bluuebunny/crossref_metadata_2025 huggingface dataset:
An incidence density sampling program for nested case-control analyses
Authors: Richardson D B
Published: November 2004

Background:The nested case-control design can be a very efficient approach to an epidemiological investigation. In order to obtain unbiased estimates of relative risk, controls should be selected by incidence density sampling, which involves matching each case to a sample of those who are at risk at the time of case occurrence.

Methods:This paper presents a simple computer program for incidence density sampling. This program was evaluated using data derived from a cohort study of mortality among workers employed in the nuclear weapons industry. Controls were selected for cases via incidence density sampling; an estimate of the exposure-mortality association was obtained via conditional logistic regression. After 100 iterations of this procedure, the average effect estimate was compared to the risk estimate obtained via proportional hazards regression. The same methods were used to evaluate a program for incidence density sampling that was proposed previously by Pearce in 1989.5

Results:Relative risk estimates obtained from nested case-control analyses conducted using the incidence density sampling program reported in this paper are unbiased. In contrast, the program for incidence density sampling proposed by Pearce5tended to produce biased relative risk estimates; the magnitude of bias increased with increasing numbers of controls selected per case.

Conclusions:The computer program described in this paper offers a simple approach to incidence density sampling for nested case-control analyses with exact matching on attained age and appropriate enumeration of the pool of eligible controls for each case. This method overcomes problems of bias inherent in a previously proposed program for incidence density sampling.
Superimposed Quesnel (late PaleozoicJurassic) and YukonTanana (DevonianMississippian) arc assemblages, Cassiar Mountains, northern British Columbia: field, UPb, and igneous petrochemical evidence
Authors: Nelson JoAnne , Friedman Richard
Published: November 2004

Allochthons in the Cassiar Mountains of northern British Columbia contain assemblages belonging to two distinct Canadian Cordilleran terranes, YukonTanana (YTT) and Quesnellia. These assemblages, of pre-Late Devonian, DevonianMississippian, PennsylvanianPermian, and Early Jurassic age, occur in intrusive and depositional, as well as structural, contact with each other. The allochthons are gently dipping thrust panels, interrupted by the mid-Cretaceous Cassiar Batholith. A key element for correlation across the batholith is the Mississippian and older pericratonic Dorsey Complex. New DevonianMississippian UPb ages for deformed plutons within it document an igneous suite like those in type YukonTanana exposures farther north. Other characteristics of the Dorsey Complex that ally it with YTT are orthoquartzites and grits, and amphibolite bodies with transitional mid-ocean ridge basalt (MORB) to ocean-island basalt (OIB) petrochemical signatures. Unconformities, deformed clasts in the late Paleozoic sequences, and a shared mid-Permian intrusive suite show that later arcs onlapped the mid-Paleozoic and older YTT assemblage. The Early Jurassic intrusive suite cuts all major contacts and fabrics except the terrane-bounding fault between the Slide Mountain and combined YTTQuesnel terranes. It represents a northern continuation of a plutonic belt that extends the length of the Mesozoic Quesnel magmatic arc. These relationships carry important implications for Cordilleran terrane history and the tectonic evolution of the North American margin. At least some of the major terranes were not unrelated entities prior to their accretion to the continent, but a system of superimposed and interconnected arcs that developed over a protracted time interval, with complex and evolving paleogeographic configurations much like the modern western Pacific province.
Holocene tree line, permafrost, and climate dynamics in the Nenets Region, East European Arctic
Authors: Kultti Seija , Oksanen Pirita , Väliranta Minna
Published: November 2004

Pollen, stomata, and macrofossils in a lake core with a basal date of 9700 14C BP were used to reconstruct past changes in climate and vegetation in the arctic tree line area, northeast European Russia. A palsa peat profile was investigated to establish a chronology of mire initiation and permafrost development during the Holocene. Macrofossils show that tree birch was present in the study area at the beginning of the Holocene and stands of spruce became established shortly thereafter. However, pollen evidence suggests that almost 400 years passed before the area was occupied by a mixed sprucebirch forest, which lasted until ca. 5000 BP. Subsequently, the area reverted to foresttundra. Paludification began ca. 9000 BP continuing at least until 5700 BP. The conditions were permafrost-free at least until 4500 BP. The latest permafrost aggradation phase is dated to the Little Ice Age. We interpret summer temperatures to have been ca. 34 °C higher between ca. 8900 and 5500 BP than at present, and the lowest temperature regime of the Holocene to have occurred between 2700 and 2100 BP.
Growth and morphological evolution of hexapod-shaped cuprous oxide microcrystals at room temperature
Authors: Zhang Xu , Xie Yi , Xu Fen , Xu Di , Liu Huarong
Published: November 2004

Growth and morphological evolution of hexapod-shaped Cu2O microcrystals is carefully studied via a γ-irradiation reduction route at room temperature and under ambient pressure. The products are examined by means of XRD patterns and FE-SEM images. The as-obtained hexapod-shaped Cu2O microcrystal is composed of six legs, whose adjacent legs are perpendicular to each other and each leg is composed of two perpendicular cross blades. A simple reaction system, excluding the influence of surfactant and thermal disturbance, would favor revelation of the inherent growth habit of Cu2O microcrystals under relatively mild experimental conditions. Furthermore, the effects of several factors on the final product and morphology are investigated.Key words: hexapod-shaped, γ-irradiation, cuprous oxide, morphological evolution.
SOME COMPLEXITY RESULTS FOR RINGS OF PETRI NETS
Authors: YEN HSU-CHUN , WANG BOW-YAW , YANG MING-SHANG
Published: November 2004

We define a subclass of Petri nets called m–state n–cycle Petri nets, each of which can be thought of as a ring of n bounded (by m states) Petri nets using n potentially unbounded places as joins. Let Ring(n, l, m) be the class of m–state n–cycle Petri nets in which the largest integer mentioned can be represented in l bits (when the standard binary encoding scheme is used). As it turns out, both the reachability problem and the boundedness problem can be decided in O(n(l+log m)) nondeterministic space. Our results provide a slight improvement over previous results for the so-called cyclic communicating finite state machines. We also compare and contrast our results with that of VASS(n, l, s), which represents the class of n-dimensional s-state vector addition systems with states where the largest integer mentioned can be described in l bits.
VERTICAL BEAM PIXE FOR IN SITU ANALYSIS OF LIQUIDS
Authors: KAWAI JUN , MAEDA KUNIKO
Published: November 2004

We have constructed a vertical beam line for in situ liquid analysis. Details of this beam line, the analytical results of milk and tea, and the detection limits of this beam line for 8-MeV He+ ion beam are described.
MONOLITHIC INTEGRATION OF DFB LASERS AND ELECTROABSORPTION MODULATORS USING IN-PLANE QUANTUM ENERGY CONTROL OF MQW STRUCTURES
Authors: AOKI MASAHIRO , SUZUKI MAKOTO , SANO HIROHISA , SASAKI SHINYA , KAWANO TOSHIHIRO , KODERA HIROSHI
Published: November 2004

This paper describes the fabrication and characteristics of a new multiple-quantum-well (MQW) integrated distributed feedback (DFB) laser diode-electroabsorption (EA) optical modulator for use as the transmitter light source in multigigabit, long-distance optical fiber communications. The device employed a novel integration scheme for active/passive waveguide coupling achieved by controlling the quantum energy of selectively grown MQW structures. This new fabrication technique for photonic integrated circuits (PICs) facilitates smooth, high-quality waveguide coupling between the interconnected guided-wave elements. It is based on the growth rate enhancement or compositional changes in the material of the quantum-well layer grown by selective-area metalorganic vapor phase epitaxy (MOVPE). Good local quantum energy control within a very wide range is shown for simultaneously grown MQW crystals. Moreover, the crystal quality, well/barrier heterointerface, and flatness and uniformity of these selectively grown MQW crystals are found to be as good as those of normally grown crystals.

This technique is applied to an MQW integrated DFB laser diode-EA modulator. Superior device performance, including a low threshold and highly efficient lasing properties, as well as high-speed, low-drive-voltage, and low-chirp modulator characteristics are attained due to improved optical coupling, easy fabrication, and sufficient crystal quality of selectively grown MQW structures. 10 Gbit/s data transmission is demonstrated over a 500 km dispersion-shifted single-mode fiber. This combined with long-term device reliability, makes this integration technique more attractive for practical fabrication of semiconductor PICs.
THERMAL EFFECTS IN VERTICAL-CAVITY SURFACE-EMITTING LASERS
Authors: OSIŃSKI MAREK , NAKWASKI WŁODZIMIERZ
Published: November 2004

A comprehensive review of temperature-related effects and thermal modeling of vertical-cavity surface-emitting lasers (VCSELs) is presented. The paper is divided into two major parts. First, the effects of temperature on device characteristics are discussed, including the temperature dependence of the longitudinal mode spectra, the threshold current, the transverse-mode structure, and the output power. A new condition is formulated for thermal matching of the Bragg mirrors and the spacer region and a comparison is made between characteristic temperatures for the threshold current (T0) and for the external quantum efficiency (Tη). In the second part, various approaches to thermal modeling of VCSELs are described. Both simplified and comprehensive thermal models are considered and both analytical and numerical approaches are discussed. A new analytical approximate method for analysis of heat-flux spreading in multilayer structures is described. The most important results obtained with the aid of these models are presented. In particular, we show that the current dependence of thermal resistance is very sensitive to VCSEL structure, and is strongly influenced by the relative distribution of heat sources and their location with respect to the heat sink.
A UNIFYING LOOK AT SEMIGROUP COMPUTATIONS ON MESHES WITH MULTIPLE BROADCASTING
Authors: BHAGAVATHI D. , OLARIU S. , SHEN W. , WILSON L.
Published: November 2004

Given a sequence of m items α1, α2,…, αm from a semigroup S with an associative operation ⊕, the semigroup computation problem involves computing α1 ⊕ α2 ⊕…⊕ αm. We consider the semigroup computation problem involving m (2≤m≤n) items on a mesh with multiple broadcasting of size [Formula: see text]. Our contribution is to present the first lower bound and the first time-optimal algorithm which apply to the entire range of m (2≤m≤n). Specifically, we show that any algorithm that solves the semigroup computation problem must take Ω( log m) time if [Formula: see text] and [Formula: see text] time for [Formula: see text]. We then show that our bound is tight by designing an algorithm whose running time matches the lower bound. These results unify and generalize all semigroup lower bounds and algorithms known to the authors.
R2M: A RECONFIGURABLE REWRITE MACHINE
Authors: RAMESH R.
Published: November 2004

Term rewriting is a popular computational paradigm for symbolic computations such as formula manipulation, theorem proving and implementations of nonprocedural programming languages. In rewriting, the most demanding operation is repeated simplification of terms by pattern matching them against rewrite rules. We describe a parallel architecture, R2M, for accelerating this operation. R2M can operate either as a stand-alone processor using its own memory or as a backend device attached to a host using the host’s main memory. R2M uses only a fixed number (independent of input size) of processing units and fixed capacity auxiliary memory units, yet it is capable of handling variable-size rewrite rules that change during simplification. This is made possible by a simple and reconfigurable interconnection present in R2M. Finally, R2M uses a hybrid scheme that combines the ease, and efficiency of parallel pattern matching using the tree representation of terms, and the naturalness of their dag representation for replacements.
ON LARGE VERTEX SYMMETRIC 2-REACHABLE DIGRAPHS
Authors: COMELLAS F. , FIOL M.A. , GÓMEZ J.
Published: November 2004

We are interested in the construction of the largest possible vertex symmetric digraphs with the property that between any two vertices there is a walk of length two (that is, they are 2-reachable). Other than a theoretical interest, these digraphs and their generalizations may be used as models of interconnection networks for implementing parallelism. In these systems many nodes are connected with relatively few links and short paths between them and each node may execute, without modifications, the same communication software. On the other hand, a message sent from any vertex reaches all vertices, including the sender, in exactly two steps.

In this work we present families of vertex symmetric 2-reachable digraphs with order attaining the upper theoretical bound for any odd degree. Some constructions for even degree are also given.
HADRON FORM FACTORS IN QCD
Authors: BELYAEV V.M. , KOGAN IAN I.
Published: November 2004

We consider the QCD sum rules approach for hadron form factors in infrared region 0≤Q2<1 GeV2. The QCD sum rules in external variable field are formulated. As an example this method is used to calculate proton and nucleon magnetic form factors. The detailed calculation of the nucleon polarization operator in external variable electromagnetic field is done. The obtained form factors (proton and neutron) are in a good agreement with experimental ones.
ASPECTS OF N=2 SUPER-Wn STRINGS
Authors: LU H. , POPE C.N. , WANG X.J. , XU K.W.
Published: November 2004

We construct N=2 super-Wn+1 strings and obtain the complete physical spectrum, for arbitrary n≥2. We also derive more general realizations of the super-Wn+1 algebras in terms of k commuting N=2 super energy-momentum tensors and n−k pairs of complex superfields, with 0≤k≤[(n+1)/2].
EDGE CURRENTS AND VERTEX OPERATORS FOR CHERN-SIMONS GRAVITY
Authors: BIMONTE G. , GUPTA K.S. , STERN A.
Published: November 2004

We apply elementary canonical methods for the quantization of 2+1 dimensional gravity, where the dynamics is given by E. Witten’s ISO(2, 1) Chern-Simons action. As in a previous work, our approach does not involve choice of gauge or clever manipulations of functional integrals. Instead, we just require the Gauss law constraint for gravity to be first class and also to be everywhere differentiable. When the spatial slice is a disc, the gravitational fields can either be unconstrained or constrained at the boundary of the disc. The unconstrained fields correspond to edge currents which carry a representation of the ISO(2, 1) Kac-Moody algebra. Unitary representations for such an algebra have been found using the method of induced representations. In the case of constrained fields, we can classify all possible boundary conditions. For several different boundary conditions, the field content of the theory reduces precisely to that of 1+1 dimensional gravity theories. We extend the above formalism to include sources. The sources take into account self-interactions. This is done by punching holes in the disc, and erecting an ISO(2, 1) Kac–Moody algebra on the boundary of each hole. If the hole is originally sourceless, a source can be created via the action of a vertex operator V. We give an explicit expression for V. We shall show that when acting on the vacuum state, it creates particles with a discrete mass spectrum. The lowest mass particle induces a cylindrical space-time geometry, while higher mass particles give an n fold covering of the cylinder. The vertex operator therefore creates cylindrical space-time geometries from the vacuum.
STRUCTURE OF THE SPACE OF STATES IN RSOS MODELS
Authors: JIMBO MICHIO , MIWA TETSUJI , OHTA YASUHIRO
Published: November 2004

The restricted solid-on-solid models in the antiferromagnetic regime are studied in the framework of quantum affine algebras. Following the line developed recently for vertex models, a representation-theoretical picture is presented for the structure of the space of states. The local operators and the creation/annihilation operators of quasiparticles are defined using vertex operators, and their commutation relations are calculated.
TEMPERATURE RENORMALIZATION GROUP AND RESUMMATION
Authors: ELMFORS PER
Published: November 2004

The temperature renormalization group equation (TRGE) is compared with a diagrammatic expansion for the (ϕ4)4-theory. It is found that the one-loop TRGE resums the leading powers of temperature for the effective mass. A two-loop contribution to TRGE is required to do the leading resummation for the coupling constant. It is also shown that the higher order TRGE resums subleading powers of temperature.
ON POSSIBLE GENERALIZATIONS OF FIELD-ANTIFIELD FORMALISM
Authors: BATALIN I. A. , TYUTIN I. V.
Published: November 2004

A generalized version is proposed for the field–antifield formalism. The antibracket operation is defined in arbitrary field–antifield coordinates. The antisymmetric definitions are given for first- and second-class constraints. In the case of second-class constraints the Dirac's antibracket operation is defined. The quantum master equation as well as the hypergauge fixing procedure are formulated in a coordinate–invariant way. The general hypergauge functions are shown to be antisymmetric first–class constraints whose Jacobian matrix determinant is constant on the constraint surface. The BRST-type generalized transformations are defined and the functional integral is shown to be independent of the hypergauge variations admitted. In the case of reduced phase space the Dirac's antibrackets are used instead of the ordinary ones.
$\mathcal W$-GRAVITY ANOMALIES WITH GHOST LOOPS AND BACKGROUND CHARGES
Authors: HULL C. M.
Published: November 2004

The path-integral quantization of chiral [Formula: see text] gravity is considered and the complete set of anomalies arising from both matter and ghost integrations is calculated. The effects of background charge are included and the results are related to the operator quantization. For those matter theories with exact quantum [Formula: see text] symmetry, the ghost contributions precisely cancel the matter-dependent anomalies. The results are extended to nonchiral [Formula: see text] gravity.
AFFINE TODA SOLITONS AND AUTOMORPHISMS OF DYNKIN DIAGRAMS
Authors: MACKAY NIALL J. , MCGHEE WILLIAM A.
Published: November 2004

Using Hirota's method, solitons are constructed for affine Toda field theories based on the simply laced affine algebras. By considering automorphisms of the simply laced Dynkin diagrams, solutions to the remaining algebras, twisted as well as untwisted, are deduced.
CRITICAL WILSON LINES IN TOROIDAL COMPACTIFICATIONS OF HETEROTIC STRINGS
Authors: MOHAUPT THOMAS
Published: November 2004

Critical values of Wilson lines and general background fields for toroidal compactifications of heterotic string theories are constructed systematically using Dynkin diagrams.
CONFINEMENT AND BOUND STATES SPECTRUM OF MASSLESS FERMIONS IN TWO-DIMENSIONAL SCALAR ELECTRODYNAMICS
Authors: TOKAREV V.F.
Published: November 2004

We investigate through the dilute instanton gas approximation the long-distance properties of the (1+1)-dimensional electrodynamics with massless fermions and Higgs-like bosons. Generally fermions have a charge different from that of bosons and are confined. We find the “mesonic” and “baryonic” spectrum of the model. The fermions become free when their charge becomes equal to that of bosons. This first-order phase transition is investigated as well. The order parameter is found to be the fermion-antifermion condensate, which is zero in confining phase and nonzero in nonconfining phase. The effective long-distance Lagrangians in both phases are found.
SINE-GORDON VS. MASSIVE THIRRING
Authors: KLASSEN TIMOTHY R. , MELZER EZER
Published: November 2004

By viewing the sine-Gordon and massive Thirring models as perturbed conformal field theories, one sees that they are different (the difference being observable, for instance, in finite-volume energy levels). The UV limit of the former (SGM) is a Gaussian model, that of the latter (MTM) a so-called fermionic Gaussian model, the compactification radius of the boson underlying both theories depending on the SG/MT coupling. (These two families of conformal field theories are related by a “twist”.) Corresponding SG and MT models contain a subset of fields with identical correlation functions, but each model also has fields the other one does not have; for example, the fermion fields of MTM are not contained in SGM, and the bosonic soliton fields of SGM are not in MTM. Our results imply, in particular, that the SGM at the so-called “free-Dirac point” β2=4π is actually a theory of two interacting bosons with diagonal S-matrix S=−1, and that for arbitrary couplings the overall sign of the accepted SG S-matrix in the soliton sector should be reversed. More generally, we draw attention to the existence of new classes of quantum field theories, analogs of the (perturbed) fermionic Gaussians models, whose partition functions are invariant only under a subgroup of the modular group. One such class comprises “fermionic versions” of the Virasoro minimal models.
THE SHANMUGADHASAN CANONICAL TRANSFORMATION, FUNCTION GROUPS AND THE EXTENDED SECOND NOETHER THEOREM
Authors: LUSANNA LUCA
Published: November 2004

After the definition of a class of well-behaved singular Lagrangians, an analysis of all the consequences of the extended second Noether theorem in the second-order formalism is made. The phase-space reformulation contains arbitrary first- and second-class constraints. An answer to the problem of the Dirac conjecture is given for this class of singular Lagrangians. By using the concepts of function groups and of the associated Shanmugadhasan canonical transformations, an attempt is made to arrive at a global formulation of the theorem, in which the original invariance under an “infinite continuous group” of transformations is replaced by weak quasi-invariance under an “infinite continuous group [Formula: see text],” whose algebra is an involutive distribution of Lie-Bäcklund vector fields generating the Noether transformations. Its phase-space counterpart is the involutive distribution associated with a special function group Ḡpm, which contains a function subgroup Ḡp connected (when in canonical form) to the Shanmugadhasan canonical transformations. Also, the various possible first-order formalisms are analyzed.
SUPERSYMMETRIC QUANTUM COSMOLOGY
Authors: MACÍAS A. , OBREGÓN O. , SOCORRO J.
Published: November 2004

Supersymmetric minisuperspace quantization is studied for cosmological models without interaction (Bianchi type I) and for models with interaction like Bianchi type IX, the Taub and the FRW (k=+1) model. In particular for the last two cases the profound differences with standard quantum cosmology are emphasized.
QUANTUM-STATISTICAL SPACE-TIME APPROACH TO BOSE-EINSTEIN CORRELATIONS AND MULTIPLICITY DISTRIBUTIONS
Authors: ANDREEV I.V. , PLÜMER M. , WEINER R.M.
Published: November 2004

A systematic quantum-statistical (density matrix) study of Bose-Einstein correlations (BEC’s) is performed. The minimum number of independent parameters that enter into BEC’s is determined. Expressions for the higher order correlation functions are derived, and the relation between BEC’s and multiplicity distributions is clarified. New results concerning the interplay between the chaotic and the coherent component are presented. The investigation of the isospin dependence of BEC’s leads to the prediction of quantum-statistical π+π− correlations and, related with it, the appearance of squeezed states in particle physics. Soft pions are found to play a specially important part in BEC’s, both with respect to the experimental detection of the new correlation and in the clarification of the role of coherence. A significant increase of the available statistics in BEC’s is necessary in order to test experimentally the new theoretical predictions. Two model sources are investigated: a “static” source and an expanding one. A comparison with a model proposed by Gyulassy, Kauffmann and Wilson is performed.
SUPERFLUID FIELD THEORY
Authors: DAVIS R.L.
Published: November 2004

The very low temperature dynamics of an isotropic superfluid is derived from a repulsive bosonic field theory. The field theory is a fully dynamical generalization of the Ginzburg-Landau theory, which at zero temperature has semiclassical superfluid solutions. It is shown that supercurrent quenching occurs above some intrinsic critical velocity. The speed of first sound is calculated and the Landau criterion for a maximum superfluid velocity is derived. At finite temperature, the thermodynamic potential is computed, the order parameter and gap equations are derived, the origin of the Landau two-fluid model is identified and the thermomechanical effect is explained. This theory successfully describes many of the features of 4He well below the critical temperature, as well as relativistic generalizations.
GAL: NETWORKS THAT GROW WHEN THEY LEARN AND SHRINK WHEN THEY FORGET
Authors: ALPAYDIN ETHEM
Published: November 2004

Learning when limited to modification of some parameters has a limited scope; capability to modify the system structure is also needed to get a wider range of the learnable. In the case of artificial neural networks, learning by iterative adjustment of synaptic weights can only succeed if the network designer predefines an appropriate network structure, i.e. the number of hidden layers, units, and the size and shape of their receptive and projective fields. This paper advocates the view that the network structure should not, as is usually done, be determined by trial-and-error but should be computed by the learning algorithm. Incremental learning algorithms can modify the network structure by addition and/or removal of units and/or links. A survey of current connectionist literature is given on this line of thought. “Grow and Learn” (GAL) is a new algorithm that learns an association at one shot due to its being incremental and using a local representation. During the so-called “sleep” phase, units that were previously stored but which are no longer necessary due to recent modifications are removed to minimize network complexity. The incrementally constructed network can later be finetuned off-line to improve performance. Another method proposed that greatly increases recognition accuracy is to train a number of networks and vote over their responses. The algorithm and its variants were tested on recognition of handwritten numerals and seem promising especially in terms of learning speed. This makes the algorithm attractive for on-line learning tasks, e.g. in robotics. The biological plausibility of incremental learning is also discussed briefly.
EFFICIENT IMAGE RETRIEVAL ALGORITHMS FOR LARGE SPATIAL DATABASES
Authors: TSENG JUDY C.R. , HWANG TSONG-FENG , YANG WEI-PANG
Published: November 2004

The 2D string, proposed by Chang et al., is a spatial index structure which preserves the information of spatial relationships in a spatial database. In this paper, two new image retrieval algorithms for 2D string are proposed. The first one improves the retrieval efficiency, while the second reduces the space requirement. The performance analysis shows that the two methods perform much better than previous works especially when the spatial database is large.
CONTROL OF EYE AND ARM MOVEMENTS USING ACTIVE, ATTENTIONAL VISION
Authors: SANDON PETER A.
Published: November 2004

Recent related approaches in the areas of vision, motor control and planning are attempting to reduce the computational requirements of each process by restricting the class of problems that can be addressed. Active vision, differential kinematics and reactive planning are all characterized by their minimal use of representations, which simplifies both the required computations and the acquisition of models. This paper describes an approach to visually-guided motor control that is based on active vision and differential kinematics, and is compatible with reactive planning. Active vision depends on an ability to choose a region of the visual environment for task-specific processing. Visual attention provides a mechanism for choosing the region to be processed in a task-specific way. In addition, this attentional mechanism provides the interface between the vision and motor systems by representing visual position information in a 3-D retinocentric coordinate frame. Coordinates in this frame are transformed into eye and arm motor coordinates using kinematic relations expressed differentially. A real-time implementation of these visuomotor mechanisms has been used to develop a number of visually-guided eye and arm movement behaviors.
ANALYSIS OF THE NONLINEAR PHENOMENA IN A SUPERCONDUCTING DOUBLE-LOOP INTERFEROMETER CIRCUIT
Authors: FINGER L. , UHLMANN F.H.
Published: November 2004

We consider the nonlinear behaviour of a superconducting double-loop interferometer circuit (Double-loop SQUID). After some theoretical considerations we investigate the dynamical behaviour with Ljapunov exponents, return maps and bifurcation diagrams. An analysis of the chaotic behaviour is performed and a transition through intermittency is found in this case. It is shown that coexisting solutions of the double-loop SQUID leads to hysteretic behaviour. The influence of thermal noise on the chaotic behaviour is discussed.
COMPUTER SUPPORT FOR CONCEPTIONAL DESIGN
Authors: ROLLER DIETER
Published: November 2004

In this paper, requirements with respect to computer support for early design phases in product development are discussed. Here, support for quick engineering sketches and note taking plays an important role. As an approach to a solution, the architecture of the system GRIPSS, a Graphical Idea Processing and Sketching System, developed at the Computer Science Institute of Stuttgart University, is introduced. Then the sketching editor of this system is described in more detail. In particular the methods used for the interpretation of the hand drawn input are presented and characterised. Eventually, some prospects for further developments are given.
GENERAL PLANNING METHOD FOR MACHINE COORDINATION AND RENDEZVOUS
Authors: TROVATO KAREN I.
Published: November 2004

This paper describes a general method for representing and solving planning problems. The framework has well-defined subcomponents to simplify the problem using transforms, define costs over permissible motions, define illegal regions in the transformed space, and efficiently find optimal motions. The method fully exploits any a priori information and also provides a method to augment this information efficiently at runtime.

The method is powerful in that it can be used in arbitrarily high dimensional spaces, and has been used to solve non-holonomic problems efficiently and with ease. Examples will be given for moving robotic equipment optimally while avoiding obstacles, for automatically maneuvering a vehicle around obstacles, and for determining alternative rendezvous locations for machinery based on the separate constraints (time, space, fuel, etc.) of each. The rendezvous problem will also give optimal strategies, and precise paths.
TRANSIENT RESPONSE OF FAST ACTING SOLENOIDS IN AUTOMOTIVE APPLICATIONS
Authors: HONG H. , KREPEC T. , CHENG R.M.H.
Published: November 2004

The dynamic response of small solenoid-operated injectors employed for discharging the high-pressure gaseous fuel in diesel engines must be precisely controlled down to a few tenths of a millisecond. This paper shows how a simple but effective switching circuit can control the generation of the solenoid force to meet the stringent timing requirements for the opening and closing of such an injector. A mathematical model of the solenoid was established, to identify the force as a function of current and of the air gap, and for the purpose of simulating the full gas injection process. The model includes effects of eddy current and flux leakage losses in order to account for the hysteresis of the magnetization of the solenoid. Good agreement with the test results has been obtained, allowing the use of the simulation program for further injector optimization.
CLOSED-LOOP CHARACTERISTICS OF VOLTAGE-MODE-CONTROLLED PWM BOOST DC-DC CONVERTER WITH AN INTEGRAL-LEAD CONTROLLER
Authors: KAZIMIERCZUK MARIAN K. , CRAVENS ROBERT C.
Published: November 2004

A complete analysis of a voltage-mode-controlled pulse-width-modulated (PWM) boost DC-DC power converter is presented using a previously derived small-signal model for continuous conduction mode (CCM). All parasitic components such as the equivalent series resistance (ESR) of the filter capacitor, the ESR of the inductor, the transistor on-resistance, and the diode forward resistance and offset voltage are included in the model. A design procedure for an integral-lead controller including the loading effect of the voltage divider in the feedback loop is given. The Bode plots of the closed-loop control-to-output transfer function, input-to-output transfer function, input impedance, and output impedance are determined and illustrated for three values of the duty cycle. Step response plots of the PWM boost converter in the open-loop and closed-loop cases are shown for changes in line voltage and duty cycle.
CONCEPTS OF ELECTRONICALLY-CONTROLLED ELECTROMECHANICAL/MECHANOELECTRICAL STEER-, AUTODRIVE- AND AUTOABSORBABLE WHEELS FOR ENVIRONMENTALLY-FRIENDLY TRI-MODE SUPERCARS
Authors: FIJALKOWSKI BOGDAN T. , KROSNICKI JAN W.
Published: November 2004

Concepts of the electronically-controlled electromechanical/mechanoelectrical Steer-, Autodrive- and Autoabsorbable Wheels (SA2W) with their brushless Alternating Current-to-Alternating Current (AC-AC), Alternating Current-to-Direct Current-Alternating Current (AC-DC-AC) and/or Direct Current-to-Alternating Current (DC-AC)/Alternating Current-to-Direct Current (AC-DC) macroelectronic converter commutator (macro-commutator) wheel-hub motors/generators with the Application Specific Integrated Matrixer (ASIM) macroelectronic converter commutators (ASIM macrocommutators) and Application Specific Integrated Circuit (ASIC) microelectronic Neuro-Fuzzy (NF) computer (processor) controllers (ASIC NF microcontrollers) for environmentally-friendly tri-mode supercars (advanced ultralight hybrids) have been conceived by the first author and designed by both authors with the Cracow University of Technology’s Automotive Mechatronics Research and Development (R&D) Team. These electromechanical/mechanoelectrical wheel-hub motors/generators, respectively, for instance, can be composed of the outer rotor with the Interior Permanent Magnet (IPM) poles and the inner stator that has the three-phase armature winding. The macroelectronic converter commutator establishes the AC-AC cycloconverter, AC-DC rectifier-DC-AC inverter and/or DC-AC inverter/AC-DC rectifier ASIM macrocommutator. The microelectronic NF computer (processor) controller establishes the ASIC microcomputer-based NF microcontroller. By adopting continuous semiconductor bipolar electrical valves in the high-power ASIM, it has been able to increase the commutation (switching) frequency and reduce harmonic losses of the electromechanical/mechanoelectrical wheel-hub motors/generators, respectively.
STRUCTURED DESIGN OF A KNOWLEDGE-BASED MESSAGE DISSEMINATION SYSTEM
Authors: HIGA KUNIHIKO , AIKEN MILAM W. , SHENG OLIVIA R. LIU
Published: November 2004

Electronic Mail Systems (EMSs) have been a boon to organizational productivity, but these systems may not receive greater acceptance due in part to their general lack of robust system features. Particularly, the intractable problem of effective electronic mail dissemination management has largely eluded solution. This paper first provides a brief survey of several existing intelligent EMSs which seek to address the conundrum of mail management and then proposes an alternative solution which takes advantage of the unique characteristics of a knowledge base/database coupling to facilitate effective information sharing among members of an organization. This approach improves on prior Knowledge-Based Mail System (KMS) designs by (1) focusing on message dissemination management rather than on message receipt management, (2) separating the relatively static knowledge of message routing from the relatively dynamic knowledge of the organizational membership, and (3) incorporating a more comprehensive view of the semantic constraints involved in configuring distribution lists of message receivers through the use of the Structured Object Model (SOM) Methodology. The design concepts are illustrated by a prototype KMS, the Message Dissemination System (MDS).
DEBUGGING LOGIC-BASED REQUIREMENTS SPECIFICATIONS FOR SAFETY-CRITICAL SYSTEMS — A FRORL APPROACH
Authors: TSAI JEFFREY J.P. , LIU ALAN , NAIR KRISHNAKUMAR
Published: November 2004

Safety-critical systems are not only difficult to build, but also difficult to debug because they often have strict timing constraints and non-deterministic behavior. A correct and precise specification reduces the effort spent in testing and debugging the implemented system. This paper presents techniques of specification debugging and issues related to it. We introduce an approach to the debugging of a specification in FRORL (Frame and Rule Oriented Requirements Language), which supports non-determinism and non-monotonicity in a system. The approach aids the user in detecting and correcting the possible faults which can arise not only when writing the specification, but also after the verification of the specification.
COMPUTATIONAL GEOMETRY COLUMN 24
Authors: O'ROURKE JOSEPH
Published: November 2004

Open problems from the Tenth ACM Symposium on Computational Geometry and the Sixth Canadian Conference on Computational Geometry listed tersely.
PHASE CONJUGATED LASERS APPLIED TO X-RAY GENERATION
Authors: HACKEL L.A. , DANE C.B. , ZAPATA L.E. , HERMANN M.R.
Published: November 2004

Three laser systems that are being developed for use in X-ray generation which incorporate SBS phase conjugate mirrors are described. A 25 J/pulse Nd:glass laser is being developed for commercial proximity print X-ray lithography; a 0.5 J/pulse, 1.3 kHz pulse repetition frequency laser is being built for soft X-ray projection lithography; and a 1 kJ/pulse laser driver for a table top X-ray laser has been designed. The results of prototypical experimental investigations are presented and the basic design principles for high average power phase conjugated laser systems shared by each of these lasers are discussed.
OPTICAL PARAMETRIC PROCESSES IN NONLINEAR OPTICS
Authors: TANG C.L.
Published: November 2004

The basic concepts on optical parametric processes and recent results on practical parametric oscillators are discussed.
QUADRISECANTS OF KNOTS AND LINKS
Authors: KUPERBERG GREG
Published: November 2004

We show that every non-trivial tame knot or link in ℝ3 has a quadrisecant, i.e. four collinear points. The quadrisecant must be topologically non-trivial in a precise sense. As an application, we show that a nonsingular, algebraic surface in ℝ3 which is a knotted torus must have degree at least eight.
RANDOM KNOTS AND ENERGY: ELEMENTARY CONSIDERATIONS
Authors: BUCK GREGORY R.
Published: November 2004

We present two constructions of random knots. The first gives piecewise linear knots. It has a parameter (which can be a function), which allows one some control of the expected shape of the knot. The second construction uses Fourier series to construct smooth random knots. We then discuss preliminary notions of the interplay between random knots and the energy of a knot.
OSCILLATIONS IN DELAY DIFFERENTIAL EQUATION MODEL OF REPRODUCTIVE HORMONES IN MEN WITH COMPUTER SIMULATIONS
Authors: DAS PRITHA , ROY A.B.
Published: November 2004

We produce here a delay model to explain the control of testosterone secretion. We have modified our earlier model by incorporating one negative feedback function which explains the inhibition of the pituitary secretion of the hormone LH (Luteinizing hormone) by the local testosterone concentration. We have derived the conditions for local asymptotic stability and switching to instability of the steady state. The length of the delay preserving the stability has also been derived. Lastly the conditions for instability and bifurcation results have been derived for the linearized model. Phase portraits of the original nonlinear model showing stable limit cycle have been simulated.
ON THE RELATION BETWEEN CATASTROPHIC INTERFERENCE AND GENERALIZATION IN CONNECTIONIST NETWORKS
Authors: LEWANDOWSKY S.
Published: November 2004

Catastrophic interference refers to the frequent inability of connectionist networks to retain old memories in the presence of new information. Although solutions to the catastrophic interference problem exist, most involve the creation of semi-distributed (only partially overlapping) representations. This has given rise to the new concern that other, desirable properties that derive from the distributed nature of networks might be lost in exchange for reduced interference. For example, it has been feared that networks may lose the ability to generalize if interference is reduced through the creation of semi-distributed representations. This article examines the close conceptual relation between interference and generalization, and reports results from simulations that examined forgetting and generalization in a prototype learning situation. Two classes of solutions to catastrophic interference were investigated: Interference-reduction techniques that rely on rearranging weights into a more robust pattern were found to leave generalizability intact. An alternative technique that reduces interference by reducing the overlap between receptive fields of static hidden units was found to trade off resistance to forgetting against a reduced ability to generalize.
LEVELS OF SIGNIFICANCE FOR FUZZY IMPLICATION
Authors: BANDLER WYLLIS , HRUSKA SUSAN I.
Published: November 2004

Fuzzy implication operators have been proposed as a tool for measuring the strength of connections between recorded concepts. Hasse diagrams are used to graphically illustrate the sometimes complicated relationships between such concepts. Establishing measures of significance for fuzzy implications is the focus of this paper. Lower and upper bounds for mean implication using the Kleene-Dienes operator are established. Examples of the intended use of these measures are given.
PROBABILITY INTERVALS: A TOOL FOR UNCERTAIN REASONING
Authors: DE CAMPOS LUIS M. , HUETE JUAN F. , MORAL SERAFIN
Published: November 2004

We study probability intervals as an interesting tool to represent uncertain information. A number of basic operations necessary to develop a calculus with probability intervals, such as combination, marginalization, conditioning and integration are studied in detail. Moreover, probability intervals are compared with other uncertainty theories, such as lower and upper probabilities, Choquet capacities of order two and belief and plausibility functions. The advantages of probability intervals with respect to these formalisms in computational efficiency are also highlighted.
COMMUTATIVE IMPLICATIONS ON COMPLETE LATTICES
Authors: WU WANGMING
Published: November 2004

This paper is devoted to the investigation of commutative implications on a complete lattice L. It is proved that the disjunctive normal form (DNF) of a linguistic composition * is included in the conjunctive normal form (CNF) of that *, i.e., DNF(*) ≤ CNF(*) holds, for a special family of t-norms, t-conorms and negations induced by commutative implications.
PROPORTIONAL HAZARDS MODEL — AN APPLICATION TO POWER SUPPLY CABLES OF ELECTRIC MINE LOADERS
Authors: KUMAR DHANANJAY , KLEFSJÖ BENGT
Published: November 2004

The electric power supply cable is one of the most critical components of an electric mine loader. The effects of operating conditions such as fault types, cable types, numbers and types of repair done, the machines on which these cables are used, are analyzed using the proportional hazards model. The relatively important operating conditions influencing the life length of the cable are identified and their magnitudes are estimated. Before fitting any model to the data, simple graphical tools have been used in formulating covariates and selecting the suitable model. The proportional hazards model is found to be an effective tool for analyzing the effects of covariates. Graphical methods have been used to test the goodness-of-fit of the proportional hazards model.
ESTIMATION OF THE MEDIAN SAFETY FACTOR IN A LOGNORMAL STRESS-STRENGTH MODEL
Authors: PHAM-GIA T. , TURKKAN N.
Published: November 2004

Both classical and Bayesian approaches are used in this article to estimate the median safety factor and the median coefficient of variation of the frequently used engineering stress-strength model, with lognormal distributions for both stress and strength. A numerical example on fire loads studies in civil engineering illustrates some of these results. A computer program, developed and tested by our group, is available upon request.
Gender differences in small intestinal perfusion following trauma hemorrhage: the role of endothelin-1
Authors: Ba Zheng F. , Shimizu Tomoharu , Szalay Laszlo , Bland Kirby I. , Chaudry Irshad H.
Published: November 2004

Although gender differences in intestinal perfusion exist following trauma-hemorrhage (T-H), it remains unknown whether endothelin-1 (ET-1) plays any role in these dimorphic responses. To study this, male, proestrus female (female), and 17β-estradiol (E2)-treated male rats underwent midline laparotomy, hemorrhagic shock (blood pressure 40 mmHg, 90 min), and resuscitation (Ringer lactate, 4× shed blood volume, 1 h). Two hours thereafter, intestinal perfusion flow (IPF) was measured using isolated intestinal perfusion. The IPF in sham-operated males was significantly lower than those in other groups and decreased markedly following T-H. In contrast, no significant decrease in IPF was observed in females and E2 males following T-H. The lower IPF in sham-operated males was significantly elevated by ETA receptor antagonist (BQ-123) administration and was similar to that seen in sham-operated females. The decreased IPF in males after T-H was also attenuated by BQ-123 administration. The intestinal ET-1 levels in sham-operated males were significantly higher than in other groups. Although plasma and intestinal ET-1 levels increased significantly after T-H in all groups, they were highest in males. Plasma E2 levels in females and E2 males were significantly higher than in males; however, they were not affected by T-H. There was a negative correlation between plasma ET-1 and E2 following T-H. Thus ET-1 appears to play an important role in intestinal perfusion failure following T-H in males. Because E2 can modulate this vasoconstrictor effect of ET-1, these findings may partially explain the previously observed salutary effect of estrogen in improving intestinal perfusion following T-H in males.