• 상하수도학회지
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• 제19권6호
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• pp.827-837
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• 2005

In this study, we derived a new non-dimensional variable including bubble size and air diffusing area by Buckingham's theorem for making a practical correlation with experimental results. Firstly, we drew a relationship between a non-dimensional variable, $NH/u_s$, which has a form of Froude number and destratification efficiency with a simple theoretical consideration. Then we derived two non-dimensional variables by Buckingham's ${\pi}$-theorem and equating them with a form of $Fr_N$ for making single parameter to correlate overall destratification efficiency. As the result, the single parameter Be number shows a correlations with destratification efficiencies obtained from laboratory and pilot experiments. Also, for the practical applications, we conducted multiple regression analysis using Be and tank area to make predictive equations about destratification efficiency. The result also shows a successful correlations with destratification efficiency ($R^2$>0.9, p<0.001). Using this equation, we proposed a new design methodology with respect to bubble diffusing area.

• 한국터널지하공간학회 논문집
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• 제3권1호
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• pp.3-9
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• 2001

발파한 후 파쇄된 암석의 파쇄도는 발파효율을 나타내는 척도의 하나로서 발파방법을 평가하는 주요 인자이다. 파쇄도는 적재작업과 재활용을 위한 분쇄작업에 큰 영향을 미친다. 그러나 현장규모로 쌓여 있는 발파암 더미로부터 파쇄도를 조사한다는 것은 용이한 작업이 아니다. 본 논문에서는 현장 사례연구로서 터널발파에서 가장 중요한 요소인 심빼기방법 중 경사공을 이용한 V형 심빼기와 수평공 무장약공을 이용한 burn 심빼기 발파방법 중 파쇄도 측면에서 더 효율적인 방법을 선택하기 위하여 발파후 파쇄된 암을 사진촬영하여 이미지 분석을 실시하고 몇가지 파쇄입도 예측식을 이용한 분석 결과와 비교하였다.

• 소성∙가공
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• 제25권3호
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• pp.182-188
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• 2016

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to producing multi-curvature surfaces by controlling the strain distribution along longitudinal direction. In FRRF, a sheet metal is shaped into the desired curvature by using reconfigurable rollers and gaps between the rollers. As FRRF technology and equipment are under development, a simulation model corresponding to the physical FRRF would aid in investigating how the shape of a sheet varies with input parameters. To facilitate the investigation, the current study exploits regression analysis to construct a predictive model for the longitudinal curvature of the sheet. Variables considered as input parameters are sheet compression ratio, radius of curvature in the transverse direction, and initial blank width. Samples were generated by a three-level, three-factor full factorial design, and both convex and saddle curvatures are represented by a quadratic regression model with two-factor interactions. The fitted quadratic equations were verified numerically with R-squared values and root mean square errors.

• Bulletin of the Korean Chemical Society
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• 제27권2호
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• pp.211-218
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• 2006

This work deals with 24 substances composed of nitrogen-containing heterocycles. The relationships between the chromatographic retention factor (k) and those physicochemical properties which are relevant in quantitative structure-properties relationship (QSPR) studies, such as the polarizability $(\alpha)$, molar refractivity (MR), lipophilicity (logP), dipole moment $(\mu)$, total energy $(E_{tot})$, heat of formation $(\Delta H_f)$, molecular surface area $(S_M)$, and binding energy $(E_b)$, were investigated. The accuracy of the simple linear regressions between the chromatographic retention and the descriptors for all of the compounds was satisfactory (correlation coefficient, $0.8 \leq r \leq 1.0$). The QSPR models of these nitrogen-containing heterocyclic compounds could be predicted with a multiple linear regression equation having the statistical index, r = 1.000. This work demonstrated the successful application of the multiple linear approaches through the development of accurate predictive equations for retention factors in liquid chromatography.

• 한국화재소방학회논문지
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• 제21권4호
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• pp.32-37
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• 2007

인화점의 정보를 확보하는 것은 화재 및 폭발의 예방을 위해 대단히 중요하다. 본 연구에서는 2-propanol+acetic acid 계와 2-propanol+n-propionic acid 계의 하부 인화점을 클리브랜드 개방식 장치를 이용하여 측정하였다. 실험값은 Raoult의 법칙, Wilson 식과 NRTL 식에 의해 계산된 값과 비교하였다. 그 결과, Wilson 식과 NRTL 식에 의한 예측값이 Raoult의 법칙에 의한 예측값 보다 실험값에 더욱 근접하였다. 또한, NRTL 식의 실험값에 대한 모사성이 Wilson 식의 그것 보다 우수하였다.

• 한국추진공학회지
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• 제6권1호
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• pp.63-70
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• 2002

본 연구에서는 초음속 및 음속 마이크로 제트 유동의 특성을 파악하기 위해서 2차원 축대칭 압축성 Navier-Stokes 방정식을 이용한 수치해석을 수행하였다. 수치해석에서는 여러 형태의 난류모델을 적용하여 실험결과와 비교하였으며, 부족팽창과 과팽창 상태를 얻기 위하여 노즐 출구의 압력비 $P_b/P_e$를 0.2~l.25로 변화시켰다. 또, 레이놀즈 수 Re를 약 600~40000까지의 범위에서 변화시켜, $P_b/P_e$와 Re가 마이크로 제트 유동장에 미치는 영향을 조사하였다. 본 연구로부터 층류 제트의 특성은 난류 제트와는 달리 레이놀즈 수의 의존성이 크다는 것을 알았다.

• Journal of Community Nutrition
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• 제2권2호
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• pp.135-140
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• 2000

The objectives of this study were to determine whether older Americans would provide valid energy intake information using a 24-hr recall method and to determine which characteristics were predictive of under-report of energy intake. We conducted 24-hour recalls on 83 male and 105 female community-dwelling older adults(66-87y) in the USA to assess energy(EI) and nutrient intakes. Basal metabolic rate(BMR) was calculated from age-and gender-specific equations of Schofield. Under-reporting was defined a priori as EI : BMR<0.9. Subjects volunteered demographic information, underwent depression and cognition exams, and completed a Level II Nutrition Risk Screen. Differences between under- and adequate-reporters were assessed using t-tests for characteristics and macro-nutrient profile. Stepwise regression analyses were used to predict under-reporting status. Under-reporting of EI occurred in 34% of the sample. Neither geriatric depression scale(GDS) score, nor self-reported weight loss were related to under-reporting. On average, under-reporters had higher body mass indices. The most significant variables for the main effect to predict the ratio of energy intake to estimated basal metabolic rate(EI : BMRest) were BMI and age. Using a standard cut-off of 76% of the recommended dietary allowances for Americans, under-reporters were consistently more likely to be classified as having inadequate nutrient, as well as energy, intakes. (J Community 2(2) 135∼140, 2000)

• 콘크리트학회지
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• 제3권3호
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• pp.141-148
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• 1991

본 논문은 전단보강이 없는 강섬유보강 고강도 철근콘크리트보의 전단거동에 관한 연구로서 전단스팬비(a/b), 섬유첨가율(Vf)의 변화에 사인장균열 전단응력 및 극한전단응력의 변화를 관찰하였다. 실험결과 섬유첨가율이 증가할수록, 전단스팬비가 감소할수록 사인장균열 전단응력 및 극한전단응력이 증가함을 보여주고 있으며, 특히 섬유첨가율이 증가함에 따라 섬유의 균열억제거동에 의해 극한전단응력이 높게 증가함을 볼 수 있다. 본 연구에 의한 실험결과를 바탕으로 각 변수에 따른 사인장균열 전단응력 및 극한전단응력에 대한 실험식을 제안하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.96-96
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• 2009

The purpose of this study is to clarify the transitional behavior and main factor of excessive welding distortion caused by fabrication process of STS 304 vacuum vessel having double curvature for the efficient quality control of vacuum vessel. In order to do it, the predictive equations of the welding distortion in simple weldment of vacuum vessel were established by conventional finite element analysis. And the principal factor controlling the welding distortion was identified by evaluating the welding distortion of vacuum vessel in each fabrication process with FEA and simplified thermo elastic method. Based on the results, the principal factors of distortion of vacuum vessel were clarified as angular distortion and transverse shrinkage which are a source of excessive out-of plane distortion in the double curved vacuum vessel. It was expected that the FE analysis results of this study could contribute to establish the proper control method of welding distortion for double curved vacuum vessel.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.211-229
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• 2004

The main purpose of this paper is the numerical analysis of the non-linear seismic response of a RC building mock-up. The mock-up is subjected to different synthetic horizontal seismic excitations. The numerical approach is based on a 3D-model involving multilayered shell elements. These elements are composed of several single-layer membranes with various eccentricities. Bending effects are included through these eccentricities. Basic equations are first written for a single membrane element with its own eccentricity and then generalised to the multilayered shell element by superposition. The multilayered shell is considered as a classical shell element : all information about non-linear constitutive relations are investigated at the local scale of each layer, whereas balance and kinematics are checked afterwards at global scale. The non-linear dynamic response of the building is computed with Newmark algorithm. The numerical dynamic results (blind simulations) are considered in the linear and non linear cases and compared with experimental results from shaking table tests. Multilayered shell elements are found to be a promising tool for predictive computations of RC structures behaviour under 3D seismic loadings. This study was part of the CAMUS International Benchmark.