• Title, Summary, Keyword: Power-Law

Search Result 1,736, Processing Time 0.05 seconds

The Power of Power Law: A View from VoD Service

  • Lee, Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.38B no.8
    • /
    • pp.607-614
    • /
    • 2013
  • In this work we investigate the power of power law in the VoD service over IP network. Especially, we show that the power of power law is strong in the location of the contents storage for the VoD service and its impact on the link dimensioning. This work first shows the instance of the power law in the popularity of the video contents from the real data for the IPTV service. After that we propose an analytic model that characterizes the behavior of customers in accessing the video servers as well as the power law in the viewing pattern. Finally, we show the impact of the power law by proposing a model for the cost as well as link dimensioning. Via numerical experiment we show the implication of the proposition.

Hydrodynamic Entrance Lengths and Entrance Correction Factors for a POWER-LAW Fluid in a Circular Duct (원관에서 POWER-LAW 유체의 수력학적 입구길이와 입구보정계수에 관한연구)

  • 오광석
    • The Korean Journal of Rheology
    • /
    • v.7 no.3
    • /
    • pp.261-266
    • /
    • 1995
  • 원관에서 power-law 유체에 대하여 수력학적 입구길이와 입구보정계수를 측정할수 있는 새로운 방법이 개발되었다. 유변학적 성질을 측정할수 있는 긴관과 입구보정계수를 측 정할수 있는 짧은 관을 가진 새로운 모세관 점도계를 이용하여 증류수를 실험한 결과 유변 학적 성질과 입구 보정계수가 표준값과 비교하여 1%안의 오차를 얻었다. Power-law 유체 에 대한 해석 및 실험결과(Carbopol 960 용액)도 이미 보고된 값과 $\pm$6% 이내로 잘 일치하 였다.

  • PDF

Investigation of Pressure Drop for a Pseudo-plastic Fluid Flow in Isosceles Triangle Pipes (이등변삼각형 단면을 갖는 파이프 내의 Pseudo-Plastic 유체유동에 대한 압력강하의 연구)

  • Lee, D.R.
    • Journal of the Korea Society For Power System Engineering
    • /
    • v.13 no.2
    • /
    • pp.30-35
    • /
    • 2009
  • Numerical Calculations for dimensionless pressure drop (friction factor times Reynolds number) have been obtained for fully developed laminar flow of MPL(Modified Power Law) fluid in isosceles triangle pipes. The solutions are valid for Pseudoplastic fluids over a wide range from Newtonian behavior at low shear rates through transition region to power law behavior at higher shear rates. The analysis identified a dimensionless shear rate parameter which for a given set of operating conditions specifies where in the shear rate range a particular system is operating, i.e., Newtonian, transition or power law region. The numerical calculation data of the dimensionless pressure drop for the Newtonian and power law regions are compared with previously published asymptotic results presenting within 0.16 % in Newtonian region and 2.98 % in power law region.

  • PDF

Analysis of vertical velocity distribution in natural rivers with ADCPs (ADCP를 이용한 자연하천의 연직유속분포 분석)

  • Lee, Hea-Eun;Lee, Chan-Joo;Kim, Yong-Jeon;Kim, Won
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • /
    • pp.1865-1869
    • /
    • 2009
  • 본 연구에서는 ADCP를 이용하여 국내 하천에서의 연직유속분포 특성을 살펴보았다. 먼저, 김치영 등 (2004)의 10점법 측정 자료와의 비교를 통하여 power law와 log law로 ADCP의 측정불가역의 유속분포를 추정하는 방법을 검증하였다. 또한, 국내 하천의 다양한 흐름조건을 고려한 4개 지점, 총 26개 자료를 사용하여 각각의 ADCP 측정자료마다 최적의 power 식과 log 식을 구했으며, 이 식들로부터 구한 수심평균유속을 ADP-stationary (고정된 지수 1/6)의 평균유속과 비교하였다. 그 결과 power law로 ADCP 측정불가역을 외삽하는 경우 하천의 흐름에 적절한 지수를 사용했는지 여부가 평균유속의 정확도에 큰 영향을 미침을 확인하였다. 이에, Limerinos (1970)의 조도계수 계산식과 ISO (1997)에 제시된 power law 지수식을 토대로 측정 자료의 power law 지수와 하상재료, 수심의 상관관계를 살펴보았다.

  • PDF

Power Law Exponent in Coastal Area of Northeastern Jeju Island for the Investigation of Wind Resource (풍력자원 조사를 위한 제주 북동부 연안역의 멱지수 분석)

  • Moon, Seo Jeong;Ko, Jung Woo;Lee, Byung Gul
    • Journal of Korean Society for Geospatial Information System
    • /
    • v.21 no.4
    • /
    • pp.65-71
    • /
    • 2013
  • Wind shear means the variation of wind speed according to the height. Wind shear is the important factor affecting the energy production of wind turbines. Power Law is used to extrapolate wind speed data. Normally, a Power Law exponent of 0.143 is used and this is referred to as the 1/7th Power Law. The Power Law exponent is affected by atmospheric stability and surface roughness of the site. Thus, it is necessary to calculate the Power Law exponent of the site exactly for an accurate estimation of wind energy. In this study, wind resources were measured at the three Met-masts which were located in the coastal area of northeastern Jeju Island. The Power Law exponents of the sites were calculated and proposed using measured data. They were 0.141 at Handong, 0.138 at Pyeongdae, and 0.1254 at Udo. We compared annual energy productions which are calculated using a Power Law exponent of 0.143, the proposed value of the Power Law exponents for each site, and the measured data. As a result, the cases of calculating using the proposed values were more similar to the cases using the measured data than the cases using the 0.143 value. Finally, we found that the propsed values of the Power Law exponent are available to more accurately estimate wind resources.

Graetz Problem Solutions for a Modified Power Law Fluid over a Wide Range of Shear Rate (광범위한 전단률에서 적용가능한 수정된 POWER LAW 유체에 대한 GRAETZ문제 해법)

  • T.F. irvine, Jr
    • The Korean Journal of Rheology
    • /
    • v.7 no.1
    • /
    • pp.35-41
    • /
    • 1995
  • 층류 열전달에서 작은 Reynolds number에서의 원통내의 흐름에대한 Power law 유 체의 해법이 사용될 수가 없는 것을 낮은 전단률(Shear Rate)에서 Power Law 법칙이 적용 되지 않기 때문이다. 본 연구에서는 이문제를 새로운 구성방정식을 이용하여 높은 전단률에 서는 Power Law 법칙이 낮은 전단률에서는 Newtonian 법칙이 그 중간에서는 천이과정을 모두 포함하는 전범위의 전단률에 대해 해결하였다. 이러한 구성방정식의 기본개졈은 실험 결과와도 잘 일치하였따. 이 구성방정식을 이용하여 Graetz 문제를 해결하였고 경계조건은 일정온도와 일정열속이다. 이용하기 쉬운 전단률변수는 적용범위가 Newtonian인지 Power law 인지 아니면 중간 천이과정인지를 나타내준다.

  • PDF

POWER SPECTRUM ANALYSIS OF THE OMC1 IMAGE AT 1.1MM WAVELENGTH

  • Youn, So-Young;Kim, Sung-Eun
    • Journal of The Korean Astronomical Society
    • /
    • v.45 no.4
    • /
    • pp.93-99
    • /
    • 2012
  • We present a 1.1mm emission map of the OMC1 region observed with AzTEC, a new large-format array composed of 144 silicon-nitride micromesh bolometers, that was in use at the James Clerk Maxwell Telescope (JCMT). These AzTEC observations reveal dozens of cloud cores and a tail of filaments in a manner that is almost identical to the submillimeter continuum emission of the entire OMC1 region at 450 and $850{\mu}m$. We perform Fourier analysis of the image with a modified periodogram and the density power spectrum, which provides the distribution of the length scale of the structures, is determined. The expected value of the periodogram converges to the resulting power spectrum in the mean squared sense. The present analysis reveals that the power spectrum steepens at relatively smaller scales. At larger scales, the spectrum flattens and the power law becomes shallower. The power spectra of the 1.1mm emission show clear deviations from a single power law. We find that at least three components of power law might be fitted to the calculated power spectrum of the 1.1mm emission. The slope of the best fit power law, ${\gamma}{\approx}-2.7$ is similar to those values found in numerical simulations. The effect of beam size and the noise spectrum on the shape and slope of the power spectrum are also included in the present analysis. The slope of the power law changes significantly at higher spatial frequency as the beam size increases.

Investigation of Heat Transfer Augmentation with Pseudoplastic Fluids in Annular Pipes (환상 파이프 내에서의 의소성 유체를 이용한 열전달 향상에 관한 연구)

  • Lee, Dong-Ryul
    • Journal of the Korean Society of Mechanical Technology
    • /
    • v.13 no.2
    • /
    • pp.85-91
    • /
    • 2011
  • Computational results with pseudoplastic fluid flows for fully developed non-Newtonian laminar flows have been obtained. Those consist of the product of friction factor and Modified Reynolds number and Nusselt numbers with respect to the shear rate parameter in an annular pipe. The numerical results of the product of friction factor and Reynolds numbers and the Nusselt numbers for both Newtonian region and the power law region were compared with previously published asymptotic results, respectively. In the present calculations, the product of friction factor and Newtonian Reynolds numbers for pseudoplastic fluid at power law region in annular pipe is 180% less than that for Newtonian fluid. For power law fluids with different power law flow indices, the difference of the product of friction factor and power law Reynolds number between previous and the present results at the power law region is within 0.20%. The solutions also show the effect of the shear rate parameter on the Nusselt number and about 11% increase of Nusselt number at the power region.

Analysis of Physical Combat Power for Unmanned Combat Aerial Vehicle (무인전투기 물리적 전투력 분석)

  • Min, Seungsik;Oh, Kyungwon
    • Journal of Aerospace System Engineering
    • /
    • v.11 no.6
    • /
    • pp.50-55
    • /
    • 2017
  • The objective of this study was to use the Lanchester equation to predict the outcome of our engagement between our unmanned aerial vehicle (UAV) (Blue Group) and enemy UAV (Red Group). Lanchester's law states that the power of corps is proportional to the number of combatants. A second law states that the power of corps is proportional to the square of the number of combatants. The first law is a suitable law for guerrilla warfare while the second law is known as the law suitable for all-out war. Therefore, the second law is commonly used. The second law of Lanchester's was used in this study to predict engagement results. We estimated the battle loss rate value to win the battle as well as the required power number. We also predicted power number to make the damage of our group less than one. The battle loss rate to reliably receive victory when the enemy's UAV and the ally's UAV are equal in number of combat units must be 1: 1.5 or more.