• Nuclear Engineering and Technology
• /
• v.29 no.1
• /
• pp.45-57
• /
• 1997

The direct contact condensation phenomenon, which occurs when steam is injected into the subcooled water, has been experimentally investigated. Two plume shapes in the stable condensation regime are found to be conical and ellipsoidal shapes depending on the steam mass flux and the liquid subcooling. Divergent plumes, however, are found when the subcooling is relatively small. The measured expansion ratio of the maximum plume diameter to the injector inner diameter ranges from 1.0 to 2.3. By means of fitting a large amount of measured data, an empirical correlation is obtained to predict the steam plume length as a function of a dimensionless steam mass flux and a driving potential for the condensation process. The average heat transfer coefficient of direct contact condensation has been found to be in the range 1.0~3.5 ㎿/$m^2$.$^{\circ}C$. Present results show that the magnitude of the average condensation heat transfer coefficient depends mainly on the steam mass fin By using dynamic pressure measurements and visual observations, six regimes of direct contact condensation have been identified on a condensation regime map, which are chugging, transition region from chugging to condensation oscillation, condensation oscillation, bubbling condensation oscillation, stable condensation, and interfacial oscillation condensation. The regime boundaries are quite clearly distinguishable except the boundaries of bubbling condensation oscillation and interfacial oscillation condensation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.4
• /
• pp.644-652
• /
• 2002

Increasing demands for Electric Resistance Welded pipes of high quality with thick wall require c lose investigations in edge deformation by slitting, strip deformation during break down farming, and difference of circumferential length. In order to obtain good quality of a welding zone, it is necessary to predict the edge shape of the initial strip. The modeling of the multi-pass thick tube roll forming process with rigid plastic finite element method ultra the edge shape prediction of an initial strip with 2nd-degree polynomial regression method are presented. Edge shapes of initial strip have been analyzed by the finite element method and designed by the regression method to satisfy the requirements in target fin pass. It is concluded that the proposed edge design method results in optimal edge shapes sat string the design requirements.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.57 no.3
• /
• pp.264-269
• /
• 2021

A single postlarva (9.72 mm in standard length) specimen of Crossorhombus azureus (Alcock, 1889) belonging to the family Bothidae, was collected using a bongo net from the southern sea of Korea on December 10, 2019. This species is characterized by having spines on post basipterygial processes. It has two eyes located at the opposite side in head, which accordingly belongs to pre-metamorphosis stage. Melanophores are distributed on the dorsal and anal fin base on the right side (blind side), which is regarded as a useful identification key distinguishing C. azureus from congeneric species in their postlarval stage. A molecular analysis based on mitochondrial DNA COI sequences showed that our specimen was closely matched to adult C. azureus (K2P distance = 0.017). As there is no Korean name for the genus Crossorhombus in spite of presence of Crossorhombus kobensis and its Korean name "Go-be-dung-geul-neob-chi" in Korea, we proposed a new Korean name "Dung-geul-neob-chi-sog" for the genus Crossorhombus and "Pa-lang-dung-geul-neob-chi" for the species C. azureus.

• Korean Journal of Ichthyology
• /
• v.32 no.4
• /
• pp.245-250
• /
• 2020

Two specimens (407~438 mm in standard length) of a pleuronectid Atheresthes evermanni were collected by a gill-net from the coastal waters off Goseong-gun, middle East Sea of Korea. These specimens are characterized by a large mouth, narrow interorbital space, invisible eye at blind side, long and slender gill rakers, emarginated caudal fin, and almost straight lateral line. This is the first record of A. evermanni in Korean waters; we therefore add it to the Korean fish fauna and propose new Korean name, "Hwa-sal-chi-ga-ja-mi-sog" for the genus and "Hwa-sal-chi-ga-ja-mi" for the species, respectively.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.4
• /
• pp.5-10
• /
• 2017

This paper analyzed the heat transfer characteristics on the outer surface of the ambient air vaporizer which received the heat from the air through natural convection by using numerical and experimental methods. The working fluid was a liquid nitrogen. The experimental variables were the length (2,000 mm, 1,800 mm, 1,600 mm) and width of the vaporizer fin and the fluid flow ($6.7m^3/h$, $7.1m^3/h$, $7.5m^3/h$). Based on the temperature data from the experiments, the heat transfer coefficient was calculated. Numerical analyses were also conducted in order to find the heat transfer coefficient for the range of Nusselt number which was difficult to get the data from experiments. The correlation equation between Nusselt number and Rayleigh number were suggested using both the experimental and numerical data.

• Development and Reproduction
• /
• v.25 no.1
• /
• pp.33-41
• /
• 2021

This study was carried out to observe the development of the autonomous skeletal development of the Favonigobius gymnauchen. Total length (TL) of larvae 3 days after hatching (DAH) were mean TL of 3.34 mm, with a line-shaped parasphenoid ossification in the cranium and basioccipital ossification in the back. The 10 DAH larvae had a mean TL of 5.20 mm, with the number of caudal vertebrae increasing to 15. The urostyle and two hypural bones in the lower part also began to ossify. The 23 DAH juveniles had a mean TL of 8.47 mm. The pectoral girdle's skeleton was completed as the scapula and coracoid were ossified. The pelvic girdle also fully supported the ventral fin as its ossification was completed. Favonigobius gymnauchen and Tridentiger obscurus showed similar characteristics in terms of the anus location of hatched larvae, number of myotomes, and melanophore distribution during the morphological development of the larvae and juveniles. However, this study confirmed differences in the development of the vertebrae and urostyle bone.

• Korean Journal of Ichthyology
• /
• v.34 no.2
• /
• pp.133-137
• /
• 2022

Two specimens of Apogon unicolor (81.0 mm and 96.3 mm in standard length) belonging to the family Apogonidae were firstly collected by using a gill net from the southwestern coastal waters of Jejudo Island, Korea in July 2013. These species are characterized by having 26 lateral line pores, a first dorsal fin with 6 spines, 2+1+8=11 developed gill rackers, posterior margin of preopercle serrated, without markings and spots on the body. Our specimens are well-matched in their morphological and molecular characteristics with Apogon unicolor previously reported. Thus, we newly add this species to the Korean fish fauna and propose its new Korean name "Jin-hong-eol-ge-bi-neul" because the overall fish body and fins reveal deep red colors.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.56 no.1
• /
• pp.44-53
• /
• 2023

In this study, the morphological development and early life cycle of larvae and juvenile Rhinogobius brunneus found in Wicheon, Nakdong River, Korea, were investigated. The fertilized eggs were 2.20×0.68 mm (long×short) in diameter. The eggs began hatching approximately 104 h after fertilization at water temperatures of 17.3-20.5℃ (mean 18.9±1.6℃). The newly hatched yolk-sac larvae were 3.71±0.06 mm in total length (TL), with an unopened anus. Three days after hatching, the preflexion larvae were 4.37±0.16 mm in TL with yolk absorption. Twenty days after hatching, the flexion larvae were 6.50±0.22 mm in TL and the tip of the notochord was bent upward. Twenty-seven days after hatching, the postflexion larvae were 11.8±0.63 mm in TL, and the tip of the urostyle was bent at 45°. Forty days after hatching, individuals measured 18.5±0.93 mm in TL and were considered as juveniles as the number of fins became constant for each part. All the postflexion larvae had detached fins. Additionally, the melanophore was observed to be distributed on the head, centrum of the body, and dorsal fin, and there was a difference in the morphology from the water stream.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.11 no.3
• /
• pp.124-132
• /
• 2006

We have investigated morphological development with growth and survival rates of juvenile for 158 days after parturition to get a basis data in the way of establishment of breeding techniques in the common seahorse species of Barbour's seahorse, Hippocampus barbouri. At 1 day after parturition, seahorse larvae were $8.82\sim10.36mm(mean\;9.48{\pm}0.69mm,\;n=4)$ in standard length (SL) with 17 dorsal fm rays, 14 pectoral fin rays and 4 anal fin rays. At 20 days after parturition, the size of seahorse larvae were $14.37\sim15.79mm(14.97{\pm}0.62mm,\;n=4)$ in SL, snout of seahorse larvae became slender was long, and body was coloration to the full as adult seahorse. At 41 days after parturition, seahorse larvae were grew $20.14\sim24.89mm(22.89{\pm}2.22mm,\;n=4)$ in SL with development of several spines in coronet, and their have 11 trunk rings and 35 tail rings. At 158 days after parturition, seahorse were grew to $59.07\sim63.76mm(61.42{\pm}3.32mm\;n=2)$, and head length (HL), trunk length (TrL) and tail length (TaL) were composed respectively $19.1{\pm}0.3%,\;25.2{\pm}0.7%$ and $55.8{\pm}0.3%$ of SL. In this time, survival rate is 15.6%.

• Journal of Aquaculture
• /
• v.20 no.2
• /
• pp.96-105
• /
• 2007

A pair of maroon clownfishes with an indonesian native, reared in recirculation culture system to develope its aquaculture techniques. Courtship, spawning behavior, egg developments and rearing of the maroon clownfish larvae were documented. The larval development were described with illustrative figures. The spawning was occurred 8 times between Feburary and August 2004. The gravid female spawned during 15:00-20:00. The male mainly took care of the eggs supplying oxygen by water currents using their pectoral fins, anal fin and mouth. The fertilized eggs were separative-adhesive and oval in shape, and $1.99{\pm}0.03\;mm$ in longer diameter and $0.88{\pm}0.03\;mm$ in shorter diameter. The fertilized eggs were in deep-orange color. Cleavage occurred in 30 minutes after fertilization, and the egg reached 2 cells stage in 1 hour 10 minutes after fertilization at $27.0^{\circ}{\pm}0.5^{\circ}C$. The embryo was formed in 23 hours 40 minutes after fertilization. Hatching began in between $120{\pm}2$ hours and $150{\pm}12$ hours after fertilization at $27.0^{\circ}C$ in the incubator. Total length (TL) of the newly hatched larvae was 3.22 mm with mouth and anus opened. Ten days after hatching, mean TL of the larvae were 6.21 mm with 28 dorsal fin rays, 17 anal fin rays and 28 caudal fin rays. Nineteen days after hatching, mean TL of the larvae were 9.34 mm. At this stage the larva had three white bands on the body, and they began to feed on commercial diet.