for initial values. The main idea is that we use initials that are calibrated to data. A simulation result strongly indicates that the calibrated initials give rise to the estimates that are far closer to the true values than the initials that are not calibrated

1239

Three-dimensional global MHD simulation code for the Earth's magnetosphere using HPF/JA

We have translated a three-dimensional magnetohydrodynamic (MHD) simulation code of the Earth's magnetosphere from VPP Fortran to HPF/JA on the Fujitsu VPP5000/56 vector-parallel supercomputer and the MHD code was fully vectorized and fully parallelized in VPP Fortran. The entire performance and capability of the HPF MHD code could be shown to be almost comparable to that of VPP Fortran. A three-dimensional global MHD simulation of the Earth's magnetosphere was performed at a speed of over 400 Gflops with an efficiency of 76.5% using 56 processing elements of the Fujitsu VPP5000/56 in vector and parallel computation that permitted comparison with catalog values. We have concluded that fluid and MHD codes that are fully vectorized and fully parallelized in VPP Fortran can be translated with relative ease to HPF/JA, and a code in HPF/JA may be expected to perform comparably to the same code written in VPP Fortran

1180

Decomposition of additive cellular automata

Finite additive cellular automata with fixed and periodic boundary conditions are considered as endomorphisms over pattern spaces. A characterization of the nilpotent and regular parts of these endomorphisms is given in terms of their minimal polynomials. Generalized eigenspace decomposition is determined and relevant cyclic subspaces are described in terms of symmetries. As an application, the lengths and frequencies of limit cycles in the transition diagram of the automaton are calculated

947

The fully entangled fraction as an inclusive measure of entanglement applications

Characterizing entanglement in all but the simplest case of a two qubit pure state is a hard problem, even understanding the relevant experimental quantities that are related to entanglement is difficult. It may not be necessary, however, to quantify the entanglement of a state in order to quantify the quantum information processing significance of a state. It is known that the fully entangled fraction has a direct relationship to the fidelity of teleportation maximized under the actions of local unitary operations. In the case of two qubits we point out that the fully entangled fraction can also be related to the fidelities, maximized under the actions of local unitary operations, of other important quantum information tasks such as dense coding, entanglement swapping and quantum cryptography in such a way as to provide an inclusive measure of these entanglement applications. For two qubit systems the fully entangled fraction has a simple known closed-form expression and we establish lower and upper bounds of this quantity with the concurrence. This approach is readily extendable to more complicated systems

141

A high-resolution high-frequency monolithic top-shooting microinjector free of satellite drops - part I: concept, design, and model

Introduces an innovative microinjector design, featuring a bubble valve, which entails superior droplet ejection characteristics and monolithic fabrication, which allows handling of a wide range of liquids. This new microinjector uses asymmetric bubbles to reduce crosstalk, increase frequency response and eliminate satellite droplets. During a firing, i.e., droplet ejection, the "virtual valve" closes, by growing a thermal bubble in the microchannel, to isolate the microchamber from the liquid supply and neighboring chambers. Between firings, however, the virtual valve opens, by collapsing the bubble, to reduce flow restriction for fast refilling of the microchamber. The use of bubble valves brings about fast and reliable device operation without imposing the significant complication fabrication of physical microvalves would call for. In addition, through a special heater configuration and chamber designs, bubbles surrounding the nozzle cut off the tail of the droplets being ejected and completely eliminate satellite droplets. A simple one-dimensional model of the operation of the microinjector is used to estimate the bubble formation and liquid refilling

902

TCP explicit congestion notification over ATM-UBR: a simulation study

The enhancement of transmission control protocol's (TCP's) congestion control mechanisms using explicit congestion notification (ECN) over asynchronous transfer mode (ATM) networks is overviewed. TCP's congestion control is enhanced so that congestion is indicated by not only packet losses as is currently the case but an agent implemented at the ATM network's edge as well. The novel idea uses EFCI (explicit forward congestion indication) bits (available in every ATM cell header) to generalize the ECN response to the UBR (unspecified bit rate) service, notify congestion, and adjust the credit-based window size of the TCR. The authors' simulation experiments show that TCP ECN achieves significantly lower cell loss, packet retransmissions, and buffer utilization, and exhibits better throughput than (non-ECN) TCP Reno