Search results for "conditions"
showing 10 items of 891 documents
Measuring the weather’s impact on MAC layer over 2.4GHz outdoor radio links
2015
The weather s impact on the performance of a radio link at the 2.4 GHz ISM (Industry, Scientific and Medical) band had not been yet studied in great detail up to now as it is generally believed that the ultra-high frequency band is not significantly affected by weather conditions. However, our study shows significant correlations between meteorological variables and control frame errors at MAC (Medium Access Control) layer of the IEEE 802.11b/g standard. This study is performed over an outdoor radio link setting which has been monitored for several months. Moreover, we check if link distance and so modulation scheme and data rate are also decisive features of such impact. Our real scenario …
Passenger Car Equivalents for Heavy Vehicles at Roundabouts. a Synthesis Review
2019
Passenger Car Equivalents (PCEs in the following) are used to transform a mixed fleet of vehicles into a fleet of equivalent passenger cars and to analyze capacity and level-of-service of roads and intersections. Most roundabouts guidelines propose constant values for PCEs but a single PCE value can result improper under heterogeneous traffic conditions. PCEs should be vary with traffic and road conditions and consequently PCEs applied to undersaturated traffic conditions can overestimate the heavy vehicle effect or be not sensitive to the traffic level or characteristics of heavy vehicles. Compared to other at-grade intersections, the interaction between the operational performances of the…
On the slabbing of stones through diamond wire cutting operations
2009
Diamond wires are usually used in the cutting operations aimed to obtain slabs of stones. This tool consists of a steel cable on which are mounted annular metal—diamond pearls. The use of this technology expanded all over the world because of its advantages on other slabbing techniques as both technical and economical aspects are considered. It should be observed that with this technology wear phenomena must be properly monitored in order to obtain the best process conditions. In this article, the diamond wire cutting operation is investigated, highlighting the process mechanics and the wear phenomena occurring in the used tools. Furthermore, a modified version of the tool itself is propos…
Theoretical Foundations of the Monte Carlo Method and Its Applications in Statistical Physics
2002
In this chapter we first introduce the basic concepts of Monte Carlo sampling, give some details on how Monte Carlo programs need to be organized, and then proceed to the interpretation and analysis of Monte Carlo results.
Graphene nanoribbons subject to gentle bends
2012
Since graphene nanoribbons are thin and flimsy, they need support. Support gives firm ground for applications, and adhesion holds ribbons flat, although not necessarily straight: ribbons with high aspect ratio are prone to bend. The effects of bending on ribbons' electronic properties, however, are unknown. Therefore, this article examines the electromechanics of planar and gently bent graphene nanoribbons. Simulations with density-functional tight-binding and revised periodic boundary conditions show that gentle bends in armchair ribbons can cause significant widening or narrowing of energy gaps. Moreover, in zigzag ribbons sizeable energy gaps can be opened due to axial symmetry breaking,…
Orthorhombic Phase of Crystalline Polyethylene: A Monte Carlo Study
1996
In this paper we present a classical Monte Carlo simulation of the orthorhombic phase of crystalline polyethylene, using an explicit atom force field with unconstrained bond lengths and angles and periodic boundary conditions. We used a recently developed algorithm which apart from standard Metropolis local moves employs also global moves consisting of displacements of the center of mass of the whole chains in all three spatial directions as well as rotations of the chains around an axis parallel to the crystallographic c-direction. Our simulations are performed in the NpT ensemble, at zero pressure, and extend over the whole range of temperatures in which the orthorhombic phase is experime…
Dilute solution rheology of flexible macromolecules (bead–rod model)
1974
The rheological behavior of dilute solutions of flexible macromolecules is studied by means of a freely jointed multiple bead–rod model. The solution of the equations describing the mechanics of the system is obtained by means of a numerical procedure, which applies to arbitrary flow conditions. The case of the transient stress in uniaxial elongational flow is developed in some detail. A comparison with bead–spring models shows both quantitative and qualitative differences which are briefly discussed.
Heterogeneous nucleation at a wall near a wetting transition: a Monte Carlo test of the classical theory
2009
While for a slightly supersaturated vapor the free energy barrier ΔF(hom)(*), which needs to be overcome in a homogeneous nucleation event, may be extremely large, nucleation is typically much easier at the walls of the container in which the vapor is located. While no nucleation barrier exists if the walls are wet, for incomplete wetting of the walls, described via a nonzero contact angle Θ, classical theory predicts that nucleation happens through sphere-cap-shaped droplets attracted to the wall, and their formation energy is ΔF(het)(*) = ΔF(hom)(*)f(Θ), with f(Θ) = (1-cosΘ)(2)(2+cosΘ)/4. This prediction is tested through simulations for the simple cubic lattice gas model with nearest-nei…
La precariedad laboral en inmigrantes en situación irregular en España y su relación con la salud
2009
ResumenObjetivoDescribir las características de la precariedad laboral en inmigrantes irregulares en España y su relación con la salud.MétodosEstudio cualitativo que utiliza los principios de la inducción analítica. Se definió una submuestra del proyecto ITSAL, cuya muestra teórica se identificó a partir de la definición de inmigrante en España y de la literatura. Las áreas de estudio fueron 4 ciudades de España. La muestra final fue de 44 trabajadores inmigrantes irregulares, de 4 nacionalidades.ResultadosAlgunas características de la precariedad laboral percibidas por los inmigrantes irregulares fueron: elevada inestabilidad laboral; ausencia total de empoderamiento en tanto no cuentan co…
Essential elements of professional nursing environments in Primary Care and their influence on the quality of care
2018
Objectives Nursing work environments (NWE) are key determinants of care quality. Our study aimed to evaluate the characteristics of nursing environments in primary care settings in the Canary Islands, and identify crucial components of such environments to improve quality. Method We conducted a cross-sectional study in primary care organisations using the Practice Environment Scale - Nursing Work Index (PES-NWI) tool. We collected sociodemographic variables, PES-NWI scores, and selected the essential items conducive to optimal care. Appropriate parametric and non-parametric statistical tests were used to analyse relations between variables (CI = 95%, error = 5%). Results 144 nurses particip…