162 research outputs found
On the Fluctuation Relation for Nose-Hoover Boundary Thermostated Systems
We discuss the transient and steady state fluctuation relation for a
mechanical system in contact with two deterministic thermostats at different
temperatures. The system is a modified Lorentz gas in which the fixed
scatterers exchange energy with the gas of particles, and the thermostats are
modelled by two Nos\'e-Hoover thermostats applied at the boundaries of the
system. The transient fluctuation relation, which holds only for a precise
choice of the initial ensemble, is verified at all times, as expected. Times
longer than the mesoscopic scale, needed for local equilibrium to be settled,
are required if a different initial ensemble is considered. This shows how the
transient fluctuation relation asymptotically leads to the steady state
relation when, as explicitly checked in our systems, the condition found in
[D.J. Searles, {\em et al.}, J. Stat. Phys. 128, 1337 (2007)], for the validity
of the steady state fluctuation relation, is verified. For the steady state
fluctuations of the phase space contraction rate \zL and of the dissipation
function \zW, a similar relaxation regime at shorter averaging times is
found. The quantity \zW satisfies with good accuracy the fluctuation relation
for times larger than the mesoscopic time scale; the quantity \zL appears to
begin a monotonic convergence after such times. This is consistent with the
fact that \zW and \zL differ by a total time derivative, and that the tails
of the probability distribution function of \zL are Gaussian.Comment: Major revision. Fig.10 was added. Version to appear in Journal of
Statistical Physic
The Steady State Fluctuation Relation for the Dissipation Function
We give a proof of transient fluctuation relations for the entropy production
(dissipation function) in nonequilibrium systems, which is valid for most time
reversible dynamics. We then consider the conditions under which a transient
fluctuation relation yields a steady state fluctuation relation for driven
nonequilibrium systems whose transients relax, producing a unique
nonequilibrium steady state. Although the necessary and sufficient conditions
for the production of a unique nonequilibrium steady state are unknown, if such
a steady state exists, the generation of the steady state fluctuation relation
from the transient relation is shown to be very general. It is essentially a
consequence of time reversibility and of a form of decay of correlations in the
dissipation, which is needed also for, e.g., the existence of transport
coefficients. Because of this generality the resulting steady state fluctuation
relation has the same degree of robustness as do equilibrium thermodynamic
equalities. The steady state fluctuation relation for the dissipation stands in
contrast with the one for the phase space compression factor, whose convergence
is problematic, for systems close to equilibrium. We examine some model
dynamics that have been considered previously, and show how they are described
in the context of this work.Comment: 30 pages, 1 figur
The Development and Use of Sustainability Criteria in SuRF-UK’s Sustainable Remediation Framework
Sustainability considerations have become widely recognised in contaminated land management and are now accepted as an important component of remediation planning and implementation around the world. The Sustainable Remediation Forum for the UK (SuRF-UK) published guidance on sustainability criteria for consideration in drawing up (or framing) assessments, organised across 15 “headline” categories, five for the environment element of sustainability, five for the social, and five for the economic. This paper describes how the SuRF-UK indicator guidance was developed, and the rationale behind its structure and approach. It describes its use in remediation option appraisal in the UK, and reviews the international papers that have applied or reviewed it. It then reviews the lessons learned from its initial use and the opinions and findings of international commentators, and concludes with recommendations on how the indicator categories might be further refined in the future. The key findings of this review are that the SuRF-UK framework and indicator guidance is well adopted into practice in the UK. It is widely recognised as the most appropriate mechanism to support sustainability-based decision making in contaminated land decision making. It has influenced the development of other national and international guidance and standards on sustainable remediation. However, there is room for some fine tuning of approach based on the lessons learned during its application
Simple deterministic dynamical systems with fractal diffusion coefficients
We analyze a simple model of deterministic diffusion. The model consists of a
one-dimensional periodic array of scatterers in which point particles move from
cell to cell as defined by a piecewise linear map. The microscopic chaotic
scattering process of the map can be changed by a control parameter. This
induces a parameter dependence for the macroscopic diffusion coefficient. We
calculate the diffusion coefficent and the largest eigenmodes of the system by
using Markov partitions and by solving the eigenvalue problems of respective
topological transition matrices. For different boundary conditions we find that
the largest eigenmodes of the map match to the ones of the simple
phenomenological diffusion equation. Our main result is that the difffusion
coefficient exhibits a fractal structure by varying the system parameter. To
understand the origin of this fractal structure, we give qualitative and
quantitative arguments. These arguments relate the sequence of oscillations in
the strength of the parameter-dependent diffusion coefficient to the
microscopic coupling of the single scatterers which changes by varying the
control parameter.Comment: 28 pages (revtex), 12 figures (postscript), submitted to Phys. Rev.
The British Army, information management and the First World War revolution in military affairs
Information Management (IM) – the systematic ordering, processing and channelling of information within organisations – forms a critical component of modern military command and control systems. As a subject of scholarly enquiry, however, the history of military IM has been relatively poorly served. Employing new
and under-utilised archival sources, this article takes the British Expeditionary Force (BEF) of the First World War as its case study and assesses the extent to which its IM system contributed to the emergence of the modern battlefield in 1918. It argues that the
demands of fighting a modern war resulted in a general, but not universal, improvement in the BEF’s IM techniques, which in turn laid the groundwork, albeit in embryonic form, for the IM systems of modern armies.
KEY WORDS: British Army, Information Management, First World War, Revolution in Military Affairs, Adaptatio
Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy
During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly
Spatial clusters of Varroa destructor control strategies in Europe
Publication history: Accepted - 18 May 2022; Published online - 29 June 2022Beekeepers have various options to control the parasitic mite Varroa destructor in honey bee colonies, but no empirical data
are available on the methods they apply in practice. We surveyed 28,409 beekeepers maintaining 507,641 colonies in 30
European countries concerning Varroa control methods. The set of 19 diferent Varroa diagnosis and control measures was
taken from the annual COLOSS questionnaire on honey bee colony losses. The most frequent activities were monitoring of
Varroa infestations, drone brood removal, various oxalic acid applications and formic acid applications. Correspondence
analysis and hierarchical clustering on principal components showed that six Varroa control options (not necessarily the most
used ones) signifcantly contribute to defning three distinctive clusters of countries in terms of Varroa control in Europe.
Cluster I (eight Western European countries) is characterized by use of amitraz strips. Cluster II comprises 15 countries from
Scandinavia, the Baltics, and Central-Southern Europe. This cluster is characterized by long-term formic acid treatments.
Cluster III is characterized by dominant usage of amitraz fumigation and formed by seven Eastern European countries. The
median number of diferent treatments applied per beekeeper was lowest in cluster III. Based on estimation of colony numbers
in included countries, we extrapolated the proportions of colonies treated with diferent methods in Europe. This suggests that
circa 62% of colonies in Europe are treated with amitraz, followed by oxalic acid for the next largest percentage of colonies.
We discuss possible factors determining the choice of Varroa control measures in the diferent clustersOpen access funding provided by University of Graz. The authors have no relevant financial or non-financial interests to disclose. COLOSS and its supporters had no influence on the study design or the decision to publish
Propuesta de alternativa para la pacificación del tránsito frente a la sede 13 (calle 47 entre las carreras 13 y 14) de la Universidad Católica de Colombia
Trabajo de investigaciónEste proyecto busca generar espacios seguros para los peatones, con el fin de reducir los accidentes de tránsito, que al año 2018 según datos del IDECA, en la intersección de la carrera 13 con calle 47 se establecieron en 13.
Gracias a las diferentes alternativas de pacificación del tránsito que se encuentran disponibles en la actualidad, se ha logrado disminuir los accidentes de tránsito, es por esto, que en esta investigación se propone diseñar un paso a nivel sobre la calle 47 entre Carreras 13 y 14, con el fin de ampliar las vías peatonales basándose en la cartilla de andenes para Bogotá de la Secretaria Distrital De Planeación y el Decreto 327 del 2004. De igual manera se verifico el nivel de servicio actual del andén del costado norte y el nivel de servicio que se prestará con las alternativas propuestas, finalmente se llevó a cabo una simulación de la condición actual de movilidad del corredor con el fin de determinar cómo se comportara el corredor con la alternativa planteada en la investigación.
Todas las conclusiones de la investigación se basan en mejorar las condiciones de movilidad peatonal con el fin de conseguir una movilidad más segura y que no represente conflicto entre los diferentes actores viales del corredor.INTRODUCCIÓN
1. ANTECEDENTES Y JUSTIFICACIÓN
2. PLANTEAMIENTO Y FORMULACIÓN DEL PROBLEMA
3. OBJETIVOS
4. MARCO DE REFERENCIA
5. ALCANCES Y LIMITACIONES
6. METODOLOGÍA
7. VISITA DE CAMPO
8. INSPECCIÓN VISUAL DE SEGURIDAD
9. ESTUDIO DE LA ALTERNATIVA
10. DISEÑO DE LA ALTERNATIVA
11. MODELACIÓN EN PTV VISSIM 2020 VERSIÓN EDUCATIVA
12. CONCLUSIONES
BIBLIOGRAFÍA
ANEXOSPregradoIngeniero Civi
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