• Applied Science and Convergence Technology
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• v.23 no.2
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• pp.97-102
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• 2014

A vacuum chamber for a commercial atomic force microscope (AFM) is designed and fabricated. Only minimal modifications were made to an existing microscope in an effort to work in a vacuum environment, while most of the available AFM functionalities were kept intact. The optical alignment needed for proper AFM operations including a SLD (superluminescent diode) and a photodiode can be made externally without breaking the vacuum. A vacuum level of $5{\times}10^{-3}$ torr was achieved with a mechanical pump. An enhancement of the quality factor was observed along with a shift in the resonance frequency of a non-contact-mode cantilever in a vacuum. Topographical data of a calibration sample were also obtained in air and in a low vacuum using the non-contact mode and the results were compared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4178-4184
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• 2013

Nanoimprint lithography (NIL) is an emerging technology enabling cost-effective and high-throughput nanofabrication. Recently, the major trends of NIL are high throughput and large area patterning. UV curable type NIL (UV NIL) can be performed at room temperature and low pressure. And one advantage of UV NIL is that it does not need vacuum, which greatly simplifies tool construction, so that vacuum oprated high-precision stages and a large vacuum chamber are no longer needed. However, one key issue in non-vacuum environment is air bubble formation problem. Namely, can the air bubbles be completely removed from the resist. In this paper, the air bubbles formation by the method of droplet application in UV NIL with non-vacuum environment are experimentally studied. The effects of the volume of droplet and the number of dispensing points on air bubble formation are investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.635-640
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• 2015

In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator. Based on previous research, we try to increase the reliability of the proposed device by changing some components. It enables the proposed device to activate under high preload. Also, we confirm it generates low shock which is main advantage of non-explosive separation device. Finally, vibration test which mimics launching environment and thermal vacuum test which mimics space environment are carried out respectively. After each environment test, we confirm the proposed device is successfully activated. Conclusively, we develop a non-explosive separation device which can activate with low shock under high preload after shock and environment tests(vibration and thermal vacuum tests).

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.309-316
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• 2014

A large particle accelerator requires an ultrahigh vacuum (UHV) system of average pressure under $1{\times}10^{-7}$ Pa for mitigating the impact of beam scattering from the residual gas molecules. The surface inside the beam ducts should be controlled with an extremely low thermal outgassing rate under $1{\times}10^{-9}Pa{\cdot}m^3/(s{\cdot}m^2)$ for the sake of the insufficient pumping speed. To fulfil the requirements, the aluminum alloys were adopted as the materials of the beam ducts for large accelerator that thanks to the good features of higher thermal conductivity, non-radioactivity, non-magnetism, precise machining capability, et al. To put the aluminum into the large accelerator vacuum systems, several key technologies have been developed will be introduced. The concepts contain the precise computer numerical control (CNC) machining process for the large aluminum ducts and parts in pure alcohol and in an oil-free environment, surface cleaning with ozonized water, stringent welding process control manually or automatically to form a large sector of aluminum ducts, ex-situ baking process to reach UHV and sealed for transportation and installation, UHV pumping with the sputtering ion pumps and the non-evaporable getters (NEG), et al. The developed UHV technologies have been applied to the 3 GeV Taiwan Photon Source (TPS) and revealed good results as the expectation. The problems of leakage encountered during the assembling were most associated with the vacuum baking which result in the consequent trouble shootings and more times of baking. Then the installation of the well-sealed UHV systems is recommended.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.101-102
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm. The pressure of vacuum the range of 10^-4${\sim}$10^-5torr. The diameter of a plane made of the stainless steel is 150mm. As a result of the experiment, the breakdown voltage is increased about degree of vacuum increased. The electrode material influenced breakdown voltage in vacuum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.366-367
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm, 0.8mm. The pressure of vacuum the range of 10^-4-10^-5torr. The diameter of a plane made of the stainless steel is150mm. As a result of the experiment, the breakdown voltage is increased about electrode gap distance increased. The electrode material influenced breakdown voltage in vacuum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.915-920
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• 2013

Units developed for a real satellite should pass space environmental tests and launch environment tests. Thermal Vacuum Test, one of the space environmental test, simulates extreme thermal environment encountered in on-orbit operation of satellite. Many payloads which adapt non-traditional, brand-new technology are developed by developers who is not familiar to space engineering field. There might be some possibility of mistakes which result in serious problem due to lack of experience, especially from planning to performing thermal vacuum test. In this paper, brief overview of thermal environmental test related to a satellite development is summarized in order to prepare and perform the thermal test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.155-156
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• 2006

UV-NIL is a promising technology for the fabrication of sub-100 nm features. Due to non-uniformity of the residual layer thickness (RLT) and a strong possibility of defects, many UV-NIL processes have been developed and some are commercially available at present, most are based on the 'step-and-repeat' nanoimprint technique, which employs a small-area stamp, much smaller than the substrate. This is mainly because, when a large-area stamp is used, it is difficult to obtain acceptable uniform residual layer thickness and/or to avoid defects such as air entrapment. As an attempt to enable UV_NIL with a large-area stamp for high throughput, we propose a new UV-NIL tool that is able to imprint 4 inch wafer in a low vacuum environment at a single step.

• Archives of Plastic Surgery
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• v.32 no.6
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• pp.727-732
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• 2005

The treatment of wounds of the lower extremity caused by diabetes or vascular dysfunction remains a difficult problem for the plastic surgeon. The use of negative pressure in wound healing is a relatively new method to facilitate chronic wound healing by secondary healing. The use of vacuum-assisted closure(VAC) system is purposed to reduce local edema, increase regional blood flow, enhance epithelial migration, preserve a moist wound environment, reduce bacterial colonization, promote granulation tissue formation, and mechanically enhance wound closure. The VAC also can be used as a dressing for anchoring an applied split thickness skin graft. We reviewed the data from 20 consecutive patients with non-healing wound in lower extremity at Dong-A University from March 2002 to December 2004. We used the VAC in 20 patients and compared the results with the control group. In the VAC using group, mean application duration was about 3 weeks and dressing change was done every other day. The follow-up period of patients ranged from 3 months to 30 months with a mean of 17 months. The points of comparison with control group are wound size, granulation tissue proliferation rate, operation method, preoperative time, postoperative healing time, complication, and cost. With those points, we propose to approve the efficiency of the VAC in non-healing wound. As a result, the VAC used in non-healing wound decrease wound size, accelerate granulation tissue formation, do a wound closure with less invasive operation method, make less postoperative complication, can make operation time shorter. Therefore it is cost effect. Our results demonstrate the usefulness of VAC as an adjunct in management of chronic wounds with other extrinsic factors.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.90-98
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• 2022

The output of an infrared (IR) sensor mounted on an EO/IR payload is known to change during a mission period in an orbital environment. As it is required to calibrate the output of the IR sensor periodically to obtain high-quality images, an on-board black body system is mounted on the payload. All systems operating in the space environment require performance tests on ground to verify the target performance in the orbital environment. Therefore, it is also required to test the black body system to verify the performance of the surface temperature uniformity and the estimated representative temperature error within the target temperature range in the operating environment. In this study, calibration of the estimated representative temperature error and verification of the thermal performance of the black body system were conducted by performed a performance test in the thermal vacuum chamber applying deep space radiation cooling effect of an orbital environment.