• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.49-55
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• 2018

Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.

• Applied Microscopy
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• v.23 no.2
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• pp.53-77
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• 1993

In this study, an attempt was made to investigate the probable organelles participating in the secretion of biligrafin. The animals (ICR male mice, 25-30gm) were divided into normal control and 6 biligrafin injected groups to which 30% biligrafin (0.006ml/gm b.w.) were injected at 10, 20, 40, 80, 160 and 320 min prior to the sampling. The mice of each group were perfused through the heart with ice-cold 2.5% glutaraldehyde buffered with 0.1M Na-cacodylate (pH. 7.4) under the Na-pentobarbital (Nembtal 0.0015mg/gm b.w.) anesthesia and liver tissues were taken from each group. Some specimens were immersed 1 hr in the same solution used in the perfusion. After an overnight rinse in 0.1M Na-cacodylate buffer containing 10% DMSO and 7.6% sucrose, $75{\mu}m$ fronzen sections were made for cytochemical study. The sections were incubated in thiamin pyrophosphatase (TPPase) and inosine diphosphatase (ID Pase) media for 70 min at $37^{\circ}C$ respectively and acid phosphatase (AcPase) medium for 40 min at $37^{\circ}C$. They were postfixed in 1 % $OsO_4$ for 1 hr. The other specimens were immersed for 8 hrs in the fixative consisting of 2.5% glutaraldehyde and 3.0% paraformaldehyde buffered with Na-cacodylate (pH. 7.4). All of the osmificated specimens were processed for electron microscopy. In both normal and biligrafin injected groups, endoplasmic reticulum (ER), vacuoles, Golgi apparatus and lysosomes were seen in the vicinity of bile canaliculus. In the biligrafin injected groups, however, the Golgi apparatus appeared to be decreased and ER and vacuoles were dilated and increased. The rough endoplasmic reticulum (RER) having a few attached ribosomes appeared to be the round saccule, especially at 20 min after biligrafin injection. Smooth endoplasmic reticulum (SER) seemed to be formed by the detachment of ribosomes at the cisternal end of RER. The cistern of SER showed saccules which probably budded off to form the vacuole. The vacuoles were devoid of visible centents. This finding seemed to be in agreement with the biochemical property of the bile constituents. The fusion between the vacuoles and bile canaliculus were frequently seen in the groups injected with biligrafin. The lysosome did not show any changes in the biligrafin injected groups. Accumulation of some material and lipid droplets were seen at the 40 and 80 min after biligrafin injection, especially at the latter. At 160 and 320 min after biligrafin injections, however, they were decreased successively while the RER stack, free ribosomes and polysomes were increased. Although the reactive products of TPPase and IDPase were observed in the ER saccules and vesicles of the normal control and biligrafin injected groups, the fusion between the bile canaliculus and saccules or vesicles could easily be seen in the latter. The AcPase activity, however, was observed in the cistern at the maturing face of Golgi apparatus and lysosomes in both normal and biligrafin groups. The results suggest that the biligrafin is excreted via the vesicles, vacuoles or sacoules probably derived from the SER without the participation of Golgi apparatus and lysosomes, and the excess amount of material is stored as inclusions during the repairing of the organelles being overactive.

• 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.29 no.1
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• pp.105-124
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• 1999

Histological and ultrastructural differentiations of the neuroepithelial cells in the mouse embryo during neurulation were observed. The neural plates and grooves consisted of pseudostratified columnar epithelium in the embryonic day (ED) 8 embryo were developed. In the ED 9 embryo, the neural tube was developed in all body length of embryo except both the cephalic and caudal ends. Secondary neurulation was shown at the tail bud of the ED 10 embryo. In the ED 8 embryo, the primitive streak was shown in the posterior end of the embryonic disc. The neuroepithelium, notochord and mesenchyme were well differentiated in the cephalic and cervical portions. In the ED 9 and 10 embryos, the roof plates of neural tubes were constituted of the closing of the surface ectodermal cells in the hindbrain and the neuroepithelial cells in the spinal cord. The floor plate of neural tube were consisted of the low pseudostratified columnar epithelium. The spinal motor nerve fibers were initially differentiated in the ED 10 embryo. According to the electron density of the cell and the differentiation of tell organelles, the neuroepithelial cells in the ED 9 and 10 embryos were classified into three types: dark, intermediate and light types. All types in the ED 9 embryo were observed but the dark cell in the ED 10 embryo was not done. The free ribosomes and polysomes in all neuroepithelial cells were developed. The RER and lipid droplets in the dark cell and the Golgi complex in the intermediate and light cells were observed. Many microfilaments in the cytoplasmic processes of intermediate cell and the microfilaments and microtubules in the light cell processes were observed to be well differentiated.

• Journal of Embryo Transfer
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• v.29 no.3
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• pp.201-206
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• 2014

The objectives of the study were to determine an effective culture dish, culture duration and protein supplementation in medium for in vitro maturation (IVM) of oocytes of native zebu cows in Bangladesh. The ovaries of cows were collected from local slaughterhouse followed by aspiration of follicular fluid. The cumulus-oocyte-complexes (COCs) with more than 3 compact cumulus cell layers were cultured in tissue culture medium (TCM) 199 for maturation. The maturation of oocytes was determined by observing polar body under microscope. To determine an effective culture dish, 130 COCs derived from 48 ovaries in a well of 4-well dish and 102 COCs derived from 36 ovaries in drops covered with mineral oil within 35 mm petri dish were cultured for 24 hours. The rate of maturation of oocytes did not vary between 4-well dish ($51.3{\pm}15.0%$) and drops in petri dish ($52.4{\pm}11.6%$). To determine the effective culture duration, 185 COCs derived from 62 ovaries were cultured in drops for 18, 21, 24 and 27 hours. The rate of maturation of occytes ranged from $51.9{\pm}9.4%$ (18 hours) to $59.0{\pm}17.1%$ (27 hours) and the difference in maturation rate among different culture durations was not significant (P>0.05). To determine an effective protein supplementation, 63 oocytes from 19 ovaries were cultured separately in TCM 199 supplemented with either fetal bovine serum (FBS) or bovine serum albumin (BSA). The rate of maturation was significantly (P<0.01) higher in medium supplemented with FBS ($55.63{\pm}16.19%$) than that of BSA ($14.82{\pm}9.36%$). In conclusion, COCs of native zebu cows can be cultured for IVM either in 4-well culture dish or droplets in petri dish for 18 to 27 hours in medium supplemented with FBS.

• Journal of Embryo Transfer
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• v.29 no.4
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• pp.397-401
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• 2014

The boar sperm has more lipid droplets and specialty of seminal plasma compared with other species, causing difficulties of freezing sperm and decreases for the utilization of frozen semen into the artificial insemination. However, several studies reported significant results for the recovery of sperm motility and reproductive by addition of cryoprotectants and seminal plasma after thawing. This study was designed to investigate the effects of supplementation of trehalose or glycerol in the LEY (lactose and egg yolk in BTS) solution for the conventional freezing and vitrification process. Two boars aged 16 months were used to collect semen for 2 times in a week. The samples were allotted to 3 freezing solutions (LEY + glycerol 10.5% + OEP 1.5%, LEY + trehalose 1M + OEP 1.5%, and sucrose 1.5M + trehalose 1 M + OEP 1.5%) after centrifugation at 800 g for 10 minutes. Semen was equilibrated in freezing solutions for 10 minutes and injected into plastic straws with 2~3 air bubbles to minimize freezing damages. Vitrification was performed to locate sperm in 5 cm above $LN_2$ for 5 minutes, and the conventional freezing was conducted with an automatic freezer. Motility and survival rates were measured by CASA (Computer assisted sperm an alyzing system) and FITC (Fluorescein isothiocyanate), respectively after thawing semen at $50^{\circ}C$ for 12 seconds. The results were analyzed by ANOVA with STATVIEW statistical program. The vitrificatioin solution (LEY + 10.5% glycerol + 1.5% OEP) presented higher motility (20.9%) than other solutions while the solution (LEY + 1M trehalose + 1.5% OEP) showed the lowest (motility : 5.2%). However, survival rates of vitrified sperms detected by FITC showed 1~4% live sperms in almost of dead sperms at all vitrification solutions' groups, but survival rate of freezing solution of LEY + 1M trehalose + 1.5% OEP LEY and LEY + 10.5% glycerol + 1.5% OEP were showed 49%, and 79%, respectively. There were differences (P<0.05) survival rate of conventional freezing in LEY + 10.5% glycerol + 1.5% OEP and LEY + 1M trehalose + 1.5% OEP and the remaining showed no differences. The results suggested that vitrified boar semen was not enough to be utilized for the artificial insemination, but it showed possibility to utilize for ICSI and conventional freezing with glycerol would be useful method for artificial insemination in pig while we choose the outstanding semen against tolerance to freezing damages.

• Restorative Dentistry and Endodontics
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• v.35 no.5
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• pp.321-334
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• 2010

Objectives: The purpose of this study is to evaluate bonding efficacy by means of measuring the effect of remained solvent on Degree of conversion(DC) and ${\mu}TBS$ and FE-SEM examination. Materials and Methods: Two 2-step total etching adhesives and two single-step self etching adhesives were used in this study. First, volume weight loss of 4 dentin adhesives were measured using weighting machine in process of time in normal conditions and calculate degree of evaporation (DE). Reaction/reference intensity ratio were measured using micro-Raman spectroscopy and calculate DC according to DE. Then 2 experimental groups were prepared according to air-drying methods (under, over) and control group was prepared to manufacturer's instruction. Total 12 groups were evaluated by means of micro tensile bond strength and FE-SEM examination. Results: Degree of evaporation (DE) was increased as time elapsed but different features were observed according to the kind of solvents. Acetone based adhesive showed higher DE than ethanol and butanol based adhesive. Degree of conversion (DC) was increased according to DE except for $S^3$ bond. In ${\mu}TBS$ evaluation, bond strength was increased by additional air-drying. Large gaps and droplets were observed in acetone based adhesives by FE-SEM pictures. Conclusions: Additional air-drying is recommended for single-step self etching adhesive but careful consideration is required for 2-step total etching adhesive because of oxygen inhibition layer. Evaporation method is carefully chose and applied according to the solvent type.

• Resources Recycling
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• v.26 no.1
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• pp.22-29
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• 2017

When the ambient air pressure was $0.1kg/cm^2$, there were few spherically formed droplets, which showed very badly fragmented state. The average particle size of the particles constituting the droplet was about 40 nm. When the air pressure increased to $0.5kg/cm^2$, the ratio of the spherical droplet forms increased, but still showed a state of severe disruption. The average particle size of the particles was reduced to about 35 nm. As the air pressure increased to $3kg/cm^2$, the ratio of spherical droplet form significantly increased, the degree of fragmentation even further decreased and the average particle size decreased to 30 nm. When the air pressure increased from 0.1 to $1kg/cm^2$, the XRD peak intensity showed little change, but the specific surface area was decreased. As the air pressure increased to $3kg/cm^2$, the intensity of XRD peaks showed a little decrease, while the specific surface area increased.

• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.665-672
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• 2018

A venturi scrubber is an important element of Filtered Containment Venting System (FCVS) for the removal of aerosols in contaminated air. The present work involves computational fluid dynamics (CFD) study of dust particle removal efficiency of a venturi scrubber operating in self-priming mode using ANSYS CFX. Titanium oxide ($TiO_2$) particles having sizes of 1 micron have been taken as dust particles. CFD methodology to simulate the venturi scrubber has been first developed. The cascade atomization and breakup (CAB) model has been used to predict deformation of water droplets, whereas the Eulerian-Lagrangian approach has been used to handle multiphase flow involving air, dust, and water. The developed methodology has been applied to simulate venturi scrubber geometry taken from the literature. Dust particle removal efficiency has been calculated for forced feed operation of venturi scrubber and found to be in good agreement with the results available in the literature. In the second part, venturi scrubber along with a tank has been modeled in CFX, and transient simulations have been performed to study self-priming phenomenon. Self-priming has been observed by plotting the velocity vector fields of water. Suction of water in the venturi scrubber occurred due to the difference between static pressure in the venturi scrubber and the hydrostatic pressure of water inside the tank. Dust particle removal efficiency has been calculated for inlet air velocities of 1 m/s and 3 m/s. It has been observed that removal efficiency is higher in case of higher inlet air velocity.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.634-638
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• 2011

We report growth of epitaxial AlN thin films on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. To achieve two-dimensional growth the substrates were nitrided by nitrogen plasma prior to the AlN growth, which resulted in the formation of a two-dimensional single crystalline AlN layer. The formation of the two-dimensional AlN layer by the nitridation process was confirmed by the observation of streaky reflection high energy electron diffraction (RHEED) patterns. The growth of AlN thin films was performed on the nitrided AlN layer by changing the Al beam flux with the fixed nitrogen flux at 860$^{\circ}C$. The growth mode of AlN films was also affected by the beam flux. By increasing the Al beam flux, two-dimensional growth of AlN films was favored, and a very flat surface with a root mean square roughness of 0.196 nm (for the 2 ${\mu}m$ ${\times}$ 2 ${\mu}m$ area) was obtained. Interestingly, additional diffraction lines were observed for the two-dimensionally grown AlN films, which were probably caused by the Al adlayer, which was similar to a report of Ga adlayer in the two-dimensional growth of GaN. Al droplets were observed in the sample grown with a higher Al beam flux after cooling to room temperature, which resulted from the excessive Al flux.