• International Journal of Highway Engineering
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• v.18 no.4
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• pp.63-68
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• 2016

PURPOSES : The nonlinear model of fatigue cracking is typically used for determining the maintenance period. However, this requires that the model parameters be known. In this study, the particle filter (PF) method was used to determine various statistical parameters such as the mean and standard deviation values for the nonlinear model of fatigue cracking. METHODS : The PF method was used to determine various statistical parameters for the nonlinear model of fatigue cracking, such as the mean and standard deviation. RESULTS : On comparing the values obtained using the PF method and the least square (LS) method, it was found that PF method was suitable for determining the statistical parameters to be used in the nonlinear model of fatigue cracking. CONCLUSIONS : The values obtained using the PF method were as accurate as those obtained using the LS method. Furthermore, reliability design can be applied because the statistical parameters of mean and standard deviation can be obtained through the PF method.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.1
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• pp.31-42
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• 2024

In this study, the methodology of determination of base bleed motor data for base bleed projectile based on the NATO standard trajectory model, especially STANAG 4355 Method 2 were presented. Ground combustion experiments and aerodynamic performance firing tests were conducted to determine the drag reduction motor data of the base bleed projectile and this data was described based on the NATO standard ballistic model. The derived drag reduction motor data were input into the ballistic equations to complete the ballistic model and it was confirmed that the calculated predicted trajectory from the ballistic model matched well with the measured trajectory from the aerodynamic performance firing tests.

• Wind and Structures
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• v.7 no.1
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• pp.1-12
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• 2004

Numerical simulation of flow past two-dimensional hill and valley is presented. Application of three turbulence models - the standard and modified (Kato-Launder) $k-{\varepsilon}$ models and standard $k-{\omega}$ model - is discussed. The computational methodology is briefly described. The mean velocity and turbulence intensity profiles, obtained from numerical simulations of flow past the hill, are compared with the experimental data acquired in a boundary-layer wind tunnel at Colorado State University. The mean velocity, turbulence kinetic energy and Reynolds shear stress profiles from numerical simulations of flow past the valley are compared with published experimental data. Overall, the results of simulations employing the standard $k-{\varepsilon}$ model were found to be in a better agreement with the experimental data than those obtained using the modified $k-{\varepsilon}$ model and the $k-{\omega}$ model.

• Communications for Statistical Applications and Methods
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• v.28 no.2
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• pp.189-204
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• 2021

In a regression analysis, a single best model is usually selected among several candidate models. However, it is often useful to combine several candidate models to achieve better performance, especially, in the prediction viewpoint. Model combining methods such as stacking and Bayesian model averaging (BMA) have been suggested from the perspective of averaging candidate models. When the candidate models include a true model, it is expected that BMA generally gives better performance than stacking. On the other hand, when candidate models do not include the true model, it is known that stacking outperforms BMA. Since stacking and BMA approaches have different properties, it is difficult to determine which method is more appropriate under other situations. In particular, it is not easy to find research papers that compare stacking and BMA when regression model assumptions are violated. Therefore, in the paper, we compare the performance among model averaging methods as well as a single best model in the linear regression analysis when standard linear regression assumptions are violated. Simulations were conducted to compare model averaging methods with the linear regression when data include outliers and data do not include them. We also compared them when data include errors from a non-normal distribution. The model averaging methods were applied to the water pollution data, which have a strong multicollinearity among variables. Simulation studies showed that the stacking method tends to give better performance than BMA or standard linear regression analysis (including the stepwise selection method) in the sense of risks (see (3.1)) or prediction error (see (3.2)) when typical linear regression assumptions are violated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.3
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• pp.63-69
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• 2014

This paper studies the strength, fatigue sensitivity, safety factor and lifetimes by means of structural and fatigue analyses of different models of rear doors upon the opening of doors and windows leading to severe fatigue fractures of the window motor components of rear doors. The simulation models were a standard model and other models. The other models, which are denoted here as models I and II, were modified versions of the standard model, with a rib of 3mm and a thickness of 2mm as compared to the standard model. The door was modelled with CATIA V5 and analyzed with the ANSYS program. The material of the rear door was cold rolled steel (DDQ). From the study results, the standard model and model I were confirmed to be less safe upon the opening of the door as compared to the opening of a window in terms of fatigue, but model II was found to be safe for both door and window openings.

• Wind and Structures
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• v.34 no.6
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• pp.483-497
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• 2022

Three-dimensional (3D) computational fluid dynamics (CFD) analysis of flow around a hipped-roof building representative of UK inland conditions are conducted. Unsteady simulations are performed using three variations of the k-ϵ RANS turbulence model namely, the Standard, Realizable, and RNG models, and their predictive capability is measured against current European building standards. External pressure coefficients and wind loading are found through the BS 6399-2:1997 standard (obsolete) and the current European standards (BS EN 1991-1-4:2005 and A1:20101). The current European standard provides a more conservative wind loading estimate compared to its predecessor and the k-ϵ RNG model falls within 15% of the value predicted by the current standard. Surface shear stream-traces and Q-criterion were used to analyze the flow physics for each model. The RNG model predicts immediate flow separation leading to the creation of vortical structures on the hipped-roof along with a larger separation region. It is observed that the Realizable model predicts the side vortex to be a result of both the horseshoe vortex and the flow deflected off it. These model-specific aerodynamic features present the most disparity between building standards at leeward roof locations. Finally, pedestrian comfort and safety criteria are studied where the k-ϵ Standard model predicts the most ideal pedestrian conditions and the Realizable model yields the most conservative levels.

• Environmental Engineering Research
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• v.18 no.3
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• pp.191-197
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• 2013

Republic of Korea announced the reduction target to be around 30% of business as usual greenhouse gas emissions by 2020. College campuses were ranked at the 5th of high energy consumption areas in the building sectors. Target management scheme was designed to set greenhouse gas emissions target including several college campuses. Previous studies showed the amount of greenhouse gas emissions with several assumptions such as the applications of renewable energy systems and light emitting diode lamps, etc. Long-range Energy Alternatives Planning model was utilized to simulate future greenhouse gas emissions. This study sets standard model labs for energy saving action programs by applying guidance studies. It has been deduced that energy saving action programs was responsible for reducing 949.5 kWh for each standard model lab and the total reduction of all 59 model labs in the Engineering College building has been calculated to 56,020.5 kWh. The objective of the study is to provide guidelines on standard model laboratory for greenhouse gas emissions reduction on the campus.

• Journal of Korean Society for Quality Management
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• v.45 no.4
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• pp.611-628
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• 2017

Purpose: This paper deals with establishing Korean national standardization policy through a comparative trend analysis of national standardization strategies and each nation's policy environment. It first investigates the standardization strategies including Korea, the United States, Japan and Germany which is currently leading the 4th Industrial Revolution. Methods: This study compares and analyzes national standardization policies that synthesize the determinants of national standard activities using the STEEP, PEST analysis used for policy environment analysis, and National Standardization Model Canvas(N-STD Model Canvas) applying business model canvas. Results: This study confirms the reasoning and operating system of establishing national standard strategy reflecting the social, economic and political situation and the direction of national standard strategy. Conclusion: Based on the results, this study summarized the policy decision factors necessary for establishing the national standard policy and suggested the management plan in the midpoint of view.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.19-33
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• 1999

This paper is concerned with developing a standard costing model based on the case study of PECT and GCT and analysing their profitability in order to improve operation efficiency and design business strategy. In doing so, the model can be a useful tool to analyze current calculation system of lease charge at the two terminals and to judge whether the level of lease charge currently applied to them is justifiable for their profitability. This paper also deals with break-even analysis of container terminal operating companies on the basis of the model and forecast of their profitability. On the top of that, it tries to look into the arguments and to suggest proposals for improving their profitability.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.362-371
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• 2022

As considerable interests in noise emission from the ships have been increased, International Maritime Organization (IMO) standardized the Underwater Radiated Noise (URN) measurement process of commercial ships in deep seas by enacting the related ISO standard ISO 17208-1 and classification societies responded with the enactment or revision of corresponding notations. According to this trend, a new hybrid underwater sound propagation model based on underwater sound propagation theories was developed and its accuracy on analysis was verified through the result comparison with the results of other generally used models. Using the verified model, each URN propagation characteristics adjusted by the correction methods proposed in the ISO standard and class notations were analyzed and compared in two assumed URN measurement cases. The results showed that the effects of transmission loss corrections in the circumstances with less bottom reflections generally similar but they had rather large differences in the model analysis results with bottom-reflection-dominant conditions. It was concluded that the deep consideration of effective bottom-reflection-correction method should be made in future revisions of ISO standard and class notations.