• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.2
• /
• pp.151-160
• /
• 2017

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.4
• /
• pp.57-66
• /
• 2015

Empirical seismic displacement equations based on the Newmark sliding block method are widely used to develop seismic landslide hazard map. Most proposed equations have been developed for embankments and landfills, and do not consider the dynamic response of sliding block. Therefore, they cannot be applied to Korean mountain slopes composed of thin, uniform soil-layer underlain by an inclined bedrock parallel to the slope. In this paper, a series of two-dimensional dynamic nonlinear finite difference analyses were performed to estimate the permanent seismic slope displacement. The seismic displacement of mountain slopes was calculated using the Newmark method and the equivalent acceleration time history. The calculated seismic displacements of the mountain slopes were compared to a widely used empirical displacement model. We show that the displacement prediction is significantly enhanced if the slope is modeled as a flexible sliding mass and the amplification characteristics are accounted for. Regression equation, which uses PGA, PGV, Arias intensity of the ground motion and the fundamental period of soil layer, is shown to provide a reliable estimate of the sliding displacement. Furthermore, the empirical equation is shown to reliably predict the hazard category.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.214-214
• /
• 2003

During a model test of Hutton TLP, a "ringing" response was first observed about 20 years ago. This phenomenon is a resonant build up over the time of wave period and this burst-like motion can cause the extreme load on the TLP tether. It is often detected in the large and steep irregular waves but the generation mechanism leading to the "ringing" is not yet well understood. According to the research since then, the higher order harmonic components may account for the "ringing" on the floating offshore structures. The main purpose of the present research is, thus, to measure the higher harmonic forces exerted on a vertical truncated circular column and to compare them with available data. A vertical truncated cylinder with a diameter of 3.5inch and a draft of 10.5inch is used as a test structure, which is a scaled model of ISSC TLP column. The cylinder is installed at a distance of 45ft from the wave maker in order to avoid parasitic waves created in the wave flap. Attached to the upper part of the cylinder are two force gages to measure the horizontal (surge) and vertical (heave) forces on the cylinder. The incoming waves are Stokes waves with a slope ranging from 0.06 to 0.24. The forces and waves are measured for 60 seconds with a sampling rate of 50 Hz. Among the recorded data, the first 10 waves are excluded because of transient behavior of the waves and the next The horizontal and vertical forces are analyzed up to 5th order harmonics. The horizontal forces are then compared to the values from the theoretical model called "FNV model". In addition, force transfer functions are also investigated. Major findings in this research are below. 1) The first order forces measured are slightly larger than the theoretical values of "FNV model" 2) The "FNV model" considerably overpredicts the second order forces. 3) The larger the amplitude and more extreme the wave slope, the smaller the predictions are compared to the experimental. 4) The higher harmonic forces are significantly smaller than the first harmonic force for all wave parameters. 5) The normalized forces vs. waves slopes are almost constant in the lower harmonics but vary a lot in the higher harmonics. 6) The trend of forces is more nonlinear in the horizontal forces than in the vertical forces as the wave slope increases. 7) The part of the results above is also observed by other researchers and confirmed again through the present work.

• Journal of the Korean Society of Safety
• /
• v.11 no.4
• /
• pp.143-150
• /
• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of KIISE
• /
• v.42 no.5
• /
• pp.609-620
• /
• 2015

Viewers of videos are likely to absorb more information from the part of the screen that attracts visual attention. This fact has led to the visual attention models that are being used in producing and evaluating videos. In this paper, we investigate the factors that are significant to visual attention and the mathematical form of the visual attention model. We then estimated the visual attention probability using the statistical design of experiments. The analysis of variance (ANOVA) verifies that the motion velocity, distance from the screen, and amount of defocus blur affect human visual attention significantly. Using the response surface modeling (RSM), we created a visual attention score model that concerns the three factors, from which we calculate the visual attention probabilities (VAPs) of image pixels. The VAPs are directly applied to existing gradient based 3D effect perception measurement. By giving weights according to our VAPs, our algorithm achieves more accurate measurement than the existing method. The performance of the proposed measurement is assessed by comparing them with subjective evaluation as well as with existing methods. The comparison verifies that the proposed measurement outperforms the existing ones.

• Journal of The Korean Ophthalmological Society
• /
• v.59 no.11
• /
• pp.1097-1102
• /
• 2018

Purpose: To report a case of toxic optic neuropathy caused by chlorfenapyr ingestion accompanied by central nervous system involvement. Case summary: A 44-year-old female visited our clinic complaining of reduced visual acuity in both eyes for 7 days. She had ingested a mouthful of chlorfenapyr for a suicide attempt 2 weeks prior to the visit. Gastric lavage was performed immediately after ingestion at the other hospital. Her best-corrected visual acuity was finger count 30 cm in the right eye and hand motion in the left eye. Both pupils were dilated by 5.0 mm and the response to light was sluggish in both eyes. A relative afferent pupillary defect was detected in her left eye. Funduscopy revealed optic disc swelling in both eyes. Magnetic resonance imaging of the brain showed a symmetric hyper-intense signal in the white matter tract including the internal capsule, corpus callosum, middle cerebellar peduncle, and brainstem. The patient was diagnosed with toxic optic neuropathy induced by chlorfenapyr ingestion, and underwent high-dose intravenous corticosteroid pulse therapy. Three days later, the best-corrected visual acuity was no light perception in both eyes. Three months later, optic atrophy was observed in both eyes. Optical coherence tomography revealed a reduction in the thicknesses of the retinal nerve fiber layer and ganglion cell and inner plexiform layer in the macular area. Conclusions: Ingestion of even a small amount of chlorfenapyr can cause severe optic nerve damage through the latent period, despite prompt lavage and high-dose steroid treatment.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.41 no.5
• /
• pp.513-522
• /
• 2021

A smartphone (SMP) includes a MEMS sensor that can record 3-components motions and has a wireless network device to transmit data in live. These features and relatively low maintenance costs are the advantage of using SMPs as an auxiliary seismic observation network. Currently, 279 SMPs are monitoring seismic motions. In this study, we compare the SMP records with the seismic station (SS) records to validate SMP records. The data used for comparison are records for five earthquakes that occurred in 2019, which are 321 SS data recorded by the Korea Meteorological Administration and the Korea Institute of Geoscience and Mineral Resources and 145 recorded by SMPs. The analysis shows that the event-term corrected average residual of the SMP MEMS sensor records is 0.59 which indicating that the peak horizontal acceleration by SMP is 1.8 factor bigger than the peak ground acceleration by SS. In addition, the residuals tend to decrease as the installation floor of the smartphone MEMS sensor increases, which is the similar trend with response spectra from SS.

• The Journal of the Korea Contents Association
• /
• v.19 no.5
• /
• pp.562-571
• /
• 2019

The expansion of the performing arts market to include new genres of art that combine art and cutting-edge media technology has surpassed the limitations of traditional theatre art elements such as stage, costumes, lighting, sound, and props, allowing free expression of space-time and visual art. It is growing into a wide area with unlimited potential in the performing arts sector. In response to these changes and the demands of the time, there is an increasing demand for multi-talents who can plan and produce arts and technology-converged contents that will contribute to the development of the performing arts industry. As a result, university departments related to theatre art across the country feel that it is urgent to develop curricula that will enhance students' competency by incorporating the latest media technologies such as virtual reality, holography, and interactive motion sensors into the existing performance art visualization process. In this study, the author will examine the process of developing courses in technology-incorporated theatre art (design) through case studies of media technology-converged performances from the past 10 years. Based on the traditional concept of theatre art, the attempt to fuse stage art with media technology will be a cornerstone of attempts to foster a group of talented artists who transcend the limits of creative visual expression and creative value.

• Korean Journal of Optics and Photonics
• /
• v.33 no.4
• /
• pp.146-158
• /
• 2022

The detector of a focal-plane-array mid-wave infrared (MWIR) camera has different response characteristics for each detector pixel, resulting in nonuniformity between detector pixels. In addition, image nonuniformity occurs due to heat generation inside the camera during operation. To solve this problem, in the process of camera manufacturing it is common to use a gain-and-offset table generated from a blackbody to correct the difference between detector pixels. One method of correcting nonuniformity due to internal heat generation during the operation of the camera generates a new offset value based on input frame images. This paper proposes a technique for dividing an input image into block image patches and generating offset values using only homogeneous patches, to correct the nonuniformity that occurs during camera operation. The proposed technique may not only generate a nonuniformity-correction offset that can prevent motion marks due to camera-gaze movement of the acquired image, but may also improve nonuniformity-correction performance with a small number of input images. Experimental results show that distortion such as flow marks does not occur, and good correction performance can be confirmed even with half the number of input images or fewer, compared to the traditional method.

• Korean Journal of Construction Engineering and Management
• /
• v.23 no.4
• /
• pp.3-14
• /
• 2022

Autonomous equipment requires a large amount of data from various environments. However, it takes a lot of time and cost for an experiment in a real construction sites, which are difficulties in data collection and processing. Therefore, this study aims to develop a virtual environment for autonomous tower cranes technology development and validation. The authors defined automation functions and operation conditions of tower cranes with three performance criteria: operational design domain, object and event detection and response, and minimum functional conditions. Afterward, this study developed a virtual environment for learning and validation for autonomous functions such as recognition, decision making, and control using the Unity game engine. Validation was conducted by construction industry experts with a fidelity which is the representative matrix for virtual environment assessment. Through the virtual environment platform developed in this study, it will be possible to reduce the cost and time for data collection and technology development. Also, it is also expected to contribute to autonomous driving for not only tower cranes but also other construction equipment.