• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.4 no.3
• /
• pp.183-188
• /
• 2003

Non-molding and welding line happen by the assembly of gas at the connector terminal. There is not good phenomenon of burr by increasing the over injection pressure, the temperatures of die and resin to prevent from them. Therefore, the connector mold to apply the vacuum molding system is developed in this study. The vacuum pressure is controlled systematically with the optimum conditions in the important ingredients of injection molding that are the temperatures of melting resin and die and cooling condition. The badness in charging is cleared by making a vacuum to non-charging part of the deep bottom part of each cavity. And the vacuum system to reduce the cycle time is applied as the study envelopment of molding work. So, the good product and the productivity improvement can be obtained in this study.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.6
• /
• pp.1341-1352
• /
• 2001

Vacuum freeze drying process by which frozen water in a drying material is removed sublimation under vacuum condition, is now applied to various industrial field such as the manufacturing and packaging of pharmaceuticals in pharmaceutical industry, the drying of bio- products in bio-technology industry, the treatment of various quality food stuff in food technology, and so on. The Knowledge about the heat and mass transfer characteristics related with the vacuum freeze drying process is crucial to improve the efficiency of the process as well as the quality of dried products. In spite of increasing needs for understanding of the process, the research efforts in this fields are still insufficient. In this paper, a numerical code that can predict primary drying in a vial is developed based on the finite volume method with a moving grid system. The calculation program can handle the axis- symmetric and multi-dimensional characteristics of heat and mass transfer of the vial freeze drying process. To demonstrated the usefulness of the present analysis, a practical freeze drying of skim Milk solution in a vial is simulated and various calculation results are presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.9
• /
• pp.441-446
• /
• 2014

In Jeju province, the Citrus is widely spread crop which is the most popular fruit on the island. When the quality of a Citrus is not in a good condition or when its size exceeds or is lower than the set criteria, it is discarded as a waste. In this study, a drying machine for waste Citrus has been developed with 2.6 GHz microwave energy supply to the Citrus at vacuum environment. The vacuum environment of the drying chamber was maintained to reduce the energy supply to the Citrus by lowering the evaporating temperature of the water. The experiment was conducted with variation of the vacuum pressure, interior temperature of the drying chamber, and operating time of the microwave. As a result, the effect of the temperature was shown to be higher than the other two control methods, and it showed with 0.305 g/W evaporation efficiency.

• Journal of Chest Surgery
• /
• v.39 no.9 s.266
• /
• pp.699-701
• /
• 2006

Mediastinitis and sternal wound infection frequently occurred after corrective surgery for complex heart anomalies. Most of the patients are neonate or infant and they have showed low oxygen tension. For that poor condition, application of invasive treatment of mediastinitis is not appropriate and recovery takes a long time. We successfully treated a mediastinitis after Norwood operation using vacuum assisted closure. So we introduce the technique and the modification of neonatal vacuum assisted closure.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.157-157
• /
• 2011

Graphene has generated significant interest in the recent years as a functional material for electronics, sensing, and energy applications due to its unique electrical, optical, and mechanical properties. Much of the considerable interest in graphene stems from results obtained for samples mechanically exfoliated from graphite. Practical applications, however, require reliable and well-controlled methods for fabrication of large area graphene films. Recently high quality graphene layers were fabricated using chemical vapor deposition (CVD) on nickel and copper with methane as the source of the carbon atoms. Here, we report a simple and efficient method to synthesize graphene layers using solid carbon source. Few-layer graphene films are grown using filtered vacuum arc source (FVAS) technique by evaporation of carbon atom on Ni catalytic metal and subsequent annealing of the samples at 800$^{\circ}$C. In our system, carbon atoms diffuse into the Ni metal layer at elevated temperatures followed by their segregation as graphene on the free surface during the cooling down step as the solubility of carbon in the metal decrease. For a given annealing condition and cooling rate, the number of graphene layers is easily controlled by changing the thickness of the initially evaporated amorphous carbon film. Based on the Raman analysis, the quality of graphene is comparable to other synthesis methods found in the literature, such as CVD and chemical methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.5
• /
• pp.466-473
• /
• 2011

The purpose of satellite thermal control design is to maintain all the elements of a spacecraft system within their temperature limits for all mission phases. The thermal analysis model for Low Earth Orbit satellite payload level simulation is established by considering thermal vacuum test environment condition, thermal vacuum chamber configuration, and satellite's payload inner thermal environment. The established thermal analysis model is used to determine thermal vacuum test conditions and test case requirements.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.6
• /
• pp.42-49
• /
• 2007

In this study, we analyzed flow characteristics of micro-nozzles for basic research to develop micro propulsion system. Cold gas propulsion system was used, and micro-nozzles having nozzle throat diameters of 1.0, 0.5, 0.25 mm were fabricated with EDM method. Thrust was measured through the use of plate-spring and strain gage based thrust measurement system, and flow characteristics of micro-nozzles were analyzed under ambient condition and vacuum condition. We used argon and nitrogen gases as propellant, and compared experimental results with CFD analysis. From the result, we verified the flow losses of viscosity and back-pressure caused by minimization of nozzle.

• Steel and Composite Structures
• /
• v.37 no.4
• /
• pp.419-429
• /
• 2020

Composite structures are generally pressurized at both sides when repaired by the scarf repair method. But single-face vacuum bag curing (SVC) may be used in some practical scarf repair of penetration damage due to the low accessibility of composite structures, which can decrease bonding quality and may reduce structural mechanical properties. In this paper, experimental investigations were conducted on tensile and compressive properties of scarf-repaired composite laminates using SVC and double-face vacuum bag curing (DVC) in four hygrothermal environments. Finite element models of composite scarf joints with voids were established to further explore the failure mechanism of scarf-repaired laminates. Results show that the curing condition hardly affects tensile and compressive properties of the repaired laminates though it significantly affects the bonding quality with adhesive inner voids. Failure loads of scarf joints almost keep unchanged with adhesive voids increasing.

• Journal of Surface Science and Engineering
• /
• v.53 no.2
• /
• pp.43-52
• /
• 2020

Various aging treatments were conducted on AISI 630 martensitic precipitation hardening stainless steel in order to optimize aging condition. Aging treatment was carried out in the vacuum chamber of Ar gas with changing aging temperature from 380℃ to 430℃ and aging time from 2h to 8h at 400℃. After obtaining the optimized aging condition, several nitrocarburizing treatments were done without and with the aging treatment. Nitrocarburizing was performed on the samples with a gas mixture of H₂, N₂ and CH₄ for 15 h at vacuum pressure of 4.0 Torr and discharge voltage of 400V. The corrosion resistance was improved noticeably by combined process of aging and nitrocarburizing treatment, which is attributed to higher chromium and nitrogen content in the passive layer, as confirmed by XPS analysis. The optimized condition is finalized as, 4h aging at 400℃ and then subsequent nitrocarburizing at 400℃ with 25% nitrogen and 4% methane gas for 15h at vacuum pressure of 4.0 Torr and discharge voltage of 400V, resulting in the surface hardness of around 1300 HV_0.05 and α'_N layer thickness of around 11 ㎛ respectively.

• Journal of Sensor Science and Technology
• /
• v.29 no.5
• /
• pp.354-359
• /
• 2020

The high vacuum hermetic sealing technique ensures excellent performance of MEMS resonators. For the high vacuum hermetic sealing, the customization of anodic bonding equipment was conducted for the glass/Si/glass triple-stack anodic bonding process. Figure 1 presents the schematic of the MEMS resonator with triple-stack high-vacuum anodic bonding. The anodic bonding process for vacuum sealing was performed with the chamber pressure lower than 5 × 10^-6 mbar, the piston pressure of 5 kN, and the applied voltage was 1 kV. The process temperature during anodic bonding was 400 ℃. To maintain the vacuum condition of the glass cavity, a getter material, such as a titanium thin film, was deposited. The getter materials was active at the 400 ℃ during the anodic bonding process. To read out the electrical signals from the Si resonator, a vertical feed-through was applied by using through glass via (TGV) which is formed by sandblasting technique of cap glass wafer. The aluminum electrodes was conformally deposited on the via-hole structure of cap glass. The TGV process provides reliable electrical interconnection between Si resonator and aluminum electrodes on the cap glass without leakage or electrical disconnection through the TGV. The fabricated MEMS resonator with proposed vacuum packaging using three-layer anodic bonding process has resonance frequency and quality factor of about 16 kHz and more than 40,000, respectively.