• The Journal of Korea Robotics Society
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• v.9 no.4
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• pp.225-231
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• 2014

Fish generates thrust with a compliant fin which is known to increase the efficiency. In this paper, the performance of a robotic dolphin, the velocity and the stability, was improved using an optimal compliant caudal fin under certain oscillating frequency. Optimal compliance of the caudal fin exists that maximizes the thrust at a certain oscillating frequency. Four different compliant fins were used to find the optimal compliance of the caudal fin at a certain frequency using the half-pi phase delay condition. The swimming results show that the optimal compliant fin increases the velocity of the robotic fish. The compliance of the caudal fin was also shown to improve the stability of the robotic fish. A reactive motion at the head of the robotic dolphin causes fluctuation of the caudal fin. This phenomenon increases with the oscillating frequency. However, compliant fin reduced this fluctuation and increased the stability.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.429-434
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• 2007

This paper presents an experimental and parametric study of a biomimetic fish robot actuated by the Lightweight Piezo-composite Actuator(LIPCA). The biomimetic aspects in this work are the oscillating tail beat motion and shape of caudal fin. Caudal fins that resemble fins of BCF(Body and Caudal fin) mode fish were made in order to perform parametric study concerning the effect of caudal fin characteristics on thrust production at an operating frequency range. The observed caudal fin characteristics are the shape, area, and aspect ratio. It was found that a high aspect ratio caudal fin contributes to high swimming speed. The fish robot was propelled by artificial caudal fins shaped after thunniform-fish and mackerel caudal fins, which have relatively high aspect ratio, produced swimming speed as high as 2.364 cm/s and 2.519 cm/s, respectively, for 300 Vpp input voltage excited at 0.9 Hz. Thrust performance of the biomimetic fish robot was examined by Strouhal number, Froude number, Reynolds number, and Net forward force.

• The Journal of Korea Robotics Society
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• v.5 no.3
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• pp.197-208
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• 2010

The ostraciiform swimming mode allows the simplest mechanical design and control for underwater vehicle swimming. Propulsion is achieved via the flapping of caudal fin without the body undulatory motion. In this research, the propulsion of underwater vehicles by ostraciiform swimming mode is explored experimentally using an ostraciiform fish robot and some rigid caudal fins. The effects of caudal fin flapping frequency and amplitude on the cruising performance are studied in particular. A theoretical model of propulsion using rigid caudal fin is proposed and identified with the experimental data. An experimental method to obtain the drag coefficient and the added mass of the fish robot is also proposed.

• Molecular & Cellular Toxicology
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• v.4 no.4
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• pp.311-317
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• 2008

Zebrafish were exposed to commercial silver nanoparticles (${\sim}$10-20 nm) at 0.4 and 4 ppm during cadual fin regeneration. The silver was in the $Ag^+$ ionic form. Fin regeneration was slow in the group exposed to the lower concentration. The cadual fin, gill, and muscle were assayed after 48 hours and subjected to histological analysis. In all tissues sampled, fish exposed to nanoparticles exhibited infiltration, large mitochondria with empty matrices, and accumulation of nano-sized silver in blood vessels. The results suggested mitochondrial damage and induction of inflammation. Microarray analysis of RNA from young zebrafish (52 hours post-fertilization) that were exposed to nanometer-sized silver particles, showed alteration in expression of the p53 gene pathway related to apoptosis. Gene expression changes in the nanoparticle-treated zebrafish led to phenotypic changes, reflecting increased apoptosis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.5
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• pp.675-677
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• 2016

We report the first occurrence of a tailless Girella leonina, collected from Jeju Island, Korea, in July 2016. This specimen has 10 scales below the median spinous portion of the dorsal fin, a black posterior margin of the operculum, and no pale vertical band on the body, and is therefore similar to the normal species, except that it has no caudal peduncle or caudal fin. The posterior parts of the dorsal and anal fins are gathered vertically at the posterior end of the body. A radiograph indicates that this abnormal specimen is lacking the vertebrae after vertebra 20.

• Ocean and Polar Research
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• v.26 no.4
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• pp.685-688
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• 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 Environmental Biology
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• v.18 no.4
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• pp.387-394
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• 2000

The morphological characteristics between male and female of three species, Chaenogobius urotaenia, C. sp. MR, C. sp. BW, collected from June 1996 to Aug. 1999, Korea was studied. Of 13 characters to be studied, 12 characters with exception of caudal fin ray length were significantly different among three species and these three species were distinguished each other by the results of the multiple comparison test (REGWQ test). Interspecific differences in female was distinct in body depth, head length, caudal peduncle length, caudal peduncle depth, snout length, pectoral fin ray length; In particular, C. sp. MR was shorter in upper jaw length, anal fin ray length and eye diameter, and to be smaller in head depth and head width than other two species. Chaenogobius urotaenia was longer in pelvic fin ray length. In case of male, there was not characters to distinguish each one among three species; Chaenogobius urotaenia was longer in head length, eye diameter and pelvic fin ray length than other two species, C. sp. MR to be longer in caudal peduncle length, but shorter in snout length and anal fin ray length, and to be lower in head depth. C. sp. BW was higher in body depth and caudal peduncle depth, and to be longer in upper jaw length and pectoral fin ray length. Both of male and female among three species didn't have any difference in caudal fin ray length. [Chaeogobius urotaenia, C. sp. MR, C. sp. BW, morphological characteristics].

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.2
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• pp.103-109
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• 2012

Fish generates large thrust through an oscillating motion with a compliant joint of caudal fin. The compliance of caudal fin affects the thrust generated by the fish. Due to the flexibility of the fish, the fish can generate a travelling wave motion which is known to increase the efficiency of the fish. However, a detailed research on the relationship between the flexible joint and the thrust generation is needed. In this paper, the compliant joint of a caudal fin is implemented in the driving mechanism of a robotic fish. By varying the driving frequency and stiffness of the compliant joint, the relationship between the thrust generation and the stiffness of the flexible joint is investigated. In general, as the frequency increases, the thrust increases. When higher driving frequency is applied, higher stiffness of the flexible joint is needed to maximize the thrust. The bending angles between the compliant joint and the caudal fin are compared with the changes of the thrust in one cycle. This result can be used to design the robotic fish which can be operated at the maximum thrust condition using the appropriate stiffness of the compliant joint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.36-42
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• 2007

This paper presents mechanical design, fabrication and test of a biomimetic fish robot actuated by a unimorph piezoceramic actuator, LIPCA(Lightweight Piezo-Composite curved Actuator.) We have designed a linkage mechanism that can convert bending motion of the LIPCA into the caudal fin movement. This linkage system consists of a rack-pinion system and four-bar linkage. Four types of artificial caudal fins that resemble caudal fin shapes of ostraciiform subcarangiform, carangiform, and thunniform fish, respectively, are attached to the posterior part of the robotic fish. The swimming test under 300 $V_{pp}$ input with 0.6 Hz to 1.2 Hz frequency was conducted to investigate effect of tail beat frequency and shape of caudal fin on the swimming speed of the robotic fish. At the frequency of 0.9 Hz, the maximum swimming speeds of 1.632 cm/s, 1.776 cm/s, 1.612 cm/s and 1.51 cm/s were reached for fish robots with ostraciiform, subcarangiform carangiform and thunniform caudal fins, respectively. The Strouhal number, which means the ratio between unsteady force and inertia force, or a measure of thrust efficiency, was calculated in order to examine thrust performance of the present biomimetic fish robot. The calculated Strouhal numbers show that the present robotic fish does not fall into the performance range of a fast swimming robot.

• The Journal of Korea Robotics Society
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• v.6 no.3
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• pp.274-283
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• 2011

A simplified linearized dynamic equation for the propulsion force generation of an Ostraciiform fish robot with elastically jointed double caudal fins is derived in this paper. The caudal fin is divided into two segments and connected using an elastic joint. The second part of the caudal fin is actuated passively via the elastic joint connection by the actuation of the first part of it. It is demonstrated that the derived equation can be utilized for the design of effective caudal fins because the equation is given as an explicit form with several physical parameters. A simple Ostraciiform fish robot was designed and fabricated using a microprocessor, a servo motor, and acrylic plastics. Through the experiment with the fish robot, it is demonstrated that the propulsion force generated in the experiment matches well with the proposed equation, and the propulsion speed can be greatly improved using the elastically jointed double fins, improving the average speed more than 80%. Through numerical simulation and frequency domain analysis of the derived dynamic equations, it is concluded that the main reason of the performance improvement is resonance between two parts of the caudal fins.