641 research outputs found
On-chip electrically controlled routing of photons from a single quantum dot
Electrical control of on-chip routing of photons emitted by a single InAs/GaAs self-assembled quantum dot (SAQD) is demonstrated in a photonic crystal cavity-waveguide system. The SAQD is located inside an H1 cavity, which is coupled to two photonic crystal waveguides. The SAQD emission wavelength is electrically tunable by the quantum-confined Stark effect. When the SAQD emission is brought into resonance with one of two H1 cavity modes, it is preferentially routed to the waveguide to which that mode is selectively coupled. This proof of concept provides the basis for scalable, low-power, high-speed operation of single-photon routers for use in integrated quantum photonic circuits
The sediment of mixtures of charged colloids: segregation and inhomogeneous electric fields
We theoretically study sedimentation-diffusion equilibrium of dilute binary,
ternary, and polydisperse mixtures of colloidal particles with different
buoyant masses and/or charges. We focus on the low-salt regime, where the
entropy of the screening ions drives spontaneous charge separation and the
formation of an inhomogeneous macroscopic electric field. The resulting
electric force lifts the colloids against gravity, yielding highly
nonbarometric and even nonmonotonic colloidal density profiles. The most
profound effect is the phenomenon of segregation into layers of colloids with
equal mass-per-charge, including the possibility that heavy colloidal species
float onto lighter ones
Resting vs. active: a meta-analysis of the intra- and inter-specific associations between minimum, sustained, and maximum metabolic rates in vertebrates
Variation in aerobic capacity has far reaching consequences for the physiology, ecology, and evolution of vertebrates. Whether at rest or active, animals are constrained to operate within the energetic bounds determined by their minimum (minMR) and sustained or maximum metabolic rates (upperMR). MinMR and upperMR can differ considerably among individuals and species but are often presumed to be mechanistically linked to one another. Specifically, minMR is thought to reflect the idling cost of the machinery needed to support upperMR. However, previous analyses based on limited datasets have come to conflicting conclusions regarding the generality and strength of their association.
Here we conduct the first comprehensive assessment of their relationship, based on a large number of published estimates of both the intra-specific (n = 176) and inter-specific (n = 41) phenotypic correlations between minMR and upperMR, estimated as either exercise-induced maximum metabolic rate (VO2max), cold-induced summit metabolic rate (Msum), or daily energy expenditure (DEE).
Our meta-analysis shows that there is a general positive association between minMR and upperMR that is shared among vertebrate taxonomic classes. However, there was stronger evidence for intra-specific correlations between minMR and Msum and between minMR and DEE than there was for a correlation between minMR and VO2max across different taxa. As expected, inter-specific correlation estimates were consistently higher than intra-specific estimates across all traits and vertebrate classes.
An interesting exception to this general trend was observed in mammals, which contrast with birds and exhibit no correlation between minMR and Msum. We speculate that this is due to the evolution and recruitment of brown fat as a thermogenic tissue, which illustrates how some species and lineages might circumvent this seemingly general association.
We conclude that, in spite of some variability across taxa and traits, the contention that minMR and upperMR are positively correlated generally holds true both within and across vertebrate species. Ecological and comparative studies should therefore take into consideration the possibility that variation in any one of these traits might partly reflect correlated responses to selection on other metabolic parameters
Extended sedimentation profiles in charged colloids: the gravitational length, entropy, and electrostatics
We have measured equilibrium sedimentation profiles in a colloidal model
system with confocal microscopy. By tuning the interactions, we have determined
the gravitational length in the limit of hard-sphere-like interactions, and
using the same particles, tested a recent theory [R.van Roij, J. Phys. Cond.
Mat. 15, S3569, (2003)], which predicts a significantly extended sedimentation
profile in the case of charged colloids with long-ranged repulsions, due to a
spontaneously formed macroscopic electric field. For the hard-sphere-like
system we find that the gravitational length matches that expected. By tuning
the buoyancy of the colloidal particles we have shown that a mean field
hydrostatic equilibrium description even appears to hold in the case that the
colloid volume fraction changes significantly on the length scale of the
particle size. The extended sedimentation profiles of the colloids with
long-ranged repulsions are well-described by theory. Surprisingly, the theory
even seems to hold at concentrations where interactions between the colloids,
which are not modeled explicitly, play a considerable role
NOX AND VOC MEASUREMENTS AND HEALTH RISK ASSESSMENT IN AN INFORMAL SETTLEMENT IN DURBAN
A previous study by Muller et al. (2003) investigated NOx, benzene, toluene, ethylbenzene and xylene levels in households in the densely settled informal settlement of Cato Crest located within the Durban Metropolitan area. AHealth Risk Assessment based on the United States EPA approach showed that the residents of Cato Crest experienced significant health risks as a result of exposure to these pollutants largely as a result of kerosene usage in their homes. Specifically, the study which was conducted in September 2000 in 14 households, showed that exposure to NOx over a 24-hour period indicated a potential health risk in all the households, that benzene poses a health risk in 50% of the households, whereas there is no health risk associated with exposure to toluene. A follow-up study was conducted in July 2006 targeting similar households and pollutants to investigate whether comparable results were found in a typical winter period, when air quality is generally expected to deteriorate
Sedimentation of binary mixtures of like- and oppositely charged colloids: the primitive model or effective pair potentials?
We study sedimentation equilibrium of low-salt suspensions of binary mixtures
of charged colloids, both by Monte Carlo simulations of an effective
colloids-only system and by Poisson-Boltzmann theory of a colloid-ion mixture.
We show that the theoretically predicted lifting and layering effect, which
involves the entropy of the screening ions and a spontaneous macroscopic
electric field [J. Zwanikken and R. van Roij, Europhys. Lett. {\bf 71}, 480
(2005)], can also be understood on the basis of an effective colloid-only
system with pairwise screened-Coulomb interactions. We consider, by theory and
by simulation, both repelling like-charged colloids and attracting oppositely
charged colloids, and we find a re-entrant lifting and layering phenomenon when
the charge ratio of the colloids varies from large positive through zero to
large negative values
Dynamical density functional theory for dense atomic liquids
Starting from Newton's equations of motion, we derive a dynamical density
functional theory (DDFT) applicable to atomic liquids. The theory has the
feature that it requires as input the Helmholtz free energy functional from
equilibrium density functional theory. This means that, given a reliable
equilibrium free energy functional, the correct equilibrium fluid density
profile is guaranteed. We show that when the isothermal compressibility is
small, the DDFT generates the correct value for the speed of sound in a dense
liquid. We also interpret the theory as a dynamical equation for a coarse
grained fluid density and show that the theory can be used (making further
approximations) to derive the standard mode coupling theory that is used to
describe the glass transition. The present theory should provide a useful
starting point for describing the dynamics of inhomogeneous atomic fluids.Comment: 14 pages, accepted for publication in J. Phys.: Condens. Matte
Π‘ΠΈΡΡΠ΅ΠΌΠ° Π°Π²ΡΠΎΠΌΠ°ΡΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΠ΅ΡΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΠ»Π΅ΠΊΡΡΠΎΠ°Π²ΡΠΎΠΌΠ°ΡΠΈΠΊΠΈ Π³Π°Π·ΠΎΠΏΡΠΎΠ²ΠΎΠ΄Π° Β«Π‘Π°Ρ Π°Π»ΠΈΠ½ βΠ₯Π°Π±Π°ΡΠΎΠ²ΡΠΊ-ΠΠ»Π°Π΄ΠΈΠ²ΠΎΡΡΠΎΠΊΒ»
Π Π΄Π°Π½Π½ΠΎΠΌ ΠΏΡΠΎΠ΅ΠΊΡΠ΅ Π±ΡΠ»Π° ΡΠ°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π° ΡΠΈΡΡΠ΅ΠΌΠ° ΠΊΠΎΠ½ΡΡΠΎΠ»Ρ ΠΈ ΡΠΏΡΠ°Π²Π»Π΅Π½ΠΈΡ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠΌ ΠΏΡΠΎΡΠ΅ΡΡΠΎΠΌ Π½Π° Π±Π°Π·Π΅ ΠΏΡΠΎΠΌΡΡΠ»Π΅Π½Π½ΡΡ
ΠΊΠΎΠ½ΡΡΠΎΠ»Π»Π΅ΡΠΎΠ² Schneider Electric Modicon 258, Ρ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ΠΌ SCADAβΡΠΈΡΡΠ΅ΠΌΡ Infinity. Π¦Π΅Π»Ρ ΡΠ°Π±ΠΎΡΡ β ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π°Π²ΡΠΎΠΌΠ°ΡΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ ΡΠΏΡΠ°Π²Π»Π΅Π½ΠΈΡ ΡΠ·Π»Π° ΠΎΡΠΈΡΡΠΊΠΈ ΠΈ ΡΠ±ΠΎΡΠ° ΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠ° Π½Π° ΠΠ Π‘ Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΠΠΠ, Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ Π²ΡΠ±ΡΠ°Π½Π½ΠΎΠΉ SCADAβΡΠΈΡΡΠ΅ΠΌΡ. ΠΠ±ΡΠ΅ΠΊΡΠΎΠΌ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΡΠ²Π»ΡΠ΅ΡΡΡ ΡΠ·Π΅Π» ΠΎΡΠΈΡΡΠΊΠΈ ΠΈ ΡΠ±ΠΎΡΠ° ΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠ° Π½Π° ΠΠ Π‘. Π Π°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π½Π°Ρ ΡΠΈΡΡΠ΅ΠΌΠ° ΠΌΠΎΠΆΠ΅Ρ ΠΏΡΠΈΠΌΠ΅Π½ΡΡΡΡΡ Π² ΡΠΈΡΡΠ΅ΠΌΠ°Ρ
ΠΊΠΎΠ½ΡΡΠΎΠ»Ρ, ΡΠΏΡΠ°Π²Π»Π΅Π½ΠΈΡ ΠΈ ΡΠ±ΠΎΡΠ° Π΄Π°Π½Π½ΡΡ
Π½Π° ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΠΏΡΠΎΠΌΡΡΠ»Π΅Π½Π½ΡΡ
ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΡΡ
. ΠΠ°Π½Π½Π°Ρ ΡΠΈΡΡΠ΅ΠΌΠ° ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΡ ΡΠ²Π΅Π»ΠΈΡΠΈΡΡ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΡΠ΅Π»ΡΠ½ΠΎΡΡΡ, ΠΏΠΎΠ²ΡΡΠΈΡΡ ΡΠΎΡΠ½ΠΎΡΡΡ ΠΈ Π½Π°Π΄Π΅ΠΆΠ½ΠΎΡΡΡ ΠΈΠ·ΠΌΠ΅ΡΠ΅Π½ΠΈΠΉ, ΡΠΎΠΊΡΠ°ΡΠΈΡΡ ΡΠΈΡΠ»ΠΎ Π°Π²Π°ΡΠΈΠΉ. Π Π°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π° ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»ΡΠ½Π°Ρ ΡΡ
Π΅ΠΌΠ° Π°Π²ΡΠΎΠΌΠ°ΡΠΈΠ·Π°ΡΠΈΠΈ, ΡΡΡΡΠΊΡΡΡΠ½Π°Ρ ΡΡ
Π΅ΠΌΠ°, Π°Π»Π³ΠΎΡΠΈΡΠΌΡ ΡΠΏΡΠ°Π²Π»Π΅Π½ΠΈΡ.This project has been developed a process monitoring and control system based on industrial controllers of Schneider Electric Modicon 258, with Infinity SCADA-system. The purpose of work - designing automated cleaning unit management system and the condensate collecting in the GDS using the PLC, based on the selected SCADA-system. The object of this study is to purification unit and condensate collection at GDS. The developed system can be used in control systems, data acquisition and control in different industrial plants. This system will increase productivity, improve the accuracy and reliability of the measurements, reduce the number of accidents. The project was designed automation functional diagram and a block diagram of the control algorithms
A frequentist framework of inductive reasoning
Reacting against the limitation of statistics to decision procedures, R. A.
Fisher proposed for inductive reasoning the use of the fiducial distribution, a
parameter-space distribution of epistemological probability transferred
directly from limiting relative frequencies rather than computed according to
the Bayes update rule. The proposal is developed as follows using the
confidence measure of a scalar parameter of interest. (With the restriction to
one-dimensional parameter space, a confidence measure is essentially a fiducial
probability distribution free of complications involving ancillary statistics.)
A betting game establishes a sense in which confidence measures are the only
reliable inferential probability distributions. The equality between the
probabilities encoded in a confidence measure and the coverage rates of the
corresponding confidence intervals ensures that the measure's rule for
assigning confidence levels to hypotheses is uniquely minimax in the game.
Although a confidence measure can be computed without any prior distribution,
previous knowledge can be incorporated into confidence-based reasoning. To
adjust a p-value or confidence interval for prior information, the confidence
measure from the observed data can be combined with one or more independent
confidence measures representing previous agent opinion. (The former confidence
measure may correspond to a posterior distribution with frequentist matching of
coverage probabilities.) The representation of subjective knowledge in terms of
confidence measures rather than prior probability distributions preserves
approximate frequentist validity.Comment: major revisio
The Physics of the Colloidal Glass Transition
As one increases the concentration of a colloidal suspension, the system
exhibits a dramatic increase in viscosity. Structurally, the system resembles a
liquid, yet motions within the suspension are slow enough that it can be
considered essentially frozen. This kinetic arrest is the colloidal glass
transition. For several decades, colloids have served as a valuable model
system for understanding the glass transition in molecular systems. The spatial
and temporal scales involved allow these systems to be studied by a wide
variety of experimental techniques. The focus of this review is the current
state of understanding of the colloidal glass transition. A brief introduction
is given to important experimental techniques used to study the glass
transition in colloids. We describe features of colloidal systems near and in
glassy states, including tremendous increases in viscosity and relaxation
times, dynamical heterogeneity, and ageing, among others. We also compare and
contrast the glass transition in colloids to that in molecular liquids. Other
glassy systems are briefly discussed, as well as recently developed synthesis
techniques that will keep these systems rich with interesting physics for years
to come.Comment: 56 pages, 18 figures, Revie
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