• Applied Science and Convergence Technology
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• v.24 no.5
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• pp.132-135
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• 2015

Schematic of RAON vacuum system is introduced. Vacuum test for superconducting cavity with liquid nitrogen is performed. Schematic plan for RAON vacuum system is introduced and vacuum control system for superconducting cavity test is constructed. Vacuum pressure of cavity is shown as a function of pumping time. The temperature of cavity is shown as a function of cooling time. Outgassing species from cavity is also detected. Detailed experimental procedure is presented to test the cavity vacuum with liquid nitrogen.

• ETRI Journal
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• v.38 no.4
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• pp.685-694
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• 2016

A surface micromachined piezoresistive pressure sensor with a novel internal substrate vacuum cavity was developed. The proposed internal substrate vacuum cavity is formed by selectively etching the silicon substrate under the sensing diaphragm. For the proposed cavity, a new fabrication process including a cavity side-wall formation, dry isotropic cavity etching, and cavity vacuum sealing was developed that is fully CMOS-compatible, low in cost, and reliable. The sensitivity of the fabricated pressure sensors is 2.80 mV/V/bar and 3.46 mV/V/bar for a rectangular and circular diaphragm, respectively, and the linearity is 0.39% and 0.16% for these two diaphragms. The temperature coefficient of the resistances of the polysilicon piezoresistor is 0.003% to 0.005% per degree of Celsius according to the sensor design. The temperature coefficient of the offset voltage at 1 atm is 0.0019 mV and 0.0051 mV per degree of Celsius for a rectangular and circular diaphragm, respectively. The measurement results demonstrate the feasibility of the proposed pressure sensor as a highly sensitive circuit-integrated pressure sensor.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.153-158
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• 2007

Molten metal flow in vacuum die casting was characterized by a numerical analysis. The VOF method was used to simulate the filling behaviors of molten metal during filling process. The various vacuum degrees of no vacuum(760 mmHg), 650, 500, 250 and 60mmHg were artificially applied in cavity. And the filling behaviors of molten metal with the applied vacuum conditions were simulated and compared with those of experiment. The results showed that molten metal was partially filled into cavity when vacuum was applied and the filling length of molten metal in cavity was increased with increasing applied reduced pressure in cavity. Also, the simulated filling behaviors of molten metal were apparently similar to those of experiment, indicating the numerical analysis developed in this study was highly effective. Through the result of fluid flow simulation, both relation equations of filling length and filling velocity with the variation of pressure conditions in cavity were calculated respectively and the internal gas contents of casting was significantly reduced by the modification of vacuum gate system.

• Journal of Korea Foundry Society
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• v.20 no.3
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• pp.181-187
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• 2000

There are two types of vacuum die casting, one is known as the chill block method, and the other is the valve block method. Efficiency of the valve block method is better than the chill block method. However purchasing and maintaining cost of the former one is very high, the latter method is popular in many small and medium die casting shops. Simple evacuation system using chill vent was prepared to investigate the effect of the air pressure, hose length and chill vent type on the pressure change in die cavity in this study. The rate of evacuation was influenced by the evacuation method, chill vent condition and hose length. Evacuation time became longer and vacuum level lower when evacuating cavity via chill vent. It took a longer time to evacuate the cavity when a longer hose was used. Vacuum level in the cavity also decreased with increase in hose length.

• Journal of Korean Vacuum Science & Technology
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• v.2 no.2
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• pp.57-62
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• 1998

The resonance frequencies, shunt impedances and Q-values for the higher-order modes in our designed cavity are calculated by the computer codes URMEL and MAFIA. A new computer code is developed to calculate the complex tune shifts for the randomness of the higher-order mode frequencies due to the construction errors of a cavity. The results with the construction errors are compared to those fo without error cases for the dipole mode and quadrupole mode.

• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.205-205
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• 1997

• Journal of Chest Surgery
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• v.53 no.4
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• pp.205-210
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• 2020

Esophageal anastomotic leak is the most common and serious complication following esophagectomy. However, the standard treatment for anastomotic leaks remains unclear. Recently, endoscopic vacuum therapy has become an important non-surgical alternative treatment method for patients with esophageal anastomotic leak. This treatment involves the endoscopic placement of a sponge connected to a nasogastric tube into the defect cavity or lumen. Subsequently, continuous negative pressure is delivered to the cavity through the tube. Several studies have reported a treatment success rate of 80% to 100%. In this study, we review the mechanism of action, the method of performing the procedure, its safety and efficacy, and prognostic factors for failure of endoscopic vacuum therapy in the management of patients with anastomotic leak, and on this basis attempted to confirm the possibility of establishing a standardized treatment protocol using endoscopic vacuum therapy.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.24-30
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• 2006

Integrated cavity output spectroscopy(ICOS) is a simple, non-intrusive absorption measurement technique that can detect and quantify trace-level gas species. The spectral absorbance of a gas is quantified from the integrated optical output of the modulated high-finesse cavity containing the sample which is irradiated by a wavelength-swept laser source. We constructed an experimental setup by using a tunable single mode external cavity diode laser operating at the wavelength near 765 nm and a Fabry-Perot cavity with length modulation achieved by a piezoelectric transducer where one of the cavity mirrors sat on. In the experiment performed on minute oxygen gas at the wave-length near 764.5nm, we demonstrated the minimum detectable absorption of $8.45\times10^{-8}cm^{-1}$.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• Journal of Chest Surgery
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• v.45 no.4
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• pp.260-262
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• 2012

Postpneumonectomy empyema is a life-threatening complication, which is often related with a bronchopleural fistula. After surgical repair of fistula, sterilization of infected pleural cavity is important and usually carried out by long-term cyclic irrigation. We report a case in which vacuum-assisted closure device was successfully applied to sterilize the pleural cavity and obliterate bronchopleural fistula.