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L Santen

Publications and source records attributed to L Santen.

7 recordsLinked to original sources
PubMed2003

Shock formation in an exclusion process with creation and annihilation.

We investigate shock formation in an asymmetric exclusion process with creation and annihilation of particles in the bulk. We show how the continuum mean-field equations can be studied analytically and hence derive the phase diagrams of the model. In the large system-size limit direct simulations of the model show that the stationary state is correctly described by the mean-field equations, thus the predicted mean-field phase diagrams are expected to be exact. The emergence of shocks and the structure of the phase diagram are discussed. We also analyze the fluctuations of the shock position by using a phenomenological random walk picture of the shock dynamics. The stationary distribution of shock positions is calculated, by virtue of which the numerically determined finite-size scaling behavior of the shock width is explained.

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PubMed2001

Boundary induced phase transitions in driven lattice gases with metastable states.

We study the effect of metastability onto boundary induced phase transitions in a driven lattice gas. The phase diagram for open systems, parameterized by the input and output rates, consists of two regions corresponding to the free flow and jammed phase. Both have been entirely characterized. The microscopic states in the high density phase are shown to have an interesting striped structure, which undergoes a coarsening process and survives in the thermodynamic limit.

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PubMed2000

Absence of thermodynamic phase transition in a model glass former

The glass transition can be viewed simply as the point at which the viscosity of a structurally disordered liquid reaches a universal threshold value. But this is an operational definition that circumvents fundamental issues, such as whether the glass transition is a purely dynamical phenomenon. If so, ergodicity gets broken (the system becomes confined to some part of its phase space), but the thermodynamic properties of the liquid remain unchanged across the transition, provided they are determined as thermodynamic equilibrium averages over the whole phase space. The opposite view claims that an underlying thermodynamic phase transition is responsible for the pronounced slow-down in the dynamics at the liquid-glass boundary. Such a phase transition would trigger the dynamic standstill, and then be masked by it. Here we perform Monte Carlo simulations of a two-dimensional system of polydisperse hard disks far within its glassy phase. The approach allows for non-local moves in a way that preserves micro-reversibility. We find no evidence for a thermodynamic phase transition up to very high densities; the glass is thus indistinguishable from the liquid on purely thermodynamic grounds.

Journal Article↗
PubMed1999

Single-vehicle data of highway traffic: a statistical analysis.

In the present paper, single-vehicle data of highway traffic are analyzed in great detail. By using the single-vehicle data directly, empirical time headway distributions and speed-distance relations can be established. Both quantities yield relevant information about the microscopic states. Several fundamental diagrams are also presented, which are based on time-averaged quantities and compared with earlier empirical investigations. In the remaining part, time-series analyses of the averaged as well as the single-vehicle data are carried out. The results will be used in order to propose objective criteria for an identification of the different traffic states, e.g., synchronized traffic.

Journal Article↗
PubMed1997

Teddy says "Hi!": Teddy bear clinics revisited.

Teddy bear/doll clinics continue to offer a feasible, effective opportunity to reach the community's children and their health information needs. Many thanks to Sunny B. Lee, RN, BS (Swedish Covenant Hospital, Chicago), and Kathy Powell, RN, PhD, and Barb Pierce, RN, MS (Children's Hospital, Birmingham).

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