Macroscopic Conditions Research Articles

Evaporation boundary conditions for the R13 equations of rarefied gas dynamics

The regularized 13 moment (R13) equations are a macroscopic model for the description of rarefied gas flows in the transition regime. The equations have been shown to give meaningful results for Knudsen numbers up to about 0.5. Here, their range of applicability is extended by deriving and testing boundary conditions for evaporating and condensing interfaces. The macroscopic interface conditions are derived from the microscopic interface conditions of kinetic theory. Tests include evaporation into a half-space and evaporation/condensation of a vapor between two liquid surfaces of different temperatures. Comparison indicates that overall the R13 equations agree better with microscopic solutions than classical hydrodynamics.

Patología pulmonar en ovinos faenados del norte del departamento de Bolívar, Colombia

El objetivo principal del estudio fue describir las lesiones pulmonares en ovinos faenados. Se realizó un estudio descriptivo transversal que incluyó 26 pulmones de ovinos faenados sin signos clínicos de la enfermedad, en el norte del departamento de Bolívar, Colombia. Se estableció la frecuencia relativa de las lesiones pulmonares macroscópicas y microscópicas, así como la asociación entre las lesiones macroscópicas y la condición corporal. El 92 % de ovinos presentó lesiones macroscópicas y microscópicas. Se encontraron 32 lesiones macroscópicas: pleuritis (34 %), neumonía intersticial (32 %), neumonía embólica (13 %), neumonía granulomatosa (6 %), bula enfisematosa (6 %), neumonía verminosa (3 %), bronconeumonía supurativa (3 %) y atelectasia (3 %). La pleuritis mostró una relación altamente significativa con la condición corporal (p <0,01). Se observaron 41 lesiones microscópicas, agrupadas en disturbios inflamatorios (63 %), disturbios de insuflación que son enfisema y atelectasia (7 %), trastornos del crecimiento celular (22 %) y disturbios de la microcirculación (8 %). En cuanto a la cronicidad de las lesiones microscópicas, se encontraron lesiones agudas (29 %), subagudas (32 %), crónicas (37 %) y crónicas activas (2 %). La mayoría de casos presentados del complejo respiratorio es de tipo subclínico, por tanto, es necesario fortalecer el uso de medidas de diagnóstico y control para reducir la tasa de infección y las pérdidas económicas.

Voluntary monitoring systems for pig health and welfare in the UK: Comparative analysis of prevalence and temporal patterns of selected non-respiratory post mortem conditions

Collection of abattoir data related to public health is common worldwide. Standardised on-going programmes that collect information from abattoirs that inform producers about the presence and frequency of disease that are important to them rather than public health hazards are less common. The three voluntary pig health schemes, implemented in the United Kingdom, are integrated systems which capture information on different macroscopic disease conditions detected in slaughtered pigs. Many of these conditions have been associated with a reduction in performance traits and consequent increases in production costs. The schemes are the Wholesome Pigs Scotland in Scotland, the British Pig Health Scheme in England and Wales and the Pig Regen Ltd. health and welfare checks in Northern Ireland. In this study, four post mortem conditions (pericarditis, milk spots, papular dermatitis and tail damage) were surveyed and analysed over a ten and half year period, with the aim to compare the prevalence, monthly variations, and yearly trends between schemes. Liver milk spot was the most frequently recorded condition while tail damage was the least frequently observed condition. The prevalence of papular dermatitis was relatively low compared to liver milk spot and pericarditis in the three schemes. A general decreasing trend was observed for milk spots and papular dermatitis for all three schemes. The prevalence of pericarditis increased in Northern Ireland and England and Wales; while Scotland in recent years showed a decreasing trend. An increasing trend of tail damage was depicted in Scotland and Northern Ireland until 2013/2014 followed by a decline in recent years compared to that of England and Wales with a decreasing trend over the full study period. Monthly effects were more evident for milk spots and papular dermatitis. Similarity of the modus operandi of the schemes made the comparison of temporal variations and patterns in gross pathology between countries possible over time, especially between countries with similar pig production profile. This study of temporal patterns enables early detection of prevalence increases and alerts industry and researchers to investigate the reasons behind such changes. These schemes are, therefore, valuable assets for endemic disease surveillance, early warning for emerging disease and also for monitoring of welfare outcomes.

Finding Hama: On the Identification of a Forgotten Queen Buried in the Nimrud Tombs

Finding Hama: On the Identification of a Forgotten Queen Buried in the Nimrud Tombs

Predicting solvation free energies and thermodynamics in polar solvents and mixtures using a solvation-layer interface condition

We demonstrate that with two small modifications, the popular dielectric continuum model is capable of predicting, with high accuracy, ion solvation thermodynamics (Gibbs free energies, entropies, and heat capacities) in numerous polar solvents. We are also able to predict ion solvation free energies in water–co-solvent mixtures over available concentration series. The first modification to the classical dielectric Poisson model is a perturbation of the macroscopic dielectric-flux interface condition at the solute–solvent interface: we add a nonlinear function of the local electric field, giving what we have called a solvation-layer interface condition (SLIC). The second modification is including the microscopic interface potential (static potential) in our model. We show that the resulting model exhibits high accuracy without the need for fitting solute atom radii in a state-dependent fashion. Compared to experimental results in nine water–co-solvent mixtures, SLIC predicts transfer free energies to within 2.5 kJ/mol. The co-solvents include both protic and aprotic species, as well as biologically relevant denaturants such as urea and dimethylformamide. Furthermore, our results indicate that the interface potential is essential to reproduce entropies and heat capacities. These and previous tests of the SLIC model indicate that it is a promising dielectric continuum model for accurate predictions in a wide range of conditions.

Advances in fog microphysics research in China

Fog microphysical research in China based on field experiments obtained many important results in recent 50 years. With the fast development of China’s economy, urbanization in the last 30 years, special features of fog microphysical structure also appeared, which did not appear in other countries. This article reviews the fog microphysical research around China, and introduces the effect of urbanization on fog microphysical structure and the microphysical processes as well as macroscopic conditions of radiation fog droplet spectral broadening. Urbanization led to an increase in fog droplet number concentration but decreases in fog liquid water content (LWC) and fog droplet size, as well as a decrease in visibility in large cities. Observations show that the radiation fog could be divided into wide-spectrum one, which is all extremely dense fog with the spectral width more than 40 μm, and narrow-spectrum one, most of which is dense fog with the spectral width less than 22 μm, according to droplet spectral distribution. During developing from dense fog to extremely dense fog, the widespectrum radiation fog is characterized by explosive deepening, that is, within a very short time (about 30 min), the droplet concentration increase by about one order of magnitude, droplet spectral broadening across 20 μm, generally up to 30-40 μm, or even 50 μm. As a result, water content increased obviously, visibility decreased to less than 50 m, when dense fog became extremely dense fog.

Transparent anisotropy for the relaxed micromorphic model: Macroscopic consistency conditions and long wave length asymptotics

In this paper, we study the anisotropy classes of the fourth order elastic tensors of the relaxed micromorphic model, also introducing their second order counterpart by using a Voigt-type vector notation. In strong contrast with the usual micromorphic theories, in our relaxed micromorphic model only classical elasticity-tensors with at most 21 independent components are studied together with rotational coupling tensors with at most 6 independent components. We show that in the limit case Lc → 0 (which corresponds to considering very large specimens of a microstructured metamaterial) the meso- and micro-coefficients of the relaxed model can be put in direct relation with the macroscopic stiffness of the medium via a fundamental homogenization formula. We also show that a similar homogenization formula is not possible in the case of the standard Mindlin-Eringen-format of the anisotropic micromorphic model. Our results allow us to forecast the successful short term application of the relaxed micromorphic model to the characterization of anisotropic mechanical metamaterials.

A Monte Carlo Algorithm for Immiscible Two-Phase Flow in Porous Media

We present a Markov Chain Monte Carlo algorithm based on the Metropolis algorithm for simulation of the flow of two immiscible fluids in a porous medium under macroscopic steady-state conditions using a dynamical pore network model that tracks the motion of the fluid interfaces. The Monte Carlo algorithm is based on the configuration probability, where a configuration is defined by the positions of all fluid interfaces. We show that the configuration probability is proportional to the inverse of the flow rate. Using a two-dimensional network, advancing the interfaces using time integration, the computational time scales as the linear system size to the fourth power, whereas the Monte Carlo computational time scales as the linear size to the second power. We discuss the strengths and the weaknesses of the algorithm.

High order harmonic generation from SF6: Deconvolution of macroscopic effects.

We measure high order harmonics from the molecule SF6 over a large range of phase matching conditions and observe several features in the harmonics that are largely independent of such macroscopic conditions. The experimental data are then compared to the quantitative rescattering theory for the generation of harmonics from three orbitals. With this comparison, we are able to assign spectroscopic features in the harmonics to contributions from 1t1g (HOMO) and 5t1u (HOMO-1) orbitals.

Optimal generation of spatially coherent soft X-ray isolated attosecond pulses in a gas-filled waveguide using two-color synthesized laser pulses.

We numerically demonstrate the generation of intense, low-divergence soft X-ray isolated attosecond pulses in a gas-filled hollow waveguide using synthesized few-cycle two-color laser waveforms. The waveform is a superposition of a fundamental and its second harmonic optimized such that highest harmonic yields are emitted from each atom. We then optimize the gas pressure and the length and radius of the waveguide such that bright coherent high-order harmonics with angular divergence smaller than 1 mrad are generated, for photon energy from the extreme ultraviolet to soft X-rays. By selecting a proper spectral range enhanced isolated attosecond pulses are generated. We study how dynamic phase matching caused by the interplay among waveguide mode, neutral atomic dispersion, and plasma effect is achieved at the optimal macroscopic conditions, by performing time-frequency analysis and by analyzing the evolution of the driving laser’s electric field during the propagation. Our results, when combined with the on-going push of high-repetition-rate lasers (sub- to few MHz’s) may eventually lead to the generation of high-flux, low-divergence soft X-ray tabletop isolated attosecond pulses for applications.

Modeling of grain refinement and mechanical response of microalloyed steel wires severely deformed by combined forming process

Recently developed accumulative angular drawing (AAD) combined with wire drawing (WD) and wire flattening (WF) processes were employed to effectively induce severe plastic deformation (SPD) effects into drawn wires. The influence of combined effects of area reduction, bending, shearing, and burnishing on the accumulated deformation energy and microstructural inhomogeneities in the microalloyed steel (b.c.c.) wires has been discussed with respect to possibilities of formation of ultrafine-grained and multilayered structures in subsequently drawn and flattened wires. However, the main challenge in the present study was to support and extend experimental research on hardening mechanisms and inhomogeneous deformation energy accumulation during investigated combined forming process by numerical simulation. One of the efficient solutions to that task is development of multiscale numerical model based on digital material representation (DMR) concept, capable of explicit recreation of microstructure morphology of investigated materials as well as its further evolution with respect to complex macroscopic processing conditions. As an outcome, it was demonstrated that the presence of precipitates in the severally deformed and inhomogeneous ferrite can be not only the key factor in strengthening process but can also directly influence the grain refining process. The presented study provides a set of evidence and inspiration for introducing the controlled inhomogeneity of deformation as a tool to produce advanced structural materials.

Macroscopic network properties and short-term dynamic simulations in coastal ecological systems at Fildes Bay (King George Island, Antarctica)

A trophic mass-balanced of the benthic/pelagic system dominated by large brown macroalgae in Fildes Bay (Antarctica) was constructed by integrating biomass, production, food spectrum, and consumption related information. The resulting trophic model was used to determine the macroscopic (emergent) properties, overall health and propagation of dynamical higher order effects within this complex Antarctic ecological system in response to simulated impacts. The magnitude of the Relative Ascendency, Relative Overhead, and Redundancy values indicates that the coastal benthic/pelagic Fildes Bay system is likely to remain less developed and therefore more resistant to perturbations than other ecological systems dominated by brown macroalgae. In terms of model component contributions to the Ascendency, detritus accounted for ∼33% of the value, followed by the phyto-zooplankton complex (∼26%), macroalgae (∼19%), filter-feeders (∼7%), small epifauna (5%), and top predators (2%). Short-term or transient Ecosim dynamical responses to increase the total mortality of each model component-given mixed and top-down vulnerabilities-revealed that changes in macroalgae levels had a limited impact on the other components of the system. The filter feeder, small epifauna and benthic fishés functional groups had the greatest effects on the remaining Fildes Bay system components. The magnitude of the System Recovery Time indicated that the Nacella concinna and small epifauna components would take the longest time to return to their initial state. Based on the outcomes obtained from the model, we suggest that this preliminary trophic model, including simulated impacts, provides promising possibilities for the determination of macroscopic baseline conditions and the most sensitive components of the Fildes Bay ecological system.

Three‐dimensional modeling of high‐latitude scintillation observations

AbstractGlobal Navigation Satellite System signals exhibit rapid fluctuations at high and low latitudes as a consequence of propagation through drifting ionospheric irregularities. We focus on the high‐latitude scintillation problem, taking advantage of a conjunction of European Incoherent Scatter Radar (EISCAT) observations and a GPS scintillation monitor viewing the same line of sight. Just after 20:00 UT on 17 October 2013, an auroral E region ionization enhancement occurred with associated phase scintillations. This investigation uses the scintillation observations to estimate the ionospheric electron density distribution beyond the spatial resolution of EISCAT (5–15 km along the line of sight in this case). Following the approach of Deshpande et al. (2014), signal propagation is modeled through a specified density distribution. A multiple phase screen propagation algorithm is applied to irregularities conforming to the description of Costa and Kelley (1977) and constrained to match the macroscopic conditions observed by EISCAT. A 50‐member ensemble of modeled outputs is approximately consistent with the observations according to the standard deviation of the phase (σp). The observations have σp = 0.23 rad, while the ensemble of modeled realizations has σp = 0.23 + 0.04–0.04. By comparison of the model output with the scintillation observations, we show that the density fluctuations cannot be a constant fraction of the mean density. The model indicates that E region density fluctuations whose standard deviation varies temporally between 5 and 25% of the mean (EISCAT‐observed) density are required to explain the observed phase scintillations.

Thermal boundary conditions in sliding contact problem

If two rough surfaces slide against each other, the typical contact event is a transient interaction of a pair of asperities. A recent finite element solution of the heat conduction through such a contact is used to develop an expression for the heat transferred between the bodies as a function of the surface statistics, the nominal contact pressure and the sliding speed. Simple curve fits are provided to permit these results to be implemented as a macroscopic heat transfer condition in numerical simulations.

Generalising the mean spherical approximation as a multiscale, nonlinear boundary condition at the solute–solvent interface

ABSTRACTIn this paper, we extend the familiar continuum electrostatic model to incorporate finite-size effects in the solvation layer, by perturbing the usual macroscopic interface condition. The perturbation is based on the mean spherical approximation (MSA), to derive a multiscale solvation-layer interface condition (SLIC/MSA). We show that SLIC/MSA reproduces MSA predictions for Born ions in a variety of polar solvents, including water as well as other protic and aprotic solvents. Importantly, the SLIC/MSA model predicts not only solvation free energies accurately but also solvation entropies, which standard continuum electrostatic models fail to predict. The SLIC/MSA model depends only on the normal electric field at the dielectric boundary, similar to our recent development of a SLIC model for charge-sign hydration asymmetry, and the reformulation of the MSA as an effective boundary condition enables its straightforward application to complex molecules such as proteins, whereas traditionally it is primarily a bulk theory. This work also opens the possibility for other electrolyte models to be incorporated into fast implicit-solvent models of biomolecular electrostatics.

Statistical evaluation of AC corona images in long-time scale and characterization of short-gap leader

Although the image of discharge in the nanosecond time scale can provide some details of a single discharge, the essence of gas discharge remains random under the same macroscopic physical conditions. Therefore, the statistical evaluation of discharge images including a large number of stochastic processes in a long-time scale is still of great significance. In this paper, a digital image processing method presented in our previously paper is used to research the statistic indicators of AC corona discharge image in the time scale of seconds, and the axial distribution of the average gray level and the gray level standard deviation about corona discharge image are determined. Then, these statistical indicators are utilized to study the long brush-like corona, and a clear �stem� caused by the point electrode and not by the ball head electrode was found, even if they all belong to the highly non uniform electric field. Considering its corresponding current pulse rise time, we believe that the leader discharge also exists in the cm-level short gap. These results indicate that the statistical analysis on the longtime scales can be used in discharge research, and further image information mining will likely be used to provide some new characteristic parameters.

Recent progress towards a physics-based understanding of the H-mode transition

Results from recent experiment and numerical simulation point towards a picture of the L-H transition in which edge shear flows interacting with edge turbulence create the conditions needed to produce a non-zero turbulent Reynolds stress at and just inside the LCFS during L-mode discharges. This stress acts to reinforce the shear flow at this location and the flow drive gets stronger as heating is increased. The L-H transition ensues when the rate of work done by this stress is strong enough to drive the shear flow to large values, which then grows at the expense of the turbulence intensity. The drop in turbulence intensity momentarily reduces the heat flux across the magnetic flux surface, which then allows the edge plasma pressure gradient to build. A sufficiently strong ion pressure gradient then locks in the H-mode state. These results are in general agreement with previously published reduced 0D and 1D predator prey models. An extended predator–prey model including separate ion and electron heat channels yields a non-monotonic power threshold dependence on plasma density provided that the fraction of heat deposited on the ions increases with plasma density. Possible mechanisms to explain other macroscopic transition threshold criteria are identified. A number of open questions and unexplained observations are identified, and must be addressed and resolved in order to build a physics-based model that can yield predictions of the macroscopic conditions needed for accessing H-mode.

On the wettability transparency of graphene-coated silicon surfaces.

In order to better understand the behavior and governing characteristics of the wetting transparency phenomenon observed in graphene-coated surfaces, molecular dynamics simulations were coupled with a theoretical model. Graphene-coated silicon was selected for this analysis, due to potential applications of hybrid silicon-graphene materials as detectors in aqueous environments. The results indicate good agreement between the theory and simulations at the macroscopic conditions required to observe wetting transparency. A microscopic analysis was also conducted in order to identify the parameters, such as the interaction potential energy landscape and the interfacial liquid structure that govern the wetting behavior of graphene-coated surfaces. The interfacial liquid structure was found to be different between uncoated Si(100) and the graphene-coated version and very similar between uncoated Si(111) and the graphene-coated version. However, the concentration of liquid particles for both silicon surfaces was found to be very similar under transparent wetting conditions.

Predicting Atmospheric Attenuation Under Pristine Conditions Between 0.1 and 100 THz

This multidisciplinary paper reports on a research application-led study for predicting atmospheric attenuation, and tries to bridge the knowledge gap between applied engineering and atmospheric sciences. As a useful comparative baseline, this paper focuses specifically on atmospheric attenuation under pristine conditions, over the extended terahertz spectrum. Three well-known simulation software packages (`HITRAN on the Web', MODTRAN ® 4, and LBLRTM) are compared and contrasted. Techniques used for modeling atmospheric attenuation have been applied to investigate the resilience of (ultra-)wide fractional bandwidth applications to the effects of molecular absorption. Two extreme modeling scenarios are investigated: horizontal path links at sea level and Earth-space path links. It is shown by example that a basic software package (`HITRAN on the Web') can give good predictions with the former, whereas sophisticated simulation software (LBLRTM) is required for the latter. Finally, with molecular emission included, carrier-to-noise ratio fade margins can be calculated for the effects of line broadening due to changes in macroscopic atmospheric conditions with sub-1-THz ultra-narrow fractional bandwidth applications. Outdoors can be far from pristine, with additional atmospheric contributions only briefly introduced here; further discussion is beyond the scope of this paper, but relevant references have been cited.

我国林业遥感研究现状与展望

通过对20多年来遥感技术在我国林业实践中的应用回顾与总结，指出随着遥感技术的发展和应用水平的逐步提高，我国林业遥感已从过去的森林资源数量清查和分类应用逐渐转向森林生态环境调查与评价，森林生态系统健康监测，森林生物物理和生化参数的提取分析等领域，并对我国林业遥感研究前景进行预测。作者认为未来中国林业遥感发展的主要方向是：1) 包容各种新技术，形成新的技术体系，并与国际接轨；2) 利用遥感的优势，研究森林的宏观状况与作用；3) 与森林经营进一步结合。 With the retrospection of the application of remote sensing technology in forestry practice over 20 years, the paper showed that our country’s application of remote sensing had turned from forest investigation and classification to forest environment investigation, forest ecosystem health monitoring, forest biophysical and biochemical parameter inversion, along with the development of remote sensing technology and application. The paper predicted the future of our country’s forestry remote sensing in the end. In the light of the mentioned above, the forest remote sensing perspective of the 21st century in China was predicted. The author put forward to the main developing directions on forest remote sensing of the next century in China, 1) to include all kinds of new technology and form new technology system and join up with international; 2) to study the macroscopic conditions and functions through utilizing the superiority of the remote sensing; 3) to integrate with the forest management.