Single- and double-electron processes in collisions of Xe23+ ions with helium

We report the measurements of relative cross sections for single capture (SC), double capture (DC), single ionization (SI), double ionization (DI), and transfer ionization (TI) in collisions of Xe23+ ions with helium atoms in the velocity range of 0.65-1.32 a.u. The relative cross sections show a weak velocity dependence. The cross-section ratio of double-(DE) to single-electron (SE) removal from He, sigma(DE)/sigma(SE), is about 0.45. Single capture is the dominant reaction channel which is followed by transfer ionization, while only very small probabilities are found for pure ionization and double capture. The present experimental data are in satisfactory agreement with the estimations by the extended classical over-barrier (ECB) model..

Excitation and dissociation of tungsten hexacarbonyl W(CO)(6): Statistical and nonstatistical dissociation processes

We have studied the excitation and dissociation processes of the molecule W(CO)(6) in collisions with low kinetic energy (3 keV) protons, monocharged fluorine, and chlorine ions using double charge transfer spectroscopy. By analyzing the kinetic energy loss of the projectile anions, we measured the excitation energy distribution of the produced transient dications W(CO)(6)(2+). By coincidence measurements between the anions and the stable or fragments of W(CO)(6)(2+), we determined the energy distribution for each dissociation channel. Based on the experimental data, the emission of the first CO was tentatively attributed to a nonstatistical direct dissociation process and the emission of the second or more CO ligands was attributed to the statistical dissociation processes. The dissociation energies for the successive breaking of the W-CO bond were estimated using a cascade model. The ratio between charge separation and evaporation (by the loss of CO+ and CO, respectively) channels was estimated to be 6% in the case of Cl+ impact. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3523347]

A model study on carbon cycle and phytoplankton dynamical processes in the Bohai Sea

The carbon cycle of lower trophic level in the Bohai Sea is studied with a three-dimension-al biological and physical coupled model. The influences of the processes (including horizontal advection,river nutrient load, active transport etc. ) on the phytoplankton biomass and its evolution are estimated.The Bohai Sea is a weak sink of the CO2 in the atmosphere. During the cycle, 13.7% of the gross pro-duction of the phytoplankton enter the higher trophic level and 76.8 % of it are consumed by the respira-tion itself. The nutrient reproduction comes mainly from the internal biogeochemical loop and the rem-ineralization is an important mechanism of the nutrient transfer from organic form to inorganic. Horizon-tal advection decreases the total biomass and the eutrophication in some sea areas. Change in the nutrientload of a river can only adjust the local system near its estuary. Controlling the input of the nutrient,which limits the alga growth, can be very useful in lessening the phytoplankton biomass.

a dynamic model to handle defect-oriented processes

Tongji Univ, Inst Dev Study, Syst Engn Soc China, Comm Syst Dynam, Syst Dynam Soc, China Chapter, Shanghai Inst Foreign Trade, Syst Dynam Soc, Chapters Asia Pacific Area

a fuzzy-based method for evaluating the trustworthiness of software processes

University of Paderborn; Fraunhofer Inst. Exp. Softw. Eng. (IESE); Chinese Academy of Science (ISCAS)

Impacts of LUCC processes on potential land productivity in China in the 1990s

Using meteorological data and RS dynamic land-use observation data set, the potential land productivity that is limited by solar radiation and temperature is estimated and the impacts of recent LUCC processes on it are analyzed in this paper. The results show that the influence of LUCC processes on potential land productivity change has extensive and unbalanced characteristics. It generally reduces the productivity in South China and increases it in North China, and the overall effect is increasing the total productivity by 26.22 million tons. The farmland reclamation and original farmlands losses are the primary causes that led potential land productivity to change. The reclamation mostly distributed in arable-pasture and arable-forest transitional zones and oasises in northwestern China has made total productivity increase by 83.35 million tons, accounting for 3.50% of the overall output. The losses of original farmlands driven by built-up areas invading and occupying arable land are mostly distributed in the regions which have rapid economic development, e.g. Huang-Huai-Hai plain, Yangtze River delta, Zhujiang delta, central part of Gansu, southeast coastal region, southeast of Sichuan Basin and Urumqi-Shihezi. It has led the total productivity to decrease 57.13 million tons, which is 2.40% of the overall output.

Modelling raindrop impact and splash erosion processes within a spatial cell: a stochastic approach

A new approach is proposed to simulate splash erosion on local soil surfaces. Without the effect of wind and other raindrops, the impact of free-falling raindrops was considered as an independent event from the stochastic viewpoint. The erosivity of a single raindrop depending on its kinetic energy was computed by an empirical relationship in which the kinetic energy was expressed as a power function of the equivalent diameter of the raindrop. An empirical linear function combining the kinetic energy and soil shear strength was used to estimate the impacted amount of soil particles by a single raindrop. Considering an ideal local soil surface with size of I m x I m, the expected number of received free-failing raindrops with different diameters per unit time was described by the combination of the raindrop size distribution function and the terminal velocity of raindrops. The total splash amount was seen as the sum of the impact amount by all raindrops in the rainfall event. The total splash amount per unit time was subdivided into three different components, including net splash amount, single impact amount and re-detachment amount. The re-detachment amount was obtained by a spatial geometric probability derived using the Poisson function in which overlapped impacted areas were considered. The net splash amount was defined as the mass of soil particles collected outside the splash dish. It was estimated by another spatial geometric probability in which the average splashed distance related to the median grain size of soil and effects of other impacted soil particles and other free-falling raindrops were considered. Splash experiments in artificial rainfall were carried out to validate the availability and accuracy of the model. Our simulated results suggested that the net splash amount and re-detachment amount were small parts of the total splash amount. Their proportions were 0.15% and 2.6%, respectively. The comparison of simulated data with measured data showed that this model could be applied to simulate the soil-splash process successfully and needed information of the rainfall intensity and original soil properties including initial bulk intensity, water content, median grain size and some empirical constants related to the soil surface shear strength, the raindrop size distribution function and the average splashed distance. Copyright (c) 2007 John Wiley & Sons, Ltd.

Enhancements of the simulation method on the edge effect in resin transfer molding processes

In resin transfer molding processes, small clearances exist between the fiber preform and the mold edges, which result in a preferential resin flow in the edge channel and then disrupt the flow patterns during the mold filling stage. A mathematical model including the effect of cavity thickness on resin flow was developed for flow behavior involving the interface between an edge channel and a porous medium. According to the mathematical analysis of momentum equations in a fully developed rectangular duct and formulations of the equivalent edge permeability, comparing with three-dimensional Navier-Stokes equations, the governing equations were modified in the edge channel. The volume of fluid (VOF) method was applied to track the flow front. A simple case is numerically simulated using the modified governing equations. The effects of edge channel width and cavity thickness on flow front and inlet pressure are analyzed, and the evolution characteristics of simulated results are in agreement with the experimental results. (c) 2007 Elsevier B.V. All rights reserved

Numerical Simulation of Reactive Extrusion Processes for Activated Anionic Polymerization

In order to deal with the complicated relationships among the variables of the reactive extrusion process for activated anionic polymerization, a three-dimensional equivalent model of closely intermeshing co-rotating twin screw extruders was established. Then the numerical computation expressions of the monomer concentration, the monomer conversion, the average molecular weight and the fluid viscosity were deduced, and the numerical simulation of the reactive extrusion process of Styrene was carried out. At last, our simulated results were compared with Michaeli's simulated results and experimental results. (C) 2007 Elsevier B.V. All rights reserved

Magnetic control of bioelectrocatalytic processes based on assembled iron oxide particles

A facile magnetic control system was designed in bioelectrocatalytic process based on functionalized iron oxide particles. The iron oxide particles were modified with glucose oxidase, and ferrocene dicarboxylic acid was used as electron transfer mediator. Functionalized iron oxide particles can assemble along the direction of applied magnetic field, and the directional dependence of the assembled iron oxide particles can be utilized for device purposes. We report here how such functionalized magnetic particles are used to modulate the bioelectrocatalytic signal by changing the orientation of the applied magnetic field. (C) 2008 Elsevier B.V. All rights reserved.

Reactive Mold Filling in Resin Transfer Molding Processes with Edge Effects

Reactive mold filling is one of the important stages in resin transfer molding processes, in which resin curing and edge effects are important characteristics. On the basis of previous work, volume-averaging momentum equations involving viscous and inertia terms were adopted to describe the resin flow in fiber preform, and modified governing equations derived from the Navier-Stokes equations are introduced to describe the resin flow in the edge channel. A dual-Arrhenius viscosity model is newly introduced to describe the chemorheological behavior of a modified bismaleimide resin. The influence of the curing reaction and processing parameters on the resin flow patterns was investigated.

Numerical simulation of coil-helix transition processes of gelatin

Gelatin is widely used in food, pharmaceutical, and photographic industries due to the coil-helix transition, whereas the structural inhomogeneity considerably affects its essential properties closely connecting with the industrial applications. The spatially structural inhomogeneity of the gelatin caused by the uneven and unstable temperature field is analyzed by the finite element method during the cooling-induced coil-helix transition process. The helix conversion and the crosslinking density as functions of time and spatial grid are calculated by the incremental method. A length distribution density function is introduced to describe the continuous length distributions of two kinds of triple helices.

Controlled synthesis of monodisperse nanocrystals by a two-phase approach without the separation of nucleation and growth processes

The synthesis of monodisperse nanocrystals is an important topic in the field of nanomaterials not only for practical applications, but also for scientific interest in fundamental research. In this feature article, we mainly focus on synthesis of monodisperse nanocrystals by a two-phase approach without the separation of nucleation and growth processes, and report some progress made recently in the observation and understanding of nucleation and growth of semiconductor nanocrystals. Firstly, a novel two-phase approach to monodisperse nanocrystals, which is different from the well-established synthesis models, is discussed. We demonstrate that the two-phase approach has a quite lengthy nucleation process, and can be applied to the synthesis of many kinds of binary monodisperse nanocrystals.

Charge Transport Processes of Immobilized Heteropolyanions at Self-assembled Monolayer Modified Gold Electrode by Electrochemical Quartz Crystal Microbalance Measurement

The in situ electrochemical quartz crystal microbalance(EQCM) technique was used to investigate the ion transport of immobilized heteropolyanions at a self-assembled monolayer(SAM) modified gold electrode during electrochemical redox process. A mixed transfer method was presented to analyse the abnormal change of resonant frequency based on the simultaneous insertion/extraction of different ions. The results indicate that the migration of HSO4- anions was indispensable in the redox process of the heteropolyan ions in a I mol/L H2SO4 solution and played a key role in the abnormal change of the resonant frequency. Such a change was attributed to different packing densities derived by means of differently immobilized methods.