• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.375-382
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• 2020

Owing to the rapid development of infrared guided weapon systems, the threat to aircraft survivability is constantly increasing, and research on infrared stealth technologies are being conducted to ensure aircraft survival. In this study, we analyze the minimum infrared signature of an aircraft according to its flight altitude by considering the characteristics of infrared guided missiles, which detect the contrast signature between the aircraft and background. We conducted computational fluid dynamics simulations for the convective coefficient, and heat transfer simulations were performed considering convection, conduction, and radiation for flight conditions. Thus, we obtained the surface temperature distribution of the aircraft and analyzed the aircraft infrared signature based on the flow characteristics around it. Furthermore, the optimum emissivity for the minimum infrared signature was derived, and the effect of the infrared signature was analyzed when this optimum emissivity was applied to the fuselage surface for each flight condition.

• Journal of Space Technology and Applications
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• v.1 no.3
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• pp.356-363
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• 2021

It was common knowledge in textbooks that images acquired using mid-infrared ray were not suitable for measuring temperature near room temperature. But a recent satellite image using a mid-infrared sensor show the possibility that the result measured using the mid-infrared sensor can also measure the temperature near room temperature. In this paper, the possibility and accuracy of extraction room temperature information from satellite images with mid-infrared sensors are reviewed. The mid-infrared satellite image reviewed in this paper showed the temperature of room temperature well, and regarding the reliability as an absolute value of the measured temperature, the effect of the heat transfer amount due to the direct reflection of sunlight on the surface and the effect of the infrared absorption amount absorbed in the atmosphere can be seen as a relatively small or constant value. However, the problem of uncertainty in the radiation coefficient due to physical properties, which is the limit of the non-contact thermometer, remained a problem to be solved.

• Advances in materials Research
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• v.13 no.3
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• pp.161-171
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• 2024

This study aimed to investigate the effect of physicochemical properties and mix ratios of iron ore (oxide feed): coke (reductant) on the carbothermic reductions of iron ore. Coke size was fixed at ≤63 ㎛ while iron ore size varied between 150-63 ㎛ and ≤63 ㎛ respectively. Mix ratios were changed from 100:0 (reference) to 80:20 and 60:40 while the temperature, heating rate and soaking duration in muffle furnace were fixed at 1100 ℃, 10 ℃/min and 1 hour. Particle size analyzer, XRF, CHNS and XRD analyses were used for determination of raw feed characteristics. The occurrence of phase transformations from various forms of iron oxides to iron during the carbothermal reductions were identified through XRD profiles and supported with weight loss (%). XRF analysis proved that iron ore is of high grade with 93.4% of Fe₂O₃ content. Other oxides present in minor amounts are 2% Al₂O₃ and 1.8% SiO₂ with negligible amounts of other compounds such as MnO, K₂O and CuO. Composite pellet with finer size iron particles (≤63 ㎛) and higher carbon content of 60:40 exhibited 45.13% weight lost compared to 32.30% and 3.88% respectively for 80:20 and 100:0 ratios. It is evident that reduction reactions can only occur with the presence of coke, the carbon supply. The small weight loss of 3.88% at 100:0 ratio occurs due to the removal of moisture and volatiles and oxidations of iron ore. Higher carbon supply at 60:40 leads into better heat and mass transfer and diffusivity during carbothermic reductions. Overall, finer particle size and higher carbon supply improves reactivity and gas-solid interactions resulting in increased reductions and phase transformations.

• Journal of Embryo Transfer
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• v.13 no.3
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• pp.277-289
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• 1998

To establish a system for sperm swim-up separation through sucrose layer, indiscreet sperm migration should sufficiently to block but movement of sperm shouldn't inhibit. Thus, the effects of sucrose levels in sucrose layer, incubation times and types of sucrose layer on sperm separation were examined. And the results obtained were as follows; 1. Layer of 10mM sucrose inhibited sperm swim-up migration through sucrose layer. 2. Incubation for 25 minutes without sucrose layer significantly increased sperm swim-up migration. However, incubation for 10 minutes to induce swim-up through sucrose layer significantly stimulated sperm migration and maintained sperm movement. 3. There was no significant difference between Type I and Type II in barrier effect of sucrose layer. However, sucrose layer of Type II with shorter distance of barrier was efficient for sampling. To elucidate a function of follicular fluid on sperm chemotaxis using in vitro system of sucrose layer of Type II and incubation for 10 minutes, the effects of dilution, heat treatment, and protein and lipid extracts of follicular fluid on sperm swim-up separation were examined. And the results obtained were as follows; 4. Follicular fluid stimulated sperm migration and movement, and significantly-attracted capacitated-sperm at 10% level. 5. Follicular fluid heated at 55$^{\circ}C$ for 30 minutes maintained the effect of follicular fluid stimulating sperm migration and movement. 6. Follicular protein stimulated sperm movement that was reduced by filtration of the protein. 7. Follicular lipid didn't significantly stimulate sperm migration and movement. 8. Both of follicular protein and lipid reduced the effect of follicular fluid stimulating sperm migration and movement. In conclusion, sucrose layer could be used for a barrier against indiscreet sperm migration by swim-up. And follicular fluid stimulated migration and movement of sperm and attracted capacitated-sperm through sucrose layer. Especially, heat-resistant protein of follicular fluid stimulated sperm migration.

• Journal of the Korea Institute of Building Construction
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• v.11 no.3
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• pp.256-264
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• 2011

By implementing an analysis on the liquid flame proof agent infiltration of microwave-heated wood under soaking conditions (room temperature soaking, heat soaking), its correlation with wood temperature, and the structure of wood and permeating components after soaking in flame proof agent, which was carried out as basic research in order to improve the fire resistance performance of the wood itself, it is found that the infiltration increases as the microwave heating time increases, while for heat soaking, it is found that high infiltration as well as the stable permeability of flame proof agent is achievable. Also, when the wood temperature is more than $80^{\circ}C$, the infiltration by the flame proof agent increased, and a very even infiltration of flame proof agent was observed, which implies that the liquid flame proof agent has a dependency on temperature change of the wood as a condition to penetrate into the wood. As a result of fine structure analysis, the flame proof agent transfer between cells through pits was considered as a cause to increase the infiltration of flame proof agent, and it is also shown that for heat soaking among the permeating component analysis, as the crystallized flame proof agent around the heartwood and sapwood inner pits increases, the flame proof agent can penetrate into the the heartwood part.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1419-1426
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• 2012

The heating and cooling energy load of the KNU plant factory was analyzed using the DesignBuilder. Indoor temperature set-point, LED supplemental lighting schedule, LED heat gain, and type of double skin window were selected as simulation parameters. For the cases without LED supplemental lighting, the proper growth temperature of lettuce $20^{\circ}C$ was selected as indoor temperature set-point together with $15^{\circ}C$ and $25^{\circ}C$. The annual heating and cooling loads which are required to maintain a constant indoor temperature were calculated for all the given temperatures. The cooling load was highest for $15^{\circ}C$ and heating load was highest for $25^{\circ}C$. For the cases with LED supplemental lighting, the heating load was decreased and the cooling load was 6 times higher than the case without LED. In addition, night time lighting schedule gave better result as compared to day time lighting schedule. To investigate the effect of window type on annual energy load, 5 different double skin window types were selected. As the U-value of double skin window decreases, the heating load decreases and the cooling load increases. To optimize the total energy consumption in the plant factory, it is required to set a proper indoor temperature for the selected plantation crop, to select a suitable window type depending on LED heat gain, and to apply passive and active energy saving technology.

• Journal of Embryo Transfer
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• v.33 no.3
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• pp.149-157
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• 2018

The objective of this study was to evaluate the effect of treating dairy cattle with exogenous human chorionic gonadotrophin (hCG), five (5) days post artificial insemination (AI) on serum progesterone (P4) concentration and pregnancy rate. In this experiment, five days after AI, cows were assigned randomly to two groups namely: a) treated group (67) which were administrered with 1500 IU hCG (Chorulon) and b) control group (61), which received no treatment. On day 5, 10, 15 and 20 after the artificial insemination, blood samples from a total of 8 cows (4 from each group) were collected and were analyzed for serum P4 concentration. Cows were detected for estrus according to standing heat by visual observation. Cows that were detected still in estrus after days 18-24 were re-inseminated and recorded as not pregnant (open). Pregnancy diagnosis was conducted by ultrasonographic examination and transrectal palpation of the uterus on approximately 60 days in cows that observed to be not in estrus. The conception rate in hCG treated and control groups were 52.5 and 36.1%, respectively. The results proved that there were no significant differences in conception rate between two groups (p=0.0568). However, pregnancy rates were reduced by hCG treatment. Average serum P4 concentrations did not differ between Hcg-treated and control groups on day 5 (0.377 versus 0.375 ng/ml). On day 20 serum P4 concentrations were greater in the treated group compared with the control group (3.085 versus 2.010 ng/ml). The treatment with hCG seemed to increase P4 level compared with the control. In conclusion, the results of this study showed that 1500 IU of hCG administered on 5 day post AI increased conception rate in dairy cows. This was supported by the results on serum P4 concentration which was greater in hCG treated group.

• Journal of Embryo Transfer
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• v.12 no.2
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• pp.181-188
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• 1997

This study was carried out to determine the effect of bovine follicular fluid(bFF), hormones, and fetal bovine serum(FBS) supplemented in the medium on the in vitro fertilization and development of bovine embryos. The ovaries were obtained from a local abattoir and placed in physiological saline kept at 30~32˚C and brought to the laboratory within 3~4 hours. The oocytes and follicular fluid were collected by aspiration from visible follicles, and the oocytes of grades I on the basis of the morphology of cumulus cells attached and the homogeneity of cytoplasmic granules were selected and used for maturation. The basal media used for oocyte maturation, fertilization and embryo development in vitro were Ham' F-10, TALP and TCM-199, respectively. The hormones supplemented in maturation medium were consisted of 35 pg /ml FSH, 10 pg /ml LH and 1 pg/mi estradiol-l7$\beta$. The bFF collected from 5~9 mm follicles was centrifuged, filtered and inactivated by heat-treatment at 56˚C for 30 min. FBS also was inactivated with the same method and kept at -20˚C until use. The embryos were co-cultured with the monolayer of bovine oviductal epithelial cells at 39˚C under 5% $CO_2$ in air for 9 days. The results obtained were summarized as follows: The fertilization rate of oocytes was found 87.4% from 10% FBS and hormones treatment for IVM, and 37.1% of these TVF embryos were developed to blastocyst stage in 10% FBS groups. Compared with this control system, the fertilization rate was decreased significantly(P<0.05) in the maturation without either FBS or hormones. These IVF embryos were developed to morula stage at the similar rate, but to blastocyst at significantly(P<0.05) lower rate in the embryo culture with or without FBS supplementation. The fertilization rate(82.9%) in hormones and 10% inactivated bFF was similar with 10% FBS and hormone groups(87.4%), but decreased significantly(P<0.05) in 20 or 30% bFF (61.0 or 66.0%), respectively. In vitro developmental competence to blastocyst stage in 10% FBS and 20% inactivated bFF(37.1% and 31.4%) was higher than in 10 or 30% inactivated bFF(20.0 or 19.2%) or 10, 20 and 30% fresh bFF(19.1, 21.0 and 17.5%) The results indicated that the in vitro fertillzation and development rate of the embryos should be improved in 10% FBS or 20% inactivated culture system and 20% inactivated bFF might be available economically for bovine oocyte maturation and embryo culture instead of fetal bovine serum.

• Journal of Adhesion and Interface
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• v.17 no.1
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• pp.15-20
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• 2016

Fiber arrangement was important for fiber reinforced thermoplastic composites using injection fabrication. In this work, fiber arrangement in CF/PP was investigated to use electrical resistance (ER) method during injection times. There were 3 types of injection products of CF/PP with different ER change ratio by fiber arrangement. High ER change ratio case of injection CF/PP products had better increased tensile strength. This reason was due to the fiber arrangement of CF/PP by injection. Fractured surface and contact angle of CF/PP products were used to evaluate for injection product quality. Uniform fiber arrangement of CF/PP by injection type exhibited the uniform heat condition of melted CF/PP. Steady thermal transfer effect occurred from melted CF/PP to steel injection mold. Steady thermal transfer effect of CF/PP was transmitted to high ER change ratio of mold. Ultimately, good condition CF/PP product by injection molding method could be predicted by using ER method.

• Polymer(Korea)
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• v.26 no.2
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• pp.260-269
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• 2002

The fire resistance of particulate polypropylene composite systems were investigated by using various reinforced particles such as zeolite, talc, $CaCO_3$ particles. In this study, The effect of particle size on the thermal properties of composite and the effect of reinforced particles on the fire resistance were studied. The inorganic reinforced particles used in this study were recycled zeolite(average particle diameter=85.34 $mu extrm{m}$), $CaCO_3$ (33.93 $mu extrm{m}$), and talc (18.51 $mu extrm{m}$). The fire resistance of composite systems was thoroughly examined by measuring limited oxygen index (LOI, ASTM D2863) and cone calorimetry (ASTM E1354, ISO 5660). Thermal stability of composite systems was thoroughly examined by measuring TGA. The flame retardants (DBDPO) and reinforced particles reduce the maximum heat release rate (M-HRR) in the order of Talc > $CaCO_3$ > recycled Zeolite. Comparing the cone calorimetry experimental results of the particle reinforced polymer composite system exhibited twice higher efficiency than DBDPO in polypropylene systems, and the LOI also showed similar trends to the cone calorimetry experiments. The optical and scanning electron microscopy techniques were used to investigate the composites ash layer and the core fracture surfaces in the burning process. The reinforcing inorganic particles seemed to accumulate at the surface of ash layer, and subsequently intercept the oxygen transport and heat transfer into the core area.