• Journal of the Korean earth science society
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• v.32 no.6
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• pp.575-585
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• 2011

The effect of wavelet pair choice in the compression of the satellite images is studied. There is a trade-off between compression rate and perception quality. The encoding ratio is used to express the compression rate, and Peak Signal-to-Noise Ratio (PSNR) is also used for the perceptional performance. The PSNR and the encoding ratio are not matched well for the images with various wavelet pairs, but the tendency is remarkable. It is hard to find the pattern of PSNR for sampled images. On the other hand, there is a pattern of the variation range of the encoding ratio for each image. The satellite images have larger values of the encoding ratio than those of nature images (close range images). Depending on the wavelet pairs, the PSNR and the encoding ratio vary as much as 13.2 to 21.6% and 16.8 to 45.5%, respectively for each image. For Synthetic Aperture Radar (SAR) images the encoding ratio varies from 16 to 20% while for the nature images it varies more than 40% depending on the choice of wavelet pairs. The choice of wavelet for the compression affects the nature images more than the satellite images. With the indices such as the PSNR and the encoding ratio, the satellite images are less sensitive to the choice of wavelet pairs. A new index, energy concentration ratio (ECR) is proposed to investigate the effect of wavelet choice on the satellite image compression. It also shows that the satellite images are less sensitive than the nature images. Nevertheless, the effect of wavelet choice on the satellite image compression varies at least 10% for all three kinds of indices. However, the important of choice of wavelet pairs cannot be ignored.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2615-2628
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• 1997

In this paper, a new codebook design algorithm is proposed. It uses a DCT map based on two-dimensional discrete cosine of transform (2D DCT) and finite state vector quantizer (FSVQ) when the vector quantizer is designed for image transmission. We make the map by dividing input image according to edge quantity, then by the map, the significant features of training image are extracted by using the 2D DCT. A master codebook of FSVQ is generated by partitioning the training set using binary tree based on tree-structure. The state codebook is constructed from the master codebook, and then the index of input image is searched at not master codebook but state codebook. And, because the coding of index is important part for high speed digital transmission, it converts fixed length codes to variable length codes in terms of entropy coding rule. The huffman coding assigns transmission codes to codes of codebook. This paper proposes single-side growing huffman tree to speed up huffman code generation process of huffman tree. Compared with the pairwise nearest neighbor (PNN) and classified VQ (CVQ) algorithm, about Einstein and Bridge image, the new algorithm shows better picture quality with 2.04 dB and 2.48 dB differences as to PNN, 1.75 dB and 0.99 dB differences as to CVQ respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.8
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• pp.113-118
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• 2016

In this paper, a read-in integrated circuit (RIIC) for IR scene projectors (IRSPs) adopting a sub-frame control technique is proposed, which minimizes the reduction of the apparent temperature of the IR images projected from IRSPs operating at a frame rate of 30 Hz. The proposed sub-frame control technique significantly reduces the amount of scene data loss on capacitors, which is caused by leakage currents flowing through MOSFET switches during holding periods, by dividing a unit frame into 8 sub-frames and refreshing the same scene data for each sub-frame. A current-drive RIIC was designed for the higher apparent temperature of IR radiated from the emitter, and it receives the scene data as a form of analog voltages from an external DAC. A prototype chip with a $64{\times}32$ RIIC array was fabricated using Magnachip/SKhynix $0.35{\mu}m$ 2-poly 4-metal CMOS process, and the measured maximum output data current is $230.3{\mu}A$. This amount of current ensures the projection of IR images whose maximum apparent temperature is $366.2^{\circ}C$ in the mid-wavelength IR (MWIR) when applied to a prototype emitter having a resistance of $15k{\Omega}$.

• Journal of Radiation Protection and Research
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• v.37 no.1
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• pp.25-34
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• 2012

To know which parameters were acceptable for achieving lowest radiation exposure to the patients and highest image quality at the diagnostic X-ray radiography, we measured the patient radiation dose and image quality in transmitted PACS (Picture Archiving and Communication System) at variable combinations of the added filters. As a result, the Dose Area Product (DAP: $mGy{\cdot}cm^2$) and Entrance Surface Doses (ESDs: $mGy$) was lowest at 1 mmAl + 0.2 mmCu and highest at 0 mmAl. The histogram of the image quality by transmitted PACS was not significantly different at variable combinations of exposure parameters on the MATLAB. In conclusion, this study can be helpful for expecting radiation dose-exposure and control exposure parameters for the diagnostic X-ray radiography.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.162-162
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• 2020

토양수분은 TDR(Time Domain Reflectometry)이나 Tensiometer 등의 장비를 이용하여 측정을 시행하고 있으나, 이를 위해서는 많은 인력과 경제적 자원이 소비될 뿐만 아니라 시공간적으로 측정할 수 있는 범위에 한계가 있다. 지상 관측의 대안으로 MIRAS(Microwave Imaging Radiometer with Aperture Synthesis)나 SMAP(Soil Moisture Active Passive), AMSR2(Advanced Microwave Scanning Radiometer 2) 등의 수동 마이크로파 위성 센서를 이용한 공간 토양수분 관측이 수행되었으나, 낮은 공간 해상도(9~36km)는 지역 규모의 토양수분 분포를 나타내기 충분하지 않고, 높은 불확실성을 내포하고 있다. 본 연구에서는 금강 상류의 용담댐 유역(930.0㎢)을 대상으로 Sentinel-1 C-band SAR(Synthetic Aperture Radar) 영상을 이용한 토지 피복 및 토양 속성을 고려한 10m 해상도의 토양수분 산출을 수행하였다. 용담댐 유역은 산림 79.7%, 논 9.0%, 밭 5.4%, 주거지 2.9%의 토지 피복 비율을 가지며 토양은 사양토(66.6%)와 양토(20.9%)가 우세하다. Sentinel-1 C-band SAR 영상은 SeNtinel Application Platform(SNAP)을 이용하여 전처리 후, 후방산란계수로 변환하였다. 토양수분 알고리즘은 TU-Wien change detection algorithm과 Regression model을 활용하였고, 검증을 위한 실측 토양수분 자료는 한국수자원공사(K-water)에서 제공하는 5년(2014~2018)간의 토양수분 관측자료를 이용하였다. 산출된 토양수분은 결정계수(Coefficient of determination, R²) 및 평균제곱근오차(Root Mean Square Error, RMSE)를 이용하여 실측 토양수분과 비교하였다. Sentinel-1 C-band SAR 영상을 이용한 고해상도의 토양수분 산출은 토지 피복 및 토양 속성을 고려한 지역 규모의 공간 토양수분 분포 및 시간적 변화를 표현 가능할 것으로 판단된다.

• Journal of the Korean Society of Radiology
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• v.79 no.5
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• pp.254-258
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• 2018

Purpose: Establishment of an appropriate protocol for breast magnetic resonance imaging (MRI) in the study of image quality standards to enhance the effectiveness of medical image information exchange, which is part of the construction and activation of clinical information exchange for healthcare informatization. Materials and Methods: The recommended protocols of breast and MRI scans were reviewed and the questionnaire was prepared by a responsible researcher. Then, a panel of 9 breast dedicated radiologists was set up in Korea. The expert panel conducted a total of three Delphi agreements to draw up a consensus on the breast MRI protocol. Results: The agreed breast MRI recommendation protocol is a 1.5 Tesla or higher device that acquires images with prone position using a breast dedicated coil and includes T2-weighted and pre-contrast T1-weighted images. Contrast enhancement images are acquired at least two times, and include 60-120 seconds between images and after 4 minutes. The contrast enhancement T1-weighted image should be less than 3 mm in thickness, less than 120 seconds in temporal resolution, and less than $1.5mm^2$ in-plane pixel resolution. Conclusion: The Delphi agreement of the domestic breast imaging specialist group has established the recommendation protocol of the effective breast MRI.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.363-364
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• 2009

초소형 영상 분광기 COMIS는 과학기술위성3호에 탑재되어 지표면 및 대기의 분광 촬영을 할 예정으로 개발되고 있다. COMIS는 궤도 700km 상공에서 약 30m의 해상도 및 30km의 관측 폭을 갖고 있으며, 가시광 및 근적외선 영역에서 $16{\sim}62$대역($2{\sim}15nm$ 파장 분해능)의 초분광 관측을 수행할 수 있다. COMIS는 CCD 등의 일부 전자 부품 단위에서의 수입을 제외하곤 설계, 제작 및 평가를 포함한 모든 개발이 국내의 연구진 및 업체에 의하여 진행되고 있다. COMIS는 2010년 말 발사를 목표를 개발되고 있으며, 현재 시험 모델 개발이 진행 중에 있다. 본 논문에서는 현재 진행 중인 시험 모델의 개발 현황을 보고한다.

• Current Industrial and Technological Trends in Aerospace
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• v.6 no.2
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• pp.125-132
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• 2008

High speed camera is very important and essential device to analyze the motion of fast moving object in detail. This paper describes the basic concepts of the high speed film camera and high speed digital camera and the history and future technical trends in high speed camera industry. In addition, application field of high speed camera in Korea as well as other countries and future plan to use high speed camera in Naro Space Center has been descried.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.107-114
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• 2003

The influence of property difference in refraction index on micro PIV measurement of two-fluid flow in a microchannel was analyzed. The difference of measurement planes in two fluids would bring misunderstanding of the physics. The objective-imaging system for two-fluid flow measurement was presented, and the condition for measurement of valid velocity profile across two-fluid interface was derived. A micro PIV experimental system was set up to measure two-fluid flow inside a Y-shape microchannel. Under the conditions, three cases of two-fluid flow of glycerol solutions at different concentration (${\phi}$), e.g., (${\phi}=0\;and\;{\phi}=0.2,\;{\phi}=0.1\;and\;{\phi}=0.5,\;{\phi}=0\;and\;{\phi}=0.6$, were measured. Close agreement of experimental and numerical results was found.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.269-272
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• 2005

For the efficient image encryption, we proposed the encryption algorithm using the chaotic function and elementary matrix operation defined on the bit plane decomposition. Though the chaotic encryption algorithm is faster than block encryption, it uses a real number computation. In this sense, we use the row and column operations on the bit-plane decomposed images combined with logistic function for the recursive rounding number, too.