• 제목/요약/키워드: required velocity

검색결과 980건 처리시간 0.027초

변동풍속의 파워 스펙트럴 밀도에 관한 평가 (Estimation on the Power Spectral Densities of Daily Instantaneous Maximum Fluctuation Wind Velocity)

  • 오종섭
    • 한국방재안전학회논문집
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    • 제10권2호
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    • pp.21-28
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    • 2017
  • 시공간적으로 불규칙하게 작용하는 변동 풍속 난류의 자료는 풍공학적으로 돌풍계수 평균풍속 변동 풍하중등의 계산에서 요구되지만, 내풍 및 사용성에 따른 동적응답의 평가에서는 변동 풍속의 파워 스펙트럴 밀도함수가 요구된다. 본 논문에서는 1987-2016.12.1일까지의 일순간최대풍속 자료를 확률과정으로 가정했고, 이 실측된 자료와 확률이론을 근거로 평균류방향 파워 스펙트럴 밀도 함수에 대한 기초적 자료를 얻고자 대표지점(6개 지점)을 선정했다. 선정된 각 지점에 대한 일순간최대풍속자료는 기상청으로부터 획득했다. 해석결과 본 논문에서 평가된 스펙트럼 모델은 저진동수 영역에서는 Solari, 고진동수 영역에서는 von Karman의 모델과 근접한 현상을 나타냈다.

회전형 CMP장비의 속도 및 마찰력 분포 해석 (Velocity and Friction Force Distribution in Rotary CMP Equipment)

  • 김형재;정해도;이응숙;신영재
    • 한국정밀공학회지
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    • 제20권5호
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    • pp.39-39
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    • 2003
  • As the design rules in semiconductor manufacturing process become more and more stringent, the higher degree of planarization of device surface is required for a following lithography process. Also, it is great challenge for chemical mechanical polishing to achieve global planarization of 12” wafer or beyond. To meet such requirements, it is essential to understand the CMP equipment and process itself. In this paper, authors suggest the velocity distribution on the wafer, direction of friction force and the uniformity of velocity distribution of conventional rotary CMP equipment in an analytical method for an intuitive understanding of variation of kinematic variables. To this end, a novel dimensionless variable defined as “kinematic number” is derived. Also, it is shown that the kinematic number could consistently express the velocity distribution and other kinematic characteristics of rotary CMP equipment.

회전형 CMP장비의 속도 및 마찰력 분포 해석 (Velocity and Friction Force Distribution in Rotary CMP Equipment)

  • 김형재;정해도;이응숙;신영재
    • 한국정밀공학회지
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    • 제20권5호
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    • pp.29-38
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    • 2003
  • As the design rules in semiconductor manufacturing process become more and more stringent, the higher degree of planarization of device surface is required for a following lithography process. Also, it is great challenge for chemical mechanical polishing to achieve global planarization of 12” wafer or beyond. To meet such requirements, it is essential to understand the CMP equipment and process itself. In this paper, authors suggest the velocity distribution on the wafer, direction of friction force and the uniformity of velocity distribution of conventional rotary CMP equipment in an analytical method for an intuitive understanding of variation of kinematic variables. To this end, a novel dimensionless variable defined as “kinematic number” is derived. Also, it is shown that the kinematic number could consistently express the velocity distribution and other kinematic characteristics of rotary CMP equipment.

Infeed Control Algorithm of Sorting System Using Modified Trapezoidal Velocity Profiles

  • Kim, Ki Hak;Choi, Yong Hoon;Jung, Hoon
    • ETRI Journal
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    • 제37권2호
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    • pp.328-337
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    • 2015
  • This paper applies acceleration/deceleration control-based velocity profiles to an infeed control algorithm for a cross-belt-type sorting system to improve the accuracy and performance of the system's infeed. The velocity profiles are of a trapezoidal shape and often have to be modified to ensure that parcels correctly synchronize with their intended carriers. Under the proposed method, an infeed line can handle up to 5,600 items/h, which indicates a 40% increase in performance in comparison with its existing handling rate of 4,000 items/h. This improvement in performance may lead to a reduction in the number of infeed lines required in a sorting system. The proposed infeed control algorithm is applied to a cross-belt-type sorting system (model name: SCS 1500) manufactured by Vanderlande Industries.

감마과정 모델을 적용한 포구속도 저하량에 따른 저장수명 예측기법 연구 (A Study on the Storage Life Estimation Method for Decrease of Muzzle Velocity using Gamma Process Model)

  • 박성호;김재훈
    • 한국군사과학기술학회지
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    • 제16권5호
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    • pp.639-645
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    • 2013
  • The aim of the study is to investigate the method to estimate a storage life of propelling charge on the decrease of muzzle velocity by stochastic gamma process model. It is required to establish criterion for state failure to estimate the storage life and it is defined in this paper as a muzzle velocity difference between reference value and maximum allowable standard deviation multiplied by 6. The relationship between storage time and muzzle velocity is investigated by nonlinear regression analysis. The stochastic gamma process model is used to estimated the state distribution and the life distribution for storage time for 155mm propelling charge KM4A2 because the regression analysis is a deterministic method and it can't describe the distribution of life for storage time.

비압축성 나비어-스톡스 방정식의 완전 내재적 분리 방법 (Fully-Implicit Decoupling Method for Incompressible Navier-Stokes Equations)

  • 김경연;백승진;성형진
    • 대한기계학회논문집B
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    • 제24권10호
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    • pp.1317-1325
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    • 2000
  • A new efficient numerical method for computing three-dimensional, unsteady, incompressible flows is presented. To eliminate the restriction of CFL condition, a fully-implicit time advancement in which the Crank-Nicolson method is used for both the diffusion and convection terms, is adopted. Based on an approximate block LU decomposition method, the velocity -pressure decoupling is achieved. The additional decoupling of the intermediate velocity components in the convection term is made for the fully -implicit time advancement scheme. Since the iterative procedures for the momentum equations are not required, the velocity components decouplings bring forth the reduction of computational cost. The second-order accuracy in time of the present numerical algorithm is ascertained by computing decaying vortices. The present decoupling method is applied to minimal channel flow unit with DNS (Direct Numerical Simulation).

표면 충돌 액적의 분열에 관한 실험적 연구 (An Experimental Study of Breakup of Impinging Droplets on a Hot Surface)

  • 고영성;정석호
    • 한국자동차공학회논문집
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    • 제2권5호
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    • pp.85-92
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    • 1994
  • Characteristics of breakup of a liquid droplet impinging on a hot surface has been investigated experimentally by using decane fuel. Factors influencing droplet breakup are surface temperature, impinging velocity, droplet diameter and incident angle. Droplets impinging on a hot surface begins to breakup at $220{\sim}235^{\circ}C$. This temperature varies with impinging Velocity, droplet diameter and incident angle. For wall temperature of $220{\sim}245^{\circ}C$ and above $270^{\circ}C$, breakup probability increases as impinging velocity increases showing S shape curve. For $245{\sim}265^{\circ}C$, a local minimum heat transfer rate occurs. In this temperature range, breakup probability shows nonmonotonous behavior as functions of impinging velocity. As droplet diameter decreases, impinging velocity required for droplet breakup increases. An optimum impinging angle for droplet breakup exists which are found to be about $75^{\circ}$.

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전통건축물보존지구내에서의 연소속도식을 고려한 방재계획의 수립과 재난위험도평가 시스템 구축에 관한 연구 (A Study on Disaster Prevention and Risk Assessment System Applying Combustion Velocity at Traditional Housing Zone)

  • 김희성;노삼규
    • 한국화재소방학회논문지
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    • 제15권4호
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    • pp.1-9
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    • 2001
  • The purpose of this study is to set up disaster prevention plan and risk assessment system considering combustion velocity at traditional housing zone. The combustion velocity analysis could contribute to build in disaster prevention technique through the potential risk analysis of the area, such analysis also able to set up comprehensive disaster prevention management system. Following results have achieved through the combustion velocity calculation. \circled1 The combustion velocity was calculated in order of the below winds, the above winds and the side winds. \circled2 It must be careful to set up disaster prevention plan in case of the below winds. \circled3 The combustion velocity was calculated at the density Bone where neighboring Distance and Length was small. \circled4 It proved that factors of each parameter not mostly effect to analyse the combustion velocity in limit of the 30 minutes after ignition. \circled5 At the density zone where Distance and Length is small the duration of transfer to neighboring house takes up to 4 minutes, it is required to set up of emergency response plan to minimize the fire dispersion.

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적성소화기 위협에 대한 함정용 선체재질별 방호한계속도 비교 연구 (Ballisitic Limit Velocity Comparison for Warship Materials against AK-47 7.62mm MSC)

  • 김종환;신윤호
    • 대한조선학회논문집
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    • 제54권4호
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    • pp.286-293
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    • 2017
  • This paper presents ballistic limit velocity results of a variety of materials generally used in warships. Ballistic limit velocity is the velocity required for a projectile to penetrate a target with 50 percents of time and is widely used as a measure of armour bulletproofing. For this study, live fire experiments were implemented using AK-47 $7.62{\times}9mm$ mild steel core as a projectile as well as various thickness warship materials as a target. Also, methods of MIL-STD-662F, NIJ-STD-0101.06 and support vector machine were applied to measure the ballistic limit velocity and then their results were graphically analyzed for comparison. The minimum of their results was considered as the ballistic limit velocity in a conservative way.

A summertime near-ground velocity profile of the Bora wind

  • Lepri, Petra;Kozmar, Hrvoje;Vecenaj, Zeljko;Grisogono, Branko
    • Wind and Structures
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    • 제19권5호
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    • pp.505-522
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    • 2014
  • While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.