• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.8
• /
• pp.579-585
• /
• 2019

Increasing the detection probability of underwater targets necessitates securing the towing stability of the active towed SONAR. In this paper, to confirm the effects of tail wing fin on towing attitude and towing stability, two scale model experiments and one sea trials were conducted and the results were analyzed. The scale model tests measured the towing behavior of each of the tail fin shapes according to towing speed in a towing tank. The shape of the tail fin used in the scale model test was tested with an I-type tail fine and four Y-type tail fins, totaling five tail fins of the two kinds. The first scale model test confirmed that the Y-type tail fin was superior to the I-type tail fin in towing attitude and towing stability. The second scale model test confirmed the characteristics of the vertical tail fin height increase and the lower horizontal tail fin inclination angle application shape based on the Y-type tail fin. The shape of the application of the lower horizontal tail fin inclination angle showed the best performance. In order to verify the results of the scale model test, a full size model was constructed, sea trials were performed, and the towing attitude was measured. The results were similar to those of the scale model test.

• Journal of the Society of Naval Architects of Korea
• /
• v.44 no.2 s.152
• /
• pp.55-63
• /
• 2007

Fins are widely used for roll stabilization of car ferries and passenger ships as well as high performance naval ships. In the present study, model experiments and numerical simulations are performed to investigate the influence of tail blades on the performance of a fin stabilizer for various angles of attack. It is found that a considerable improvement in performance of the fin stabilizer is achieved with adoption of the tail blades. The results can be utilized for the design of a high-lift control surfaces including fin stabilizers.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.22 no.5
• /
• pp.625-636
• /
• 2019

Recently, research on projectiles with wings for precision guidance is actively underway. In this study, we analyzed how the tail fins attached to the projectile affect the base drag. Aerodynamic analysis was performed with RANS(Reynolds Averaged Navier-Stokes) equations using FLUENT, a commercial CFD(Computational Fluid Dynamics) code. Through the aerodynamic analysis, the base drag characteristics of the projectile by parameters (number, length, thickness, position, shape of tail fin) were investigated. The results of this study are expected to be applicable to aerodynamic design of tail fins mounted on projectiles.

• Ocean Science Journal
• /
• v.41 no.4
• /
• pp.201-205
• /
• 2006

Larval specimens of Halicampus punctatus were collected off Ulsan and Uljin in December 2002 (three specimens) and off Ulsan in December 2003 (one specimen). These specimens are characterized by the following morphological characteristics: rings, 14 + 35 = 49; subdorsal rings, 1 + 3 = 4; dorsal fin rays, 19 - 20; pectoral fin rays, 14 - 15; anal fm rays, 9; head length (HL), 5.8 - 6.7 in the standard length; snout length, 1.9 in HL; snout depth, 3.7 - 5.2 in snout length. The number of caudal fin rays 9 is less than those of the other species in the same genus 10. Wide stripe bands composed of small pigments are shown in the trunk and the tail. Melanophores are not found in the dorsal fin, the pectoral fin, and the anal fin except the caudal fin. The supraoccipital crest is on the head. The frontal ridge is on the dorsal side of front trunk. The blanched ridges on the opercular are fused with a main ridge like a tree branch. A few branched ridges that are small and narrow on the trunk and the tail are fused with the main ridges. We report these specimens as the first record in Korea and name them 'Byeol-sil-go-ki' in Korean.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.537-541
• /
• 2003

In order to control the missiles by aerodynamics, control surfaces sometime called fins are used. Deflection angles of these fins are the right control variables of the aerodynamics, but aerodynamicists prefer to use analytic variables called aileron, elevator and rudder instead of these physical variables, because these three analytic variables dominantly influence on the roll, pitch and yaw channels of the missile maneuver, respectively, and each can be assumed a linear combination of four fin deflection angles. On that basis, roll, pitch and yaw autopilots for controlling the attitudes or lateral acceleration of the missile are designed, and as a consequence outputs of each autopilot are aileron, elevator and rudder commands, respectively. In the existing fin control scheme for the typical tail-fin controlled cruciform missiles, firstly these outputs are distributed to four fin defection commands, and after that four fins are actuated by fin controllers so that their deflections follow the commands. This paper shows that performance of such control schemes can be degraded significantly when fin actuators have certain physical constraints such as slew rate, voltage or current limit, uncertainty of actuator dynamics, and so on, and propose a new control scheme which alleviates such problems. This scheme can be widely applied to various fin actuation systems. But in this paper, for convenience, tail-fin controlled cruciform missile is taken as an example, and it is shown that a proposed control scheme gives better performance than the existing one.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.1
• /
• pp.45-54
• /
• 2022

There has been necessity to supplement the fin database to improve the accuracy of low-fidelity aerodynamic solver for missile configuration. In this study, fin database is expanded by in-house solver, utilized in the triservice data the previously established into regions beyond means of CFD. Fin alone data of CFD analysis results in the original region is matched well with triservice data originated from the wind tunnel tests. Extensive fin aerodynamic data from CFD analysis is added to the existing database of the low-fidelity solver. For confirmation, aerodynamic characteristics of body-tail and body-canard-tail missile configurations is computed using upgraded low-fidelity solver at transonic region. The result using improved solver shows good agreements with wind tunnel test and CFD analysis results, which implies that it becomes more accurate.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.42 no.6
• /
• pp.725-728
• /
• 2009

Four specimens of Cynoglossus larvae (3.2-7.3 mm in notochord length, NL) collected from the middle Yellow Sea in August, 2008 were identified as Cynoglossus joyneri larvae based on morphological characteristics; (1) the two elongated dorsal fin rays on the parietal region, (2) protruded abdomen, (3) no melanophores on the mediolateral trunk and tail. Larva of 3.2 mm NL is compressed with a little big head and tapering, long tail. Larva of 7.0 mm NL has 115 dorsal fin and 85 anal fin rays, which are the same to those of adult. Larva of 7.3 mm NL tended to have concave part in the fringe of forehead, in which left-side eye may move to the other side.

• Development and Reproduction
• /
• v.21 no.2
• /
• pp.193-204
• /
• 2017

The influence of triploidization on histological characteristics of retina, trunk kidney, liver and midgut tissue, and cell cycle of tail fin and gill tissue in far eastern catfish, Silurus asotus were analyzed. In the infertile triploid fish, the nucleus and/or cell size of secondary proximal tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger than those of the corresponding cells in the diploid fish (P<0.05). However, triploid tissue showed fewer number of outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk kidney than those for diploid tissue. The mean percentages of the $G_l-$, the S- and the $G_2+M-phase$ fractions were 92.5%, 3.2% and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of triploid, respectively. There were no significant differences in the percentages of each cell cycle fraction between diploid and triploid. The mean percentages of each phase fractions were 75.1%, 11.1% and 13.8% in gill tissue of diploid and 85.2%, 8.9% and 5.9% in those of triploid, respectively. The differences of cell cycle between tail fin tissue and gill tissue were statistically significant in diploid and triploid (P<0.05). Also, the differences between diploid and triploid were statistically significant in tail fin tissue and gill tissue (P<0.05). Cyclin D1 and cyclin E expressions were not significantly difference between gill tissue and tail fin tissue, and protein expressions of induced triploid were higher than those of diploid. Results from this study suggest that some characteristics in the triploid exhibiting larger cell and nucleus size with fewer number of cell than diploid can be used as an indicator in the identification of triploidization and ploidy level in far eastern catfish.

• Ocean and Polar Research
• /
• v.26 no.4
• /
• pp.685-688
• /
• 2004

The morphology of the post-larva of Liopropoma japonicum of the family serranidae is described from one specimen collected off Jeju Island ($32^{\circ}42'N,\;127^{\circ}45'E$) on May 3, 2001. The body is laterally compressed and caudal peduncle deep at 19.4 mm BL. Anus locates at a vertical through posteriormost(8th) dorsal-fin spine. Dorsal fin rays were VIII, 14; anal fin rays III, 10; pectroal fin rays 16; pelvic fin rays I, 5. A caudal fin is rounded. Length of elongate second and third dorsal-fin spines are 499% and 423% of the body length, respectively. A series of 50 sensory pores on body is elongated to caudal fin. Head spination is well developed. Melanophores are moderately large and dense in the head, and are small and rare in teh neck. Being freshly collected, the body color is yellowish-red and tail is semitransparent. The head is yellowish-red and the brain is dark-red.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.8 no.4
• /
• pp.225-233
• /
• 1975

Morphological changes of early post-larval and young stages of Chasmichthys dolichognathus HILGEnDORF (Family Gobiidae) have been studied based on the samples of 953 individuals collected in June 1968, July 1969 and July 1971. Particular emphasis was paid on the development of fin rays, chromatophore patterns and ventral fins. The primordial fin rays of the first dorsal fin appear in the post-larvae of around 8.0 mm in total length, and dorsal fin fully develops in the larvae of around 9.2 mm. In the early young stages of 17.0 mm in total length fin rays have completely developed. According to chromatophore patterns the larvae are grouped into three successive groups. The larvae at the early stages of 6.3-14.2 mm have melanophores on the whole dorsal surface, the posterior ventro-lateral part of the tail and the basal part of the caudal fin. In the later larval stages of 17.0-24.4 mm a group of melanophores are added on medio-lateral part of the tail. These melanophores extend anteriorly and eventually cover the medio-lateral part of the whole body. In the early young stages of 97.2-34.8 mm the chromatophores cover the whole body surface in cloudy and H-shaped patterns. The chromatophore patterns of this stage are distinctive as generic characters of the fish. Fin membranes of the ventral fin appear in the post-larval stage (ca. 7.4 mm), and the primordial fin rays develop in the late post-larval stages (ca. 14.2 mm). The fin rays develop into a complete sucker in the young fish stage of around 30.0 mm in total length.