• 제목/요약/키워드: size and scale

검색결과 3,374건 처리시간 0.025초

입자 크기의 함수로 나타낸 대기 중 블랙카본의 변성시간척도 (Particle-size-dependent aging time scale of atmospheric black carbon)

  • 박성훈
    • 한국입자에어로졸학회지
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    • 제5권2호
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    • pp.45-52
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    • 2009
  • Black carbon, which is a by-product of combustion of fossil fuel and biomass burning, is the component that imposes the largest uncertainty on quantifying aerosol climate effect. The direct, indirect and semi-direct climate effects of black carbon depend on its state of the mixing with other water-soluble aerosol components. The process that transforms hydrophobic externally mixed black carbon particles into hygroscopic internally mixed ones is called "aging". In most climate models, simple parameterizations for the aging time scale are used instead of solving detailed dynamics equations on the aging process due to the computation cost. In this study, a new parameterization for the black carbon aging time scale due to condensation and coagulation is presented as a function of the concentration of hygroscopic atmospheric components and the black carbon particle size. It is shown that the black carbon aging time scale due to condensation of sulfuric acid vapors varies to a large extent depending on the sulfuric acid concentration and the black carbon particle size. This result indicates that the constant aging time scale values suggested in the literature cannot be directly applied to a global scale modeling. The aging time scale due to coagulation with internally mixed aerosol particles shows an even stronger dependency on particle size, which implies that the use of a particle-size-independent aging time scale may lead to a large error when the aging is dominated by coagulation.

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수직응력과 압입이론에 기반한 나노스케일 기계가공에서의 크기효과 분석 (Analysis of Size Effect of Nano Scale Machining Based on Normal Stress and Indentation Theories)

  • 전은채;이윤희;제태진
    • 한국기계가공학회지
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    • 제17권6호
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    • pp.1-6
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    • 2018
  • Recently nano meter size pattern (sub-micro scale) can be machined mechanically using a diamond tool. Many studies have found a 'size effect' which referred to a specific cutting energy increase with the decrease in the uncut chip thickness at micro scale machining. A new analysis method was suggested in order to observe 'size effect' in nano scale machining and to verify the cause of the 'size effect' in this study. The diamond tool was indented to a vertical depth of 1,000nm depth in order to simplify the stress state and the normal force was measured continuously. The tip rounding was measured quantitatively by AFM. Based on the measurements and theoretical analysis, it was verified that the main cause of the 'size effect' in nano scale machining is geometrically necessary dislocations, one of the intrinsic material characteristics. st before tool failure.

Meal nutritional management status of daycare centers by size

  • Hye Won Kim
    • International Journal of Advanced Culture Technology
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    • 제11권3호
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    • pp.26-32
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    • 2023
  • In this study, we attempted to analyze the status of meal nutritional management at daycare centers and determine whether the need for improvement varies depending on their size. We divided into two groups based on the size of foodservice facilities. If meals for more than 50 people are provided at a time, they are classified as large-scale facilities (Large-scale group). If they are smaller, they are classified as small-scale facilities (Small-scale group). Dietitians visited each daycare center and checked 5 categories and 14 items. When comparing 5 categories, scores in the Small-scale group scored higher than those in the Large-scale group for 'Menu utilization' category. As a result of comparing the detailed 14 items, the scores of 'Indicate dietary information', 'Use menus suitable for those who are eligible for meals', and 'Posting menus by age in public places at foodservice facilities' were higher in the Small-scale group than in the Large-scale group. As such, there are differences in meal nutritional management according to the size of children's foodservice facilities therefore, it was found that customized education and management were needed according to the facilities' size.

Influence of shear preload on wave propagation in small-scale plates with nanofibers

  • Farajpour, M.R.;Shahidi, A.R.;Farajpour, A.
    • Structural Engineering and Mechanics
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    • 제70권4호
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    • pp.407-420
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    • 2019
  • In the present work, an attempt is made to explore the effects of shear in-plane preload on the wave propagation response of small-scale plates containing nanofibers. The small-scale system is assumed to be embedded in an elastic matrix. The nonlocal elasticity is utilized in order to develop a size-dependent model of plates. The proposed plate model is able to describe both nanofiber effects and the influences of being at small-scales on the wave propagation response. The size-dependent differential equations are derived for motions along all directions. The size-dependent coupled equations are solved analytically to obtain the phase and group velocities of the small-scale plate under a shear in-plane preload. The effects of this shear preload in conjunction with nanofiber and size effects as well as the influences of the elastic matrix on the wave propagation response are analyzed in detail.

보육시설의 실외놀이 환경에 대한 사용자 평가 및 요구조사 (A Study on the Needs and Estimation of Users in the Playground of Child Care Facilities)

  • 최목화;변혜령
    • 한국주거학회:학술대회논문집
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    • 한국주거학회 2008년도 춘계학술발표대회 논문집
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    • pp.386-392
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    • 2008
  • The purpose of this study is to clarify playground types by characteristics of playground environment in child care facilities, to analyze the needs and estimation of users according to playground types. The subjects of this study were care-givers, who assist outdoor play activities of children and manage safety in playground, to estimate adequateness of playground's environment to children's outdoor plays and to report needs. The data were collected by field measurement survey for clarification playground environments in 21 child care facilities and structured-questionnaire for estimation and needs of 181 care-givers in them. The major results showed the following. 1) The playgrounds were clarified to five type according to number of child and size of playground. The five types include A-type as large-scale facility/small-size playground, B-type as small-scale facility/large-size playground, C-type as small-scale facility/small-size playground, D-type as middle-scale facility/large-size playground, and E-type as large-scale facility/large-size playground. 2) The adequateness of playground environment of D-type were estimate higher than others. C-type were estimated lower than other types in size and outdoor play areas organization of playground. 3) The care-givers in D-type and E-type wanted to install various play equipments, but the care-giver in C-type didn't wanted to install play equipment. 4) The various outdoor play areas were needed in D-type.

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Investigation of the model scale and particle size effects on the point load index and tensile strength of concrete using particle flow code

  • Haeri, Hadi;Sarfarazi, Vahab;Zhu, Zheming;Hedayat, Ahmadreza;Marji, Mohammad Fatehi
    • Structural Engineering and Mechanics
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    • 제66권4호
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    • pp.445-452
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    • 2018
  • In this paper the effects of particle size and model scale of concrete have been investigated on point load index, tensile strength, and the failure processes using a PFC2D numerical modeling study. Circular and semi-circular specimens of concrete were numerically modeled using the same particle size, 0.27 mm, but with different model diameters of 75 mm, 54 mm, 25 mm, and 12.5 mm. In addition, circular and semi-circular models with the diameter of 27 mm and particle sizes of 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, and 1.27 mm were simulated to determine whether they can match the experimental observations from point load and Brazilian tests. The numerical modeling results show that the failure patterns are influenced by the model scale and particle size, as expected. Both Is(50) and Brazilian tensile strength values increased as the model diameter and particle sizes increased. The ratio of Brazilian tensile strength to Is(50) showed a reduction as the particle size increased but did not change with the increase in the model scale.

인구 집단의 스케일의 확장이 집단 비율 및 집단 크기 지각에 미치는 영향: 다수편향적 사회적 정보 활용을 중심으로 (On the Effect of Extended Human Group Scale in Perception of Group Ratio and Size at Majority-biased Social Learning)

  • 장재경 ;장대익
    • 인지과학
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    • 제34권1호
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    • pp.39-66
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    • 2023
  • 뉴미디어는 사회적 교류의 장을 인터넷으로 옮겨와 대규모 집단이 시공간의 한계를 뛰어넘어 한 곳에서 소통할 수 있게 만들었다. 최근 연구는 인간의 사회적 능력이 소셜 미디어를 통해 경험하는 확장된 집단 스케일을 따라가지 못하는 사례를 보고하기도 한다. 이러한 맥락에서, 본 연구는 인간의 사회적 정보 지각이 인구 집단 스케일의 확장에 영향을 받는지 다수편향 맥락에서 확인하였다. 인터넷 기반 과제를 통해 구성원의 수로 나타낸 집단 크기와 전체에서 특정 집단이 차지하는 집단 비율이 개인에게 지각되고 다수편향적 사회적 정보 활용에 영향을 주는 심리적 과정을 조사하였으며, 전체 집단 스케일의 확장에 각 과정이 영향을 받는지 살펴보았다. 집단 비율은 다수편향에 정적 영향을 주고 있으며, 그 관계는 비율 지각에 의해 부분매개 되었다. 전체 집단 스케일은 집단 비율과 비율 지각의 관계를 조절하지 않았다. 반면, 집단 크기와 다수편향의 상관은 유의하지 않았다. 전체 집단 스케일은 집단 크기 지각을 조절하였다. 전체 집단 스케일이 작은 조건에서 집단 크기와 크기 지각은 양적 상관을 나타냈지만, 전체 집단의 스케일이 확장된 조건에서 지각된 집단 크기는 유의미하게 작아졌고, 두 변수는 상관을 잃었다. 이러한 결과를 통해 집단 크기 지각과 관련된 심리 기제가 전체 집단 스케일의 확장에 제대로 반응하지 못하고 있음을 확인하였다. 나아가 집단 크기 정보를 처리하는 전문화된 심리 기제가 존재할 가능성과 다수편향이 특이적으로 받아들이는 자극의 형태를 진화심리적 관점에서 논하였다.

접촉 면적에 따른 나노/마이크로 마찰 특성 (Nano/Micro Friction with the Contact Area)

  • 윤의성;;공호성
    • Tribology and Lubricants
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    • 제21권5호
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    • pp.209-215
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    • 2005
  • Nano/micro friction with the contact area was studied on Si-wafer (100) and diamond-like carbon (DLC) film. Borosilicate balls of radii $0.32{\mu}m,\;0.5{\mu}m,\;1.25{\mu}m\;and\;2.5{\mu}m$ mounted on the top of AFM tip (NPS) were used for nano-scale contact and Soda Lime glass balls of radii 0.25mm, 0.5mm, 1mm were used for micro-scale contact. At nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at micro scale it was measured using ball-on flat type micro-tribotester. All the experiments were conducted at controlled conditions of temperature $(24\pm1^{\circ}C)$ and humidity $(45\pm5\%)$. Friction was measured as a function of applied normal load in the range of 0-160nN at nano scale and in the range of $1000{\mu}N,\; 1500{\mu}N,\;3000{\mu}N\;and\;4800{\mu}N$ at micro scale. Results showed that the friction at nano scale increased with the applied normal load and ball size for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for Si-wafer at micro scale. However, for DLC friction decreased with the ball size. This difference of in behavior of friction in DLC nano- and microscale was attribute to the difference in the operating mechanisms. The evidence of the operating mechanisms at micro-scale were observed using scanning electron microscope (SEM). At micro-scale, solid-solid adhesion was dominant in Silicon-wafer, while plowing in DLC. Contrary to the nano scale that shows almost a wear-less situation, wear was prominent at micro-scale. At nano- and micro-scale, effect of contact area on the friction was discussed with the different applied normal load and ball size.

대형 지반시험장비의 개발 및 구축 (Development and Installation of Large-scale Geotechnical Testing Facilities)

  • 서민우;하익수;김용성;박동순
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2005년도 춘계 학술발표회 논문집
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    • pp.1233-1240
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    • 2005
  • As the geotechnical technologies have grown, the size of civil structures has become bigger than before, thereby requiring large-scale geotechnical testing equipments which can evaluate the mechanical behavior of large size testing materials such as gravel, crushed rock and so on. These kind of large testing equipments are usually used to evaluate the mechanical characteristics of large size material which are applied in the large infra structures like dam, seashore structure, coastal landfill, soil-structure interaction and seismic response of large-scale structure. In this research, state-of-the-art information in the field of geotechnical engineering was collected and summarized for such large-scale experimental equipments as large-scale geo-centrifuge, large-scale triaxial testing machine, large-scale direct shear testing apparatus and large-scale oedometer.

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소형탈선시뮬레이터 상에서의 1/5 축소대차의 안정성 해석 (A Running Stability Test of 1/5 Scaled Bogie using Small Scale Derailment Simulator)

  • 엄범규;이세용;이영엽;강부병;이희성
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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    • pp.1905-1913
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    • 2011
  • The dynamic characteristic of bogie that is driving system of railway vehicle is very important regarding decision of vehicle characteristics as running safety and comport. The dynamic characteristic test of bogie is tested on full size in place on field testing on track. But, the testing on the full size caused many problems. To overcome these problem by full size test, the Railway Safety Research Center in Seoul National University of Science & Technology developed 1/5 scale size of small scale derailment simulator and is currently testing running stability of 1/5 scaled bogie. Also To take effectively advantage of running stability test using small scale derailment simulator in actuality design and reliability estimation, it is necessary comparison and examination with field test and theoretical analysis result In this paper. to achieve running stability analysis of 1/5 scaled bogie on small scale derailment. the program using MATLAB that is fast compose and analysis the motion equation of Saemaul power bogie is developed. It is achieved analysis according to various specification (weight, size, suspension, etc..) and is evaluated corelation between test result and dynamic characteristic of actual railway vehicle.

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