• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.552-568
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• 2020

After long-term service in deep ocean, pipelines are usually suffered from corrosions, which may greatly influence the Vortex-Induced Vibration (VIV) behavior of pipes. Thus, we investigate the VIV of defective pipelines. The geometric nonlinearity due to large deformation of pipes and nonlinearity in vortex-induced force are simulated. This nonlinear vibration system is simulated with finite element method and solved by direct integration method with incremental algorithm. Two kinds of defects, corrosion pits and volumetric flaws, and their effects of depth and range on VIV responses are investigated. A new finite element is developed to simulate corrosion pits. Defects are found to aggravate VIV displacement response only if environmental flow rate is less than resonance flow rate. As the defect depth grows, the stress responses increase, however, the increase of the defect range reduces the stress response at corroded part. The volumetric flaws affect VIV response stronger than the corrosion pits.

• Journal of Korean Academy of Nursing
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• v.45 no.3
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• pp.397-411
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• 2015

Purpose: The purpose of the study was to explore and describe the experience of Korean college students on suicide attempts. Methods: Eight students participated and data were collected through in-depth individual interviews between September, 2011 and April, 2012. Data were analyzed using Strauss and Corbin's grounded theory method. Results: Analysis showed that the central phenomenon of suicide attempt experience of college students was 'inextricable despair'. Causal conditions were 'sense of shame by failure to achieve perfect independence' and 'a big gap between reality and ideals'. Contextual conditions were 'extreme situation of being cornered' and 'excessive changes in emotions'. Intervening conditions were 'important others' and 'perspectives on the world'. Action/interaction strategies were 'temporary efforts' and 'gathering up one's mind'. Consequences were 'trauma as one's own hurt', 'conflict between life and death' and 'becoming mature'. Conclusion: The results of this study provide an in-depth understanding of the experience of college students with attempted suicide. It is necessary to develop programs to prevent suicide attempts by college students and these results can be used as a basis for program development.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.144-152
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• 2018

This study aims to establish a mathematical formula to provide rapid and safety estimation of the damaged double hull tankers under ship-ship collision. Difference in heights between the striking and struck ships 'h' and penetration depth 'x' were considered as the main parameters. In ship-ship interaction, Large oil tankers are selected as target struck vessels, and they are struck by Very Large Crude-Oil Carrier (VLCC) class oil tanker. The residual strength of damaged ship at several locations and collision scenarios were carried out using Intelligent Supersize Finite Element Method (ISFEM) which considers the progressive collapse behavior of ship hulls strength. Based on these results, satisfactory was achieved and empirical formula was successfully established using the regression analysis method by deploying the height difference 'h' and penetration depth 'x' as the observed parameters.

• Journal of Korean Academy of Nursing
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• v.46 no.6
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• pp.858-870
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• 2016

Purpose: The purpose of the study was to explore and describe the adaptation process of older people to group homes. Methods: Participants were twenty older adults aged 65 or older who were living in group homes. Data were collected from January to April, 2015. In-depth unstructured interviews were conducted with individual participants. Data were analyzed using Strauss and Corbin's grounded theory method. Results: From open coding, 100 concepts, 38 sub-categories, and 14 categories were identified. Analysis showed that the central phenomenon of the adaptation process of older people to group homes was 'gradually giving up'. Causal conditions were 'good-for-nothing body', contextual conditions were 'pushed', 'beleaguered'. Intervening conditions were 'reliable pillar: children', 'having affection (情) more than having it from family: facility workers', 'comfort - like feeling at home', 'relieved: system'. Action/interaction strategies were 'facing the unfamiliar reality', 'building relationships with other people', 'accepting reality'. Consequences were 'a good place, more than expected', 'hope for the remaining days', 'waiting for a peaceful death'. Conclusion: The results of this study provide an in-depth understanding of the experience of the adaptation process of older people to group homes. The findings from this study can be used as basic data to establish policies to increase the number of small scale facilities which can help older adults adapt easily to the facilities.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.106-113
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• 2010

The most suitable condition for plasma source ion implantation(PSII) was found based on the study of the characteristics of PSIIed tool and machined surfaces. The depth analysis according to the chemical bonding state of elements and surface component elements through the XPS and SIMS, was conducted to find the improved property of the PSIIed surface. Due to the diffusion of PSII, the nitrogen was found up to a depth of about 150nm according to the supplied voltage and ion implanted time. The deep diffusion by nitrogen caused the surface modification, but the formation of oxide component was found due to the residual gas contamination on the surface. Statistical method of ANOVA was conducted to find the effects of spindle speed and feed rate in interaction for machined surface roughness with PSIIed tools. The surface modification was found largely occurred by the nitrogen implanted surface with 2 hours for 27kV, 35kV and 43kV.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.485-488
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• 2006

Surface roughening which is occurred by interaction between base paper and water in coating color deteriorates surface properties of coated paper. In this study, the effect of calendering variables on surface roughening and the relationship between hot calendering and water penetration depth were investigated. BCTMP handsheets were calendered at the various conditions of temperature and linear load, and its PPS roughness was measured before and after moistening to evaluate surface roughening. To determine water penetration depth, thickness was measured from the cross sectional images of sheet which were obtained using CLSM technique. High pressure calendering was beneficial to reduce surface roughness before coating but its smoothening effect was mostly lost by contact with water. On the contrary, sheet calendered at the highest temperature showed the lowest roughening. High temperature calendering allowed the smallest penetration of water into fiber network because of sufficient deformation and densification in top side of z-direction of sheet. Consequently, hot calendering could be the effective way to reduce surface roughening and unevenness of paper surface.

• Structural Engineering and Mechanics
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• v.85 no.2
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• pp.247-263
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• 2023

The paper deals with the study of the mechanical time-harmonic forced vibration of the hydro-piezoelectric system consisting of the piezoelectric plate and compressible viscous fluid with finite depth. The exact equations of motion of the theory of linear electro-elasticity for piezoelectric materials are employed for describing the plate motion, however, the fluid flow is described by employing the linearized Navier-Stokes equations for a compressible (barotropic) viscous fluid. The plane-strain state in the plate and the plane flow of the fluid are considered and the corresponding mathematical problems are solved by employing the Fourier transform with respect to the space coordinate which is on the coordinate axis directed along the platelying direction. The expressions of the corresponding Fourier transform are determined analytically, however, the inverse transforms are found numerically. Numerical results on the interface pressure and the electrical potential are obtained for various PZT materials and these results are discussed. According to these results, in particular, it is established that the electromechanical coupling effect can significantly decrease the interface pressure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2585-2598
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• 2015

Hand posture recognition has played a very important role in Human Computer Interaction (HCI) and Computer Vision (CV) for many years. The challenge arises mainly due to self-occlusions caused by the limited view of the camera. In this paper, a robust hand posture recognition approach based on 3D point cloud from two RGB-D sensors (Kinect) is proposed to make maximum use of 3D information from depth map. Through noise reduction and registering two point sets obtained satisfactory from two views as we designed, a multi-viewed hand posture point cloud with most 3D information can be acquired. Moreover, we utilize the accurate reconstruction and classify each point cloud by directly matching the normalized point set with the templates of different classes from dataset, which can reduce the training time and calculation. Experimental results based on posture dataset captured by Kinect sensors (from digit 1 to 10) demonstrate the effectiveness of the proposed method.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.183-191
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• 2004

The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged droplets, both the fixed droplet distances of 5 radii to 40 radii horizontally and 4 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal or vertical droplet spacing substantially influence lifetime of interacting droplets. At a low Reynolds number, lifetime of the two droplets with decreasing horizontal droplet spacing increases monotonically, whereas their lifetime with decreasing vertical droplet spacing decreases due to flow acceleration. This flow acceleration effect is reversed when the vertical droplet spacing is smaller than 5 radii in which decreasing flame penetration depth causes the reduction of heat transfer from flame to droplets. At a high Reynolds number, however, lifetime of the first droplet is hardly affected by either the horizontal droplet spacing or flow acceleration effect. Lifetime with decreasing vertical droplet spacing increases due to reduction of flame penetration depth. Lifetime of interacting droplets exhibits a strong dependence on Reynolds number, the horizontal droplet spacing and the vertical droplet spacing and can be con-elated well with these conditions to that of single burning droplet.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.123-132
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• 1999

One of the major difficulties in the seismic analysis of a dam-reservoir system is the treatment of the energy radiation in the upstream direction of the reservoir. In the paper, a new transmitting boundary is presented that can model properly the radiation of energy in the far field direction of a semi-infinite reservoir with constant depth. In the newly developed method, effects of surface wave motion are taken into accounted and the reservoir-foundation interaction is approximately accounted for with an absorbing boundary condition. If a dam has vertical upstream face and the infinitely long reservoir maintains constant depth, then the proposed transmitting boundary can be directly coupled with the model of dam body. In present study, the dam body is assumed to behave elastically and modeled by finite element method. Seismic responses of a dam model are investigated using the newly developed transmitting boundary.