• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.06a
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• pp.160-173
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• 1997

Microstructure of hypereutectic Al-17wt.% Si alloy, fabricated by mechanical stirring and by reheating at semi-solid state, was investigated by optical microscope. Flow behavior semi-solid metal also was investigated at diffentent mould temperatures 280$^{\circ}C$, 290$^{\circ}C$ and 300$^{\circ}C$. Size of silicon particles were increased over 100$\mu\textrm{m}$ during solidification as a result of stirring. It is considered as microstructural coarsening by bonding between neighbouring primary silion particles during stirring of slurry. In case of reheating at semi-solid state, however, primary silicon particle was not increased at size of 40$\mu\textrm{m}$ and nearly spherical aluminum solde particle also could be obtained uniformly in distribution. The fludity of Al-17wt.% Si alloys at semi-solid state was improved when solid fraction was 0.7 at mould temperature of 300$^{\circ}C$ than other conditions.

• Korean journal of food and cookery science
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• v.9 no.2
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• pp.88-93
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• 1993

Semi-prepared frozen muscle foods purchased from local industry were tested for lipid oxidation. The effects of various storage conditions, cooking methods, defrosting methods and reheating methods on rancidity were examined using TBA assay and sensory evaluation. TBARS values were increased faster in cooked samples than in uncooked ones during storage periods. During refrigeration of cooked samples, TBARS values were increased significantly for 15 days (p<0.001). In defrosting experiments, refrigerated defrosting was proven to be better compared with room temperature or microwave defrosting (p<0.05). For overall explanation, stepwise regression analysis was done and the results are in this order: storage conditions, cooking methods, moisture content, and lipid content. Using these 4 variables, TBARS values could be explained by 40~53%.

• Korean journal of food and cookery science
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• v.13 no.5
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• pp.592-601
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• 1997

The purposes of this study were to develop Hazard Analysis Critical Control Point-based standardized recipe applicable to cook/chilled soy sauceglazed mackerel and to evaluate the qualities related to the product flow of this item. After conducting experimental cooking, preliminary test, and analysis of recipes, critical control points were identified, control methods were determined, and HACCP-based recipe was standardized. At each critical control point, time-temperature profile was recorded and microbiological analysis (total aerobic plate counts, psychrotrophic plate count, coliform, and fecal coliform count), chemical analysis (pH, acid value and volatile based nitrogen (VBN)) and sensory evaluation of the item were done. Time-temperature data showed that the time the menu item had passed through temperature danger zone (5∼60$^{\circ}C$) during all phases was 60 min. At rapid cooling, but after cooling at room temperature, the temperature of this menu item did not drop below the ambient temperature. The results of microbiological test were negative throughout all phases following cooking and the results of chemical analysis did not change significantly in terms of storage periods except for VBN which increased on 7th day significantly(p<0.05). After steam/convection oven reheating and microwave oven reheating, the sensory score of the only appearance decreased significantly related to the storage time of overall quality profiles. But significant differences were not detected according to two reheating methods. In conclusion, this HACCP-based recipe was considered as an effective tool for assuring microbial as well as sensory quality of this cook/chilled item.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.5
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• pp.267-274
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• 2001

Microalloyed steels, which substituted by conventional quenched and tempered steels, have been used in a wide variety of structural and engineering application. The main driving force for preference of MA steels is a cost reduction which can be achieved by an omission of heat treatment. In this study, low carbon martensitic MA steels in 0.18C-0.30(0.60)Si-2.00(1.80)Mn-0.05S-1.5Cr-0.05(0.10)V-0.015Ti(wt%) were investigated to know the effects of cooling method on the mechanical properties and microstructures of Si, Mn, V added microalloyed steel at different reheating temperature. Microstructure of oil quenched steels which were comprised lath martensite, auto-tempered martensite and retained austenite, had more various structure than that of air cooled steel made of mainly bainite. Therefore, oil quenched steels, which had more various microstructure, had better strength-toughness balance compare to air cooled steels. In the impact test, fracture mode of oil quenched steels, which showed good mechanical properties, were dimple, but that of air cooled steels were cleavage.

• Journal of the Korean Society of Food Culture
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• v.17 no.3
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• pp.315-328
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• 2002

The purpose of this study was to analyze the problems arising from the actual conditions of the Foodbank, and to implement the HACCP system as a solution in terms of increasing the safety of donated food within the Foodbank. In order to apply HACCP system, the entire Foodbank working process such as preparation, collection, transportation, division, and distribution was considered and analyzed to decide the application point for CCPs. Donated foods mainly consisted of processed foods, raw materials, lunch boxes, and cooked foods from mass catering establishments, which dominated over the others in terms of quantity. Cooked foods were divided into three groups based on menu-types and processing methods. Temperature, pH, and aw were measured on cooked foods, and Total Plate Count, Coliforms, E. coli, Salmonella spp., Staphylococcus aureus, Listeria monocytogenes, and E. coli O157:H7 were conducted in order to apply a HACCP plan. From these experiments, temperature, pH, and $a_w$ of donated food were likely contributed to microbial growth. Donated foods before HACCP implementation showed high numbers in terms of total plate count and Coliforms, both well over the acceptable standard levels. By setting the CCPs on maintenance of donated food below $10^{\circ}C$ and using a $75^{\circ}C$ reheating method, microbiological hazard levels were able to be controlled and lowered. From these results, it is concluded that in order to guarantee food safety, foods donated to the Foodbank must not only maintain a reasonable level of initial microbiological growth, but also must be handled properly through time and temperature controls within the Foodbank system. Furthermore, in terms of implementing the HACCP plan within the Foodbank management structure, basic food safety and sanitation measures, such as reheating facilities and various cold chain systems such as refrigerated vehicle for food transportation are importantly needed. The training and education of Foodbank personnel and management in areas such as awareness of hygiene and safe food handling and practice are also required and necessary.

• Journal of the Korean Society of Food Culture
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• v.11 no.4
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• pp.465-473
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• 1996

The purpose of this study was to evaluate microbiological hazards in the steps of production, transportation and selling of hamburger and sandwich that were marketed in CVS, then to identify methods of control. The reasults are as follows: As the reasult of operation surroundings of manufacturerand reserch of circulation, $4{\sim}6$ hours are needed from manufacturer to CVS. Also transportation car mean temperature was $10^{\circ}C$ which exceeds the standard of $7^{\circ}C$ or below. Hamburger: Critical control points identified were purchasing, cooking, post-preparation, transportation and holding at CVS. As the reasult of microbial analysis following the case of holding methods and reheating at CVS, microbes of cold holding and reheat after cold holding was within standard value. But in the case of room temperature microbes exceeded standard value. Sandwich: Critical control points identified were purchasing, cooking, post-preparation, transportation and holding at CVS. As the reasult of microbial analysis following the case of holding methods and reheating at CVS, total plate counts of cold holding and reheat after cold holding was within standard value. But in the case of room temperature holding after 24 hours total plate counts exceeded standard value. In the case of room temperature holding the number of microbes increased according to the passage of time. As a reasult of food poisoning bacteria, it was negative in every test in sample against V. parahaemolyticus, Salmonella, S. aureus.

• Journal of Korea Foundry Society
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• v.39 no.1
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• pp.7-13
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• 2019

Few studies of large blooms over 700 mm thick among those used for the forging of raw materials have been reported. The cooling rate difference between the surface and the center of a large bloom is large, and the degradation of the mechanical properties is likely in cases involving excessively coarse precipitates resulted from the slow cooling rate of a large bloom after casting. Therefore, a schematic investigation of the growth behaviors of precipitates while varying their locations in blooms is necessary. The dissolution behaviors of precipitates were investigated by simulating a reheating process during which the bloom is heated to a high temperature. The segregation behavior of the as-cast large bloom was also investigated. Reheating specimens were obtained after an isothermal heat treatment at $1150^{\circ}C$ with various holding times to simulate the reheating process, with the samples undergoing a subsequent water quenching step. The precipitates were extracted using an electrolytic extractor and a particle size analysis was conducted with the aid of SEM, EDS, and TEM. In the present work, Al oxide, MnS and Nb carbide were mainly observed.

• Composites Research
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• v.14 no.2
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• pp.33-42
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• 2001

The cure kinetic equation fur 52-glass/polyester prepreg composites was established through DSC (differential scanning calorimetry). Using the established kinetic equation, the temperature distribution of the thick composite was calculated considering the change of heat transfer resistance due to resin impregnation of bleeder plies used. In order to reduce the overheat during cure of thick glass fiber composites, the cure cycle was modified by introducing the cooling and reheating steps. Then the thick glass composites were cured both by the conventional cycle without any cooling or reheating step and the modified cure cycle. The mechanical properties of the thick composites cured by the both cycles were tested by the short beam shear test and the Barcol hardness test, and then their results were compared.

• Composites Research
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• v.13 no.4
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• pp.19-32
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• 2000

The fabrication process of particulate metal matrix composites(PMMCs) with homogeneous distribution of reinforcement and reheating for thixoforming has been studied. Both of eletro-magnetic stirring and mechanical stirring were used to fabricate particulate metal matrix composites(PMMCs) for variation of particle size. The electrical and mechanical processing conditions for fabricating PMMCs are also suggested. For thixoforming of PMMCs, fabricated bi1lets are reheated by using the designed optimal coil with as function of length between PMMC billet and coil surface, and coil diameter and billet. The effect of reinforcement distribution according to variation of billet temperature were investigated with solid fraction theory with a function of matrix alloy and volume fraction of reinforcement.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.941-952
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• 2017

Using the Generation of Thermal-Hydraulic Information for Containments (GOTHIC) code, thermal-hydraulic phenomena that occur inside the containment have been investigated, along with the preliminary design of the passive containment cooling system (PCCS) of an innovative pressurized water reactor (PWR). A GOTHIC containment model was constructed with reference to the design data of the Advanced Power Reactor 1400, and report related PCCS. The effects of the design parameters were evaluated for passive containment cooling tank (PCCT) geometry, PCCS heat exchanger (PCCX) location, and surface area. The analyzed results, obtained using the single PCCT, showed that repressurization and reheating phenomena had occurred. To resolve these problems, a coupled PCCT concept was suggested and was found to continually decrease the containment pressure and temperature without repressurization and reheating. If the installation level of the PCCX is higher than that of the PCCT, it may affect the PCCS performance. Additionally, it was confirmed that various means of increasing the external surface area of the PCCX, such as fins, could help improve the energy removal performance of the PCCS. To improve the PCCS design and investigate its performance, further studies are needed.