• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.2
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• pp.77-83
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• 2012

Numerical analyses through Computational Fluid Dynamics have been performed to investigate the seawater flow field characteristics for various shrouds used in horizontal axis tidal current turbine systems. Seawater flow characteristics are largely influenced under constant tidal current velocity by the shroud geometry and there is considerable difference in fluid velocity distributions around the shrouds. Especially the location and magnitude of maximum seawater flow velocity directly affect turbine performance for power generation. For the cylinder-diffuser type shroud system whose cylinder and diffuser parts have the same length accelerated flow region is formed in the overall cylinder part while maximum velocity in the nozzle-diffuser type whose nozzle and diffuser parts have the same length with symmetry, locally appears near the minimum sectional area. In case of cylinder-diffuser type shroud fluid velocity increases rather high compared with current velocity. And fluid velocity at the centerline gradually increases from the entrance, and then decreases rapidly after reaching a peak close to the middle of the cylinder part unlike the nozzle-diffuser while there is not much variation near the rear of the shroud. These results of the seawater flow characteristics with various shroud geometries can be applied to optimal design for the development of efficient tidal current power generation systems.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.263-271
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• 2016

This study investigated the hydraulic impact scope and dissolved oxygen (DO) concentration distribution by the micro-bubble aeration in the Juksan Lake located in Asan city in Chungcheongnam-do province. A tracing experiment for hydraulic impact scope was used which constituted a 20% rhodamine solution. A 160 m-guideline was installed in the horizontal direction of the micro-bubble jet flow and the rhodamine concentration, water temperature, and DO concentration were measured at depths of 1 m, 2 m, and 3 m at intervals of 10 m. In the Juksan Lake, the effective range of jet flow discharged by the micro-bubble generator was about 40 m, and after then the jet plume moved up to 80 m to 120 m through the advection and diffusion processes of ambient water. DO concentration in the lake was maintained at 7.4-12.6 mg/L during tracking experiment. The DO of the lake sediments improved from 0.2 mg/L to 8.0 mg/L after applying micro-bubble aeration. In conclusion, the micro-bubble aeration can be an effective technology for the management and improvement of water quality in an agricultural reservoir.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.67-75
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• 2009

The purpose of this study is to analyze the effects of target position on the bowling motion. Four female high school athletes with more than four years of bowling experiences were recruited to this study. The major results of this study are as follows; When a subject treats the 1st pin, The spin angle of a coxa for the target position is largely kept from the downswing to the backswing peak point. When a subject treats the 7th pin, As the 7th pin exists at the left side for the right shoulder axis of the thrower, the movement of the ball center of the thrower from side to side is the lowest. In addition, the time required and horizontal speed appear the highest in the release section. The slant angle of a shoulder is largely increased as she moves from the backswing peak point to the release section. The twist angle of a shoulder also appears small as a throw motion is made toward the left side. When a subject treats the 10th pin, The spin angle of a shoulder and the twist angle of a body in motion appear the largest in the release section. So, there are the effects of target position on the bowling motion.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.156-164
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• 2018

In order to investigate the upwelling and island effects following the wind storm events in the East Sea (i.e., Uljin-Ulleungdo-Dokdo line) during spring, we assessed the vertical and horizontal profiles of abiotic and biotic factors, including phytoplankton communities. The assessment was based on the Geostationary Ocean Color Imager (GOCI) and field survey data. A strong south wind occurred on May 3, when the lowest sea level pressure (987.3 hPa) in 2016 was observed. Interestingly, after this event, huge blooms of phytoplankton were observed on May 12 along the East Korean Warm Current (EKWC), including the in the offshore waters of Ulleungdo and Dokdo. Although the diatoms dominated the EKWC area between the Uljin coastal waters and Ulleungdo, the population density of raphidophytes Heterosigma akashiwo was high in the offshore waters of Ulleungdo-Dokdo. Based on the vertical profiles of Chlorophyll-a (Chl. a), the sub-surface Chl. a maximum appeared at 20 m depths between Uljin and Ulluengdo, whereas relatively high Chl. a was distributed equally across the entire water column around the waters of Ulleungdo and Dokdo islands. This implies that the water mixing (i.e., upwelling) at the two islands, that occurred after the strong wind event, may have brought the rapid proliferation of autotrophic algae, with nutrient input, to the euphotic layer. Therefore, we have demonstrated that a strong south wind caused the upwelling event around the south-eastern Korean peninsula, which is one of the most important role in occurring the spring phytoplankton blooms along the EKWC. In addition, the phytoplankton blooms may have potentially influenced the oligotrophic waters with discrete time lags in the vicinity of Ulleungdo and Dokdo. This indicates that the phytoplankton community structure in the offshore waters of Ulleungdo-Dokdo is dependent upon the complicated water masses moving related to meandering of the EKWC.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.1
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• pp.51-57
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• 2012

The anterior maxillary incisor is the most traumatized region in the mouth and trauma is frequent between the ages of 8-10. Traumatic loss of teeth, can lead to many complications in children. Thus, as possible to keep traumatic teeth, but if you need extractions There may be. Complications occur and early tooth loss is frequent. Complications of early loss of central incisors are esthetic compromise, loss of vertical and horizontal width, height, contour of alveolar bone, tilting of adjacent teeth, arch length loss. Alveolar bone loss may affect normal function and stability, and results in esthetic problem for future prosthesis restoration. The 9-year-old girl and 6-year-old boy got early loss of upper central incisor. The amount of alveolar bone resorption was measured using cone beam computed tomograph and cast analysis.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.81-84
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• 2005

The origin for the charge disproportionation (CD) transition in polycrystalline $La_{1/3}Sr_{2/3}FeO_{2.96}$ was examined using X-ray diffraction and the external field $M\ddot{o}ssbauer$ssbauer spectroscopy. In order to see how the external magnetic field affects the CD state above its transition temperature, an external magnetic field of up to 6 T was applied either parallel or perpendicular to the $\gamma-ray$ direction with the sample temperature fixed at 225 K, which was above the CD transition temperature. Without an external magnetic field, a completely paramagnetic singlet was obtained in the temperature range of the averaged valence state above the transition temperature, which was interpreted as coming from the average valence $Fe^{3.6+}$. In the longitudinal geometry, a magnetic Zeeman with its intensity ratio 3:0:1:1:0:3 is superimposed to the central singlet. In the transverse geometry, however, the central singlet disappears and only a magnetic component with its intensity ratio 3:4:1:1:4:3 emerges. The existence of a singlet is understood as an evidence of the fast electron-transfer among Fe ions. Since the singlet still exists under the magnetic field, the application of an external field has little effect on the conduction mechanism of hopping electrons.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.176-183
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• 2008

Recently, several large-scale Mega-Projects are being conducted. For these urban revitalization projects which requires many complex functions, the existing project management system based on single project level is limited in application. Therefore, our main objectives of this research are two 1) Develop a brand-new program management system(Prototype Ver 1.0) for mega-projects where various facilities are combined both horizontally and vertically. 2) Develop management strategies(Prototype Ver 1.0) based on the program level that enable the comprehensive management of a multiple various projects. The subtitles of this Research are i-PMIS(Program Management Information System) Development, Standardization & Optimization of Construction Life-Cycle Process, Comprehensive Project Cost & Process Management Technology, Effective and Optimized Integrated Performance Management Technology, and, we suggest to optimize the whole life cycle process, predict and respond to various risks, predict and control the process, the cost and the schedule, achieve maximum return on investment to the participating parties, and provide a brand-new Program-MIS including the visual-based web-portal platform to respond the changing business environments and decision making.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.4
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• pp.141-149
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• 2010

Three-dimensional geo-spatial information is important for the efficient use and management of the country and the three-dimensional expression and analysis of urban projects, such as urban plans devised by local governments and urban management. Thanks to the revitalization of the geo-spatial information service industry, it is now being variously used not only in public but also private areas. For the creation of high-guiltily three-dimensional geo-spatial information, emphasis should be placed on not only the quality of the source image and three-dimensional geo-spatial model but also the level of visualization, such as level of detail and texturing. However, in the case of existing three-dimensional geo-spatial information, its establishment process is complicated and its data are not updated frequently enough, as it uses ready-created digital maps. In addition, as it uses Ortho Images, the images exist Relief displacement. As a result, the visibility is low and the three-dimensional models of artificial features are simplified to reach LoD between 2 and 3, making the images look less realistic. Therefore, this paper, analyzed the quality of three-dimensional geo-spatial information created using the three-dimensional modeling technique were applied using Digital photogrammetry technique, using digital aerial photo images by an existing large-format digital camera and multi-looking camera. The analysis of the accuracy of visualization information of three-dimensional models showed that the source image alone, without other visualization information, secured the accuracy of 84% or more and that the establishment of three-dimensional spatial information carried out simultaneously with filming made it easier to gain the latest data. The analysis of the location accuracy of true Ortho images used in the work process showed that the location accuracy was better than the allowable horizontal position accuracy of 1:1,000 digital maps.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.521-528
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• 2017

In this study, vertical loading tests were conducted to investigate the nonlinear behaviors of the fastening systems that have generally been used in the concrete track of domestic railway lines. Nonlinear load-displacement curve models were derived based on the test results. The uplift forces generated in the fastening systems were evaluated by applying the derived nonlinear models as well as the existing linear models. The influence of the factors on the maximum uplift force of the fastening system was analyzed through a parameter study on the distance between neighboring sleepers, the horizontal distance between the center of the bearing and the nearest fastening system from the deck end, and the height of the bridge girder. From the evaluation results it is known that, for economical track and bridge design, due to deck end deformation, it is necessary to consider the nonlinear behavior of the fastening system in the calculation of the uplift force of the fastening systems.

• Journal of Korean Society of Forest Science
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• v.94 no.6
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• pp.468-475
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• 2005

To understand spatiotemporal changes of temperature and humidity in Lentimula edodes cultivation sheds, temperature, relative humidity were measured with HOBO H8 series sensors in log cultivation sheds and sawdust cultivation sheds. The results obtained from October in 2003 to October in 2004 were as follows; 1. Horizontal temperature changes were smaller at center of cultivation shed inside than comer of cultivation shed inside, while relative humidity changes were greater about 3% at center of cultivation shed inside than corner of cultivation shed inside. 2. Vertical temperature changes showed that the temperature was higher at above than at below when the temperature rises, while the temperature was lower at above than at below when the temperature falls. Thus close to soil surface temperature showed a little fluctuation. Vertical relative humidity changes showed that the relative humidity was lower at above than at below when the temperature rises, while the relative humidity was higher at above than at below when the temperature falls. After all temperature and relative humidity was the opposite in cultivation shed. 3. It's showed in log cultivation shed that the minimum temperature was a subzero temperature until the end of April, while the minimum temperature did above zero after the beginning of the May. Besides a winter was the greatest at daily temperature range during the four season, about $30^{\circ}C$. On the other hand the minimum relative humidity was less than 20% at April, May and June but more than 40% after May.