Chul Soo Lee

Hydrate phase equilibria for gas mixtures containing carbon dioxide: A proof-of-concept to carbon dioxide recovery from multicomponent gas stream

Three-phase equilibrium conditions (aqueous liquid-hydrate-vapor) of CO2-N2 binary mixtures in the temperature range of 271.75 K to 284.25 K and the pressure range of 12 to 235 bar. In addition, three-phase (aqueous liquid-hydrate-vapor) behavior for CO2-CH4 mixture were measured in the temperature range of 272 to 284 K at the constant pressures of 15, 20, 26, 35 and 50 bar. In high concentration of CO2, upper quadruple points were also measured. The obtained data indicates that three-phase equilibrium temperatures become higher with increasing concentration of CO2. For the prediction of three-phase equilibrium, the vapor and liquid phases were treated by employing the Soave-Redlich-Kwong equation of state (SRK-EOS) with the second order modified Huron-Vidal (MHV2) mixing rule and the hydrate phase with the van der Waals-Platteeuw model. The calculated results showed good agreement with experimental data. The concentration of vapor and hydrate phases was also determined experimentally. This work can be used as the basic data for selective separation process by hydrate formation.

Region-of-interest coding based on set partitioning in hierarchical trees

In many image coding applications, such as Web browsing, image database and telemedicine, it is useful to reconstruct only a region of interest (ROI) before the rest of the image is reconstructed. An ROI coding functionality is incorporated with the set partitioning in hierarchical trees (SPIHT) algorithm (see Said and Pearlman, IEEE Trans. Circuits and Systems for Video Technology, vol.6, p.243-50, 1996). By emphasizing the ROI coefficients, they are coded with higher fidelity than the rest of the image in early stages of progressive reconstruction. The main thrust of this research is how to identify necessary coefficients for the decoder to reconstruct the desired region. The proposed method provides better performance than the previous method.

Computer-aided diagnostic system for breast cancer by detecting microcalcifications

X-ray mammography is an important diagnostic imaging modality for early detection of breast cancer. The early detection of the breast cancer can reduce the mortality of middle-aged women, especially in the developed country. Computer aided diagnosis (CAD) technologies have been developed to assist radiologists to detect breast cancer in early stage. This paper presents a KCAD (KAIST Computer-Aided Diagnosis) system for detection of breast cancer, which consists of personal computer, high resolution X-ray film scanner, high-resolution display and application softwares. There are three algorithms implemented in the application softwares. The first algorithm is the enhancement of the digitized X-ray mammograms based on the gradient operation. The second algorithm is to detect the clustered microcalcifications based on the statistical texture analysis, which is called surrounding region dependence method (SRDM). The SRDM matrix is computed for each ROI, which has 128 by 128 pixels. The SRDM matrix characterizes the small and high-density regions in mammograms, which can be recognized as microcalcifications. Four textural features are computed from the SRDM matrix. Using these features, the neural network classifies the regions as normal or microcalcification region. The third algorithm is the classification of the clustered microcalcifications as malignant or benign based on the shape analysis. The microcalcifications are segmented using SRDM. Four shape features are extracted from each microcalcification and five representatives are computed for each shape feature. Twenty-one shape-based values containing the number of microcalcifications are used to classify the region as malignant or benign. These algorithms are verified by real experiments.

A multiresolutional coding method based on SPIHT

We propose a new method to code still images with multiresolutional coding functionality. This algorithm is based on set partitioning in hierarchical trees (SPIHT) (IEEE Trans. Circuits Systems Video Technol. 6 (3) (1996) 243). We consider each subband as a region of interest and encode it using a region of interest (ROI) coding scheme proposed by the authors. The ROI coding scheme introduced a new parent ROI mask and multiple lists of insignificant pixels and multiple lists of insignificant sets. The proposed multiresolutional coding handles multiple ROIs, each of which corresponds to each subband of the wavelet-transformed image. Although the PSNR performance of the proposed multiresolutional coding at low rates is inferior to the original SPIHT algorithm, it provides multiresolutional coding functionality. We analyzed the rate-distortion performance and the computation time of the multiresolutional coding with respect to various bit-rates.

A real-time encoding/decoding system (REDS) for HDTV editing

A programmable and scalable parallel architecture is proposed for the real-time encoding/decoding of HDTV images and for nonlinear editing of the compressed video data. It only uses the intra-mode compression/decompression so that nonlinear editing can be performed easily and high-quality images can be recovered. Spatially partitioned image data are concurrently processed by multiple parallel processing units (PUs). Each PU consists of a programmable parallel digital signal processor, called multimedia video processor (MVP; TMS320C80), and reconfigurable field programmable logic devices (FPLDs). The performance of the REDS is described in terms of the required MVP cycles for transform coding and the FPLDs throughput for entropy coding. Robust rate distortion-optimized quantization matrices for HDTV images are presented.

Progressive coding of error-diffused bilevel images

We propose a new method to compress error-diffused bilevel images with resolution scalability. This method is a combina- tion of inverse halftoning and rehalftoning. For the inverse halfton- ing, we combine 232 dots into a single pixel of a resolution-reduced image, where each pixel has a multilevel value of 0, 1, 2, 3, and 4. After the inverse halftoning, the resolution-reduced multilevel image is halftoned by using an error diffusion algorithm. Thus, the resolu- tion of the error-diffused bilevel images can be reduced by repetition of the inverse halftoning and rehalftoning processes. After reducing the image size, we encode an error-diffused bilevel image progres- sively from the lowest resolution image to the highest resolution image. To encode higher resolution images, we use the information in the previously coded lower resolution image. Though the com- pression ratios of the proposed algorithm are similar to those of progressive Joint Bilevel Image Processing Group (JBIG), the image quality of the resolution-reduced image from the proposed algorithm is much better than that from the progressive JBIG.

Progressive coding of error diffused images

We propose a new method to compress error diffused images with spatial scalability. This method is a kind of combination of inverse halftone and rehalftone. During inverse halftoning, we combine four dots into a pixel of a reduced image. Then, the reduced image is rehalftoned using an error diffusion algorithm. We encode an error diffused image progressively from the lowest resolution image to higher resolution image. To code higher resolution images, we use the dots in the previously coded lower resolution image. The compression ratios of the proposed algorithm are similar to those of the JBIG (Joint Bilevel Image Processing Group) progressive mode. However, the reduced image quality from the proposed algorithm is better than that from the JBIG progressive mode.

A Multiresolutional Coding Method Based on SPIHT

In this work, we incorporate a multiresolutional coding functionality into the SPIHT algorithm [1]. The multiresolutional coding can be considered as a kind of the region of interest (ROI) coding with multiple regions of interest. Therefore, the ROI coding proposed by authors can be extended for the multiresolutional functionality without any cost in performance. The parent of ROI (PROI) and the multiple lists for insignificant sets and pixels, which were proposed for the ROI coding, are also used for the multiresolution coding.

A real-time encoding and decoding system for nonlinear HDTV editor

A real‐time encoding and decoding system (REDS) for HDTV that can be used for nonlinear HDTV editing in studio has been developed. The intrapicture coding of motion JPEG is implemented and optimized in the REDS so that a high‐quality image can be recovered for the nonlinear editing. The REDS has a parallel architecture with multiple programmable digital signal processors (DSP) and reconfigurable field programmable logic devices (FPLD). The HDTV image is spatially partitioned and concurrently processed by the multiple processors. The programmable DSPs perform the discrete cosine transform and quantization to reduce the spatial redundancy of the HDTV image, whereas the FPLDs perform the variable length coding to reduce the statistical redundancy. In addition, field‐based quantization matrices are developed for HDTV images. The REDS has the programmability and the random accessibility of image frames, the two most important features for a nonlinear HDTV editing system.