2,144 research outputs found
Anisotropic diffusion in square lattice potentials: giant enhancement and control
The unbiased thermal diffusion of an overdamped Brownian particle in a square
lattice potential is considered in the presence of an externally applied ac
driving. The resulting diffusion matrix exhibits two orthogonal eigenvectors
with eigenvalues , indicating anisotropic diffusion along a "fast"
and a "slow principal axis". For sufficiently small temperatures, may
become arbitrarily large and at the same time arbitrarily small. The
principal diffusion axis can be made to point into (almost) any direction by
varying either the driving amplitude or the coupling of the particle to the
potential, without changing any other property of the system or the driving.Comment: 7 pages, 7 figure
Exploiting lattice potentials for sorting chiral particles
Several ways are demonstrated of how periodic potentials can be exploited for
sorting molecules or other small objects which only differ by their chirality.
With the help of a static bias force, the two chiral partners can be made to
move along orthogonal directions. Time-periodic external forces even lead to
motion into exactly opposite directions.Comment: 4 pages, 4 figure
Location of the Lee-Yang zeros and absence of phase transitions in some Ising spin systems
We consider a class of Ising spin systems on a set \Lambda of sites. The
sites are grouped into units with the property that each site belongs to either
one or two units, and the total internal energy of the system is the sum of the
energies of the individual units, which in turn depend only on the number of up
spins in the unit. We show that under suitable conditions on these interactions
none of the |\Lambda| Lee-Yang zeros in the complex z = exp{2\beta h} plane,
where \beta is the inverse temperature and h the uniform magnetic field, touch
the positive real axis, at least for large values of \beta. In some cases one
obtains, in an appropriately taken \beta to infinity limit, a gas of hard
objects on a set \Lambda'; the fugacity for the limiting system is a rescaling
of z and the Lee-Yang zeros of the new partition function also avoid the
positive real axis. For certain forms of the energies of the individual units
the Lee-Yang zeros of both the finite- and zero-temperature systems lie on the
negative real axis for all \beta. One zero-temperature limit of this type, for
example, is a monomer-dimer system; our results thus generalize, to finite
\beta, a well-known result of Heilmann and Lieb that the Lee-Yang zeros of
monomer-dimer systems are real and negative.Comment: Plain TeX. Seventeen pages, five figures from .eps files. Version 2
corrects minor errors in version
Beach changes at Nauset Inlet, Cape Cod, Massachusetts, 1670-1981
A historical study of barrier beach and inlet changes for the Nauset Inlet
region, Cape Cod, Massachusetts, was performed to document patterns of beach
and inlet change as a preliminary to designing and carrying out ffeld studies
of inlet sediment transport. 120 historical charts from 1670 and 125 sets of
aerial photographs from 1938 formed the basis for this study. Specific
aspects of barrier beach and inlet change addressed include onshore barrier
beach movement, longshore tidal inlet migration, and longshore sand bypassing
past the inlet. In an effort to correlate forcing events with barrier changes,
an exhaustive study of the local storm climate was performed. Detailed
treatment of the specific mechanisms responsible for Nauset Inlet migration
episodes in a direction opposite the dominant littoral drift are treated in a
companion paper by Aubrey, Speer, and Ruder (1982). Documentation of the data
base available for the Nauset Area is presented herein as appendices.Prepared for NOAA, 0ffice of Sea Gnant under Grant NA 80-AA-D-
00077 (R/B-21) and for the U.S. Army Research 0ffice under Grant
DAAG29-81-K-0004
Recommended from our members
Improved Criteria for Acceptable Yield Point Elongation in Surface Critical Steels
Yield point elongation (YPE) is considered undesirable in surface critical applications where steel is formed since "strain lines" or Luders bands are created during forming. This project will examine in detail the formation of luders bands in industrially relevant strain states including the influence of substrate properties and coatings on Luders appearance. Mechanical testing and surface profilometry were the primary methods of investigation
Hydrodynamical Modeling of a Multiple‐Inlet Estuary/Barrier System: Insight Into Tidal Inlet Formation and Stability
Two specific questions are addressed concerning the role of tidal hydrodynamics in determining the long‐term morphologic evolution of the Nauset Beach‐Monomoy Island barrier system and the Chatham Harbor‐Pleasant Bay tidal estuary, Massachusetts: (1) why do the barrier and estuary exhibit a long‐term (∼150 yr) cycle of new inlet formation, and (2) once a new inlet forms, why is the resulting multiple inlet system unstable? To address these questions, a branched 1‐d numerical model is used to recreate the basic flow patterns in the tidal estuary at ten‐year intervals during the last half century and also to recreate flow conditions shortly before and shortly after the formation of the new inlet. Results suggest that an inlet will form through Nauset Beach once southerly elongation of the barrier has led to a critical head across the barrier at high tide. If this critical head (enhanced by storm surge and wave set‐up) exists at high tide during consecutive tidal cycles, flood currents can deepen the overwash channel sufficiently to enable the stronger ebb currents to complete the formation process. Once a new inlet has formed, the surface gradient and tidal discharge are drastically reduced along the pre‐existing channel to the south of the inlet. This reduction eliminates the tidal scouring action needed to keep the channel open. Rapid shoaling within the channel to the south of the new inlet completes the hydrodynamic decoupling of the northern and southern sections of the estuary.https://scholarworks.wm.edu/vimsbooks/1037/thumbnail.jp
Austenite Formation and Manganese Partitioning during Double Soaking of an Ultralow Carbon Medium-Manganese Steel
Double soaking (DS) is a thermal processing route intended to produce austenite–martensite microstructures in steels containing austenite-stabilizing additions and consists of intercritical annealing (primary soaking), followed by heating and brief isothermal holding at an increased temperature (secondary soaking), and quenching. Herein, experimental dilatometry during DS of a medium-manganese (Mn) steel with nominally 7 wt% Mn and an ultralow residual carbon concentration, in combination with phase-field simulations of austenite formation during secondary soaking, is presented. The feasibility of maintaining heterogeneous Mn distributions during DS is demonstrated and insight is provided on the effects of the secondary soaking temperature and prior Mn distribution on the ferrite-to-austenite phase transformation during the secondary soaking portion of the DS treatment
Simulation of Heavily Irradiated Silicon Pixel Sensors and Comparison with Test Beam Measurements
Charge collection measurements performed on heavily irradiated p-spray DOFZ
pixel sensors with a grazing angle hadron beam provide a sensitive
determination of the electric field within the detectors. The data are compared
with a complete charge transport simulation of the sensor which includes signal
trapping and charge induction effects. A linearly varying electric field based
upon the standard picture of a constant type-inverted effective doping density
is inconsistent with the data. A two-trap double junction model implemented in
the ISE TCAD software can be tuned to produce a doubly-peaked electric field
which describes the data reasonably well. The modeled field differs somewhat
from previous determinations based upon the transient current technique. The
model can also account for the level of charge trapping observed in the data.Comment: 8 pages, 11 figures. Talk presented at the 2004 IEEE Nuclear Science
Symposium, October 18-21, Rome, Italy. Submitted to IEEE Transactions on
Nuclear Scienc
A Case Study of a Co-Instructed Multidisciplinary Senior Capstone Project in Sustainability
As societal challenges involving sustainable development increase, the need to effectively integrate this inherently multidisciplinary topic into existing curricula becomes more pressing. Multidisciplinary, team-taught, project-based instruction has shown effectiveness in teaching teamwork, communication, and life-long learning skills, and appreciation for other disciplines. Unfortunately, this instruction mode has not been widely adopted, largely due to its resource-intensiveness. Our proposed co-instruction model of multidisciplinary senior project administration was tested to see if it could effectively teach sustainability topics and duplicate the known benefits of team-taught instruction, while overcoming its resource-intensiveness. A case study of a co-instructed senior project was undertaken with students and faculty from electrical and mechanical engineering, business, political science, and industrial design. The participating students were compared to the control group, i.e. students who chose to complete a traditional disciplinary senior project instead. Extensive assessment was performed with pre/post quizzes, online surveys, focus groups, and course deliverables. The multidisciplinary projects outperformed traditional senior projects in 4 out of the 5 participating courses. However, the students in the multidisciplinary project rated their satisfaction with the experience lower on average than the control group. A strong, positive correlation between students’ project satisfaction and rating of other instruction aspects (0.50 \u3c r \u3c 0.7, p \u3c 0.01) was discovered, which has implications for all project-based instruction. Participating faculty generally found the process illuminating and engaged in scholarship and creative endeavors as a result
A LISTING OF THE FLORA AND FAUNA OF SAINT HELENA ISLAND, SOUTH CAROLINA WITH EMPHASIS ON HISTORIC PENN CENTER
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