Measurements Of Concentration Distribution Research Articles

マイクロリアクター内の反応生成物濃度分布計測への２色法の適用

マイクロリアクター内の反応生成物濃度分布計測への２色法の適用

G702 キャパシタンスCTを用いた鉛直管内流動層の濃度分布計測(1)(GS7 様々な流体,反応流,一般セッション)

G702 キャパシタンスCTを用いた鉛直管内流動層の濃度分布計測(1)(GS7 様々な流体,反応流,一般セッション)

G702 キャパシタンスCTを用いた鉛直管内流動層の濃度分布計測(2)(GS7 様々な流体,反応流,一般セッション)

G702 キャパシタンスCTを用いた鉛直管内流動層の濃度分布計測(2)(GS7 様々な流体,反応流,一般セッション)

OS10-5 固液二相流濃度分布測定のためのレジスタンスCTの開発(OS10 混相流の計測技術と解析,循環型社会における動力エネルギー技術)

OS10-5 固液二相流濃度分布測定のためのレジスタンスCTの開発(OS10 混相流の計測技術と解析,循環型社会における動力エネルギー技術)

Model and real pollutant dispersion: concentration studies by conventional analytics and by laser spectrometry

The differential absorption LIDAR together with spot analyzers (infrared absorption and chemiluminescence method) was used for concentration measurements in an urban street canyon in Prague. Measurements in the real atmosphere were compared with measurements of concentration distribution inside a model. Experiments in a wind-tunnel-simulated atmosphere were carried out using laser photoacoustic spectrometry and the laser visualization method. A comparison of concentrations on the windward and leeward sides of the model and real street canyon was performed.

Quasi 2-D Measurements of Gaseous and Liquid Fuel Concentrations Using Two-Color Laser Beam Scanning Technique

Planer Laser Induced Fluorescence (PLIF) has been employed to measure the spatial liquid and vapor fuel concentration distributions, although it is generally difficult to achieve quantitatively accurate measurement. The authors devised a 2-D fuel spray concentration distribution measurement method which combines three optical principles; absorption, fluorescence, and scatter. NO2 gas was used as a fluorescence dopant while Ar+ laser was employed as a light source by scanning across the cylinder in order to measure the spatial fuel concentration distribution. This technique was applied to gaseous jets and swirl sprays. Quantitative measurement was successfully achieved in both tests. Also, the characteristics of liquid and vapor fuel concentration distribution using a swirl type injector were confirmed.

Change in spectra of mobility of small atmospheric ions during convection and diffusion

The change in spectra of mobility of small atmospheric ions during molecular diffusion and convection in air has been studied experimentally. There occurs no change in mobility spectra for the molecular diffusion in windless air because both coefficients of adhesion and diffusion are proportional to the mobility. On the other hand, the mobility spectrum of ions changes during the convections due to the inverse proportionality of the lifetime to the mobility of ions. The mean lifetime of ions was experimentally obtained from the measured concentration distribution of ions in a round free jet. The results showed that the mobility spectrum of ions changes with increasing downstream distance due to a rapid dissipation of the ions of high mobility during the convections.

Luminescence technique for the measurement of local concentration distribution in thin liquid films

Experimental data of the concentration field with high spatiotemporal resolution is required for the comprehension of mass transfer increasing kinetic phenomena in falling liquid films. For this purpose a non-invasive measuring method based on luminescence indicators is developed. It is used to determine the concentration distribution and the local film thickness simultaneously. First results are presented for the oxygen absorption into a laminar-wavy water film flowing down a plane with an inclination angle of 4° and a liquid side Reynolds number of 177. With the measured concentration distributions the effective diffusion coefficients are calculated at three points in a single wave of the film.

Log-stable concentration distributions of trace elements in biomedical samples

In the present paper, which follows our earlier observation that the asymmetric and long-tailed concentration distributions of trace elements in biomedical samples, measured by the X-ray fluorescence techniques, can be modeled by the log-stable distributions, further specific aspects of this observation are discussed. First, we demonstrate that, typically, for a quite substantial fraction (10–20%) of trace elements studied in different kinds of biomedical samples, the measured concentration distributions are described in fact by the “symmetric” log-stable distributions, i.e. the asymmetric distributions which are described by the symmetric stable distributions. This observation is, in fact, expected for the random multiplicative process, which models the concentration distributions of trace elements in the biomedical samples. The log-stable nature of concentration distribution of trace elements results in several problems of statistical nature, which have to be addressed in XRF data analysis practice. Consequently, in the present paper, the following problems, namely, (i) the estimation of parameters for stable distributions and (ii) the testing of the log-stable nature of the concentration distribution by using the Anderson–Darling ( A 2) test, especially for symmetric stable distributions, are discussed in detail. In particular, the maximum likelihood estimation and Monte Carlo simulation techniques were used, respectively, for estimation of stable distribution parameters and calculation of the critical values for the Anderson–Darling test. The discussed ideas are exemplified by the results of the study of trace element concentration distributions in selected biomedical samples, which were obtained by using the X-ray fluorescence (XRF, TXRF) methods.

Simulation of the Dispersion of Radioactive Effluents over the Kori site using Field Tracer Experiment

Field tracer experiments have been conducted at the Kori nuclear site for the purpose of analyzing the site-specific atmospheric dispersion characteristics and validating a real-time radiological dose assessment system FAD AS. Field tracer experiments were performed for three years from 2000 to 2002. Tracer gas SF6 was released at the top of the meteorological tower of the site and sampled by 140 automatic sequential gas samplers. The samplers were disposed at sampling points along the traffic roads around the site. The coordinates of all the sampling points were investigated by GPS. The concentration of the sampled gas was analyzed by gas chromatography. And the measured concentration distribution was compared with the distribution simulated by FAD AS. During the experiments, meteorological data was measured at several sampling points including the release point. The measured meteorological data were used for the numerical simulation by FAD AS. The comparative study between the measured and the simulated concentration was conducted. Due to the effects of the complex terrain of the Kori site, the degree of agreement between the measure and the simulated concentration is somewhat lower than that of the site of a flat terrain. The analysis of the site-specific field tracer experiment provides the useful information for the realistic application of an atmospheric dispersion model for a nuclear site.

Direct methanol fuel cell (DMFC): analysis of residence time behaviour of anodic flow bed

This paper studies the residence time behaviour and concentration distribution in a simplified rhomboidal DMFC anode flow bed by 3D numerical flow simulations and by experimental measurements. The rhomboidal DMFC anode flow bed and the applied volume flow are discussed with regard to data given in the literature. Simulations with CFX, based on Finite Volume Method, and MooNMD, based on Finite Element Method, show strongly similar results and the reliability of the computed residence time distributions (RTD) is proved by showing that they depend only slightly on parameters of the numerical schemes applied. The realisation of the RTD and concentration distribution measurements are described. Experimentally obtained RTD results are in good agreement with the numerical simulations. Also, the experimentally obtained concentration distribution inside the anode flow bed is very similar to the computed distribution. By analysing the RTDs and concentration distributions, the obtained results provided evidence of weaknesses of the flow bed design.

Concentration distribution of trace elements: from normal distribution to Lévy flights

The paper discusses a nature of concentration distributions of trace elements in biomedical samples, which were measured by using the X-ray fluorescence techniques (XRF, TXRF). Our earlier observation, that the lognormal distribution well describes the measured concentration distribution is explained here on a more general ground. Particularly, the role of random multiplicative process, which models the concentration distributions of trace elements in biomedical samples, is discussed in detail. It is demonstrated that the lognormal distribution, appearing when the multiplicative process is driven by normal distribution, can be generalized to the so-called log-stable distribution. Such distribution describes the random multiplicative process, which is driven, instead of normal distribution, by more general stable distribution, being known as the Lévy flights. The presented ideas are exemplified by the results of the study of trace element concentration distributions in selected biomedical samples, obtained by using the conventional (XRF) and (TXRF) X-ray fluorescence methods. Particularly, the first observation of log-stable concentration distribution of trace elements is reported and discussed here in detail.

Comparative study of trace element contents in human full-term placenta and fetal membranes by total reflection X-ray fluorescence

The total reflection X-ray fluorescence (TXRF) method was applied to study the influence of environmental pollution on the contents of trace elements in human full-term placenta and fetal membranes. The samples were collected from the donors living in two regions characterised by different levels of environmental pollution. In this comparative study, based on relatively large (∼100) populations, the concentrations of approximately 20 trace elements (P–Pb) were determined in the samples. In particular, the paper discusses the role of ‘truncation’ of measured concentration distribution by the detection limit of the TXRF method in context of comparative studies. First, the importance of the developed method of reconstruction of original concentration distribution, to derive the correct concentrations of trace elements, is described and demonstrated and, second, the statistical tests, which can be used to compare the truncated, or reconstructed, concentration distributions are discussed. Finally, the statistically significant differences of trace element concentrations found in both populations are presented and summarised.

Direct Measurement of Concentration Distribution within the Boundary Layer of an Ion-Exchange Membrane

In this study the concentration distributions within the diffusion boundary layer were obtained by directly measuring the potential drops while the currents (under- and overlimiting) passed through the Neosepta CMX cation-exchange membrane (Tokuyama Corp., Japan). Potential drops according to the distance from the membrane surface on the depleted side were measured using a microelectrode to obtain the concentration profile. From the concentration profiles obtained, it was observed that the diffusion boundary layers existed in the range of 300–350 μm, which reasonably coincide with the theoretical diffusion boundary layer thickness calculated from the limiting current density. Although there were some deviations between the concentrations determined from the Nernst model and those from experiments, it was confirmed that the Nernst model effectively depicts the transport phenomena in the ion-exchange membrane system. In addition it was found that the salt concentration at the membrane surface increased when the currents applied exceeded the limiting current. It is thought that the concentration polarization formed in the diffusion boundary layer at currents near or lower than the limiting current was disturbed by a turbulent convection when the current was greater than the limiting current. As a consequence, the concentration at the membrane surface increased to a sufficient level for generation of the overlimiting current.

A mixture model for the PDF of a diffusing scalar in a turbulent flow

This paper offers physical and statistical arguments that lead to the representation of the probability density function of a scalar diffusing in a turbulent flow as a mixture of two probability density functions. Particular attention is given to the high-concentration tails which are consistently observed to be described accurately by a generalized Pareto distribution. A 4-parameter construct, using a mixture of beta densities, is shown to provide an adequate representation of measured concentration distributions of wind-tunnel, grid turbulence, plume data. By using either measured or theoretically predicted moments to conduct statistical inference, it is expected that the proposed model will be flexible enough to apply to a wide variety of experimental data sets, including those obtained from large-scale environmental flows.

Modelling the effects of groyne fields on the transport of dissolved matter within the Rhine Alarm-Model

The influence of artificial dead zones, such as groyne fields, on the transport of a spill in a river has been analysed. For this purpose, tracer experiments executed in the Dutch Rhine branches in the framework of the development of the Rhine Alarm-Model were used. Additionally for low water discharges with a suppressed flow in the Lower-Rhine River, measured concentration distributions of a few accidental spills were considered. In the Rhine Alarm-Model a lag coefficient applied to the convective transport of a spill represents the influence of the groyne fields. In the case of a complete exchange of the groyne field with the main stream, this coefficient is equal to the ratio between the cross-sectional areas of the groyne field and the main stream of the river. It is shown that this is correct to a certain extent for the Dutch Rhine branches Waal and Lower Rhine. However, in the case of low water discharges the influence of the groyne fields can reduce considerably. To explain these reductions, fundamental research of the mass exchange processes between groyne fields and main stream is needed.

Measurements and evaluation of concentration distributions in filter cake formed in dead-end ultrafiltration of protein solutions

To clarify the internal structures of the filter cake formed on the membrane surface in protein ultrafiltration, a method has been developed for measuring the variations of protein concentration across the filter cake on the basis of the principle of inclined ultrafiltration, where the membrane was inclined and a large amount of filter cake was formed, and the results were compared with the calculations based on a compressible cake filtration model, which explicitly took the non-homogeneity and the compressibility of the filter cake into account. The experimental results obtained from ultrafiltration of bovine serum albumin (BSA) solutions under constant pressure conditions clearly demonstrated that the filter cake tended to have a much more compact structure at the membrane in comparison with a relatively loose condition at the surface. It was also found that the thickness of the filter cake formed on the membrane increased as the filtration progressed. Further, the effects of pH and the solute concentration in the feed solution on the structure of the filter cake have been examined experimentally. The measured concentration distributions accorded well with the calculated results based on a compressible cake filtration model. This study revealed that the dynamic deposition behaviors of the protein molecules in dead-end ultrafiltration could be accurately described by a compressible cake filtration model.

Influence of detection limit on the measured concentration distribution of trace elements

AbstractThe concentration distributions of trace elements in large populations (n > 100) of biomedical samples were studied by x‐ray fluorescence spectrometry. For elements, the concentrations of which measured in all samples exceed the detection limit (DL) of the method, the log‐normal distribution was found to describe the data very well. For other elements, measured in only a fraction of the studied population, the observed distributions were truncated by the variable DL level. We demonstrate, however, that by using the information on the distribution of reported detection limits, the original distributions of concentration, and also the detection limits, can be reconstructed from the measured data. This can be done by solving the system of integral equations relating the measured and original distributions of the concentration and the detection limit. The applicability of this method is demonstrated in a comparative study of trace element concentrations in urine samples. Copyright © 2001 John Wiley & Sons, Ltd.

Field tracer experiments over nuclear sites for the validation of a Korean real-time atmospheric dispersion and dose assessment system (FADAS)

A real-time atmospheric dispersion and dose assessment system (FADAS) has been developed. It has been used as a basic tool to monitor the atmospheric dispersion of released radioactive materials and radiological dose assessment to the national emergency preparedness system, CARE, since 1995. Tracer experiments have been conducted for the purpose of validating FADAS and analysing the environmental characteristics using automatic sequential samplers. The measured concentration distributions were compared with those simulated by FADAS. Both concentration distribution patterns agreed well.

PALLAS: a novel optical measurement technique in air pollutant transport studies

This paper presents the principles of a novel laser optical method in the measurement of concentration distribution of air pollutants. It is based on a concerted application of panoramic annular lens (PAL) optical detection system and a laser sheet illumination equipment (PALLAS). The PAL optic provides full 360° angle of panoramic view information. This is the most important property which makes the PALLAS especially suitable for extensive investigation of concentration field around models of buildings and features of terrain. This paper presents the advantages of this system in comparison to the conventional laser sheet technique. The first results are also presented and measurement technical improvement of PALLAS method is summarised.