• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.750-750
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• 2002

The Airship PKNU is a roughly 12 m (32 ft) long blimp, filled with helium, whose two-gasoline power(3hp per engine) are independently radio controlled. The motors and propellers can be tilted and are attached to the gondola through an axle and supporting braces. Four stabilizing fins are mounted at the tail of the airship. To fill in the helium, a valve is placed at the bottom of the hull. The inaugural flight was on jul. 31.2002 at the Pusan, S.korea Most environment monitoring system\ problem use satellite image. But, Low resolution satellite image (multi-spectral) : 1km ∼ 250 m ground resolutions is lows. So, detail information acquisition is hard at the complex terrain. High resolution satellite image (black and white) 30m : The ground resolution is high. But it is high price, visit cycle and delivery time is long So. We want make high accuracy airship photogrammetry system. This airship can catch picture Multi. spectral Aerial photographing (visible, Near infrared and thermal infrared), and High resolution (over 6million pixel). It can take atmosphere datum (Temperature (wet bulb, dew point, general), Pressure (static, dynamic), Humidity, wind speed). this airship is very Quickness that aircraft install time is lower than 30 minutes, it is compact and that conveyance is easy. High-capacity save image (628 cut per 1time (over 6million and 4band(R,G,B,NIR)) and this airship can save datum this High accuracy navigatin (position and rotate angle) by DGPS tech. and Gyro system. this airship will do monitor about red-tide, sea surface temperate, and CH-A, SS and etc.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.33-44
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• 1994

This work studies for boiling and condensation heat transfer performance of trapezoidally shaped integral-fin tubes having fin densities from 748fpm to 1654fpm. For comparison, tests are made using a plain tube having the same inside and outside diameter as that of the root of fins of finned tubes. Hahne's theoretical model and Webb's theoretical model are used to predict the R-11 boiling heat transfer coefficient and condensing heat transfer coefficient respectively for plain tube and all integral-fin tubes. Experiments are carried out using R-11 as working fluid. This work is limited to film-wise condensation and pool boiling on the outside surface of plain tube and 4 low integral-fin tubes. In case of condensation, the refrigerant condenses at saturation state of 32$^{\circ}C$ on the outside tube surface cooled by coolant and in case of boiling. the refrigerant evaporates at saturation state of 1bar on the outside tube surface. The amount of non-con-densable gases in the test loop is reduced to a negligible value by repeated purging. The actual boiling and condensing processes occur on the outside tube surfaces. Hence the nature of this surface geometry affects the heat transfer performances of condenser and evaporator in refrigerating system. The condensation heat transfer coefficient of integral-fin tube is enhanced by both extended tube surface area and surface tension. The ratio of the condensation heat transfer coefficients of finned to plain tubes is greater than that of surface area of finned to plain tubes, while ratio of the boiling heat transfer coefficient of finned to plain tubes shows reverse result. As a result, low integral-fin tube can be used in condenser more effectively than used in evaporator.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.243-252
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• 2016

Conventionally, the static angle of attack and static elevator tests are carried out separately to estimate hydrodynamic stability derivatives of underwater vehicles. However, it is difficult to verify the interaction between the angle of attack and elevator angle in such cases. In this study, we perform a static elevator with angle of attack test where both the angle of attack and elevator angle are varied simultaneously. The experimental results show that the angle of attack has an influence on the elevator control force and that this tendency is dependent on the sense in which the angle of attack and elevator angle are varied. We predict level flight performance using hydrodynamic derivatives estimated through this experiment. The predictions considering the effect of angle of attack show good agreement with trials conducted in the open sea.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.12-17
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• 2018

A natural cavitation-type high-speed underwater vehicle with solid rocket motor is tested, and its speed and running distance are measured. The outputs from pressure sensors on the surface of the vehicle reveal a pressure-time history reflecting the development of supercavitation. Underwater cameras installed on the wall of the test pool record the entire process from the onset of supercavitation to its full development. CNU-SuperCT, based on two-dimensional inviscid theoretical analysis, is used to simulate test results. Considering CNU-SuperCT does not include the control fins of the vehicle, simulation results agree with test results very well. Additionally, pictures from underwater cameras support the test results.

• Korean Journal of Breeding Science
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• v.41 no.4
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• pp.377-384
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• 2009

Three-year-old seedlings of susceptible Pinus densiflora and resistant Pinus x rigitaeda were each inoculated with the pinewood nematode, Bursaphelenchus xylophilus, to compare disease development. Needle dehydration was evident on seedlings of P. densiflora by 20 days after inoculation, 10 days earlier than this symptom was observed on P. ${\times}$ rigitaeda. Xylem drying was more frequent in seedlings of P. densiflora than in that of P. ${\times}$ rigitaeda between 20 and 60 days after inoculation. No significant differences were found between P. densiflora and P. ${\times}$ rigitaeda for stem water content or for stem and leaf relative water content in current-year branches after nematode inoculation, but the average number of B. xylophilus recovered from stems differed significantly between the two groups. The number of B. xylophilus recovered from stems was negatively correlated with the stem water content and with stem and leaf relative water content. By the time the experiment was terminated at 60 days after inoculation, all 3 of the last group of P. densiflora seedlings had died, but 2 of the 3 remaining P. ${\times}$ rigitaeda hybrid seedlings were still alive. Additional studies are needed to further explore the specific mechanisms preventing nematode multiplication in the seedlings of resistant P. ${\times}$ rigitaeda.

• Korean Journal of Ichthyology
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• v.31 no.3
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• pp.178-182
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• 2019

This is the first report of Brachirus annularis (Pleuronectiformes: Soleidae) from Korea. A specimen of B. annularis (229.0 mm standard length) was firstly collected by drift gill net at a fishing ground locating between Jejudo and Geomundo Islands, the southern coast of Korea on 31 March, 2019. This species was characterized by having five large, deep colored patches on the ocular side of body, each patch outlined by dark brown ring, united dorsal and anal fins jointed with caudal fin, and short pectoral fin. We add this species to the Korean fish fauna and propose its new Korean names, "Eol-luk-seo-dae-sok" and "Eol-luk-seo-dae" for the genus and species, respectively.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.1093-1101
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• 2020

This study was carried out numerically to investigate the air flow and thermal performance around single and parallel fin-tube heat exchangers and the cooling performance of the fluid inside the heat exchangers. In this study, the air velocity(1~7m/s), the pitch of fin(4, 6.1, 8, 11.3, 18.3, 44mm) and the diameter of fin(31, 33, 35, 37, 39mm) were varied. The flow rate of the water at the fin-tube heat exchanger inlet is 89cc/min and the water temperature is 353K. The air temperature at the upstream region of the heat exchanger is 300K. flow rate of the water at the fin-tube heat exchanger inlet is 80cc/min and the water temperature is 353K. It was found that the air pressure drop around single and parallel fin-tube heat exchangers was highly dependent on the air velocity and the fin pitch, but was independent of the fin diameter. Also, it was shown that pressure drop increased more the parallel arrangements than in single heat exchanger. The temperature difference of water at the inlet and outlet of the heat exchanger depended on the air velocity, the fin pitch and the fin diameter, and it was found that the parallel arrangement method further reduced the temperature of water. It was shown that the Nusselt number increased as the Reynolds number and the fin pitch increased, and decreased as the fin diameter increased.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.2
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• pp.188-193
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• 2021

On March 13, 2018 two postflexion larval specimens (18.28 mm and 16.80 mm in standard length) belonging to the family Cryptacanthodidae, suborder Zoarcoidei were collected from Sokcho and Gangneung in Gangwon Province. The family Cryptacanthodidae comprises 4 species worldwide: 3 in the North Pacific Ocean and 1 in the western North Atlantic Ocean. As a result of analyzing 620 bp of the mtDNA COI region, the two postflexion larvae collected in this study were identified as Cryptacanthodes bergi by 99.5% agreement with C. bergi adult registered in NCBI. Postflexion larvae of C. bergi are compressed with large eyes and radial pectoral fins and the anus located in front of the center of the body. Melanophores were intensively distributed along the dorsal midline, except for caudal peduncle, and sporadically distributed on the back of the anus. In addition, there were limited star-like melanophores on the back of the gut. This species showed 0.058 genetic distance when compared mtDNA COI region of C. aleutensis, and it was well distinguished in the distribution pattern of black vesicles of the head, count and measurement traits. Considering the morphological and ecological characteristics of this species, we suggest a new Korean name, " Gwisin-jang-gaeng-i ".

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.423-431
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• 2022

In this paper, the results of Planar Motion Mechanism (PMM) test for a 1/15 scaled model of the MARIN Joubert BB2 submarine is dealt with to derive the maneuvering coefficients for surface condition. For the depth of surface navigation, the top of the sail was exposed 0.46 m above the water surface in the model scale, and it corresponds to 6.9 m in the full scale. The resistance and self-propulsion tests were conducted, and the model's self-propulsion point was obtained for 1.328 m/s, which corresponded to 10 knots in the full scale. The maneuvering tests were performed at the model's self-propulsion point, and the maneuvering coefficients were obtained. Based on the maneuvering coefficients, a turning simulation was performed for starboard 30 degree of stern fins. The straight-line stability and control effectiveness in the horizontal plane were analyzed using the maneuvering coefficients and compared with the appropriate range. For the analysis of the neutral fin angle of the X-type stern fin, the stern fin test with drift angles was carried out. As a result, the flow straightening effect at lower and upper parts of the stern fin was discussed.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.6
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• pp.1033-1038
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• 2022

In this paper, the design of a printed dipole antenna fed by broadside coupled striplines (BCS) for the 3.5GHz band is described. The two fins of the bow tie are, respectively, on the two sides of the substrate. The feeding balanced lines adopted for 1×2 array are the BCS. The obtained numerical results are in good agreement with experimental data. Through experiments with printed dipole antennas of various extended angles, the printed dipole antenna exhibits the wide bandwidth in the desired frequency band, which has a bandwidth of 28% for VSWR < 2.0 : 1. And within this bandwidth, This printed dipole antenna achieves a stable radiation pattern. It is found that the narrow band and feeding for array characteristic which is a disadvantage of the conventional printed dipole antenna can be improved. The radiation pattern showed omnidirectional characteristics and the maximum gain was about 4.4dBi.