• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1681-1685
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• 2014

The visual quality of medical image is an important factor for diagnosis accuracy. Therefore, the methods to improve the quality of medical image have studied. Among them, frequency domain filter is very powerful method to impove the visual quality of image. In this paper, the X-ray medical image using optimized high-pass filter was improved edges. The result image was improved edge and contrast of flat area using optimized high frequency emphasis filter. At last, the result image is to minimize the noise using the minimum mean square error(MMSE) filter. As a result, the proposed method has enhanced contrast and edge of the image in the contrast of existing filters, with the noise canceling effect.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.30-35
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• 2006

This paper describes fully integrated low phase noise MMIC voltage controlled oscillators(VCOs). The Asymmetrical Inductance Tank VCO(AIT-VCO), which optimize the shortcoming of the previous tank's inductance optimization approach, has lower phase noise performance due to achieving higher equivalent parallel resistance and Q value of the tank. This VCO features an output power signal in the range of - 11.53 dBm and a tuning range of 261 MHz or 15.2 % of its operating frequency. This VCO exhibits a phase noise of - 117.3 dBc/Hz at a frequency offset of 100 kHz from carrier. A phase noise reduction of 15 dB was achieved relative to only one spiral inductor. The AIT-VCO achieved low very low figure of merit of -184.6 dBc/Hz. The die area, including buffers and bond pads, is $0.9{\times}0.9mm^2$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.451-454
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• 2011

In this paper, a wideband clock generator using novel Automatic frequency calibration(AFC) scheme is proposed. Wideband clock generator using AFC has the advantage of small VCO gain and wide frequency band. The conventional AFC compares whether the feedback frequency is faster or slower then the reference frequency. However, the proposed AFC can detect frequency difference between reference frequency with feedback frequency. So it can be reduced an operation time than conventional methods AFC. Conventional AFC goes to the initial code if the frequency step changed. This AFC, on the other hand, can a prior state code so it can approach a fast operation. In simulation results, the proposed clock generator is designed for DisplayPort using the CMOS ring-VCO. The VCO tuning range is 350MHz, and a VCO frequency is 270MHz. The lock time of clock generator is less then 3us at input reference frequency, 67.5MHz. The phase noise is -109dBC/Hz at 1MHz offset from the center frequency. and power consumption is 10.1mW at 1.8V supply and layout area is $0.384mm^2$.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.225-233
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• 1999

Harbor design and construction plan in Korea becomes the most hot issue both in the Maritime Affairs and Fisheries Office and in the related port industries. Production of the plane and cross section maps together with the profile map for harbor project is done firstly and is important in all procedure because it is the most basic datum in counting the constructional expense for determination of the area and capacity. As the expense assigned on surveying part among the total expenses of harbor planning and construction in Korea is very small, it is difficult to make exact maps. Moveover, because the method used to make such maps is mostly traditional surveying such as plane table surveying , offset surveying, stadia surveying and level surveying, etc, it is difficult to get precise three dimensional maps. Therefore, for making more precise map in the harbor project, we have to use the newest surveying equipment. This study discusses the method of old surveying and recent surveying used for the three dimensional map of the site for lighthouse which gives navigational aids for the in-and out-bound ships. The authors are proposing a method for more precise three dimensional positioning in this study.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.4
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• pp.305-313
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• 2022

The evolution of the GNSS (Global Navigation Satellite System) technology has enhanced positioning performance in terms of positioning accuracy and time efficiency. The technology makes it possible to determine orthometric heights at a few centimeter accuracies by transforming accurate ellipsoid heights if an accurate geoid model has been employed. This study aims to generate a correction surface using GNSS/leveling co-points and a local geoid model, Thailand Geoid Model 2017 (TGM2017), through the Kriging interpolation method in a small local area. Combining the surface and TGM2017 significantly improves height transformation with the 1-cm RMSE (Root Mean Square Error) fit of 10 GNSS/leveling reference points and a mean offset of +0.1 cm. The evaluation of the correction surface at 5 GNSS/leveling checkpoints shows the RMSE of 1.0 cm, which is 82.6 percent of accuracy improvements. The GNSS leveling method can possibly be used to replace a conventional leveling technique at a few centimeter uncertainties in the case of small areas with clear-sky and high satellite visibility environments.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1291-1298
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• 2023

Surveillance reconnaissance sensor network is used for surveillance in wartime and area of operation. In this paper, we propose a target localization method using the detection signal strength of seismic sensors. Relay equipment calculates the target location using coordinate information and detection signal strength of the seismic sensors. Target localization error deviation due to environmental factors was minimized by subtracting the dynamic offset when calculating the target location. Field test shows improvement of target localization through reduction of errors. The average error was decreased to 3.62m. Up to 62% improved result was obtained compared to weighted centroid localization method.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.223-231
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• 2024

For the OPR1000, a standard power plant in Korea, an analytical model of the containment building considering voids and deterioration was built with multilayer shell elements. Voids were placed in the vulnerable parts of the analysis model, and the deterioration effects of concrete and rebar were reflected in the material model. To check the impact of voids and deterioration on the seismic performance of the containment building, iterative push-over analysis was performed on four cases of the analytical model with and without voids and deterioration. It was found that the effect of voids with a volume ratio of 0.6% on the seismic performance of the containment building was insignificant. The effect of strength reduction and cross-sectional area loss of reinforcement due to deterioration and the impact of strength increase of concrete due to long-term hardening offset each other, resulting in a slight increase in the lateral resistance of the containment building. To determine the limit state that adequately represents the seismic performance of the containment building considering voids and deterioration, the Ogaki shear strength equation, ASCE 43-05 low shear wall allowable lateral displacement ratio, and JEAC 4601 shear strain limit were compared and examined with the analytically derived failure point (ultimate point) in this study.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.88-90
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• 2012

This paper describes a 10-bit 10-MS/s asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) with a rail-to-rail input range. The proposed SAR ADC consists of a capacitor digital-analog converter (DAC), a SAR logic and a comparator. To reduce the frequency of an external clock, the internal clock which is asynchronously generated by the SAR logic and the comparator is used. The time-domain comparator with a offset calibration technique is used to achieve a high resolution. To reduce the power consumption and area, a split capacitor-based differential DAC is used. The designed asynchronous SAR ADC is fabricated by using a 0.18 um CMOS process, and the active area is $420{\times}140{\mu}m^2$. It consumes the power of 0.818 mW with a 1.8 V supply and the FoM is 91.8 fJ/conversion-step.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.634-637
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• 2005

Multichannel seismic data acquired in Ulleung Basin of East Sea for gas hydrate exploration. The seismic sections of this area show strong BSR(bottom simulating reflections) associated with methane hydrate occurrence in deep marine sediments. Very limited information is available from deep sea drilling as the risk of heating and destabilizing the initial hydrate conditions during the processing of drilling is considerably high. Not so many advanced status of gas hydrate exploration in Korea, the most of information of gas hydrate characteristics and properties are inferred from seismic reflection data. In this study, The AVO analysis using the long offset seismic data acquired in Ulleung Basin used to explain the characteristics and structure of gas hydrate. It is used primarily P-wave velocity accessible from seismic data. To make a good quality of AVO analysis input data, seismic preprocessing including 'true gain correction', 'source signature deconvolution', twice velocity analysis and some kinds of multiple rejection and enhancing the signal to noise ratio processes is carried out very carefully. The results of AVO analysis, the eight kinds of AVO attributes are estimated basically and some others of AVO attributes are evaluated for interpretation of AVO analysis additionally. The impedance variation at the boundary of gas hydrate and free gas is estimated for investing the BSR characteristics and properties. The complex analysis is performed also to verifying the amplitude variation and phase shift occurrence at BSR. Type III AVO anomaly appearance at saturated free gas area is detected on BSR. It can be an important evidence of gas hydrate deposition upper the BSR.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.542-545
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• 2005

Spaceborne radar interferometry has been widely used to estimate the topography and deformation of the Earth. It is difficult to obtain coherent interferometric SAR pairs especially over coastal areas mainly because of variation of surface conditions. We carried out the experiment using a cross-interferometric pair with a perpendicular baseline of about 1.4 km, a 30 minutes temporal separation and the height sensitivity of about 6 meters. The temporal decorrelation can be reduced by the cross interferometric technique with a 30 minutes temporal separation. Accurate coregistration was performed through resampling of ENVISAT ASAR data to equivalent pixel spacing to the ERS SAR data, because of the differences of the pulse repetition frequency and range sampling rate between the two sensors. Then we estimated range and azimuth offset to a sub-pixel accuracy using image intensity cross correlation. A larger window chip size than a general case was used because it was difficult to distinguish typical features. As range bin increased, the difference of Doppler centroid also increased. It resulted in lower coherence in far range than in near range. Coherences over wetland in near and far range were about 0.8 and 0.5, respectively. The coherence was improved by applying azimuth and range common band filtering, but coherence gap still existed. ERS-ENVISAT cross-interferogram usually lost information in urban area. However, high coherence over a city in this pair was shown, because of less man-made structures than other major cities. Accuracy of the DEM constructed by the ERS-ENVISAT 30-minute pair in a coastal area is to be evaluated.