• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.1
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• pp.19-27
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• 2024

Globalization has significantly elevated the importance of the aviation sector in the global economy. However, despite the pivotal role airports play, some have struggled to maintain sustainability. Based on these problems, the purpose of this study is to understand the effect of Regional airports' perceived critical success factors and its effect on the performance of airports. This paper surveyed personnel who worked at regional airport and conducted an empirical analysis based on survey results. The study validates hypotheses pertaining to the critical success factors within regional airports and its influences on management performance. The comprehensive analysis reveals that, central governments has a positive impact on the regional airports' team·process·organizational factors. Furthermore, the team and organizational factors exerts positive influence on the management performance. This paper offers empirical insights to regional airports's critical success factors and its impact on airports' performance.

• Structural Engineering and Mechanics
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• v.4 no.2
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• pp.139-148
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• 1996

Vector algorithms and the relative importance of the four basic modules (computation of element stiffness matrices, assembly of the global stiffness matrix, solution of the system of linear simultaneous equations, and calculation of stresses and strains) of a finite element computer program for inelastic analysis of reinforced concrete shells are presented. Performance of the vector program is compared with a scalar program. For a cooling tower problem, the speedup factor from the scalar to the vector program is 34 for the element stiffness matrices calculation, 25.3 for the assembly of global stiffness matrix, 27.5 for the equation solver, and 37.8 for stresses, strains and nodal forces computations on a Gray Y-MP. The overall speedup factor is 30.9. When the equation solver alone is vectorized, which is computationally the most intensive part of a finite element program, a speedup factor of only 1.9 is achieved. When the rest of the program is also vectorized, a large additional speedup factor of 15.9 is attained. Therefore, it is very important that all the modules in a nonlinear program are vectorized to gain the full potential of the supercomputers. The vector finite element computer program for inelastic analysis of RC shells with layered elements developed in the present study enabled us to perform mesh convergence studies. The vector program can be used for studying the ultimate behavior of RC shells and used as a design tool.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.345-354
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• 2022

It is easy for a ship passing through confined waters to be exposed in dangers of collisions and grounding due to different hydrodynamic responses. Since marine accidents can cause significant impacts on environments, global economy, and human lives, it is necessary to study the effect of shallow water on hydrodynamic performance of a ship. In this paper, the effect of water depth on resistance performance was investigated using CFD analysis as an initial study for improving navigational safety of a large container ship under confined waters. After a CFD set-up for deep water condition was validated and verified by comparing CFD analysis with model test results, CFD calculations according to ship speed and water depth were conducted. The features were investigated in terms of tendency and physical knowledge related to resistance performance. The increase of resistance due to shallow water effect was reviewed with empirical formula suggested from SWABE JIP. Speed loss due to shallow water effect was additionally reviewed from estimated delivered power according to ship speed and water depth.

• Tribology and Lubricants
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• v.39 no.3
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• pp.94-101
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• 2023

Automotive wheel bearings are a critical component of vehicles that support their weight and facilitate rotation. Life and stiffness are significant performance characteristics of wheel bearings. Designing wheel bearings involves finding optimal design variables that satisfy both performances. CO₂ emission reduction and fuel efficiency regulations attribute to the recent increase in design requirements for lightweight and compact automotive parts while maintaining performance. However, achieving a design that maintains performance while reducing weight poses challenges, as performance and weight are generally inversely proportional. In this study, we perform design optimization of automotive wheel bearings considering life and stiffness. We develop a program that calculates the basic rated life and modified rated life based on international standards for evaluating the life of wheel bearings. We develop a regression equation using regression analysis to address the time-consuming stiffness analysis during repetitive analysis. We perform ANOVA and main effect analyses to understand the statistical characteristics of the developed regression equation. Furthermore, we verify its reliability by comparing the predicted and test results. We perform design optimization using the developed life prediction program, stiffness regression equation and weight regression equation. We select bearing specifications and geometry as design variables, weight as the cost function, and life and stiffness as constraints. Through design optimization, we investigate the influence of design variables on the cost function and constraints by comparing the initial and optimal design values.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1245-1254
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• 2008

Proposing a method for the estimation of the social cost for global warming impact (external cost) is the aim of this paper. Both the endpoint approach and conjoint analysis were applied to estimating the social cost for global warming. The endpoint approach was used to assess the damage on the safeguard subjects by global warming due to the emission of greenhouse gases into the atmosphere. The conjoint analysis was used to estimate the economic values for safeguard subjects which measure the social preferences and willingness to pay (WTP) on safeguard subjects. The economic values of human health and social asset were estimated at 62,261,700 Won / DALY (yr) and 10,000 Won / 10,000 Won, respectively. Moreover, cost factors of GHGs were calculated by multiplying the damage factor which is quantified the unit damage on safeguard subject and the economic value. In the case of CO$_2$, the cost factor was calculated at 13.52 Won / kg (13,520 Won / ton). External cost of products or services can be calculated by multiplying the GHG inventory result of products or services by the cost factor of each GHG. inventory.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.3
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• pp.1-14
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• 2024

Gaining an accurate 3D stream geometry has become feasible with Unmanned Aerial Vehicle (UAV), which is crucial for better understanding stream hydrodynamic processes. The objective of this study was to investigate series of filters to remove stream vegetation and propose the best method for generating Digital Terrain Models (DTMs) using UAV-based point clouds. A stream reach approximately 500 m of the Bokha stream in Icheon city was selected as the study area. Point clouds were obtained in August 1st, 2023, using Phantom 4 multispectral and Zenmuse L1 for Structure from Motion (SfM) and Light Detection And Ranging (LiDAR) respectively. Three vegetation filters, two morphological filters, and six composite filters which combined vegetation and morphological filters were applied in this study. The Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were used to assess each filters comparing with the two cross-sections measured by leveling survey. The vegetation filters performed better in SfM, especially for short vegetation areas, while the morphological filters demonstrated superior performance on LiDAR, particularly for taller vegetation areas. Overall, the composite filters combining advantages of two types of filters performed better than single filter application. The best method was the combination of Progressive TIN (PTIN) and Color Indicies of Vegetation Extraction (CIVE) for SfM, showing the smallest MAE of 0.169 m. The proposed method in this study can be utilized for constructing DTMs of stream and thus contribute to improving the accuracy of stream hydrodynamic simulations.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.37
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• pp.361-389
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• 2008

The purpose of this study is to detect the factors which have an effect on transformation level and performance and to provide the ways of successful transformation and vitalization from OEM to ODM. This study was proceeded by an empirical analysis. A model and hypotheses were set up and they were verified through the empirical analysis. Those factors were divided into four, inner company factors, strategic factors, core competence factors and purchase determining factors. In the result of the model suitability analysis on the study model of relationship among 'influencing factors of ODM transformation - ODM transformation level-export performance', every factors, $X^2=912.067$, DF=261, p value=0.000, GFI=0.737, AGFI=0.620, NFI=0.786, IFI=0.837, CFI=0.834, Q value=3.495 were rather insufficient to be a good model, but they were good enough for the general analysis. Taking these accounts into consideration, this study suggests the following implications. First, making a plan and setting up strategies in advance are required. Second, financial plan has to be prepared. Third, trends in global markets have to be analyzed. Fourth, companies have to focus on developing new materials and products through R&D. Fifth, quality competitiveness and quality control systems are required.

• Structural Engineering and Mechanics
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• v.89 no.5
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• pp.491-505
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• 2024

This study evaluates the seismic performance of a premodern six story reinforced concrete building typology designed during the communism period of Albania and build throughout the country. During the November 26, 2019 Earthquake in Albania, the most affected reinforced concrete buildings were among the old templates, lacking shear walls and inadequate reinforcement details which suffer from concrete aging. The mathematical model of the selected building is done in the environments of ZeusNL software, developed especially for earthquake engineering applications. The capacity curve of the structure is gained using the conventional static nonlinear analysis. On the other hand, the demand estimation is utilized using one of the recent methods known as Incremental Dynamic Analysis with a set of 18 ground motion records. The limit states in both curves are defined based on the modern guidelines. For the pushover, immediate occupancy (IO), life safety (LS) and collapse prevention (CP) are plotted in the same graph with capacity curve. Furthermore, on each IDA derived, the IO, CP and global instability (GI) are determined. Moreover, the IDA fractiles are generated as suggested by the literature, 16%, 50% (median) and 84%. In addition, the comparative assessment of the IDA median with capacity curve shows good correlation points. Lastly, this study shows the approach of determination of LS in IDA fractiles for further vulnerability assessment based on the local seismic hazard map with 95 and 475 return period.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.447-470
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• 2014

Numerical simulation of the non-linear behavior of (RC) structural walls subjected to severe earthquake ground motions requires a reliable modeling approach that includes important material characteristics and behavioral response features. The objective of this paper is to optimize a simplified method for the assessment of the seismic response and damage development analyses of an RC structural wall building using macro-element model. The first stage of this study investigates effectiveness and ability of the macro-element model in predicting the flexural nonlinear response of the specimen based on previous experimental test results conducted in UCLA. The sensitivity of the predicted wall responses to changes in model parameters is also assessed. The macro-element model is next used to examine the dynamic behavior of the structural wall building-all the way from elastic behavior to global instability, by applying an approximate Incremental Dynamic Analysis (IDA), based on Uncoupled Modal Response History Analysis (UMRHA), setting up nonlinear single degree of freedom systems. Finally, the identification of the global stiffness decrease as a function of a damage variable is carried out by means of this simplified methodology. Responses are compared at various locations on the structural wall by conducting static and dynamic pushover analyses for accurate estimation of seismic performance of the structure using macro-element model. Results obtained with the numerical model for rectangular wall cross sections compare favorably with experimental responses for flexural capacity, stiffness, and deformability. Overall, the model is qualified for safety assessment and design of earthquake resistant structures with structural walls.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.10-18
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• 2014

This study carried out to evaluate the hydration heat analysis and fundamental characteristics such as air content, slump, compressive strength and dry shrinkage according to concrete with premixed cement, ternary concrete and OPC concrete for using concrete with premixed cement. The results of experiment are founded that concrete with premixed cement have sufficient performances such as workability, compressive strength and dry shrinkage. Also, the results of hydration heat analysis are founded that concrete with premixed cement have more performance than ternary concrete and OPC concrete at a point of view for the quality control such as thermal crack reducing and economic benefit. Therefore, it is desirable that concrete with premixed cement should be used to rise durability performance and convenience of maintenance.