bluuebunny/crossref_metadata_2025 huggingface dataset:
CHAIN BEHAVIOR IN MODEL HOMOGENEOUS ER FLUIDS DEPENDING ON TEMPERATURE
Authors: OKAMURA HIROKAZU , SUZUKI KAORI , MORI TAKESHI , MINAGAWA KEIJI , MASUDA SEIZO , TANAKA MASAMI
Published: August 2002

Water-soluble urethane-modified polyethers were prepared by addition of poly(ethylene oxide)-co-poly(propylene oxide) and aromatic isocyanate compounds. These polymers were found to dissolve in water at lower temperature and separate from solution upon heating. The temperature showing this unusual solubility change is called lower critical solution temperature (LCST). These chemical structures of thermo-responsive polymers were similar to those of urethane-modified ER active polymers containing poly(tetramethylene oxide) and aromatic urethane moiety. The thermo-responsive and ER polymers may have various intra- and intermolecular interactions through the urethane moiety. It is considered that both thermo-responsivility and ER effect are dependent on the conformational stability of the polymers under different conditions possibly related to these stimuli-responsivility through the molecular interactions. In order to clarify molecular motion of thermo-responsive polymers near the LCST, 1 H-NMR spin-lattice relaxation time ( T 1) was measured in D 2 O . The result indicated that hydrophobic interaction of terminal urethane moiety would strongly affect the LCST behavior.
BEHAVIOR OF MAGNETORHEOLOGICAL FLUIDS UTILIZING NANOPOWDER IRON
Authors: ROSENFELD NICHOLAS , WERELEY NORMAN M. , RADAKRISHNAN RADHAKUMAR , SUDARSHAN TIRULAI S.
Published: August 2002

Iron nanopowders for use in magnetorheological (MR) fluids were synthesized using a Microwave Plasma Synthesis technique developed at Materials Modification Inc (Fairfax VA). Transmission electron microscopy and surface area analysis measured iron particle size at 15–25 nm. The nanopowders were mixed into hydraulic oil to create nano-scale MR fluid. A micro-scale fluid was created using 45 μm iron particles as well as a hybrid fluid using a 50/50 mix of micro- and nanoparticles. All three fluids had a solids loading of 60% (w/w or weight by weight fraction). The fluids were tested in a flow mode rheometer fabricated from a modified damper using a sinusoidal input dynamometer over a speed range of 12.7 to 177.8 mm/s (0.5 to 6 in/s) and an input current range of 0 to 2 A. The yield stress and plastic viscosity of the MR fluid were characterized using a Bingham plastic model.
ELECTRO-MAGNETORHEOLOGICAL FLUIDS DISPERSING ZEOLITE PARTICLES CONTAINING IRON
Authors: SHIBAYAMA A. , MIYAZAKI T. , YAMAGUCHI K. , MURAKAMI K. , FUJITA T.
Published: August 2002

Some functional fluids that respond to both magnetic and electric fields have been prepared and their characteristics are described. In this study, an electro-magnetorheological fluid (EMRF) dispersing zeolite particles containing metallic iron by reducing precipitated magnetite has been investigated. When the viscosity is measured by cone plate viscometer and cylindrical viscometer, electric and magnetic fields are applied both between cone and plate or two cylinders. In case of cone plate, the shear stress at constant shear rate increased with the increase of both magnetic field and electric field. On the other hand when the viscosity is measured by cylindrical viscometer, the shear stress at constant shear rate increased with the increase of electric field, however, the increase rate of shear stress by magnetic field is very small. In this case the magnetic field direction is perpendicular to electric field. The EMRF has typical characteristics to respond with magnetic and electric field. The shear stress of EMRF in electric field is stronger than that of magnetic field. Additionally, the inflection and peak point in the shear rate-shear stress curve are appeared and the behaviors of the clusters in the electric field are observed. The experimental results suggested that the fluid viscosity (shear stress/shear rate) is affected by the arrangement of clusters parallel or perpendicular to the direction of the EMRF flow.
COMPRESSIVE MODULUS OF FERRITE CONTAINING POLYMER GELS
Authors: MITSUMATA TETSU , FURUKAWA KENTA , JULIAC ETIENNE , IWAKURA KENJI , KOYAMA KIYOHITO
Published: August 2002

The mechanical properties of magnetic gel have been investigated. Magnetic gels, which consist of finely dispersed powder of barium ferrite ( BaFe 12 O 19) and poly vinyl alcohol (PVA), have been synthesized. The diameter of barium ferrite is less than 45 μm. The magnetic gels varying with ferrite concentration, crosslinking densities were prepared by mixing 10 wt.% PVA aqueous solution and barium ferrite using glutaraldehyde as a crosslinking agent in the presence of HCl. The diameter of barium ferrite is large enough to have a permanent magnetic moment. We applied a 10 kOe magnetic field in order to saturate the magnetic moment of barium ferrite. After magnetization, the compressive modulus was estimated with an ultrasonic method in order to find the influence of magnetization. Ultrasonic measurements were carried out using burst waves at 10 MHz and 295.5 K. The modulus of magnetized gel was found to depend on the concentration of magnetic substance, the crosslinking density, and the degree of swelling. It was clear that the modulus of magnetized gel was higher than the gel without magnetization for all samples. The change in modulus to the initial modulus ΔM′/M′o for 10 wt.% and 15 wt.% of ferrite concentration was about 0.28% and 0.4% in a lower density region, respectively. Moreover, the change in modulus ΔM′/M′o was constant in a lower density region however it strongly depends on the density in a higher density region. When the stress direction is perpendicular to the magnetization, the change in modulus increased. On the contrary, the change in modulus decreased when the stress direction is parallel to the magnetization. As increasing the density, the distance between magnetic substances become short and therefore the magnetic interaction is more significant in a higher density region.
FIELD DEPENDENCE OF VISCOELASTIC PROPERTIES OF MR ELASTOMERS
Authors: BELLAN C. , BOSSIS G.
Published: August 2002

A magnetoactive elastomer made of micronic carbonyl iron particles, structured in elongated clusters and embedded in a silicon elastomer matrix is studied under traction both in static and dynamic modes. The application of a magnetic field of 120 kA/m induces a change in elastic moduli of about 0.6 MPa at strains of 4 to 5%. Still higher changes (4 MPa) are observed in dynamic storage modulus at low strains (10-4 to 10-3). The shape of the stress-strain curves are explained by taking into account the existence of a fiber like structure.
ELECTRIC-FIELD RESPONSE OF THE STRUCTURE AND RHEOLOGICAL PROPERTY OF SILICONE/POLYETHER BLENDS
Authors: MINAGAWA KEJI , SAITOH KOICHI , OKAMURA HIROKAZU , MORI TAKESHI , MASUDA SEIZO , TANAKA MASAMI
Published: August 2002

The ER effects were studied for various immiscible blends composed of urethane-modified polyethers and sillicones. Some polyethers and silicones were prepared from polypropylene glycol (PPG) and modified poly(dimethyl siloxane) having terminal hydroxyl groups, respectively. The influence of blend composition on the ER effects were examined for some binary and ternary blends based on these materials. The ER effects of these blends varied with the modification of polyethers and silicones, and also with the blend composition. In particular, the response of viscosity on applying or removing an electric field was found to vary with the blend composition, which should reflect some time-dependent change in the phase structure during the application and removal of the electric field. The variety of field response are discussed on the basis of the miscibility of the blend components.
SYNTHESIS AND ELECTRORHEOLOGY OF PHOSPHATE CELLULOSE SUSPENSIONS
Authors: KIM J. W. , CHO Y. H. , CHOI H. J. , JHON M. S.
Published: August 2002

As a candidate for the development in electrorheological (ER) materials, phosphate cellulose (PC) particles were synthesized from the phosphate–ester reaction between cellulose particles and ammonium phosphate solution prepared from six different molar concentrations of phosphoric acid. The synthesized particles were then dispersed in silicone oil to prepare the PC-based anhydrous ER fluid. The effects of electric field strength and particle concentration on the ER performance were investigated with both steady shear and dynamic oscillatory shear modes. The ER system with PC particles formed with a 2 M phosphoric acid solution exhibited the highest yield stress. A difference in the flow behavior of the PC-based ER fluids was also analyzed via the dielectric spectra using an impedance analyzer. We adapted the PC-based ER fluids to the semi-active ER damper and the examined their damping characteristics.
ELECTRORHEOLOGICAL BEHAVIOR OF CHITOSAN DICARBOXYLATE SUSPENSIONS
Authors: CHOI UNG-SU , KO YOUNG-GUN
Published: August 2002

The electrorheological (ER) behavior of chitosan dicarboxylate suspensions in silicone oil was investigated by varying the electric fields, volume fractions of particles, and shear rates, respectively. The chitosan dicarboxylate susepnsions showed a typical ER response caused by the polarizability of an amide polar group and shear yield stress due to the formation of multiple chains upon application of an electric field. Of these, chitosan malonicate suspension represented slightly higher rheological performance than any other suspensions due to dependent upon the carbon chain length. The shear stress for the suspension exhibited a linear dependence on an electric field power of 1.88. On the basis of the results, the newly synthesized chitosan dicarboxylate suspensions were found to be an anhydrous ER fluid.
THE CONTRIBUTION OF COLUMNAR STRUCTURE TO THE STRESS IN ER POLYMERIC BLENDS IN A SHEAR FLOW
Authors: RIHA P. , TAKIMOTO J. , MASUBUCHI Y. , KOYAMA K.
Published: August 2002

The bridging of electrodes by the columns of highly viscous polymer is dominant feature of the response of most electro-rheological liquid polymeric blends to the imposed electric field. To link the columnar structure and its deformation to the macroscopic shear stress, the transitory process of structure reorganization is described as a stochastic process determining rheological properties of the blend. The shear stress predictions are compared to the experimental data for steady and start up shear flows. The data support the assumption that only viscous deformation prevails in shear flow.
EFFECTS OF SHAPE AND SIZE OF DISPERSOID ON ELECTRORHEOLOGY
Authors: KAWAI AKIKO , UCHIDA KUNIO , IKAZAKI FUMIKAZU
Published: August 2002

The effects of shape and size of dispersoids on electrorheology were investigated. In order to study the effect of shape on electrorheology, three kinds of hydroxy-zinc complexes were used for dispersoids. Hydroxy-zinc complexes were Zn 5 (OH) 8 Cl 2 · H 2 O (1), Zn 5 (OH) 8( NO 3)2 · 2H 2 O (2), and Zn 5 (OH) 8( CH 3 COO )2 · 2H 2 O (3). Shapes of (1) and (2) are plate. The shape of (3) is rod. The ER fluid containing (3) showed the lowest permittivity and the lowest ER effect. The ER phenomena containing dispersoids with different shapes were independent of their shapes and were explained by their dielectric properties. Zinc oxides prepared by the heat treatment of (1), (2), and (3) were used for studying the effect of size on electrorheology. The particle size influenced their dielectric property and influenced their electrorheology. The dielectric properties were responsible for the ER effect.
ER EFFECT OF LIQUID CRYSTAL FLOWING BETWEEN TWO PARALLEL-PLATE ELECTRODES
Authors: TSUKIJI TETSUHIRO , TANABE SHINSUKE
Published: August 2002

Liquid crystal is one of homogeneous ER(Electro-rheological) fluids in some range of temperature. Transient responses of pressure drop are examined when liquid crystal flows between two parallel-plate electrodes for constant flow rates. When voltages are applied on the liquid crystal and removed, the pressure responses of the inlet of electrodes are measured with the pressure transducer. At the same time, liquid crystal between the transparent electrodes made of glass is visualized with the high-speed video camera to investigate the time history of the director of the liquid crystal. Outlet of the flow channel with two parallel-plate electrodes is atmosphere. Relation between the flow visualization results and the changes of pressure drop is investigated especially for transient period. In the present experiment the flow rates change from 0.001 cc/sec(velocity is 1 mm/sec) to 0.003 cc/sec and the electric field intensity is from 0.2 kV/mm to 1 kV/mm. The gap of the electrodes is 0.2 mm. The isotropic-nematic transition is 35.5°C and smectic-nematic transition is 23.1°C. The open-loop test facility with the liquid crystal is set in a pyrostat to keep the temperature constant.
EFFECT OF MAGNETIC HYSTERESIS OF THE SOLID PHASE ON THE RHEOLOGICAL PROPERTIES OF MR FLUIDS
Authors: DE VICENTE J. , DURÁN J. D. G. , DELGADO A. V. , GONZÁLEZ-CABALLERO F. , BOSSIS G.
Published: August 2002

An experimental investigation is described concerning the effect of the existence of a remanent magnetization of the dispersed particles on the rheological properties of magnetorheological fluids (MRF). Two MRF's were used: (1) solid phase: cobalt ferrite particles + silica gel (1.5% w/w); liquid phase: silicone oil (viscosity 20 mPa·s); and (2) solid phase: carbonyl iron + silica gel; liquid phase; silicone oil. The cobalt ferrite particles were synthetized as monodisperse colloidal spheres with an average diameter of 850 nm. The dependence of the dimensionless shear stress (τ⋆/ϕ) vs. Mason number (Mn) fails to scale when a "magnetorheological hysteresis procedure" is followed, specially for the higher volume fractions used (≈ 7.5%). The yield stress (τy) is first estimated from successive rheograms obtained decreasing the external field (H0) values for different ϕ. A more precise determination can be done by applying a stress ramp in the oscillatory regime. The critical stress amplitude (τc) needed to exceed the viscoelastic linear region (VLR) is obtained. It is found that both τy and τc strongly depend on the magnetic history of the sample. As expected, the previous results were not obtained in a classical MRF of carbonyl iron particles since they do not present magnetic hysteresis. We conclude that cobalt ferrite suspensions are an other kind of MRF which works at low fields (0 – 17.8 kA/m) with the opposite effect: decrease of the yield stress with the field. This property can be improved using particles with stronger remanent magnetization.
RHEOLOGICAL AND DIELECTRIC CHARACTERIZATION OF ELECTRORHEOLOGICAL FLUIDS COMPOSED OF BOTH DISPERSED PARTICLES AND LIQUID DROPS IN A DIELECTRIC MEDIUM
Authors: REJON L. , GARCIA L. , MANERO O.
Published: August 2002

The rheological and dielectric behavior of novel electrorheological suspensions composed of noncolloidal silica gel particles of irregular shape and oil-in-oil emulsions with different electrical conductivity (and permittivity) are studied in this work. The rheological behavior of the suspensions is examined in systems with various compositions of the oil phase under different intensities of constant DC electric fields. Results reveal that the electrorheological (ER) response of the oil-in-oil emulsion increases with the applied voltage but is affected negatively when the concentration of the oil with higher conductivity is increased. When a small volume fraction of silica gel is added, the ER response increases considerably and its magnitude is strongly dependent on the electric field. In this case, however, larger concentrations of the oil with the higher conductivity, in the presence of silica particles, increase the relative viscosity of the suspensions. The dielectric properties of the suspensions are examined to elucidate the relation between the dielectric relaxation process and the relative composition of liquid drop phases. The mechanisms responsible of the ER response are explained in terms of the relationship between the microstructure changes in the suspensions and their rheological and dielectric properties.
THE UNIFORM MAGNETIC FIELD INFLUENCE ON THE MAGNETIC FLUID MENISCUS MOTION IN THE CYLINDRICAL CAPILLARY
Authors: BASHTOVOI V. , KUZHIR P. , REKS A. , BOSSIS G. , VOLKOVA O.
Published: August 2002

An improvement of liophobic capillary-porous systems using magnetic fluids is proposed. The cycle of non-wetting liquid penetration and displacement is realized experimentally in the presence of the uniform magnetic field. Experimental investigations of the effect of the external uniform magnetic field on dynamics of capillary penetration of the Newtonian magnetic fluid into cylindrical capillaries at zero gravity and under gravity are presented. It is found that the pressure difference in the magnetic fluid between a meniscus and a free surface in a vessel increases in the field longitudinal to the capillary and decreases in the transverse one. In the longitudinal field, the velocity of penetration increases at zero gravity and does not vary under gravity. The transverse field slows down the process.
FLOW MODIFICATION INDUCED BY QUINCKE ROTATION IN A CAPILLARY
Authors: CEBERS A. , LEMAIRE E. , LOBRY L.
Published: August 2002

When particles immersed in a semi-insulating liquid are submitted to a sufficiently high DC field, they can rotate spontaneously around any axis perpendicular to the field (Quincke rotation). Recently we have shown that due to Quincke effect the effective viscosity of a colloidal suspension could be reduced. When the suspension is submitted to a shear, the particles rotation is amplified by the electric torque and drives the suspending liquid. For a flow in a capillary, this effect manifests itself by an increase of the flow rate. We present the results of our experiments carried out with a rectangular cross section capillary. These results are compared with the direct determination of the apparent viscosity in a Couette flow rheometer.
STRUCTURE-ENHANCED YIELD SHEAR STRESS IN ELECTRORHEOLOGICAL FLUIDS
Authors: Tao R. , Lan Y. C. , Xu X.
Published: August 2002

A new technology, compression-assisted aggregation, is developed to enhance the strength of electrorheological (ER) fluids. The yield shear stress of ER fluids depends on the fluid microstructure. The unassisted electric-field induced ER structure mainly consists of single chains, whose weak points are at their ends. This new technology produces a structure consisting of robust thick columns with strong ends. As the weak points of the original ER structure are greatly enforced, the new structure makes ER fluids super-strong: At a moderate electric field and moderate pressure the yield shear stress of ER fluids at 35% volume fraction exceeds 100 kPa, well above any requirement for major industrial applications.
CHARACTERISTICS OF A YIELD STRESS SCALING FUNCTION FOR ELECTRORHEOLOGICAL FLUIDS
Authors: CHOI H. J. , KIM J. W. , CHO M. S. , KIM C. A. , JHON M. S.
Published: August 2002

The electrorheological (ER) fluids exhibit a drastic change in rheological and electrical properties. Among these properties, yield stress is one of the critical evaluation parameters of the performance of ER devices. The published experimental data of yield dependence on the electric field strength and particle volume fraction are inconsistent due to the time dependence of material properties and measuring conditions. In this paper, we present a universal function, descriptive of the normalized yield stress, via scaling of the applied electric field strength. This scaling equation hybridizes both the polarization and conductivity models. Yield stress data for various ER fluids are collapsed onto a single curve for a broad range of electric field strengths, suggesting that the proposed scaling equation is adequate for predicting the ER property. Furthermore, the yield stresses, obtained from two different measuring techniques (static and dynamics methods), were also examined.
STRESS RELAXATION OF MAGNETORHEOLOGICAL FLUIDS
Authors: LI W. H. , CHEN G. , YEO S. H. , DU H.
Published: August 2002

In this paper, the experimental and modeling study and analysis of the stress relaxation characteristics of magnetorheological (MR) fluids under step shear are presented. The experiments are carried out using a rheometer with parallel-plate geometry. The applied strain varies from 0.01% to 100%, covering both the pre-yield and post-yield regimes. The effects of step strain, field strength, and temperature on the stress modulus are addressed. For small step strain ranges, the stress relaxation modulus G(t,γ) is independent of step strain, where MR fluids behave as linear viscoelastic solids. For large step strain ranges, the stress relaxation modulus decreases gradually with increasing step strain. Morever, the stress relaxation modulus G(t,γ) was found to obey time-strain factorability. That is, G(t,γ) can be represented as the product of a linear stress relaxation G(t) and a strain-dependent damping function h(γ). The linear stress relaxation modulus is represented as a three-parameter solid viscoelastic model, and the damping function h(γ) has a sigmoidal form with two parameters. The comparison between the experimental results and the model-predicted values indicates that this model can accurately describe the relaxation behavior of MR fluids under step strains.
ROLE AND NATURE OF HIGH FIELD CONDUCTION OF THE SUSPENDING LIQUID IN ELECTRORHEOLOGICAL FLUIDS
Authors: ATTEN P. , FOULC J.-N. , GONON P.
Published: August 2002

We examine the interaction force between spheres of a slightly conducting material immersed in a dielectric liquid when subjected to a DC field. An approach is developed which refines the previous two-zone model retaining only the electrical conduction of the solid and liquid phases and taking into account the field enhanced dissociation of electrolytic impurities. Approximations on the shape of the equipotential surfaces inside the solid lead to a system of ordinary differential equations governing the distribution of the electrical potential along the sphere surface. Estimates are derived for the attraction force between spheres in contact, for the current and for the electric stress in the liquid lying between the spheres in the "contact zone". This field takes values in the range 200–300 V/μm which correspond to extremely high levels of salts dissociation. The different conduction phenomena in the liquid are then discussed and their role in limiting the interaction force is emphasized.
MASS LOSSES OF MAGNETIZED RHEOLOGICAL MEDIUMS SUBJECTED TO MAGNETIC FIELD
Authors: BAEV A. R. , MATOUSSEVITCH N. P.
Published: August 2002

Theoretical analysis and experimental research of the film flowing of magnetorheologic fluids when infinitive solid plate is retrieving from the former mediums were carried out. We have got dependencies of fluids mass losses m vs: velocity of moving plate V; magnitude of magnetic intensity, its gradient and angle φ between direction of intensity lines and normal vector to plane of plate. It is shown that theoretical and experimental m(φ) is anisotropy one and may change its magnitude more than 10 times. Real behavior and extreme characteristics of m(φ) depends on rhelogiacal parameters of MRS and its magnetization. Obtained experimental data of dependence m(V) are in qualitative and quantitative agreement with the modernized theory.
SIMULATION OF BIDISPERSE MAGNETORHEOLOGICAL FLUIDS
Authors: KITTIPOOMWONG DAVID , KLINGENBERG DANIEL J. , ULICNY JOHN C.
Published: August 2002

A method for simulating the steady-shear behavior of bidisperse, nonlinearly magnetizable MR suspensions is described. Results show that the yield stress of suspensions containing mixtures of large and small particles is larger than that of monodisperse suspensions, in agreement with previous experimental results.
COMPARATIVE INVESTIGATIONS ON ER FLUIDS WITH DIFFERENT POLARIZATION MECHANISMS
Authors: BÖSE H. , TRENDLER A.
Published: August 2002

The rheological and electric properties of various ER fluids in strong electric fields have been investigated simultaneously. From the measured data the dependences of shear stress and real and imaginary part of the high field permittivity on field strength, temperature and frequency have been derived. One group of ER fluids containing perovskite type particles obeys a polarization mechanism which is attributed to the local displacement of ions in the crystal structure of the particles. The contribution of conduction to ER activity is low and the electric properties of these ER fluids are nearly constant. The increase of shear stress with frequency is in accordance with the polarization model. In contrast, another group of ER fluids containing zeolite or ion conducting polymer particles shows a strong dependence of the complex permittivity on field strength and temperature demonstrating the pronounced nonlinearity of the electric properties. It is assumed that both conduction and polarization contribute to the ER activity in these systems. The relative extent of the contributions changes with external conditions like field strength and temperature.
A SIMPLE FACTOR-2/3 APPROXIMATION ALGORITHM FOR TWO-CIRCLE POINT LABELING
Authors: WOLFF ALEXANDER , THON MICHAEL , XU YINFENG
Published: August 2002

Given a set P of n points in the plane, the two-circle point-labeling problem consists of placing 2n uniform, non-intersecting, maximum-size open circles such that each point touches exactly two circles.

It is known that this problem is NP-hard to approximate. In this paper we give a simple algorithm that improves the best previously known approximation factor from [Formula: see text] to 2/3. The main steps of our algorithm are as follows. We first compute the Voronoi diagram, then label each point optimally within its cell, compute the smallest label diameter over all points and finally shrink all labels to this size. We keep the O(n log n) time and O(n) space bounds of the previously best algorithm.
SEARCHING A ROOM BY TWO GUARDS
Authors: PARK SANG-MIN , LEE JAE-HA , CHWA KYUNG-YONG
Published: August 2002

We consider the problem of searching for mobile intruders in a polygonal region with one door by two guards. Given a simple polygon [Formula: see text] with a door d, which is called a room [Formula: see text], two guards start at d and walk along the boundary of [Formula: see text] to detect a mobile intruder with a laser beam between the two guards. During the walk, two guards are required to be mutually visible all the time and eventually meet at one point. We give a characterization of the class of rooms searchable by two guards and an O(n log n)-time algorithm to test if a given room admits a walk, where n is the number of the vertices in [Formula: see text].
RELIABLE SOLUTION IN STRAIN SPACE OF ELASTOPLASTIC PROBLEMS WITH ISOTROPIC HARDENING AND UNCERTAIN DATA
Authors: HLAVÁČEK IVAN
Published: August 2002

Quasi-static problems of the flow theory of elastoplasticity are formulated in strain space by means of a variational inequality. Continuous dependence of the resulting stress tensor on some input data (coefficients, initial condition and loading) is proved. Employing a worst scenario method for uncertain data, we prove the existence of "worst" admissible input data with regard to three given criteria.
NUMERICAL ANALYSIS OF MICRO–MACRO SIMULATIONS OF POLYMERIC FLUID FLOWS: A SIMPLE CASE
Authors: JOURDAIN BENJAMIN , LELIÈVRE TONY , LE BRIS CLAUDE
Published: August 2002

We present in this paper the numerical analysis of a simple micro–macro simulation of a polymeric fluid flow, namely the shear flow for the Hookean dumbbells model. Although restricted to this academic case (which is however used in practice as a test problem for new numerical strategies to be applied to more sophisticated cases), our study can be considered as a first step towards that of more complicated models. Our main result states the convergence of the fully discretized scheme (finite element in space, finite difference in time, plus Monte Carlo realizations) towards the coupled solution of a partial differential equation/stochastic differential equation system.
SOLUTION OF TWO EQUATIONS ARISING IN THE OVERLAPPING GENERATIONS MODEL
Authors: DEMICHELIS STEFANO
Published: August 2002

We solve two equations arising in the model of overlapping generations introduced by Samuelson, we use the result to prove uniqueness of equilibria in overlapping generations models up to time shift.
SINGULAR CONVERGENCE TO NONLINEAR DIFFUSION WAVES FOR SOLUTIONS TO THE CAUCHY PROBLEM FOR THE COMPRESSIBLE EULER EQUATIONS WITH DAMPING
Authors: DI FRANCESCO M. , MARCATI P.
Published: August 2002

We investigate the singular limit for the solutions to the compressible gas dynamics equations with damping term, after a parabolic scaling, in the one-dimensional isentropic case. In particular, we study the convergence in Sobolev norms towards diffusive prophiles, in case of well-prepared initial data and small perturbations of them. The results are obtained by means of symmetrization and energy estimates.
A FORMULA FOR THE CASSON KNOT INVARIANT OF A 2-BRIDGE KNOT
Authors: MIZUMA YOKO
Published: August 2002

The purpose of this note is to give a formula for the Casson knot invariant (the second coefficient of the Conway polynomial) of a 2-bridge knot, calculating without using a continued fraction expansion.
QUANDLE KNOT INVARIANTS ARE QUANTUM KNOT INVARIANTS
Authors: GRAÑA MATÍAS
Published: August 2002

We prove that the knot invariants given by quandles can be recovered by invariants given by traces on braided vector spaces, i.e. quantum invariants.
THE MYSTERY OF THE BRANE RELATION
Authors: GAROUFALIDIS STAVROS
Published: August 2002

Using the notion of surgery on objects called Y-graphs and claspers by Goussarov and Habiro, one can define a theory of finite type invariants of closed 3-manifolds. The paper discusses upper bounds for the number of invariants, and focuses on two surprises that arise: One surprise is that the upper bounds depend on a bit more than a choice of generators for H1. A complementary surprise a curious brane relation (in two flavors, open and closed) which shows that the upper bounds are in a certain sense independent of the choice of generators of H1.
A TRANSFER MATRIX APPROACH TO THE ENUMERATION OF KNOTS
Authors: JACOBSEN J. L. , ZINN-JUSTIN P.
Published: August 2002

We propose a new method to enumerate alternating knots using a transfer matrix approach. We apply it to count numerically various objects, including prime alternating tangles with two connected components, up to order 18–22, and comment on the large-order behavior in connection with one of the authors's conjecture.
ABOUT THE UNIQUENESS OF THE KONTSEVICH INTEGRAL
Authors: LESCOP CHRISTINE
Published: August 2002

We refine a Le and Murakami uniqueness theorem for the Kontsevich Integral in order to specify the relationship between the two (possibly equal) main universal Vassiliev link invariants: the Kontsevich Integral and the perturbative expression of the Chern-Simons theory. As a corollary, we prove that the Altschuler and Freidel anomaly [Formula: see text]-that groups the Bott and Taubes anomalous terms- is a combination of diagrams with two univalent vertices and we explicitly define the isomorphism of [Formula: see text] which transforms the Kontsevich integral into the Poirier limit of the perturbative expression of the Chern-Simons theory for framed links, as a function of α
A MATRIX INVARIANT OF CURVES IN S2
Authors: ZULLI LOUIS
Published: August 2002

Let k: S1 → S2 be a generic immersion with n double points. We present an algorithm that assigns to k a partitioned n × n matrix over Z/2Z, and show that k gives rise to an orthogonal decomposition of (Z/2Z)n. We discuss a connection between this decomposition and the trip matrix of an alternating knot diagram produced from k.
ON NON-SIMPLE REFLEXIVE LINKS
Authors: MATSUDA HIROSHI , OZAWA MAKOTO , SHIMOKAWA KOYA
Published: August 2002

We consider Dehn surgeries on some non-simple 2-component links in S3 which yield S3. As corollary we give a class of 2-component links which are determined by their complements.
PLANAR LACES
Authors: JIN GYO TAEK , KIM HUN
Published: August 2002

Let S be a connected open subset of 2-sphere S2 which is identified with the extended plane R2 ∪ {∞}. We assume that S contains the n segments {1, 2, …, n} × [-1, 1]. An n-lace ℓ (in S) is the union ℓ1 ∪ … ∪ ℓn of disjoint simple arcs in S such that ∂ ℓi = {(i, 1), (π (i),-1)}, i = 1, …, n, for some permutation π of {1, 2, …, n}.

In this paper we will do present mapping class group description of n-laces, and 1-lace in 1-punctured plane, and 2-laces in S2. We will also describe the isotropy subgroup of the trivial lace in [Formula: see text].
ON DOUBLE-TORUS KNOTS (I)
Authors: HILL PETER
Published: August 2002

A double-torus knot is knot embedded in a genus two Heegaard surface [Formula: see text] in S3. After giving a notation for these knots, we consider double-torus knots L such that [Formula: see text] is not connected, and give a criterion for such knots to be non-trivial. Various new types of non-trivial knots with trivial Alexander polynomial are found.
ON OHTSUKI'S INVARIANTS OF HOMOLOGY 3-SPHERES
Authors: LAWRENCE RUTH J.
Published: August 2002

By analysing Ohtsuki's original work in which he produced a formal power series invariant of rational homology 3-spheres, we obtain a simplified explicit formula for them, which may also be compared with Rozansky's integral expression. We further show their relation to the exact SO(3) Witten-Reshetikhin-Turaev invariants at roots of unity in a stronger form than that given in Ohtsuki's original work.
Portfolio Effect on Daily Stock Return Across Industrial Sectors in Hong Kong: An Analysis of Dow Effect
Authors: Tang Gordon Y. N.
Published: August 2002

This paper examines the portfolio effect on the daily stock returns across industrial sectors in the Hong Kong market. For the overall daily stock returns, our results show that with an increase in the portfolio size, the standard-deviation and kurtosis decrease while the skewness becomes more negative. The result is a more negatively skewed but less leptokurtic stock return distribution on average. However, the impact of diversification on stock returns differs across weekdays. On Monday, the reduction in standard deviation is the smallest across all weekdays. Simple portfolio diversification cannot eliminate skewness and kurtosis only on Monday but not on other weekdays. Our results suggest that a new anomaly exists in the Hong Kong stock market on Monday.
Financial Management Issues in International Life Insurance Operations
Authors: Forbes Stephen W.
Published: August 2002

The dismantling of foreign trade barriers, 24-hour worldwide capital markets, regulatory reforms within countries recognizing the importance of private financial markets, technologies such as the Internet, and the access of large segments of urban populations throughout the world to television and computers mark significant changes in financial services. As part of these structural changes, many governmental, economic, and competitive trends are affecting life insurance markets throughout the world in similar ways. This paper discusses these trends and the factors required for effective international life insurance operations.
Financial Reforms and Financial Crisis: The Korean Case
Authors: Oh Junggun , Park Donghyun
Published: August 2002

We assess the role of financial reforms and liberalization in Korea's financial crisis, which erupted in late 1997. We first examine financial reforms carried out since the early 1980s and their effects on corporate financing as well as on the current account. We then analyze policy issues associated with the current financial crisis. Our main conclusion is that the crisis is due in no small measure to the unbalanced nature of Korea's financial reforms — extensive external liberalization combined with inadequate internal liberalization. The massive inflow of foreign capital associated with external liberalization exacerbated the over-investment problem that already existed in the 1970s. The inefficiencies of Korea's manufacturing corporations and financial institutions mutually reinforced each other, producing a vicious cycle of ever lower productivity of capital. The key to Korea's recovery thus lies in successful restructuring of both its financial and corporate sectors.
India and Pakistan Go Nuclear: The Economic Costs for India, Pakistan — and China
Authors: Sweeney Richard J. , Zhang Jianhua
Published: August 2002

Quantitative estimates show that India's nuclear tests caused important economic damage to India and its neighbors, Pakistan and China. Pakistan's tests caused further economic damage to all three countries. In response to India's tests, India's stock market fell by 7.26 percent, Pakistan's by 10.59 percent and China's by 2.70 percent. In response to Pakistan's tests, India's stock market fell by another 5.57 percent, Pakistan's by 16.82 percent and China's by 3.93 percent. Overall, the two countries' tests caused India's stock market to fall by 12.83 percent, Pakistan's by 27.41 percent and China's by 6.63 percent. Some argue that going nuclear increased India and Pakistan's national security and their international political standing. In the financial markets' opinion, these tests caused major reductions in both countries' economic security, and harmed China's economic security. The tests had no important effects on the Group of Ten countries' stock markets; thus, the tests' economic effects seem for the moment of be confined to southern Asia.
Short-Term Seasonalities on the Jakarta Stock Exchange
Authors: Wong Kie Ann , Yuanto Kusnadi
Published: August 2002

This research attempts to uncover the presence of various stock market seasonalities on the Jakarta Stock Exchange (JSX). We find that most of the seasonal effects exist on the JSX, except for the January effect. There is a day-of-the-week effect with low Tuesday and high Friday returns. The "twist" effect is confirmed with a negative Tuesday return following a market decline in the previous week. The Tuesday "Rogalski" effect is present, with Tuesday return being positive in the month of January and negative for the other months. The monthly, turn-of-the-month, turn-of-the-year and pre-holiday effects are also confirmed in recent sub-periods after the reforms of the JSX in 1988.
Best Efforts vs. Firm Commitment Initial Public Offerings: Evidence on the Market Feedback Theory
Authors: Sherman Ann E.
Published: August 2002

This paper documents the differences between best efforts and firm commitment U.S. IPOs and looks for evidence of the Sherman (1992) market feedback theory. A probit model of the contract choice is estimated. Best efforts offerings are shown to be, on average, smaller offerings from smaller, younger companies, many of them start-ups. They have higher average initial returns and a higher variance of initial returns, and they are less likely to include shares sold by insiders. The data is consistent with the implications of the market feedback theory.
Financial Policy Responses to the Asian Financial Turmoil and Future Financial Reform of Taiwan, ROC
Authors: Chiu Paul C. H.
Published: August 2002

This paper discusses financial policy as it relates to the Asian financial crisis. The paper is divided into three parts. First, I discuss some of the concrete measures taken by the ROC government in the face of the financial crisis. Second, I would like to outline our continuing efforts at financial reform. Finally, I conclude with some comments on what we may expect in the days to come, along with some general conclusions.
What Makes Hot Money Hot? The Relative Volatility of International Flows of Debt and Equity Capital
Authors: Brennan Michael J. , Aranda Carmen
Published: August 2002

This paper is concerned with the relative volatility of international flows of debt and equity capital. It is shown that if foreign investors are less well informed about the domestic economy than domestic investors, then international flows of debt capital will be more volatile than flows of equity capital in the sense that the proportional change of foreign bondholdings in an economy in response to a change in that economy's economic prospects will be greater than the proportional change in foreign stockholdings. This is shown to be consistent with the behavior of international flows of debt and equity capital during the Asian crisis.
NASH EQUILIBRIA FROM THE CORRELATED EQUILIBRIA VIEWPOINT
Authors: CANOVAS SABRINA GOMEZ , HANSEN PIERRE , JAUMARD BRIGITTE
Published: August 2002

We consider Nash equilibria as correlated equilibria and apply polyhedral theory to study extreme Nash equilibrium properties. We obtain an alternate proof that extreme Nash equilibria are extreme correlated equilibria and give some characteristics of them. Furthermore, we study a class of games that have no completely mixed Nash equilibria.
THE STABILITY OF DYNAMIC RENT-SEEKING GAMES
Authors: XU LIN , SZIDAROVSZKY FERENC
Published: August 2002

The asymptotical stability of the equilibrium in dynamic rent-seeking games is examined. Both discrete and continuous time scales are considered. Sufficient, necessary and sufficient stability conditions are derived and then economic interpretations are discussed. Special cases of linear production functions are used to illustrate the conditions.
A STRATEGIC CONCESSION GAME
Authors: JØRGENSEN STEFFEN , YEUNG DAVID W. K.
Published: August 2002

This paper considers a two-player negotiation problem with complete information and non-transferable payoffs/utilities. There are gains to be made by both players if they make bilateral concessions in their actions, relative to the status quo Nash equilibrium (NE) outcome. The failure to agree on a jointly acceptable arrangement has been a major stumbling block to the exploitation of such gains. The paper develops a concession game which has a cooperative trait in the sense that bilateral concessions in actions are sought by both players, but the game proceeds in a non-cooperative fashion in determining the levels of concessions, given a prior agreement over the rules of the game among the players. The game is applicable to a large class of bargaining situations in which both players would benefit from mutual reductions in their decision variables. Two specific applications, a tariff negotiation game and a cartel output agreement are examined.
Chronology Versus Biology
Authors: Aviv Abraham
Published: September 2002

There is considerable evidence that essential hypertension is closely linked to the growth, development, and aging of human beings. It is imperative, therefore, to introduce biological indicators of growth and aging into models developed to provide a better understanding of the etiology of essential hypertension. One of these indicators may well be the age-dependent telomere attrition rate in somatic cells. Telomere attrition registers the replicative history of somatic cells. As such, it chronicles not only the growth that results from the replication of somatic cells but also their turnover—a process that is strongly linked to inflammation and oxidative stress, which are key factors in the biology of human aging.
Angiotensin II Induces Catecholamine Release by Direct Ganglionic Excitation
Authors: Dendorfer Andreas , Thornagel Alexandra , Raasch Walter , Grisk Olaf , Tempel Klaus , Dominiak Peter
Published: September 2002

Angiotensin II (ANG) is known to facilitate catecholamine release from peripheral sympathetic neurons by enhancing depolarization-dependent exocytosis. In addition, a direct excitation by ANG of peripheral sympathetic nerve activity has recently been described. This study determined the significance of the latter mechanism for angiotensin-induced catecholamine release in the pithed rat. Rats were anesthetized and instrumented for measuring either hemodynamics and renal sympathetic nerve activity or plasma catecholamine concentrations in response to successively increasing doses of angiotensin infusions. Even during ganglionic blockade by hexamethonium (20 mg/kg), angiotensin dose-dependently elevated sympathetic nerve activity, whereas blood pressure–equivalent doses of phenylephrine were ineffective. Independently of central nervous sympathetic activity and ganglionic transmission, angiotensin (0.1 to 1 μg/kg) also induced an up-to 27-fold increase in plasma norepinephrine levels, reaching 2.65 ng/mL. Preganglionic electrical stimulation (0.5 Hz) raised basal norepinephrine levels 11-fold and further enhanced the angiotensin-induced increase in norepinephrine (4.04 ng/mL at 1 μg/kg ANG). Stimulation of sympathetic nerve activity and norepinephrine release were suppressed by candesartan (1 mg/kg) or tetrodotoxin (100 μg/kg), respectively. Angiotensin enhanced plasma norepinephrine, heart rate, and sympathetic nerve activity at similar threshold doses (0.3 to 1 μg/kg), but raised blood pressure at a significantly lower dose (0.01 μg/kg). It is concluded that direct stimulation of ganglionic angiotensin type 1 (AT
1
) receptors arouses electrical activity in sympathetic neurons, leading to exocytotic junctional catecholamine release. In both the absence and presence of preganglionic sympathetic activity, this mechanism contributes significantly to ANG-induced enhancement of catecholamine release.
Sibling Resemblance for Left Ventricular Structure, Contractility, and Diastolic Filling
Authors: Tang Weihong , Arnett Donna K. , Devereux Richard B. , Province Michael A. , Atwood Larry D. , Oberman Albert , Hopkins Paul N. , Kitzman Dalane W.
Published: September 2002

Although there is evidence that left ventricular (LV) function is genetically controlled, the contribution of familial factors to variation and covariation of LV diastolic filling, contractility, and structure is unknown. Single- and cross-trait sibling correlations were estimated using bivariate familial correlation models in 200 white (400 pairs) and 374 black (539 pairs) hypertensive sibships. LV transmitral early and late peak filling velocities, isovolumic relaxation time, atrial filling fraction, stress-corrected midwall shortening, and LV mass and structure were measured and adjusted for important covariates in race-specific linear regression models. Single-trait sibling correlation was strongest for early peak filling velocity. Significant cross-trait sibling correlation was detected between early and late peak filling velocities. In whites, early peak filling velocity and atrial filling fraction, and isovolumic relaxation time and end-diastolic posterior wall thickness, were also significantly correlated. Familial factors common to early and late peak filling velocities contributed to 64% and 54% of sibling resemblance in early peak filling velocity and to 76% and 77% in late peak filling velocity in blacks and whites, respectively. In whites, 100% of sibling resemblance in isovolumic relaxation time was shared by posterior wall thickness, whereas 75% of sibling influence in posterior wall thickness was common to isovolumic relaxation time. In conclusion, significant cross-trait sibling resemblance was detected between (1) early and late filling parameters and (2) isovolumic relaxation time and posterior wall thickness, suggesting pleiotropy and/or common environment on these traits. These data have potential importance in understanding heritability of LV diastolic function in hypertension.