• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.43-49
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• 2007

Anatomical properties of Kenaf (Hibiscus cannabinus L.) planted in a reclaimed-land of Korea were examined to understand the growth characteristics by an optical and scanning electron microscopy. The samples of kenaf were taken from four positions of the stem (3, 35, 70, 105 cm above from the ground) in four growth periods (July. August, September, October) from seeding planted in the middle of May. Bast fiber, phloem rays, cortex parenchyma cells and sieve tube members were observed in phloem, and vessel elements, fibers and rays in xylem. Solitary and multiple radial pores existed in xylem. The cell types of ray parenchyma in radial section were procumbent, upright, and square. The intervascular pitting showed an alternate type. Xylem proportion, the number of bast fibers and dimension of phloem rays increased with increasing growth period, and decreased with increasing stem height. The proportion of multiseriate rays was higher than that of uniseriate and biseriate rays in xylem with increasing growth period. On the other hand, The proportion of multiseriate rays was lower than that of uniseriate and biseriate rays in xylem with increasing stem height.

• Korean Journal of Plant Resources
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• v.23 no.1
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• pp.31-37
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• 2010

It was investigated that morphological characteristics of leaf and stomata, chlorophyll contents and wood anatomy characteristics in Schisandra chinensis, Schisandra nigra and Kadsura japonica. Leaf morphological characteristics were significant at 5% levels within the species and within the individuals as a male, a female and monoecious. K. japonica was the longest in the leaf length, followed by S. chinensis and S. nigra. For the leaf length among S. nigra individuals, the female was longer than male and monoecious. As for the Petiole length, S. nigra was twice longer than S. chinensis and K. japonica. Stomata length was ranged from $92.5\;{\mu}m$ to $105.9\;{\mu}m$ for S. nigra, $79.9\;{\mu}m$ for S. chinensis, $76.2\;{\mu}m$ for K. japonica. S. nigra was longer than the others in length and width, while its stomata density was lower than the others. The size of vessel elements and xylem fiber showed a similar tendency to stomata, significant at 5% levels within S. nigra individuals (male, female and monoecious). Chlorophyll contents were also variable in inter and intra species and in general K. japonica showed higher levels of chlorophyll contents than Schisandra spp. plants.

• Strategy21
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• s.44
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• pp.177-212
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• 2018

The purpose of this article is to examine the 'Discussion of maritime defense' which began to be discussed from the late Goryeo dynasty to the early Joseon dynasty and the process of establishing a maritime defense system. Also it can identify changes in the aspects of the naval ship operation and their strategic tactics during the reign of King Sejong. Japanese raiders began a full-scale invasion from 1350 at the late Goryeo Dynasty, So the government realized the need to raise the 'Sea power' and to organize the maritime defense system for defending enemy invasion. for example, the reinforcement of naval forces, construction of warships, develoment of weapon systems and so on. which have achieved remarkable growth while continuing, have also been used to carry out a three-time 'Conquest of Daemado' in 1389, 1396, 1419. Until then, however, it is difficult to interpret that the naval forces had a systematic and organizational combat operation system. According to fighting patterns on combat reports before the early days of King Sejong's reign, Our naval forces had no advantage over the Japanese raiders in terms of their capabilities and tactics. Then, the period of King Sejong marked a watershed in maritime defense history. Based on accumulated experience of naval battles and force Projections, The paradigm shift of the naval strategic tactics for maritime defense has occurred. First, the capability of the naval vessels has improved. for example, ship speed, durability, and weather resistance. Through these efforts, navy forces were able to pursue and attack, destroy enemy's ships by taking advantage of the 'Ship speed superiority'. This has led to tactical shifts from defensive to offensive. Second, purpose to support offensive tactics, the government put a strategic plan into practice that is the forward depolyment of naval bases from the inland to the coast, considering the 'sea environment' and 'threat'. By doing so, Joseon dynasty was able to secure 'the command of the sea'. This may be a little different from the perception of the so-called 'peace period' that King Sejong's era. We need to remember that Joseon dynasty was working hard for its defense. When studying history of maritime defense, these strategic and tactical elements must be fully considered. Only then we can have a coherent understanding of the many naval battles in the past, including the Imjin War(1592-1598).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.111-116
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• 2005

The approaching waters of Po-hang port will be increased the traffic volume and passage of larger vessel according to the opening of Young-il new port in 2006. But the adjacent area of Po-hang port still exist the danger elements of safe navigation, the disordered navigation and traffic congestion. Therefore the safety of traffic must be improved in Po-hang vicinity area. This paper describes the status of marine traffic flow and navigational characteristics based on the marine traffic survey using the exclusive software, and the results of marine traffic survey classify into the ship's types and tonnage and track history of passing ships through the statistical method. Finally the examinations of main traffic route, traffic flow and navigational characteristics are discussed, and these results can be utilized the best design of ship's routing at the Po-hang approaching water.

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.409-415
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• 2011

The method to improve the detection sensitivity of Hand-held XRF (X-Ray Fluorescence) device currently being developed is discussed. To minimize the loss of the intensity due to atmospheric gas molecules, the vacuum module, which can be filled with atmospheric or He gas, between the sample and the detector was installed. And the change of the detection sensitivity was measured in a vacuum and in the He gas-filled state. As a result, the following three important results were obtained; Firstly, XRF intensity was increased 2~4 times in the low energy range (3~4 keV). It is a very important result because the enhancement of the detection sensitivity means shortening of the detection time in Hand-held XRF device. Secondly, the possibility of detection of the elements less than 3 keV in emission energy was confirmed. Thirdly, the absorption by atmospheric gas molecules can be minimized without vacuum- sealed vessel in Hand-held XRF device, if the vacuum module filled with He gas is used. We concluded that all of three results are very meaningful in the development of a Hand-held XRF device.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.438-444
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• 2018

Korea has recently selected twenty-two ports for reinforcement breakwater installation of protection facilities, due to rise sea level caused by global warming and increase in the number of typhoon and tsunami. In addition, due to consistent enlargement of ship size, dredging for depth of water for large vessel's berthing and enlargement of berth is under construction. However, no definite construction plan for the reinforcement and lengthening of crown height, which has close relationship with the safe mooring of ships. In this study, domestic and foreign design criteria of crown height were analyzed, and the crown height evaluation index and evaluation method were developed by dividing it into environment and ship elements. In particular, in the case of ship evaluation index, each step was set up in 4 steps according to domestic and foreign regulations, weighted by each step, and the safety level of crown height was evaluated. As a result of the mooring safety simulation of the 100,000 ton cruise ship, the appropriate minimum crown height standard was derived to be 3 m above A.H.H.W. The results of this study are expected to be used as basic data to propose the crown height standard reflecting ship characteristics.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.112-125
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• 2021

Marine spatial planning(MSP) designates the marine as nine kinds of use zones for the systematic and rational management of marine spaces. One of them is the fishery protection zone, which is necessary for the sustainable production of fishery products, including the protection and fosterage of fishing activities. This study intends to quantitatively identify the fishing activity space, one of the elements necessary for the designation of fisheries protection zones, by mapping of fishery activities using V-Pass data and deriving the fishery activity concentrated zone. To this end, pre-processing of V-Pass data was performed, such as constructing a dataset that combines static and dynamic information, calculating the speed of fishing vessels, extracting fishing activity points, and removing data in non-fishing activity zone. Finally, using the selected V-Pass point data, a fishery activity map was made by kernel density estimation, and the concentrated space of fishery activity was analyzed. In addition, it was confirmed that there is a difference in the spatial distribution of fishing activities according to the type of fishing vessel and the season. The pre-processing technique of large volume V-Pass data and the mapping method of fishing activities performed through this study are expected to contribute to the study of spatial characteristics evaluation of fishing activities in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1098-1105
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• 2021

The International Maritime Organization has steadily strengthened environmental regulations on nitrogen oxides and carbon dioxide emitted from marine vessels. Consequently, the demand for electric propulsion vessels based on eco-friendly elements has increased. To this end, research and development has been steadily conducted for various vessels. In electric propulsion systems, a redundancy configuration is typically adopted to increase reliability and facilitate the onboard arrangement. Furthermore, studies have been actively conducted to ensure the safety of electric propulsion systems through the combination with digital twin technology. A digital twin can be used to predict outcomes in advance by implementing real-world equipment or space in a virtual world like twins, integrating real-world information and data with the virtual world, and performing computer simulations of situations that can occur in a real environment. In this study, we perform failure modes and effects analysis (FMEA) to validate the electric power management system (PMS) redundancy scheme for the digital twin technology development of electric propulsion vessels. Then, we propose the role and algorithm of PMS as a compensation function for preventing primary and secondary damages caused by a single equipment failure of the PMS and preventing additional damages by analyzing the impact on the entire system under real vessel operating conditions based on the redundancy FMEA suggested for the ship classification and certification. We verified the improvement in propulsion conservation through tests.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.857-862
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• 2023

In order for an autonomous ship to arrive near the pier and automatically berth without the help of a tugboat or pilot, it is necessary to recognize the pier and calculate the thruster output and output angle for berthing to the pier at a fixed berthing speed under given external force conditions. Therefore, in this study, the external force and moment acting on the ship while berthing were analyzed, and the thruster output calculation for automatic berthing was designed and the basic concept for the development of the automatic berthing program was designed. The wind pressure applied to the hull by the wind while the ship is berthing was calculated based on the wind pressure area and the wind direction angle and the turning moment to rotate the ship according to the transverse force of the ship was calculated. Considering the force acting on the ship and the turning moment during berthing, a theoretical formula was presented to calculate the thruster output and output angle for berthing parallel to the pier, and the turning due to other variables was controlled by the PID controller. In addition, the basic concept for program development was presented by analyzing the input elements necessary for the theoretical formula.

• Journal of the Korean Wood Science and Technology
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• v.15 no.2
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• pp.26-52
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• 1987

Among the diffuse-porous woods which arc dominant in Korea and used as construction materials due to their wood quality, ten species of six genus involving seven species of three genus in Betulaceae were studied on the radial variation of structural demenb. The species studied were Betula platyphylla var. japonica, B. ermanii, B. davurica, B. scstata, B. schmidtii, Carpinus laxifora, Alnus japonica, Prunus sargentii. Acer mono and Diospyros kaki. Wood fiber, vessel elements and ray increased rapidly in size from pith to a certain annual ring. After then the radial variation in size of the main structural elements seemed to be divided into three types; levelled off curve pattern indicating constant size(type I), continuously increasing curve pattern showing ever increase in size (type II) and parabolic curve pattern showing the gradual decrease after the maximum (type III), but the variation types by structural dements were different even in the same species. Based on the results from this study, it appears to be reasonable to consider the stabilized age of wood fiber, vessel elements and ray rather than considering wood fiber length in distinguishing mature woods from juvenile woods.