• Journal of radiological science and technology
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• v.45 no.5
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• pp.397-405
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• 2022

Computed radiography (CR) systems, which convert an analog signal recorded on a cassette into a digital image, combine the characteristics of analog and digital imaging systems. Compared to digital radiography (DR) systems, CR systems have presented difficulties in evaluating system performance because of their lower detective quantum efficiency, their lower signal-to-noise ratio (SNR), and lower modulation transfer function (MTF). During the step of energy-storing and reading out, a baseline offset occurs in the edge area and makes low-frequency overestimation. The low-frequency offset component in the line spread function (LSF) critically affects the MTF and other image-analysis or qualification processes. In this study, we developed the method of baseline correction using mathematical morphology to determine the LSF and MTF of CR systems accurately. We presented a baseline correction that used a morphological filter to effectively remove the low-frequency offset from the LSF. We also tried an MTF evaluation of the CR system to demonstrate the effectiveness of the baseline correction. The MTF with a 3-pixel structuring element (SE) fluctuated since it overestimated the low-frequency component. This overestimation led the algorithm to over-compensate in the low-frequency region so that high-frequency components appeared relatively strong. The MTFs with between 11- and 15-pixel SEs showed little variation. Compared to spatial or frequency filtering that eliminated baseline effects in the edge spread function, our algorithm performed better at precisely locating the edge position and the averaged LSF was narrower.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.31-36
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• 2002

A continuous tool-path, that is to cut continuously with the minimum number of cutter retractions during the cutting operations, is developed in order to minimise the fluctuation of cutting load and the possibility of chipping on the cutting edge in HSM (high-speed machining). This algorithm begins with the offset procedure along the boundary curve of the sculptured surface being machined. In the of offset procedure, the offset distance is determined such that the scallop height maintains a constant roughness to ensure higher levels of efficiency and quality in high-speed machining. Then, the continuous path is generated as a kind of the diagonal curve between the offset curves. This path strategy is able to connect to neighbor paths without cutter retractions. Therefore, the minimum tool retraction tool-path can be generated And, it allows the sculptured surface incorporating both steep and flat areas to be high-speed machined.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.698-704
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• 2013

The image process for image enhancement applies differently the same algorithm for each application. So, the optimized value for each application is required. In this paper, the X-ray medical image using a high-pass filter was improved edges. The result image was improved edge and the contrast of flat area using a constant multiplier and offset. Therefore, the high-frequency emphasis filter optimized for medical image is required. These optimized values are the gaussian high-pass filter, the distance of cutoff frequency=0.05 and offset=0.5. From the result of optimaized simulation, The proposed method has enhanced contrast and edge of the image in the contrast of existing mothods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.662-672
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• 2011

This paper presents a new edge-preserving algorithm and its VLSI architecture for block artifact reduction. Unlike previous approaches using block classification, our algorithm utilizes pixel classification to categorize each pixel into one of two classes, namely smooth region and edge region, which are described by the edge-preserving maps. Based on these maps, a two-step adaptive filter which includes offset filtering and edge-preserving filtering is used to remove block artifacts. A pipelined VLSI architecture of the proposed deblocking algorithm for HD video processing is also presented in this paper. A memory-reduced architecture for a block buffer is used to optimize memory usage. The architecture of the proposed deblocking filter is prototyped on FPGA Cyclone II, and then we estimated performance when the filter is synthesized on ANAM 0.25 ${\mu}m$ CMOS cell library using Synopsys Design Compiler. Our experimental results show that our proposed algorithm effectively reduces block artifacts while preserving the details.

• Journal of Sensor Science and Technology
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• v.28 no.3
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• pp.164-170
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• 2019

In this paper, a lane detection and tracking algorithm based on vision sensors and employing a robust filter for inner edge detection is proposed for developing a lane departure warning system (LDWS). The lateral offset value was precisely calculated by applying the proposed filter for inner edge detection in the region of interest. The proposed algorithm was subsequently compared with an existing algorithm having lateral offset-based warning alarm occurrence time, and an average error of approximately 15ms was observed. Tests were also conducted to verify whether a warning alarm is generated when a driver departs from a lane, and an average accuracy of approximately 94% was observed. Additionally, the proposed LDWS was implemented as an embedded system, mounted on a test vehicle, and was made to travel for approximately 100km for obtaining experimental results. Obtained results indicate that the average lane detection rates at day time and night time are approximately 97% and 96%, respectively. Furthermore, the processing time of the embedded system is found to be approximately 12fps.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.215-220
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• 2008

A microchannel PCHE is manufactured by the two technologies of micro photo-etching and diffusion bonding. In this paper, heat transfer and pressure drop characteristics by applying various configuration for the flow channel in the microchannel PCHE is experimentally investigated. The flow channel configurations are designed three types such as straight, wavy and offset strip channels. The performance experiment of each configuration is performed for Reynolds numbers in ranges of $100{\sim}700$ under various flow conditions for the hot side and the Reynolds number of cold side is fixed at 350. The inlet temperatures of the hot side and cold side are conducted as $40^{\circ}C$ and $20^{\circ}C$, respectively. The heat transfer performance of wavy channel, which was similar to that of offset strip channel, was much higher than that of straight channel. The effectiveness of wavy channel and offset strip channel was evaluated as about $0.5{\sim}0.9$. The pressure drop of wavy channel was highest among configurations and that of offset strip channel was lower than that of straight channel because the round curved surface of each strip edge was reduced the pressure loss.

• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.212-221
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• 2003

In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. A new rapid prototyping process, transfer-type variable lamination manufacturing process by using expandable polystyrene foam (VLM-ST), has been developed to reduce building time, apparatus cost and additional post-processing. At the same time, VLM Slicer, the CAD/CAM software for VLM-ST has been developed. In this study, algorithms for accuracy improvement of VLM-ST, which include offset and overrun of a cutting path and generation of a reference shape are developed. Offset algorithm improves cutting accuracy, overrun algorithm enables the VLM-ST process to make a shape of sharp edge and reference shape generation algorithm adds additional shape which makes off-line lamination easier. In addition, proposed algorithms are applied to practical CAD models for verification.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.468-470
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• 2012

본 논문에서는 High Efficiency Video Coding (HEVC)을 하드웨어로 구현하기 위해서 파이프라인 방식을 인-루프 필터에 새롭게 도입된 기술인 Sample Adaptive Offset (SAO)에 적용하여 병렬화 처리하는 방법을 제안한다. 현재 HEVC 에서 SAO 의 입출력이 프레임단위로 구현되어 있는데, 이를 파이프라인 방식의 하드웨어 설계시에는 Largest Coding Unit(LCU)단위로 입출력이 가능하도록 수정해야 한다. SAO 에서 사용하는 두 가지 방식으로 Edge Offset(EO)과 Band Offset(BO)모드가 있으며, 이 중 EO 모드가 주변 화소값을 이용하므로 주변 화소값 정보가 없는 LCU 경계에 위치한 화소들을 버퍼에 저장한 뒤, 다음 LCU 블록의 입력과 함께 SAO 를 수행한다. 또한, SAO 앞 단의 인-루프 필터 기술인 디블록킹 필터(Deblocking Filter)에서도 LCU 단위로 입출력이 수행되므로 디블록킹 필터에서 저장하는 버퍼를 고려하면, SAO 입력에서 사용가능한 데이터는 LCU 가 천이된 형태가 된다. 따라서 SAO 입력의 천이된 형태와 버퍼 사용에 따라 총 9 가지 타입을 갖게 되며, 이 중 경계에 위치한 블록을 제외한 타입들의 경우 서로 다른 정보를 가진 SAO 를 4 번 수행해야 한다. 이러한 점을 반영한 파이프라인 방식을 SAO 에 적용하여 하드웨어에 적합한 구조를 구현할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2719-2730
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• 2009

In this paper, we implement the measurement functionality for performance measurements of EDGE (Enhanced Data Rates for GSM Evolution) terminal by using software. Generally speaking, the receiving algorithms in normal MODEM cannot be used directly to a measurement system due to the lack of accuracy. Therefore, we propose a new receiver algorithm for precise EDGE signal measurements. In the proposed algorithm, 2-stage (coarse stage, fine stage) parameters estimation (symbol-timing, frequency offset, carrier phase) scheme is used. To improve the estimation accuracy, we increase the number of the received signal samples by interpolation. The proposed EDGE signal measurement algorithm can be used for verifying the hardware measurement system, and also can be used for the commercial systems through software optimization.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.54-60
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• 2015

Laser-arc hybrid welding has been considered as an effective pipe girth welding process since early 2000's. Tolerance for fit-up offsets such as gap and edge misalignment is one of most important requirements in pipe girth laser-arc hybrid welding, and several approaches using parameter optimization, a laser beam scanning and an arc oscillation have been tried. However the required offset tolerance has not been fully accomplished up to now and laser-arc hybrid welding has not been widely applied in pipeline construction than expected, despite of its high welding speed and deep penetration. In this study, internal welding was adopted to ensure the offset tolerance and sound back bead. The effect of welding parameters on bead shape was investigated at the flat position. Also tolerances for gap and edge misalignment were verified as 0.5 mm and 2.0 mm, respectively. The position welding trials were conducted at several welding positions from the flat to the overhead position in a downward direction. With the fixed welding speed, arc current for gas metal arc welding current and laser output power, adequate welding voltages for gas metal arc welding were suggested for each position.