• 대한기계학회논문집B
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• 제33권10호
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• pp.820-826
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• 2009

The anisotropic phonon conductions with varying Joule heating rate of the silicon film in Silicon-on-Insulator devices are examined using the electron-phonon interaction model. It is found that the phonon heat transfer rate at each boundary of Si-layer has a strong dependence on the heating power rate. And the phonon flow decreases when the temperature gradient has a sharp change within extremely short length scales such as phonon mean free path. Thus the heat generated in the hot spot region is removed primarily by heat conduction through Si-layer at the higher Joule heating level and the phonon nonlocality is mainly attributed to lower group velocity phonons as remarkably dissimilar to the case of electrons in laser heated plasmas. To validate these observations the modified phonon nonlocal model considering complete phonon dispersion relations is introduced as a correct form of the conventional theory. We also reveal that the relation between the phonon heat deposition time from the hot spot region and the relaxation time in Si-layer can be used to estimate the intrinsic thermal resistance in the parallel heat flow direction as Joule heating level varies.

• Steel and Composite Structures
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• 제29권1호
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• pp.53-66
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• 2018

A high-order nonlocal strain gradient model is developed for wave propagation analysis of porous FG nanoplates resting on a gradient hybrid foundation in thermal environment, for the first time. Material properties are assumed to be temperature-dependent and graded in the nanoplate thickness direction. To consider the thermal effects, uniform, linear, nonlinear, exponential, and sinusoidal temperature distributions are considered for temperature-dependent FG material properties. On the basis of the refined-higher order shear deformation plate theory (R-HSDT) in conjunction with the bi-Helmholtz nonlocal strain gradient theory (B-H NSGT), Hamilton's principle is used to derive the equations of wave motion. Then the dispersion relation between frequency and wave number is solved analytically. The influences of various parameters (such as temperature rise, volume fraction index, porosity volume fraction, lower and higher order nonlocal parameters, material characteristic parameter, foundations components, and wave number) on the wave propagation behaviors of porous FG nanoplates are investigated in detail.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1992년도 한국우주과학회보 제2권1호
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• pp.16-16
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• 1993

The Cosmic Mach number M is the ratio of the bulk flow velocity of the galaxrvelocity field on some scale R to the unall scale velocity dispersion within refcions of scale R. Because M is the ratio of two velocities, it is inn-dimansionat and the Here, independent of the amplitude of the power specHim and of the biasplnmeter in the linear theory. We have measured the Mach rnlmber for two observational samples: a spiral galaxy sample(AHM) of Aaronson and hiscoBlaborators with absolute distances measured by the infrared Ttillr-Fisher relatioa and an elliptical galaxy sample(EGALS) of Faber or 0, with distances determined by the relation. The effective depths distances of galaxies from the Local Group of these samples are 1639 km/s and 2862 e/s, respectivelr. The Machnumbers from these observed peculiar velocity Selds He fund as M=0.95 for AHMand M=0.59 for EGALS. We comPBre these calculated Mach numbers with thosefrom meck surweys drawn fuom three cosnulogical medels: the stand8rd biased nh=0.5 CDM modet an open CDM rrudel with gh=0.2, and a medd with thepower-law power specelm P(k)-k-1 and n=1. The Mach rnlmber test can give robust constraints on these cosmelogical nudels whose power spectra have very different shapes at large scales.

• 한국대기환경학회지
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• 제8권4호
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• pp.213-220
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• 1992

Simple correlation analysis, factor analysis, and multi-variate analysis have been performed to analyze the relationship between air pollution and meteorological factors for air pollution and meteorological data measured at Kwanghwamun in Seoul during the period of one year(January 1990 $\sim$ December 1990). As a result of simple correlation and factor analysis, $SO_2$, TSP and CO concentrations have shown high negative correlation with temperature and among these indicating that these are related with pollutant emission trend based upon heating fuel usage. Ozone has a good corrleation with solar radiation and relative humidity to have a closed relation with $O_3$ generation reaction mechanism. The result of multi-variate correlation analysis shows that the concentration of $SO_2$ and CO are adequate for correlation model with ambient temperature and wind speed and $O_3$ concentrations are adequate for that with solar radiation and wind speed. $SO_2$ and CO levels are considered to be affected first of all by heating fuel usage as a emssion source and wind speed as a dispersion effect. The $SO_2$ concentration in the condition that the temperature fall below zero is explained by multilicative model with wind speed, only one variable.

• Journal of Astronomy and Space Sciences
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• 제16권1호
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• pp.41-52
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• 1999

지구 주변에는 플라즈마로 가득 차 있고 그것을 매질로 하는 다양한 플라즈마 파동이 존재한다. 우주공간 플라즈마는 여러 종류의 이온과 전자로 구성되어 있고 특히 이온들은 파동의 전파에 많은 영향을 미친다. 다중 이온 플라즈마에서 파동분산 방정식의 해를 구하는 것은 상당히 복잡하다. 따라서, 임의의 자기장, 밀도를 고려하여 우주공간에서 다중 이온 플라즈마에서 파동의 분산관계를 쉽게 알 수 있는 계산모델을 개발하였다. 이 모델로부터 IGRF(International Geomagnetic Reference Field)에서 임의 지점을 지나는 자력선과 관측된 밀도 함수로부터 각 위도별로 가능한 파동들의 성질을 조사하여 위성의 초기 관측 자료 분석에 응용하였다. 예를 들어 POLAR 위성의 관측값 중에서 자기 적도 근처에서 발생되어 자력선을 따라 전파하는 특정한 범위의 주파수 경우 파동의 편극 상태가 변한 위치, 전파경로 등을 본 모델을 이용하여 예측할 수 있었다.

• 한국자기학회지
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• 제3권3호
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• pp.234-240
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• 1993

본 연구에서는 습식법에 의해서 초미립 마그네타이트를 합성하였으며, 이를 자성유체의 분산질로 하는 수상자성 유체를 제조하였다. 이때 합성마그네타이트의 입자표면에는 dodecanoic acid 이온의 흡착층을 형성시켜 수용액중에 안정하게 분산시켰다. 또한 합성된 마그네타이트의 기초적 물 성과 수상자성유체 제조시 계면활성제의 첨가량 및 pH의 변화등이 자성유체의 분산측성, 자기적 특성 및 콜로이드적 안정성에 미치는 영향을 조사하였다.

• Computers and Concrete
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• 제7권5호
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• pp.469-482
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• 2010

This paper investigates the concrete permeability through a numerical and statistical approach. Concrete is considered as a random heterogeneous composite of three phases: aggregates, interfacial transition zones (ITZ) and matrix. The paper begins with some classical bound and estimate theories applied to concrete permeability and the influence of ITZ on these bound and estimate values is discussed. Numerical samples for permeability analysis are established through random aggregate structure (RAS) scheme, each numerical sample containing randomly distributed aggregates coated with ITZ and dispersed in a homogeneous matrix. The volumetric fraction of aggregates is fixed and the size distribution of aggregates observes Fuller's curve. Then finite element method is used to solve the steady permeation problem on 2D numerical samples and the overall permeability is deduced from flux-pressure relation. The impact of ITZ on overall permeability is analyzed in terms of ITZ width and contrast ratio between ITZ and matrix permeabilities. Hereafter, 3680 samples are generated for 23 sample sizes and 4 contrast ratios, and statistical analysis is performed on the permeability dispersion in terms of sample size and ITZ characteristics. By sample theory, the size of representative volume element (RVE) for permeability is then quantified considering sample realization number and expected error. Concluding remarks are provided for the impact of ITZ on concrete permeability and its statistical characteristics.

• Journal of Forest and Environmental Science
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• 제30권1호
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• pp.101-106
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• 2014

The purpose of this research was to figure out the stand structure and growth characteristic with relation to DBH, height, and volume in sixteen Pinus koraiensis plantations of Gangwon province region. Age class was diversely distributed from age class II (16 yr) to age class VIII (77 yr), and, in terms of site index, sixteen regions were superior: nine regions 'high', seven regions 'middle'. The distribution of DBH by sites appeared a bell-shaped curve, and the number of trees was the most in diameter section of 18-22 cm. The dispersion of DBH was various with age and widest ranging from 18 cm to 58 cm in age class VII-VIII. The distribution of height was also a bell-shaped curve with the smaller deviation than the distribution of DBH, and most of trees were in height section of 14-18 m. The correlation of DBH and height was high (r=0.75), and the volume bigger than 1.0 $m^3$ was presented from DBH 35 cm, height 20 m.

• 동력기계공학회지
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• 제17권2호
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• pp.56-62
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• 2013

A technique is presented that uses a circular waveguide for the measurement of the bulk shear (S-wave) velocities of unconsolidated, saturated media, with particular application to near surface soils. The technique requires the measurement of the attenuation characteristics of the fundamental torsional mode that propagate along an embedded pipe, from which the acoustic properties of the surrounding medium are inferred. From the dispersion curve analysis, the feasibility of using fundamental torsional mode which is non-dispersive and have constant attenuation over all frequency range is discussed. The principles behind the technique are discussed and the results of an experimental laboratory validation are presented. The experimental data are best fitted for the different depths of wetted sand and the shear velocities are evaluated as a function of depths. Also the characteristics of the reflected signal from the defects are examined and the reflection coefficients are calculated for identifying the relation between defect sizes and the magnitude of the reflected signal.

• 환경위생공학
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• 제7권2호
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• pp.141-152
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• 1992

Simple correlation analysis, factor analysis, and multi-verite analysis have been performed to analyze the relationship between air pollution and meteorological factors for air pollution and meteorological data measured at Kwanghwamun in Seoul during the period of one year (January 1990" December 1990). As a result of simple correlation and factor analysis, $SO_2$, TSP and CO concentrations have shown high negative correlation with temperature and among these indicating that these are related with pollutants emission trend based upon heating fuel usage. Ozone has a good correlation with solar radiation and relative humidity to have a closed relation with $0_3$ generation reaction mechanism. The result of multi-variate correlation analysis shows that the concentration of $SO_2$ and CO are adequate for correlation model with ambient temperature and wind speed and 0$_{3}$ concentrations are adequate for that with solar radiation and wind speed. $SO_2$ and CO levels are considered to be affected first of all by heating fuel usage as a emission source and wind speed as a dispersion effect. The $SO_2$ concentration in the condition that the temperature fall below zero is explained by multiplicative model with wind speed, only one variable.