• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.950-955
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• 2001

For the development of an ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We analyze and test the unit removal profiles for a ball type polishing tool. Using these results we calculate dwell time distributions and residual errors for a target removal shape. We use the polishing simulation method and feed rate calculation method for the dwell time calculation. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.74-78
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• 2002

Ultra-Precision CNC polishing system including on-machine measurement system, a corrective polishing algorithm is developed. The unit removal profiles for various polishing tools and analyzed and tested and dwell time distributions and residual errors for a target removal shape are calculated. The corrective polishing algorithm is tested with various workpieces. This result will be used for the software development of the CNC polishing system.

• 한국정밀공학회지
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• 제19권1호
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• pp.99-106
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• 2002

For the development of a ultra-precision CNC polishing system including on-machine measurement system, we study a corrective polishing algorithm. We calculated unit removal profiles for various flat type polishing tools and polishing tool positions. Using these results we simulate the corrective polishing process based on dwell time control. We calculate dwell time distributions and residual error of the polishing simulation method and the FFT calculation method. We test corrective polishing algorithm with an optical glass. The target removal shape is a sine wave that has amplitude 0.3 micro meters. We find this polishing process has a machining resolution of nanometer order and is effective for sub-micrometer order machining. This result will be used for the software development of the CNC polishing system.

• Steel and Composite Structures
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• 제15권2호
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• pp.151-162
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• 2013

In this study, an electrolyzing device for the production of metal powders was designed and fabricated. The production of copper powders was performed using a variety of current densities, anode-cathode distances and power removal times. The effect of these parameters on powder particle size and shape was determined. Particle size was measured using a laser diffraction unit while the powder shape was determined by SEM. Experimental results show that an increase in current density leads to a decrease in powder particle size. In addition particle shape changed from globular dendritic to acicular dendritic with increasing the current density. Distance between the cathode and anode also showed a similar influence on powder particle size and shape. An increase in time of powder removal led to an increase in powder particle size, as the shape changed from acicular dendritic to globular dendritic.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.311-315
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• 2001

This paper presents the result of basic study about corrective polishing for arbitrary surface figure. In this study, we researched polishing characteristics on the working condition of optical glass. The abrasive size, relative velocity and working pressure were selected major factors that affect polishing process. The Preston's equation which is the representative model of polishing process was used to model the unit removal shape. The Preston's coefficient and unit removal function were calculated from the polished surface. Applying these results, we have shown that the systematic corrective polishing of arbitary figure is feasible through experiments and analysis.

• 한국대기환경학회지
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• 제24권4호
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• pp.483-491
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• 2008

The filtration characteristics of $CYBAGFILTER^{(R)}$ unit with pleated filter bags were evaluated by comparing the performance of the unit with the lower part of cyclone shape with that of the unit with conventional lower part. Results from the test were also compared with those from the previous research with the $CYBAGFILTER^{(R)}$ in which round filter bags were installed. $CYBAGFILTER^{(R)}$ is the unit which combines the centrifugal separation mechanism and the fabric filtration mechanism in a single unit for efficient removal of particulate matters. The pleated filter bags are made of pleated fabric with an extension of the filtration area about 3 times compared with the conventional round filter bags. The results from the test using pleated filter bags showed an overall collection efficiency of over 99.9% regardless of the shape of lower part installed. When the lower part of cyclone shape was installed, the filter cleaning interval was over 2 times longer compared with that when the conventional lower part was installed. At the same conditions of filtration velocity and filter pressure drop, the $CYBAGFILTER^{(R)}$ with the lower part of cyclone shape, in which the pleated filter bags are installed, can be operated with a flow rate of round 3 times higher than that with conventional round filter bags.

• 한국대기환경학회지
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• 제26권1호
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• pp.85-93
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• 2010

$CF_4$ removal characteristics were investigated using an elongated arc reactor. The advantage of the elongated arc reactor includes direct use of treated gas as plasma operating gas and the enhancement of the removal reaction by using a thermo-chemistry and a plasma induced chemistry at the same time. Geometrical configurations, such as the length of the reactor and the shape of a throat, were tested to get an optimized removal efficiency with low power consumption. As results, over 95% of $CF_4$ removal was obtained with 300 lpm of total flowrate for various $CF_4$ concentration (0.1~1%). Corresponding specific energy density (SED), which means required electrical energy to treat the unit volume of treated gas, is about 3.5 kJ/L, The present technique can be applied to real applications by satisfying three major concerns, those are the high flowrate of treated gas, high removal efficiency (> 95%), and low power consumption (< 10 kJ/L).

• 한국입자에어로졸학회지
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• 제5권2호
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• pp.37-43
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• 2009

Particulate matter (PM) is one of the major indoor air pollutants especially in the subway station in Korea. In order to remove PM in the subway station, several kinds of PM removal system such as roll-filter, auto-washable air filter, demister, and electrostatic precipitator are used in the air handling unit (AHU) of subway stations. However, those systems are prone to operation and maintenance problems since the filter-regeneration unit consisting of electrical or water jet parts might malfunction due to the high load of particulates unless the filter medium is periodically replaced. In this study, the use of axial-flow cyclone was proposed for particulate filter unit in the AHU for its low operation and maintenance cost. Novel shape of axial-flow cyclone was designed by using computational fluid dynamics (CFD). The shape of vortex vane was optimized in terms of pressure drop and tangential velocity. In addition, CFD analysis was validated experimentally through the pressure drop measurement of mock-up model. We found that pressure drop and tangential velocity of fluid through the axia-flow cyclone was significantly affected by the rotating degree of vortex vane and the numerical prediction of pressure drop agreed well with experimental measurement.

• 한국정밀공학회지
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• 제28권8호
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• pp.929-935
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• 2011

As a deterministic finishing process for the optical parts having complex surface, machining performance of the magnetorheological(MR) fluid jet polishing of optical glass are studied and compared with a general water jet polishing. First, design of the jet polishing system which has the special electromagnet-nozzle unit for stabilizing the slurry jet based on MR fluid and the change of jet shape as magnetic field is applied are explained. Second, for the BK7 glass, machining spot and its cross section profile are analyzed and the unique effect of MR fluid jet polishing is shown. Third, both material removal depth and surface roughness are explored in order to investigate the polishing performance of MR fluid jet. With the same ceria abrasives and amount in the polishing slurries, MR fluid jet shows superior machining performance compared to water jet and the difference of material removal mechanism and its resulting performance are described.

• 한국입자에어로졸학회지
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• 제5권4호
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• pp.189-197
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• 2009

Wet-type particulate removal system is employed in most of ironmaking processes. These de-dusting systems require additional downstream aggregates for treatment of water and for drying of the collected slurry. Thus dried slurry can be pressed in shape of briquettes and recycled in the steelmaking process. Different from the wet-type, the dry-type particulate removal systems generate no slurry. A high-temperature, high-pressure de-dusting system with inertial inlet was developed. The target application of this system was to remove particulate matter generated from the novel ironmaking process and other steelmaking processes. In this study we conducted tests with this newly developed system to evaluate the performance of the silica-carbide (SiC) ceramic filters. In addition, for purpose of comparison, we also conducted tests with a unit which has conventional direct inlet. Fe-Particles collected from the novel ironmaking process were used in our tests as test dusts. The temperature and the pressure were kept constant at their respective values $800^{\circ}C$ and $3kg_f/cm^2$.