• Geomechanics and Engineering
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• 제18권2호
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• pp.189-203
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• 2019

Brine leakage is a common phenomenon during construction facilitated by artificial freezing technique, threatening the stability of frozen wall due to the continual thawing of already frozen domain. This paper takes the frequently encountered soft clay in Wujiang District as the study object, and remolded specimens were prepared by mixing calcium chloride solutions at five levels of concentration. Both the deformation and pore water pressure of frozen specimens during thawing were investigated by two-stage loading tests. Three sections were noted from the changes in the strain rate of specimens during thawing at the first-stage load, i.e., instantaneous, attenuated, and quasi-stable sections. During the second-stage loading, the deformation of post-thawed soils is closely correlated with the dissipation of pore water pressure. Two characteristic indexes were obtained including thaw-settlement coefficient and critical water content. The critical water content increases positively with salt content. The higher water content of soil leads to a larger thaw-settlement coefficient, especially at higher salt contents, based on which an empirical equation was proposed and verified. The normalized pore water pressure during thawing was found to dissipate slower at higher salt contents, with a longer duration to stabilize. Three physical indexes were experimentally determined such as freezing point, heat conductivity and water permeability. The freezing point decreases at higher salt contents, especially as more water is involved, like the changes in heat conductivity. The water permeability maintains within the same order at the considered range of salt contents, like the development of the coefficient of consolidation. The variation of the pore volume distribution also accounts for this.

• 한국공간구조학회논문집
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• 제19권4호
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• pp.69-76
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• 2019

A stadium roof that uses the pin-jointed spatial truss system has to be designed by taking into account the unstable phenomenon due to the geometrical non-linearity of the long span. This phenomenon is mainly studied in the single-free-node model (SFN) or double-free-node model (DFN). Unlike the simple SFN model, the more complex DFN model has a higher order of characteristic equations, making analysis of the system's stability complicated. However, various symmetric conditions can allow limited analysis of these problems. Thus, this research looks at the stability of the DFN model which is assumed to be symmetric in shape, and its load and equilibrium state. Its governing system is expressed by nonlinear differential equations to show the double Duffing effect. To investigate the dynamic behavior and characteristics, we normalize the system of the model in terms of space and time. The equilibrium points of the system unloaded or symmetrically loaded are calculated exactly. Furthermore, the stability of these points via the roots of the characteristic equation of a Jacobian matrix are classified.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.224-231
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• 2010

최근 발표된 GvdW(Generalized van der Waals) EOS에서는 상호작용이 vdWf(van der Waals force)뿐이라고 여겨지는 구체특성의 비선형적 입자에 대해 임계영역에서의 상태 특성이 잘 기술될 수 있음을 보였다. 그러나 기존의 논문에서는 선형성을 갖는 입자의 형태나 정전기적 인력 등 추가적인 상호작용이 존재하는 입자에 대해서도 GvdW가 정확성을 나타내는지에 대한 분석이 이루어지지 않아, GvdW의 범용성에 대한 논란의 여지가 남아있다. 따라서 본 논문에서는 선형성을 갖는 입자인 포화 알칸 유도체 류(R=methane, ethane, propane, butane)와 정전기적 인력이 극한적으로 나타나는 포화 아민 유도체 류($RNH_2$, R=methyl-, ethyl-, propyl-amine)에 대한 임계영역 시뮬레이션을 위하여 이들 입자들에 대한 GvdW의 파라미터 값을 정의하였으며, 이를 바탕으로 최근에 발표된 기존의 상태방정식들과 비교 분석하였다. 시뮬레이션 결과 포화 알칸 유도체 류와 포화 아민 유도체 류 입자에 대하여 GvdW는 기존의 방정식들보다 측정값에 더 가까운 정확한 임계영역 특성이 나타남을 확인할 수 있었다. 특히 분자량이 큰 부탄에 있어서는 GvdW EOS만이 임계점에 정확하게 근접함을 알 수 있었다.

• 한국물환경학회지
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• 제23권6호
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• pp.913-919
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• 2007

This study was conducted to develop a model equation to estimate the delivered point and nonpoint pollutant loads, which are critical factor to determine the water quality of watersheds. The model equation was developed by considering various factors such as biological removal and delivered distance of pollutants, basin shape and geomorphic runoff condition. The parameters for the model equation were estimated in 3 periods, which are October to March, April to June, and July to September. As a parameter, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$, a and b for $BOD_5$-delivered pollutant loads were estimated to be 0.010~0.0155, 0.051, -0.033, 0.018~0.050 and 0.93, respectively. For T-N, ${\alpha}_p$, ${\alpha}_n$, ${\beta}$ a and b were estimated to be 0.0060~0.0140, 0.014, -0.02, 0.044~0.079 and 0.93, respectively. The same parameters for T-P were estimated to be 0.0160, 0.014, -0.0250, 0.015 and 1.21, respectively. The relationship, $E^2$ (Model efficiency), between observed and calculated delivered pollutant loads showed 0.65 for $BOD_5$, 0.81 for T-N, and 0.66 for T-P, respectively. Consequently, the model equation is effective to estimate delivered pollutant loads for TMDL.

• Spatial Information Research
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• 제14권4호
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• pp.363-377
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• 2006

본 연구에서는 개정범용토양유실공식(RUSLE: Revised Universal Soil Loss Equation)을 이용하여 미국 South Carolina 주 Congaree 유역에 대한 평균 연간 토양 유실량을 산출 하였으며 비점오염원 토양 유실 민감지역을 추출하였다. 평균 연간 토양 유실량은 강우-유출 침식성 인자, 토양침식성 인자, 지면특성 인자, 식생피복 인자, 그리고 토양보존 인자의 곱으로 계산할 수 있으며, 토양 유실 민감지역은 토양 유실량이 토양침식 허용량을 초과하는 지역으로 추출할 수 있다. 연구 결과, 전체 면적의 10% 이상의 면적이 비점오염원 토양 유실 민감 지역으로 확인되었으며, Congaree 유역의 7개 소유역중 Congaree Creek, Gills Creek 소유역의 도심지역과 Cedar Creek 소유역의 농업지역에서 가장 심각한 토양 유실의 위험이 나타났다. 관심 지역의 인위적, 자연적 변화가 토양 유실에 가져오는 영향을 살펴보기 위한 시범 모형으로서, 개정범용토양유실공식에 기초한 내장형 모형이 Visual Basic for Applications (VBA)를 이용하여 ESRI사의 ArcGIS ArcMap 9.0에서 사용할 수 있도록 개발되었다. 이 내장형 모형에서 사용자는 각 소유역의 토지 피복, 식생 유형, 지표 식생 유형, 경사, 작물 유형, 경작 방식 등을 변경시킴으로써 C, LS, P 인자를 변화시킬 수 있으며, 계산된 평균 연간 토양 유실량과 민감 지역을 현재 상태의 값들과 비교하여 앞으로의 토양유실 관리를 위한 주요 정보로 사용할 수 있다.

• 열처리공학회지
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• 제30권4호
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• pp.156-163
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• 2017

In the present study, we investigated the optimal austenitizing temperature of high-alloyed tool steels from an industrial point of view. Austenitizing temperatures for manufacturing 25 commercial tool steels were surveyed with their alloy compositions. The relationship between the austenitizing temperatures and the critical equilibrium temperatures by thermodynamic-based calculation was analyzed and a correlation was found. Based on the austenitizing temperatures of 25 commercial tool steels and the thermodynamic calculation results, we proposed a simple equation to predict an optimal austenitizing temperature to achieve superior mechanical properties of high-alloyed tool steels. The applicability of the proposed equation was experimentally validated with a new developed tool steel.

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.313-334
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• 2005

The paper presents a new approach for the analysis of slope stability that is based on the numerical solution of a differential equation, which describes the thrust force distribution within the potential sliding mass. It is based on the evaluation of the thrust force value at the endpoint of the slip line. A coupled approximation of the slip and thrust lines is applied. The model is based on subdivision of the sliding mass into slices that are normal to the slip line and the equilibrium differential equation is obtained as the slice width approaches zero. Opposed to common iterative limit equilibrium procedures the present method is straightforward and gives an estimate of slope stability at the value of the safety factor prescribed in advance by standard requirements. Considering the location of the thrust line within the soil mass above the trial slip line eliminates the possible development of a tensile thrust force in the stable and critical states of the slope. The location of the upper boundary point of the thrust line is determined by the equilibrium of the upper triangular slice. The method can be applied to any smooth shape of a slip line, i.e., to a slip line without break points. An approximation of the slip and thrust lines by quadratic parabolas is used in the numerical examples for a series of slopes.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.657-665
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• 2021

The study aims to assess the acceptance of social commerce and participate in social commerce amongst Omani people. The questions of the survey Instrument were prepared in English later converted into Arabic. The survey instrument was having two parts; the first part sought the demographic information like age, gender, education, occupation etc. The second part of the instrument was related to the variables, which was in 5-point Likert scale, where 5 means strongly agree while 1 meaning strongly disagree. The data was collected using online and offline surveys, making the number of the valid responses to 478. A conceptual model was developed using the following variables. The selected variables such as "Familiarity" (F), "Trust" (T), "Perceived usefulness" (PU), "Perceived ease of use" (PEU), "Intention to Purchase" (IP). The hypothesis was tested using structural equation modelling. The results indicate that all six hypotheses were supported. The F, T and PEU, and PU was found to be positive and significant related to intention to purchase (p-value 0.003, 0.001, 0.000. & 0.007). Amongst the four, p value of F was found to be the lowest and PU was found to be the highest. This indicate F was strong indicator of IP as compared to others. PUE relates to PU, and F was related to IP.

• Journal of the Korean Physical Society
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• 제73권11호
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• pp.1774-1786
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• 2018

Phenotypic variation among clones (individuals with identical genes, i.e. isogenic individuals) has been recognized both theoretically and experimentally. We investigate the effects of phenotypic variation on evolutionary dynamics of a population. In a population, the individuals are assumed to be haploid with two genotypes : one genotype shows phenotypic variation and the other does not. We use an individual-based Moran model in which the individuals reproduce according to their fitness values and die at random. The evolutionary dynamics of an individual-based model is formulated in terms of a master equation and is approximated as the Fokker-Planck equation (FPE) and the coupled non-linear stochastic differential equations (SDEs) with multiplicative noise. We first analyze the deterministic part of the SDEs to obtain the fixed points and determine the stability of each fixed point. We find that there is a discrete phase transition in the population distribution when the probability of reproducing the fitter individual is equal to the critical value determined by the stability of the fixed points. Next, we take demographic stochasticity into account and analyze the FPE by eliminating the fast variable to reduce the coupled two-variable FPE to the single-variable FPE. We derive a quasi-stationary distribution of the reduced FPE and predict the fixation probabilities and the mean fixation times to absorbing states. We also carry out numerical simulations in the form of the Gillespie algorithm and find that the results of simulations are consistent with the analytic predictions.

• 한국식품조리과학회지
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• 제27권2호
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• pp.61-71
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• 2011

This study was conducted to estimate the shelf-life of Kimbab manufactured using a Hazard Analysis and Critical Control Point (HACCP). We performed a microbiological verification after applying the HACCP plan to Kimbab. Additionally, the shelf-life of Kimbab at each holding temperature was calculated as a regression equation between the aerobic plate counts and holding time during the storage period. The critical control points of the HACCP plan, that were applied to Kimbab, included: cold-holding of refrigerated foods, checking the endpoint cooking temperature of heated food, and cold-holding of cooked foods. As a result of the microbiological verification of Kimbab, the aerobic plate counts averaged 3.46 log CFU/g. In contrast, the coliforms, E. coli, Staphylococcus aureus, and Salmonella spp. were not detected in any of the samples. The estimated shelf-life of Kimbab was calculated to be 45 hours at $10^{\circ}C$, 29 hours at $15^{\circ}C$, 6 hours at $25^{\circ}C$ and 3 hours at $35^{\circ}C$. In conclusion, manufacturers should apply a prerequisite program and a HACCP system for a safe consumption of ready-to-eat foods and label products with a proper shelf-life. Distributors should control the proper holding time-temperature until sale and consumers should eat immediately after purchasing ready-to-eat foods.