• 시스템엔지니어링학술지
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• 제15권2호
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• pp.57-65
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• 2019

The weapon system applies the rule that the system engineering procedure must be applied at the acquisition stage. Naval ships, which are one of the important naval weapon systems, take a long period of time to acquire, and the leadership must be commissioned. Therefore, in order to acquire a naval ship, high risk management is necessary, and it is necessary to promote business success through effective application of system engineering which is a scientific management method. However, in the case of naval ships, there are no specific procedures and methods for applying the system engineering. Therefore, research on application method of system engineering which can be easily used by person in charge is necessary. This should have a simple approach to ensure effective business performance by systematically refining and simplifying existing works. QFD (Quality Function Deployment) is a way to improve product satisfaction, impress customers, reduce defective products, reduce design errors, and reduce costs. This systematically develops these mutual relationships by converting the needs of customers into quality characteristics of products and defining them as the design quality of products considering the functions, quality, and process elements of parts. The purpose of this research is to present concrete methodology at the practical level using QFD in a way to ensure traceability of requirements which is an important element of system engineering.

• 한국자동차공학회논문집
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• 제17권4호
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• pp.93-100
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• 2009

Intake/exhaust valve timing and exhaust cam lift were changed to control the internal exhaust gas recirculation (IEGR) and combustion phase of homogeneous charge compression ignition (HCCI) engine. To measure the IEGR rate, in-cylinder gas was sampled during from intake valve close to before ignition start. The lower exhaust cam made shorter valve event than higher exhaust cam and made IEGR increase because of trapping the exhaust gas. IEGR rate was more affected by exhaust valve timing than intake valve timing and increased as exhaust valve timing advanced. In-cylinder pressure was increased near top dead center due to early close of exhaust valve. Ignition timing was more affected by intake valve timing than exhaust valve timing in case of exhaust valve lift 8.4 mm, while ignition timing was affected by both intake and exhaust valve timing in case of exhaust valve 2.5 mm. Burn duration with exhaust valve lift 2.5 mm was longer than other case due to higher IEGR rate. The fuel conversion efficiency with higher exhaust valve lift was higher than that with lower exhaust valve lift. The late exhaust and intake maximum open point (MOP) made the fuel conversion efficiency improve.

• 시스템엔지니어링학술지
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• 제10권2호
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• pp.59-69
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• 2014

In the bidding stage of turn-key based plant construction contracts, owners provide design and performance basis for contractors instead of giving design drawing. To win the bid for a plant construction, the contractors should be obliged to satisfy and ensure owners'requirements such as design and performance basis in a plant construction project, In other words, owners imposes technical risk of the design to the contractors by specifying responsibility for the analysis and verification of the plant construction. Thus, it is very important that contracters make accurate and realistic basic design plan in a short period of time. To deal with such a situation, we propose a systems engineering approach for the analysis and management of the technical risk. Specifically, we first: 1) Analyzes technical risk related with the plant design information for the bidders, followed by 2) Developing stakeholder requirements for the basic engineering design, and 3) System requirements for dealing with technical risk. Also, in this paper, we proposed converting method from MOE(Measure of Effectiveness) to MOP(Measure of Performance) in the risk analysis. To show the effectiveness of the proposed method, we carried out a case study.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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• pp.246-255
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• 2017

The proposed design methodology represents a new approach to optimize the propeller-hull system simultaneously. In this paper, two objective functions are considered, the first objective function is Lifetime Fuel Consumption (LFC) and the other one is cost function including thrust, torque, open water and skew efficiencies. The variables of the propeller geometries (Z, EAR, P/D and D) and ship hull parameters (L/B, B/T, T and $C_B$) are considered to be optimized with cavitation, blades stress of propeller. The well-known evolutionary algorithm based on NSGA-II is employed to optimize a multi-objective problem, where the main propeller and hull dimensions are considered as design variables. The results are presented for a series 60 ship with B-series propeller. The results showed that the proposed method is an appropriate and effective approach for simultaneously propeller-hull system design and is able to minimize both of the objective functions significantly.

• 약학회지
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• 제60권2호
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• pp.53-57
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• 2016

This study was performed to examine the skin phototoxicity of purified bee venom (Apis mellifera L.) collected using bee venom collector. To confirm whether the gel containing purified bee venom (BV gel) causes photototoxicity when used for the skin medicinal products, phototoxicity testing was conducted using guinea pig models. The BV gel (0.1 ml/site) was administered transdermally to guinea pigs. 8-MOP was used to introduce positive control response. After administration, the guinea pigs were irradiated with UVA ($15J/cm^2$) with doses based on standard phototoxicity study guidelines. In the weight measurement and clinical observation, BV gel groups didn't show any significant changes compared with control group. BV gel groups did not show any symptoms such as erythema and edema formation of skin. This study demonstrated that BV gel has promising potential external treatment for topical uses that do not induce significant levels of skin phototoxicity.

• Safety and Health at Work
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• 제11권1호
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• pp.80-87
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• 2020

Background: Residential and commercial cleaning is a part of our daily routine to maintain sanitation around the environment. Health care of professionals involved in such cleaning activities has become a major concern all over the world. The present study investigates the risk of musculoskeletal disorders in professional cleaners involved in floor mopping tasks. Methods: A cross-sectional study was performed on 132 mopping professionals using a modified Nordic questionnaire. The Pearson correlation test was implemented to study the association of perceived pain with work experience. The muscle strain and postural risk were evaluated by means of three-channel electromyography and real-time motion capture respectively of 15 professionals during floor mopping. Results: Regarding musculoskeletal injuries, risk was reported majorly in the right hand, lower back, left wrist, right shoulder, left biceps, and right wrist of the workers. Work experience had a low negative association with MSDs in the left wrist, right wrist, right elbow, lower back, and right lower arm (p < 0.01). Surface EMG showed occurrence of higher muscle activity in upper trapezius and biceps brachii (BB) muscles of the dominant hand and flexor carpi radialis and BB muscles of the nondominant hand positioned at the upper and lower portion of the mop rod, respectively. Conclusion: Ergonomic mediations should be executed to lessen the observed risk of musculoskeletal injuries in this professional group of workers.

• 한국군사과학기술학회지
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• 제16권1호
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• pp.5-26
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• 2013

Since the optimized use of sonar systems for target tracking is a practical problem for naval operations, the measure of mission achievability is needed for preparing efficient sonar-maneuver tactic. In order to quantify the mission achievability or Measure Of Effectiveness(MOE) for given sonar-maneuver tactics, we developed and tested a simulation algorithm. The proposed algorithm for tracking is based on Measure Of Performance(MOP) for localization and tracking system of sonar against target. Probability of Detection(PD) using steering beam patterns referenced to the aspect angle of sonar is presented to consider the tracking-performance of sonar. Also, the integrated software package, named as Optimal Acoustic Search Path Planning(OASPP) is used for generating sonar-maneuver patterns and vulnerability analysis for a given scenario. Through simulation of a simple case for which the intuitive solution is known, the proposed algorithm is verified.

• Advances in environmental research
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• 제4권1호
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• pp.49-68
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• 2015

Chemically activated and carbonized adsorbents were prepared from Moringa oleifera pod husks (MOP), characterized and evaluated for their ability to remove a common antibiotic - ofloxacin (OFX) from aqueous solution. The pulverized precursor was steeped in a saturated ammonium chloride solution for a day to give the chemically activated adsorbent (AMOP). A portion of AMOP was pyrolyzed in a muffle furnace at 623 K for 30 min to furnish its carbonized analogue (CMOP). The adsorbents showed favorable physicochemical attributes. The effects of operational parameters such as initial OFX solution pH and concentration, adsorbent dosage, temperature and contact time on OFX removal were investigated. At equilibrium, optimal removal efficiencies of 90.98% and 99.84% were achieved at solution pH 5 for AMOP and CMOP, respectively. The equilibrium adsorption data fitted into both the Langmuir and Freundlich isotherms. Gibbs free energy change (${\Delta}G^o$), enthalpy change (${\Delta}H^o$) and entropy change (${\Delta}S^o$) indicated that the adsorption of OFX was feasible, spontaneous, exothermic and occurred via the physisorption mode. Adsorption kinetics obeyed the Blanchard pseudo-second-order model. The results may find applications in the adsorptive removal of micro-contaminants of pharmaceutical origin from wastewater.

• The Journal of Asian Finance, Economics and Business
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• 제6권1호
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• pp.91-105
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• 2019

The paper aims to combine balance sheet analysis at the firm level with the International Monetary Fund's public debt sustainability assessment framework to assess state-owned enterprises' (SOE) leverage as a contingent liability to the public sector. Based on company data and the interest coverage ratio as a measure of debt at risk, aggregate baseline scenarios are projected to gauge the magnitude of SOE debt as a contingency. SOE's financial and debt ratios are first bootstrapped to generate firm-level distributions and then averaged into a fan chart of the economy-wide SOE contingent liability. Applied to the People's Republic of China as an example, the study finds that by the end of 2015 SOE leverage had grown to a substantial liability. However arbitrary the assumptions underlying these projections, it would appear that even if authorities had to mop up as much as 20% of SOE debt at risk gone bad, this would have been manageable at roughly 2.7% of the gross domestic product in 2016 or 5.5% by 2021. This projection framework is fully amenable to alternative assumptions and settings, which makes it a useful analytical tool to monitor contingent liabilities from non-financial corporate debt that have been building in emerging and advanced economies alike.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.228-228
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• 2012

인공관절은 노인성 질환이나 자가 면역질환, 신체적인 외상 등으로 인하여 발생하는 관절의 손상 부위를 대체하기 위하여 고안된 관절의 인공 대용물이다. 인공 관절 중 인공 고관절의 경우 관절 운동을 하는 라이너(Liner)와 헤드(Head) 부분이 마모에 관여하여 인공관절의 수명에 영향을 미치게 되는데, 헤드 소재로서는 Co-Cr-Mo 합금이, 라이너 소재로서는 고분자 소재인 UHMWPE (Ultra High Molecular Weight Polyethylene)가 주로 사용되고 있다. 이러한 MOP (Metal-On-Polymer) 구조의 인공관절의 경우, 충격흡수의 장점이 있는 반면, 관절 운동시 발생하는 UHMWPE의 wear debris에 의한 골용해로 인하여 관절이 느슨해지는 문제점이 발생하여 재시술을 필요로 하게 된다. 또한 메탈 헤드의 마모로 인한 금속이온의 용출은 세포 독성의 문제를 야기하여 인공관절의 수명을 낮추는 또 하나의 요인이 되고 있다. 이러한 문제점들을 해결 하기 위하여, 본 연구에서는 PIII&D (Plasma Immersion Ion Implantation & Deposition)공정을 이용하여 Co-Cr-Mo 합금 소재 위에 niobium nitride (NbN) 박막을 증착하여 상대재인 UHMWPE의 마모를 줄이고자 하는 연구를 진행하였다. 마모량의 감소를 위하여, 박막을 증착하기 전에 Co-Cr-Mo 합금 위에 질소를 이온주입 하는 pre-ion implantation 공정을 도입하였으며, Co-Cr-Mo 합금과 NbN박막 사이의 접착력을 증가시키기 위하여 박막의 증착 초기에 이온주입과 증착을 동시에 수행하는 dynamic ion mixing공정을 수행하였다. 실험 결과 pre-ion implantation 공정을 도입한 경우 현재 상용화 되어있는 Co-Cr-Mo 합금에 비하여 마모량을 2배 이상 감소시키는 것을 확인 할 수 있었으며, dynamic ion mixing 공정을 도입한 경우 장시간의 마모 시험에서도 UHMWPE의 마모량을 2배 가까이 줄일 수 있었다.