• Journal of Biomedical Engineering Research
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• v.19 no.4
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• pp.361-367
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• 1998

We student tow image characteristics, the smoothness and the similarity, which give rise to local and global redundancy in image representation. The smoothness means that the gray level values within a given block vary gradually rather than abruptly. The similarity means that any patterns in an image repeat itself anywhere in the rest of the image. In this sense, we proposed a lossless medical image compression scheme which exploits both types of redundancy. The proposed method segments the image into variable size blocks and encodes them depending on characteristics of the blocks. The proposed compression schemes works better 10~40[%] than other compression scheme such as the Huffman, the arithmetic, the Lempel-Ziv, HINT(Hierachical Interpolation) and the lossless scheme of JPEG with one predictor.

• Korean Journal of Optics and Photonics
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• v.33 no.1
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• pp.22-27
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• 2022

We fabricate a polarization-independent dielectric multilayer thin-film diffraction grating for a spectral-beam-combining (SBC) system with a simple grating structure and low aspect ratio. Due to the refractive index and thickness error of the manufactured thin films, the diffraction efficiency of the fabricated diffraction grating was lower than that of the design. The causes of the errors were analyzed, and it was confirmed through simulation that diffraction efficiency could be compensated through an additional coating on the manufactured diffraction grating. As a result of sputtering an additional Ta₂O₅ layer on a fabricated diffraction grating, the diffraction efficiency was corrected and a maximum 91.7% of polarization-independent diffraction efficiency was obtained.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.83-89
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• 2012

Recently, due to widespread use of smartphones, the number of applications of the QR code is increased rapidly. QR codes, a kind of 2-dimensional barcode, is used to encode information such as simple URLs or namecards, especially for corporates' advertisement. Users can get some information easily by taking picture of the target QR code, however, fake or altered QR codes can cause serious problems, e.g., URL hijacking or infringement of private information because no one can identify the buried information in the QR code by his naked eye. In this paper, I summarize threats to the QR code and present how to tackle these threats.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.7
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• pp.45-52
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• 2005

This paper is studied on boost AC-DC converter of high power factor and high efficiency for discontinuous current control. The converter operated in discontinuous current control eliminates the complicated circuit control requirement, and reduces a number of components. The input current waveform in proposed circuit is got to be a discontinuous sinusoidal form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control circuit is simple. Also the switching devices in a proposed circuit are operated with soft switching by the partial resonant method. The result is that the switching loss is very low and the efficiency of system is high. The partial resonant circuit makes use of a inductor using step up and loss-less snubber capacitor. The circuit topology of the converter is simplified. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.1 s.307
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• pp.45-52
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• 2006

In this paper, authors propose a step-up converter of pulse width modulation (PWM) and power factor correction (PFC) by using a novel loss-less snubber. The proposed converter for a discontinuous conduction mode (DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Thereupon, the input power factor is nearly unity and the control method is simple. In the general DCM converters, the switching devices are fumed-on with the zero current switching (ZCS), and the switching devices must be switched-off at a maximum reactor current. To achieve a soft switching (ZCS and ZVS) of the switching turn-off, the proposed converter is constructed by using a new loss-less snubber which is operated with a partial resonant circuit. The result is that the switching loss is very low and the efficiency of converter is high. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2008.12a
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• pp.111-118
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• 2008

1. 고추 무농약재배 비가림 시설재배 효과 무농약 고추 노지 터널재배와 비가림 재배의 수량성을 검토하고, 관행 비가림 시설에 측고와 동고를 높이고 가로대를 보강하여 최소한의 투입으로 작물재배 환경을 개선으로 농작업에 편리성을 도모하고자 시험을 수행한 결과 비가림 시설재배가 노지 터널재배에 비하여 생육이 양호하고. 수량이 2배정도 많았다. 노지재배 고추는 강우로 인하여 탄저병이 40% 정도 발생되었으나, 비가림 시설재배는 탄저병과 역병이 전혀 발생되지 않았다. 2. 고추 비가림 시설 환경 개선 효과 구명 비가림 시설의 측과와 동고를 높이는 간단한 환경개선으로 여름철은 시설내 온도가 관행 비가림 시설보다 낮아지는 효과가 있었다. 또한 비가림 시설환경 개선에 의해서 "녹광" 풋고추의 생육은 증가되었으며, 홍고추 "조양" 품종도 같은 경향이었다. 고추의 수량은 풋고추 "녹광" 품종이 홍고추 "조양" 품종보다 수확량이 현저하게 많았고 처리간에는 비가림 시설의 환경을 개선한 시설이 관행 비가림 시설에 비하여 증수되었다. 그리고 비닐온실의 측고를 높인 결과 비닐 온실 내 측면으로 사람의 통행이 자유로워 작업환경 도도 개선되었다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.63-71
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• 2000

A new type of second-order digital peaking filters for professional-quality digital audio system is proposed whose frequency response can be elaborately controlled throughout the composite structure of a standard band-pass filter and a 0-dB bypass gain. The proposed method for designing the peaking filter uses the Q-compensation technique to prevent the Q-distortion caused by the variation of the gain factor and is reduced into a compact form which is proper to the real-time implementation. Methods are examined for computing its coefficients, which are exact and very straightforward to compute with small amount of the system resources.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.585-597
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• 2008

The aim of this study was to find an analytic solution to the problem of determining the optimal capacity (lot-size) of a batch-storage network to meet demand for a finished product in a system undergoing random failures of operating time and/or batch material. The superstructure of the plant considered here consists of a network of serially and/or parallel interlinked batch processes and storage units. The production processes transform a set of feedstock materials into another set of products with constant conversion factors. The final product demand flow is susceptible to short-term random variations in the cycle time and batch size as well as long-term variations in the average trend. Some of the production processes have random variations in product quantity. The spoiled materials are treated through regeneration or waste disposal processes. All other processes have random variations only in the cycle time. The objective function of the optimization is minimizing the total cost, which is composed of setup and inventory holding costs as well as the capital costs of constructing processes and storage units. A novel production and inventory analysis, the PSW (Periodic Square Wave) model, provides a judicious graphical method to find the upper and lower bounds of random flows. The advantage of this model is that it provides a set of simple analytic solutions while also maintaining a realistic description of the random material flows between processes and storage units; as a consequence of these analytic solutions, the computation burden is significantly reduced.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2409-2416
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• 2015

This paper presents an orientation-based adaptive prediction method for effective lossless image compression. For a robust prediction, the proposed method estimates the directional information and the property near the current pixel in a support region-based fashion, not a pixel-based one which is sensitive to a small variation. We improve the prediction performance effectively by selection of the prediction pixel adaptively according to the similarity between support regions of the current pixel and the neighboring pixels. Comprehensive experiments demonstrate that the proposed scheme achieves excellent prediction performance measured in entropy of the prediction error compared to a number of conventional prediction methods such as MED, GAP, and EDP. Moreover the complexity of the proposed algorithm measured by average execution time is low compared to MED which is the simplest prediction method.

• Journal of Convergence for Information Technology
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• v.8 no.4
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• pp.109-114
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• 2018

In general, the simple items we need to live in are purchased through retail stores such as supermarkets near our home. In the store, not only the items but also the management personnel and the payment instruments for the store management are located in one space called the store. Such a general store environment is gradually changing into an 'unmanned market' as a result of the development and fusion of information and communication technology (ICT). An unmanned market is an environment in which no one runs a market as the word has. An example of a typical change is Amazon's Unofficial Amazon Store. In addition, the usage and prospects of unmanned market in China are growing very meaningfully. In this study, the present situation of the unmanned market is examined in the US and China markets, and the development prospects are described. It also describes the key milestones necessary for the unmanned market.