• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E1
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• pp.29-36
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• 2002

The selective catalytic reduction (SCR) reaction of promoter catalysts was investigated in this study. A pure anatase type of TiO$_2$ was used as support. Activation measurement of prepared catalysts was practiced on a fixed reactor packing by the glass bead after filling up catalysts in 1/4 inch stainless tube. The reaction temperature was measured by K-type thermocouple and catalyst was heated by electric furnace. The standard compositions of the simulated flue gas mixture in this study were as follows: NO 1,780ppm, NH$_3$1,780ppm, $O_2$1% and $N_2$ as balance gas. In this study, gas analyzer was used to measure the outgassing gas. Catalyst bed was handled for 1hr at 45$0^{\circ}C$, and the reactivity of the various catalyst was determined in a wide temperature range. Conversion of NH$_3$/NO ratio and of $O_2$ concentration was practiced at 1,1.5 and 2, respectively. The respective space velocity were as follows . 10,000, 15,000 and 17,000 hr-1. It was found that the maximum conversion temperature range was in a 5$0^{\circ}C$. It was also found toi be very sensitive at space velocity, $O_2$ concentration, and NH$_3$/NO ratio. We also noticed that the maximum conversion temperature of (W, Mo, Sn) -V$_2$O$_{5}$/TiO$_2$ catalysts was broad. Specially WO$_3$-V$_2$O$_{5}$TiO$_2$2 catalyst appeared nearly 100% conversion at not only above 30$0^{\circ}C$ ut also below 25$0^{\circ}C$. At over 30$0^{\circ}C$, NH$_3$ oxidation decreased with decrease of surface excess oxygen. In addition, WO$_3$-V$_2$O$_{5}$TiO$_2$ catalyst did not appear to affect space velocity, $O_2$ concentration, and NH$_3$/NO ratio.ratio.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.2
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• pp.131-139
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• 1996

The developent of ceramic combustor is being increased beca- use of the excellent physical properties of ceramic material, that is, high-resistant strength, high emissivity power and high corrosin-resistance. Ceramic combustor has been interested in the application of ultra-lean combustion for low NO$_{x}$ emission and gaseuos waste incineration with good combustion. This experimental study was conducted to investigate the combustion and emission characteristics of wall recess type ceramic combustor with equivalence ratio, mixture flow velocity and wall recess depth as parameters. The results in this study are as follows: 1. Wall recess played a important role to extend flame stability region. 2. The peak temperature of gas was peoportional to equivalence ratio, mixture flow velocity and wall recess depth. 3. The static pressure of mixing chamber and inlet temperature depended on the position of flame zone. 4. NO reduction was achieved by lean mixture without lower combustibility.y.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.587-592
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• 2010

A numerical analysis of reactive flow in a MILD(Moderate and Intense Low oxygen Dilution) combustor is accomplished to elucidate the characteristics of combustion phenomena in the furnace with the variation of air fuel ratio. For the smaller magnitude of air injection velocity(10 m/s), the air flow could not penetrate toward upper part of furnace. On the other hand, the air flow suppresses the fuel flow for the case of air injection velocity 30 m/s. The air velocity 18 m/s is corresponding to the stoichiometric air flow velocity, and for that case, the air flows to relatively more upper part of the furnace when compared with the case of air injection velocity 10 m/s. The reaction zone is produced with the previous flow pattern, so that the reaction zone of the air injection velocity 10 m/s is biased to the air nozzle side and for the case of air injection velocity 30 m/s, the reaction zone is inclined to the fuel nozzle side. For the cases with the air injection velocities 16, 18, 20 m/s, the reaction zone is nearly located at the center between air nozzle and fuel nozzle. The maximum temperatures and NOx concentrations for the cases of air injection velocity 16, 18, 20 m/s are lower than the cases with air injection velocity 10, 30 m/s. From the present study, the stoichiometric air fuel ratio is considered as the most optimal operating condition for the NOx reduction.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.7
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• pp.832-838
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• 2003

IMO NOx levels are generally possible to meet by means of primary on-engine measures. Nevertheless further significant follow-on reductions are likely to require a secondary after-treatment technique. SCR system is currently the only available technology proven at full scale to meet the 90% NOx reduction levels. Accordingly, maybe the use of an SCR system on board ship provides the solution to minimize this primary pollutant without increasing fuel consumption. In order to develop a practical SCR system for marine application on board ship, a primary SCR system using urea was made. The SCR system was set up on the ship. employed a two-stroke diesel engine as a main propulsion. which is a training ship in KMU (Korea Maritime Univ.). The purpose of this paper is to report the results about the basic effects of the above system parameters which is investigated from practical application through its trial use. The degree of NOx removal depends on some parameters. such as the amount of urea solution added, space velocity. reaction gas temperature and activity of catalyst. The preliminary results from trial run are presented.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.18-21
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• 2020

Undetected wafer slip during the lift pin-down motion in semiconductor equipment may affect the center to edge variation, wafer warpage, and pattern misalignment in plasma equipment. Direct measuring of the amount of wafer slip inside the plasma process chamber is not feasible because of the hardware space limitation inside the plasma chamber. In this paper, we demonstrated a practice for the wafer lift pin-up and down motions with respect to the gear ratio, operating voltage, and pulse width modulation to maintain accurate wafer position using remote control linear servo motor with an experimentally designed chamber mockup. We noticed that the pin moving velocity and gear ratio are the most influencing parameters to be control, and the step-wised position control algorithm showed the most suitable for the reduction of wafer slip.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.274-279
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• 2009

Reduction Gear Box where from productive site uses the gear with power delivery with high mechanical efficiency of power a deceleration and as the mechanical element union product which has the velocity ratio which is various together is produced with the power occurrence motor and leads gets a high driving force is plentifully used. The above occurs from gear drive issue sound Whine, Noise and Vibration as occurring from the rim process which the gear will bite mainly is delivered with the case etc. gear drive whole which leads the axis and the bearing. The productivity falls with the going straight rate decrease which with like this problem point is caused by with rework the problem point where the cost of production rises under improving boil many kinds analyzed the plan and investigates the resultant acceleration sensor which and a frequency analysis system and was made to apply.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1309-1317
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• 2011

This study selected 6 river reach, which have various curved-channel, included in an object of study as making the Nakdong River, which is a real nature river, as a point of an object of study by using SMS RMA-2 model, a 2D numerical analysis model, and applied project flood and analyzed and examined characteristic of hydrological property and super-elevation, which includes characteristic of the velocity of a moving fluid. As a result, in a river reach, whose width is wide, angle of curved-channel has impact on the velocity of a moving fluid of inside of curved-channel and in a river reach, whose width is narrow, the radius of curvature and width of the river have impact on the velocity of a moving fluid of inside of curved-channel. Also it found out that the ratio of reduction in water-level of inside of curved-channel is more bigger than ratio of increasing in water-level of outside of curved-channel when project flood is increasing and angle of curve is increasing. Based on this, this study would be used as a expectation of danger and preliminary data in planning real river or a business, that creates an environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.70-80
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• 2001

A cycloid reducer is one of the rotational velocity reduction equipments of machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of transmission ratio and the smaller workspace than other kinds of reducer. A cycloidal plate gear is a main part of the cycloid reducer. Its tooth shape is peculiar because of gearing with the roller gear that has the several rollers on the circular line. And then it can be designed to contact all teeth to rollers. So, the cycloid reducer has the good characteristics in the dynamic properties and the zero-backlash in the contact motion. It can be used in robots, high-precision machines and high capacity machinery. This paper proposes a new approach for the shape design of the cycloidal plate gear and presents a Computer-Aided-Design program developed by the proposed method. The first part of this paper defines the two types of the cycloid reducers and explains their mechanisms. The second part defines the instant velocity centers for each type of the cycloid reducers and calculates the contact angles and the contact points by using te geometric relationships and the kinematical properties of the reducers. The third part generates the full shape of the cycloidal plate gear by the coordinate transformation technique. Finally, this paper presents two examples for the shape design of the cycloidal plate gear in order to prove the theory of the proposed method in this paper and the accuracy of the \"CycloGear Designer\".

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.394-399
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• 2015

Because flow uniformity affects the life cycle and performance of the catalyst, it is an important design factor for selective catalytic reduction (SCR) systems. We examined how the diffuser angle and the area ratio of the inlet of the SCR reactor to the front of the catalyst affect flow uniformity. For the numerical analysis, we used STAR-CCM+, a common CFD software program. Analysis results showed that the larger the area ratio was, the less the flow uniformity was, and that the longer the diffuser length was, the greater the flow uniformity was. When the area ratio was greater than 1:5, the flow uniformity appeared very similar at the front of the catalyst. As a result, the spread time of the exhaust gas increased and the flow velocity decreased.

• Wind and Structures
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• v.18 no.1
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• pp.69-82
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• 2014

Flow around a small white fir tree was investigated with varying the length of the bottom trunk (hereafter referred to as bottom gap). The velocity fields around the tree, which was placed in a closed-type wind tunnel test section, were quantitatively measured using particle image velocimetry (PIV) technique. Three different flow regions are observed behind the tree due to the bottom gap effect. Each flow region exhibits a different flow structure as a function of the bottom gap ratio. Depending on the gap ratio, the aerodynamic porosity of the tree changes and the different turbulence structure is induced. As the gap ratio increases, the maximum turbulence intensity is increased as well. However, the location of the local maximum turbulence intensity is nearly invariant. These changes in the flow and turbulence structures around a tree due to the bottom gap variation significantly affect the shelter effect of the tree. The wind-speed reduction is increased and the height of the maximum wind-speed reduction is decreased, as the gap ratio decreases.