• Title/Summary/Keyword: volume size distribution

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Analysis of e-Learning Server Workload (e-Learning 서버 작업부하 분석)

  • Son, Sei-Il;Kim, Heung-Jun;Ahn, Hyo-Beom
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.8 no.1
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    • pp.65-72
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    • 2007
  • This paper aims to provide information to generate a statistical load model of an educational server by analyzing workload of an e-Learning sewer at Dankook University. The result of the analysis shows file size distribution, access frequency and transmission volume for each file type, access interval, changes in preference and clients access rate by networks. In particular, it had different results from previous studies about video file's size distribution and file distribution based on access frequency. This is because the characteristics of e-learning are influenced by using authoring tools for making into video file and by freeing the number of students who register for a course. The result in this paper can be used as a basic data for studies designed to improve e-learning system architecture and server performance.

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Study of Aluminum Agglomeration Model During Solid Propellant Combustion (고체추진제 연소 중 알루미늄 응집 모델 연구)

  • Yoon, Jisang;Lee, Kookjin;Kim, Daeyu;Park, Namho;Ko, Seungwon;Yoon, Woongsup
    • Journal of the Korean Society of Propulsion Engineers
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    • v.23 no.2
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    • pp.78-86
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    • 2019
  • Aluminum, which is a metal fuel contained in the composite solid propellant, is not ignited and burned on the combustion surface by the oxide film, and it partially melts and coalesces with surrounding aluminum particles. For the evaluation and design of the propellant performance, modeling was performed to predict the size and distribution of agglomerated particles, and the size and distribution of agglomerates were compared and verified through experiment. The predicted values showed the tendency to decrease with pressure as in the experiment, but the error increased as the pressure increased. The agglomerated particle distribution graph showed a difference in the volume fraction although the diameter at the peak was the same.

Analysis of Correclations between Flow Rate, Pressure and Average Size of Droplet with Hydraulic Diameter of Water Curtain Nozzle (수막설비용 노즐의 수력직경 변화에 따른 방사유량, 방사압 그리고 액적의 평균 크기 상관관계 분석)

  • Park, Jung Wook;Shin, Yeon Je;You, Woo Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.4
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    • pp.317-323
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    • 2020
  • In this study, the correlations between flow rate, exhaust pressure, and droplet mean diameter with the shape factor of a water curtain nozzle were investigated. To analyze the flow coefficient and the distribution constant on the effects of the hydraulic diameter, five nozzles (D5W3, D5W6, D5W8, D4W6, and D7W6) were mocked up with a consideration of the internal diameter and width. The results showed that the flow coefficient increased in proportion to the constant 0.79 and 62.8 of the hydraulic diameters according to the diameter. As the nozzle width increased, the average droplet size decreased to the -0.235 exponential of the pressure. The average volume was reduced, in which the size distribution of the volume indeterminate decreased with increasing pressure for the same nozzle of the water-curtain. The distribution constants of droplet increased in proportion to the 0.258 exponential of the hydraulic diameter and 244.21. These results are expected to be useful to the design of pressure, flow meter, and average droplet size from a water curtain nozzle to predict the flow characteristics.

Effect of Soaking on Expansion Volune of Gang Jung (찹쌀의 수침이 강정의 팽화부피에 미치는 영향)

  • Park, Young-Mee;Oh, Myung-Suk
    • Korean Journal of Food Science and Technology
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    • v.17 no.6
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    • pp.415-420
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    • 1985
  • In this study, changes in physical and chemical properties of glutinous rice during various soaking periods (0, 0.08, 1, 3, 5, 7, 10 days) were investigated in order to clarify the relations ship between soaking period and expansion volume in the preparation of Gang Jung. The longer the soaking period was, the greater the expansion volume of Gang Jung was. Higher maximum viscosity and breakdown in amylogram of glutinous rice flour were observed as the soaking period was increased, As the length of soaking period increased, hardness of glutinous rice and size of flour particle significantly decreased, while sweeling power and solubility of glutinous rice flour showed no significant difference. Increased length of soaking period was associated with higher fatty acidity, higher acidity of water extract and lower pH of glutinous rice flour. Control of flour particle size distribution resulted in significantly larger expansion volume of Gang Jung. Brabender's amylogram showed that the increase of expansion volume of Gang Jung associated with the increase of soaking period was related to the change of rheological properties of glutinous rice. It seemed that changes in viscometric properties of glutinous rice was attributed to the different flour particle size distribution resulted from changes in hardness of rice during soaking.

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Effect of particle size of rice flour on popping rice bread (쌀가루 입도가 쌀 식빵의 팽화에 미치는 영향)

  • Park, Mi-Kyung;Kang, Soon-Ah;Lee, Kyung-Hee
    • Korean journal of food and cookery science
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    • v.22 no.4 s.94
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    • pp.419-427
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    • 2006
  • The purpose of this study is to promote the substitution of rice flour for wheat flour in making bread and thus the consumption of rice by examining the effect of particle size of rice flour on leavening rice bread. For this purpose, several experiments were carried out. With regard to particle size distribution, 59.45% of wheat flour had passed 200 mesh and 3 kinds of rice flour milled to penetrate into 20, 35, and 45 mesh (S1, S2 and S3) had passed 21.88%, 33.1% and 36.38% of those for 200 mesh, respectively. To leaven the rice flour dough to bread, 25% of vital gluten was needed. To determine the optimal water quantity for rice bread dough, the hardness of wheat and rice flour dough was measured by rheometer. The appropriate water quantity for S1, S2 and S3 was set at 285 ml , 295 ml and 335${\sim}$340m1, respectively. The loaf volume index of the wheat flour bread was 6.24, while that of and rice flour bread S1, S2 and S3 was 5.38, 5.50 and 5.75, respectively. These results indicated that the loaf volume index of rice flour bread is lower than that of wheat flour bread, but that the volume of rice flour bread was increased with fuel particle size of rice flour. Scanning electron microscopy (SEM), image of the wheat bread tissue at a magnification of 35 times showed long, large, oval-shaped, air cells and thin cell membrane, as well as small air cells, whereas the images of rice flour showed angular, circular, air cells and rough and thick cell membrane. The size and number of air cells in the rice bread were larger in S2 and S3 with fuel particle flours than in S1. In particular, the bread made with S3 contained many air cells that were as large as those in the wheat bread were. In addition, when the inner cell wall was magnified 1500 times, almost no small air cell was observed in C and S3, whereas many fine air cells were observed in the cell wall of S1 and S2.

Effect of Substrate Porosity on Double Coating Structure (기질의 공극성의 이중 도공 구조에 미치는 영향)

  • 김병수;박중열;정현찬
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.30 no.4
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    • pp.79-84
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    • 1998
  • The process of double coating consists of bottom coating using relatively coaser pigments to improve characteristics of base paper and top coating using finer pigments to cover unevenness of the bottom coating and to give various function of the coated paper. The structure of precoating is influenced not only by its components, but also characteristics of base paper, Moreover pore size and its size distribution of precoating are expected to influence the top coating properties, but this is not well understood. Coating and printing operations involve the application of pigmented fluid on top of a porous substrate. The porosity of the substrate has been shown to influence the properties of the coating, but a good understanding of the mechanisms is lacking in the literature. The role of pore size and void volume on top coating structure is unclear.

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A Simulation Method for Modeling the Morphology and Characteristics of Electrospun Polymeric Nanowebs

  • Kim Hyungsup;Kim Dae-Woong;Seo Moon Hwo;Cho Kwang Soo;Haw Jung Rim
    • Macromolecular Research
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    • v.13 no.2
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    • pp.107-113
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    • 2005
  • We developed an algorithm to simulate the generation of virtual nanowebs using the Monte Carlo method. To evaluate the pore size of the simulated multi-layered nanoweb, an estimation algorithm was developed using a ghost particle having zero volume and mass. The penetration time of the ghost particle through the virtual nanoweb was dependent on the pore size. By using iterative ghost particle penetrations, we obtained reliable data for the evaluation of the pore size and distribution of the virtual nanowebs. The penetration time increased with increasing number of layers and area ratio, whereas it decreased with increasing fiber diameter. Dimensional analysis showed that the penetration time can be expressed as a function of the fiber diameter, area ratio and number of layers.

Dyeing Study on DMF-Modified Polyesters for Morphology Characterization

  • Park, Myung-Ja
    • The International Journal of Costume Culture
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    • v.5 no.2
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    • pp.53-65
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    • 2002
  • Morphology of polyester fiber was physically modified by solvent treatment. PET fiber was treated with N,N-dimethylformamide (DMF) at 100, 120, $140^{circ}C$ for 10 minutes without tension. The structural changes in the morphology of DMF-induced modified PET fiber were FTIR and SEM analysis. Also dyeing behavior of DMF-treated polyester fibers with various disperse dyes was studied to detect changes of amorphous area in fine structure. DMF treatment resulted in increases in total void content, degree of crystallinity, trans isomer content, chain folding, segmental mobility and molecular packing, but it resulted in decreases in amorphous orientation, intermolecular forces and individual void size through longitudinal shrinkage, lateral welling and removal of oligomers. Void-size distribution could be estimated from the dye uptake with various sizes of disperse dyes. In contrast to the large increases in dye uptake with small dye molecules, there is no and little dye uptake with the bulkiest dye, which means that void size is bigger or smaller than the volume of each dye. Diffusion rates of dye molecules showed increases. This dyeing study revealed that the disperse dyeing is very effective method for characterizing the internal morphology of polyester fiber.

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Polymeric Micelle Formation of Multiblock Copolymer Composed of Poly( $\gamma$-benzyl L-glutamate) and Poly(ethylene oxide)

  • Na, Jae Un;Jeong, Yeong Il;Jo, Jong Su
    • Bulletin of the Korean Chemical Society
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    • v.21 no.4
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    • pp.383-388
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    • 2000
  • Multiblock copolymers consisting of poly( g-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part (GEG) were synthesized and characterized. GEG polymeric micelles were prepared by the dialysis technique. Particle size distributions based on intensity,volume, and number-average were 22.6 $\pm$ 11.9 nm, 23.5 $\pm$ 4.6 nm, and 23.7 $\pm$ 37 nm, respectively. It was observed that par-ticle size and size distribution of GEG polymeric micelles changed significantly with the choice of initial sol-vent. Transmission electron micrographs (TEM) showed the polymeric micelles to be spherically shaped, with sizes ranging from 20 nm to 40 nm in diameter. Fluorescence spectroscopy measurements suggested that GEG block copolymers wereassociated in water to form polymeric micelles, and the critical micelle concentrations (CMC) value of the block copolymers was 0.0094 g/L. Further evidenceof micelle formation of GEG block copolymers and limited mobility of the PBLG chain in the core ohe micelle was obtained with 1 H NMR in D2O.

3-Dimensional Calculation on Cold Air Flow Characteristics in a Refrigerator (냉장고 내부의 냉기 유동특성에 관한 3차원 해석(I))

  • Oh, Min-Jung;Lee, Jae-Heon;Oh, Myung-Do
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.3
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    • pp.382-395
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    • 1995
  • A numerical study has been performed on flow characteristics in a domestic refrigerator whose size is $540mm{\times}1,530mm{\times}680mm$, considering existence of a fan and evaporator. The flow field has been simulated with the low Reynolds number $k-\bar{\varepsilon}$ turbulent model and SIMPLE algorithm based on the finite volume method. The region of fan which makes driving force for cold air distribution was modeled as a region in which momentum sources are generated uniformly. The concept of the distributed pressure resistance was applied to describe the momentum loss from evaporator. The result showed that the rate of cold air distribution into freezing room and cold storage room was almost 7 : 3.

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