Bulk etch rates of CR-39 at high etchant concentrations:diffusionlimited etching

Systematic CR-39 bulk etching experiments were conducted over a wide range of concentrations(2–30 N)of NaOH-based etchant.Critical analysis and a deep discussion of the results are presented.A comprehensive nuclear track chemical etching data bank was developed.Three regimes of CR-39 bulk etching were identified.Regime I spans etchant concentrations from 2 to 12 N.Regime II spans concentrations from 12 to 25 N.We call this the dynamic bulk etching regime.Regime III is for concentrations greater than 25 N.In this regime,the bulk etch rate is saturated with respect to the etchant concentration.This classification is discussed and explained.The role of ethanol in NaOH-based etchants is explored and discussed.A parameter called the “reduced bulk etch rate” is defined here,which helps in analyzing the dependence of bulk etching on the amount of ethanol in the etchant.The bulk etch rate shows a natural logarithmic dependence on the density of ethanol in the etchant.

Bulk Etch Rate of LR 115 Polymeric Radon Detector

In this study, we used strippable LR 115 type 2 which is a Solid State Nuclear Track Detector (SSNTD) widely known for radon gas detection and measurement. The removed thickness of the active layer of samples of this SSNTD, were determined by measuring the average initial thickness (before etching) and residual thickness after 80 to 135 minutes chemical etching in the standard conditions, using an electronic comparator. These results allowed the calculation of the bulk etch rate of this detector in a simple way. The mean value obtained is (3.21 ± 0.21) μm/h. This value is in close agreement with those reported by different authors. It is an important parameter for alpha track counting on the sensitive surface of this polymeric detector after chemical etching because track density depends extremely on its removed layer. This SSNTD was then used for environmental radon gas monitoring in Côte d’Ivoire.

Measure the Bulk Etch Rate Using the Time-Diameter Method

The present work measured the bulk etch rate (VB?) of solid state nuclear track detector by taking the diameter time measurement of alpha particle in CR-39 detector. The values of the track diameter have been found by using TRACK-TEST program from Yu et al. function and Brun et al. function with different energies of alpha particles. The results showed that the time-diameter (t-d) method gave good results of the bulk etch rate (VB?) and these values were (1.705 and 1.72) μm·hr-1. They showed good agreement with the values measured by using the other methods, and it was a simple method because it required getting diameters of the tracks in the detector with the etching time.

The Probability Density Function Related to Shallow Cumulus Entrainment Rate and Its Influencing Factors in a Large-Eddy Simulation

The process of entrainment-mixing between cumulus clouds and the ambient air is important for the development of cumulus clouds.Accurately obtaining the entrainment rate(λ)is particularly important for its parameterization within the overall cumulus parameterization scheme.In this study,an improved bulk-plume method is proposed by solving the equations of two conserved variables simultaneously to calculateλof cumulus clouds in a large-eddy simulation.The results demonstrate that the improved bulk-plume method is more reliable than the traditional bulk-plume method,becauseλ,as calculated from the improved method,falls within the range ofλvalues obtained from the traditional method using different conserved variables.The probability density functions ofλfor all data,different times,and different heights can be well-fitted by a log-normal distribution,which supports the assumed stochastic entrainment process in previous studies.Further analysis demonstrate that the relationship betweenλand the vertical velocity is better than other thermodynamic/dynamical properties;thus,the vertical velocity is recommended as the primary influencing factor for the parameterization ofλin the future.The results of this study enhance the theoretical understanding ofλand its influencing factors and shed new light on the development ofλparameterization.

Accuracy Analysis of Assembly Success Rate with Monte Carlo Simulations

Monte Carlo simulation was applied to Assembly Success Bate (ASK) analyses. ASR of two peg-in-hole robot assemblies was used as an example by taking component parts' sizes, manufacturing tolerances and robot repeatability into account. A statistic arithmetic expression was proposed and deduced in this paper, which offers an alternative method of estimating the accuracy of ASR, without having to repeat the simulations. This statistic method also helps to choose a suitable sample size, if error reduction is desired. Monte Carlo simulation results demonstrated the feasibility of the method.

Computer Simulation of Plastic Deformation in GrainBoundary Region under High Rate Loading

The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.

Preliminary Study on Simulation of Global Seismic Activities with Global Strain Rate

The relationship between the strain rate field observed by GPS and global distribution of strong earthquakes is analyzed in this work. How do we recognize the characteristics of global seismic activities with space observation technology? A preliminary model of Cellular Automata that could simulate the global seismic activities both in time and space has been established based on the results of global strain rate field provided by the GSRM Program. The grid of the model is evenly divided,which is consistent with that of GSRM.The status of each cell is its strain state,and is adjusted according to the evolution rules.Maximum shear strain criterion is adopted in the evolution of the Cellular Automata. The threshold for cells in surface expansion is 80% of that for those in compression. The preliminary model could in general simulate the main characteristics of the distribution of the global seismic activities. It could exhibit in general the global distribution of weak and active tectonic activities. Although the preliminary Cellular Automata model needs to be improved in many aspects,the result suggests the possibility of modeling the general features of rather complicated global seismic activities based on the strain rates obtained by GPS and other observations.

Adsorption and Step Elution of Urokinase Using Affinity Chromatography-Comparison of Data with Rate Model Simulation

A non-equilibrium chromatographic rate model was employed to simulate the affinity chromatography of urokinase. The chromatography process was developed to a yield of high purity product of urokinase from crude materials. The affinity gel used in the process was prepared by an epichlorohydrin-activation method using epichlorohydrin activated Sepharose 4B as a matrix and p-aminobenzamidine as a ligand. The chromatographic process were numerically simulated and analyzed with the aid of VERSE-LC computer simulator. Considering the basic principles, rate model with the back mixing in column inlet was utilized in simulating and studying the effect of the column inlet pattern on other parameters. Comparison of the simulation results with the experimental data showed that the rate model can be used to describe the affinity chromatography of urokinase in a fixed bed column with satisfactory accuracy.

A Simulation Based Comparison of Correlation Coefficients with Regard to Type I Error Rate and Power

In this simulation study, five correlation coefficients, namely, Pearson, Spearman, Kendal Tau, Permutation-based, and Winsorized were compared in terms of Type I error rate and power under different scenarios where the underlying distributions of the variables of interest, sample sizes and correlation patterns were varied. Simulation results showed that the Type I error rate and power of Pearson correlation coefficient were negatively affected by the distribution shapes especially for small sample sizes, which was much more pronounced for Spearman Rank and Kendal Tau correlation coefficients especially when sample sizes were small. In general, Permutation-based and Winsorized correlation coefficients are more robust to distribution shapes and correlation patterns, regardless of sample size. In conclusion, when assumptions of Pearson correlation coefficient are not satisfied, Permutation-based and Winsorized correlation coefficients seem to be better alternatives.

Dependence of wet etch rate on deposition,annealing conditions and etchants for PECVD silicon nitride film

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE

TDC Model for PSG Sacrificial Layer Etching with Hydrofluoric Acid

HF etching of sacrificial layers with different The existing model cannot fit the experimental data well perimental data increases with etching time. A modified structures, namely channel, bubble, and joint-channel, is studied. The error of etching rate between the existing model and the exmodel considering the diffusion coefficient as a function of HF concentration and temperature is proposed. The etching rate coefficient as a function of temperature and the effect of reaction production are also considered in the modified model. For the joint-channel structure, a new mathematical model for the etching profile is also adopted. Experimental data obtained with channel, bubble, and joint-channel structures are compared with the modified model and the previous model. The results show that the modified model matches the experiments well.

Numerical simulation of the hydrodynamics within octagonal tanks in recirculating aquaculture systems

A three-dimensional numerical model was established to simulate the hydrodynamics within an octagonal tank of a recirculating aquaculture system. The realizable k-e turbulence model was applied to describe the flow, the discrete phase model （DPM） was applied to generate particle trajectories, and the governing equations are solved using the finite volume method. To validate this model, the numerical results were compared with data obtained from a full-scale physical model. The results show that： （1） the realizable k-e model applied for turbulence modeling describes well the flow pattern in octagonal tanks, giving an average relative error of velocities between simulated and measured values of 18% from contour maps of velocity magnitudes; （2） the DPM was applied to obtain particle trajectories and to simulate the rate of particle removal from the tank. The average relative error of the removal rates between simulated and measured values was 11%. The DPM can be used to assess the self-cleaning capability of an octagonal tank; （3） a comprehensive account of the hydrodynamics within an octagonal tank can be assessed from simulations. The velocity distribution was uniform with an average velocity of 15 cm/s; the velocity reached 0.8 m/s near the inlet pipe, which can result in energy losses and cause wall abrasion; the velocity in tank corners was more than 15 cm/s, which suggests good water mixing, and there was no particle sedimentation. The percentage of particle removal for octagonal tanks was 90% with the exception of a little accumulation of 〈5 mm particle in the area between the inlet pipe and the wall. This study demonstrated a consistent numerical model of the hydrodynamics within octagonal tanks that can be further used in their design and optimization as well as promote the wide use of computational fluid dynamics in aquaculture engineering.

Physical simulation and theoretical analysis of migrating rate of inclusions in aluminum melt in electromagnetic field

Simulation law and physical simulation were used to study the kinematic behavior of inclusions in electromagnetic separation. It was found that velocity of spherical non metallic particles shares different functions in different Reynolds number range. The function of spherical particle’s velocity has been got by confirming the relationship between Reynolds number and resistance coefficient when Reynolds number is 0.2 ～10. For non spherical particles, the moving behavior is influenced by shape and orientation while spherical coefficient has nothing to do with the velocity of irregular particles. The influence of orientation of cuboid particle on the electromagnetic expulsive force has been indicated by numerical computation. [

Investigation and numerical simulation of inner-flow of an axial mineflow fan under low flow rate conditions

Because of unstable properties of axial mine flow fans working under conditions of low flow rates, the safety and reliability of fans in their operational zone is reduced. At times, serious vibration may bring about the destruction of equipment or even jeopardize the safety of entire factories. By means of oil flow visualization techniques and numerical simulation, we have investigated the inner-flow of an axial mine flow fan working under low flow rate conditions. The fundamental reasons of complex flow phenomena of the inner-flow of the flow fan under these stated conditions were revealed. At the same time and in order to improve the inner-flow under conditions of low flow rates, a blade separator and air separator were designed. From our tests we found that the blade separator and air separator are two kinds efficient methods to improve the unstable working characteristics of the axial mine flow fan operating under low flow rate conditions. The effect of the improvement of the air separator is stronger than that of the blade separator.

SYSTEM-LEVEL SIMULATION OF VIBRATORY MICROMACHINED GYROSCOPE WITH FENCE STRUCTURE

An equivalent circuit model of a novel fence structure vibratory micromachined gy- roscope's oscillating properties is modeled by electrical equivalent circuits according to its dynamics equation.Equivalent circuit model of oscillating and differential detection capacitance model are im- plemented in the circuit simulation tool PSPICE,which is available in oscillating properties analysis such as oscillating's transient response,steady response and frequency response to angular rate to op- timize working mode of the gyroscope.The model also enables sensor simulation with the interfacing electronics to analyse the performances of the whole system.Behavioral simulation of the system is performed to prove the function of detection circuits.The simulation results and measurement results show that the design of circuits is feasible.

Monte-Carlo Simulation of Surface Crack Growth Rate for Offshore Structural Steel E36-Z35

The Monte- Carlo method is used to simulate the surface fatigue crack growth rate for offshore structural steel E36-Z35, and to determine the distributions and relevance of the parameters in the Paris equation. By this method, the time and cost of fatigue crack propagation testing can be reduced. The application of the method is demonstrated by use of four sets of fatigue crack propagation data for offshore structural steel E36-Z35. A comparison of the test data with the theoretical prediction for surface crack growth rate shows the application of the simulation method to the fatigue crack propagation tests is successful.

Local inhomogeneity in totally asymmetric simple exclusion processes with different hopping rates

Local inhomogeneity in totally asymmetric simple exclusion processes （TASEPs） with different hopping rates was studied. Many biological and chemical phenomena can be described by these non-equilibrium processes. A simple approximate theory and extensive Monte Carlo computer simulations were used to calculate the steady-state phase diagrams and bulk densities. It is found that the phase diagram for local inhomogeneity in TASEP with different hopping rates p is qualitatively similar to homogeneous models. Interestingly, there is a saturation point pair （a＊, fl＊） for the system, which is decided by parameters p and q. There are three stationary phases in the system, when parameter p is fixed （i.e., p=0.8）, with the increase of the parameter q, the region of LD/LD and HD/HD phase increases and the HD/LD is the only phase which the region shrinks. The analytical results are in good agreement with simulations.

Modelling and Simulation of the Spread of HBV Disease with Infectious Latent

This paper studies the global behavior of the spread of HBV using a SEIR model with a constant vaccination rate. The infectivity during the incubation period is considered as a second way of transmission. The basic reproduction number R0 is derived as a function of the two contact rates?β1?and β2?. There is a disease free equilibrium point (DFE) of our model. When R0 R0 > 1, there is a unique endemic equilibrium. We proved that the endemic equilibrium was globally asymptotically stable when R0 > 1 and that the disease persisted in the population. These results are original for our model with vaccination and two contact rates.

Simulation of critical cooling rate and process conditions for metallic glasses in vertical type twin-roll casting

Critical cooling rates for producing metallic glasses were evaluated based on a calculated continuous cooling transformation(CCT)diagram.Temperature distributions of the melt in molten pool in the vertical type twin-roll casting(VTRC)process of metallic glasses were simulated,and cooling rates under different casting conditions were calculated with the simulated results.By comparing the results obtained by CCT diagrams and simulation,the possibility of producing metallic glasses by the VTRC method and influences of casting conditions on cooling rate were discussed.The results reveal that cooling rate with3or4orders of magnitude by the VTRC process can be attained in producing Mg-based metallic glasses,which is faster than the critical cooling rate calculated by the CCT diagram.One side pouring mode can improve the temperature distributions of casting pool.VTRC process has a good ability in continuous casting metallic glassy thin strips.

An Attempt to Study on the Growth and Damping Rates with Approximate Solutions by Using Mathematical Models

As is already known, most of the plasma literature is occupied with the plasma instabilities and the inevitable plasma waves, which remain major obstacles to the thermonuclear fusion process. Many experimental data on the plasma waves （growth or damping） and their accompanied theoretical interpretations have been published during the last five decades; lots of them have been identified and justified as well, some not yet. One of these is our previous research on plasma waves, which originated in the early 80＇s at the Plasma Physics Laboratory of the NCSR ＂Demokritos＂. As the wave rising is defined by the growth rate （or the damping on the extinguishment）, these important wavy quantities will be studied in detail in the present paper. Three examples are taken from our previous theoretical results, and the first observation reveals that the involved quantities are complicated enough to be studied by themselves. So, the use of suitable approach models, which may interpret the experimental wavy quantities, is the central idea of the present attempt, Furthermore, calculations with a little change of the initial conditions have been repeated in order to determine whether the plasma behaves as a chaotic medium.