• Ocean Systems Engineering
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• v.2 no.2
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• pp.115-135
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• 2012

The very low natural frequencies of tension leg platforms (TLP's) have raised the concern about the significance of the action of hydrodynamic wave forces on the response of such platforms. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that coupling between various degrees of freedom has insignificant effect on the displacement responses. Moreover, for short wave periods (i.e., less than 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on the wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about its original position. Also, for short wave periods, a higher mode contribution to the pitch response accompanied by period doubling appeared to take place. For long wave periods, (12.5 and 15 sec.), this higher mode contribution vanished after very few cycles.

• Ocean Systems Engineering
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• v.4 no.4
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• pp.327-342
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• 2014

The tension leg platform (TLP) is one of the compliant structures which are generally used for deep water oil exploration. With respect to the horizontal degrees of freedom, it behaves like a floating structure moored by vertical tethers which are pretension due to the excess buoyancy of the platform, whereas with respect to the vertical degrees of freedom, it is stiff and resembles a fixed structure and is not allowed to float freely. In the current study, a numerical study for square TLP using modified Morison equation was carried out in the time domain with water particle kinematics using Airy's linear wave theory to investigate the effect of changing the tether tension force on the stiffness matrix of TLP's, the dynamic behavior of TLP's; and on the fatigue stresses in the cables. The effect was investigated for different parameters of the hydrodynamic forces such as wave periods, and wave heights. The numerical study takes into consideration the effect of coupling between various degrees of freedom. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables. Nonlinear equation was solved using Newmark's beta integration method. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e., 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether tension force, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations that is significantly dependent on wave height, and that special attention should be given to tethers fatigue because of their high tensile static and dynamic stress.

• Korean Journal of Environment and Ecology
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• v.28 no.1
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• pp.71-79
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• 2014

The goal of this study is to estimate economic benefit of restoring ecological stream of Hong Cheon river. The benefit is determined by estimating willingness-to-pay for the value of Hong Cheon river because it is a non-market good which is difficult to be measured in terms of monetary value. Specifically, the spike model, one of the contingent valuation methods, is used to distinguish respondents having zero willingness-to-pay for Hong Cheon river. The results show that a household located near the Hong Cheon river is willing to pay 3,300~4,628 Korean Won per year, while a household not located near the Hong Cheon river is willing to pay 1,308~2,929 Korean Won per year. Thus, total benefit of restoring ecological stream of Hong Cheon river is estimated as 97.6~216.3 billion Korean Won.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.68-75
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• 2017

This paper presents the experimental and theoretical results of the dynamic responses of a pendular energy extractor in a two-dimensional wave channel. By adopting a wave maker with varying wave height and period, the dynamic responses of the pendular buoy were experimentally obtained. Furthermore, with the aid of the co-simulation of moving particle analysis and rigid dynamic analysis, the dynamic responses of the pendular system were evaluated. In order to validate the feasibility of the proposed wave power generator, the force tuning of the pendular system with restoring energy was carried out. The results provide proof of concept data for the development and design of a commercial model for horizontal wave power generators in the shoreline area.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.1
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• pp.79-89
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• 2005

Forest soils were analyzed on their biological and physicochemical properties for the ecological restoration of burnt forest soil using organic wastes and proper microorganisms. Three kinds of soil samples were collected from undamaged soil(US), naturally restoring soil(NS) and artificially restoring soil(AS). All soil samples were sandy soil and acidic soil, ranged pH 5.34~5.78. Moisture content was higher in the soil of NS region. And the others were similar. Total organic matter and soluble sugar were higher at the surface, generally. Heterotrophic soil microbes were abundant at the surface soil of NS and subsoil of AS. Dehydrogenase, cellulase and phosphatase activities were higher at the NS soil. Especially, Dehydrogenase activity as primary index of soil microbial process showed high correlationship with moisture content(r=0.90, P < 0.05).

• Journal of Broadcast Engineering
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• v.23 no.4
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• pp.503-510
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• 2018

Restoring of damaged images is a fundamental problem that was attempted before digital image processing technology appeared. Various algorithms for reconstructing damaged images have been introduced. However, the results show inferior restoration results compared with manual restoration. Recent developments of DNN (Deep Neural Network) have introduced various studies that apply it to image restoration. However, if the wide area is damaged, it can not be solved by a general interpolation method. In this case, it is necessary to reconstruct the damaged area through contextual information of surrounding images. In this paper, we propose an image restoration network using a generative adversarial network (GAN). The proposed system consists of image generation network and discriminator network. The proposed network is verified through experiments that it is possible to recover not only the natural image but also the texture of the original image through the inference of the damaged area in restoring various types of images.

• Journal of Internet Computing and Services
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• v.4 no.2
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• pp.1-9
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• 2003

Path restoration, which is needed to increase network survivability in MPLS networks, is a technology of supplying reliable service by delivering the traffics through restoring the paths when links or nodes of a working path are failed. In this paper, we propose a path restoration method using duplication of working paths for link failure as a method of restoring paths for the high priority traffics. The existing path restoration method transmits the traffics to the path restoration uniformly in regardless of the priority while link obstacle. It has a problem to take a long time to restore the connection of the high priority traffics. On the other hand, the suggested restoration method establishes the duplication path for the working path, which transmits the high priority traffics and transmit the traffics through the duplication path. It has a strong point to restore the connection quickly. Also, through simulation we analyze the performance of the restoration system using the duplication path and prove that the proposed restoration method is superior in performance to the existing restoration methods regarding to the high priority traffics.

• Journal of The Korean Astronomical Society
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• v.46 no.5
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• pp.191-200
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• 2013

Full-disk solar images are provided by many solar telescopes around the world. However, the observed images show Non-Radial Variation (NRV) over the disk. In this paper, we propose algorithms for detecting distortions and restoring these images. For detecting NRV, the cross-correlation coefficients matrix of radial profiles is calculated and the minimum value in the matrix is defined as the Index of Non-radial Variation (INV). This index has been utilized to evaluate the H images of GONG, and systemic variations of different instruments are obtained. For obtaining the NRV's image, a Multi-level Morphological Filter (MMF) is designed to eliminate structures produced by solar activities over the solar surface. Comparing with the median filter, the proposed filter is a better choice. The experimental results show that the effect of our automatic detection and restoration methods is significant for getting a flat and high contrast full-disk image. For investigating the effect of our method on solar features, structural similarity (SSIM) index is utilized. The high SSIM indices (close to 1) of solar features show that the details of the structures remain after NRV restoring.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.1
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• pp.1-10
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• 2011

The purpose of this study is to derive the actually applicable directions and measures for conservation and restoration according to biotope types. Recently biotope project-installing eco-river, restoring damaged area, protecting habitate for flora and fauna- is processed according to being interested in making and restoring the biotope. But it is lack of study to estimate and systematize which biotope preserve and restore primary. For this purpose, the direction and measures of conservation and restoration be applicable to actuality are drafted by a review on the preceded case studies until now at the inside and outside of the country. And then this study proposed the concept, direction and measures for the effective systematic biotope management through continual feed back such as field applications in selected case study areas and consultations. First, the applicable directions and measures for conservation and restoration according to biotope types is suggested with the 'conservation' divided into two parts; protection and maintenance, the 'restoration', and the 'enhancement' divided into two parts; improvement and creation. Second, for the effective biotope management, the biotope types are classified into urban type, agricultural types and natural types according to the naturalness and dominant landscape. However, this study suggests that the direction and measures suitable to the regional conditions should be reviewed enough and selected and also the detail measures should be supplemented with the foundation of directions and measures for biotope conservation and management proposed in this study because the biotope management should consider regional characteristics.

• Archives of Plastic Surgery
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• v.41 no.6
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• pp.686-692
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• 2014

Background Restoring orbital volume in large blowout fractures is still a technically challenge to the orbital surgeon. In this study, we restored the orbital wall using the combination of transorbital and transnasal approach with additional supports from the paranasal sinuses, and we compared the surgical outcome to that of a conventional transorbital method. Methods A retrospective review of all patients with pure unilateral blowout fractures between March 2007 and March 2013 was conducted. 150 patients were classified into two groups according to the surgical method: conventional transorbital method (group A, 75 patients, control group), and the combination of transorbital and transnasal approach with additional supports from the paranasal sinuses (group B, 75 patients, experimental group). Each group was subdivided depending on fracture location: group I (inferior wall), group IM (inferomedial wall), and group M (medial wall). The surgical results were assessed by the Hertel scale and a comparison of preoperative and postoperative orbital volume ratio (OVR) values. Results In the volumetric analysis, the OVR decreased more by the experimental groups than each corresponding control groups (P<0.05). Upon ophthalmic examination, neither the differences among the groups in the perioperative Hertel scale nor the preoperative and postoperative Hertel scales were statistically significant (P>0.05). Conclusions Our surgical results suggest that orbital volume was more effectively restored by the combination of transorbital and transnasal approach with additional supports from the paranasal sinuses than the conventional method, regardless of the type of fracture.