bluuebunny/crossref_metadata_2025 huggingface dataset:
Considering Equipment and Transmission Availability Levels
Authors: Held Gilbert
Published: July 2007

In considering methods to reduce the probability of equipment and transmission facility outages, the reader may want to examine the effect of different equipment configurations upon the ability of network users to access data if one or more devices should fail. Thus, what you need is a mechanism to denote the effect of different equipment configurations upon the ability to access network resources. That mechanism is known as availability and is the general topic to be covered in this article.
A Corporate Anti‐Virus Strategy
Authors: Herold Rebecca
Published: July 2007

The Principal Finance Group's anti‐virus strategy was implemented at the beginning of 1994. To date, this strategy has been effective in quickly identifying viruses that have entered the company's computers, and removing them in an efficient and timely manner.
Is It Security or Disaster Recovery? Who Cares?
Authors: Ross Steven J.
Published: July 2007

In dealing with information systems, it does not matter whether efforts are expended toward securing information assets against misuse or protecting them against destruction.
Emitter design for high‐efficiency silicon solar cells. Part I: Terrestrial cells
Authors: Zhao Jianhua , Wang Aihua , Green M. A.
Published: July 2007

Emitter diffusions for conventional high‐efficiency silicon solar cells have commonly been designed to be very shallow to improve the short‐wavelength response of the cells. This first part of a two‐part paper has a substantial tutorial content and analyses the effect of the emitter design on cell performance with different cell surface passivation conditions. the analysis shows that shallow emitters are only necessary for cells with poor surface passivation. In contrast, high‐efficiency cells with good surface passivation do not necessarily need shallow emitters. the application of these design insights into recent generations of high‐efficiency passivated emitter solar cells is also discussed.
Solar cell efficiency tables (version 2)
Authors: Green Martin A. , Emery Keith
Published: July 2007

Upadated tables showing the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and the eight new entries since January 1993 are briefly described.
A novel type of solar cell holder for performance measurement
Authors: Larue J. C.
Published: July 2007

A conventional cell holder comprises a temperature‐controlled plate, the cell being held by vacuum suction. Pairs of probes are put in contact with the front grid. Different plates are required for various cell sizes. Holding thin and/or bent cells is critical. Probes may cause damage.

The proposed holder has a simple vacuum groove and is divided into two conductive areas. the cell is covered with a transparent plastic foil and a vacuum is applied to the groove. the plastic foil presses the cell and the interconnector on their respective areas, providing uniform pressure, realistic electrical configuration and reduced risk of breakage. One holder plate is sufficient for all cell sizes.

As the measurement is made by comparison to a ‘primary standard cell’, the foil's optical effect is taken into account by using it also on top of the standard.
Short communication: Effects of heat treatments and CdCl2, pretreatments on the stoichiometries of solution‐grown CdS thin films
Authors: Niles David W. , Hasoon Falah S.
Published: July 2007

Solution grorwth of CdS on SnO2‐coated glass with subsequent heat treatments is known to produce stoichiometric CdS thin films with characteristic thicknesses of about 1000 Å. We show that heating solution‐grown CdS thin films in a nitrogen atmosphere to ⩾ 450° C results in sulphur loss. Heating to 550°C leads to a 50% loss of sulphur, leaving the entire 1000‐A CdS thin film with a concentration of about 75 at.% Cd and 25 at.% S. However, dipping the CdS thin films in a CdCl2 solution prior to heating coats the CdS, leaving a CdCl2 layer that acts as a protective coating and prohibits the loss of sulphur. Cadmium sulphide thin films dipped in a CdCl2 solution and then heated to 550°C are stoichiometric.
Optimization of the rear contact pattern of high‐efficiency silicon solar cells with and without local back surface field
Authors: Sterk S. , Knobloch J. , Wettling W.
Published: July 2007

The influence of the point spacing and size on the cell efficiency is studied for different silicon solar cell structures with local rear contacts: the PERC (passivated emitter and rear cell) with its high recombination at the rear contacts and the LBSF (local back surface field) or PERL (passivated emitter and rear locally diffused) cell with reduced combination at the rear contacts due to a diffused high‐low junction (or LBSF) beneath the contacts. Float zone materials of different resistivities have been investigated.

The experimental results are explained by three‐dimensional finite difference simulations for the open‐circuit voltage, the short‐circuit current and the fill factor.
Renaissance of Czochralski silicon photovoltaics
Authors: Mitchell K. W.
Published: July 2007

The message of this paper is simple. Many of the concepts developed in the 1970s and 1980s that defined the limitations of Czochralski (Cz) silicon photovoltaic technology need to be re‐examined in light of new developments in all areas of the technology, from silicon feedstock costs, to Czochralski crystal growth, to the introduction of wire saw technology, to novel cell designs and processing. Present studies indicate that Czochralski silicon is capable of achieving module costs in the $2 W−−1 range.

Programs to reduce manufacturing costs by reducing the direct and indirect material costs and improving process throughput and yields are showing success.
Defining terms for crystalline silicon solar cells
Authors: Basore Paul A.
Published: July 2007

Sandia National Laboratories manages the US Department of Energy's program supporting photovoltaic technology based on crystalline silicon. In this role, Sandia has favored terminology for use in this program. Terms defined and presented here are for the description of different types of crystalline silicon based on grain size, the description of cell area and the description of module area. While these terms have not been formally established as an international standard, it is hoped that the majority of the photovoltaic community will adopt these terms voluntarily.
‘Wild Ideas’: Radiation‐resistant silicon solar cells
Authors: Wenham S. R.
Published: July 2007

Innovative cell structures for thin‐film crystalline silicon solar cells should facilitate the achievement of relatively high performance from poor material quality. In particular, a design strategy based on heavily doped, multiple interleaved n‐ and p‐type layers, in conjunction with the buried‐contact solar cell approach, is presented. an example design is modelled to demonstrate the corresponding effective ‘radiation hardness’ and the ability to achieve high performance, even with poor minority carrier diffusion lengths expected at end‐of‐life (EOL) for a space cell. Results of modelling indicate that degradation in performance, sustained through typical space radiation damage, can be limited to approximately 5%. Using the same approach for terrestrial thin‐film crystalline silicon cells fabricated from low‐quality, low‐cost material, eficiencies well above 16% should be feasible.
Worldwide photovoltaic market growth 1985–2000
Authors: Gay Charles F. , Eberspacher Chris
Published: July 2007

The combination of a rising demand for reliable, low‐cost energy and an increased awareness of environmental quality issues has created new business opportunities for photovoltaics, especially in applications without an installed electric utility grid line.
Three‐dimensional numerical analysis of contact geometry in back‐contact solar cells
Authors: Ohtsuka Hiroyuki , Ohkura Yasuyuki , Uematsu Tsuyoshi , Warabisako Terunori
Published: July 2007

The device characteristics of back‐contact solar cells, in which both p‐ and n‐type contacts are integrated on the rear surface, are analyzed using a newly developed three‐dimensional solar cell computing program. Comparing the characteristics of line‐ and point‐contact models having the same contact area shows that, contrary to general expectation, the conversion efficiency of line‐contact cells is higher than that of point‐contact cells. Finally, the design criteria for achieving a conversion effciency higher than 24% are discussed.
An alternation of the equilibrium structure symmetry of Li[Cn]1 (n = 7–12) for different n and the correlation with boundary MO features of isolated hydrocarbons [Cn]1
Authors: Balashov Alexander , Yu Ermilov Alexandr
Published: July 2007

The equilibrium geometries of the cylinder‐like lithium hydrocarbon complexes Li[Cn]1 (n = 7–12) are calculated within density functional theory with PBE0 exchange‐correlation potential. The 6‐31 G* basis was set on carbon and lithium atoms while STO‐3G one was chosen for hydrogens. The complexes with odd n possess Cs symmetry for equilibrium structures, and lithium is located near the border of π‐electron system of the hydrocarbons. For complexes Li[Cn]1 with even n (n = 8, 10, 12), the lithium position at the center of benzene ring is stable, and the equilibrium geometry has C2v point symmetry. We have observed correlation between the alternation of the equilibrium structure of the complex and degeneracy of boundary MO of isolated hydrocarbons. By using Cnh symmetry, the π‐MO of the [Cn]1 are found analytically within Huckel model. The nonbonding orbitals with energy α take place only for hydrocarbons with even n. These MO's are characterized by the density distributions among the terminal carbon atoms with sign alternation of AO's contributions. The solution with energy α with analogous distributions is present for larger hydrocarbons [Cn]q with any finite q and even n. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Adaptive control vector parameterization for nonlinear model‐predictive control
Authors: Hartwich Arndt , Schlegel Martin , Würth Lynn , Marquardt Wolfgang
Published: July 2007

Chemical processes are often operated in a dynamic mode. This is always true by definition for the wide class of batch processes and it also holds for the transient phases of continuous processes, caused for example by load or grade changes. Nonlinear model‐predictive control (NMPC) is a powerful approach to deal with the complexity of the related nonlinear control problems aiming for economic optimization. One major element of any NMPC implementation is a dynamic optimization algorithm, which solves the underlying optimization problem efficiently to obtain the optimal control trajectory in real time. Applying nonlinear dynamic optimization to industrial process models results in high calculation times restricting the use of NMPC for most chemical processes. In a previous publication, a method has been presented, which provides the optimizer with a control grid specifically tailored to the problem and therefore facilitates the optimization. In this work, this method is adapted to the on‐line application in NMPC. In contrast to off‐line optimizations, uncertainties and a fixed discrete time sampling have to be taken into account. The approach is applied to a small example and considerable speed‐up is observed. The gain is expected to be even greater for large‐scale industrial problems. Copyright © 2007 John Wiley & Sons, Ltd.
Worker burnout: A dynamic model with implications for prevention and control
Authors: Homer Jack B.
Published: July 2007

This paper explores the dynamics of worker burnout, a process in which a hard‐working individual becomes increasingly exhausted, frustrated, and unproductive. The author's own two‐year experience with repeated cycles of burnout is qualitatively reproduced by a small system dynamics model that portrays the underlying psychology of workaholism. Model tests demonstrate that the limit cycle seen in the base run can be stabilized through techniques that diminish work‐related stress or enhance relaxation. These stabilizing techniques also serve to raise overall productivity, since they support a higher level of energy and more working hours on the average. One important policy lever is the maximum workweek or work limit; an optimal work limit at which overall productivity is at its peak is shown to exist within a region of stability where burnout is avoided. The paper concludes with a strategy for preventing burnout, which emphasizes the individual's responsibility for understanding the self‐inflicted nature of this problem and pursuing an effective course of stability.
Minds over methods
Authors: Saeed Khalid
Published: July 2007

Notes and Insights is a forum for discussion and debate about current issues in the philosophy and application of the system dynamics approach, and a marketplace for the exchange of information about current research, policy issues, and teaching experiences. Manuscripts treating material particularly suited to presentation in short form (less than 2,000 words) should be sent to Erich Zahn, Betriebswirtschaftliches Institut, Universität Stuttgart, Herdweg 23, D‐7000 Stuttgart 1, West Germany.
The role of econometric techniques in dynamic modeling: Systematic bias in the estimation of stock adjustment models
Authors: Forrester Nathan B.
Published: July 2007

Founded in the mid‐1950s, the field of system dynamics has intellectual roots reaching much further into the past. The Archives section of the Review seeks to publish material from that past which can contribute to current theory and practice. The section welcomes previously unpublished but deserving system dynamics work, classics from past system dynamics literature that should receive renewed attention, and previously published articles from other disciplines of particular significance to current system dynamicists. Contributions emphasizing the philosophy and theory of model building, validation. implementation, education, and generic structures are particularly encouraged. Submissions may range in length from notes to main articles but may be edited. Send suggested material, together with a brief introduction placing it in historical and current contexts, to John D. Sterman, System Dynamics Group, M.I.T. E40‐294, Cambridge. MA 02139, U.S.A.
Dynamic models of evolving systems
Authors: Allen Peter M.
Published: July 2007

The basis of systems modeling has been the Newtonian paradigm that states that the behavior of a system can be understood and anticipated by identifying its components and the causal links between them. This assumption leads to a set of deterministic differential or difference equations that governs the behavior of the system. However, such description is achieved by classifying elements into categories and supposing that only the most probable events in fact occur. But real systems evolve, that is, they add and subtract mechanisms, components, and interactions over time; the deterministic model does not reflect this. Clearly, evolution must therefore result from what has been removed in the reduction process. If we are to understand evolving systems better, to anticipate structural changes, and to explore the real impacts of decisions, we must study the effects on system dynamics of nonaverage behavior. We can then gain new insights into the nature of evolutionary processes and build better models that include the adaptive responses from within the system.
Local and global bifurcations in a model of the economic long wave
Authors: Brøns Morten , Sturis Jeppe
Published: July 2007

Combining mathematical analysis with simulations, we obtain a bifurcation diagram for a simple (two state variables) system dynamics model of the economic long wave. Previous linear analysis of the onset of oscillatory behavior (Hopf bifurcation) is extended to include nonlinear effects. It is shown that both sub‐ and supercritical Hopf bifurcation can occur. In the case of subcritical Hopf bifurcation, the system has two coexisting stable solutions, one stationary and one periodic, in a parameter interval below the bifurcation point. The importance of distinguishing between the two types of Hopf bifurcation is discussed. The model also exhibits homoclinic bifurcation to infinity for some parameter combinations: a limit cycle explodes and disappears. Finally, we discuss how the results may apply to other system dynamics models.
Modeling growth strategy in a biotechnology startup firm
Authors: Morecroft John D. W. , Lane David C. , Viita Paul S.
Published: July 2007

The top managers of a biotechnology startup firm agreed to participate in a system dynamics modeling project to help them think about the firm's growth strategy. The article describes how the model was created and used to stimulate debate and discussion about growth management. The paper highlights several novel features about the process used for capturing management team knowledge. A heavy emphasis was placed on mapping the operating structure of the factory and distribution channels. Qualitative modeling methods (structural diagrams, descriptive variable names, and “friendly” algebra) were used to capture the management team's descriptions of the business. Simulation scenarios were crafted to stimulate debate about strategic issues such as capacity allocation, capacity expansion, customer recruitment, customer retention, and market growth, and to engage the management team in using the computer to design strategic scenarios. The article concludes with comments on the impact of the project.
Using system dynamics to measure the value of information in a business firm
Authors: Clark Thomas D. , Augustine Fred K.
Published: July 2007

The primary focus of the research reported in this article was on measuring the value of information in a business firm. A five‐sector system dynamics model was developed and calibrated to an average firm in the U.S. metal‐can production industry. The model was used to test several propositions about the economic value of information. A framework in which to assess information value was developed, and the performance of the firm was assessed using cost, profitability, and efficiency measures for the information attributes of accuracy, timeliness, relevance, and reliability at the strategic, managerial, and operational decision‐making levels of the firm.
Transition in the New York State solid waste system: A dynamic analysis
Authors: Mashayekhi Ali N.
Published: July 2007

This article presents a system model to analyze the solid waste disposal problem in New York State. The model shows that the solid waste system will go through a costly transition from a landfill‐dominated mode of disposal to other disposal alternatives. The solid waste budget has to rise sharply during the transition. Solid waste expenses are financed by local taxes and state financial aid. If local and state governments do not respond rapidly to higher budget requirements, illegal disposal will increase and the total cost of transition will rise. Rapid response of the local authorities to increase the solid waste budget and to lower solid waste generation per capita is necessary to manage the transition with a lower total cost and less illegal disposal.
New technologies in simulation games
Authors: Simons Kenneth L.
Published: July 2007

New computer software allows modelers to create sophisticated educational tools based on models. Such computerized simulation games have generally failed as standalone educational tools. Effective learning requires that computerized simulation games not only simulate models but also give an understanding of structure and dynamics. Feedback during the game may be able to teach this systems understanding without textbook readings. Computerized feedback requires new methods of “expert” computer analysis; some methods are suggested in this article. Simulation games also offer the opportunity to integrate learning of structure and dynamics with learning of facts. Other tools need to be developed to help create simulation games and to give the games abilities that they do not yet have, such as access to data bases of models, pictures, and text, and connections between simulation games.
On the decay properties of solutions to the non-stationary Navier–Stokes equations in R3
Authors: He Cheng , Xin Zhouping
Published: July 2007

In this paper, we study the asymptotic decay properties in both spatial and temporal variables for a class of weak and strong solutions, by constructing the weak and strong solutions in corresponding weighted spaces. It is shown that, for the strong solution, the rate of temporal decay depends on the rate of spatial decay of the initial data. Such rates of decay are optimal.
Complete representation of some functionals showing the Lavrentieff phenomenon
Authors: Esposito A. Corbo , Durante T.
Published: July 2007

The functional F(u) = ∫Bf(x, Du) is considered, where B is the unit ball in R2, u varies in the set of the locally Lipschitz functions on R2 and f belongs to a family containing, as model case, the following integrand:

The computation of the relaxed functional F̄ is provided yielding an explicit representation formula.

This formula nevertheless is not integral, because F̄ is not a measure and does not coincide with the obvious extension of F over all W1,p(B).

This phenomenon is essentially due to the non-standard growth behaviour of f(x, z) in the variable z.
Spectral properties of the equation (∇ + ieA) × u = ±mu
Authors: Elton Daniel M.
Published: July 2007

We develop a spectral theory for the equation (∇ + ieA) × u = ±mu on Minkowski 3-space (one time variable and two space variables); here, A is a real vector potential and the vector product is defined with respect to the Minkowski metric. This equation was formulated by Elton and Vassiliev, who conjectured that it should have properties similar to those of the two-dimensional Dirac equation. Our equation contains a large parameter c (speed of light), and this motivates the study of the asymptotic behaviour of its spectrum as c → +∞. We show that the essential spectrum of our equation is the same as that of Dirac (theorem 3.1), whereas the discrete spectrum agrees with Dirac to a relative accuracy δλ/mc2 ~ O(c−4) (theorem 3.3). In other words, we show that our equation has the same accuracy as the two-dimensional Pauli equation, its advantage over Pauli being relativistic invariance.
New exact multiplicity results with an application to a population model
Authors: Korman Philip , Shi Junping
Published: July 2007

We obtain some new exact multiplicity results for the Dirichlet boundary-value problem

on a unit ball Bn in Rn. We consider several classes of nonlinearities f(u), including both positive and sign-changing cases. A crucial part of the proof is to establish positivity of solutions for the corresponding linearized problem. As an application we obtain exact multiplicity results for the Holling-Tanner population model.
Non-classical Riemann solvers and kinetic relations. II. An hyperbolic–elliptic model of phase-transition dynamics
Authors: LeFloch Philippe G. , Thanh Mai Duc
Published: July 2007

This paper deals with the Riemann problem for a partial differential equation's model arising in phase-transition dynamics and consisting of an hyperbolic–elliptic system of two conservation laws. First of all, we provide a complete description of all solutions of the Riemann problem that are consistent with the mathematical entropy inequality associated with the total energy of the system. Second, following Abeyaratne and Knowles, we impose a kinetic relation to determine the dynamics of subsonic phase boundaries. Based on the requirement that subsonic phase boundaries are preferred whenever available, we determine the corresponding wave curves associated with composite waves (shocks, rarefaction fans, phase boundaries). It turns out that even after the kinetic relation is imposed, the Riemann problem may admit up to two solutions. A nucleation criterion is necessary to select between a solution remaining in a single phase and a solution containing two phase boundaries. Alternatively, a strong assumption on the kinetic relation ensures that the Riemann solution is unique and depends continuously upon its initial data.
Masked factorable matrices
Authors: Sinnamon Gord
Published: July 2007

The class of masked factorable matrices is introduced and simple necessary and sufficient conditions are given for matrices in the class to represent bounded transformations between Lebesgue sequence spaces.
Perturbation of domain: ordinary differential equations
Authors: Mason C.
Published: July 2007

We study a boundary perturbation problem for a one-dimensional Schrödinger equation in which the potential has a regular singularity near the perturbed end point. We give the asymptotic behaviour of the eigenvalues under the perturbation. This problem arose out of the author's studies of singular elliptic operators in higher dimensions and we illustrate this point with an example. The class of potentials to which this method applies is larger than that covered by standard results, which assume uniform ellipticity of the operator or a perturbative term that is analytic in the perturbation parameter.
Consequences of the connection formulae for Sturm-Liouville spectral functions
Authors: Riehl S. M.
Published: July 2007

For a special case of the Sturm-Liouville equation, −(py′)′ + qy = λwy on [0, ∞) with the initial condition y(0) cos α + p(0)y′(0) sin α = 0, α ∈ [0, π), it is shown that, given the spectral derivative for two values of α ∈ [0, π) at a fixed μ = Re{λ} ≥ Λ0, it is possible to uniquely determine . An explicit formula is derived to accomplish this. Further, in a more general case of the Sturm-Liouville problem for μ with both finite and positive, then the following inequality holds
On the Dirichlet problem with several volume constraints on the level sets
Authors: Stepanov Eugene , Tilli Paolo
Published: July 2007

We consider minimization problems involving the Dirichlet integral under an arbitrary number of volume constraints on the level sets and a generalized boundary condition. More precisely, given a bounded open domain Ω ⊂ Rn with smooth boundary, we study the problem of minimizing ∫Ω |∇u|2 among all those functions u ∈ H1 that simultaneously satisfy n-dimensional measure constraints on the level sets of the kind |{u = li}| = αi, i = 1,…, k, and a generalized boundary condition u ∈ K. Here, K is a closed convex subset of H1 such that ; the invariance of K under provides that the condition u ∈ K actually depends only on the trace of u along ∂Ω.

By a penalization approach, we prove the existence of minimizers and their Hölder continuity, generalizing previous results that are not applicable when a boundary condition is prescribed.

Finally, in the case of just two volume constraints, we investigate the Γ-convergence of the above (rescaled) functionals when the total measure of the two prescribed level sets tends to saturate the whole domain Ω. It turns out that the resulting Γ-limit functional can be split into two distinct parts: the perimeter of the interface due to the Dirichlet energy that concentrates along the jump, and a boundary integral term due to the constraint u ∈ K. In the particular case where K = H1 (i.e. when no boundary condition is prescribed), the boundary term vanishes and we recover a previous result due to Ambrosio et al.
Infinitely many arbitrarily small positive solutions for the Dirichlet problem involving the p-Laplacian
Authors: Anello Giovanni , Cordaro Giuseppe
Published: July 2007

In this paper we present a result of existence of infinitely many arbitrarily small positive solutions to the following Dirichlet problem involving the p-Laplacian,

where Ω ∈ RN is a bounded open set with sufficiently smooth boundary ∂Ω, p > 1, λ > 0, and f: Ω × R → R is a Carathéodory function satisfying the following condition: there exists t̄ > 0 such that

Precisely, our result ensures the existence of a sequence of a.e. positive weak solutions to the above problem, converging to zero in L∞(Ω).
Diffusive-dispersive travelling waves and kinetic relations. II A hyperbolic–elliptic model of phase-transition dynamics
Authors: Bedjaoui Nabil , LeFloch Philippe G.
Published: July 2007

We deal here with a mixed (hyperbolic-elliptic) system of two conservation laws modelling phase-transition dynamics in solids undergoing phase transformations. These equations include nonlinear viscosity and capillarity terms. We establish general results concerning the existence, uniqueness and asymptotic properties of the corresponding travelling wave solutions. In particular, we determine their behaviour in the limits of dominant diffusion, dominant dispersion or asymptotically small or large shock strength. As the viscosity and capillarity parameters tend to zero, the travelling waves converge to propagating discontinuities, which are either classical shock waves or supersonic phase boundaries satisfying the Lax and Liu entropy criteria, or else are undercompressive subsonic phase boundaries. The latter are uniquely characterized by the so-called kinetic function, whose properties are investigated in detail here.
On Diophantine approximations of the solutions of q-functional equations
Authors: Matala-aho Tapani
Published: July 2007

Given a sequence of linear forms

in m ≥ 2 complex or p-adic numbers α1, …,αm ∈ Kv with appropriate growth conditions, Nesterenko proved a lower bound for the dimension d of the vector space Kα1 + ··· + Kαm over K, when K = Q and v is the infinite place. We shall generalize Nesterenko's dimension estimate over number fields K with appropriate places v, if the lower bound condition for |Rn| is replaced by the determinant condition. For the q-series approximations also a linear independence measure is given for the d linearly independent numbers. As an application we prove that the initial values F(t), F(qt), …, F(qm−1t) of the linear homogeneous q-functional equation

where N = N(q, t), Pi = Pi(q, t) ∈ K[q, t] (i = 1, …, m), generate a vector space of dimension d ≥ 2 over K under some conditions for the coefficient polynomials, the solution F(t) and t, q ∈ K*.
Hyperbolic inverse boundary-value problem and time-continuation of the non-stationary Dirichlet-to-Neumann map
Authors: Kurylev Yaroslav , Lassas Matti
Published: July 2007

Let M be a compact Riemannian manifold with non-empty boundary M. In this paper we consider an inverse problem for the second-order hyperbolic initial-boundary-value problem utt + but + a(x, D)u = 0 in M R+, u|MR+ = f, u|t=0 = ut|t=0 = 0. Our goal is to determine (M, g), b and a(x, D) from the knowledge of the non-stationary Dirichlet-to-Neumann map (the hyperbolic response operator) RT, with sufficiently large T 0. The response operator RT is the map , where is the normal derivative of the solution of the initial-boundary-value problem.

More specifically, we show the following.

(i)

It is possible to determine Rt for any t 0 if we know RT for sufficiently large T and some geometric condition upon the geodesic behaviour on (M, g) is satisfied.

(ii)

It is then possible to determine (M, g) and b uniquely and the elliptic operator a(x, D) modulo generalized gauge transformations.
Singular limit of reactiondiffusion systems and modified motion by mean curvature
Authors: Logak E.
Published: July 2007

We consider two model reaction-diffusion systems of bistable type arising in the theory of phase transition; they appear in various physical contexts, such as thin magnetic films and diblock copolymers. We prove the convergence of the solution of these systems to the solution of free-boundary problems involving modified motion by mean curvature.
Socially meaningful syntactic variation in sign-based grammar
Authors: BENDER EMILY M.
Published: July 2007

In this article, I investigate the implications of socially meaningful sociolinguistic variation for competence grammar, working from the point of view of HPSG as a kind of performance-plausible sign-based grammar. Taking data from African American Vernacular English variable copula absence as a case study, I argue that syntactic constraints and social meaning are intertwined. I present an overview of the literature on social meaning, discuss what grammars are models of, and argue that in order to model socially meaningful variation, competence grammars need to be extended to include social meaning, precompiled phrases, and probabilistic or frequentistic information. I then explore different heuristics for defining the boundaries of competence grammar and discuss the commonalities between the proposed additions and the kind of linguistic knowledge which is generally assumed to comprise competence grammar.
The New Era of Eclipsing Binary Research with Large Telescopes
Authors: Ribas Ignasi
Published: July 2007

The advent of larger telescopes and powerful instrumentation enables the exploration of new aspects of faint eclipsing binaries that are just now becoming accessible. An example of this are eclipsing binaries in Local Group galaxies such as the LMC, SMC, M31 and M33, whose study yields not only stellar properties of stars formed in different chemical environments (thus providing useful model tests) but also direct distance determinations to the host galaxies. In general this is also applicable to eclipsing binaries belonging to any stellar ensemble. Another example is the observation and study of eclipsing very-low mass stars, brown dwarfs and planets. Besides the need for large telescopes because of their faintness, these also benefit from improved observational capabilities in the infrared spectral windows. Here we discuss the prospects for eclipsing binary research using photometry and spectroscopy from large telescopes.
Classical Observations of Visual Binary and Multiple Stars
Authors: Mason Brian D.
Published: July 2007

Changes in the double star database are highlighted, describing various methods of observation (both historically and those of the past few years) and their effectiveness in different regimes of separation space. The various niches for wide- and narrow-field work as they apply to double and multiple stars are examined and the different types of information which each can provide are described. Despite the significant growth of the double star database, much can still be done, such as finding lost pairs, filling in missing parameters so that observing programs can select all stars appropriate to their capabilities, or providing at least gross kinematic descriptions. After more than 20 years of successful work, speckle interferometry and conventional CCD astrometry have replaced filar micrometry and photography as preferred classical techniques. Indeed, most work in filar micrometry is now being done by amateurs. Work on pairs described as neglected in the last major WDS data release (2001) is given as a specific example. Finally, the continued need to publish data in classical double star parameters is also discussed.
Bipolar Jets, Hot Interaction Regions, and Colliding Winds in OB Interacting Binaries
Authors: Peters Geraldine J.
Published: July 2007

Contemporary information on the nature of the circumstellar environment in early-type interacting binaries derived from observation is discussed. Emphasis is placed on results from FUV spectroscopy. New spectra from the FUSE spacecraft and earlier FUV observations with IUE have revealed the presence of hot interaction regions, bipolar outflows, splash outflows, and accretion hot spots in Algol-type systems with B-type mass gainers. In addition, close O-type pairs and systems containing O + W stars show a shock-heated region generated from their colliding winds. Recent FUSE observations of an apparent hot accretion spot and associated splash plasma in the direct-impact system U Cephei are presented.
Close Binary Star Observables: Modeling Innovations 2003-06
Authors: Wilson R. E.
Published: July 2007

Innovative work on close binary models in 2003-06 improved upon synthesized line spectra, line profiles, and polarimetry; developed new ways of parameter estimation; and increased solution effectiveness and efficiency. Recent applications demonstrate the analytic power of binary system line spectrum models that pre-date the triennium. X-ray binary line profiles and radial velocity curves were refined by solution of the radiative transfer problem with specific inclusion of X-irradiation. Model polarization curves were generated by Monte Carlo experiments with multiple Thomson scattering in thin and thick binary system disks. In the parameter estimation area, independent developments by two groups now allow measurement of ephemerides, apsidal motion, and third body parameters from whole light and velocity curves, to supplement the traditional way of eclipse timings. Although the new route to those parameters is not well known within the ephemeris community, there are accuracy advantages and the number of applications is increasing. Numerical solution experiments on photometric mass ratios have checked two views of their intuitive basis, and show that mass ratios are well determined where star radii and limiting lobe radii are both well determined, which is for semi-detached or over-contact binaries with total-annular eclipses. Solution efficiency and automatic operation is needed for processing of light curves from large surveys, and will also be valuable for preliminary solutions of individually observed binaries. Neural networks have mainly been used for classification, and now a neural network program reliably finds preliminary solutions for W UMa binaries. Archived model light curves and Fourier fitting also are being pursued for classification and for preliminary solutions. Light curves in physical units such as erg·sec−1·cm−3 now allow direct distance estimation by combining the absolute accuracy of model stellar atmospheres with the astrophysical detail of a physical close binary model, by means of rigorous scaling between surface emission and observable flux. A Temperature-distance (T-d) theorem specifies conditions under which temperatures of both stars and distance can be found from light and velocity curves.
Evaluating the Gaia Contribution to the Field of Eclipsing Binaries with Ground-Based Spectroscopy and Hipparcos Photometry
Authors: Niarchos P. G. , Munari U. , Zwitter T.
Published: July 2007

During its definition phase, ESA's Cornerstone mission Gaia was designed to perform extremely accurate photometry in 10 medium plus 5 broad bands and to collect about 90 epoch spectra with a resolving power of 11500 and a wavelength range 8480–8740Å (centered on the CaII triplet in the far red). Combining epoch photometry from the ground and the Hipparcos mission with ground-based spectra strictly simulating Gaia ones, we have investigated in a series of papers the performance expected from Gaia on SB2 EBs. We review here the results we obtained. The Gaia design is now under major revision, and its impact on EBs will be briefly addressed.
Fragile Binaries: Observational Leverage on Difficult Astrophysical Problems
Authors: Oswalt T.D. , Johnston K.B. , Rudkin M. , Vaccaro T. , Valls-Gabaud D.
Published: July 2007

Loosely bound,fragilebinary stars, whose separations may reach ∼ 0.1 pc, are like open clusters with two coeval components. They provide a largely overlooked avenue for the investigation of many astrophysical questions. For example, the orbital distribution of fragile binaries with two long-lived main-sequence components provides a sensitive test of the cumulative effects of the Galactic environment. In pairs where one component is evolved, the orbits have been amplified by post-main-sequence mass loss, potentially providing useful constraints on the initial-to-final mass relation for white dwarfs. The nearly featureless spectra of cool white dwarfs usually provide little information about intrinsic radial velocity, full space motion, population membership, metallicity, etc. However, distant main sequence companions provide benchmarks against which those properties can be determined. In addition, the cooling ages of white dwarf components provide useful limits on the ages of their main sequence companions, independent of other stellar age determination methods. This paper summarizes some of the ways fragile binaries provide useful leverage on these and other problems of interest.
The Ejection of Runaway Massive Binaries
Authors: McSwain M. Virginia , Ransom Scott M. , Boyajian Tabetha S. , Grundstrom Erika D. , Roberts Mallory S.E.
Published: July 2007

The runaway O-type stars HD 14633 and HD 15137 are both SB1 systems that were probably ejected from the open cluster NGC 654. Were these stars dynamically ejected by close gravitational encounters in the dense cluster, or did the binaries each receive a kick from a supernova in one member? We present new results from our investigation of the optical, X-ray, and radio properties of these binary systems to discuss the probable ejection scenarios. We argue that these binaries may have been ejected via dynamical interactions in the dense cluster environment.
Catalogs of Wide Binaries: Impact on Galactic Astronomy
Authors: Chanamé Julio
Published: July 2007

Wide binaries, particularly in large numbers and as free from selection biases as possible, constitute a largely overlooked tool for studying the Galaxy. The goal of this review is to highlight the potential inherent to large samples of field wide binaries for research on problems as varied as star formation in the early Galaxy, the nature of halo dark matter, the evolution of the stellar halo, new geometric distances, metallicities, masses, and ages of field stars and white dwarfs, and much more. Using the Revised NLTT as an illustrative example, I review the main steps in the assembly of a large catalog of wide binaries useful for multiple applications. The capability of cleanly separating between the Galactic disk and halo populations using good colors and proper motions is emphasized. The critical role of large surveys for research on wide binaries as well as for the better understanding of the Galaxy in general is stressed throughout. Finally, I point out the potential for assembling new samples of wide binaries from available proper-motion surveys, and report on current efforts of using the SDSS towards this goal.
Eclipsing Binaries in the LMC: a Wealth of Data for Astrophysical Tests
Authors: Derekas A. , Kiss L. L. , Bedding T. R.
Published: July 2007

We have analysed publicly available MACHO observations of 6833 variable stars in the Large Magellanic Cloud, classified as eclipsing binaries. After finding that a significant fraction of the sample was misclassified, we redetermined periods and variability class for all stars, producing a clean sample of 3031 eclipsing binaries. We have investigated their distribution in the period-color-luminosity space, which was used, for example, to assign a foreground probability to every object and establish new period-luminosity relations to selected types of eclipsing stars. We found that the orbital period distribution of LMC binaries is very similar to those of the SMC and the Milky Way. We have also determined the rate of period change for every star using the O-C method, discovering about 40 eclipsing binaries with apsidal motion, 45 systems with cyclic period changes and about 80 stars with parabolic O-C diagrams. In a few objects we discovered gradual amplitude variation, which can be explained by changes in the orbital inclination caused by a perturbing third body in the system.
The Influence of Binarity on Stellar Activity
Authors: Oláh Katalin
Published: July 2007

Activity of late type stars is enhanced by fast rotation, which is maintained in nearly synchronized close binary systems. Magnetic activity originates in the deep convection zones of stars from where magnetic flux tubes emerge to their surfaces. The gravitational forces in binaries help the clustering of activity features giving rise to active longitudes. These preferred longitudes are observed in binaries from dwarfs to giants. Differential rotation is found in many active stars that are components of binary systems. If these binaries are circularized and nearly synchronized, then there will be a corotation latitude in their surfaces, and its position can be determined by observations and by theoretical calculations. Enhanced activity in binaries could have a reverse effect as well: strong magnetism in a binary component can modify the orbital period by the cyclic exchange of kinetic and magnetic energy in its convective envelope.
Summary of Observational Aspects
Authors: Scarfe C. D.
Published: July 2007

This summary covers the first two days of the Symposium, in which the oral papers were primarily observational in nature. It also mentions several of the many observational posters associated with those discussions.
Analyses of internal solitary waves generated at the Columbia River plume front using SAR imagery
Authors: Pan Jiayi , Jay David A. , Orton Philip M.
Published: July 2007

Internal solitons generated at the Columbia River plume front during ebb tide are displayed on a synthetic aperture radar (SAR) image taken on 26 July 2004 at 14:24:22 UTC. Scale analyses suggest that these internal solitons belong to the finite‐depth category. A theoretical model, relating the radar backscatter cross section to dynamic parameters of internal solitons in the continuous stratification, is developed. Using the model and background stratification data collected by the River Influences on Shelf Ecosystem (RISE) project in July 2004, we extract the soliton dynamic parameters of the half‐width, amplitude, phase speed, and average energy flux per crest length along a typical section across the internal solitons. The observed stratification is simulated by using a theoretical model parameterized by pycnocline depth, thickness, and maximum buoyancy frequency. The half‐width, amplitude, phase speed, and energy flux of the leading soliton at the section are 119.3 m, 9.3 m, 0.69 m s−1, and 417.4 W m−1 with the uncertainty ranges of ±14.7 m, ±2.6 m, ±0.10 m s−1, and ±281.6 W m−1, respectively. Sensitivity analyses reveal that the extraction of the soliton half‐width from the SAR image is not affected by the stratification. The amplitude is less influenced by the pycnocline thickness than the depth and is independent of the maximum buoyancy frequency.
Analysis of Gravity Recovery and Climate Experiment time‐variable mass redistribution signals over North America by means of principal component analysis
Authors: Rangelova E. , van der Wal W. , Braun A. , Sideris M. G. , Wu P.
Published: July 2007

Four years of data provided by the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) satellite mission are analyzed over North America using principal component analysis (PCA). Three hydrology models [Global Land Data Assimilation System (GLDAS), Climate Prediction Center (CPC), and Land Dynamics (LaD)] are used to analyze the water mass changes over the same area and time period. The GRACE‐observed and the hydrology models mass changes are compared spatially and temporally, and good agreement is observed. Two signal modes are found to represent more than 65% of the GRACE‐observed mass variability. The first mode represents mainly mass changes related to the snow accumulation and melting and has maximum amplitude in the western Cordillera and Québec‐Labrador regions. The second mode comprises long‐term positive mass changes in central and eastern Canada and negative mass changes in Alaska. In addition, two more spatiotemporal patterns that explain 14% of the GRACE‐observed mass variability are extracted and studied, but no definite relation to hydrology is established. While the GLDAS model agrees very well with the GRACE observations, it is found that the CPC model also provides useful information for validating the GRACE‐observed mass changes in North America. On the basis of the results of this study, we can state that principal component analysis is a useful technique for extracting and validating regional hydrology signals from GRACE gravity field data. The main advantage of PCA is the capability to extract interannual and nonperiodic mass changes in addition to long‐term and periodic variations.