• Journal of the Society of Naval Architects of Korea
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• v.60 no.4
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• pp.222-230
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• 2023

In the present work, the scale effect on the Boil-Off Rate (BOR) was investigated based on an analytical method to systematically evaluate the thermal performance of a Liquefied Natural Gas (LNG) Cargo Containment System (CCS). A two-dimensional thermal resistance network model was developed to accurately estimate the heat ingress into the CCS from the outside. The analysis was performed for the KC-1 LNG membrane tank under the IGC and USCG design conditions. The ballast compartment of both the LNG tank and cofferdam was divided into six sections and a thermal resistance network model was made for each section. To check the validity of the developed model, the analysis results were compared with those from existing literature. It was shown that the BOR values under the IGC and USCG design conditions were agreed well with previous numerical results with a maximum error of 1.03% and 0.60%, respectively. A SDR, the scale factor of the LNG CCS was introduced and the BOR, air temperature of the ballast compartment, and the surface temperature of the inner hull were obtained to examine the influence of the SDR on the thermal performance. Finally, a correlation for the BOR was proposed, which could be expressed as a simple formula inversely proportional to the SDR. The proposed correlation could be utilized for predicting the BOR of a full-scale LNG tank based on the BOR measurement data of lab-scale model tanks.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.429-439
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• 2009

When Catastrophic extreme flood occurs due to dam break, the response time for flood warning is much shorter than for natural floods. Numerical models can be powerful tools to predict behaviors in flood wave propagation and to provide the information about the flooded area, wave front arrival time and water depth and so on. But flood wave propagation due to dam break can be a process of difficult mathematical characterization since the flood wave includes discontinuous flow and dry bed propagation. Nevertheless, a lot of numerical models using finite volume method have been recently developed to simulate flood inundation due to dam break. As Finite volume methods are based on the integral form of the conservation equations, finite volume model can easily capture discontinuous flows and shock wave. In this study the numerical model using Riemann approximate solvers and finite volume method applied to the conservative form for two-dimensional shallow water equation was developed. The MUSCL scheme with surface gradient method for reconstruction of conservation variables in continuity and momentum equations is used in the predictor-corrector procedure and the scheme is second order accurate both in space and time. The developed finite volume model is applied to 2D partial dam break flows and dam break flows with triangular bump and validated by comparing numerical solution with laboratory measurements data and other researcher's data.

• The Korean Journal of Franchise Management
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• v.8 no.2
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• pp.37-47
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• 2017

Purpose - Recently, the food service franchise market is experiencing rapid growth and competition is intensifying. Therefore, consumer choice has expanded, and reputation management has become important as a strategy for survival of corporations. Based on previous studies, this research proposed the theoretical framework about the structural relationships among reputation, trust(cognitive trust, affective trust), and loyalty. Research design, data, and methodology - This study examined the structural relationship between reputation, trust, and loyalty from the customer's perspective. Based on comprehensive validation procedures across nine food service Franchise firm types, This study found support for a five-dimensional scale with the following dimensions: Customer Orientation, Employer Brand, Reliable and Financially Strong Company, Product and Service Quality, and Social and Environmental Responsibility. In order to verify the research purposes, research model and hypotheses were developed. The data were collected from 227 food service franchise consumers through online survey. The data was analyzed with SPSS 24.0 and Amos 23.0 statistical program. Result - The results of the study are as follows. First, customer orientation, reliable·financially strong company and product·service quality have significant impact on corporate cognitive trust. And employer brand, product/service quality and social·environmental responsibility have significant impact on corporate affective trust. Second, cognitive trust and affective trust have significant impacts on consumer loyalty. Conclusions - The implications of this study are following as: From the theoretical perspective, this study considers trust as two dimensions such as cognitive and affective, not a single dimension, and identify what dimensions of franchise firms affect consumers' reputation perception and in turn lead cognitive and affective trust, and loyalty. This study also provides several managerial implications. In the franchise market where competition is intensifying, it is very important to analyze the attitudes of consumers in order to gain an advantage in competition with other competitors. In this study, it is meaningful that the study was conducted on consumers who have experience using a restaurant franchise company. Also, reputation is necessary to pay attention to the company because it is an important variable that strengthens with customer through confidence in food service franchise business, and leads loyalty and consumer consumption. Therefore, marketers should develop marketing strategies considering various reputation factors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.261-270
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• 2008

Even though there is a great deal of progress in a numerical method of high caliber like SPH, it is very rarely deployed in a water resources community. Despite the great stride in computing environment, depth averaged approach like a nonlinear shallow equation is still efficient tool for flood routing in large watershed, but it can give some misleading information like the inundation height of flood. In this rationale, we numerically simulate the flow into the dry channel, dry channel with an obstacle triggered by the collapse of a two dimensional water column using SPH (Smoothed Particle Hydrodynamics) in order to boost the application of numerical method of high caliber like SPH in a water resources community. As a most severe test of the robustness of SPH, we also carry out the simulation of the flow through a clearance into the wet channel driven by the rapid removal of a water gate. As a hydrodynamic model, we used the Navier-Stokes equation, a numerical integration of which was carried out using SPH. To verify the validity of newly proposed numerical model, we compare the numerically simulated flow with the others in the literature mainly from VOF and MAC, and hydraulic experiments by Martin and Moyce (1952), Koshizuka et al. (1995) and Janosi et al. (2004). It was shown that agreements between the numerical results in this study and hydraulic experiments are remarkable.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.861-872
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• 2006

The element free Galerkin method is extended by the local partition of unity method to model the cohesive cracks in two dimensional continuum. The shape function of a particle whose domain of influence is completely cut by a crack is enriched by the step enrichment function. If the domain of influence contains a crack tip inside, it is enriched by a branch enrichment function which does not have the LEFM stress singularity. The discrete equations are obtained directly from the standard Galerkin method since the enrichment is only for the displacement field, which satisfies the local partition of unity. Because only particles whose domains of influence are influenced by a crack are enriched, the system matrix is still sparse so that the increase of the computational cost is minimized. The condition for crack growth in dynamic problems is obtained from the material instability; when the acoustic tensor loses the positive definiteness, a cohesive crack is inserted to the point so as to change the continuum to a discontiuum. The crack speed is naturally obtained from the criterion. It is found that this method is more accurate and converges faster than the classical meshless methods which are based on the visibility concept. In this paper, several well-known static and dynamic problems were solved to verify the method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.881-893
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• 2008

The major objective of this study is to investigate the fatigue damage factor evaluation of immovability crossing for railway turnout by the field test and qualitative analysis. From the field test results of the servicing turnout crossing and qualitative analysis with frictional wear which section stiffness decreased, it was evaluated fatigue life of servicing turnout crossing. Most design practices have not taken advantage of the advanced theories in the modern fracture mechanics and finite element analysis due to complexity of analysis as well as the large quantity of vaguely defined parameters in actual designs. This paper considers fatigue problems in turnout crossing using effective analytical and design tools from the field of qualitative constraint reasoning. A set of software modules was developed for fatigue analysis and evaluation, which is easily applicable in engineering practices of designers. The techniques enable the use complex analysis formulations to tackle practical problems with uncertainties, and present the design outcome in two-dimensional design space solution. Appropriate engineering assumptions and judgments in carrying out these procedures, often the most difficult part for practicing engineers, can be partially produced by using qualitative reasoning to define the trends and ranges, interval constraint analysis to derive the controlling parameters, as well as design space to account for practical experience.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.1025-1032
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• 2006

Sensor modeling of high-resolution satellites is a prerequisite procedure for mapping and GIS applications. Sensor models, describing the geometric relationship between scene and object, are divided into two main categories, which are rigorous and approximate sensor models. A rigorous model is based on the actual geometry of the image formation process, involving internal and external characteristics of the implemented sensor. However, approximate models require neither a comprehensive understanding of imaging geometry nor the internal and external characteristics of the imaging sensor, which has gathered a great interest within photogrammetric communities. This paper described a comparison between rigorous and various approximate sensor models that have been used to determine three-dimensional positions, and proposed the appropriate sensor model in terms of the satellite imagery usage. Through the case study of using IKONOS satellite scenes, rigorous and approximate sensor models have been compared and evaluated for the positional accuracy in terms of acquirable number of ground controls. Bias compensated RFM(Rational Function Model) turned out to be the best among compared approximate sensor models, both modified parallel projection and parallel-perspective model were able to be modelled with a small number of controls. Also affine transformation, one of the approximate sensor models, can be used to determine the planimetric position of high-resolution satellites and perform image registration between scenes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.887-899
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• 2006

The aim of this study is to investigate a correlation between fundamental data on aerodynamic characteristics of bridge girder cross-sections, such as aerodynamic force coefficients and flutter derivatives, and their aerodynamic behaviour. The section model tests were carried out in three stages. In the first stage, seven deck configurations were studied, namely; Six 2-edge girders and one box girder. In this stage, changes in aerodynamic force coefficients due to geometrical shape of girders, incidence angle of flow, wind directions and turbulence intensities were studied by static section model tests. In the second stage, the dynamic section model tests were carried out to investigate the relativity of static coefficients to dynamic responses. And finally, the two-dimensional (lift-torsion) aerodynamic derivatives of three bridge deck configurations were investigated by dynamic section model tests. The aerodynamic derivatives can be best described as a representation of the aerodynamic damping and the aerodynamic stiffness provided by the wind for a given deck geometry. The method employed here to extract these unsteady aerodynamic properties is known as the initial displacement technique. It involves the measurement of the decay in amplitude with time of an initial displacement of the deck in heave and torsion, for various wind speeds, in smooth flow. It is suggested that the proposed aerodynamic force coefficients and flutter derivatives of bridge girder sections will be potentially useful for the aeroelastic analysis and buffeting analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3B
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• pp.279-289
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• 2006

The reconstruction of low dimension nonlinear behavior from the hydrologic time series has been an active area of research in the last decade. In this study, we present the applications of a powerful state space reconstruction methodology using the method of Support Vector Machines (SVM) to the Great Salt Lake (GSL) volume. SVMs are machine learning systems that use a hypothesis space of linear functions in a Kernel induced higher dimensional feature space. SVMs are optimized by minimizing a bound on a generalized error (risk) measure, rather than just the mean square error over a training set. The utility of this SVM regression approach is demonstrated through applications to the short term forecasts of the biweekly GSL volume. The SVM based reconstruction is used to develop time series forecasts for multiple lead times ranging from the period of two weeks to several months. The reliability of the algorithm in learning and forecasting the dynamics is tested using split sample sensitivity analyses, with a particular interest in forecasting extreme states. Unlike previously reported methodologies, SVMs are able to extract the dynamics using only a few past observed data points (Support Vectors, SV) out of the training examples. Considering statistical measures, the prediction model based on SVM demonstrated encouraging and promising results in a short-term prediction. Thus, the SVM method presented in this study suggests a competitive methodology for the forecast of hydrologic time series.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3B
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• pp.301-310
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• 2006

Typically, we needs enormous national budget for the flood control project and so the project usually has big influence on the national economy. Therefore, the reliable estimation of flood damage is the key issue for the economic analysis of the flood control project. This study aims to provide a GIS based technique for distributed flood damage estimation. We consider two aspects of engineering and economic sides, which are the inundation analysis and MD-FDA (Multi-Dimensional Flood Damage Analysis), for the flood damage assessment. We propose the analysis framework and data processing using GIS for assessing flood damages. The proposed methodology is applied to the flood control channel project for flood disaster prevention in Mokgamcheon/Dorimcheon streams and this study presents the detailed GIS database and the assessment results of flood damages. This study may have the worth in improving practical usability of MD-FDA and also providing research direction for combining economic side with the engineering aspect. Also this distributed technique will help decision-making in evaluating the feasibility of flood damage reduction programs for structural and nonstructural measures.