• Title/Summary/Keyword: Log-normal Particle Size Distribution

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Mapping Particle Size Distributions into Predictions of Properties for Powder Metal Compacts

  • German, Randall M.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.704-705
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    • 2006
  • Discrete element analysis is used to map various log-normal particle size distributions into measures of the in-sphere pore size distribution. Combinations evaluated range from monosized spheres to include bimodal mixtures and various log-normal distributions. The latter proves most useful in providing a mapping of one distribution into the other (knowing the particle size distribution we want to predict the pore size distribution). Such metrics show predictions where the presence of large pores is anticipated that need to be avoided to ensure high sintered properties.

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Yellow Sand Phenomena Influence to the Atmosphere in Korea (黃砂現象이 우리나라에 미치는 影響)

  • 이민희;한의정;원양수
    • Journal of Korean Society for Atmospheric Environment
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    • v.2 no.3
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    • pp.34-44
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    • 1986
  • Particle size distribution of airborne suspended particulate concentrations according to particle size in the events of yellow sand phenomena, have been measured and analyzed by using Andersen air sampler for four years, January 1982 through December 1985. The conclusions are as follows: 1. Yellow sand phenomena, generally, occur between March and May. 2. The frequent occurrences of yellow sand were observed during March and April and airborne suspended particulate concentrations in the cases of yellow sand appeared to be 2 $\sim$ 3.4 times higher than those of normal conditions. 3. Geometric mean particle diameter and its geometric mean standard deviation by logarithmic normal distribution sheet, were quite close to each other and log-distribution curves showed similar shapes. 4. Analysis by particle size distribution curve showed bi-modal distribution. 5. Concentrations of coarse particles in normal conditions were 1.2 $\sim$ 2 times higher than those of fine particles and, similarly, coarse particle concentrations in yellow sand cases were 1.3 $\sim$ 2.5 times higher than those of fine particles. 6. Concentrations of coarse particles in yellow sand cases were 2 $\sim$ 3.6 times higher than those in normal conditions and those of fine particles were 1.7 $\sim$ 3.5 times higher.

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A Study on Evaluation for Sampling and Analytical Methods of Diatomaceous Earth Dust (규조토 분진 측정 및 분석 방법의 비교에 관한 연구)

  • Lim, Hyun Sul;Kim, Ji Yong;Cheong, Hoe Kyeong
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.5 no.2
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    • pp.212-225
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    • 1995
  • This study was performed in a diatomite factory located at Pohang City, Kyeongsangbuk-Do. The major objectives were to evaluate sampling and analytical methods of diatomaceous earth dust. Concentrations of total and respirable diatomaceous earth dust were measured. Size distribution of dust was analyzed by a personal cascade impactor and the particle size analyzer which is an application of multiple diffraction method. Also crystalline silica in respirable and total dust samples was analyzed quantitatively by X-ray diffraction and Fourie Transform Infrared Spectroscopy(FTIR). The results were as follows: The airborne total and respirable dust concentrations, particle size distribution, and cristalline silica(quartz) concentrations showed approximately a log-normal distribution. The means of totaldust concentrations at flour maufacturing, fire brick grinding and packaging processes exceeded the Korean and American Conference of Governmental Industrial Hygienists standards, $10mg/m^3$. The size distribution of diatomaceous earth dust was log-normal and identified as the rspirable particle mass and thoracic particle mass. The crystalline silica in respirable and total dust samples was identified to quartz and contained about 10 % in those samples. Finally, it is necessary to study the applicability of multiple diffraction for particle size distribution to compare the ACGIH's size selective sampling with other materials containing crystalline silica. Also, advanced quantitative study to X-ray diffraction and FTIR methods shoud be carried out 10 verify general and specific characteristics for respirable crystalline silica.

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Effect of Particle Size Distribution on the Sensitivity of Combustion Instability for Solid Rocket Motors (입자 크기 분포도를 고려한 고체로켓 모터의 연소 불안정 민감도 예측)

  • Joo, Seongmin;Kim, Junseong;Moon, Heejang;Ohm, Wonsuk;Lee, Dohyung
    • Journal of the Korean Society of Propulsion Engineers
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    • v.19 no.5
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    • pp.37-45
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    • 2015
  • Prediction of combustion instability within a solid-propellant rocket motor has been conducted with the classical acoustic analysis. The effect of particle size distribution on the instability has been analyzed by comparing the log-normal distribution to the fixed mono-sized particle followed by a survey of motor length scale effect between the baseline model and small scale model. Particle damping effect was more efficient for the small scale motor which has a relatively high unstable mode frequencies. It was also revealed that the prediction results by considering the particle size distribution show an overall attenuation of fluctuating pressure amplitude with respect to the mono-sized case.

Determination of the Size Distribution of Magnetite Nanoparticles from Magnetic Measurements

  • Yoon, Sung-Hyun
    • Journal of Magnetics
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    • v.16 no.4
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    • pp.368-373
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    • 2011
  • Particle size distributions in 10 nm magnetite ferrofluids are analyzed based on both dc and ac magnetic measurements. Modified log-normal distributions are used for fitting the experimental results, which allows for a proper account of the narrow distributions. The calculated average particle sizes are in good agreement with the TEM results. However the ac method gives a much narrower distribution width than that of the dc magnetization curve fit. The proposed measurements combined with the analysis methods are useful for the characterization of ferrofluids being considered for biomedical applications.

Analysis of Electrical Coagulation of Unipolar Charged Particles in an Alternating Electric Using Moment Method (모멘트법을 이용한 AC 전기장 내의 단극성 입자의 전기응집 해석)

  • Ji, Jun-Ho;Hwang, Jeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.1
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    • pp.9-17
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    • 2001
  • A numerical study has been carried out on the evolution of the particle size distribution for unipolar charged particles that experience coagulation in an alternating electric field. The collision frequency function of charged particles was analytically derived. The log-normal size distribution function is utilized for representing a poly-disperse size distribution and the moments of the particle size distribution are used to solve the general dynamic equation considering only AC electric force effect. The results are compared with the effects of brownian coagulation.

Recent Development of Analytical Solutions to Brownian Aerosol Coagulation in Different Particle Size Regimes

  • Park, Seong-Hun;Kim, Hyun-Tae;Lee, Kyoo-Won
    • Journal of Korean Society for Atmospheric Environment
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    • v.15 no.E
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    • pp.65-71
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    • 1999
  • The log-normal size distribution theories developed recently for aerosol coagulation are reviewed. The analytical solutiosn to Brownian coagulation developed recently for various particle size regimes are reviewed. In order to describe the evolution of the size distribution of a coagulating aerosol over the entire size range, the analytical solutions developed individually for the free-molecule regime, the transition regime, the nearcontinuum regime, and the continuum regime have been combined. The work described here represents the first analytical solution to the aerosol coagulation problem covering the entire particle size range.

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Experimental and Numerical Study of Aerosol Coagulation by Gravitation (에어로졸 입자의 중력응집에 관한 실험 및 수치적 연구)

  • 권순박;이규원
    • Journal of Korean Society for Atmospheric Environment
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    • v.16 no.1
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    • pp.1-10
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    • 2000
  • The behavior of aerosos due to gravitational coagulation was studied experimentally and numerically. In experimental study, the geometric mean particel size increased as time elapsed in a vertical tube column, while the size decreased when the tube was set horizontally. The particle size distribution was observed to maintain the lognormal form during the coagulation process. Separately, numerical calculations were performed for studying the aerosol behavior under gravitational and Brownian coagulation using the moment method. By comparing the expeimented results with the numerical predictions, the governing mechanism of the aerosol behavior proved to be gravitational coagulation.

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Condensational Growth of Fine Aerosol Particles to Increase Precipitation Efficiency (집진효율 향상을 위한 미세 에어로졸 입자의 응축에 의한 성장 연구)

  • Han, Sang-Woo;Hwang, Jung-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.8
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    • pp.1069-1076
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    • 2000
  • As the environmental problems grow, the regulation of the pollutants emitted from power plants increases. Most of the pollutants in particle phase are removed by particle removal facilities, but fine particles between 0.1 micron and I micron in diameter have a low removal efficiency compared to particles in other size ranges. Therefore the present concern has concentrated on the removal of those fine particles. The purpose of this study is to grow fine particles by condensation to the range larger than I micron. Theoretically the general dynamic equation is solved with an assumption that the particle size follows a log-normal distribution to calculate the temporal behavior of the size distribution. Experiments have been carried out to compare the results with the theoretical predictions. Particles grown by condensation are sampled by impactors and observed with SEM photographs.

Dilutant flow characteristics model of coarse particle suspensions with uniform size distribution

  • Ookawara, Shinichi;Ogawa, Kohei
    • Korea-Australia Rheology Journal
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    • v.15 no.1
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    • pp.35-41
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    • 2003
  • It is expected that particle size distribution of any portion obtained through screening, is of more uniform than that of the original mixture, typically following such as log-normal, Rosin-Rammler distributions and so on. In this study, therefore, a new relation between parameters of the uniform distribution and flow characteristics of the coarse particle suspensions is derived based on the continuous polydisperse model (Ookawara and Ogawa, 2002b), which is derived from the discrete polydisperse model (Ookawara and Ogawa,2002a). The derived model equation predicts a linear increase of viscosity with shear rate, viz., dilutant flow characteristics. Further, the increase of viscosity is expected to be proportional to the square of volume fraction of particles, and to show the linear dependency on density and average diameter of particles. It is also shown that the uniform distribution model includes additional term that expresses the effect of distribution width. For verification of the model, the experimental results of Clarke (1967) are cited as well as in our previous work for the monodisperse model (Ookawara and Ogawa,2000) since most parameters were varied independently in his work. It is suggested that the newly introduced term expands the applicable range compared with the monodisperse model.