• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.1-5
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• 2012

We investigate the exchange bias effect in $[Pd/Co]_5$ superlattice structures which are representative system of the perpendicular magnetic anisotropy. We fabricate Si/$[Pd/Co]_5$/FeMn structures, and study the exchange bias variations by measuring hysteresis loop variations with thickness of FeMn layer. In order to optimize the perpendicular magnetic anisotropy, we fix the thickness of Pd with 1.1 nm and investigate the dependence of the perpendicular magnetic anisotropy on the ferromagnetic Co layer thickness. As results, we find that the biggest coercivity in 0.3 nm of Co layer without FeMn layer. The biggest exchange bias field is found for 0.3 nm of Co layer when we change the Co thickness with fixed FeMn thickness. When we vary thickness of FeMn layer, the biggest coercivity is found for 5 nm of FeMn layer. No exchange bias is observed when the FeMn layer is thinner than 3 nm, and the exchange bias field increases with FeMn layer thickness continuously up to 15 nm.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.246-252
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• 2018

In this paper, the friction drag force of 3D submerged body is investigated by considering the surface roughness, the first grid height, and the Reynolds number using open CFD source code, OpenFOAM 4.0. A procedure for estimating drag components by CFD code is set up and suggested in this study. In the 3D submerged body, because of the form factor in the 3D computations, the friction resistance with the small roughness of $12{\mu}m$ obtains different result with the smooth wall. As the Reynolds number increased, the boundary layer becomes thinner and the fiction resistance tends to decrease. In the computations for the effect of y+, the friction resistance and wall shear stress are excessively predicted when the y+ value deviates from the log layer. This is presumably because the boundary layer becomes thicker and the turbulence energy is excessively predicted in the nose due to the increase in y+ value. As the roughness increases, the boundary layer becomes thicker and the turbulence kinetic energy on the surface increases. From this study, the drag estimation method, considering the roughness by numerical analysis for ships or offshore structures, can be provided by using the suggested the y+ value and surface roughness with wall function.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.293-294
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• 2011

It is known that semiconductor quantum-dot (QD) heterostructures have superior zero-dimensional quantum confinement, and they have been successfully applied to semiconductor laser diodes (QDLDs) for optical communication and infrared photodetectors (QDIPs) for thermal images [1]. The self-assembled QDs are normally formed at Stranski-Krastanov (S-K) growth mode utilizing the accumulated strain due to lattice-mismatch existing at heterointerfaces between QDs and cap layers. In order to increase the areal density and the number of stacks of QDs, recently, sub-monolayer (SML)-thick QDs (SQDs) with reduced strain were tried by equivalent thicknesses thinner than a wetting layer (WL) existing in conventional QDs (CQDs) by S-K mode. Despite that it is very different from CQDs with a well-defined WL, the SQD structure has been successfully applied to QDIP[2]. In this study, optical characteristics are investigated by using photoluminescence (PL) spectra taken from self-assembled InAs/GaAs QDs whose coverage are changing from submonolayer to a few monolayers. The QD structures were grown by using molecular beam epitaxy (MBE) on semi-insulating GaAs (100) substrates, and formed at a substrate temperature of 480$^{\circ}C$ followed by covering GaAs cap layer at 590$^{\circ}C$. We prepared six 10-period-stacked QD samples with different InAs coverages and thicknesses of GaAs spacer layers. In the QD coverage below WL thickness (~1.7 ML), the majority of SQDs with no WL coexisted with a small amount of CQDs with a WL, and multi-peak spectra changed to a single peak profile. A transition from SQDs to CQDs was found before and after a WL formation, and the sublevel of SQDs peaking at (1.32${\pm}$0.1) eV was much closer to the GaAs bandedge than that of CQDs (~1.2 eV). These revealed that QDs with no WL could be formed by near-ML coverage in InAs/GaAs system, and single-mode SQDs could be achieved by 1.5 ML just below WL that a strain field was entirely uniform.

• Polymer(Korea)
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• v.38 no.5
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• pp.640-644
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• 2014

As a process of plat panel display production, slot coating is widely used for the coating of photoresist on a wide glass substrate. A uniform coating thickness is important, and the coating uniformity is divided into nozzle and machine directions. The machine and nozzle directions coating uniformities are influenced by the operation condition of coater and flow uniformity inside the die, respectively. Non-uniform coating during steady coating process occurs according to those factors, however, non-uniform coating along the machine and nozzle directions has been observed at the beginning of coating by unsteady flow. In this study, steady and unsteady state flow simulations have been performed and compared with experiment to examine the causes of non-uniform coating. Computational results exhibited that it took a time to get a uniform pressure distribution at whole inside the die, and during this period of time edge regions showed lower exit velocity compared with center region. Subsequently edge regions had thinner coated layers than center region. However edge regions showed higher exit velocity than center region after steady state, and this made edge regions had thicker coated layer than center region.

• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.455-462
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• 1999

This study was designed to investigate the number of the growing and mature follicles in each stage of estrus cycle in mature rats. Eighteen mature rats(Sprague-Dawley, initially 190~230gm) were randomly alloted into 4 groups(proestrus, estrus, metestrus, and diestrus) according to estrus cycles. The uteri and ovaries of rats were collected and then alternative sections of paraffin embedding ovaries were stained with H-E. Numbers of large, middle and small follicles or only large and middle follicles from secondary and tertiary follicles were investigated by LM photography of preparations. Small follicles were defined as secondary follicles with 2~5 cell layers of granulosa cells surrounding the oocyte, and middle follicles were defined as secondary follicles with more than 5 cell layers or with early signs of antral cavity or with more than one small cleft on either side of the oocytes and large follicles were defined as tertiary follicles with a single medium or large antral cavity. The number of follicles in a pair ovary per rat was appeared to be ranged from 207 to 370 and the mean number of these follicles was $270.4{\pm}52.6$ and the mean number of follicles per ovary was $134.9{\pm}32.0$. The mean number of large, middle and small follicles per ovary was appeared to be $16.4{\pm}4.4$($12.2{\pm}3.3%$), $36.2{\pm}8.6$($26.8{\pm}6.4%$), and $82.7{\pm}24.0$($61.3{\pm}17.8%$), respectively. The mean number of large and middle follicles in each stage group of estrus cycle was appeared to be $17.8{\pm}2.1$ and $38.3{\pm}7.4$ at proestrus stage group, $15.7{\pm}5.2$ and $38.0{\pm}10.0$ at estrus stage group, $16.5{\pm}3.5$ and $33.8{\pm}7.0$ at metestrus stage group, $16.7{\pm}5.8$ and $29.7{\pm}5.5$ at diestrus group, respectively. In histological findings of large follicles during each estrus cycle, the large follicles in proestrus group contain single small antrum, thick granulosa cell layers, and were $300{\sim}500{\mu}m$ in diameter and were growing follicles with PCNA-positive cells in the granulosa cell layers, and other luteinizing follicles of proestrus cycle stage were decreased in size and were thicker in wall thickness and more luteinized than those in metestrus and diestrus stage groups. The large follicles in estrus stage group contain thick granulosa cell layers and nonprominent cumulus-oocyte complexes in antrum, and were $400{\sim}700{\mu}m$ in diameter and were growing follicles with PCNA-positive cells in the granulosa cell layers. The large follicles in metestrus and diestrus stage groups contain enlarged antrums, thinner layers of walls and prominent cumulus-oocyte complexes, and were $700-950{\mu}m$ in diameter, and were nongrowing follicles without PCNA-positive cells or another large follicles contain cells with dark stainability and distinct boundary.

• Korean Journal of Veterinary Research
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• v.45 no.2
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• pp.139-149
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• 2005

In order to study about the lobule and layer formation and cell migration of the mouse cerebellum from at the birth to 15th day effected by 2.5, 5 and 10 Gy r-raddiation at the 19th pregnancy. The routine tissue preparation and staining procedure, Immunohistochemical staining method by the several antibody and western brotting method were utilized from the birth to the15th day. The results were as followings. 1. The body and cerebellum weights were more slowly increase of the the 2.5 Gy, 5 Gy and 10 Gy irradiation group compare to the control group, and the health condition of the 2.5 Gy group was a little bad. but the 10 Gy group was more severe and begun to die from the 12th day after birth. 2. The thickness, proliferation and migration of the 2.5, 5 and 10 Gy irradiated external granular cells from the maginal zone to the medullary area forming the molecular layer from the 6th day to the 15th day after birth were thinner, weaker and more slower according to the radiated dosages than the control group in the cresyl violet staining. 3. The proliteration, migration and lobulation of the 5 Gy radiated groups from the first day to the 15th day after birth were more weak, incomplete and irregular shape in the immunostaining with Dab, Cdk5, P35, calbindin and Zebrin antibody. 4. In the western blotting analysis using the Reelin, Dab, Cdk5 and P35 antibody. The Bands were in the 60 KD, 80 KD, 33 KD and 35 KD, and there were no differences between the control and irradiated groups in the molecular band except the Reelin. 5. As a results, the proliferation and migration of the outer granular and purkinje cells, and lobulation of the cerebellum by the several dosaege of the ${\gamma}$-ray radiation were proportionally incomplete according to dosage.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.546-553
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• 1999

In Older to evaluate the effectiveness of 'One-bottle dentin adhesive system', the shear bond strengths of two fourth generation dentin adhesive systems and two One-bottle systems to the occlusal dentin of the freshly extracted third molars were measured by the regulation of the ISO TR 11405. The fourth generation dentin adhesive systems used in this study were Scotchbond Multi-Purpose Plus and All-Bond 2, and the One-bottle systems were Single Bond and One-Step. The effects of the thickness of hybrid layer and adhesive layer, the diameter of resin tag and the ratio between the diameter of resin tag and that of dentinal tubule were analyzed as the contributing factors of the shear bond strength of dentin bonding systems from the Scanning Electron Microscopic images. The results were as follows: 1. The shear bond strengths of Scotchbond Multi-Purpose, All-Bond 2, and Single Bond were 16.98${\pm}$3.40 MPa, 15.10${\pm}$2.77 MPa and 15.05${\pm}$3.18 MPa, respectively. There were no statistical differences(p>0.05). 2. But, the shear bond strength of One-Step were significantly lower than those of the other groups (11.81${\pm}$1.95 MPa, p<0.05). 3. The thicknesses of hybrid layer and adhesive layer of One-Step were significantly thinner than those of the other groups(p<0.05). The differences of the diameter of resin tag(p=0.0685) and the ratio between the diameter of resin tag and that of dentinal tubule(p=0.2401) were not significant among all the material groups. 4. The thickness of hybrid layer and adhesive layer might be considered as contributing factors of the she at bond strengths of dentin bonding systems, but the diameter of resin tag and the ratio between the diameter of resin tag and that of dentinal tubule might not.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.33-38
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• 2007

We studied a bonding at low temperature using polymer bump and Non-Conductive Adhesive (NCA), and studied the reliability of the polymer bump/Al pad joints. The polymer bumps were formed on oxidized Si substrates by photolithography process, and the thin film metals were formed on the polymer bumps using DC magnetron sputtering. The substrate used was AL metallized glass. The polymer bump and Al metallized glass substrates were joined together at $80^{\circ}C$ under various pressure. Two NCAs were applied during joining. Thermal cycling test ($0^{\circ}C-55^{\circ}C$, cycle/30 min) was carried out up to 2000 cycles to evaluate the reliability of the joints. The bondability was evaluated by measuring the contact resistance of the joints through the four point probe method, and the joints were observed by Scanning Electron Microscope (SEM). The contact resistance of the joints was $70-90m{\Omega}$ before the reliability test. The joints of the polymer bump/Al pad were damaged by NCA filler particles under pressure above 200 MPa. After reliability test, some joints were electrically failed since thinner metal layers deposited at the edge of bumps were disconnected.

• Korean Journal of Community Nutrition
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• v.8 no.5
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• pp.658-666
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• 2003

This study was carried out to investigate among adolescents (total=729) the relationship between their self-esteem, body-cathexis, their attitudes toward the importance of their bodies, their anthropometric characteristics, their perceptions of their body shapes and their experiences with weight control. The results are summarized as follows: The mean values for self-esteem and body-cathexis were generally low, but these values were significantly higher among boys than girls (p<0.01-0.001). However the mean values for their attitudes toward the importance of their bodies were relatively high and were significantly higher among girls than boys (p<0.01). The mean values for Percent Ideal Body Weight (PIBW) and Body Mass Index (BMI) were normal and no significant differences between the genders were observed. The distribution of the PIBW and the BMI values showed a higher rate for normal weights among the girls and a higher rate for underweightedness and obesity among the boys (p<0.01). With regard to their perception of their body image, among the boys, their current figures were almost identical with their idea of an ideal figure, but among the girls, their idea of an ideal figure was thinner than their current figure. The girls were more dissatisfied with their own body image than the boys (p<0.001). Fifty-four percent of the subjects had previous weight control experience, and the girls had significantly more experience than the boys (p<0.001). Their main reason for practising weight control was to lose weight (65.3%) Those who had more weight control experience had lower satisfaction with their body shapes, higher PIBW, higher BMIs or currently had fatter figures. Their standard image of their figures was influenced by TV (40.3%) and friends (36.9%). There was a weakly positive correlation between their self-esteem and their satisfaction with their body shapes, and a weakly negative correlation between their satisfaction with their body shapes and their attitudes toward the importance of their bodies. These results suggest the necessity for an educational program for adolescents as to foster a positive body image. Such a program should consider psychological factors such as self-esteem, satisfaction with body shape and attitudes toward the importance of the body.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.157-167
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• 2015

Cement composites subjected to high-velocity projectile shows local failure and it can be suppressed by improvement of flexural toughness with reinforcement of fiber. Therefore, researches on impact resistance performance of cement composites are in progress and a number of types of fiber reinforcement are being developed. Since bonding properties of fiber with matrix, specific surface area and numbers of fiber are different by fiber reinforcement type, mechanical properties of fiber reinforced cement composites and improvement of impact resistance performance need to be considered. In this study, improvement of flexural toughness and failure reduction effect by impact of high-velocity projectile have been evaluated according to fiber type by mixing steel fiber, polyamide, nylon and polyethylene which are have different shape and mechanical properties. As results, flexural toughness was improved by redistribution of stress and crack prevention with bridge effect of reinforced fibers, and scabbing by high-velocity impact was suppressed. Since it is possible to decrease scabbing limit thickness from impact energy, thickness can be thinner when it is applied to protection. Scabbing of steel fiber reinforced cement composites was occurred and it was observed that desquamation of partial fragment was suppressed by adhesion between fiber and matrix. Scabbing by high-velocity impact of synthetic fiber reinforced cement composites was decreased by microcrack, impact wave neutralization and energy dispersion with a large number of fibers.