• Korean Journal of Ichthyology
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• v.28 no.4
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• pp.239-248
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• 2016

The habitat, age and spawning characteristics of the Korean eastern spined loach, Iksookimia yongdokensis, were investigated to obtain baseline data for its ecological characteristics in the Chuksancheon (stream), Yeongdeok-gun, Gyeongsangbuk-do, Korea. The difference between the habitats of juveniles (0+) and 1~4 year old loaches was that juveniles mainly inhabited sandy bottoms (substratum particle size $0.6{\pm}1.44\;cm$) with very slow velocities of water current ($2.4{\pm}2.09\;cm/sec$) and low depths ($29.2{\pm}7.57\;cm$), whereas 1~4 year old loaches inhabited pebble and cobble bottoms (substratum particle size 5.5~6.1 cm) with relatively fast velocities of water current (3.8~4.6 cm/sec) and deep depths (50~70 cm). The age groups for I. yongdokensis (female) estimated by the frequency distribution of total length in the spawning season (July) indicated that the 35~64 mm is 1-year old, the 65~94 mm group is 2-year old, the 95~119 mm is 3-year old, and the 120~145 mm is more than 4-year old. The sex ratio (♂/♀) was 0.69, and females were 10~30 mm larger than males. The lamina circularis at the base of the pectoral fins in males, a secondary sexual characteristic, formed at the 13th month after hatching. The spawning season according to the gonadosomatic index (GSI) was June to July with water temperatures of $20{\sim}25^{\circ}C$. The average number of eggs was $2,292{\pm}618$, with a diameter of $1.46{\pm}0.02\;mm$ for mature eggs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.511-519
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• 2017

In this study, we have performed tests to improve the productivity of hybrid solar stills, which can be operated by solar thermal energy and/or waste heat of exhaust gas from electrical generators. The experimental apparatus is a hybrid solar still with a $1m{\times}2m$ collecting area, which consists of a conventional simple solar still and a vertical multi-effect diffusion(MED) section. The experiments were conducted under various operating conditions, with two identical hybrid solar stills, using solar radiation as the energy source. The results of the tests showed that the yield of the hybrid solar still depends on the various operating conditions. Insulation at the side glasses and a lower basin seawater level increased the productivity of the hybrid solar still. Reflecting fins with less than 47% reflectivity unexpectedly decreased the total productivity. However, the various feeding flow rate of the seawater into MED part did not show clear effects on productivity in the tested range.

• Applied Microscopy
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• v.29 no.2
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• pp.177-187
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• 1999

Ultrastructure of gametes in the three-spine stickleback, Gasterosteus aculeatus aculeatus was observed, utilizing light, scanning and transmission electron microscopes. The egg of three-spine stickleback is spherical and demersal type. The eggs are highly adhesived to each other but not to substrates. There are many oil droplets in vitelline membrane. The outer surface of egg envelope is arranged by mushroom-like structures and pore canals. The egg have a micropyle, sperm entry site, in the area of the animal pole. The egg envelope consists of three layers, an outer layer with high electron density, a middle layer consisting two layers and an inner layer consisting of 16 to 20 layers. In the fertilized egg envelope, the molecular weights of these components ranged from 14 kDa to 205 kDa. The molecular weights of nam protein bands are 19.4 kDa, 36.7 KDa, 39.4 kDa, 42.9 kDa, 46.1 kDa and 53.0 kDa. The head of spermatozoa is spherical shape and the acrosome is absent. The mitochondria in midpiece are arranged from one to three layers and separated from the axoneme by the cytoplasmic canal. The tail has two lateral fins and the axoneme is of the 9+2 structure.

• Applied Microscopy
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• v.39 no.3
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• pp.227-236
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• 2009

The ultrastructure of spermatogenesis and sperm in Coreoleuciscus splendidus, belonging to Gobioninae, Cyprinidae was investigated by light and electron microscopes. The testis was located between intestine and air bladder. The size of testis was major axis 1.8 cm, minor axis 3 mm. The testis of C. splendidus contained numerous testicular cysts, and spermatogenesis was non-synchronized in these testicular cysts. In May, the upper area of testis contained with other germ cells and sperm but the lower area of testis contained with matured sperm only. In case of spermatogonia, the nucleus was comparatively large spherical, and mitochondria showed a marked development. The size of primary spermatocyte was smaller than that of spermatogonia, and that of secondary spermatocyte was smaller than that of primary spermatocyte. The chromatin of spermatocyte was highly condensed according to their development. The nucleus with electron-dense was round shape. In spermiogenesis, flagella started to be formed and chromatin was more condensed. The mitochondria were rearranged in a middle piece. The head of matured sperm was a spherical shape and had not acrosome. The microtubules of flagella were arranged 9+2 structure. Also, the tail of sperm had not lateral fins and 7 outer coarse fibers.

• Applied Microscopy
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• v.39 no.3
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• pp.219-226
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• 2009

The ultrastructure of spermatogenesis and sperm in Cichlasoma managuensis belonging to Cichlidae was investigated by light and electron microscopes. The testis of C. managuensis contained numerous testicular cysts, and spermatogenesis was synchronized in these testicular cysts. In the case of spermatogonia, the nucleus was comparatively large ellipsoidal, and mitochondria showed a marked development. The size of primary spermatocyte was smaller than that of spermatogonia, and that of secondary spermatocyte was smaller than that of primary spermatocyte. The chromatin of spermatocyte was highly condensed according to their development. The nucleus with electron-dense was round shape. In spermiogenesis, flagella started to be formed and chromatin was more condensed. The mitochondria were rearranged in a middle piece. The sperm was formed by loss of cytoplasm. The head of mature sperm was a spherical shape and had not acrosome. The microtubules of flagella were arranged 9+2 structure. Also, the tail of sperm have lateral fins.

• Restorative Dentistry and Endodontics
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• v.32 no.4
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• pp.335-342
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• 2007

C-shaped canals are known to present a complex canal anatomy with numerous fins connecting individual canals, thus requiring supplementary effort to accomplish a successful root canal treatment. This study examined the frequency of the C-shaped mandibular second molars and interrelation between the clinical records and radiographs to recognize them treated in the Department of Conservative Dentistry of the Chosun University Dental Hospital during a six-year period (1998-2004). This study reviewed the clinical records of 227 patients who underwent root canal treatment of the mandibular second molars. After opening the chamber, those cases with C-shaped orifices in the pulpal floor were selected, ana the C-shaped root canal types were classified according to Melton's criteria. Three experienced dentists evaluated the radiographs of the C-shaped mandibular second molar on a viewer using a magnifying glass in order to determine if the root apex was fused or separated, the distal root canal was either centered or mesial shifted in the distal root, and if there was bilateral symmetry in a panorama. In conclusion, there is a high frequency of C-shaped mandibular second molars in Koreans. Simultaneous interpretation of the root shape and distal root canal using the preoperative, working length and post-treatment radiographs is important for diagnosing a C-shaped mandibular second molar.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.915-924
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• 2014

In an aero gas-turbine engine, a surface air-oil heat exchanger (SAOHE) is used to cool the oil system for the gearboxes and electric generators. The SAOHE is installed inside the fan casing of the engine in order to dissipate the heat from the oil system into the bypass duct stream. The purpose of this study was to develop an effective numerical method for designing an SAOHE for an aero gas-turbine engine. A two-dimensional model using a porous medium was developed to evaluate the aero-thermal performance of the fins of the heat exchanger, and a one-dimensional flow and thermal network program was developed to save time and cost in the evaluation of the heat exchanger performance. Using this network program, the pressure drop and heat transfer performance of the heat exchanger were predicted, and the results were compared with two-dimensional computational fluid dynamics results and experiment data for validation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.79-86
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• 2017

In this study, the flow and heat transfer characteristics of the finned annular passage were investigated numerically. The annular passage simulates co-axial geothermal heat exchanger, and fins are installed on its inner wall to reduce heat loss from the production passage (annulus) to injection passage (inner pipe). A commercial CFD program, Ansys Fluent, was used with SST $k-{\omega}$ turbulence model. The effects of the geometric parameters of the fin on the inner tube were analyzed under the periodic boundary condition. The result indicated that most parameters had a tendency to increase with an increase in the height and angle of the fin. However, it was confirmed that the Nusselt number of the inner tube on the coaxial 15, 5, 0.3 was lower than that of the smooth tube. Additionally, the Nusselt number of the inner tube exhibited a tendency of decreasing with a decrease in the spacing in Coaxial 15, $S_f$, 0.3.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.339-345
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• 2008

The heat exchanger tube in nuclear power plants is mainly fabricated from nonferromagnetic material such as a copper, titanium, and inconel alloy, but the moisture separator & reheater tube in the turbine system is fabricated from ferromagnetic material such as a carbon steel or ferrite stainless steel which has a good mechanical properties in harsh environments of high pressure and temperature. Especially, the moisture separator & reheater tubes, which use steam as a heat transfer media, typically employ a tubing with integral fins to furnish higher heat transfer rates. The ferromagnetic tube typically shows superior properties in high pressure and temperature environments than a nonferromagnetic material, but can make a trouble during the normal operation of power plants because the ferrous tube has service-induced damage forms including a steam cutting, erosion, mechanical wear, stress corrosion cracking, etc. Therefore, nondestructive examination is periodically performed to evaluate the tube integrity. Now, the remote field testing(RFT) technique is one of the solution for examination of ferromagnetic tube because the conventional eddy current technique typically can not be applied to ferromagnetic tube such as a ferrite stainless steel due to the high electrical permeability of ferrous tube. In this study, we have designed RFT probes, calibration standards, artificial flaw specimen, and probe pusher-puller necessary for field application, and have successfully carry out RFT examination of the moisture separator & reheater tube of nuclear power plants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.34-44
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• 2016

This study is an experimental study about a facility for preventing the accumulation of floating debris at a bridge by flooding at a small river. Generally, structures installed at a small river are damaged frequently by floating debris during typhoons or localized rainfall events. On the other hand, there is no method available for preventing such damage. The facilities used in other countries to prevent such damage by the accumulation of floating debris include debris fins, deflectors, and sweeper. Among these facilities, the present study was conducted with a sweeper to investigate the damage-reducing capability through a real-scale accumulation experiment. A sweeper was installed in front of a bridge to bypass floating debris by self-rotation so that the floating debris may not be accumulate at the bridge. A small bridge model was prepared in a real-scale for the real-scale experiment. The accumulation reducing capability was compared through an accumulation experiment before and after the sweeper installation depending on the length of the debris and flow conditions. The result showed that the accumulation rate increased with increasing length of the debris or decreasing flow rate. The installation of a sweeper decreased the debris accumulation rate by a minimum of 55% to a maximum of 88% compared to the case without an installed sweeper. The result of the present study showed that the installation of a sweeper at a small river having a high potential of generating floating debris may help secure the stability of a bridge in the case of floating debris accumulation.