bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of nitrogen and boron fertilization on foliar boron nutrition and growth in two different lodgepole pine ecosystems
Authors: Brockley R P
Published: May 2003

The 9-year effects of nitrogen (N) and boron (B) fertilization on the growth and foliar B nutrition of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were evaluated in two different ecosystems in the interior of British Columbia. When added alone, B had no effect on basal area or height increment. However, combined applications of N and B were superior to N alone in stimulating height development at both study sites. At one site, fertilization with N, alone and in combination with sulphur (S), resulted in a significant amount of top dieback symptomatic of severe B deficiency. No visible deficiency symptoms were observed when B was combined with N or N + S. Boron fertilization significantly increased foliar B concentrations at both study sites, and higher foliar B levels were maintained throughout the 9-year study period. Results suggest that significant visible symptoms of B deficiency in lodgepole pine are unlikely to occur at foliar levels >6 mg/kg, although subacute B deficiency may suppress height development in the absence of deficiency symptoms. When combined with nitrogenous fertilizers, B applications of 1.53.0 kg/ha are likely sufficient to achieve, and maintain, favourable B status and healthy growth of trees over a prolonged period.
Effects of competition control and annual nitrogen fertilization on gas exchange of different-aged Pinus taeda
Authors: Munger Gregory T , Will Rodney E , Borders Bruce E
Published: May 2003

To determine the importance of competition control and annual fertilization on leaf gas exchange, light-saturated net photosynthesis (Asat), stomatal conductance (gs), and internal CO2 concentration (Ci) were measured multiple times in different-aged loblolly pine (Pinus taeda L.) stands growing at a Piedmont (BF Grant) and Coastal Plain (Waycross) location in Georgia, U.S.A. At both locations, competition control decreased Asat and gs (Asat from 4.53 to 4.12 µmol·m2·s1, gs from 0.058 to 0.050 mol·m2·s1 at BF Grant; Asat from 4.22 to 4.01 µmol·m2·s1, gs from 0.054 to 0.049 mol·m2·s1 at Waycross). Overall, fertilization did not have a positive impact on Asat, even though fertilization significantly increased foliar nitrogen concentration. At BF Grant, fertilization significantly decreased gs from 0.057 to 0.051 mol·m2·s1 and Ci from 217 to 205 µmol·mol1. In addition, the decrease in Ci associated with fertilization became larger with stand age. At Waycross, fertilization decreased Ci from 211 to 203 µmol·mol1 and the interaction between fertilization and stand age was significant for gs and Ci. These results indicate that silivcultural practices that increase resource availability and stand growth did not enhance leaf gas exchange.
Regional impacts of periodical cicadas on oak radial increment
Authors: Koenig Walter D , Liebhold Andrew M
Published: May 2003

We investigated the effects of periodical cicadas (Magicicada spp.) on growth of their hosts using records of radial tree-ring growth on oaks (Quercus spp., a common host genus) and pines (Pinus spp., a common nonhost genus) growing within the ranges of 13- and 17-year broods. Growth of oaks was significantly depressed during years of adult emergence by about 4%. Effects in years following emergences or in years prior to emergences were variable or absent. Spectral analyses revealed a significant tendency for periodicity in the growth of oaks, but not pines, matching that of the life cycle of the broods. These results provide some of the first evidence for landscape-level effects of a root-feeding insect and demonstrate that periodical cicadas have a small but detectable effect on growth of their hosts on a geographical scale, considerably larger than previously suspected.
Tabu search design for difficult forest management optimization problems
Authors: Richards Evelyn W , Gunn Eldon A
Published: May 2003

A series of tabu search (TS) methods for solving the stand harvesting and road access optimization problem was developed and evaluated. This challenging forest management problem includes spatial constraints for maximum opening size, adjacency delay (green up), as well as timber-flow targets derived exogenously from a strategic planning process. The base harvest decision unit is the stand, and harvest blocks are created dynamically as adjacent stands are scheduled for treatments. The road network subproblem is solved using a fast heuristic method to select a minimum discounted cost set of road construction projects so that scheduled stands are accessible. The TS methods range from simple ones with fixed tabu tenure to an adaptive search with feedback mechanisms to control tabu tenure and to direct the search near constraint boundaries. It was found that while simple TS algorithms can find feasible solutions to the problem, these may be far from optimal. A good short-term memory strategy, constraint boundaries smoothed using penalty functions, and customized diversification moves were important design elements in the most successful TS algorithm for this problem. This paper points out the necessity to design the TS method carefully, since there are many possible TS designs and the design choices matter.
Forest-fire-scar aging using SPOT-VEGETATION for Canadian ecoregions
Authors: Amiro Brian D , Chen Jing M
Published: May 2003

The mapping of Canadian fires is a large effort supported by provincial, territorial, and federal agencies. Remote sensing techniques can aid in mapping, especially in remote areas and during busy fire seasons. The SPOT-VEGETATION (SPOT-VGT) sensor has previously shown promise at distinguishing fire scars on the landscape. The usefulness of SPOT-VGT to age fires in 18 Canadian ecoregions was evaluated for a period up to 50 years since fire, analysing more than 250 000 pixels (nominal resolution about 1 km2). The SPOT-VGT reflectances were evaluated using the ratio of the short-wave infrared band (1.581.75 µm) to near-infrared band (0.780.89 µm), compared with the Canadian large-fire database (fires greater than 200 ha in size). Nonlinear regressions were significant for all ecoregions with r2 values being greater than 0.57 for 16 of them. Five ecoregions groupings had similar relationships, consistent with their contiguous pattern on the landscape. The prediction of fire-scar age depends on ecoregion and can be successful over periods as short as 6 years to as long as 30 years. The root mean square error for all ecoregions ranged from 5 years for recent burns to about 12 years for three decades following fire. This tool is useful to get approximate fire-scar ages, but the accuracy is limited because of the variation in forest succession on the landscape, and it cannot replace more detailed mapping done currently by fire agencies.
The Holocene vegetation history of Isle Royale National Park, Michigan, U.S.A.
Authors: Flakne Robyn
Published: May 2003

A vegetation history for Isle Royale National Park, Michigan, U.S.A., is reconstructed using pollen and spores extracted from two lake sediment cores. Lily Lake is on the southwestern end of the main island of Isle Royale surrounded by northern hardwoods forest. Lake Ojibway is on the northeastern end of the main island surrounded by boreal forest. Pollen and spore records were analyzed using pollen percentage diagrams, nonmetric multidimensional scaling ordination, and modern analog analysis. Squared chord distances for temporally paired subsamples from each site were calculated to determine palynological dissimilarities between the sites through time. These analyses revealed an overall vegetation history that is consistent with other regional reconstructions. High percentages of spruce pollen, indicating a cool climate, are present in the early Holocene, whereas high percentages of pine pollen, indicating a dry climate, occur in the mid-Holocene. The pollen records from the two sites diverge with increased precipitation during the late Holocene. At this time, birch-dominated forest is established near Lily Lake on till-derived soils. At Lake Ojibway, a mixed birch, pine, spruce, and fir forest is established on bedrock-derived soils. The divergence in forest composition is most pronounced within the last 500 years, and this divergence is tentatively attributed to the response of taxa on different substrates to increasing precipitation. Other possible explanations for the recent divergence include changing microclimates or disturbance regimes.
Effects of NaCl on shoot growth, transpiration, ion compartmentation, and transport in regenerated plants of Populus euphratica and Populus tomentosa
Authors: Chen Shaoliang , Li Jinke , Wang Shasheng , Fritz Eberhard , Hüttermann Aloys , Altman Arie
Published: May 2003

The effect of a 20-day NaCl treatment on shoot growth, transpiration, ion uptake and transport, and intracellular ion compartmentation was investigated in regenerated plants of Populus euphratica Oliv. and Populus tomentosa Carr. Plants watered with 100 mM NaCl for 8 days and then 200 mM NaCl for 12 days exhibited soil NaCl concentrations of 60 and 95 mM, respectively. Unit transpiration rates and relative growth rates of P. tomentosa were restricted more by salinity as compared with P. euphratica. Salinized P. tomentosa exhibited leaf necrosis whereas no damage was seen in stressed P. euphratica. Compared with P. tomentosa, P. euphratica had considerably lower rates of net root uptake and transport of salt ions (Na+ and Cl) to the shoots under salinity. The relatively lower unit transpiration rates of P. euphratica and the lower salt concentrations in the xylem of salinized P. euphratica contribute to its greater capacity for salt exclusion. X-ray microanalysis showed that P. euphratica had a greater ability to restrict radial salt transport in roots by blocking apoplasmic salt transport and sequestering more Cl in cortical vacuoles. In addition, P. euphratica maintained higher K+ uptake and transport than P. tomentosa in the presence of high external Na+ concentrations.
Morphometric, allometric, and developmentally adaptive traits in red spruce and black spruce. II. Seedling and mature tree assessment of controlled intra- and inter-specific hybrids
Authors: Major John E , Mosseler Alex , Barsi Debby C , Campbell Moira , Rajora Om P
Published: May 2003

The objective of this study was to investigate the genetic nature of morphometric, allometric, and developmental traits in controlled intra- and inter-specific hybrid crosses of red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) BSP). We examined 1-year-old greenhouse-grown seedlings and 22-year-old mature trees that were part of the same set of controlled crosses performed in the early 1970s. Seed weight had a strong female species effect. Mean cotyledon number and germination time had a very strong hybrid index effect. F1 interspecific hybrids showed negative heterosis in mature tree height, whereas hybrid index 25, a black spruce backcross, produced positive heterosis for seedling and mature tree height growth. Correlations of mean height of seedlings with mean height of mature trees on two sites were remarkably high (r = 0.918 and r = 0.968) when tested by hybrid index. Any cross having black spruce as the female or male parent had significantly higher height growth than those with red spruce as either female or male parent. Of the five hybrid indices, hybrid index 0 (black spruce) had the highest biomass allocation to stem wood and hybrid index 100 (red spruce) had the highest allocation to roots.
ELASTIC AND DRIFT–DIFFUSION LIMITS OF ELECTRON–PHONON INTERACTION IN SEMICONDUCTORS
Authors: SCHMEISER CHRISTIAN , ZWIRCHMAYR ALEXANDER
Published: May 2003

This paper deals with electron transport in semiconductors when electron–phonon interaction is considered. Smallness of the mean free path compared to a characteristic length scale and of the phonon energy compared to the thermal energy of the crystal are assumed. The corresponding limits in the transport problem are carried out and shown not to commute. An intermediate limit leads to a new macroscopic model.
ON THE PERTURBATION METHODS FOR SOME NONLINEAR QUANTUM CHEMISTRY MODELS
Authors: CANCÈS ERIC , BRIS CLAUDE LE
Published: May 2003

The purpose of this article is to (a) give a sound mathematical foundation to perturbation methods for some nonlinear quantum chemistry models. This contributes to the understanding of computations on molecular systems in situ, such as solvated molecules or molecules subjected to a uniform external electric field and (b) prove in the latter setting a result of non-existence of solutions to the Thomas–Fermi–Von Weizsäcker and to the Hartree–Fock equations, which is the nonlinear counterpart of a result by Avron and Herbst.2
ON THE EXPONENTIAL STABILITY OF ADVECTION SEMIGROUPS WITH BOUNDARY OPERATORS
Authors: AMMAR-KHODJA FARID , MOKHTAR-KHARROUBI MUSTAPHA
Published: May 2003

This paper deals with estimates of the type of advection semigroups with contraction boundary operator when the velocity space is bounded away from zero. Two approaches are given. The first one, using energy method, relies on Datko–Pazy's theorem while the second approach is based upon the analysis of the resolvent operator and the identity of the spectral bound (of generators) and the type of positive semigroups on Lp(μ) spaces by Weis.
FREEZING PROCESSES IN SATURATED SOILS
Authors: TALAMUCCI F.
Published: May 2003

When a soil saturated with water is subject to freezing, a volume expansion can generally be observed. The increase in volume is due not only to the different densities of water and ice, but mainly to a water migration process that is transported from the base of the soil up to an intermediate region where the change of phase occurs. It is generally accepted that a transition region, called frozen fringe, where ice and water coexist in the porous space, separates the unfrozen from the frozen part of the soil. Immediately over the frozen fringe a pure segregated layer of ice (ice lens) can form. If the freezing process is too fast or the weight acting on the soil (overburden pressure) is relevant, the porous matrix does not separate and the shifting of the frozen fringe towards the base of the soil (frost penetration) is observed. Many mathematical models have been proposed for the frost heave process. The main features of the one-dimensional model we are considering are summarized in Sec. 1. In Ref. 9 the case of assignment of the boundary thermal fluxes (at the base and on top of the soil) is studied. In practical cases, sometime the boundary temperatures, instead of the thermal fluxes, can be registered or imposed: in this paper we will investigate the model in such case. The main purpose is to detect which are the boundary values for temperature that determine the process of lens formation or frost penetration, once the properties of the soil are known.
METHOD OF ASYMPTOTIC PARTIAL DECOMPOSITION OF DOMAIN
Authors: PANASENKO G. P.
Published: May 2003

A new method of partial decomposition of a domain is proposed for partial differential equations, depending on a small parameter. It is based on the information about the structure of the asymptotic solution in different parts of the domain. The principal idea of the method is to extract the subdomain of singular behavior of the solution and to simplify the problem in the subdomain of regular behavior of the solution. The special interface conditions are imposed on the common boundary of these partially decomposed subdomains. If, for example, the domain depends on the small parameter and some parts of the domain change their dimension after the passage to the limit, then the proposed method reduces the initial problem to the system of equations posed in the domains of different dimensions with the special interface conditions.
VORTICITY–VELOCITY FORMULATION OF THE STOKES PROBLEM WITH VARIABLE DENSITY AND VISCOSITY
Authors: ERN ALEXANDRE
Published: May 2003

We investigate the vorticity–velocity formulation of the stationary, two-dimensional Stokes problem in the case of variable density and viscosity. The analysis is presented in the low Mach number regime, where the density is independent of spatial variations of the pressure. We introduce a variational framework and prove the equivalence of the vorticity–velocity and velocity–pressure formulations in appropriate functional spaces. We then derive a weak formulation for the Stokes equations in vorticity–velocity form. Finally, when the spatial variations of the density and of the viscosity are small enough, we prove the existence and uniqueness of the solution to the Stokes problem in both vorticity–velocity and velocity–pressure forms.
GLOBAL EXISTENCE AND LONG-TIME BEHAVIOR FOR A PARTIALLY DISSIPATIVE SYSTEM MODELLING A POLYMERIZATION–CRYSTALLIZATION REACTION
Authors: NJAMKEPO SERGE
Published: May 2003

We consider a partially dissipative system in a bounded interval of ℝ and we prove the existence of a local exponential attractor. The key tool is the adaptation of a method due to Babin and Nicolaenko, for a dissipative system in an unbounded domain.
ASYMPTOTIC STABILITY OF EQUILIBRIUM STATES FOR MULTICOMPONENT REACTIVE FLOWS
Authors: GIOVANGIGLI VINCENT , MASSOT MARC
Published: May 2003

We consider the equations governing multicomponent reactive flows derived from the kinetic theory of dilute polyatomic reactive gas mixtures. Using an entropy function, we derive a symmetric conservative form of the system. In the framework of Kawashima and Shizuta's theory, we recast the resulting system into a normal form, that is, in the form of a symmetric hyperbolic–parabolic composite system. We also characterize all normal forms for symmetric systems of conservation laws such that the null space associated with dissipation matrices is invariant. We then investigate an abstract second-order quasilinear system with a source term, around a constant equilibrium state. Assuming the existence of a generalized entropy function, the invariance of the null space naturally associated with dissipation matrices, stability conditions for the source term, and a dissipative structure for the linearized equations, we establish global existence and asymptotic stability around the constant equilibrium state in all space dimensions and we obtain decay estimates. These results are then applied to multicomponent reactive flows using a normal form and the properties of Maxwellian chemical source terms.
THE hp FINITE ELEMENT METHOD FOR SINGULARLY PERTURBED PROBLEMS IN SMOOTH DOMAINS
Authors: XENOPHONTOS CHRISTOS A.
Published: May 2003

We consider the numerical approximation of singularly perturbed elliptic problems in smooth domains. The solution to such problems can be decomposed into a smooth part and a boundary layer part. We present guidelines for the effective resolution of boundary layers in the context of the hp finite element method and we construct tensor product spaces that approximate these layers uniformly at a near-exponential rate.
A STOCHASTIC MODEL FOR THE COOPERATIVE RELAXATION OF PROTEINS, BASED ON A HIERARCHY OF INTERACTIONS BETWEEN AMINO ACIDIC RESIDUES
Authors: ABUNDO M. , ACCARDI L. , STELLA L. , ROSATO N.
Published: May 2003

In this paper, a stochastic model for the cooperative relaxation of proteins, based on a hierarchic structure of the interactions between amino acids is proposed. It relies on the arbitrary splitting of interactions into two classes, strong and weak, and tests the preponderance of one class over the other. The presented model generalizes a first one valid for homogeneous interactions in the protein molecules previously studied by the authors. The time evolution of the system is studied as a function of five parameters, three of which are related to the cooperativity. Moreover, different approximations of the discrete system to a diffusion process, and to a Poisson process are considered, according to the magnitude of the parameters. A method for estimating the parameters from real data is proposed. Finally, numerical simulations and a comparison with the molecular dynamics of a real protein (Barnase) are reported.
ON THE TWO-POINT CORRELATION FUNCTION FOR DISPERSIONS OF NONOVERLAPPING SPHERES
Authors: MARKOV KONSTANTIN Z. , WILLIS JOHN R.
Published: May 2003

Random dispersions of spheres are useful and appropriate models for a wide class of particulate random materials. They can be described in two equivalent and alternative ways — either by the multipoint moments of the characteristic function of the region, occupied by the spheres, or by the probability densities of the spheres' centers. On the "two-point" level, a simple and convenient integral formula is derived which interconnects the radial distribution function of the spheres with the two-point correlation of the said characteristic function. As one of the possible applications of the formula, the behavior of the correlation function near the origin is studied in more detail and related to the behavior of the radial distribution function at the "touching" separation of the spheres.
AN OPTIMAL LOW-ORDER LOCKING-FREE FINITE ELEMENT METHOD FOR REISSNER–MINDLIN PLATES
Authors: CHAPELLE D. , STENBERG R.
Published: May 2003

We propose a simple modification of a recently introduced locking-free finite element method for the Reissner–Mindlin plate model. By this modification, we are able to obtain optimal convergence rates on numerical benchmarks. These results are substantiated by a complete mathematical analysis which provides optimal a priori error estimates.
GENESIS OF A SOURCE/SINK LINE INTO A SINGULAR UPDRAFT
Authors: CHASKALOVIC JOËL
Published: May 2003

Mathematical models applied to tornadoes describe these kinds of flows as an axisymmetric fluid motion which is restricted for not developing a source or a sink near the vortex line. Here, we propose the genesis of a family of a source/sink line into a singular updraft which can modeled one of the step of the genesis of a tornado. This model consists of a three-parameter family of fluid motions, satisfying the steady and incompressible Navier–Stokes equations, which vanish at the ground. We establish the local existence and uniqueness for these fields, at the neighborhood of a nonrotating singular updraft.
EXISTENCE RESULTS FOR THE STATIC CONTACT PROBLEM WITH COULOMB FRICTION
Authors: ECK C. , JARUSEK J.
Published: May 2003

We prove the existence of solutions to the static contact problem with Coulomb friction, provided that the coefficient of friction is small enough. The proof employs the penalty method and a certain smoothing procedure for the friction functional. Using optimal trace estimates for the solutions of the Lamé equations, we calculate an upper bound for the admissible coefficient of friction which is greater than the corresponding bounds proposed by Necas, Jarusek and Haslinger (1980) and by Jarusek (1983).
ASYMPTOTIC ESTIMATES FOR THE MULTI-DIMENSIONAL ELECTRO-DIFFUSION EQUATIONS
Authors: ALABAU F. , MOUSSAOUI M.
Published: May 2003

The drift-diffusion equations can be studied in the framework of singular perturbation analysis as a small parameter characterizing the device goes to zero. A formal asymptotic expansion, which includes internal (and eventually boundary) layer terms can be derived by standard techniques of asymptotic analysis. We present in this paper L2 estimates for the difference between the solutions of the full system and the first term of the expansion which are valid for multi-dimensional devices close to equilibrium. These estimates are based on a uniform monotone property of the equations with respect to the small parameter and on a L∞ bound for the gradient of solutions of equations under divergence form whose coefficients are bounded, and have derivatives in one direction which are bounded with respect to all variables.
A DEGENERATE PARABOLIC VARIATIONAL INEQUALITY FOR THE AMERICAN OPTION PRICING PROBLEM
Authors: MASTROENI LORETTA , MATZEU MICHELE
Published: May 2003

A formulation in terms of degenerate parabolic variational inequalities for the price of an American put option is stated. The usual uniform ellipticity condition is weakened by the presence of a weight function. Then the appropriate framework is that of some suitable "weighted" Sobolev spaces. One applies a result previously stated by the authors in Ref. 8.
A FINSLER GEOMETRIC MODEL OF EVOLUTION BY SYMBIOSIS
Authors: ANTONELLI P. L.
Published: May 2003

Finsler geometry in two dimensions is introduced to solve the problem of modelling two freely living populations (e.g. bacterial) which affect the stable physiology of a colonial organism. The populations are assumed to be logistic, but chemical producing. Concepts of Medawar's growth energy, Margulis' evolution by symbiosis, Harper's modular organisms and Wilson's ergonomics are formulated in terms of Volterra–Hamilton systems of Finsler type. It is proved that there can be no Riemannian models.
PATTERNS OF ALCOHOLISM: A MATHEMATICAL MODEL
Authors: AN DER HEIDEN U. , SCHWEGLER H. , TRETTER F.
Published: May 2003

In a first phenomenological part various forms of alcoholism and their classification are summarized. Our aim is to give an explanation of these patterns of alcohol consumption and addiction. Social, psychic, behavioral, and biochemico-physiological mechanisms currently discussed in the literature are briefly considered with respect to their potential for generating the dynamics of alcohol addiction. As central core those mechanisms turn out to be self-enhancing. By formulating these mechanisms in terms of mathematical models a tool is provided to study their consequences in isolation and in qualitative and quantitative detail.

The mathematical modeling is put forward in several steps starting with a single (differential) equation for the process of self-enhancement. This process, acting alone, leads to exponential and unbounded increase of the average alcohol consumption. In a second step, inhibitory mechansims are added which result e.g. from negative effects of alcohol drinking. The combination and different relative weights of self-enhancement and inhibition can already explain several types of drinking behavior, in particular those of α, β, γ and δ drinkers according to the classification of Jellinek. Possible transitions from one type to another and also to abstinence become imaginable by discussion of bifurcations on a 'cusp catastrophe".

Oscillatory phenomena in drinking behavior, e.g. the "episodic drinker", result if and only if, in a further step, the model is complemented by a second differential equation accounting for the dynamics of an internal state symbolically called "frustration level". More generally this variable may represent any factor which interacts in a circular fashion (feedback loop) with the alcohol consumption.

In connection with the presented models, various ways and strategies for the transition from one type of drinking behavior to another (including low level drinking or abstinence) are discussed.
ON A FLUID-STRUCTURE INTERACTION PROBLEM IN VELOCITY-DISPLACEMENT FORMULATION
Authors: FLORI F. , ORENGA P.
Published: May 2003

We present in this paper an existence result of weak solutions as well as some regularity results for a fluid-structure interaction problem when a fluid velocity-structure displacement formulation is used. This formulation induces a difficulty connected with the coupling condition. Indeed, unlike the pressure-displacement formulation, we do not have a Neumann condition and consequently it is more difficult to obtain weak solutions.
NUMERICAL SIMULATIONS OF MEAN CURVATURE FLOW IN THE PRESENCE OF A NONCONVEX ANISOTROPY
Authors: FIERRO FRANCESCA , GOGLIONE ROBERTA , PAOLINI MAURIZIO
Published: May 2003

In this paper we present and discuss the results of some numerical simulations in order to investigate the mean curvature flow problem in the presence of a nonconvex anisotropy. Mathematically, nonconvexity of the anisotropy leads to the ill-posedness of the evolution problem, which becomes forward–backward parabolic. Simulations presented here refer to two different settings: curvature driven vertical motion of graphs (nonparametric setting) and motion in the normal direction by anisotropic mean curvature of surfaces (parametric setting). In the latter we first relax the problem via an Allen–Cahn type reaction-diffusion equation, in the context of Finsler geometry (diffused interface approximation). Our results suggest three main points. A nonconvex anisotropy and its convexification give rise, for both settings and the discretizations considered, to different evolutions. Wrinkled regions seem to appear only in correspondence to locally concave parts of the anisotropy. Moreover, locally convex regions (interior to the convexification of the so-called Frank diagram) seem to play an important role.
SOME EXISTENCE AND UNIQUENESS RESULTS FOR A TIME-DEPENDENT COUPLED PROBLEM OF THE NAVIER–STOKES KIND
Authors: CLIMENT BLANCA , FERNANDEZ-CARA ENRIQUE
Published: May 2003

In this paper, we consider some systems which are close to the instationary Navier–Stokes equations. The structure of these systems is the following: An (N + 1)-dimensional equation for motion (including the incompressibility condition) and a scalar equation involving an additional unknown, k = k(x,t). Among other things, they serve to model the behavior of certain turbulent flows. We are mainly concerned with existence and uniqueness results. The main difficulties are due to the scalar equation. In particular, the right-hand side is typically in L1; furthermore, there are nonlinear terms of the kind ∇·(μ(k)∇ k) and ∇·(B(k)), where μ and B are general continuous functions (no growth condition at infinity is imposed). Following the previous work of other authors, it is crucial to introduce the notion of weak-renormalized solution. Our results give the existence in the two-dimensional case, as well as the uniqueness of regular solution in both the two- and three-dimensional cases.
LOW CONCENTRATION LIMIT FOR A FLUID FLOW THROUGH A FILTER
Authors: MARUŠIĆ SANJA
Published: May 2003

A fluid flow through an ∊-periodic array of obstacles distributed on a hypersurface (filter) is considered. The study of the asymptotic behavior as ∊→0 for two critical sizes of obstacles ∊ and ∊2 gives two different laws describing a global flow. In this paper we study the case of an intermediate obstacle size ∊β, 1 < β < 2 and we prove the continuity of the filtration law in the low-volume fraction limit.
ON COUPLED PROBLEMS FOR VISCOUS FLOW IN EXTERIOR DOMAINS
Authors: FEISTAUER M. , SCHWAB C.
Published: May 2003

The use of the complete Navier–Stokes system in an unbounded domain is not always convenient in computations and, therefore, the Navier–Stokes problem is often truncated to a bounded domain. In this paper we simulate the interaction between the flow in this domain and the exterior flow with the aid of a coupled problem. We propose in particular a linear approximation of the exterior flow (here the Stokes flow or potential flow) coupled with the interior Navier–Stokes problem via suitable transmission conditions on the artificial interface between the interior and exterior domains. Our choice of the transmission conditions ensures the existence of a solution of the coupled problem, also for large data.
DISCRETE CONSERVATION AND DISCRETE MAXIMUM PRINCIPLE FOR ELLIPTIC PDEs
Authors: BERTOLAZZI ENRICO
Published: May 2003

A class of finite volume numerical schemes for the solution of self-adjoint elliptic equations is described. The main feature of the schemes is that numerical solutions share both discrete conservation and discrete strong maximum principle without restriction on the differential operator or on the volume elements.
AN INTEGRAL EQUATION OF CELL POPULATION DYNAMICS FORMULATED AS AN ABSTRACT DELAY EQUATION — SOME CONSEQUENCES
Authors: ARINO OVIDE , SÁNCHEZ EVA
Published: May 2003

From a nonlinear integral equation modelling cell proliferation, two other formulations are first proposed. One of them leads to a delay differential equation with values in a Banach space to which the theory of abstract delay differential equations is applied. Specific features of the equation are shown to entail interesting formulae for the dual product and the fundamental solution. Finally, preliminary steps are made in the study of what seems to be a Hopf bifurcation.
STATIONARY SOLUTIONS FOR SECOND GRADE FLUIDS EQUATIONS
Authors: BRESCH DIDIER , LEMOINE JÉRÔME
Published: May 2003

We discuss the existence and uniqueness for stationary second grade fluids. We give results in Lr(Ω)3 where r > 3, for an open set Ω which is only of class [Formula: see text]. This relies on a fixed point method.
A PENALTY METHOD FOR SOLVING PARTIAL DIFFERENTIAL EQUATIONS WITH PERIODIC BOUNDARY CONDITION: APPLICATION TO THE HOMOGENIZATION THEORY
Authors: AOUBIZA BOUJEMAA , LAYDI MOHAMED RACHID
Published: May 2003

We present a numerical method, based on a penalization technique, for the solution of an elliptic problem with periodic boundary conditions. The convergence of the method is established and an error estimate is given. Numerical tests are performed on some problems from homogenization theory.
COMPLETENESS OF ROOT FUNCTIONS FOR ELASTICITY PROBLEMS IN A STRIP
Authors: TITEUX I. , YAKUBOV Y.
Published: May 2003

In order to improve the expansion of stresses close to the edge for a thin plate, a corrective term is added to the displacement. This corrective displacement must solve a problem posed over an infinite domain. In order to get the behavior of this term far from the edge, we write it as a combination of root functions of the problem. To do this, we have to prove that a system of root functions is complete. It follows from this study that the corrective term decreases exponentially.
MIXED hp-FEM ON ANISOTROPIC MESHES
Authors: SCHÖTZAU DOMINIK , SCHWAB CHRISTOPH
Published: May 2003

Mixed hp-FEM for incompressible fluid flow on anisotropic meshes are analyzed. A discrete inf–sup condition is proved with a constant independent of the meshwidth and the aspect ratio. For each polynomial degree k≥2 we present velocity-pressure subspace pairs which are stable on quadrilateral mesh-patches independently of the element aspect ratio, implying in particular divergence stability on the so-called Shishkin-meshes. Moreover, the inf–sup constant is shown to depend on the spectral order k like k-1/2 for quadrilateral meshes and like k-3 for meshes containing triangles. New consistency results for spectral elements on anisotropic meshes are also proved.
ASYMPTOTICS FOR CRITICAL FIELDS IN AN APPROXIMATE GINZBURG–LANDAU MODEL IN THE LARGE SIZE LIMIT
Authors: BOLLEY CATHERINE , HELFFER BERNARD
Published: May 2003

Pursuing a study of the superheating field for the Ginburg–Landau equations performed in Ref. 8, we consider an approximate model for a film on a bounded interval when the thickness 2e is large in comparison with the inverse of the characteristic κ of the material. We show for this problem the existence of a local superheating field, and recover, as e tends to +∞, the superheating field for a similar approximate model on a semi-infinite interval which has been studied in Ref. 8.
ASYMPTOTIC ANALYSIS FOR A PARTICLE TRANSPORT EQUATION WITH INELASTIC SCATTERING IN EXTENDED KINETIC THEORY
Authors: BANASIAK JACEK , FROSALI GIOVANNI , SPIGA GIAMPIERO
Published: May 2003

In this paper we perform the asymptotic analysis for a linear transport equation for test particles in an absorbing and inelastically scattering background, when the excited species can be considered as non-participating. This model is derived in the frame of extended kinetic theory and rescaled with the Knudsen number ∊. After examining the main properties of the collision model and of the scattering operator in the case with an infinite interval of energy as well as the case with a finite interval, the modified (compressed) Chapman–Enskog expansion procedure is applied to find the asymptotic equation for small mean free path. A specific feature of this model is that the collision operator has an infinite-dimensional null-space. The main result is that in the small mean free path approximation on [Formula: see text] level we obtain a free molecular flow for a suitable hydrodynamic quantity, rather than the diffusion which is typical for linear transport problems.
EXPONENTIALLY DECAYING COMPONENT OF A GLOBAL SOLUTION TO A REACTION–DIFFUSION SYSTEM
Authors: HOSHINO HIROKI , KAWASHIMA SHUICHI
Published: May 2003

A reaction–diffusion system which is related to a simple irreversible chemical reaction between two chemical substances is considered. When a non-negative global solution for the system converges uniformly to zero with polynomial rate as time goes to infinity, large-time approximation of the solution is studied. It is shown that the difference of the solution and its spatial average tends to zero with exponential rate via a global solution for the corresponding system of ordinary differential equations.
MIGRATION IN AGE STRUCTURED POPULATION DYNAMICS
Authors: ARINO O. , SMITH W. V.
Published: May 2003

We introduce a linear model for age structured populations which migrate between several locations or patches. Birth is allowed in each patch. Existence, uniqueness and positivity of solutions is proved. A certain North Atlantic fishery is given as an example. Asymptotic solutions are characterized in a general system with periodic coefficients by spectral theory techniques and the results are applied to the example.
EXACT BOUNDARY CONTROLLABILITY OF A NONLINEAR SHALLOW SPHERICAL SHELL
Authors: BRADLEY MARY E. , LASIECKA IRENA
Published: May 2003

We consider the problem of boundary exact controllability of a coupled nonlinear system which describes vibrations of a thin, shallow, spherical shell. We show that under the geometric condition of "shallowness", which restricts the curvature with respect to the thickness, the system is exactly controllable in the natural "finite energy" space by means of L2 controls. This controllability is produced via moments and shear forces applied to the edge of the shell.
ON THE SPATIALLY HOMOGENEOUS LANDAU EQUATION FOR MAXWELLIAN MOLECULES
Authors: VILLANI C.
Published: May 2003

We establish a simplified form for the Landau equation with Maxwellian-type molecules. We study in details the Cauchy problem associated to this equation, and some qualitative features of the solution. Explicit solutions are given.
ROTATIONAL TRANSFORMATION METHOD AND SOME NUMERICAL TECHNIQUES FOR COMPUTING MICROSTRUCTURES
Authors: LI ZHIPING
Published: May 2003

A rotational transformation method and an incremental crystallization method are developed to overcome some of the difficulties involved in the computation of microstructures. The numerical method based on these techniques has proved to be convergent. To increase further the accuracy of the computation, a technique is applied to remove the boundary effect of the numerical solutions. Numerical results for a double well problem are given to show the efficiency of the techniques.
A QUASI-STATIC TWO-DIMENSIONAL INDUCTION HEATING PROBLEM I: MODELLING AND ANALYSIS
Authors: PARIETTI C. , RAPPAZ J.
Published: May 2003

We consider a nonlinear elliptic–parabolic system modelling induction heating processes when a sinusoidal electromagnetic field is applied at the boundary of the inductor. The magnetic field satisfies an elliptic equation whereas the temperature equation is parabolic. These equations are coupled together due to the conductivities and the Joule effect. We show the existence of a weak solution to the corresponding problem and under additional assumptions, we study the uniqueness of the solution.
NUMERICAL SOLUTION OF THE KURAMOTO–SAKAGUCHI EQUATION GOVERNING POPULATIONS OF COUPLED OSCILLATORS
Authors: SARTORETTO FLAVIO , SPIGLER RENATO , VICENTE CONRADO J. PÉREZ
Published: May 2003

A spectral method is developed to solve the Kuramoto–Sakaguchi nonlinear integro-differential equation numerically. This describes the dynamical behavior of populations of infinitely many nonlinearly coupled oscillators, and models a large number of phenomena in Biology, Medicine, and Physics. Some relevant bifurcation properties of solutions are investigated, and the numerical results are compared with those obtained from both the linearized equation and Monte–Carlo-type simulations of finitely many Langevin equations. In the numerical experiments, several frequency distributions, and several values of the bifurcation parameters are considered.
INSTABILITY OF OVERCOMPRESSIVE SHOCK WAVES FOR ROTATIONALLY INVARIANT SYSTEMS OF VISCOUS CONSERVATION LAWS
Authors: KUEH KA-LAM
Published: May 2003

Motivated by the study of M.H.D., we consider rotationally invariant system of viscous conservtion laws. We prove that overcompressive travelling waves solutions to the system are unstable by fixing a perturbation to the travelling waves and making the viscosity small.
STABILITY AND CONVERGENCE OF TWO-LEVEL DIFFERENCE SCHEMES IN INTEGRAL WITH RESPECT TO TIME NORMS
Authors: SAMARSKII ALEXANDER A. , MATUS PETR P. , VABISHCHEVICH PETR N.
Published: May 2003

Nowadays the general theory of operator-difference schemes with operators acting in Hilbert spaces has been created for investigating the stability of the difference schemes that approximate linear problems of mathematical physics. In most cases a priori estimates which are uniform with respect to the t norms are usually considered. In the investigation of accuracy for evolutionary problems, special attention should be given to estimation of the difference solution in grid analogs of integral with respect to the time norms. In this paper a priori estimates in such norms have been obtained for two-level operator-difference schemes. Use of that estimates is illustrated by convergence investigation for schemes with weights for parabolic equation with the solution belonging to [Formula: see text].
FINITE ELEMENT APPROXIMATION OF NONLOCAL HEAT RADIATION PROBLEMS
Authors: TIIHONEN T.
Published: May 2003

This paper focuses on finite element error analysis for problems involving both conductive and radiative heat transfers. The radiative heat exchange is modeled with a nonlinear and nonlocal term that also makes the problem non-monotone. The continuous problem has a maximum principle which suggests the use of inverse monotone discretizations. We also estimate the error due to the approximation of the boundary by showing continuous dependence on the geometric data for the continuous problem. The final result of this paper is a rigorous justification and error analysis for methods that use the so-called view factors for numerical modeling of the heat radiation.
A NONOVERLAPPING DOMAIN DECOMPOSITION METHOD FOR THE OSEEN EQUATIONS
Authors: OTTO F.-C. , LUBE G.
Published: May 2003

We describe a nonoverlapping domain decomposition algorithm which can be applied to scalar advection–diffusion reaction problems and the Oseen equations.

A convergence result is proved for the continuous algorithm in case of the Oseen equations and stated for the other case. We give some suggestions for the design of the interface conditions used within the algorithm and present some numerical examples.
MATHEMATICAL CONTROL THEORY IN STRUCTURAL ACOUSTIC PROBLEMS
Authors: LASIECKA IRENA
Published: May 2003

We consider control problems formulated within the context of structural acoustic models. The goal is to reduce the level of a noise or unwanted pressure in the interior of an acoustic chamber. This is accomplished by applying passive and active boundary and point controls in a feedback form. Mathematical (PDE) aspects of the underlying control problems are presented.
DISTURBANCE STRESS FOR STABILIZED SECOND ORDER CONTROL SYSTEMS
Authors: LEE E. B. , LUO J. C.
Published: May 2003

It is shown that the nastiest bounded disturbance stress for the stable second order oscillator is bang–bang with switching set by the state. A quadratic index and a time-distance index are used to evaluate the severity of the stressing. A procedure is suggested to construct a switching curve which synthesizes the disturbance stress in feedback form. Examples illustrating the results and the possible extension to third and higher order systems are given.
DISPERSION MODELING AND SIMULATION IN SUBSURFACE CONTAMINANT TRANSPORT
Authors: BUTERA JEFFREY V. , FITZPATRICK BEN G. , WYPASEK CHRISTIAN J.
Published: May 2003

In this paper, we examine three separate approaches to analyze the spatial dispersion of a subsurface contaminant. These methods are contrasted against traditional models to demonstrate their feasibility and usefulness. Lastly, numerical simulations illustrate the effectiveness of these approaches.
A REVIEW ON THE INFLUENCE OF BOUNDARY REGULARITY ON THE QUESTION OF BOUNDARY STABILIZATION
Authors: HORN MARY ANN
Published: May 2003

Sharp regularity results for the traces of solutions to elastic systems have proven to be invaluable in the study of controllability and stabilization. Such results have reduced the severity of the geometric assumptions required on the domain of definition. While early work imposed strong geometric constraints such as requiring the domain to be convex, such requirements are now known to be overly strict. Furthermore, these assumptions were often assumed to hold even in the case when control is permitted to act on the entire boundary. However, it is only a mathematical technicality that forces this restriction which is overcome via sharp trace regularity. A review on these issues is presented for the wave equation, the Kirchhoff plate equation and the system of three-dimensional elasticity.
NONUNIFORM GRIDS FOR REDUCED BASIS DESIGN OF LOW ORDER FEEDBACK CONTROLLERS FOR NONLINEAR CONTINUOUS SYSTEMS
Authors: KING BELINDA B.
Published: May 2003

In this paper, we discuss the use of nonuniform grids in reduced basis design for developing low order nonlinear feedback controllers for hybrid distributed parameter systems. The reduced basis approach was presented in an earlier paper by Burns and King; therein, all approximations were based upon uniform grids. In this paper, we explore the effect on control design of using nonuniform grids in the fundamental step of approximating the functional controller gains. We illustrate the process using a weakly nonlinear distributed parameter system.
APPROXIMATE BOUNDARY FORMABILITY WITH VOLUME ACTUATION
Authors: RUSSELL DAVID L.
Published: May 2003

We study the approximate formability of the boundary of a two-dimensional isotropic elastic medium with the use of uniform volume actuation in the interior of that medium. We show that care is required in the selection of formability criteria to ensure that formability corresponds with common sense notions of "shape control". Finally, we analyze what we define as approximate normal boundary formability in the case of a rectangular and a triangular region, showing that such formability does not obtain in the first instance but, with some smoothness assumptions, does obtain in the second.
MINIMUM AVERAGE COST PRODUCTION PLANNING IN STOCHASTIC MANUFACTURING SYSTEMS
Authors: SETHI SURESH P. , ZHANG HANQIN , ZHANG QING
Published: May 2003

Recently, the production control problem in stochastic manufacturing systems has generated a great deal of interest. The goal is to obtain production rates to minimize total expected surplus and production cost. This paper reviews the research devoted to minimum average cost production planning problems in stochastic manufacturing systems. Manufacturing systems involve a single or parallel failure-prone machines producing a number of different products, random production capacity, and constant demands.
THE POINTWISE COMPUTABILITY OF THE LORENZ SYSTEM
Authors: ESTEP DON , JOHNSON CLAES
Published: May 2003

We give evidence that most trajectories of the Lorenz system of ordinary differential equations are pointwise computable on time intervals of moderate length using an adaptive finite element method. Based on accurate computation, we present a description of the structure of the solutions of the Lorenz system as a repeated process of cutting-expanding-flipping-interlacing. We also give some general remarks on issues of computability and the relation between discrete and continuous dynamical systems.