• Clean Technology
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• v.8 no.3
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• pp.141-149
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• 2002

In the present study, flow fields inside a photocatalysis air cleaning system have been investigated to obtain the data for optimum design of the system. For this investigation, we first predicted the pressure drop of a photocatalysis filter. Based on this calculation, we replaced the filter by the porous media and analysed the performance of the entire system. This porous media assumption could predict characteristics of the cylindrical photocatalysis filter within 1%. Two cases of the cylindrical filter were considered in the present calculations. The first case had an inside diameter of 6 mm, while the second case had an inside diameter of 20 mm. It was found that the first case of filter showed a pressure drop three times higher than that of the second case. In addition, the cylindrical filter equipped with a housing to hold a number of cylinders in a bundle was also analyzed. When the housing was present, the pressure drop increased. It was found that the pressure drop is 8 times higher than that of the case when the housing was not equipped.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.1
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• pp.60-64
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• 2011

In this paper, we propose a new post-processing technique that removes blocking and ringing artifacts in Block discrete cosine transformation (BDCT)-coded images using bilateral filtering. The selection of filter parameters is a key issue in the application of a bilateral filter because it significantly affects the result. An efficient method of selecting the bilateral filter parameters is presented. The experimental results show that the proposed approach alleviates the artifacts efficiently in terms of PSNR, MSDS, and SSIM.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.259-266
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• 2006

As the volume of spam has increased to extreme levels, many anti-spam filtering techniques have been proposed. Among these techniques, the machine-Loaming filtering technique is one of the most popular filtering techniques. In this paper, we propose a machine-learning spam filtering technique based on the neural network, the genetic algorithm and the $X^2$-statistic. This proposed filtering technique is designed to overcome the problems in existing filtering techniques, and to achieve high spam filtering accuracy. It is able to classify spam and legitimate emil with 95.25 percent and 95.31 percent accuracy. This accuracy of the sum filtering is 7.75 percent and the 12.44 percent higher than rule-based filtering and the Bayesian filtering technique, respectively.

• Journal of IKEEE
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• v.14 no.4
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• pp.263-269
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• 2010

In this paper, we present high temperature characteristics of a tunable all-optical filter using fiber Bragg grating(FBG) filter in Ge doped and Ge & B co-doped fiber, including peak reflectivity, bandwidth and various normalized refractive index change with temperature variation. The reflection spectrum of a FBG filter with refractive index change is affected by its thermal stability. Consequently Ge doped FBG tunable filter has a better thermal stability than Ge & B co-doped FBG tunable filter. Also, both FBG tunable filters show good thermal stability up to about $500^{\circ}C$.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.301-306
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• 2021

The use of tin filters as a way to reduce the medical radiation in computed tomography (CT). However, due to the changed X-ray spectrum with the use of tin filters, disease diagnosis could be affected because it appears as images of different impressions from previous images. Therefore, this study evaluates the changes in images when using tin filter and high pitch in chest low-dose CT. In this study, images were acquired in groups of three for comparison. Group 1 did not apply to tin filter, and used the existing pitch 0.8. Group 2 used a tin filter, pitch 0.8, Group 3 used a tin filter, and pitch 2.5. To compare the image quality, the natural image quality evaluator (NIQE) and the blind/referenceless image quality evaluator (BRISQUE) were used among the blind quality evaluation factors depended on a no-reference basis. As a result, the NIQE values were low in the order of Group 1, Group 3, and Group 2. BRISQUE values were low in the order of Group 3, Group 2 and Group 1. This study confirms the superiority of images of tin filter and high pitch techniques in chest low-dose CT, which is considered to be a fundamental study for acquiring accurate images of patients with difficult breathing control.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.51-56
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• 2012

One of the most critical and essential procedures in the interpretation of gravity and magnetic data is to separate the anomaly due to the specific geologic structure from the summation of effects from a broad variety of geologic sources, especially those of different depths. Separation of the residual anomaly from the regional field is the most simple case of the vertical separation. If the anomaly due to a layer of specific depth can be separated or the depth of the separated layer can be quantitatively determined, it may deserve the separation-sounding. We suggest a wavelength filter whose cutoff frequency is determined by log-power spectrum analysis, as a separation-sounding filter. We applied this filter both to synthetic and real gravity data acquired at Heunghae area, and compared the results with those of Jacobsen's upward continuation filter. These showed that the proposed separation-sounding filter could be a useful tool for interpretation of the vertical geologic structure by stripping the gravity effects of geologic sources down to the desired depth.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.4 s.34
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• pp.27-32
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• 2005

DEM is needed for urban modeling, forecasting of floods and the analysis of slope and aspect. It has been generated using digital maps, aerial photos or satellite imageries. Recently, however, many studies on DEM generation from LiDAR data has been conducted because of its efficiency and accuracy. Filtering is said to be the process of making DEM by eliminating non-ground points from LiDAR data. In most researches, some input parameters such as the size of filter are required. The purpose of this investigation is to automatically obtain DEM by eliminating objects of various sizes without the knowledge of the objects' sizes. The experimental results show that most of objects on steep terrain are eliminated by the proposed method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.225-230
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• 2017

In this paper, a highly efficient GMR(guided-mode resonant) color filter is proposed and implemented. The GMR color filter consists of $Si_3N_4/air$ layers containing complementary fixed and mobile gratings. The device is designed using RETT(rigorous equivalent transmission-line theory) and a grating structure operating in subwavelength. The numerical result reveals that the color filter has a tuning capability of about 35 nm over the $0.45{\mu}m{\sim}0.55{\mu}m$ range for blue-green color and across $0.6{\mu}m{\sim}0.7{\mu}m$ range for red color. Furthermore, The color filters have a spectral bandwidth of about 8 nm with efficiencies of 99%, 98%, and 99% at the center wavelength of blue, green, and red color, respectively, and these are higher efficiencies than reported in the literature previously.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.593-598
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• 2006

High-resolution satellite imagery has many benefits, compared to aerial photo in the wide area as well as multi-spectral character. So, it can be used well for constructing GIS data when making digital map. This study analysed the possibilities that road information derived automatically from IKONOS can be used for making ITS system or updating digital map of the urban areas where change frequently and producing satellite image map. In this study, Sobel was applied for road edge dectection after low pass filtering. As the results, it's possible for low pass filtering and high pass filtering to be used as the basic data for ITS construction when extracting edge roads and constructs according to the characteristic of high-resolution satellite imagery.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.723-733
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• 2011

A numerical method of the CSF(Continuum Surface Force) model is presented for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The application of the present method to a 2-D liquid drop problem is illustrated by an equilibrium and nonequilibrium oscillating drop calculation. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows.