• Korean Journal of Ichthyology
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• v.35 no.2
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• pp.75-82
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• 2023

The samples used in this study were collected on two occasions (April 21 and May 16, 2021) from Liobagrus mediadiposalis and spawned egg masses located under rocks in Daeseocheon, Yeongdeok-gun, Gyeongsangbuk-do. Fertilized eggs ranged in size from 3.30~3.92 (average 3.57±0.19) mm (n=30), and it took 152~155 hours to hatch at water temperatures of between 17.0 and 20.0℃. Newly hatched larvae immediately post-hatching had a total length of 6.43~6.67 (6.55±0.07) mm (n=30), and were characterized by the retention of a yolk sac and an incompletely open mouth and anus, consistent with the yolk. On the 9 days post-hatching, the postflexion larvae had grown to length of between 11.0~13.8 (12.3±0.70) mm (n=30), and the caudal bone at the tip of the tail was bent upwards at an angle of 45°, thereby indicating the transition to the late larval growth stage. On the 16 days post-hatching, the total length of juvenile had increased to between 15.8~18.2 (16.8±0.77) mm (n=30), and the number of fins reached a fixed number of 8 dorsal, 17 anal, and 8 pelvic fins. On the basis of the findings of this study, we were able to confirm differences in the size of hatching larvae and fin mottle patterns in the early life history of related species.

• Korean Journal of Ichthyology
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• v.12 no.2
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• pp.137-145
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• 2000

The embryonic and larval development of Chelon lauvergnii (Eydoux & Souleyet) was surveyed by incubating artificially inseminated eggs with parent fishes obtained at Kang-wha island in the mid-western coastal area of Korea on June, 1997. The fertilized eggs were transparent, spherical in shape, measuring 0.95~1.08 mm in diameter, having a large oil globule, and their perivitelline space narrow, and began to hatch at 40 hrs. in water temperature $22{\pm}1^{\circ}C$. The newly hatched larvae were 2.35~2.68 mm in total length with 23 myomeres, anus opened, mouth closed, preanal length 58.7~61.6% of total length, oil globule located in posterior end of yolk sac. Melanophores, branch in shape, were distributed mainly along the ventro-lateral region of trunk part and a few on the anterior end of caudal part and surface of oil globule. The larvae measuring 3.08~3.36 mm in total length absorbed yolk material completely in 3 days after hatching, in which air bladder began to appear and mouth opened. In 8 days after hatching, the larva was measured 5.09 mm in total length, its posterior end of notochord began to flex upward and the caudal fin rays differentiated as 7, finfold of the second dorsal and anal fins appeared. In this time, melanophores, branch in shape, were concentrated in the anterior half region of the caudal part and a few also distributed on the top of head, snout region, ventral margin of lower jaw and isthmus region. In 12 days after hatching, the larva measuring 8.48 mm in total length completed all the fins (D. IV-9; P1. 16; P2. I, 5; A. II, 9) and reached to the juvenile stage. Melanophores, in this time, were distributed on the mid-lateral region of the caudal part in enlargment than before and a few also found in the dorso-lateral region of the trunk part, and in the cheek region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1434-1443
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• 1999

The turbulent fluctuations of temperature and two components of velocity have been measured with hot- and cold-wires in the Thermally Stratified Wind Tunnel(TSWT). Using the fin-tube heat exchanger type heaters and the neural network control algorithm, both stable ($dT/dz=109.4^{\circ}C$) and unstable ($dT/dz=-49.1^{\circ}C$) stratifications were realized. An ambient air jet was issued normally into the cross flow($U_{\infty}=1.0 m/s$) from a round nozzle(d = 6 mm) flushed at the bottom waII of the wind tunnel with the velocity ratio of $5.8(U_{jet}/U_{\infty})$. The characteristics of turbulent dispersion in the cross flow jet are found to change drastically depending on the thermal stratification. Especially, in the unstable condition, the vertical velocity fluctuation increases very rapidly at downstream of jet. The fluctuation velocity spectra and velocity-temperature cospectra along the jet centerline were obtained and compared. In the case of stable stratification, the heat flux cospectra changes Its sign from a certain point at the far field because of the restratification phenomenon. It is inferred that the main reason in the difference between the vertical heat fluxes is caused by the different length scales of the large eddy motions. The turbulent kinetic energy and scalar dissipation rates were estimated using partially non-isotropic and isotropic turbulent approximation. In the unstable case, the turbulent energy dissipation decreases more rapidly with the downstream distance than in the stable case.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.46-51
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• 2009

In this work, the experimental investigation was carried out to evaluate the heat transfer performance on the shell side of shell-and-plate finned tube heat exchanger with three different tube numbers(9, 13 and 19). Oil flowing on the shell side was cooled by cold water flowing inside the tubes. A shell-and-tube heat exchanger of an oil cooler consisted of one shell pass and two tube passes with the inner tube diameter of 8.82 mm and the tube length of 575 mm. Mass flow rate was varied from 1.2 to $6.0\;m^3/h$ for oil and from 0.6 to $3.0\;m^3/h$ for cold water, respectively. From the experiment of shell-and-plate finned tube heat exchanger, the overall heat transfer coefficient of heat exchanger with 9 tubes was compared with that of 13 and 19 tubes. It was found that the heat transfer coefficients in shell side of heat exchanger with 9 plate finned tubes showed averagely 1.8 times and 2.3 times higher than those of 13 and 19 tubes, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.6
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• pp.478-484
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• 2008

To elucidate the spawning behavior and early life history of Liobagrus mediadiposalis, mature male and female fish were collected from a branch of the Seomjin River. Spawning was induced by injecting hormones, and then the spawning process and development of fertilized eggs, larvae, and juveniles were observed. Observations of spawning behavior showed that the female established a territory and built a spawning nest, and frequently pressed on the upper ventral part of the male to release her eggs. When spawning was finished, the fish supplied fresh water to the egg mass using their pectoral and caudal fins. Hatching began 189 h 20 min after fertilization at $21.5-23.5^{\circ}C$ (mean $22.7^{\circ}C$). The mean total length (TL) of newly hatched larvae was 7.18-7.39 mm (mean 7.31 mm). Their mouth and anus were already open and they had 14+24=38 myotomes. Eighteen days after hatching, the larvae were 12.71-13.79 mm (mean 13.27 mm) in TL and the yolk sac was absorbed completely. At 35 days after hatching, when all the fin-rays had formed, the juveniles were 15.84-17.92 mm (mean 16.33 mm) in TL.

• Korean Journal of Ichthyology
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• v.22 no.4
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• pp.279-284
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• 2010

Four leptocephali (TL 109.8~129.7 mm) of the family Ophichthidae, collected from Sangju in the South Sea of Korea, were identified using morphological and molecular methods. Our four leptocephali were similar to Ophichthus sp. based on morphological characters: the melanophores present in series of eight gut swellings; total myomeres 144~151; body depth in total length less than 10%; eight or nine black horizontal bands present from anus to caudal fin base. On the other hand, our four leptocephali were identified to Pisodonophis sp. based on 826 base pairs of 12S rRNA gene nucleotide sequences. Our results showed that morphology-based identification did not agree with molecular identification, indicating difficulty in differentiating morphologically between Ophichthus and Pisodonophis leptocephali. We, herein, firstly describe morphological characteristics of Pisodonophis sp. leptocephali from Korea.

• Korean Journal of Ichthyology
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• v.27 no.3
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• pp.238-242
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• 2015

Three specimens (56.7~92.4 mm in standard length) of the small psychrolutid Psychrolutes pustulosus (Schmidt, 1937) were collected by bottom trawl in the coastal waters off Pohang, the southern East Sea, Korea. This species is characterized by large cephalic pores, no markings on the body or fins, no spines on the head, and no notch between the spiny and soft-rayed dorsal fin. We describe specimens the southernmost distribution in the world, and compare them with two congeneric species from Russia. We thus present the first record of Psychrolutes pustulosus (Schmidt, 1937) within the Korean fish fauna and propose the new Korean name "Min-mu-nui-mul-su-bae-gi" for this species.

• Journal of Aquaculture
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• v.9 no.1
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• pp.11-18
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• 1996

We described morphological characteristics of embryonic, larval, and juvenile period of the yellow puffer, Takifugu obscurus. We defined seven periods of embryogenesis the zygote, cleavage, blastula, gastrula, segmentation, pharygula, and hatching periods. The eggs were adhesive and spherical in shape. The egg yolk had numerous tiny oil globules. Hatching began about 280 hours after insemination at $17.0{\pm}1.0^{\circ}C$ water temperature. Melanopores of star shape were seen on yolk, head and trunk during the pharygula and hatching period. The hatched larvae haying large yolk were $3.00\~3.54$ mm in size with $25\~26$ myomeres. The larvae completely absorbed the yolk materials and oil globules within 7 days after hatching and became post-larvae. Laval fish became juveniles within 60 days after hatching, and they reached $23.54\~30.12$ mm in total length and had fin-rays.

• Wind and Structures
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• v.29 no.6
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• pp.457-469
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• 2019

In this paper, a numerical solution is presented for supersonic flutter analysis of cantilever non-symmetric functionally graded (FG) sandwich plates. The plate is considered to be composed of two different functionally graded face sheets and an isotropic homogeneous core made of ceramic. Based on the first order shear deformation theory (FSDT) and linear piston theory, the set of governing equations and boundary conditions are derived. Dimensionless form of the governing equations and boundary conditions are derived and solved numerically using generalized differential quadrature method (GDQM) and critical velocity and flutter frequencies are calculated. For various values of the yaw angle, effect of different parameters like aspect ratio, thickness of the plate, power law indices and thickness of the core on the flutter boundaries are investigated. Numerical examples show that wings and tail fins with larger length and shorter width are more stable in supersonic flights. It is concluded for FG sandwich plates made of Al-Al₂O₃ that increase in volume fraction of ceramic (Al₂O₃) increases aeroelastic stability of the plate. Presented study confirms that improvement of aeroelastic behavior and weight of wings and tail fins of aircrafts are not consistent items. It is shown that value of the critical yaw angle depends on aspect ratio of the plate and other parameters including thickness and variation of properties have no considerable effect on it. Results of this paper can be used in design and analysis of wing and tail fin of supersonic airplanes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.26-34
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• 1996

Copulation process, fertilization and gestation of the viviparous teleost surfperch, Ditrema temmincki were investigated by using photomicroscopy. Samples were collected from the vicinity of Suyoung Bay, Pusan, Korea from May 1992 to August 1993. During the copulation period, the copulatory organs were protruded at the base part of right and left soft ray of the anal fin in mature male. Secondary sexual characteristics index (SSCI) of male participated in copulation was above 3.5. Mature oocytes appeared only in the female containing sperms in the ovarian cavity. Transport of the spermatozoa into the ovarian cavity during copulation belonged to a spermatophore type. After copulation, spermatozoa remained in the ovarian cavity for about one month untill fertilization. Fertilization occured within the follicular cavity. Fertilized eggs were released into the ovarian cavity where they developed during gestation period. Developmental sequence of the female was as following: fertilization-ovulation-hatching-parturition. Right before parturition, the total length (TL) of the embryo was about 63.0 mm. When TL of maternal body was 20.0 cm, the mean numbers of the embryo were 18. The numbers of the embryo were positively related to the maternal body size.