• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1123-1130
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• 2004

Numerical simulations have been carried out to investigate the effect of nozzle hole geometry on the combustion characteristics of the large diesel engine. 6S90MC-C. Spray and combustion phenomena were examined numerically using FIRE code. Wane breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Predictions on the cylinder peak pressure and NOx emission were first verified with the experimental data to confirm the reliability of numerical calculations. The comparison results showed good agreements within the range of 0.64% and 4.6% respectively. Finally, the effects of fuel spray angle and diameter on the engine performance were investigated numerically to find the optimum nozzle hole geometry considering fuel consumption, NOx emission and heat flux of the combustion chamber wall. It was concluded that the combustion gas recirculation in cylinder by changing fuel injection direction is an effective method to reduce NOx emission by about 10% with increasing fuel oil consumption, 1.4% in a large diesel engine.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.13-14
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• 2005

Multi-dimensional combustion analysis and experiment has been carried out to investigate the effects of the injector nozzle hole diameter and number on the NOx formation and fuel consumption in HYUNDAI HiMSEN engine. The behavior of spray and combustion phenomena in diesel engine was examined by FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation. Wallfilm model suggested by Mundo, et al. and auto-ignition model suggested by Theobald and Cheng were adopted to investigate the spray-wall interaction characteristics and ignition delay. The information of spray angle and spray tip penetration length was extracted from fuel spray visualization experiment and the fuel injection rate profile was extracted from fuel injection system experiment as an input and verification data for the combustion analysis. Next, the nine different nozzle configurations were simulated to evaluate the effect of injector hole diameter and number on the NOx formation and fuel consumption.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.57-65
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• 2008

The characteristics of soot deposition on the cold wall in laminar diffusion flames have been numerically analyzed with a two-dimension with the FDS (Fire Dynamics Simulator). In particular, the effects of surrounding air temperature and wall temperature have been discussed. The fuel for the flame is an ethylene ($C_2H_4$). The surrounding oxygen concentration is 35%. Surrounding air temperatures are 300K, 600K, 900K and 1200K. Wall temperatures are 300K, 600K and 1200K. The soot deposition length defined as the relative approach distance to the wall per a given axial distance is newly introduced as a parameter to evaluate the soot deposition tendency on the wall. The result shows that soot deposition length is increased with increasing the surrounding air temperatures and with decreasing the wall temperature. And the numerical results led to the conclusion that it is essential to consider the thermophoretic effect for understanding the soot deposition on the cold wall properly.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.928-931
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• 2006

Due to their light weight, high stiffness-to-weight and strength-to-weight ratios, and potentially high resistance to environmental degradation, resulting in lower life-cycle costs, polymer composites, are increasingly being considered for use in civil infrastructure applications. Recently, an FRP deck has been installed on a state highway, located in New York State. In this study, a thermal stress analysis was conducted using finite element method to study failure mechanisms of the superstructure. This analysis evaluated small and large temperature gradient effects on the FRP deck considering lightweight of FRP deck and ply orientations at the interface between steel girders and FRP deck Finite element model was verified using the load tests of the bridge deck. Finally, the analytical results shows the possible failure mechanism of FRP deck under various temperature changes and its corresponding index is suddenly varied depending on the rapid change of temperature on the deck plate.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.2
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• pp.70-79
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• 2020

The offshore installation units may be subjected to various accidental loads such as collision from supply vessels, impact from dropped objects, blast load from gas explosion and thermal load from fire. This paper deals with the design and strength evaluation method of the stiffened plate structures in response to a blast load caused by a gas explosion accident. It is a comprehensive review of various items used in actual project such as the size and type of the explosive loads, general design procedure/concept and analysis method. The structural analyses using simple analysis methods based on SDOF model and nonlinear finite element analysis are applied to the particular FPSO project. Also validation studies on the design guidance given by simple analysis method based on SDOF model have also considered several items such as backpressure effects, material behavior and duration time of the overpressure. A good correlation between the prediction made by simple analysis method based on SDOF model and nonlinear finite element analysis can be generally obtained up to the elastic limit.

• Korean Journal of Occupational Health Nursing
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• v.26 no.4
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• pp.227-235
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• 2017

Purpose: This descriptive correlational study investigated the effects of violent experience and resilience on burnout in emergency medical technicians (EMTs). Methods: The participants were 160 EMTs working in fire stations (safety center and local center) located in U, B, and D city. The collected data were analyzed by descriptive statistics, independent t-test, ANOVA, $Scheff{\acute{e}}$ test post-hoc analysis, Pearson correlation coefficients, and multiple regression analysis using IBM SPSS Statistics 20.0. Results: The number of EMTs getting into ambulances was significantly associated with violent experience, resilience, and burnout. Position of EMTs was significantly associated with both resilience and burnout. In the multiple regression analysis, the subscales of durability and optimism in resilience were significantly associated with burnout after controlling for confounding variables. Conclusion: This study indicated that improving durability and optimism in resilience was important to cope with experience of violence and to prevent burnout in EMTs.

• Steel and Composite Structures
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• v.16 no.6
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• pp.657-679
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• 2014

This paper describes a series of compression tests performed on cold-formed steel channel sections with perforations in the web (thermal studs) fabricated from a galvanized steel plate whose thickness ranged from 1.0 mm to 1.6 mm and nominal yield stress was 295 MPa. The structural behavior and performance of thermal studs undergoing local, distortional, or flexural-torsional buckling were investigated experimentally and analytically. The compression tests indicate that the slits in the web had significant negative effects on the buckling and ultimate strength of thin-walled channel section columns. The compressive strength of perforated thermal studs was estimated using equivalent solid channel sections of reduced thickness instead of the studs. The direct strength method, a newly developed and adopted alternative to the effective width method for designing cold-formed steel sections in the AISI Standard S100 (2004) and AS/NZS 4600 (Standard Australia 2005), was calibrated to the test results for its application to cold-formed channel sections with slits in the web. The results verify that the DSM can predict the ultimate strength of channel section columns with slits in the web by substituting equivalent solid sections of reduced thickness for them.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.858-868
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• 2009

A numerical investigation has been carried out about the performance of a 500MW class tangentially coal-fired boiler, focusing on the optimization of separated overfire air (SOFA) position to reduce NOx emission. For this purpose, a comprehensive combination of NOx chemistry models has been employed in the numerical simulation of a particle-laden flow along with solid fuel combustion and heat and mass transfer. A reasonable agreement has been shown in baseline cases for predicted operational parameters compared with experimental data measured in the boiler. A further SOFA calculation has been made to obtain optimum elevation and position of SOFA port. Additionally, clarifying on the effect of SOFA on NOx emission has been carried out in the coal-fired boiler. As a result, this paper is valuable to provide an information about the optimum position of SOFA and the mechanism by which the SOFA would affect NOx emission.

• The Journal of Pediatrics of Korean Medicine
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• v.22 no.1
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• pp.149-162
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• 2008

Objectives The purpose of this study is to investigate that causes of motion sickness in oriental medicine. Methods The internal and external studies about motion sickness were searched Results and Conclusions The motion sickness is induced by conflict of balance system including vestibular, visual and proprioceptive system. The motion sickness is more common in female and in children between 2 and 12 years old. In western medicine, antihistamine and anticholinergic has been used for treatment of motion sickness, but these anti-motion sickness drug turn out to be not a perfect solution and have several side effects. On the other hands, In oriental medical terminology, there is no words equivalent to the "motion sickness", but we consider the motion sickness as state with dizziness, nausea and vomiting. The motion sickness can be induced by either internal or external causes and the internal causes can thought to be a constitutional factor of an individuals, and the general transportation can be an external cause. The important internal cause is a dysfunction of the spleen, stomch(脾胃不調), retention of phlegm and fluids(痰飮), and deficiency of the kidney jing(腎精不足). The wind(風) and fire(火) in the upper part of the body, especially in the head, also can be an important cause of the motion sickness.

• The Journal of Pediatrics of Korean Medicine
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• v.22 no.1
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• pp.163-187
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• 2008

Objectives The aim of this study was to investigate the treatment of precocious puberty in current traditional Chinese medical journals. Methods To figure out diagnosis methods, treatment methods, treatment effects of oriental medicine about precious puberty, Chinese medical journals from China National Knowledge Infrastructure (CNKI) which was published from 1999 to 2007 were analyzed and precocious puberty was also been searched. Results 82 articles were selected. 1. Yin and purging Fire(滋陰瀉火) from traditional Chinese Medicine was usually used. 2. The herbs were almost used such as Rehmannia glutinosa(地黃), Anemarrhena asphodeloides (知母), Phellodendron amurense(黃柏), Thesium chinense(夏枯草), Paeonia suffruticosa Andrews(牧丹皮), Alisma canaliculatum(澤瀉), Testudinis Plastrum(龜板), Paeonia japonica(白芍藥), Bupleurum falcatum(柴胡), Genianae Scabrae Radix(龍膽草). 3. The total improvement rate was 72.50 to 100% Conclusions The oriental medical treatments for precocious puberty were presumed to be effective, but more studies are still needed.