• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.287-294
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• 2012

In the high vacuum condition of the space, outgassing from any assembly of satellite can contaminate satellites, especially second surface mirror and optical lens, it cause satellite to fail in own missions. Therefore, all unit shall be check for compatibility with vacuum using CVCM (Collected Volatile Condensable Material) and TML (Total Mass Loss) in advance. CVCM and TML of the PZT-5 piezoelectric ceramic vibrator has less than 0.1% and 1.0% respectively. Also, it has less than 500 $ng/cm^2/hr$ of Thermoelectric Quartz Crystal Microbalance for vacuum bake-out test using high temperature(more than $80^{\circ}C$) and high vacuum (less than $5.0{\times}10^{-3}$ Pa). Thus, piezoelectric ceramic vibrator may be employed in the vacuum environments. Finally, it can be confirmed that the characteristics change of the piezoelectric ceramic vibrator is less than 1% under vacuum environments.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.105-110
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• 2001

Autoclave curing using the vacuum bagging method is widely used for the manufacture of advanced composite prepreg airframe structures. Due to increasing use of advanced composites, specific techniques have been developed to repair damaged composite structures. In order to repair the damaged part, it is required that the damaged areas be removed, such as skin and/or honeycomb core, by utilizing the proper method and then repairing the area by laying up prepreg (and core) then curing under vacuum using the vacuum bagging materials. It shall be cured either in an oven or autoclave per the original specification requirements. Delamination can be observed in the sound areas during and/or after a couple times exposure to the elevated curing temperature due to the repeated repair condition. This study was conducted for checking the degree of degradation of properties of the cured parts and delamination between skin prepreg and honeycomb core. Specimens with glass honeycomb sandwich construction and glass/epoxy prepreg were prepared. The specimens were cured 1 to 5 times at $260^{circ}F$ in an autoclave and each additionally exposed 50, 100 and 150 hours in the $260^{circ}F$ oven. Each specimen was tested for tensile strength, compressive strength, flatwise tensile strength and interlaminar shear strength. To monitor the characteristics of the resin itself, the cured resin was tested using DMA and DSC. As a results, the decrease of Tg value were observed in the specific specimen which is exposed over 50 hrs at $260^{circ}F$. This means the change or degradative of resin properties is also related to the decrease of flatwise tensile properties. Accordingly, minimal exposure on the curing temperature is recommended for parts in order to prevent the delation and maintain the better condition.

• Journal of Biosystems Engineering
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• v.33 no.3
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• pp.179-185
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• 2008

The seeding rates of the vacuum suction nozzle seeders are affected by the jumping height of the seeds on the vibrating seed hopper. This study was performed to investigate the optimum vibration condition of the seed hopper on the vacuum suction nozzle seeder for improving seeding performance. Experiments were carried out to determine the vibration conditions of the seed hopper by air pressure and eccentric weight, and to optimize the seed-pickup performance of each nozzle by suction pressure. As the result with the experiments, the fluctuations of the jumping height of the seeds were showed at amplitude 0.4 mm and frequency 42 Hz, and jumping heights of the seeds were increased as the air pressure increase and the eccentric weight decrease, regardless number of seeds of the hopper. The best seeding rate of the seed hopper was 98% at the 300-seed cell, when the condition of the seed hopper was the suction air pressure of 94.6 kPa-abs., amplitude and frequency of the seed hopper vibration were at 0.57 mm and 43.6 Hz, respectively. The optimum vibrating conditions of the seed hopper were decided into frequency 43.6-43.8 Hz and the amplitudes 0.61-0.62 mm.

• Journal of IKEEE
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• v.22 no.2
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• pp.274-280
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• 2018

In this paper, we have developed the vacuum infusion automation system for the safety and quality advancement of the boat. It is necessary for the precise mixing rate of resinoid and curingagent to inject in an inner ship and deck at short time. We need for the optimal condition to a strengthen construction of boat. This one can solve the post deformability of the strengthen structure and can control the precise mixing rate of resinoid and curingagent to the resinoid fluidity and flowing rate per time. Under these condition, we can advance the an quality construction that based on the model and database information of the boat. Also, we can have an effective process management and retrench the production cost.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.163-176
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• 2012

Effective porosity has been measured for cement specimen as a function of vacuum time and pressure in the vacuum saturation process. Six cement specimen are used; three of them are made of the same ratio of cement and sand, the other three are 100% cement mortar, of which average porosity is about 25% and 40%, respectively. Using the 6 samples, measured effective porosities are compared and examined with 5 different vacuum pressures (2, 4, 6, 8, 10 torr) and times (20, 40, 60, 80, 100 minute), respectively. Comparing measured effective porosity from experiments when vacuum time varies from 100 minute to 20 minute with 20 minute step and vacuum pressure is fixed to 10, 6, and 2 torr, average deviation decreases as 0.6, 0.5, and 0.2% respectively. Comparing measured effective porosity from experiments when vacuum pressure varies from 2 torr to 10 torr with 2 torr step and vacuum time is fixed to 100, 60, and 20 minute, average deviation increases as vacuum time decreases. These results can be a background of suggested method of ISRM that describes the vacuum time longer than 60 minute and vacuum pressure higher than 6 torr. In this study, only qualitative discussion can be possible for the effects on the effective porosity by decreasing 20 minute vacuuming time at the same pressure or by decreasing 2 torr of vacuum pressure at the same vacuum time. This is because the sample could not reached to perfectly dried condition even though the sample were dried at $105^{\circ}C$ and following the ISRM suggested method, so that initial water content could not be the same at each experiment.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.57-58
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• 2002

Asperity arrays and Independent asperities were fabricated on a silicon plate. Then pull-off and friction forces were measured on each asperity pattern by using AFM (atomic force microscope) in humid air and high vacuum of $2{\times}10^{-5}$ Pa. The probe of AFM cantilever has a flat square of about $1\;{\mu}m^2$ on its tip. The results showed that the pull-off force was proportional to the curvature radius of asperity peak in each ambient condition. The friction force was proportional to the pull-off force and was slightly higher in the humid air than in the high vacuum.

• Food Science and Preservation
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• v.4 no.3
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• pp.259-264
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• 1997

To improve freshness of onion(Allium cepa), it was packed with various packaging films and stored at 5$^{\circ}C$ until 52 days. During the storage, internal gas composition, weight loss, spout ratio, decay ratio, surface color were determined. The used packaging films are two-perforated LDPE (control), LDPE, CPP/OPP/PE, Nylon/PE and Ag-zirconium filled LDPE. Onions were prepared by peeling or dipping in GFSE(grape fruit seed extract) and packed under vacuum or atmosphere with the selective films. Anaerobic condition was shown in the Nylon/PE package after 4 days and, thus weight loss, sprout ratio and color were considerably poor. All onions in the vacuum package after 15 days were spouted. Onions in CPP/OPP/PE and functional film(Ag-zirconium filled LDPE) package showed aerobic respiration until 52 days. Thus, the quality of onions in these packages was superior to the control.

• Journal of the Korean Mathematical Society
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• v.45 no.3
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• pp.645-681
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• 2008

The Navier-Stokes system for heat-conducting incompressible fluids is studied in a domain ${\Omega}{\subset}R^3$. The viscosity, heat conduction coefficients and specific heat at constant volume are allowed to depend smoothly on density and temperature. We prove local existence of the unique strong solution, provided the initial data satisfy a natural compatibility condition. For the strong regularity, we do not assume the positivity of initial density; it may vanish in an open subset (vacuum) of ${\Omega}$ or decay at infinity when ${\Omega}$ is unbounded.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.127-127
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• 2010

This study describes the optimal design of shield to improve the insulation performance of vacuum interrupter(VI). Axi-symmetric finite element routine including floating boundary condition for shields was applied to analyze electric potential and field distribution in VI. A ($\mu-\lambda$) Evolution Strategy(ES) is employed as optimization method. Three design variables of shield are selected for minimizing the maximum electric field strength in VI. Finally, optimal solution for shield is obtained and compared with the result of the prototype.

• Journal of Technologic Dentistry
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• v.32 no.4
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• pp.337-340
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• 2010

Purpose: This study was performed to compare sintering conditions for fabrication of porous Ti implant. Methods: The porous Ti implant samples were fabricated by sintering of spherical Ti powders in vacuum and atmosphere conditions. Surface morphology, composition and phase were analyzed by FE-SEM, EDX and XRD. Results: Sintered Ti implant in the vacuum consisted of particles connected in three dimensions by clear necking without excessive oxide layers. However, sintered Ti implant in atmosphere was formed excessive oxide layers with non-stoichiometric compounds. Conclusion: The porous Ti implant can be sintered in vacuum condition preferably.