• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1111-1120
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• 1998

Spray Drying Absorber(SDA) system, where the combustion product gas is mixed with atomized limestone-slurry droplets and then the chemical reaction of $SO_2$ with alkaline components of the liquid droplets forms sulfates, has been widely used to eliminate $SO_2$ gas from coal fired power plants and waste incinerators. Liquid atomization is necessary because it can maximize the reaction efficiency by increasing the total surface area and dispersion angle of the alkaline components. First, numerical calculations using FLUENT are carried out to investigate $SO_2$ concentration distribution and thus to calculate $SO_2$ removal efficiency. So to attain the optimized spray conditions, then an electrostatic spraying system is set up and spray visualization is performed to show the effect of an electric field on overall droplet size. Next, the effect of an electric field on the concentrations of $SO_2$ is experimentally examined. Field strength is varied from -10 kV to 10 kV and configurations of conduction charging and induction charging are utilized. Consequently, the electrostatic removal efficiency of 501 increases about 30% with the applied voltage of ${\pm}10kV$ but is independent of polarity of the applied voltage. It Is also found that the conduction charging configuration results in higher efficiency of $SO_2$ removal that the induction charging configuration. Finally, the effect of slurry temperature on $SO_2$ removal is studied. The temperature influences on the electrostatic removal efficiency of $SO_2$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.415-421
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• 2013

This study describes the aerodynamic design procedure for the axial turbines of a small heavy-duty gas turbine engine being developed by Doosan Heavy Industries. The design procedure mainly consists of three parts: namely, flowpath design, airfoil design, and 3D performance calculation. To design the optimized flowpath, through-flow calculations as well as the loss estimation are widely used to evaluate the effect of geometric variables, for example, shape of meridional plane, mean radius, blades axial gap, and hade angle. During the airfoil design procedure, the optimum number of blades is calculated by empirical correlations based on the in/outlet flow angles, and then 2D airfoil planar sections are designed carefully, followed by 2D B2B NS calculations. The designed planar sections are stacked along the spanwise direction, leading to a 3D surfaced airfoil shape. To consider the 3D effect on turbine performance, 3D multistage Euler calculation, single row, and multistage NS calculations are performed.

• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.1-9
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• 1999

A study has been made on the fabrication of a dual mode(a longitudinal and shear mode) ultrasonic sensor using a single PZT piezoelectric ceramic element. We investigated the mechanism of the dual mode sensor that generated both of the longitudinal and the shear waves simultaneously with the single PZT element. Through the analysis of analytic wave propagation equations, all the possible crystal cuts have been examined to determine appropriate Euler transformation angles for efficient excitations of the dual modes. We studied the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves of equal strength. Experimental examination of the waveform on a delay line(STS303) setup confirms that the ultrasonic sensor can transmit and detect both longitudinal and shear waves simultaneously.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.7
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• pp.1121-1127
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• 2009

This study presents an eco-friendly and one-step finishing method for modifying fiber property that reduces fiber damage in wool/polyester blend fabrics. Lipase from aspergillus oryzae is used in this experiment. The enzymatic treatment condition is optimized by measuring the relative activity of lipase depending on pH level, temperature, concentration of lipase, and treatment time. The concentration of $CaCl_2$as an activator is determined by the characteristics including whiteness, water contact angle (WCA), and dyeing property. The modified properties of lipase treated fabrics are tested for pill resistance and surface morphology. The results are described as follows: the optimum condions for lipase treatment constitute a pH level of 8.0, treatment temperature of 40$^{\circ}$$_C$, concentration of lipase at 100% (o.w.f), and a treatment time of 90 minutes. $CaCl_2$helps in raising lipase activation, and the optimum concentration is 50mM. The whiteness, wet ability, and pill resistance of lipase treated fabrics improves as compared to the control. The dyeing property of lipase treated fabrics improved by 53.5% after using the one-bath dyeing method. This means that lipase treatment can save time and cost during the dyeing process since lipase treatment modifies wool and polyester fibers. The surface of lipase treated wool fibers do not exhibit any change, however voids and cracks manifest on the surface of lipase treated polyester fibers.

• Journal of Power Electronics
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• v.10 no.5
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• pp.548-554
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• 2010

In this paper, a 1.5 kW Interior Permanent Magnet Synchronous Generator (IPMSG) with a power conditioner for the grid integration of a variable-speed wind turbine is developed. The power-conditioning system consists of a series-type 12-pulse diode rectifier powered by a phase shifting transformer and then cascaded to a PWM voltage source inverter. The PWM inverter is utilized to supply sinusoidal currents to the utility line by controlling the active and reactive current components in the q-d rotating reference frame. While the q-axis active current of the PWM inverter is regulated to follow an optimized active current reference so as to track the maximum power of the wind turbine. The d-axis reactive current can be adjusted to control the reactive power and voltage. In order to track the maximum power of the wind turbine, the optimal active current reference is determined by using a simple MPPT algorithm which requires only three sensors. Moreover, the phase angle of the utility voltage is detected using a simple electronic circuit consisting of both a zero-crossing voltage detecting circuit and a counter circuit employed with a crystal oscillator. At the generator terminals, a passive filter is designed not only to decrease the harmonic voltages and currents observed at the terminals of the IPMSG but also to improve the generator efficiency. The laboratory results indicate that the losses in the IPMSG can be effectively reduced by setting a passive filter at the generator terminals.

• Korean Journal of Remote Sensing
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• v.33 no.4
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• pp.359-375
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• 2017

We developed fog detection algorithm (KNU_FDA) based on the optical and textural properties of fog using satellite (COMS) and ground observation data. The optical properties are dual channel difference (DCD: BT3.7 - BT11) and albedo, and the textural properties are normalized local standard deviation of IR1 and visible channels. Temperature difference between air temperature and BT11 is applied to discriminate the fog from other clouds. Fog detection is performed according to the solar zenith angle of pixel because of the different availability of satellite data: day, night and dawn/dusk. Post-processing is also performed to increase the probability of detection (POD), in particular, at the edge of main fog area. The fog probability is calculated by the weighted sum of threshold tests. The initial threshold and weighting values are optimized using sensitivity tests for the varying threshold values using receiver operating characteristic analysis. The validation results with ground visibility data for the validation cases showed that the performance of KNU_FDA show relatively consistent detection skills but it clearly depends on the fog types and time of day. The average POD and FAR (False Alarm Ratio) for the training and validation cases are ranged from 0.76 to 0.90 and from 0.41 to 0.63, respectively. In general, the performance is relatively good for the fog without high cloud and strong fog but that is significantly decreased for the weak fog. In order to improve the detection skills and stability, optimization of threshold and weighting values are needed through the various training cases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.183-190
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• 2014

A multiphase pump was developed in this study. The optimum multiphase pump design was arrived at, and the interactions among the different geometric configurations were explained by applying numerical analysis and the DOE (design of experiments) method. First, we designed the base model to meet the specifications. Then, we defined the design parameters related to the meridional plane and the blade angle. Each design parameter was used for generating experiment sets, and numerical analyses were performed on these sets. Finally, the optimized design was selected based on the results of the DOE analysis. The numerical optimization resulted in the optimum model having higher efficiency than the base model. In addition, performance degradation due to changes in the GVF (gas volume fraction) is discussed.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.204-209
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• 2003

In an urban area telecommunication using wireless system, the accurate prediction and analysis of wave propagation characteristics are very important to determine the service area, optimized selection of base station, and cell design, etc. In the stage of these analyses, we have to present the propagation prediction model which is varied with the type of antenna, directional angle, and configuration of the ground in our urban area. In addition we need to perform an analysis of the conventional model which is similar to ours and dig out the parameters to evaluate the wave environment before the cell design for the selected area. In this paper, we propose a wave propagation prediction model concerning the topography and obstacles in our urban area. We extract the parameters and apply them to the proposed wave environment for the simulation analyzing the propagation characteristics. Throughout these analyzing procedure, we extracted the essential parameters such as the position of the base station, the height of topography, and adequate type and height of the antenna with our preferable correctness.

• Membrane and Water Treatment
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• v.8 no.3
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• pp.225-244
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• 2017

A novel thin-film nanocomposite (TFN) reverse osmosis (RO)/non-woven fabric (NWF) membrane was prepared by adding zinc oxide (ZnO) nanospheres ($30{\pm}10nm$) during the interfacial polymerization process of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on self-made polysulfone (PSF) membrane/polyester (PET) non-woven fabric support. The improved performance of TFN RO membrane was verified in terms of water contact angle (WCA), water flux, salt rejection, antifouling properties and chlorine resistance. The results showed that the WCA value of TFN RO surface had a continuous decrease with the increasing of ZnO content in MPD aqueous solution. The water flux of composite TFN RO membranes acquired a remarkable increase with a stable high solute rejection (94.5 %) in $1g{\cdot}L^{-1}$ NaCl aqueous solution under the optimized addition amount of ZnO (1 wt%). The continuous testing of membrane separation performance after the immersion in sodium hypochlorite solution indicated that the introduction of ZnO nanospheres also dramatically enhanced the antifouling properties and the chlorine resistance of composite RO membranes.

• Journal of the Korean Graphic Arts Communication Society
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• v.27 no.1
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• pp.1-14
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• 2009

The color reproduction of digital still camera does not, in general, match those of the final output device. Because color gamut of these devices is different, it is therefore necessary to take account of a way to match. The way uses the optimized profile to output device an image. This paper proposed a way to create the input profile of digital still camera for standardization soft proofing process. The results of proposed way showed that for input profiles equivalent, good results relatively. In this paper, an experiment was done where the illumination sources used as the standard illumination 5200K and illuminated at a $45^{\circ}$ angle in the best illumination efficiently. The white balance was in mode 'custom' : aperture F11, exposure time 1/60s, ISO50, focal length 80mm. The images were exported and saved as 16bit RGB TIFF(AdobeRGB, sRGB, ProphotoRGB) images. To do the test, the RGB values of the RGB TIFF images are processed through the ICC input profile to arrive at processed $CIEL^*a^*b^*$ values. A profiling tool such as ProfileMaker 5.0 and Monacoprofile 4.8 are used to do this. The processed $CIEL^*a^*b^*$ values are compared to the reference $CIEL^*a^*b^*$ values and these two values are used to calculate a ${\Delta}E{^*}_{ab}$.