• Tribology and Lubricants
• /
• v.38 no.4
• /
• pp.121-127
• /
• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.

• Radiation Oncology Journal
• /
• v.19 no.3
• /
• pp.275-286
• /
• 2001

Purpose : To setup procedures of quality assurance (OA) for implementing intensity modulated radiation therapy (IMRT) clinically, report OA procedures peformed for one patient with prostate cancer. Materials and methods : $P^3IMRT$ (ADAC) and linear accelerator (Siemens) with multileaf collimator are used to implement IMRT. At first, the positional accuracy, reproducibility of MLC, and leaf transmission factor were evaluated. RTP commissioning was peformed again to consider small field effect. After RTP recommissioning, a test plan of a C-shaped PTV was made using 9 intensity modulated beams, and the calculated isocenter dose was compared with the measured one in solid water phantom. As a patient-specific IMRT QA, one patient with prostate cancer was planned using 6 beams of total 74 segmented fields. The same beams were used to recalculate dose in a solid water phantom. Dose of these beams were measured with a 0.015 cc micro-ionization chamber, a diode detector, films, and an array detector and compared with calculated one. Results : The positioning accuracy of MLC was about 1 mm, and the reproducibility was around 0.5 mm. For leaf transmission factor for 10 MV photon beams, interleaf leakage was measured $1.9\%$ and midleaf leakage $0.9\%$ relative to $10\times\;cm^2$ open filed. Penumbra measured with film, diode detector, microionization chamber, and conventional 0.125 cc chamber showed that $80\~20\%$ penumbra width measured with a 0.125 cc chamber was 2 mm larger than that of film, which means a 0.125 cc ionization chamber was unacceptable for measuring small field such like 0.5 cm beamlet. After RTP recommissioning, the discrepancy between the measured and calculated dose profile for a small field of $1\times1\;cm^2$ size was less than $2\%$. The isocenter dose of the test plan of C-shaped PTV was measured two times with micro-ionization chamber in solid phantom showed that the errors upto $12\%$ for individual beam, but total dose delivered were agreed with the calculated within $2\%$. The transverse dose distribution measured with EC-L film was agreed with the calculated one in general. The isocenter dose for the patient measured in solid phantom was agreed within $1.5\%$. On-axis dose profiles of each individual beam at the position of the central leaf measured with film and array detector were found that at out-of-the-field region, the calculated dose underestimates about $2\%$, at inside-the-field the measured one was agreed within $3\%$, except some position. Conclusion : It is necessary more tight quality control of MLC for IMRT relative to conventional large field treatment and to develop QA procedures to check intensity pattern more efficiently. At the conclusion, we did setup an appropriate QA procedures for IMRT by a series of verifications including the measurement of absolute dose at the isocenter with a micro-ionization chamber, film dosimetry for verifying intensity pattern, and another measurement with an array detector for comparing off-axis dose profile.

• Journal of Wetlands Research
• /
• v.25 no.3
• /
• pp.176-183
• /
• 2023

The aim of this paper is to understand the blade number effect on vortex turbine performance in the cylindrical vortex chamber below the free water surface. Using the same blade profile, the performance of gravitational vortex turbine is tested each with 2, 3, 4, 5 and 6 blades installed at the relative vortex height (y/h_v) ranging from 0.065 to 0.417. The obtained results indicate that the rotation, voltage, current and power increase in the relative vortex height of 0.065 and 0.111 when increasing the number of blades at flow velocity of less than 0.7 m/s. The average power of the 5-blade turbine is more than others. The performance of the 4-blade turbine with a 130 mm diameter installed near the orifice is higher than that of the same number of blades with a 220 mm diameter in the vortex chamber.

• The Journal of Korean Society for Radiation Therapy
• /
• v.22 no.2
• /
• pp.123-129
• /
• 2010

Purpose: The purpose of this study was to evaluate dosimetric characteristics of Optically stimulated luminescent dosimeters (OSLD) for dosimetry Materials and Methods: InLight/OSL $NanoDot^{TM}$ dosimeters was used including $Inlight^{TM}MicroStar$ Reader, Solid Water Phantom, and Linear accelerator ($TRYLOGY^{(R)}$) OSLDs were placed at a Dmax in a solid water phantom and were irradiated with 100 cGy of 6 MV X-rays. Most irradiations were carried out using an SSD set up 100 cm, $10{\times}10\;cm^2$ field and 300 MU/min. The time dependence were measured at 10 minute intervals. The dose dependence were measured from 50 cGy to 600 cGy. The energy dependence was measured for nominal photon beam energies of 6, 15 MV and electron beam energies of 4-20 MeV. The dose rate dependence were also measured for dose rates of 100-1,000 MU/min. Finally, the PDD was measured by OSLDs and Ion-chamber. Results: The reproducibility of OSLD according to the Time flow was evaluated within ${\pm}2.5%$. The result of Linearity of OSLD, the dose was increased linearly up to about the 300 cGy and increased supralinearly above the 300 cGy. Energy and dose rate dependence of the response of OSL detectors were evaluated within ${\pm}2%$ and ${\pm}3%$. $PDD_{10}$ and PDD20 which were measured by OSLD was 66.7%, 38.4% and $PDD_{10}$ and $PDD_{20}$ which were measured by Ion-chamber was 66.6%, 38.3% Conclusion: As a result of analyzing characteration of OSLD, OSLD was evaluated within ${\pm}3%$ according to the change of the time, enregy and dose rate. The $PDD_{10}$ and $PDD_{20}$ are measured by OSLD and ion-chamber were evaluated within 0.3%. The OSL response is linear with a dose in the range 50~300 cGy. It was possible to repeat measurement many times and progress of the measurement of reading is easy. So the stability of the system and linear dose response relationship make it a good for dosimetry.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.2
• /
• pp.77-86
• /
• 2008

The disturbance zone and measured values are affected by the size of the penetrometer. The local value may be measured by the smaller penetrometer. An ultra small Micro-Cone penetrometer (5mm in outer diameter) is designed and manufactured to characterize soil properties with minimum disturbance during penetration tests. The tip resistance is measured by using stain gauges attached near the Micro-Cone. In addition, the friction sleeve is adopted to effectively remove the skin friction from the tip resistance. Design concern includes the installation of stain gauges, circuits, penetration systems, penetration rate, sampling rate, operating temperature, and calibration. Application tests show that the clay interface, and the soil layers consisting of clay and sand are clearly detected by the Micro-Cone. Furthermore, the cone tip resistances measured by the Micro-Cone and the miniature cone (16mm in outer diameter) are similar. Note the resolution is much higher in the Micro-Cone. This study shows that the Micro-Cone may effectively detect the soil interface with high resolution, and with minimum disturbance.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.7
• /
• pp.1071-1075
• /
• 2003

In this paper, we present a DNA manipulation device in the reaction chamber, which consists of a center electrode and circular outer electrodes of a reaction unit. The charged bio-molecules, DNA, are manipulated by the charge of the electrode in reaction unit. Controlling the induced dynamic electric field between the center electrode and the outer electrodes, concentration / repulsion / manipulation of bio-molecules are enabled at a periphery of electrode. Concentration of the fluorescent DNA at the center electrode is observed by applying ＋2V. Subsequently, applying －2V, the concentrated DNA is repelled rapidly from the center electrode, which makes dispersion completely in 0.5second. Furthermore, repeated applying ＋1V/－1V every 5 seconds at each outer electrode, we can circulate the DNA. We also investigate a micro-heater and sensor for DNA manipulation and reaction temperature. The coefficient of heat-resistance and heater temperature characteristic is 0.0043 and 100$^{\circ}C$/sec, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.9
• /
• pp.42-47
• /
• 1998

We have fabricated electron-optical lens for micro E-beam system that can overcome the limitation of current E-beam lithography. Our electron-optical lens consists of multiple silicon electrodes which were fabricated by micromachining technology and assembled by anodic bonding. The assembled system was installed in UHV chamber to observe the emission characteristics of focused electrons by the electro-optical lens. We used STM(Scanning Tunneling Microscope) tip for electron source. By performing lithography with the focused electrons with PMMA(poly-methylmethacrylate) as E-beam resist. We could draw 0.13${\mu}{\textrm}{m}$ nano-scale lines.

• Advances in aircraft and spacecraft science
• /
• v.4 no.1
• /
• pp.21-35
• /
• 2017

Hydrogen peroxide is being considered as a monopropellant in micropropulsion systems for the next generation of miniaturized satellites ('nanosats') due to its high energy density, modest specific impulse and green characteristics. Efforts at the University of Vermont have focused on the development of a MEMS-based microthruster that uses a novel slug flow monopropellant injection scheme to generate thrust and impulse-bits commensurate with the intended micropropulsion application. The present study is a computational effort to investigate the initial decomposition of the monopropellant as it enters the catalytic chamber, and to compare the impact of the monopropellant injection scheme on decomposition performance. Two-dimensional numerical studies of the monopropellant in microchannel geometries have been developed and used to characterize the performance of the monopropellant before vaporization occurs. The results of these studies show that monopropellant in the lamellar flow regime, which lacks a non-diffusive mixing mechanism, does not decompose at a rate that is suitable for the microthruster dimensions. In contrast, monopropellant in the slug flow regime decomposes 57% faster than lamellar flow for a given length, indicating that the monopropellant injection scheme has potential benefits for the performance of the microthruster.

• Fashion & Textile Research Journal
• /
• v.10 no.5
• /
• pp.683-689
• /
• 2008

The purpose of this study was to investigate physiological responses such as rectal temperature, skin temperature, micro climate, sweat rate and subjective sensations using cold protective clothing with five different clo value. The clo value was measured by thermal manikin in windless condition. Healthy five 20's males volunteered as subjects for wearing trial experiment. The climate chamber was controlled at $50^{\circ}C$, 65% RH. The experiment consisted of repeated exercise and recovery periods. We found that the higher clo value has, the higher mean skin temperature, micro climate and sweat rate show. They felt warm and wet with higher insulation clothing. Thermal comfort increased in the last recovery period after exercise. There was significant difference between five cold protective clothing. In correlation analysis of clo value, it showed that correlation coefficient(r) values were more than 0.8. Therefore, in terms of clothing insulation, we found that correlation between thermal manikin experiment and wearing trial experiment was high. Clothing insulation could be variable according to many factors such as body movement, covering area, clothing gap, layering and design. Considering the body movement, we thought that insulation measurement need to carry out both thermal manikin experiment and wearing trial experiment.

• Journal of Sensor Science and Technology
• /
• v.20 no.6
• /
• pp.363-367
• /
• 2011

This paper proposes a highly-sensitive gas flow sensor with a simple structure. The sensor is composed of a micro-heater for heating the gas medium and a pair of temperature sensors for detecting temperature differences due to gas flow in a sealed chamber on one axis. Operation of the gas flow sensor depends on the transfer of heat through the air medium. The proposed gas flow sensor has the capability to measure gas flow rates <5 $cm^3$/min with a resolution of approximately 0.01 $cm^3$/min. Furthermore, this paper reports some additional experiment results, including the sensitivity of the proposed gas flow sensor as a function of operating current and the flow of different types of gas(oxygen, carbon dioxide, and nitrogen). The fabrication process of the proposed sensor is very simple, making it a good candidate for mass production.