Geoje, South Korea
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Kim T.-G.,Seoul National University | Hong S.-Y.,Seoul National University | Song J.-H.,Korea University | Kwon H.-W.,Koje College
Noise Control Engineering Journal | Year: 2016

Noise from heating, ventilating and air conditioning (HVAC) systems is normally predicted by the empirical method suggested by the National Environmental Balancing Bureau (NEBB). However, the method suggested by the NEBB for ducts used in architecture is not suitable for large size ducts usually used in ships and offshore plants. In this paper, to predict noise from an offshore plant HVAC system, empirical formulas for attenuation of sound pressure level in large ducts are derived using the boundary element method (BEM). Further, regeneration noise caused by air flow in ducts with stiffeners inside is analyzed using computational fluid dynamics (CFD). Break-out noise is also analyzed by BEM and finite element method (FEM). Utilizing the results of this study, an integrated HVAC noise analysis program has been developed and the results obtained from the program were compared with measured data. The efficiency and validity of the formulas are shown. © 2016 Institute of Noise Control Engineering.

Kwon H.-W.,Koje College | Hong S.-Y.,Seoul National University | Song J.-H.,Chonnam National University
Advances in Engineering Software | Year: 2015

For the analysis of noise problems in medium-to-high frequency ranges, the energy flow boundary element method (EFBEM) has been studied. EFBEM is numerical analysis method of energy flow analysis (EFA), and solves energy governing equations using a boundary element method in complex structures. Based on EFBEM, a noise prediction software, "noise analysis system by energy flow analysis" (NASEFA), was developed. For effective maintenance, NASEFA is composed of three main modules: the translator, the model converter, and the main solver. The translator changes the FE model to the NASEFA BE model, and the model converter changes the BE model to an EFBE model, including various data, such as structural materials, medium properties, sources, and boundary conditions. NASEFA then solves the acoustic energy density and intensity on boundary and in the field. Moreover, it analyzes interior and exterior noise problems for single and multiple domains in two and three dimensions. Finally, for the validation of the software developed, interior and exterior noise predictions of various structures were performed. The results obtained with NASEFA were compared with those of the commercial SEA program and experiment. From these comparative studies, the usefulness of NASEFA was established. © 2015 Elsevier Ltd. All rights reserved.

Kwon H.-W.,Koje College | Hong S.-Y.,Seoul National University | Song J.-H.,Chonnam National University
Journal of Mechanical Science and Technology | Year: 2016

In this study, a method for energy flow analysis was developed to predict the vibrational responses of coupled cylindrical thin shell structures in the medium-to-high frequency ranges. To extend the application of the energy flow model for out-of-plane waves in the thin shell to coupled structures, the wave transmission analyses of general coupled cylindrical thin shell structures are performed. Power reflection and transmission coefficients on the coupled line were calculated using the coupling relationships established for coupled cylindrical thin shells. Using these coefficients, an energy flow analysis in which a junction was considered, was performed for coupled cylindrical thin shell structures. The junction consisted of an arbitrary number of cylindrical thin shells coupled along a junction line. Through numerical simulations, the energy flow solutions of coupled cylindrical thin shell structures were compared with those of classical displacement solutions, and they showed well-developed energy density global propagation and decay patterns. © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

PubMed | Koje College and Gyeongnam National University of Science and Technology
Type: Journal Article | Journal: International journal of nursing practice | Year: 2016

This study was designed to construct and test the structural equation modelling on nurses turnover intention including emotional labour, job stress, emotional intelligence and burnout in order to identify the mediating effect of emotional intelligence between those variables. Emotional labour, job stress and burnout increase turnover intention of nurses. However, emotional intelligence is negatively correlated with emotional labour and reduces job stress, burnout and turnover intention. Structural equation modelling was used to analyse the goodness of fit of the hypothetical model of nurses turnover intention. Research data were collected via questionnaires from 4 to 22 August 2014 and analysed using SPSS version 18.0 and AMOS version 20.0. The model fit indices for the hypothetical model were suitable for recommended. Emotional intelligence has decreasing effect on turnover intention through burnout, although its direct effect on turnover intention is not significant. Emotional intelligence has mediation effect between emotional labour and burnout. This studys results suggest that increasing emotional intelligence might critically decrease nurses turnover intention by reducing the effect of emotional labour on burnout.

Kwak D.-J.,Kyungsung University | Kim J.-H.,Kyungsung University | Park B.-W.,Kyungsung University | Sung Y.-M.,Kyungsung University | And 2 more authors.
Current Applied Physics | Year: 2010

Aluminium-doped zinc oxide (ZnO:Al) conducting layer was deposited on polyethylene terephthalate (PET) substrate by r.f. magnetron sputtering to investigate the possible application of the film as transparent conducting electrode for film-typed dye-sensitized solar cells (FT-DSCs). The structural and electrical properties of ZnO:Al thin film were influenced significantly by the position of PET substrate and by also gas pressure. The minimum resistivity of 2.1 × 10-3 Ω cm was obtained at gas pressure of 5 mTorr. The deposition rate of ZnO:Al film at 5 mTorr of gas pressure was 248 nm/min. The efficiency of prepared FT-DSCs sample with ZnO:Al electrode showed about 2.1% (FF: 0.54, Voc: 0.73 V, Jsc: 5.3 mA/cm2). © 2009 Elsevier B.V.

Hwang A.,Koje College | Yoon S.,Maritime R and nter Nex1 Co. | Hwang J.,Maritime R and nter Nex1 Co.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

This paper proposes the result of hardware in the loop simulation (HILS) for performance evaluation about a small attitude heading reference system (AHRS) based micro electro mechanical system (MEMS) suitable for small unmanned underwater vehicle. Unmanned underwater vehicles (UUV) have many applications in scientific, military, and commercial area due to its autonomy and the navigation system is most important system for unmanned underwater vehicle because the correct position information is essential for autonomous missions. Since GPS-signal is not accessible underwater, the inertial navigation system (INS) have usually been used as the navigation system for underwater vehicle. The MEMS AHRS will be good alternative for the inertial sensor for INS of small UUV. Hardware in loop simulation (HILS) was performed to validate the developed MEMS AHRS with flight motion simulator and the results of HILS showed that the developed MEMS AHRS is capable of providing the attitude information under roll free and no roll free condition. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).

Shin D.-C.,Koje College | Nam J.-H.,Dongyang University | Kim D.-W.,Korea Aerospace University
Experimental Techniques | Year: 2016

The elastomeric O-ring is used as a packing element in the diverse parts of industrial system, such as the high pressure vessel, the oil supply equipment, the aerospace component, and the nuclear power plant etc. The design criterion of O-ring was determined by analyzed results of stress and the deforming behavior at various loading conditions related with sealing pressure and fit condition. The shape of O-ring was changed according to the squeeze rate, the sealing pressure, and time. At last, the study of deforming behavior and distribution of internal stress distribution from the constant squeezing O-ring with various sealing pressures was carried out on the real-time observation. To realize the experimental progress, we developed a specific loading device for the hybrid transmission photoelasticity under the continuous applying of the sealing pressure for squeeze rate. The O-ring was infiltrated into the space gap between the low-sidewall and the front-sidewall while the test load was forcing out. The analysis using the photoelastic model experiment of interior stress field in the constant squeezing of O-ring seal evidently gave a solution to predict the characteristic fracture of elastomeric sealing material. © 2016, The Society for Experimental Mechanics, Inc.

Shin D.-C.,Koje College | Kim T.-G.,Pusan National University | Kim D.-W.,Daegu University
Experimental Mechanics | Year: 2015

The linear contribution of total energy release rate for fracture of ferroelectric materials was studied based on the linear theoretic framework of piezoelectricity using the double-torsion technique. It was found that three linear contributions of the total energy release rate for piezoelectric material are definitely associated with pure mechanical compliance, electromechanical compliance, and pure electrical capacitance. To confirm the entity of contributions, mechanical and electromechanical compliances were analyzed obtained from result of load vs. displacement measured on each electric field, and electrical capacitance was obtained from property and geometry of samples. © 2015 Society for Experimental Mechanics

Hwang A.,Koje College | Seong W.,Seoul National University | Lee P.-m.,Korea Ocean Research and Development Institute
International Journal of Offshore and Polar Engineering | Year: 2012

This paper proposes a simultaneous localization and mapping (SLAM) scheme applicable to the autonomous navigation of unmanned underwater vehicles (UUV). A SLAM scheme is an alternative navigation method for measuring the environment through which the vehicle is passing and providing the relative position of the unmanned vehicle. An unscented Kalman filter (UKF) is utilized in order to develop a SLAM that is suitable for estimating the locations of the UUV and the surrounding objects when the UUV's motion is highly nonlinear. A range sonar is used as a sensor for collecting the data of the spatial information of the environment in which the UUV navigates. The proposed UKF-SLAM scheme was tested in experiments that used various 3 degrees-of-freedom motion conditions with a real UUV under a tank environment. The results of these experiments showed that the proposed SLAM algorithm was capable of estimating the position of the UUV and the surrounding objects in real environments, and that the algorithm will perform well in various conditions. © The International Society of Offshore and Polar Engineers.

Hwang A.,Koje College | Seong W.,Seoul National University
Defence Science Journal | Year: 2012

Paper proposes a simultaneous localisation and mapping (SLAM) scheme which is applicable to small military unmanned underwater vehicles (UUVs). The SLAM is a process which enables concurrent estimation of the position of UUV and landmarks in the environment through which the vehicle is passing. An unscented Kalman flter (UKF) is utilised to develop a SLAM suitable to nonlinear motion of UUV. A range sonar is used as a sensor to collect the relative position information of the landmark in the environment in which the UUV is navigating. The proposed SLAM scheme was validated through towing tank experiments about two degrees of freedom motion with UUV motion simulator and real range sonar system for small UUV. The results of these experiments showed that proposed SLAM scheme is capable of estimating the position of the UUV and the surrounding objects under real underwater environment. © 2012, DESIDOC.

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