• Journal of the Korean Society of Radiology
• /
• v.17 no.6
• /
• pp.843-849
• /
• 2023

This study attempted to determine the optimal algorithm after quantitatively analyzing noise, SNR, and CNR measurements by reconstructing four algorithms (Standard, Soft, Bone, and Detail) from head and neck CT images of patients who underwent implant surgery. As an analysis method, pixel values were calculated through the region of interest in the reconstructed image using the Image J program. For noise, SNR, and CNR, the region of interest was measured at the location of the pharynx, masseter muscle, and parotid gland in the image, and the mean and SD values were obtained. The values of SNR and CNR were calculated based on the given formula. As a result, the standard algorithm showed the lowest noise and the highest SNR. CNR was highest in the Soft algorithm, but showed no significant difference from the Standard algorithm. Therefore, it is believed that the Standard algorithm is the optimal algorithm for examining patients wearing intraoral implants in head and neck CT examinations. We hope that the data from this study will be used as basic data for image evaluation in head and neck CT examinations, and that the quality of images will be further improved through various algorithm changes. It is believed that this will be an opportunity to do so.

• Journal of Korea Port Economic Association
• /
• v.30 no.1
• /
• pp.175-194
• /
• 2014

Because the thawing of the Arctic ocean is slowly accelerating due to global warming, recently exploring resources in Arctic ocean and transporting resources by using the North Pole route have been getting spotlight. Since the original route transported by the Suez Canal from Korea to Europe could be shorten about 8,000km in distance(decreased about 38% compared to the original route), which means shortening about 10 voyage dates, it is expected to bring huge logistics cost reduction. Once the North Pole route is commercialized successfully, it would be one of the most important variables that affects future of Busan port and guides for economic development of Busan. Therefore, the purpose of this study is to analyze Busan port and the economic growth of Busan area by researching promising industry, based on the effect of freight transporting by the Northern sea route on the economy of Busan. For this study, questionnaire surveys and interviews were conducted for 64 people of experts in the shipping and port industry, relevant government, and academics. The survey finding shows that port logistics industry is a promising business in Busan in terms of its growth and competitiveness. It is necessary to develop feeder network facilities that prepare for commercialization of the Northern sea route as a short and medium term plan and provide professional manpower training in polar regions. Ship supply business would also play an important role. It is identified that revitalization of shipbuilding and ocean plant industry should be done in terms of Arctic business. With regard to the fishery industry it is found that modernization of fishery ship and development of fishery equipment used in polar areas should be carried out.

• Journal of Navigation and Port Research
• /
• v.35 no.3
• /
• pp.219-226
• /
• 2011

This study aimed to empirically identify the determinants of turnover intention of seafarers under the recognition that the number of seamen is decreasing. The results of regression analyses on questionnaire survey data are as follows. The more satisfied over wage and working condition, the lower the level of turnover intention of seafarers. The higher social identification and career vision, the lower the level of turnover intention of seafarers. In addition to this, older, married seamen were found to have lower turnover intention as compared to younger, unmarried ones. Lastly, four-year college graduates were, on the other hand, found to have higher turnover intention.

• Journal of Korean Society of Transportation
• /
• v.19 no.5
• /
• pp.99-108
• /
• 2001

A framework of using and integrating GIS and OR tools for determining the best site selection has been provided. In this research, we demonstrated that both the P-Median heuristic method and MIP method can be successfully applied to the optimum site selection problem of oil tank location selection. Furthermore, the results identified by both approaches are identical. To accomplish this, both GIS road and maritime networks have been constructed and combined to calculated the minimum distance matrix, which is required by both approaches. After the application to the Korean peninsula, the facility locations chosen are Kunsan, Yosu, Busan, and Okgye for each district. As has been shown, the power of GIS and both algorithm have been demonstrated throughout the research and further similar research can also be conducted using the power of GIS and Operations Research tools.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.5
• /
• pp.495-501
• /
• 2011

We present an experimental study of electrical discharge in nanoscale gaps. The discharge occurred between a cathode made of sharpened Pt-Ir wire and a gold-plated anode. Electric discharges were detected for electric potentials from 10 V to 80 V, and their gaps ranged from 50 nm to 800 nm. The spark signals indirectly showed spark phenomena such as discharges or shortages in the system. The sparks and discharges strongly depended on the electric potential (voltage) and the radius of the tips. For small gaps, the electrical discharge was random and strongly depended on the radius of the cathode tips.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.5
• /
• pp.496-504
• /
• 2012

In the field of environmental protection, close co-operation between Contracting Parties is strongly required and the reporting obligation under MARPOL 73/78 is playing an important role as a part of international co-operation for the environmental protection. In this paper, I review the meaning of reporting obligation under MARPOL 73/78 from the perspective of the international law, and investigate the status of implementation for the reporting obligation. For this purpose, I analyze status of implementation for last 10 years from 2001 to 2010 regarding reporting obligations under MARPOL 73/78 in accordance with MEPC/Circ.318. Finally, I suggest the way forward to improve Contracting Parties' compliance with reporting obligations through this analysis.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.32-38
• /
• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.11
• /
• pp.978-983
• /
• 2008

An application of innovative laser+GMA hybrid welding process is presented for reducing bead humping defects in high speed welding and increasing side wall fusion in narrow groove welding without torch or wire oscillation. In this hybrid process, the laser heat input is applied adjacent to the weld pool at a relatively low power density to produce a wider, flatter weld bead. In bead on plate in sheet metal gauges, the hybrid process was able to produce hump-free welds from 70ipm (${\sim}1780mm/min$) to over 150ipm (${\sim}3810mm/min$) of the travel speed compared to the un-assisted GMAW process. A square-butt joint in 15mm A572 Gr50 steel welds was investigated. A square butt joint with a gap of 3.2mm was filled with 6 passes. Liquid Nitrogen calorimetry and innovative $CO_2$ laser reflective optics were also developed to demonstrate the concept of hybrid welding.

• Journal of Korean Society of Transportation
• /
• v.14 no.2
• /
• pp.157-172
• /
• 1996

The long-existed licence system which has acted as one of the strong barriers to entry in the ocean shipping market in Korea is supposed to repeal in the near future. As a result, competition among the different sizes of firms which are operating under regional shield by means of the licence will be intensified. The main objective of this paper is to estimate the degree of economies of scale and economies of density for various firm sizes. For the successful estimation of economies scale and economies of density, translog cost models are developed and estimated through SURE technique which was suggested by Zeller (1963). The major findings are as follows ; All shipping firms in the sample exhibit economies of scale and density. Even small size shipping firms under licence system, they show substantial economies of scale contrary to the wide-known idea that small-size firms are subject to diseconomies of scale. For the ranked firm sizes according to owned deadweight tons, the degree of economies of scale decreases as the firm sizes are larger and larger. The degree of economies of density moderately declines from the smallest to the firm size of 30-60 thousand deadweight tons and sharply rise thereafter. And the large shipping firms with over half-million deadweight tons exhibit high economies density compared to other sizes of firm. If follows that the larger firms have great advantage in competition if the licence system is abolished.

• Journal of Korean Society for Geospatial Information Science
• /
• v.17 no.1
• /
• pp.13-19
• /
• 2009

The Gwangalli Beach, one of beaches representative of Busan together with the Haeundae Beach, is a tourist attraction, having increased tourists since the completion of Gwangandaero Bridge in 2003 and recording more than 10 million tourists in 2006. Although the competent local government office has conducted artificial beach nourishment/gravel removal projects every year to manage it, systematic monitoring and studies of erosion are insufficient. This study analyzed the changes in the coastline of Gwangalli Beach using aerial photos, tidal data, GPS survey data for the last sixty years, and examined how the Gwangandaero Bridge, which had been constructed on the Gwanganlli sea, has affected the changes. The results show that the area of Gwangalli Beach has increased 40% for the last sixty years, and that the effects of Gwangandaero Bridge on the coastline are insignificant.