• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.2
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• pp.185-192
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• 2017

In this paper, we reviewed major design parameters for a solid type of deployable antenna and its structural design. We performed modal analysis for a single reflector panel made of aluminum and CFRP (carbon fiber reinforced plastic) to confirm the appropriateness of selected materials. We then predicted the elastic modulus of CFRP using the principles of unidirectional composite elasticity stiffness predictions such as the ROM (Rule of Mixture) and HSR (Hart Smith 10% Rule). To optimize the shape of the antenna reflector, a structural stiffness analysis was performed using derived numerical optimization factors. Six structural stiffness analyses were performed using the constructed experimental design method. The resulting optimal shape conditions are proposed to meet the structural stiffness requirements while minimizing weight.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.181-185
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• 2010

The behavior of combustion-induced internal flow of SRM equipped with fin-slot grain and submerged nozzle is very complex and diverse. Cold air-flow test for 2D and 3D scale models of SRM has been done in order to specify the visualization method to analyze particular internal flow patterns such as roll-torque inducing flow. Swirl flow induced by asymmetric vortical tube also has been visualized through employing various light source and recording directions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.4
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• pp.399-410
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• 2022

The solubility and species distribution of radionuclides in groundwater are essential data for the safety assessment of deep underground spent nuclear fuel (SNF) disposal systems. Americium is a major radionuclide responsible for the long-term radiotoxicity of SNF. In this study, the solubility of americium compounds was evaluated in synthetic groundwater (SynDB3), simulating groundwater from the DB3 site of the KAERI Underground Research Tunnel. Geochemical modeling was performed using the ThermoChimie_11a thermochemical database. Concentration of dissolved Am(III) in Syn-DB3 in the pH range of 6.4-10.5 was experimentally measured under over-saturation conditions by liquid scintillation counting over 70 d. The absorption spectra recorded for the same period suggest that Am(III) colloidal particles formed initially followed by rapid precipitation within 2 d. In the pH range of 7.5-10.5, the concentration of dissolved Am(III) converged to approximately 2×10^-7 M over 70 d, which is comparable to that of the amorphous AmCO₃OH(am) according to the modeling results. As the samples were aged for 70 d, a slow equilibrium process occurred between the solid and solution phases. There was no indication of transformation of the amorphous phase into the crystalline phase during the observation period.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.869-878
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• 2001

Alumina $(Al_2O_3)$ green bodies were fabricated by gel-casting using three kinds of alumina with different particle size (mean particle size: 4.6 $\mu\textrm{m}$, 0.32 $\mu\textrm{m}$, 10nm). The effects of particle size on gel-casting process and green microstructure were investigated. The optimum dispersion conditions using ammonium salt (D-3019) as dispersant were 0.2 wt% (4.63 $\mu\textrm{m}$), 0.5 wt% (0.32 $\mu\textrm{m}$), and 5.0 wt% (10 nm), in high solid loading. The optimum solid loading of each starting material for gel-casting was obtained as 59 vol% (4.63 $\mu\textrm{m}$), 57 vol% (0.32 $\mu\textrm{m}$), 15 vol% (10 nm), depending on particle size, indicating that nano-size particle (10 nm) represent lower solid loading as high specific surface area than those of other two starting materials. The drying at ambient conditions (humidity; $\thickapprox$90%) was performed more than 48hrs to enable ejection of the part from the mold and then at $120^{\circ}C$ for 2hrs in an air oven, showing no crack and flaw in the dried green bodies. The pore size and distribution of the gelcast green bodies showed the significant decrease with decreasing particle size. Green microstructure was dependent on the pore size and distribution due to the particle size, and on the deairing step. The green density maximum obtained was 58.9% (4.63 $\mu\textrm{m}$), 60% (0.32 $\mu\textrm{m}$), 47% (10 nm) theoretical density (TD), and the deairing step applied before gel-casting did not affect green density.

• Journal of Welding and Joining
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• v.31 no.1
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• pp.58-64
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• 2013

The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1235-1244
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• 1994

In this study, experimental results of the nucleate boling of wire-wrapped tubes are provided. Both water and R-113 were boiled. Solid stainless steel wires, stranded copper wires and stranded nylon wires were tested. Solid stainless wire is effective to enhance the boiling of water. The performance is approximately the same(or slightly better at certain conditions) as that of GEWA-T tubes. For the test range of wire diameter 0.6 $mm{\le}d{\le}2.6 mm$, the optimum gap width increases as the wire diameter increases. The maximum heat transfer coefficient was obtained for the 1.0 mm diameter wire, and it is 1.6 times larger than that of the GEWA-T at the heat flux of 20 $kW/m^{2}.$ Solid stainless wire is also effective to enhance the boling of R-113 at low heat fluxes. The performance of the wire-wrapped tube approaches that of GEWA-T. At high heat fluxes, however, the enhancement decreases. The reason may be attributed to the cavity shape and the high wettability of the refrigerants. Stranded copper or nylon wire is effective to enhance the boiling of R-113. The performance is approximately the same(or slightly better) as that of GEWA-T tubes. Maximum heat transfer was obtained for the stranded nylon wire, and it is approximately 1.4 times larger than that for the GEWA-T at the heat flux of 20 $kW/m^{2}.$ The reason may be atrributed to the favorable thermal environment in the restricted regions formed by twisted wires.

• Journal of Animal Science and Technology
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• v.58 no.10
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• pp.36.1-36.5
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• 2016

Background: Liquid feeding system has been introduced to domestic swine farms, but negative cognition about liquid feeding system has been remained for feed waste decay related with poor management and microbial contamination. For these reasons, this study was conducted to evaluate the effects of feeding method in lactating sows. Methods: A total of 30 mixed-parity (average 4.13) lactating sows (Yorkshire ${\times}$ Landrace) with an initial BW of $218.8{\pm}19.5kg$ was used in a 3 week trial. Sows were allotted to 1 of 2 treatments in a completely randomized design by their body weight, backfat thickness, parity and alive litter weight. One of treatments was dry feeding and the other was liquid feeding (water to feed ratio, 1:1). Experimental diets contained 3265 kcal ME/kg, 12.6 % CP, 5.76 % EE, 1.09 % total lysine, 0.25 % total methionine, as fed basis. Results: Dry feeding treatment had high body weight loss rather than liquid feeding treatment (P = 0.04). Dry feeding treatment had tendency to increase litter weight at 21d of lactation (P = 0.06) and litter weight gain (P = 0.04) during lactation period (0-3 week). Sows fed dry feeding method made milk containing high content of casein and total solid rather than sows fed liquid feeding method (P = 0.04). In addition, dry feeding treatment had tendency to higher content of milk fat, protein and solid not fat on 21d of lactation (P = 0.07). Sows fed dry feeding type also showed higher milk energy content in milk of 21d lactation (P = 0.05). Furthermore, liquid feeding treatment showed high occurrence in feed waste during lactation period (P <0.01). Conclusion: Dry feeding method was more suitable feeding method to lactating sows under high temperature environment like lactating barn.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.869-874
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• 2014

It is possible to fabricate a three-dimensional (3D) shape using the solid freeform fabrication (SFF) technology. However, there are several problems in applying conventional SFF technologies to the direct manufacturing of a product. Hence, multimaterial SFF is gaining attention. Moreover, a 3D circuit device that is different from a conventional two-dimensional PCB can also be fabricated using multimaterial SFF. In this study, a hybrid system using fused deposition modeling and direct writing was designed for 3D circuit device fabrication.

• Advances in pediatric surgery
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• v.2 no.2
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• pp.94-99
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• 1996

The management of twenty-two children with blunt abdominal trauma was analyzed. Nineteen cases had intraabdominal injuries; involving the spleen in 7 cases, the liver in 5, the pancreas in one and the bladder in one. There were five case multiple intraabdominal organ injuries. Seventeen out of 19 patients were treated non-operatively, but one was operated upon later because of delayed bleeding. Thirteen patients required transfusion in the non operated group, the mean values of the Pediatric Trauma Score (PTS) was 11.3. The mean lowest hemoglobulin(LHb) was 9.1 g/dL. The mean value of three cases with extraabdominal injuries were 9.0 and 8.3 g/dL respectively. The average amount of transfusion was 17.3 ml/kg. In the operated group, 2 cases were transfused an average of 139.8 ml/kg and their mean PTS was 5 and LHb was 6.6 g/dL. In one out of 16 non-operated cases, intrahepatic hematoma developed and but resolved conservatively. However, two out of 3 operated cases suffer complications such as an intubation granuloma and an intraabdominal abscess with wound dehescence. In conclusion, non-operative management in child with blunt abdominal trauma was safe in Grade I and II solid organ injuries. The decision for operation should be based on the hemodynamic stability after initial resuscitation including transfusion.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.79-87
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• 2021

In this study, we developed a method to predict/analyze the performance of a dual thrust rocket motor that has 2 kinds propellant charged in axial direction. When transitioning from the booster to the suspender stage, a transient phenomenon related to performance occurred at the interface. The causes and characteristics of the transient phenomenon were investigated by comparing them with the results of the combustion test. It was confirmed that the performance transient phenomenon is sensitively generated not only by the shape design between the propellants with different properties of the propellant, but also by errors in manufacturing due to the propellant curing shrinkage.