• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.64-70
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• 2008

Temperatures of engine head and liner depend on many factors such as spray and combustion process, coolant passage flow and engine related structures. To estimate the temperature distribution of engine structure, multi-dimensional computational fluid dynamics (CFD) codes have been mainly adopted. In this case, it is of great importance to obtain the realistic wall temperature distribution of entire engine structure. In the present work, a CFD-FEM coupling methodology was presented to address this demand. This approach was applied to a real large-size marine diesel engine. CFD combustion and coolant flow simulations were coupled to FEM temperature analysis. Wall heat flux and wall temperature data were interfaced between combustion simulation and solid component temperature analysis via translator by a commercial CFD package named FIRE by AVL. Heat transfer coefficient and surface temperature data were exchanged and mapped between coolant flow simulation and FEM temperature analysis. Results indicate that there exists the optimum cell thickness near combustion chamber wall to reasonably predict the wall heat flux during combustion period. The present study also shows that the effect of cell refining on predicting in-cylinder pressure during combustion is negligible. Hence, the basic guidance on obtaining the wall heat flux needed for the reasonable CFD-FEM coupling analysis has been established. It is expected that this coupling methodology is a robust tool for practical engine design and can be applied to further assessment of the temperature distribution of other engine components.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.15-21
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• 2009

The design of the stud shear connector of a bridge structure is mostly controlled by the fatigue resistance not by the strength, if it is followed by AASHTO LRFD Bridge Design Specification. This fatigue design code in AASHTO LRFD is based on the research work done by Slutter and Fisher in 1966. These tests seemingly underestimated the fatigue resistance of connectors because of the inherent eccentricity of the one-face test setup which results additional tension forces to the stud. In addition, the stress ranges were not plotted in the log scale, because it was not known at that time that the fatigue resistance of the welded steel structures has a linear relationship of log scales of stress range and number of loading cycles. This study evaluates the test data produced by the Slutter and Fischer, and plot the data on the proper manner. The fatigue push-out test data produced recently by many other researches all around the world are gathered and analyzed, furthermore a design curve is recommended.

• Wind and Structures
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• v.27 no.5
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• pp.325-336
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• 2018

The physical infrastructure of the power systems, including the high-voltage transmission towers and lines as well as the poles and wires for power distribution at a lower voltage level, is critical for the resilience of the community since the failures or nonfunctioning of these structures could introduce large area power outages under the extreme weather events. In the current engineering practices, single circuit lattice steel towers linked by transmission lines are widely used to form power transmission systems. After years of service and continues interactions with natural and built environment, progressive damages accumulate at various structural details and could gradually change the structural performance. This study is to evaluate the typical existing transmission tower-line system subjected to synoptic winds (atmospheric boundary layer winds). Effects from the possible corrosion penetration on the structural members of the transmission towers and the aerodynamic damping force on the conductors are evaluated. However, corrosion in connections is not included. Meanwhile, corrosion on the structural members is assumed to be evenly distributed. Wind loads are calculated based on the codes used for synoptic winds and the wind tunnel experiments were carried out to obtain the drag coefficients for different panels of the transmission towers as well as for the transmission lines. Sensitivity analysis is carried out based upon the incremental dynamic analysis (IDA) to evaluate the structural capacity of the transmission tower-line system for different corrosion and loading conditions. Meanwhile, extreme value analysis is also performed to further estimate the short-term extreme response of the transmission tower-line system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.965-971
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• 2017

The primary objective of this study was to assess the energy efficiency performance of an optimized hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were also assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used to assess effective power. An optimized hull form with minimum resistance was selected given real operating conditions. The effective horsepower of existing and optimized vessels was estimated at three speeds. Resistance performance for an optimized vessel showed a 6 % improvement in effective horsepower at design speed (12 knots) compared to existing vessels. Quasi-propulsive efficiency employed experimental data, while energy efficiency performance was analyzed based on operating days, bunker fuel oil C cost, daily fuel oil consumption and specific fuel oil consumption. Energy efficiency performance for an optimized vessel showed a gain of 30 million won per year in reduced costs at design speed (12 knots) compared to existing vessels.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.432-438
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• 2017

The primary objective of the current work was to develop a standardized retrofit hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used for assessment of effective power. Three retrofit hull forms with minimum resistance were selected given real operating conditions. These vessels were named after customized ready-made hull forms to enable ship owners to make easier choices. The effective power of each vessel was estimated under real operating conditions. Subjects were operated with the lowest draft, and performance for retrofit No. 3 showed an 11-16% improvement in effective power at low speed ranges of 16-18 knots compared to existing vessels. When operated with a middle draft, performance for retrofit No. 3 showed a 6-11% improvement in effective power at low speed ranges compared to existing vessels. When operated with the highest draft, performance for all vessels showed little difference in effective power.

• Wind and Structures
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• v.10 no.3
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• pp.287-300
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• 2007

Wind action is a factor of fundamental importance in the structural design of light or slender constructions. Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by meteorological phenomena such as Extratropical Storms (EPS) or Tropical Storms. Wind effects due to other phenomena, such as thunderstorms, and its combination with EPS winds in so-called squall lines, are simply neglected. In this paper a model that describes the three-dimensional wind velocity field originated from a downburst in a thunderstorm (TS) is proposed. The model is based on a semi empirical representation of an axially-symmetrical flow line pattern that describes a stationary field, modulated by a function that accounts for the evolution of the wind velocity with time. The model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters employed in the model are related to meteorological variables, which are susceptible of statistical assessment. A background wind is also considered, in order to account for the translational velocity of the thunderstorm, normally due to local wind conditions. When the translation of the TS is caused by an EPS, a squall line is produced, causing the highest wind velocities associated with TS events. The resulting vertical velocity profiles were also studied and compared with existing models, such as the profiles proposed by Vicroy, et al. (1992) and Wood and Kwok (1998). The present model predicts horizontal velocity profiles that depend on the distance to the storm center, effect not considered by previous models, although the various proposals are globally compatible. The model can be applied in any region of interest, once the relevant meteorological variables are known, to simulate the excitation due to TS winds in the design of transmission lines, long-span crossings, cable-stayed bridges, towers or similar structures.

• YAKHAK HOEJI
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• v.56 no.2
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• pp.126-135
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• 2012

Purpose: To develop therapeutic duplication criteria for the drugs used for respiratory diseases. Method: Therapeutic duplication was defined as "more than 2 drug ingredient-usage in which each has the same therapeutic effect and combination therapy does not confer additional therapeutic benefit". Respiratory system drugs approved in Korea were examined for the study. The WHO's Anatomical Therapeutic Chemical Classification System was used for grouping of the corresponding drug ingredients. The principles and recommendations on combination usage or multiple drug regimens were reviewed by using the clinical practice guidelines, textbooks, product labelings, and clinical articles. Clinical expert group consultation was performed and expert opinions were incorporated into the final criteria. Results: Nine hundred sixty two drug products with Korean Food and Drug Administration classification codes of 141, 149, 222, and 229 were evaluated, of which 87 active ingredients were composed. The drug ingredients were classified into 12 groups (antihistamines, oral nasal decongestants, leukotriene receptor antagonists, inhaled anticholinergics, inhaled corticosteroids, oral ${\beta}2$-agonists, long-acting ${\beta}2$-agonists, short-acting ${\beta}2$-agonists, xanthines, antiallergics, mucolytics and cough suppressants). The use of more than 2 drug ingredients including the same group was therapeutic duplication, and thus combination should be recommended not to be used. Conclusion: Twelve drug groups were identified as therapeutic duplication criteria. Combination therapy within each group should not be used otherwise therapeutic benefits outweigh potential risks.

• Korean Journal of Construction Engineering and Management
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• v.5 no.4 s.20
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• pp.115-121
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• 2004

The purpose of this study is to develop checklist and manual in order to control and manage military construction project in an environmentally friendly way during each stage in construction. The main contents of the study are as follows. 1) Checklists and manual are developed for reviewing the construction project in advance to meet environment codes and regulations during each stage of project. 2) Critical check points of environment management program focused on waste are identified. 3) A new construction paradigm in harmony with sound environment is established through the application of program for proactive waste control. The study also recommends that, as a future research, the development of a web-based manual be developed for more easy applications in general construction project.

• Journal of Preventive Medicine and Public Health
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• v.51 no.5
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• pp.227-233
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• 2018

Objectives: Chronic diseases, including back pain, result in significant patient morbidity and societal burden. Overall improvement in physical fitness is recommended for prevention and treatment. Walking is a convenient modality for achieving initial gains. Our objective was to determine whether neighbourhood walkability, acting as a surrogate measure of physical fitness, was associated with the presence of chronic disease. Methods: We conducted a cross-sectional study of prospectively collected data from a prior randomized cohort study of 227 patients referred for tertiary assessment of chronic back pain in Ottawa, ON, Canada. The Charlson Comorbidity Index (CCI) was calculated from patient-completed questionnaires and medical record review. Using patients' postal codes, neighbourhood walkability was determined using the Walk Score, which awards points based on the distance to the closest amenities, yielding a score from 0 to 100 (0-50: car-dependent; 50-100: walkable). Results: Based on the Walk Score, 134 patients lived in car-dependent neighborhoods and 93 lived in walkable neighborhoods. A multivariate logistic regression model, adjusted for age, gender, rural postal code, body mass index, smoking, median household income, percent employment, pain, and disability, demonstrated an adjusted odds ratio of 2.75 (95% confidence interval, 1.16 to 6.53) times higher prevalence for having a chronic disease for patients living in a car-dependent neighborhood. There was also a significant dose-related association (p=0.01; Mantel-Haenszel chi-square=6.4) between living in car-dependent neighbourhoods and more severe CCI scores. Conclusions: Our findings suggest that advocating for improved neighbourhood planning to permit greater walkability may help offset the burden of chronic disease.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.665-671
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• 2013

In a Korean Generation IV prototype sodium-cooled fast reactor (SFR), various types of high-temperature heat exchangers such as IHX (intermediate heat exchanger), DHX (decay heat exchanger), AHX (air heat exchanger), FHX (finned-tube sodium-to-air heat exchanger), and SG (steam generator) are to be designed and installed. In this study, the high-temperature design and integrity evaluation of the sodium-to-air heat exchanger AHX in the STELLA-1 (sodium integral effect test loop for safety simulation and assessment) test loop already installed at KAERI (Korea Atomic Energy Research Institute) and FHX in the SEFLA (sodium thermal-hydraulic experiment loop for finned-tube sodium-to-air heat exchanger) test loop to be installed at KAERI have been performed. Evaluations of creep-fatigue damage based on full 3D finite element analyses were conducted for the two heat exchangers according to the high-temperature design codes, and the integrity of the high-temperature design of the two heat exchangers was confirmed.