Search

С развитием цифровизации происходит увеличение потребности в информационном обеспечении компаний. На сегодняшний день количество поставщиков информационных технологий для транспортной отрасли насчитывается огромное количество, но качество предоставляемых ими услуг не всегда высоко. В данной статье рассматриваются наиболее популярные информационные программы, которые помогают повысить уровень логистической координации транспортных процессов на предприятиях. Проанализировав описанные в тексте программы, были выявлены их функциональных возможности, направленные на улучшение логистической координации транспортных процессов, а также сформулирован вывод о качестве информационных технологий на сегодняшний день., With the development of digitalization, there is an increase in the need for information support for companies. Today, there are a huge number of information technology providers for the transport industry, but the quality of their services is not always high. This article discusses the most popular information programs that help to improve the level of logistics coordination of transport processes at enterprises. After analyzing the programs described in the text, their functional capabilities aimed at improving the logistics coordination of transport processes were identified, and a conclusion was formulated about the quality of information technologies today.

The evaluation of a new air water generator (AWG) based on absorption and reverse osmosis is described. For the evaluation, an aqueous lithium bromide solution has been selected from a wide range of liquids as the absorbent. At high salt mass fractions, the aqueous lithium bromide solution has a low vapour pressure and a high osmotic pressure. The low vapour pressure ensures that the water vapour can be absorbed from the air, but the high osmotic pressure leads to high pressures over the membrane. Due to the high osmotic pressures, several reverse osmosis membrane modules are necessary and salt solution has to be present on both sides of the membrane, which leads to an additional inlet on the permeate side. Models for the absorber, the reverse osmosis membrane module and the complete multi-stage reverse osmosis system have been developed in Python. The model of the complete system has then been used to simulate the performance of the AWG at different boundary conditions. The simulations have shown that based on the defined assumptions, extracting water from the air with absorption and reverse osmosis is possible and that the energy demand per litre of pure water is similar to AWG systems which use condensation., + ID der Publikation: hslu_82593 + Art des Beitrages: Wissenschaftliche Medien + Jahrgang: 6 + Sprache: Englisch + Letzte Aktualisierung: 2021-12-09 09:37:44

Solidifiers are dry, granular hydrophobic polymers that form physical bonds with hydrocarbons by molecular interactions (hydrogen bonding, London forces), and are used to immobilize hydrocarbon spill propagation and dispersion. CIAgent© is a non-toxic, proprietary polymer blend listed as an “Oil Solidifier” on the EPA's National Contingency Plan Product Schedule for use on hydrocarbon spills in the navigable waterways of United States. CIAgent solidifies the liquid hydrocarbons through a rapid transformation into a cohesive rubber-like inert mass upon contact and retains the liquid for easier removal and disposal. The objective of this paper is to determine the effectiveness of the solidifier with a variety of hydrocarbon liquids that could be encountered in an oil spill scenario. The effectiveness of the solidifier was characterized in terms of the application rate, temperature change, solubility parameters and solidification time for a variety of hydrocarbon liquids (e. g., gasoline, diesel fuel, crude oil) that could be encountered by measuring the heat of solidification using a solution calorimeter. A thermogram was obtained and the heat of solidification was calculated using the temperature difference upon solidification. The temperature change and the degree of swelling in the solidifier were used to determine the solubility parameter of the solidifier (6.77 Hildebrands). The heat of solidification value was used to determine the ease and speed of the solidification of the hydrocarbon liquids. Solidification times ranged from 40 to 120 s for the liquids tested. The average application ratio in weight of solidifier to weight of hydrocarbon ranged was 3.35., Chemical engineering; Environmental Chemical Engineering; Transport Process; Adsorption; Water Treatment; Environmental Hazard; Solidification; Hydrocarbon; calorimeter; polymer; spill remediation

Introduction. The article determines the relevance of the scientifically sound solutions and effective tools’ development in the evaluation of the passenger companies’ performance. The author notes that these decisions should be based on the modern methodological principles for assessing the complex systems’ performance, taking into account the specific of the transport service process and the general requirements for evaluation methods. Materials and methods. The methods and tools of the quality management system, methods of system and the methods of structural and comparative analysis are used in the research. The main approaches to the task assessing effectiveness of the complex systems’ functioning are singled out, and their shortcomings, and the possibility of their application for the evaluation of performance in the theory of passenger motor transport are determined. Results. The author proposes to use the index normalization method to develop a methodology for assessing the performance of passenger enterprises, where the whole set of carefully selected indicators in accordance with accepted standards is converted from absolute values to relative ones. In accordance with it, the tasks and stages of subsequent research are defined. The article presents the classification model of the basic system formation of performance indicators and the functional scheme of their grouping for the subsequent indicators’ ranking by significance within each of the four groups. Discussion and conclusion. The author concludes that the index rationing method could be used for urban public transportation terms. Systematized enterprises’ indicators should be ranked in order of importance, first of all for the passenger, then for the department of transport, and only then for the enterprise, because efficiency in market conditions is not only a good financial result, but also the enterprise competitiveness for the quality of services and the amount of subsidies.

International audience; This paper describes an early lumping approach for generating a mathematical model of the heating process of a moving dual-layer substrate. The heat is supplied by convection and nonlinearly distributed over the whole considered spatial extend of the substrate. Using CFD simulations as a reference, two different modelling approaches have been investigated in order to achieve the most suitable model type. It is shown that due to the possibility of using the transition matrix for time discretization, an equivalent circuit model achieves superior results when compared to the Crank-Nicolson method. In order to maintain a constant sampling time for the in-visioned-control strategies, the effect of variable speed is transformed into a system description, where the state vector has constant length but a variable number of non-zero entries. The handling of the variable transport speed during the heating process is considered as the main contribution of this work. The result is a model, suitable for being used in future control strategies.

Up-today intercity passenger transportation is needed to consider fluctuations in demand for services over time. Designated fluctuations in demand mainly linked to the onset of a period of national or religious celebrations holidays, mass vacation in summer, internal and international sports and cultural activities, ect. Therefore, these demand irregularity of using public intercity transport should be considered when managing transportation. In issue to meet the needs of passengers moving within existing fluctuations in demand can decide to change the parameters of the components of the transport system. These changes include variety in amount or type of vehicles, schedules, changes in traffic patterns routes, introduction of these routes, limiting of the passenger’s purchasing ability fares and so on. It is important to determine the passenger’s place in the social, economic or cultural development of the population overemphasized. Therefore, regulation of activity of the public transport services must satisfy the possibility of these services within acceptable financial, time and physical burden for passengers. So, component optimization efficiency of intercity passengers’ transportation should take place in harmony with the social and economic development of society. The requirements set out not to satisfy the demand of passengers to move through extra large fare, lack of communication between bus transport areas with constant correspondence, failure to comply with increasing comfort haulage transport of tiredness or lack of means of transport are unacceptable phenomena. On the one hand the importance of the social dimension in long-distance traffic route of transport. In accordance with the meaning specified the need for balanced decision-making on the management system of passenger traffic. Invention compromise between technical and economic level to meet the demand and requirements of the conservation of expenditure-revenue component transport process is a key issue. According to conditions need to take informed decisions about technical support of demand irregularity still unresolved is the issue of estimating the increasing the potential feasibility of intercity passengers transportation by changes in the quality or quantity of vehicles on existing routes or the introduction of additional temporary route network routes.

The aim of this note is to deepen the knowledge of isotropic random flights moving in mixed Poisson media; that is we analyze the random evolution of a particle with random scattering rate Λ . By assuming Λ distributed according to some standard probability laws, we are able to explicit the probability measure of the random flights. Furthermore, we show that there exists a link between our processes and a inhomogeneous wave equation.

The salt permeability through three commercial cation-exchange membranes with different morphologies is investigated in aqueous NaCl solutions. Ion-exchange membranes (IEMs) find application in different processes such as electrodialysis, reverse osmosis, diffusion dialysis, membrane electrolysis, membrane fuel cells and ion exchange bioreactors. The aim of this paper is the experimental determination of the electrolyte permeability in the following membranes: MK-40 membrane, Nafion N324 membrane and Nafion 117 membrane. The latter is selected as being a reference membrane. The effect of an increase in the NaCl concentration in the solutions on membranes transport properties is analyzed. With regard to membranes sorption, a decrease in the water content was observed when the external electrolyte concentration is increased. Concerning permeation through the membranes, the salt permeability increased with concentration for the Nafion 117 membrane and remained nearly constant for the other two membranes. A close relation between the degree of liquid sorption by the membranes and the electrolyte permeability was observed.

A new phenomenological model, based on a second order dissolution kinetics, was developed for the alkaline removal of non-collagenous protein (NCP) from the skin of Nile tilapia (SNT). This model allows estimating the liquid concentration of NCP in terms of temperature, skin size, NaOH concentration and time. This model was fitted with 135 experiments averaging a R2 of 0.99. The root-mean-square deviation and the mean-absolute-percentage error of the model were 0.0041 and 3.15%, respectively. The Arrhenius-activation energy was 15–122 kJ mol−1. Multi-objective optimization led to the highest NCP extraction (NCPE) of 24.3% and to the lowest loss of collagen (LC) of 1.3%, with R2 coefficients of 0.98 and 0.92, respectively. Ultimately, SNT deproteinized under optimal conditions was subjected to acid extraction and purification. FTIR and SEM analyses indicated that the product was a Type I collagen that could be used in the pharmaceutical industry., Chemical engineering; Dynamical system; Transport process; Materials characterization; Chemical reaction kinetics; Chemical characterization of food; Nile tilapia; Kinetics extraction; Acid-soluble collagen; Alkaline pretreatment; Modelling; Second-order model

Highly populated river deltas are experiencing marine environment degradation resulting from the tremendous input of terrestrial dissolved substances (TeDS). The Pearl River Delta is one of the deltas with degradation of the water quality and ecological condition. The Pearl River Estuary (PRE) was investigated to reveal the fate and transport timescales of TeDS in order to provide guidance on water resource management and pollutant transport prediction. By using passive tracers in a calibrated 3D numerical model, the TeDS transports from five different outlet groups were investigated systematically. The TeDS transport time was computed by using the concept of water age, which is a measure of the time that has elapsed since the tracer was transported from the upstream boundary to the downstream concerned area. The tracer impacted area was defined by the area with tracer concentrations &gt, 0.2 (arbitrary unit). The domains that were impacted by the tracer coming from each outlet group were identified separately. In the wet season, the impacted area was larger than in other seasons. The most prominent variations appeared in the Jiaomen&ndash, Hengmen&ndash, Hongqili (JHH) and Modaomen (MD) outlets. The hydrodynamic conditions controlled the offshore spreading of the TeDS. Assuming the TeDS were conservative, it took approximately 10&ndash, 20 days for the TeDS to be transported from the head water to the entrance of the outlet. For the TeDS coming from the head water of the Humen outlet, it took approximately 40 (80) days for the TeDS to be transported out of the mouth of the Lingding Bay during the wet (dry) season. For the case of the TeDS coming from the head water of the JHH outlets, it took approximately 20 (40) days for the TeDS to be transported out of the Lingding Bay during the wet (dry) season. For the MD, Jiti and Yamen&ndash, Hutiao outlets, it usually took approximately 10 days for the TeDS to be transported from the head water to the inner shelf. The correlation coefficient between the river flow and tracer concentrations was 0.78, and between the river flow and transport time it was &minus, 0.70 at a station in the lower Lingding Bay. At the estuary mouth, the impacts of other forcing fields got stronger.

We show a relation between fractional calculus and fractals, based only on physical and geometrical considerations. The link has been found in the physical origins of the power-laws, ruling the evolution of many natural phenomena, whose long memory and hereditary properties are mathematically modelled by differential operators of non integer order. Dealing with the relevant example of a viscous fluid seeping through a fractal shaped porous medium, we show that, once a physical phenomenon or process takes place on an underlying fractal geometry, then a power-law naturally comes up in ruling its evolution, whose order is related to the anomalous dimension of such geometry, as well as to the model used to describe the physics involved. By linearizing the non linear dependence of the response of the system at hand to a proper forcing action then, exploiting the Boltzmann superposition principle, a fractional differential equation is found, describing the dynamics of the system itself. The order of such equation is again related to the anomalous dimension of the underlying geometry., Comment: 23 pages, 6 figures

This paper develops a mathematical model to quantify the market share of given freight transport corridor. By analysing the whole process of door to door freight transport, the generalized cost model of railway and highway is established, respectively. A case study of long-distance transport in China's inland cities is subsequently conducted to explore market share of railway and highway. At last, the sensitivity of influence factors is analysed. We find that the average train speed, waiting time to be loaded, container volume and transport distance can significant affect the railway market share. The railway market share increases as the average train speed, container volume and transport distance increase, while decreases as the time waiting to be loaded increases. When the average trains speed is over 50 km/h, or the time waiting to be loaded is less than 1.5 d, railway market share is over 50%. Moreover, railway is more competitive in high capacity and long-distance freight transport. We also find that the result of single factor's change is limit, while the change of multi-factors can affect the railway market share greatly.

The highest population of Calophyllum inophyllum is in Indonesia. One of the bioactive compound contained in C. inophyllum leave is cholestane. The extraction method was employed to obtain crude extract from these leaves. It was followed by identification of the bioactive compounds. The purpose of this research was to develop a process for isolating and identifying cholestane and dihydropyrene from methanolic extract of C. inophyllum leaves in high yield and purity. The effect of crude extract to non-polar solvent mass ratio and non-polar solvent types on the separation of the bioactive compounds were also systematically investigated. New compounds (trans-2-[2-(trifluoromethyl)phenyl]-10b,10c-dimethyl-10b, 10c-dihydropyrene and anti-4-aza-B-homo-5.alpha-cholestane-3-one) were also identified in C. inophyllum leaves. The successful separation was obtained by employing CS2 as the solvent and crude extract to CS2 mass ratio of 1/10 (g/g)., Chemical engineering; Biochemical engineering; Pharmaceutical engineering; Transport process; Industrial chemistry; Materials characterization; Calophyllum inophyllum leaves; Extraction; Separation; Solvent.

Analysis of ‘entropy generation’ is an important strategy to build, optimize and operate the heat exchange systems within their maximum operating efficiency. Porous rhombic cavities with various inclination angles, φ and various thermal aspect ratios, A, have been considered for the numerical investigation of thermal processing of various fluids (Prandtl number, Pr = 0.015 and 1000) in the range of Darcy number (Da = 10−3–10) due to its extensive energy related applications. The effect of A and φ for various governing parameters during convection are discussed in detail via heat transfer irreversibility (Sθ) and fluid friction irreversibility, Sψ. At lower A, the entropy generation in the cavity is dominated by both Sθ and Sψ for all φs irrespective of Da and Pr. As A increases, Sθ as well as Sψ decreases for all φs which in turn decreases Stotal with A irrespective of Da and Pr. The total entropy generation (Stotal) is found to be lower for φ = 30° and higher for φ = 75° for all Pr and Da. Analysis of variations of Beav with A for higher Da (Da = 10) indicates that, entropy generation is highly fluid friction dominant irrespective of φ and A. Lesser entropy generation (Stotal) with larger heat transfer rate ( Nu b ¯ ) and reasonable heat transfer rate ( Nu b ¯ ) occurs for Pr = 0.015 and Pr = 1000, respectively at φ = 30° cavities with all A irrespective of Da. Current work attempts to analyze energy efficient thermal convection strategies and role of thermal aspect ratio within porous rhombic enclosures based on entropy generation minimization vs heat transfer rates for various fluids.

We study the evacuation dynamics of a crowd evacuating from a complex geometry in the presence of a fire as well as of a slowly spreading smoke curtain.The crowd is composed of two kinds of individuals: those who know the layout of the building, and those who do not and rely exclusively on potentially informed neighbors to identify a path towards the exit. We aim to capture the effect the knowledge of the environment has on the interaction between evacuees and their residence time in the presence of fire and evolving smoke. Our approach is genuinely multiscale—we employ a two-scale model that is able to distinguish between compressible and incompressible pedestrian flow regimes and allows for micro and macro pedestrian dynamics. Simulations illustrate the expected qualitative behavior of the model. We finish with observations on how mixing evacuees with different levels of knowledge impacts important evacuation aspects.

DOI: 10.1103/PhysRevLett.118.138302 URL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.138302 Filiació URV: SI We introduce a framework to intertwine dynamical processes of different nature, each with its own distinct network topology, using a multilayer network approach. As an example of collective phenomena emerging from the interactions of multiple dynamical processes, we study a model where neural dynamics and nutrient transport are bidirectionally coupled in such a way that the allocation of the transport process at one layer depends on the degree of synchronization at the other layer, and vice versa. We show numerically, and we prove analytically, that the multilayer coupling induces a spontaneous explosive synchronization and a heterogeneous distribution of allocations, otherwise not present in the two systems considered separately. Our framework can find application to other cases where two or more dynamical processes such as synchronization, opinion formation, information diffusion, or disease spreading, are interacting with each other.

Analysis of ‘entropy generation’ is an important strategy to optimize the natural convection process in order to achieve efficient heat transfer within the system. Rhombic enclosures of various inclination angles ( φ = 30 ° , 45° and 75°) filled with porous media and bounded by adiabatic top wall, cold side walls, isothermally (case 1) and non-isothermally (case 2) heated bottom wall have been considered for the analysis of thermal processing of various fluids ( Pr =0.015, 0.7, 7.2 and 1000) in the range of Darcy number ( Da =10 −5 – 10 −3 ). At Da =10 −5 , the total entropy generation, S total , is found to be significantly high for φ = 30 ° and low for φ = 75 ° and is dominated by heat transfer irreversibility ( S θ ) for all Pr in case 1 whereas the distributions of S total for φ = 45 ° , 75° and 90° closely follow the distributions of φ = 30 ° for all Pr in case 2. Cup mixing temperature ( Θ cup ) is higher for φ = 75 ° and 90° whereas overall heat transfer rate, Nu ¯ , is higher for φ = 30 ° compared to other φ s in both heating cases except at high Pr ( 0.7 − 1000 ) fluids at Da =10 −5 . On increase of Da to 10 − 3 , fluid friction irreversibility, S ψ also increases for all φ s irrespective of Pr in both cases. Increase in S total with Da is small for lower φ ( φ = 30 ° ) due to insignificant S ψ of S total and large for higher φ ( φ = 75 ° ) due to significant S ψ of S total at Da ≥ 10 − 4 irrespective of Pr in both cases. Also, Θ cup slightly decreases at Da ≥ 10 − 4 and further, that reaches a constant value at higher Da as well as S total in both cases irrespective of φ for all Pr except Pr =0.015. Maximum Nu ¯ occurs for φ = 30 ° cavities at Da =10 −3 for all Pr in case 1 due to less available energy loss corresponding to less S ψ . Current work attempts to analyze energy efficient thermal convection strategies within porous rhombic enclosures based on entropy generation minimization vs enhanced thermal mixing or heat transfer rates for various fluids in porous media.

A numerical model is developed for investigating the evolution of fracture permeability in a coupled fracture-matrix system in the presence of fracture-skin with simultaneous colloidal and bacterial transport, by taking into account the effects of thermal stress and silica precipitation/dissolution, which is computed using linear reaction kinetics. The non-linear coupled equations are numerically modeled using the fully implicit finite difference method and a constant continuous source is adopted while modeling thermal, contaminant, colloidal and bacterial transport. Due to co-colloid bacterial transport under non-isothermal conditions, in a coupled fracture-skin-matrix system, the fracture apertures vary spatially, with a corresponding pressure variation for a constant discharge. A series of numerical experiments were conducted for analyzing the spatial variation of fracture aperture in response to the combined effects of thermal stress, silica precipitation/dissolution, and simultaneous colloidal and bacterial transport in the presence of the fracture-skin. The simulation results suggest that temperature and contaminant concentration of the mobile fluid within the fracture increases with reduction in initial fracture aperture. The pattern of variation followed by the fracture aperture is nearly the same in the presence and absence of bacterial transport but the magnitude of the fracture aperture is low under the influence of bacterial transport. The variation in the fracture aperture resulting from precipitation-dissolution and thermoelastic stress is significant when the fracture aperture is very low and reduces with increment in fracture aperture. The variation in fracture aperture and pressure remains the same for both undersaturated and supersaturated fluid entering the fracture due to the influence of bacterial transport at the inlet of the fracture. � 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

A numerical study of the interaction between flow, reactions and thermal effects in a planar two dimensional model of a catalytic convertor is presented. A typical catalytic convertor consists of an inlet manifold, a catalytic monolith and an outlet manifold. The catalytic monolith is modeled as a multi-channel structure. Two different planar 2D geometries are compared: a full-scale geometry with 85 channels and a reduced-scale model with 21 channels. The diverging diffuser section of the inlet manifold, which lies immediately upstream the catalytic monolith, induces flow non-uniformity along the transverse direction. The flow immediately upstream of the multi-channel monolith is highly non-uniform. However, the frictional pressure drop in the individual channels tends to reduce this non-uniformity within individual channels. A "flow distribution index" - ratio of actual flow-rate in a channel to the ideal expected flow-rate if the flow was uniform - is defined to numerically characterize the flow mal-distribution across the various channels in the monolith. The velocity and scale effects are analyzed. Higher inlet velocities induce more flow non-uniformity. Catalytic oxidation of CO represented by power-law kinetics is employed to study the role of flow distribution. The flow distribution affects the conversion in the catalytic convertor, with different conversions in central and peripheral channels of the monolith. The net conversion from the device is marginally lower than what is predicted by single channel simulations with an assumption of uniform flow distribution. The thermal effects due to heat losses and reactions also in turn affect flow distribution. The flow tends to be more uniform when heat losses are included in the non-adiabatic simulations for the geometric parameters and kinetics considered in this work. � 2011 Elsevier Ltd.

International audience; A vertical distribution of helium-4 was obtained in pore-water from the Toarcian/Domerian argillaceous formation at Tournemire (South Aveyron, France). Most of the studied core samples were collected from two vertical air-drilled boreholes across the impervious argillaceous formation and penetrating the bounding aquifers. Accessible porosities for helium were assumed similar to those of water and calculated by weighting before and after heating the core samples. Helium-4 concentrations were obtained after out-gassing the rock samples in tight containers. The comparison of the total amount of 4He produced since the deposition of the formation with that presently measured in the rock reveals that more than 97% of 4He has been lost from the solid phase to pore-water and afterwards to the surrounding aquifers. Helium distribution in pore water shows a complex profile because of the presence of unexpectedly 4He-rich samples in the lower part of the Upper Toarcian level. In order to understand this distribution and to assess the transport of helium at the formation scale, a series of preliminary model calculations were performed using helium diffusion coefficients three times higher than those of water isotopes. The comparison between simulated and experimental data indicates that: (1) the helium profile could be similar to those of deuterium and chloride in pore-water if some unexpectedly 4He-rich samples are not considered; (2) the estimated transport parameters (at small scale) may be transposable at the formation scale with some uncertainties; (3) a steady state has most probably been reached between the in situ helium production and its loss towards the aquifers; (4) only 17-30Ma of diffusion time would be necessary to obtain steady state; this is short compared to the formation age (180Ma) and thus the helium profile cannot give very precise information about diffusion time in the massif, but is in agreement with the hypothesis that transport processes are dominated by diffusion. © 2011 Elsevier Ltd.

Fluorescence correlation spectroscopy (FCS) is a powerful technique for measuring low concentrations of fluorescent molecules and their diffusion coefficients in an open detection volume. However, in several practical cases, when FCS measurements are carried out in small compartments like microchannels, neglecting boundary effects could lead to erroneous results. Here, a close form solution is proposed to explicitly account for the presence of walls located at a distance comparable with the characteristic detection volume lengths. We derive a one-dimensional diffusion constrained model and then generalize the solution to the two- and the three-dimensional constrained cases. We further indicate within which limits the standard autocorrelation function (ACF) model gives reliable results in microconfinement. Our model relies just on the assumption of elastic hits at the system walls and succeeds in describing the ACF of fluorescent probes confined along one direction. Through the analysis of FCS experimental data, we are able to predict the correct shape of the ACF in channels of micrometric and submicrometric width and measure the extent of lateral confinement. In addition, it permits the investigation of microstructured material features such as cages and cavities having dimensions on the micrometric range. On the basis of the proposed model, we also show in which conditions confinement could generate an apparent time dependent probe mobility, thus allowing a proper interpretation of the transport process taking place in submicrometric compartments.

We present an experimental and theoretical characterization of single cigar-shaped nanopores with pH-responsive carboxylic acid and lysine chains functionalized on the pore surface. The nanopore characterization includes (i) optical images of the nanostructure obtained by FESEM; (ii) different chemical procedures for the nanopore preparation (etching time and functionalizations; pH and electrolyte concentration of the external solution) allowing externally tunable nanopore responses monitored by the current-voltage (I-V) curves; and (iii) transport simulations obtained with a multilayer nanopore model. We show that a single, approximately symmetric nanopore can be operated as a reconfigurable diode showing different rectifying behaviors by applying chemical and electrical signals. The remarkable characteristics of the new nanopore are the sharp response observed in the I-V curves, the improved tunability (with respect to previous designs of symmetric nanopores) which is achieved because of the direct external access to the nanostructure mouths, and the broad range of rectifying properties. The results concern both fundamental concepts useful for the understanding of transport processes in biological systems (ion channels) and applications relevant for tunable nanopore technology (information processing and drug controlled release). © 2012 American Chemical Society., P.R., J.C., and S.M. acknowledge the financial support from the Ministry of Science and Innovation of Spain, Materials Program (Project Nos. MAT2009-07747) and FEDER. M.A., Q.H.N., S.N, and W.E. gratefully acknowledge financial support by the Beilstein-Institut, Frankfurt/Main, Germany, within the research collaboration NanoBiC, and Prof. C. Trautmann (GSI, Department of Materials Research) for support with irradiation experiments.

International audience; Metal uptake by plants occurs by soil−root transfer but also by direct transfer of contaminants from the atmosphere to the shoots. This second pathway may be particularly important in kitchen gardens near industrial plants. The mechanisms of foliar uptake of lead by lettuce (Lactuca sativa) exposed to the atmospheric fallouts of a lead-recycling plant were studied. After 43 days of exposure, the thoroughly washed leaves contained 335 ± 50 mg Pb kg−1 (dry weight). Micro-X-ray fluorescence mappings evidenced Pb-rich spots of a few hundreds of micrometers in diameter located in necrotic zones. These spots were more abundant at the base of the central nervure. Environmental scanning electron microscopy coupled with energy dispersive X-ray microanalysis showed that smaller particles (a few micrometers in diameter) were also present in other regions of the leaves, often located beneath the leaf surface. In addition, submicrometric particles were observed inside stomatal openings. Raman microspectrometry analyses of the leaves identified smelter-originated Pb minerals but also secondary phases likely resulting from the weathering of original particles. On the basis of these observations, several pathways for foliar lead uptake are discussed. A better understanding of these mechanisms may be of interest for risk assessment of population exposure to atmospheric metal contamination.

We propose a unified physical framework for transport in variably saturated porous media. This approach allows fluid flow and solute migration to be treated as ensemble averages of fluid and solute particles, respectively. We consider the cases of homogeneous and heterogeneous porous materials. Within a fractal mobile-immobile (MIM) continuous time random walk framework, the heterogeneity will be characterized by algebraically decaying particle retention-times. We derive the corresponding (nonlinear) continuum limit partial differential equations and we compare their solutions to Monte Carlo simulation results. The proposed methodology is fairly general and can be used to track fluid and solutes particles trajectories, for a variety of initial and boundary conditions., Comment: 12 pages, 9 figures

Observations have revealed widespread emissions of alkyl nitrates from the tropical and Southern Oceans. We present the first chemical transport model simulations to examine the global impact of these emissions. Matching observed atmospheric abundances, we derive a total oceanic flux of methyl nitrate (MeONO2) and ethyl nitrate (EtONO2) equivalent to 0.35 Tg of N per year, which contributes as much as 1 DU to the tropospheric ozone column in the Western Pacific and is responsible for about 3% of the global oxidative capacity of the troposphere.

The present article analyzes the dissipation characteristics of the direct contact condensation (DCC) phenomenon that occurs when steam is injected into a water tank at a subsonic speed using a new modeling approach for the entropy generation over the calculation domain. The developed entropy assessment model is based on the local equilibrium hypothesis of non-equilibrium thermodynamics. The fluid flow and heat transfer processes are investigated numerically. To describe the condensation and evaporation process at the vapor-liquid interface, a phase change model originated from the kinetic theory of gas is implemented with the mixture model for multiphase flow in the computational fluid dynamics (CFD) code ANSYS-FLUENT. The CFD predictions agree well with the published works, which indicates the phase change model combined with the mixture model is a promising way to simulate the DCC phenomenon. In addition, three clear stages as initial stage, developing stage and oscillatory stage are discriminated from both the thermal-hydraulic results and the entropy generation information. During different stages, different proportion of the entropy generation rate owing to heat transfer, viscous direct dissipation, turbulent dissipation and inner phase change in total entropy generation rate is estimated, which is favorable to deeper understanding the irreversibility of DCC phenomenon, designing and optimizing the equipment involved in the process.

In the secondary electron emission (SEE) from solids, the role of different excitation processes is now as ever of special interest from both the theoretical and the experimental points of view. Depending on the primary energy, the relative importance of different excitation mechanisms related to conduction as well as core electrons will be discussed for different simple metals. So far, first principles results are available only for Al for primary energies up to 10 keV. Starting from a microscopic description of the SEE based on the transport equation formalism, calculations were performed for other nearly-free-electron metals (Mg, Be) up to primary energies used in scanning electron microscopy. In this way, it is possible to obtain more general statements about the role of different excitation processes responsible for SEE. Special attention is devoted to the contribution of emitted electrons stemming from the excitation of conduction electrons by decay of bulk plasmons generated by the primary electron. The different strength of this excitation mechanism in Al, Mg, and Be is related to the different magnitude of the plasmon damping in these metals.

Starting from a microscopic description of the particle-induced kinetic electron emission based on the transport equation formalism, the role of different excitation and scattering mechanisms is investigated. Especially, the excitation of electrons by decay of plasmons generated by the impinging particle results in an important contribution to the electron yield. In the case of ion-induced kinetic electron emission, the special features of the energy distribution of emitted electrons are related to the plasmon damping and the plasmon dispersion. In order to describe the available experimental results on nearly-free-electron metals (Al,Mg) in a consistent way, plasmon effects must be taken into account within the excitation process as well as in the description of the transport of excited electrons towards the surface of the solid.

An outline is given of some of the steps which in the last ten years have led to an understanding of many of the properties of conduction and valence bands in non-crystalline materials. The concept of a mobility edge is described and some of the experimental evidence for its existence. A discussion is given of the nature of states in the gap, thought of as deep donors or acceptors. These pin the Fermi energy and act as recombination centres. A distinction is made between materials such as silicon or germanium with fourfold co-ordination and those like As2Te3 or SiO 2, where for the chalcogen (Te or O) co-ordination is twofold; for the former an electron in a deep state produces only moderate distortion of the lattice, for the latter the distortion is large. Photoluminescence and other properties of chalcogenides ave discussed in terms of a recent model of charged dangling bonds. It is suggested that free holes in As2Te3 and As 2Se3 are not self-trapped but that in SiO2 they are. Finally the nature of the optical absorption edge in SiO2 is contrasted with that in a soda glass in terms of a model of self-trapped excitons.

Two models are given of branching transport processes that converge to branching Brownian motion starting with one initial particle. The martingale problem method is used.

The aim of the atmospheric nitrogen inputs into the coastal ecosystem (ANICE) project is to improve transport-chemistry models that estimate nitrogen deposition to the sea. To achieve this, experimental and modelling work is being conducted which aims to improve understanding of the processes involved in the chemical transformation, transport and deposition of atmospheric nitrogen compounds. Of particular emphasis within ANICE is the influence of coastal zone processes. Both short episodes with high deposition and chronic nitrogen inputs are considered in the project. The improved transport-chemistry models will be used to assess the atmospheric inputs of nitrogen compounds into the European regional seas (the North Sea is studied as a prototype) and evaluate the impact of various emission reduction strategies on the atmospheric nitrogen loads. Assessment of the impact of atmospheric nitrogen on coastal ecosystems will be based on comparisons of phytoplankton nitrogen requirements, other external nitrogen inputs to the ANICE area of interest and the direct nitrogen fluxes provided by ANICE. Selected results from both the experimental and modelling components are presented here. The experimental results show the large spatial and temporal variability in the concentrations of gaseous nitrogen compounds, and their influences on fluxes. Model calculations show the strong variation of both concentrations and gradients of nitric acid at fetches of up to 25km. Aerosol concentrations also show high temporal variability and experimental evidence for the reaction between nitric acid and sea salt aerosol is provided by size-segregated aerosol composition measured at both sides of the North Sea. In several occasions throughout the experimental period, air mass back trajectory analysis showed connected flow between the two sampling sites (the Weybourne Atmospheric Observatory on the North Norfolk coast of the UK and Meetpost Noordwijk, a research tower at 9km off the Dutch coast). Results from the METRAS/SEMA mesoscale chemistry transport model system for one of these cases are presented. Measurements of aerosol and rain chemical composition, using equipment mounted on a commercial ferry, show variations in composition across the North Sea. These measurements have been compared to results obtained with the transport-chemistry model ACDEP which calculates the atmospheric inputs into the whole North Sea area. Finally, the results will be made available for the assessment of the impact of atmospheric nitrogen on coastal ecosystems.

The article of record as published may be located at http://dx.doi.org/10.1002/2013JD021228 Includes a supplemental bitstream. During the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and 2013 Nucleation in California Experiment (NiCE) field campaigns, a predominantly organic aerosol (> 85% by mass) was observed in the free troposphere over marine stratocumulus off the coast of California. These particles originated from a densely forested region in the Northwestern United States. The organic mass spectrum resolved by positive matrix factorization is consistent with the mass spectra of previously measured biogenic organic aerosol. Particulate organic mass exhibits a latitudinal gradient that corresponds to the geographical distribution of vegetation density and composition, with the highest concentration over regions impacted by densely populated monoterpene sources. Due to meteorological conditions during summer months, cloud-clearing events transport aerosol from the Northwestern United States into the free troposphere above marine stratocumulus. Based on the variation of meteorological variables with altitude, dry air containing enhanced biogenic organic aerosol is shown to entrain into the marine boundary layer. Fresh impacts on cloud water composition are observed north of San Francisco, CA which is consistent with fresh continental impacts on the marine atmosphere at higher latitudes. Continental aerosol size distributions are bimodal. Particles in the 100 nm mode are impacted by biogenic sources, while particles in the ~ 30 nm mode may originate from fresh biogenic emissions. Continental aerosol in the 100 nm mode is cloud condensation nuclei active and may play a role in modulating marine stratocumulus microphysics.

Solute transport in natural formations at the regional scale is influenced by several scales of heterogeneity which correspond to the presence of several geological units called facies. As customarily assumed in stochastic theories, inside the facies the transport can be characterized by a single scale of heterogeneity. At the regional scale several geological units are present such that a hierarchy of relevant scales needs to be defined. A possible model for this spatial variability assumes the log conductivity as a random space function of stationary increments characterized by a power law semivariogram. With this hypothesis the ergodic dispersion coefficient grows unbounded as time increases, leading to the phenomenon called anomalous dispersion. An alternative approach considers the plume in nonergodic conditions and assumes the effective dispersion coefficient, which is defined through differentiation in time of the expected value of the spatial second-order plume moment, as representative of macrodispersion. Large differences have been observed in the resulting plume spreading while approaching the problem using the above alternative definitions. In this paper we provide first-order analytical solutions for the longitudinal effective dispersion coefficient, D(L), as well as for the expected value of the longitudinal spatial plume moment, , that complement semianalytical expressions recently proposed in literature. Furthermore, we provide a semianalytical expression for the standard deviation of the longitudinal second-order moment which is important in assessing the interval of confidence of the estimation provided by . Suitable numerical simulations are performed to validate analytical and semianalytical expressions as well as to assess the impact of the cutoff in the log conductivity power spectrum imposed by choosing a finite domain dimension. We conclude that according to recently published results, the dispersion is anomalous when the Hurst coefficients, H, is larger than 0.5 while it is Fickian for H < 0.5. This is in contrast with the ergodic analysis which concludes that the dispersion is anomalous irrespective of the Hurst coefficient. Hence the effective dispersion coefficient is more effective than the ergodic dispersion coefficient to represent the plume spreading. However, the standard deviation of the longitudinal spatial second-order moment is of the same order of magnitude as the expected value leading to the conclusion that the estimations provided by D(L) and are affected by large uncertainties. Numerical results are in good agreement with the analytical solutions, and under some hypotheses they are not influenced by the cutoff. This is not the case for the ergodic second-order longitudinal moment, which strongly depends on the imposed cutoff.

Quantum fluctuations are imprinted with valuable information about transport processes. Experimental access to this information is possible, but challenging. We introduce the dynamical Coulomb blockade (DCB) as a local probe for fluctuations in a scanning tunneling microscope (STM) and show that it provides information about the conduction channels. In agreement with theoretical predictions, we find that the DCB disappears in a single-channel junction with increasing transmission following the Fano factor, analogous to what happens with shot noise. Furthermore we demonstrate local differences in the DCB expected from changes in the conduction channel configuration. Our experimental results are complemented by ab initio transport calculations that elucidate the microscopic nature of the conduction channels in our atomic-scale contacts. We conclude that probing the DCB by STM provides a technique complementary to shot noise measurements for locally resolving quantum transport characteristics., 9 pages, 7 figures, including supplementary material

The equation of motion for a local Josephson junction will be solved assuming a current phase relation j = σ0(V) V + σ1(V) V cos ϕ + j 1( V) sin ϕ including an interference term σ 1. The characteristics and the stationary state has been discussed, if σ 0, σ 1, j1 are approximated by appropriate voltage averages of the functions derived from weak-coupling BCS theory. Analytical solutions have been found for the weak and the strong damped junction, whereas for medium damping computer solutions can be given. The Josephson characteristics for σ 1 < 0 essentially cross over the normal characteristics σ 0 V, a feature which may be detectable experimentally. The current quite generally in(de)creases, if σ 1 in(de)creases and | σ1 | ≤ σ 0.