1,718 research outputs found
The asymmetric exclusion process: Comparison of update procedures
The asymmetric exclusion process (ASEP) has attracted a lot of interest not
only because its many applications, e.g. in the context of the kinetics of
biopolymerization and traffic flow theory, but also because it is a
paradigmatic model for nonequilibrium systems. Here we study the ASEP for
different types of updates, namely random-sequential, sequential,
sublattice-parallel and parallel. In order to compare the effects of the
different update procedures on the properties of the stationary state, we use
large-scale Monte Carlo simulations and analytical methods, especially the
so-called matrix-product Ansatz (MPA). We present in detail the exact solution
for the model with sublattice-parallel and sequential updates using the MPA.
For the case of parallel update, which is important for applications like
traffic flow theory, we determine the phase diagram, the current, and density
profiles based on Monte Carlo simulations. We furthermore suggest a MPA for
that case and derive the corresponding matrix algebra.Comment: 47 pages (11 PostScript figures included), LATEX, Two misprints in
equations correcte
Residence time estimates for asymmetric simple exclusion dynamics on stripes
The target of our study is to approximate numerically and, in some particular
physically relevant cases, also analytically, the residence time of particles
undergoing an asymmetric simple exclusion dynamics on a stripe. The source of
asymmetry is twofold: (i) the choice of boundary conditions (different
reservoir levels) and (ii) the strong anisotropy from a nonlinear drift with
prescribed directionality. We focus on the effect of the choice of anisotropy
in the flux on the asymptotic behavior of the residence time with respect to
the length of the stripe. The topic is relevant for situations occurring in
pedestrian flows or biological transport in crowded environments, where lateral
displacements of the particles occur predominantly affecting therefore in an
essentially way the efficiency of the overall transport mechanism
Modeling the Interdependences between Voltage Fluctuation and BTI Aging
With technology scaling, the susceptibility of circuits to different reliability degradations is steadily increasing. Aging in transistors due to bias temperature instability (BTI) and voltage fluctuation in the power delivery network of circuits due to IR-drops are the most prominent. In this paper, we are reporting for the first time that there are interdependences between voltage fluctuation and BTI aging that are nonnegligible. Modeling and investigating the joint impact of voltage fluctuation and BTI aging on the delay of circuits, while remaining compatible with the existing standard design flow, is indispensable in order to answer the vital question, “what is an efficient (i.e., small, yet sufficient) timing guardband to sustain the reliability of circuit for the projected lifetime?” This is, concisely, the key goal of this paper. Achieving that would not be possible without employing a physics-based BTI model that precisely describes the underlying generation and recovery mechanisms of defects under arbitrary stress waveforms. For this purpose, our model is validated against varied semiconductor measurements covering a wide range of voltage, temperature, frequency, and duty cycle conditions. To bring reliability awareness to existing EDA tool flows, we create standard cell libraries that contain the delay information of cells under the joint impact of aging and IR-drop. Our libraries can be directly deployed within the standard design flow because they are compatible with existing commercial tools (e.g., Synopsys and Cadence). Hence, designers can leverage the mature algorithms of these tools to accurately estimate the required timing guardbands for any circuit despite its complexity. Our investigation demonstrates that considering aging and IR-drop effects independently, as done in the state of the art, leads to employing insufficient and thus unreliable guardbands because of the nonnegligible (on average 15% and up to 25%) underestimations. Importantly, considering interdependences between aging and IR-drop does not only allow correct guardband estimations, but it also results in employing more efficient guardbands
Experiential learning about medication adherence
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140039/1/tct12645.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/140039/2/tct12645_am.pd
Dynamics of an exclusion process with creation and annihilation
We examine the dynamical properties of an exclusion process with creation and
annihilation of particles in the framework of a phenomenological domain-wall
theory, by scaling arguments and by numerical simulation. We find that the
length- and time scale are finite in the maximum current phase for finite
creation- and annihilation rates as opposed to the algebraically decaying
correlations of the totally asymmetric simple exclusion process (TASEP).
Critical exponents of the transition to the TASEP are determined. The case
where bulk creation- and annihilation rates vanish faster than the inverse of
the system size N is also analyzed. We point out that shock localization is
possible even for rates proportional to 1/N^a, 1<a<2.Comment: 16 pages, 8 figures, typos corrected, references added, section 4
revise
Ease of use and accuracy of a perinatal measuring device (Episiometer) to ensure correct angle and length of a mediolateral episiotomy: a mixed methods study
Introduction: To guide clinicians in performing mediolateral episiotomies (MLEs) at 60‐degrees, a new clinical innovation called the 'Episiometer' was developed. The aim of this study was to assess the usability and accuracy of the Episiometer in guiding clinicians to perform a safe episiotomy in both low‐ and high‐resource settings.
Design: A prospective, multi‐site Phase‐I clinical trial was conducted between January 2017 and July 2018, involving three international study sites: Australia; Papua New Guinea; and India. The study design was mixed‐methods, incorporating an explanatory sequential design using surveys, clinician interviews and patient chart review to determine the usability and accuracy of the Episiometer. The patient chart review and results of this are discussed in an accompanying article.
Methods: The Episiometer is the clinical innovation designed to attain an episiotomy cutting angle of 60‐degrees. The instrument is designed to assist clinicians to make an accurate and consistent episiotomy cutting angle within a 'safe' green zone between 45–60 degrees and length of at least 4 cm. The instrument also improves the visibility of the 60‐degree line to clinicians, and provides an exact measurement for length (located on the 60‐degree angle line). Clinicians from all three sites were recruited to provide feedback and measurements of incisions performed using the Episiometer (n = 135) following attendance at a minimum of at least one training session with site coordinators. Twenty of these clinicians were then recruited randomly from the sample who responded in the surveys and interviewed face‐to‐face. Patients were followed up 6‐weeks postpartum to monitor potential complications (n = 120).
Results: Overall, the Episiometer was well received by clinicians – particularly by more junior staff members who were significantly more likely to report the Episiometer as being beneficial in guiding a safe MLE compared to their more senior counterparts (P = 0.003 and P = 0.011, respectively). In addition, 89% of incisions (107/120) were within the 'safe zone' between 45‐60 degrees, and 40% (48/120) were made at exactly 60‐degrees. No patient had any degree of perineal tear at follow up.
Conclusion: The Episiometer is a well‐received clinical innovation in both high‐resource and lower resource settings. When used as directed, the Episiometer produces an accurate and safe incision, and reduces variation in clinicians' performance of episiotomy
SNGuess: A method for the selection of young extragalactic transients
With a rapidly rising number of transients detected in astronomy,
classification methods based on machine learning are increasingly being
employed. Their goals are typically to obtain a definitive classification of
transients, and for good performance they usually require the presence of a
large set of observations. However, well-designed, targeted models can reach
their classification goals with fewer computing resources. This paper presents
SNGuess, a model designed to find young extragalactic nearby transients with
high purity. SNGuess works with a set of features that can be efficiently
calculated from astronomical alert data. Some of these features are static and
associated with the alert metadata, while others must be calculated from the
photometric observations contained in the alert. Most of the features are
simple enough to be obtained or to be calculated already at the early stages in
the lifetime of a transient after its detection. We calculate these features
for a set of labeled public alert data obtained over a time span of 15 months
from the Zwicky Transient Facility (ZTF). The core model of SNGuess consists of
an ensemble of decision trees, which are trained via gradient boosting.
Approximately 88% of the candidates suggested by SNGuess from a set of alerts
from ZTF spanning from April 2020 to August 2021 were found to be true relevant
supernovae (SNe). For alerts with bright detections, this number ranges between
92% and 98%. Since April 2020, transients identified by SNGuess as potential
young SNe in the ZTF alert stream are being published to the Transient Name
Server (TNS) under the AMPEL_ZTF_NEW group identifier. SNGuess scores for any
transient observed by ZTF can be accessed via a web service. The source code of
SNGuess is publicly available.Comment: 14 pages, 10 figures, Astronomy & Astrophysics (A&A), Forthcoming
article, source code https://github.com/nmiranda/SNGues
The critical exponents of the two-dimensional Ising spin glass revisited: Exact Ground State Calculations and Monte Carlo Simulations
The critical exponents for of the two-dimensional Ising spin glass
model with Gaussian couplings are determined with the help of exact ground
states for system sizes up to and by a Monte Carlo study of a
pseudo-ferromagnetic order parameter. We obtain: for the stiffness exponent
, for the magnetic exponent
and for the chaos exponent . From Monte Carlo simulations we
get the thermal exponent . The scaling prediction is
fulfilled within the error bars, whereas there is a disagreement with the
relation .Comment: 8 pages RevTeX, 7 eps-figures include
Phase diagrams of in Double Exchange Model with added antiferromagnetic and Jahn-Teller interaction
The phase diagram of the multivalent manganites , in
space of temperature and doping , is a challenge for the theoretical
physics. It is an important test for the model used to study these compounds
and the method of calculation. To obtain theoretically this diagram for
, we consider the two-band Double Exchange Model for manganites with
added Jahn-Teller coupling and antiferromagnetic Heisenberg term. In order to
calculate Curie and N\'{e}el temperatures we derive an effective Heisenberg
model for a vector which describes the local orientation of the total
magnetization of the system. The exchange constants of this model are different
for different space directions and depend on the density of electrons,
antiferromagnetic constants and the Jahn-Teller energy. To reproduce the well
known phase transitions from A-type antiferromagnetism to ferromagnetism at low
and C-type antiferromagnetism to G-type antiferromagnetism at large , we
argue that the antiferromagnetic exchange constants should depend on the
lattice direction. We show that ferromagnetic to A-type antiferromagnetic
transition results from the Jahn-Teller distortion. Accounting adequately for
the magnon-magnon interaction, Curie and N\'{e}el temperatures are calculated.
The results are in very good agreement with the experiment and provide values
for the model parameters, which best describe the behavior of the critical
temperature for .Comment: 13 pages, 5 figure
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