bluuebunny/crossref_metadata_2025 huggingface dataset:
TUMBLING MOTION OF ELLIPTICAL PARTICLES IN VISCOUS TWO-DIMENSIONAL FLUIDS
Authors: RISTOW GERALD H.
Published: July 2002

The settling dynamics of spherical and elliptical particles in a viscous Newtonian fluid are investigated numerically using a finite difference technique. The terminal velocity for spherical particles is calculated for different system sizes and the extrapolated value for an infinite system size is compared to the Oseen approximation. Special attention is given to the settling and tumbling motion of elliptical particles where their terminal velocity is compared with the one of the surface equivalent spherical particle.
STRUCTURAL PROPERTIES OF CARBON NANORODS: MOLECULAR-DYNAMICS SIMULATIONS
Authors: ERKOÇ ŞAKIR , MALCIOĞLU OSMAN BARIŞ
Published: July 2002

The formation of carbon nanorods from various types of carbon nanotubes has been investigated by performing molecular-dynamics computer simulations. Calculations have been realized by using an empirical many-body potential energy function for carbon. It has been found that carbon nanorod formed from carbon nanotubes with different chirality is not stable even at low temperature.
HPF LIBRARY AND COMPILER SUPPORT FOR HALOS IN DATA PARALLEL IRREGULAR COMPUTATIONS
Authors: BRANDES THOMAS
Published: July 2002

On distributed memory architectures data parallel compilers emulate the global address space by distributing the data onto the processors according to the mapping directives of the user and by generating automatically explicit inter-processor communication. A shadow is additionally allocated local memory to keep on one processor also non-local values of the data that is accessed or defined by this processor. While shadow edges are already well studied for structured grids, this paper focuses on its use for applications with unstructured grids where updates on the shadow edges involve unstructured communication with complex communication schedules.

The use of shadow edges is considered for High Performance Fortran (HPF) as the de facto standard language for writing data parallel programs in Fortran. A library with a HPF binding provides the explicit control of unstructured shadows and their communication schedules, also called halos. This halo library allows writing HPF programs with a performance close to hand-coded message-passing versions but where the user is freed of the burden to calculate shadow sizes and communication schedules and to do the exchanging of data with explicit message passing commands.

In certain situations, the HPF compiler can create and use halos automatically. This paper shows the advantages and also the limits of this approach. The halo library and an automatic support of halos have been implemented within the ADAPTOR HPF compilation system. The performance results verify the effectiveness of the chosen approach.
COMPILING DATA-PARALLEL PROGRAMS TO A DISTRIBUTED RUNTIME ENVIRONMENT WITH THREAD ISOMIGRATION
Authors: ANTONIU GABRIEL , BOUGÉ LUC , NAMYST RAYMOND , PÉREZ CHRISTIAN
Published: July 2002

The compilation of data-parallel languages is traditionally targeted to low-level runtime environments: abstract processors are mapped onto static system processes, which directly address the low-level communication library. Alternatively, we propose to map each HPF abstract processor onto a "lightweight process" (thread) which can be dynamically migrated between nodes together with the data it manages, under the supervision of some external scheduler. We discuss the pros and cons of such an approach and the facilities which must be provided by the multithreaded runtime. We describe a prototype HPF compiling system built along these lines, based on the Adaptor HPF compiler and using the PM2 multithreaded runtime environment.
ROSE: COMPILER SUPPORT FOR OBJECT-ORIENTED FRAMEWORKS
Authors: QUINLAN DAN
Published: July 2002

ROSE is a preprocessor generation tool for the support of compile time performance optimizations of general object-oriented frameworks. Within this work ROSE is being applied first to Overture, a serial/parallel object-oriented framework for solving partial differential equations in two and three space dimensions. The optimization of the interactions between objects within Overture is of particular interest since the Overture applications can be computationally large (many millions of mesh points and iterating over thousands of time-steps). Unfortunately, optimizations that might be obvious to the framework developer or application developer (e.g. cache based optimizations), due to the precise semantics of the framework's abstractions, are often lost through the C++ compiler's inability to recognize or leverage such semantics. Preprocessing steps can be used to introduce transformations using the semantics of a framework's abstractions, but the development of such a preprocessor tool is particularly complicated for a general object-oriented language such as C++. This paper shows how such framework specific preprocessors can be automatically generated.

In this paper we briefly present Overture with some examples, and present our approach toward optimizing the performance for Overture and the A++P++ array class abstractions upon which Overture depends. The results we present show that the semantics of the abstractions represented within Overture and the A++P++ array class library can be used to generate a preprocessor using ROSE. The results demonstrate the performance of an Overture application with and without such a preprocessing step, the final performance with preprocessing is equivalent to that of optimized C and Fortran 77. By design, ROSE is general in its application to any object-oriented framework or application and is in no way specific to Overture.
WHERE DOES THE SPEEDUP GO: QUANTITATIVE MODELING OF PERFORMANCE LOSSES IN SHARED-MEMORY PROGRAMS
Authors: KIM SEON WOOK , EIGENMANN RUDOLF
Published: July 2002

Even fully parallel shared-memory program sections may perform significantly below the ideal speedup of P on P processors. Relatively little quantitative information is available about the sources of such inefficiencies. In this paper we present a speedup component model that is able to fully account for sources of performance loss in parallel program sections. The model categorizes the gap between measured and ideal speedup into the four components memory stalls, processor stalls, code overhead, and thread management overhead. These model components are measured based on hardware counters and timers, with which programs are instrumented automatically by our compiler. The speedup component model allows us, for the first time, to quantitatively state the reasons for less-than-optimal program performance, on a program section basis. The overhead components are chosen such that they can be associated directly with software and hardware techniques that may improve performance. Although general, our model is especially suited for the analysis of loop-oriented programs, such as those written in the OpenMP API. We have applied this model to compare three parallel code generation schemes for the Polaris parallelizing compiler. It helps us answer questions such as, what sources of inefficiencies are present in compiler-parallelized programs. To discuss the question we have also implemented an alternative, thread-based code generation method.
MASSIVE AXIAL GAUGE IN THE EXACT RENORMALIZATION GROUP APPROACH
Authors: PANZA P. , SOLDATI R.
Published: July 2002

The Exact Renormalization Group (ERG) approach to massive gauge theories in the axial gauge is studied and the smoothness of the massless limit is analysed for a formally gauge invariant quantity such as the Euclidean Wilson loop.
ELECTRONIC THEORY FOR ELECTRON-DOPED CUPRATE SUPERCONDUCTORS: d-WAVE SUPERCONDUCTIVITY AND THE PHASE DIAGRAM
Authors: MANSKE D. , EREMIN I. , BENNEMANN K. H.
Published: July 2002

Using the one-band Hubbard Hamiltonian we determine various basic properties of the electron-doped cuprate superconductor Nd 2-x Ce x CuO 4 for a spin-fluctuation-induced pairing mechanism. We find a narrow range of superconductivity and, most importantly, like for hole-doped cuprates dx2-y2 -symmetry for the superconducting order parameter. The superconducting transition temperatures Tc(x) for various electron doping concentrations x are calculated to be much smaller than for hole-doped cuprates due to the different energy dispersion and a flat band well below the Fermi level. We find that lattice disorder may sensitively distort the dx2-y2 -symmetry via electron-phonon interaction yielding a finite isotope exponent α0.
LARGE DEVIATIONS AND THE RANDOM ENERGY MODEL
Authors: DORLAS T. C. , WEDAGEDERA J. R.
Published: July 2002

We present a simple proof of the formula for the free energy of the random energy model using a large deviation property which holds almost surely with respect to the randomness. This proof is extended to the case with external magnetic field leading to the solution of a model with higher-order ferromagnetic term. It is shown that this model is useful for Sourlas' application to error-correcting codes as was already pointed out in a recent letter by the authors.
RELAXATION OF EXCITONS INTO CHARGE-SEPARATED PAIRS IN PbBr2 AND PbCl2 CRYSTALS
Authors: IWANAGA MASANOBU , WATANABE MASAYUKI , HAYASHI TETSUSUKE
Published: July 2002

We have studied the relaxed state of excitons in PbBr 2 and PbCl 2 crystals from the photoluminescence (PL) properties at low temperatures. The analysis of decay curves of intrinsic PL band reveals that excitons relax into charge-separated pairs of a self-trapped electron and a self-trapped hole in both crystals. The relaxation of excitons, found experimentally for the first time, is ascribed to the repulsive correlation via acoustic phonons between the electron and hole.
ENHANCED POWER-LAW SINGULARITY BY LIGHT FIELD IN QUANTUM WIRES
Authors: INOUE JUN-ICHI , SHIMIZU AKIRA
Published: July 2002

We discuss an interplay of light field and electron interactions in one-dimensional systems. After constructing the Hamiltonian that includes the effect of a pump beam, probe absorption is discussed using the linear response theory with the bosonization technique. This describes a nonlinear optical property of the system. We show that (1) the absorption spectrum of the probe beam follows a power-law and (2) the power depends on the intensity of the pump beam, where electron correlation plays important roles. The result can be applied to other response functions, e.g. for transport phenomena.
STE LUMINESCENCE FROM THE SUPERSTRUCTURE PHASE Na6CdCl8 IN NaCl:Cd2+ CRYSTALS
Authors: NAKAGAWA H. , KISHIGAMI S.
Published: July 2002

Optical Absorption and luminescence studies have been conducted in Nacl crystals contining various amounts of CdCl 2 in order to investigate the electronic excited states and their lattice relaxation processes in Suzuki superstructure lattice. X-ray diffraction measurements have been also made to confirm the presence of the Suzuki phase and to determine its detailed structure. Two broad absorption structures are observed in the energy region of 4.25-5.0 eV (LE) and of 5.0-6.0 eV (HE). With excitation in the LE region, three emission bands are produced at 2.64 (BG), 3.14 (V) and 3.56(UV1)eV. They are attribute to the Cd 2+ impurity-related centers. In case of excitation in the HE region, two prominent emission bands are observed at 2.76 (B) and 2.08 (Y) eV. Taking into consideration the experimental results of X-ray diffraction, thermal treatment and Cd 2+ concentration dependence, the B- and Y-emission are connected to the STE in Suzuki lattice of small and large sizes, respectively.
Crystal Growth of Al-doped ZnO Films under Different Sputtering Conditions
Authors: Goh E. G. , Gong H.
Published: July 2002

Al -doped ZnO (AZO) films were deposited on glass substrate using radio-frequency (RF) magnetron sputtering. It is found that the crystal orientation in the films is dependent on the ambience during the sputtering. The electrical and optical properties are related to the structure of the as-sputtered films at various growth conditions. The as-sputtered films were further heat-treated in an nitrogen ambience and the resultant film properties due to the post-thermal annealing were studied as well. Although the x-ray diffraction revealed that all the films have a distinct (002)-ZnO orientation, the Scanning Electron Microscope (SEM) showed that there's a distinct difference in surface topology when the partial pressure of both gases were increased; from needle-like shaped to granular in the N 2-mixed ambience and from plate-like to wedge-shaped in the NH 3-mixed ambience.
THE SPECIFIC HEAT OF A FERMI GAS AT LOW TEMPERATURE: A CLOSER LOOK AT THE lnT BEHAVIOR
Authors: REBEI A. , HITCHON W. N. G.
Published: July 2002

At finite temperature, a Fermi gas can have states that simultaneously hold a particle and a hole with a finite probability. This gives rise to a new set of diagrams that are absent at zero temperature. The so called "anomalous" diagram is just one of the new diagrams. We have already studied the contribution of these new diagrams to the thermodynamic potential (Phys. Lett.A224, 127 (1996)). Here we continue that work and calculate their effect on the specific heat. We will also calculate the finite temperature contribution of the ring diagrams. We conclude that the ln T behavior of the specific heat due to exchange gets canceled by the new contribution of the new diagrams, and that screening is not essential to resolve this anomaly.
IR SPECTRAL INVESTIGATION OF xCuO(100-x)[2B2O3·TeO2] GLASS SYSTEM
Authors: ARDELEAN I. , CICEO-LUCACEL RALUCA , BRATU I.
Published: July 2002

Samples belonging to x CuO (100-x)[2 B 2 O 3· TeO 2] vitreous system with 0≤x≤30 mol% CuO were investigated by FTIR spectroscopy in order to obtain information about the influence of CuO on the local order from 2 B 2 O 3· TeO 2 glass matrix. The interpretation of the obtained vibrational spectra revealed the presence of BO 3 units and boroxol rings in the structure of investigated borate-tellurite glasses. No BO 4 units were detected.
A SIMPLE MODEL FOR OBTAINING OPTICAL CONSTANTS OF POROUS SILICON
Authors: TORRES JAIME , GIRALDO JAIRO
Published: July 2002

A simple method is proposed to calculate optical constants from porous silicon (PS) thin films, out of the simulation of normal incidence reflection spectrums. In the optical system used in this model, PS one considers as a homogeneous uniform thin film when deposited upon a substrate with semi-infinite dimensions. The PS and Substrate refractive indexes are obtained using the Simple Harmonic Oscillator Model, proposed by Wemple and DiDomenico. In addition, the absorption coefficient and sample thickness are also be obtained. The model to calculate the optical constants of some samples prepared at different anodisation times is used.
LUMINESCENT PROPERTIES OF SOL-GEL DEPOSITED Eu:TiO2 THIN FILMS
Authors: GARCIA-ROCHA M. , CONDE-GALLARDO A. , HERNANDEZ-CALDERON I. , PALOMINO-MERINO R.
Published: July 2002

In this work we show the results on tile growth and optical characterization of TiO 2 thin films doped with Eu atoms. Eu:TiO2 films were grown at room temperature with different Eu concentrations by sol-gel on Si Corning glass substrates. A different crystalline structure is developed for the films deposited on Corning glass than those deposited on Si as observed from x-ray diffraction experiments. Room and low temperature photoluminescence (PL) was measured by using two different lines (325 and 442 nm) of a HeCd laser. A strong PL signal associated to the 5 D 0→7 F 2 transition from Eu +3 was observed. A better emission was obtained from those films deposited on Si substrates, Finally, the evolution of the PL signal is studied when the samples are annealed at different temperatures in O 2 atmosphere.
ELASTIC BEHAVIOR OF MELT-POWDER-MELT-GROWTH PROCESSED YBa2Cu3O7-δ
Authors: REDDY P. VENUGOPAL , MURAKAMI M.
Published: July 2002

The ultrasonic velocity measurements of a Y-Ba-Cu-O material, prepared by Melt-Powder-Melt-Growth process (MPMG) with Nd-123 as a seed material, known as MPMG-II material, have been undertaken by the pulse transmission technique over a temperature range 80–300 K. It has been observed that the MPMG-II material, in contrast to Y-123 material also prepared by the Melt-Powder-Melt-Growth method without using any seed material, designated as MPMG-II, exhibits a very high Young's and rigidity modului, which are comparable with those of single crystalline ones. Further, it has also been observed that the longitudinal velocity is found to increase continuously with decreasing temperature right up to liquid nitrogen temperature, i.e. 80 K, without showing any anomaly, whatsoever, thereby indicating that the behavior resembles a normal solid having normal behavior. From these two observations, it has been speculated that MPMG-II material may be free from all types of lattice instabilities and that it may be approaching mechanically a single crystalline Y-123 material.
CHAOTIC AND HYPERCHAOTIC MOTION OF A CHARGED PARTICLE IN A MAGNETIC DIPOLE FIELD
Authors: DE ALCANTARA BONFIM O. F. , GRIFFITHS DAVID J. , HINKLEY SASHA
Published: July 2002

The motion of a charged particle in the field of a magnetic dipole is studied by numerically integrating the equations of motion. The widely believed picture in which a bound particle corkscrews about a line of magnetic flux, bouncing back along the same line as it nears the poles, is shown to be a substantial over-simplification. The nature of the trajectory depends on the energy of the particle, but whatever the energy this picture is not observed. For low energies the particle will corkscrew towards the poles, while at the same time drifting laterally with a variable speed in a quasiperiodic fashion. For intermediate energies the motion is found to be chaotic, and for higher energies it becomes hyperchaotic. In the equatorial plane only quasiperiodic orbits can occur. If the magnetic dipole moment is slowly varying, the particle undergoes chaotic motion even in the equatorial plane, but only for high energies.
CONTROLLING A BOUNCING BALL
Authors: VINCENT THOMAS L. , MEES ALISTAIR I.
Published: July 2002

A ball bouncing on a vibrating plate is surely one of the simplest physical systems that can produce chaotic motion, yet it is a prototype for a large class of mechanical systems. We wish to design a control algorithm for the plate motion so that the ball, starting at rest on the plate, can be bounced up to a prescribed periodic orbit, and maintained bouncing there. Keeping the amplitude of the vibrating plate fixed, we use the frequency of the plate as a control input. We examine two approaches for designing the controller. The first is classical LQR design and the second is a variant of a "greedy" method which only looks a short distance ahead in time. Using both of these methods we attempt control by linearizing an analytic model, the so-called high-bounce approximation of the ball map, and also by using a data-derived approximation to the true system. These approximate controllers are applied to a more accurate continuous system model of the bouncing ball. Encouragingly, both controllers perform well in spite of the approximations in their construction. The greedy control method appears to be more robust in certain situations.
LOWER BOUNDS FOR THE STABILITY DEGREE OF PERIODIC SOLUTIONS IN FORCED NONLINEAR SYSTEMS
Authors: GIOVANARDI L. , BASSO M. , GENESIO R. , TESI A.
Published: July 2002

In this paper the problem of local exponential stability of periodic orbits in a general class of forced nonlinear systems is considered. Some lower bounds for the degree of local exponential stability of a given periodic solution are provided by mixing results concerning the analysis of linear time-varying systems and the real parametric stability margin of uncertain linear time-invariant systems. Although conservative with respect to the degree of stability obtainable via the Floquet-based approach, such lower bounds can be efficiently computed also in cases where the periodic solution is not exactly known and the design of a controller ensuring a satisfactory transient behavior is the main concern. The main features of the developed approach are illustrated via two application examples.
THE SETS OF POINTS WITH BOUNDED ORBITS FOR GENERALIZED CHEBYSHEV MAPPINGS
Authors: UCHIMURA KEISUKE
Published: July 2002

We study the dynamical systems given by generalized Chebyshev mappings [Formula: see text] and show that (1) the set of points with bounded orbits of Fc(z) is connected and its complement in C∪{∞} is simply connected if and only if -4 ≤ c ≤ 2; (2) if c > 2, then the set of points with bounded orbits of Fc(z) is Cantor set.

These results are the analogue of the theory of filled Julia sets of quadratic polynomials in one complex variable. We show that the mapping Fc(z) has relation to an important holomorphic map on the complex projective space P2.
CAN BLACK HOLES DECAY TO NAKED SINGULARITIES?
Authors: DAS SAURYA , GEGENBERG J. , HUSAIN V.
Published: July 2002

We investigate thermodynamic properties of two types of asymptotically anti-de Sitter spacetimes: black holes and singular scalar field spacetimes. We describe the possibility that thermodynamic phase transitions can transform one spacetime into another, suggesting that black holes can radiate to naked singularities.
CHAOTIC INFLATION WITH TIME-VARIABLE SPACE DIMENSIONS
Authors: NASSERI FOROUGH , RAHVAR SOHRAB
Published: July 2002

Assuming the space dimension is not constant but decreases during the expansion of the Universe, we study chaotic inflation with the potential m2ϕ2/2. Our investigations are based on a model Universe with variable space dimensions. We write down field equations in the slow-roll approximation, and define slow-roll parameters by assuming the number of space dimensions decreases continuously as the Universe expands. The dynamical character of the space dimension shifts the initial and final value of the inflaton field to larger values. We obtain an upper limit for the space dimension at the Planck length. This result is in agreement with previous works for the effective time variation of the Newtonian gravitational constant in a model Universe with variable space dimensions.
A FEW ISSUES REGARDING OXIDE SURFACES
Authors: JUPILLE JACQUES
Published: July 2002

This comment article introduces a series of four review papers about oxide surfaces which are published in this journal.1–4It is emphasized that oxides concern a very broad area of applications and that the examination of the extreme surface of these materials is crucial to the understanding of an increasing number of phenomena.
ADSORPTION AND ABSORPTION OF H ON Ni(111): A THEORETICAL STUDY BASED ON MOLECULAR ORBITALS
Authors: ZAPATA SILVINA , CASTELLANI NORBERTO J.
Published: July 2002

The adsorption of monoatomic H on Ni(111) was studied theoretically, taking into account the possibility of H diffusion and eventual incorporation of H as an interstitial. The desorption of H 2 as a diffusion-controlled process from the bulk and the influence on adsorption properties due to a H sub-surface phase very near to the adsorbed phase were considered. Our semiempirical molecular orbital approach allows us to analyze the results from an electronic structure perspective, showing that in general the H–Ni bond is weakened by the presence of the H sublayer.
DC ELECTRICAL PROPERTIES OF SOME CHALCOGENIDE GLASSY ALLOYS OF THE SYSTEMSe100-xInx
Authors: EL-HASSAN S. ABOU
Published: July 2002

DC electrical properties of the system Se100-xInx(x=5, 10, 15, 20 at. %) have been investigated I–V characteristics of this system are discussed in terms of the Poole–Frenkel and the Schottky effect. The jump distance (d), charge carrier concentration (n) and trap depth (φ) have been deduced for the system. According to the Arrhenius equation of conductivity, the activation energy of conduction Δw1and Δw2for the two arms of conductivity has been found to be in the range of 0.18–1.2 eV. Both the mobility (μ) and diffusion coefficients are calculated for different compositions at different ambient temperatures. The activation energy due to the mobility (ΔU) and diffusion (ΔQ) mechanisms has been deduced and the values range from 0.02 to 0.4 eV. The behavior of ΔW1, ΔU and ΔQ has the same trend with composition, which indicates that the conduction mechanism is controlled by one type of process. The Meyer–Neldel rule has been applied to our results and a confirmation of this rule has been found.
BELIEF REVISION FOR ADAPTIVE INFORMATION FILTERING AGENTS
Authors: LAU RAYMOND , TER HOFSTEDE ARTHUR H. M. , BRUZA PETER D.
Published: July 2002

Agent-based information filtering alleviates the problem of information overload on the Internet by proactively scanning through the incoming stream of information on behalf of the users. Nevertheless, users' information needs will change over time. Therefore, it is essential for the information filtering agents to learn and adapt to the users' changing information needs in order to maintain the accuracy of the filtering process. Applying logic-based representation and adaptation to adaptive information filtering agents is promising since the semantic relationships among information items can be captured and reasoned about during the agents' learning and adaptation processes. This opens the door to a more responsive reinforcement learning than can be obtained from a purely statistical approach. The AGM belief revision paradigm that models rational and minimal change of an agent's beliefs offers a sound theoretical foundation for constructing the learning components of adaptive information filtering agents. This paper describes a symbolic framework for representing domain knowledge in an adaptive information filtering agent, and illustrates how the AGM belief revision paradigm can be applied to develop the agent's learning mechanism.
NEUROLOGICALLY INTACT FRACTURE-DISLOCATIONS OF THE THORACOLUMBAR SPINE
Authors: Öğün Tunç Cevat , Özdemir Mustafa , Arazi Mehmet , Kapicioğlu M. I. Safa , Kutlu Abdurrahman
Published: July 2002

Purpose: In this study, we presented ten neurologically intact fracture-dislocations of the thora-columbar spine which are extremely rare, and reported the results of treatment. Methods: Ten fracture-dislocations of the thoracolumbar spine were treated in a period of nine years. Surgical reduction and stabilization were performed in six patients. Four patients rejected surgery and were treated conservatively. The average follow-up was 55 months. Results: During the conservative course of treatment, surprisingly, the neurologic status did not deteriorate. However, varying degrees of pain and roentgenographic deterioration of spinal alignment and canal compromise were detected. In the operated group, there were also no deteriorations in the neurologic status and the roentgenograms revealed no serious loss of reduction. One of the patients from the conservative group and two of the patients from the operative group were able to return to their pre-injury works. Conclusion: Surgical treatment was satisfactory, both clinically and radiologically, in a group of patients with thoracolumbar fracture-dislocations. Well-known drawbacks of conservative treatment, including long-term bed-rest, social and economic losses and long-lasting treatment, led us to favor surgical treatment.
ON THE LARGE TIME BEHAVIOR OF QUANTUM SYSTEMS
Authors: AREF'EVA I. YA. , VOLOVICH I. V.
Published: July 2002

There exists the well-known approximate expression describing the large time behavior of matrix elements of the evolution operator in quantum theory: < U(t)>≃ exp (at). This expression plays the crucial role in considerations of problems of quantum decoherence, radiation, decay, scattering theory, stochastic limit, derivation of master and kinetic equations etc. This expression was obtained in the Weisskopf–Wigner approximation and in the van Hove (stochastic) limit. We derive the exact general formula which includes the higher order corrections to the above approximate expression: = exp (At+B+C(t)). The constants A and B and the oscillating function C(t) are computed in perturbation theory. The method of perturbation of spectra and renormalized wave operators is used. The formula is valid for a general class of Hamiltonians used in statistical physics and quantum field theory.
TREE TRIANGULAR CODING IMAGE COMPRESSION ALGORITHMS
Authors: PRASAD MUNAGA V. N. K. , SHUKLA K. K.
Published: July 2002

This paper presents new algorithms for image compression that are an improvement on the recently published Binary Tree Triangular Coding (BTTC). These algorithms are based on recursive decomposition of the image domain into triangles where the new triangle vertex is located at the point of maximum prediction error and does not require the constraints of right-angled isosceles triangle and square image as in previous algorithm. These algorithms execute in O(n log n) for encoding and θ(n) for decoding, where n is the number of image pixels. Simulation results show that the new algorithms have a significant execution time advantage over conventional BTTC while providing a quality of the reconstructed image as good as BTTC. This improvement is obtained by eliminating a major weakness of the standard BTTC, wherein the algorithm does not utilize the point of maximum error for domain decomposition despite performing an exhaustive search (in the worst case) over the triangular domain.
VISUALIZATION EXPERIMENT OF MASS TRANSPORT IN PULMONARY VENTILATION INSIDE BRONCHIAL TUBE MODEL
Authors: MOCHIZUKI S. , TOGASHI Y. , MURATA A. , YANG W. J.
Published: July 2002

Flow visualization in reciprocating flow inside branching tubes was performed to investigate the mechanism of axial gas exchange in the human lung system. A bronchial tube model is employed which is geometrically similar to the average human lung system. Water is used as the working fluid. The ranges of Reynolds and Womersley numbers in the present study correspond to those of normal human respiration and HFV (high frequency ventilation), respectively. It is revealed that the axial gas exchange phenomenon occurring in the human lung system is governed by a "trap-and-release" mechanism caused by the formation-and-destruction of the separation regions, which are formed on the wall of the parent tube and or daughter tubes, depending on the direction of the reciprocating flow.
An incremental access method for ViewCache
Authors: Roussopoulos Nicholas
Published: July 2002

A
ViewCache
is a stored collection of pointers pointing to records of underlying relations needed to materialize a view. This paper presents an
Incremental Access Method (IAM)
that amortizes the maintenance cost of ViewCaches over a long time period or indefinitely. Amortization is based on
deferred
and other update propagation strategies. A deferred update strategy allows a ViewCache to remain outdated until a query needs to selectively or exhaustively materialize the view. At that point, an incremental update of the ViewCache is performed. This paper defines a set of conditions under which incremental access to the ViewCache is cost effective. The decision criteria are based on some dynamically maintained cost parameters, which provide accurate information but require inexpensive bookkeeping.

The IAM capitalizes on the ViewCache storage organization for performing the update and the materialization of the ViewCaches in an interleaved mode using one-pass algorithms. Compared to the standard technique for supporting views that requires reexecution of the definition of the view, the IAM offers significant performance advantages. We will show that under favorable conditions, most of which depend on the size of the incremental update logs between consecutive accesses of the views, the incremental access method outperforms query modification. Performance gains are higher for multilevel ViewCaches because all the I/O and CPU for handling intermediate results are avoided.
Double iterative framework for flow-sensitive interprocedural data flow analysis
Authors: Forgács István
Published: July 2002

Compiler optimization, parallel processing, data flow testing, and symbolic debugging can benefit from interprocedural data flow analysis. However, the live, reaching definition, and most summary data flow problems are theoretically intractable in the interprocedural case. A method is presented that reduces the exponential time bound with the help of an algorithm that solves the problem in polynomial time. Either the resulting sets contain precise results or the missing (or additional) results do not cause any problems during their use. We also introduce the double iterative framework, where one procedure is processed at a time. The results of the intraprocedural analysis of procedures then propagates along the edges of the call multi-graph. In this way the intra and interprocedural analyses are executed alternately until there is no change in any result set. This method can be applied to any known interprocedural data flow problem. Here the algorithms for the kill, live variables, and reaching definitions problems are presented. Besides for precision, the algorithms can be used for very large programs, and since inter and intraprocedural analyses can be optimized separately, the method is fast as well.
Formal query languages for secure relational databases
Authors: Winslett Marianne , Smith Kenneth , Qian Xiaolei
Published: July 2002

The addition of stringent security specifications to the list of requirements for an application poses many new problems in DBMS design and implementation, as well as database design, use, and maintenance. Tight security requirements, such as those that result in silent masking of witholding of true information from a user or the introduction of false information into query answers, also raise fundamental questions about the meaning of the database and the semantics of accompanying query languages. In this paper, we propose a belief-based semantics for secure databases, which provides a semantics for databases that can “lie” about the state of the world, or about their knowledge about the state of the world, in order to preserve security. This kind of semantics can be used as a helpful retrofit for the proposals for a “multilevel secure” database model (a particularly stringent form of security), and may be useful for less restrictive security policies as well. We also propose a family of query languages for multilevel secure relational database applications, and base the semantics of those languages on our semantics for secure databases. Our query languages are free of the semantic problems associated with use of ordinary SQL in a multilevel secure context, and should be easy for users to understand and employ.
The integrality of speech in multimodal interfaces
Authors: Grasso Michael A. , Ebert David S. , Finin Timothy W.
Published: July 2002

A framework of complementary behavior has been proposed which maintains that direct-manipulation and speech interfaces have reciprocal strengths and weaknesses. This suggests that user interface performance and acceptance may increase by adopting a multimodal approach that combines speech and direct manipulation. This effort examined the hypothesis that the speed, accuracy, and acceptance of multimodal speech and direct-manipulation interfaces will increase when the modalities match the perceptual structure of the input attributes. A software prototype that supported a typical biomedical data collection task was developed to test this hypothesis. A group of 20 clinical and veterinary pathologists evaluated the prototype in an experimental setting using repeated measures. The results of this experiment supported the hypothesis that the perceptual structure of an input task is an important consideration when designing a multimodal computer interface. Task completion time, the number of speech errors, and user acceptance improved when interface best matched the perceptual structure of the input attributes.
Read-only transactions in a distributed database
Authors: Garcia-Molina Hector , Wiederhold Gio
Published: July 2002

A read-only transaction or query is a transaction which does not modify any data. Read-only transactions could be processed with general transaction processing algorithms, but in many cases it is more efficient to process read-only transactions with special algorithms which take advantage of the knowledge that the transaction only reads. This paper defines the various consistency and currency requirements that read-only transactions may have. The processing of the different classes of read-only transactions in a distributed database is discussed. The concept of
R
insularity is introduced to characterize both the read-only and update algorithms. Several simple update and read-only transaction processing algorithms are presented to illustrate how the query requirements and the update algorithms affect the read-only transaction processing algorithms.
An interative factorization techniques for polynomials
Authors: Luther H. A.
Published: July 2002

An iterative technique is displayed whereby factors of arbitrary degree can be found for polynomials in one variable. Convergence is shown to occur always if a certain Jacobian does not vanish and if the initial approximation to a factor is near enough to an actual factor. The process is simply programmed, and preliminary results indicate it to be well adapted to use with digital computers. For factors of degree two, the technique is similar to that of Bairstow, the present method being somewhat simpler.
The architecture of robust publishing systems
Authors: Waldman Marc , Rubin Aviel D. , Cranor Lorrie Faith
Published: July 2002

The Internet in its present form does not protect content from censorship. It is straightforward to trace any document back to a specific Web server, and usually directly to an individual. As we discuss below, there are valid reasons for publishing a document in a censorship-resistant manner. Unfortunately, few tools exist that facilitate this form of publishing. We describe the architecture of robust systems for publishing content on the Web. The discussion is in the context of Publius, as that system meets the most design goals of currently deployed systems. Publius has the property that it is very difficult for any adversary to censor or modify the content. In addition, the identity of the publisher is protected once the content is posted. The system differs from others in that tools are provided for updating or deleting published content, and users can browse the content in the normal point-and-click manner using a standard Web browser and a client-side proxy.
Transaction processing monitors
Authors: Bernstein Philip A.
Published: July 2002

A transaction processing (TP) application is a program that performs an administrative function by accessing a shared database on behalf of an on-line user. A TP system is an integrated set of products that supports TP applications. These products include both hardware, such as processors, memories, disks and communications controllers, and software such as operating systems (Oss), database management systems (DBMSs), computer networks and TP monitors. Much of the integration of these products is provided by TP monitors which coordinate the flow of transaction request between terminals that issue requests and TP applications that can process them.

Today, TP represents over 25 percent of the computer systems market and is one of the growing segments of the computer business. TP applications appear in most sectors of large-scale enterprises such as airline reservation, electronic banking, securities trading, inventory and production control, communications switching, videotex, sales management, military command and control and government services.
MYOBLAST CELL GRAFTING INTO HEART MUSCLE: Cellular Biology and Potential Applications
Authors: Kessler P. D. , Byrne B. J.
Published: July 2002

▪ Abstract  This review surveys a wide range of cellular and molecular approaches to strengthening the injured or weakened heart, focusing on strategies to replace dysfunctional, necrotic, or apoptotic cardiomyocytes with new cells of mesodermal origin. A variety of cell types, including myogenic cell lines, adult skeletal myoblasts, immortalized atrial cells, embryonic and adult cardiomyocytes, embryonic stem cells, teratoma cells, genetically altered fibroblasts, smooth muscle cells, and bone marrow–derived cells have all been proposed as useful cells in cardiac repair and may have the capacity to perform cardiac work. We focus on the implantation of mesodermally derived cells, the best developed of the options. We review the developmental and cell biology that have stimulated these studies, examine the limitations of current knowledge, and identify challenges for the future, which we believe are considerable.
Modeling the Emergence of Complexity: Complex Systems, the Origin of Life and Interactive On-Line Art
Authors: Sommerer Christa , Mignonneau Laurent
Published: July 2002

The origin of this paper lies in the fundamental question of how complexity arose in the course of evolution and how one might construct an artistic interactive system to model and simulate this emergence of complexity. Relying on the idea that interaction and communication between entities of a system drive the emergence of structures that are more complex than the mere parts of that system, the authors propose to apply principles of complex system theory to the creation of VERBARIUM, an interactive, computer-generated and audience-participatory artwork on the Internet, and to test whether complexity can emerge within this system.
Fast Calculation of Short-Term Depressing Synaptic Conductances
Authors: Giugliano Michele , Bove Marco , Grattarola Massimo
Published: July 2002

An efficient implementation of synaptic transmission models in realistic network simulations is an important theme of computational neuro-science. The amount of CPU time required to simulate synaptic interactions can increase as the square of the number of units of such networks, depending on the connectivity convergence. As a consequence, any realistic description of synaptic phenomena, incorporating biophysical details, is computationally highly demanding. We present a consolidating algorithm based on a biophysical extended model of ligand-gated postsynaptic channels, describing short-term plasticity such as synaptic depression. The considerable speedup of simulation times makes this algorithm suitable for investigating emergent collective effects of short-term depression in large-scale networks of model neurons.
Spatiotemporal Coding in the Cortex: Information Flow-Based Learning in Spiking Neural Networks
Authors: Deco Gustavo , Schürmann Bernd
Published: July 2002

We introduce a learning paradigm for networks of integrate-and-fire spiking neurons that is based on an information-theoretic criterion. This criterion can be viewed as a first principle that demonstrates the experimentally observed fact that cortical neurons display synchronous firing for some stimuli and not for others. The principle can be regarded as the postulation of a nonparametric reconstruction method as optimization criteria for learning the required functional connectivity that justifies and explains synchronous firing for binding of features as a mechanism for spatiotemporal coding. This can be expressed in an information-theoretic way by maximizing the discrimination ability between different sensory inputs in minimal time.
Facing the Music: Perspectives on Machine-Composed Music
Authors: Cope David
Published: July 2002

The author describes some of the processes required in creating Experiments in Musical Intelligence, a computer program for the simulation of musical styles. He then outlines many of the problems listeners face when attempting to deal with successful output from such programs. These problems involve redefining terms, debating humanversus computer-creativity and, ultimately, grappling with the meaning of music. This discussion includes an example from the computer-composed opera Mahler. The author argues that such music should be considered integral to mainstream humancomposed music since it results from a collaboration between humans and the machines they have created.
Telepresence: Understanding People as Content
Authors: Walker Graham , Bowskill Jerry , Hollier Mike , McGrath Andrew
Published: July 2002

BT is a leading international supplier of telepresence in the form of telephony. Tele-presence enables “people as content”, and there are rapidly developing and wide-ranging opportunities for broadband, mobile, multimedia telepresence services. This paper outlines work in progress at BT Adastral Park, including projects on large-scale inhabited applications, networked immersion or “through-the-screen” conferencing, and wearable computing for ubiquitous telepresence. We conclude that research into future services requires a reappraisal of traditional methods, with an emphasis on multidisciplinary collaboration.
ESTIMATING THE COMPLEXITY OF ANIMAL BEHAVIOUR: HOW MOUNTAIN GORILLAS EAT THISTLES
Authors: Byrne Richard , Corp Nadia , Byrne Jennifer
Published: July 2002

Mountain gorillas use elaborate, multi-stage procedures for dealing with plant defences. This paper investigates the use of mathematically-inspired, informational measures to gauge the complexity of one of these tasks, eating thistle Carduus nyassanus, from field observations of 38 adults and juveniles. Behaviour was analysed at two levels, a detailed, movementbased description of the form of actions, and an organizational description of techniques that were composed of a series of many actions. Complexity, as measured by counting the sizes of behavioural repertoires, correlated at the two levels. Repertoires were shown to be incomplete, but the rates of cumulative increase in actions differed between tasks. Thistle eating was the most complex, and apparently involved many more actions than even chimpanzee tool-use. Techniques were highly selective arrangements of actions, so that their organization (sequence, bimanual coordination, hierarchical structure) reflected cognitive capacity. Although ideally it would preferable to estimate complexity of task organization, this may seldom be feasible, and was not in this case. Instead, the length of a regularly occurring sequence of actions may be the best practical estimate of an underlying complexity of mental process. Confidence in this measure will be increased if it broadly agrees with other, independent estimates of task complexity; in the case of gorilla plant processing, both the size of repertoire of functionally distinct actions and the degree of lateral specialization were, like sequence length, greater for thistle processing than for other tasks studied to date.