Choon-Woo Kim

Effects of green tea extract administration on the pharmacokinetics of clozapine in rats.

The pharmacokinetic interaction between clozapine, an atypical antipsychotic with metabolic complications, including weight gain, and green tea consumption has not been evaluated, although green tea is responsible for beneficial effects, including weight reduction, and is widely consumed in the world. Commercial green tea extract (175 mg kg−1) or saline was administered orally for 4 days before the oral administration of clozapine (20 mg kg−1) to rats. Plasma concentrations of clozapine were measured up to 5 h after clozapine administration, and then hepatic CYP1A2 expression and activity were determined. There was no significant difference in the elimination half‐life of clozapine between the green tea extract and saline groups. However, the time to reach peak concentration (Tmax) was significantly increased by green tea extract. The mean total area under the plasma concentration‐time curve (AUC0‐∞) and maximal peak plasma concentration (Cmax) of clozapine in the green tea extract group were significantly lower than those of controls. Green tea extract induced a ∼2‐fold increase in hepatic CYP1A2 levels, while the activity increased slightly (by 10% of control). Because of this reduction in AUC and Tmax of clozapine by green tea extract pretreatment, we suggest that both the rate and amount of absorption of clozapine may be reduced by green tea extract, although the hepatic elimination phase may not be significantly altered. Therefore, the clinical implications of the effects of green tea on the bioavailability of clozapine in patients should be further evaluated.

An Efficient Frame Rate Up-Conversion Method for Mobile Phone with Projection Functionality

Mobile phones with the built-in projection functionality are about to be introduced in market. In order to achieve high visual quality in mobile projection, an efficient frame rate up-conversion is proposed in this paper. Computational complexity and size of memoty resources are important factors in mobile applications. The proposed motion estimation algorithm utilizes adaptive block size and search window according to motion activity levels. In order to improve accuracy of the estimated motion vectors, the two stage motion vector refinement technique is proposed. Also, the proposed method is hardware implemented. Experimental results indicate that the proposed technique exhibits better performance compared to the conventional methods .

Extraction of memory colors for preferred color correction in digital TVs

Subjective image quality is one of the most important performance indicators for digital TVs. In order to improve subjective image quality, preferred color correction is often employed. More specifically, areas of memory colors such as skin, grass, and sky are modified to generate pleasing impression to viewers. Before applying the preferred color correction, tendency of preference for memory colors should be identified. It is often accomplished by off-line human visual tests. Areas containing the memory colors should be extracted then color correction is applied to the extracted areas. These processes should be performed on-line. This paper presents a new method for area extraction of three types of memory colors. Performance of the proposed method is evaluated by calculating the correct and false detection ratios. Experimental results indicate that proposed method outperform previous methods proposed for the memory color extraction.

A real time image processor for reproduction of gray levels in dark areas on plasma display panel (PDP)

Due to the non-balanced and linear luminous characteristics of RGB color channels of plasma display panels (PDPs), it is required to determine the white point of each gray level and perform inverse gamma correction. However, the two measures cause degradation of gray level representation and undesirable false contouring in the dark areas on PDPs. We describe the implementation of a real time image processor with an error diffusion algorithm and unsharp masking operation. Experimental results show improvements of gray level representation and reduction of undesirable false contouring on the PDP.

Simulation of Blur in Transmitted Image through Transparent Plastic for Transparent OLEDs

Transparent displays have received attention as next-generation displays. When attached to transparent displays, transparent plastics can control transmission of incident lights. They can extend the use of transparent displays to various applications. The transmitted image of the background through the transparent plastic appears blurred due to the light diffusion. Major factors affecting this blurriness include the haze and background distance. In this paper, the degree of blurriness in the transmitted image is modelled by the Gaussian blur kernel. With a small set of measurements from the black-and-white patch, the standard deviations of the Gaussian blur kernel and luminance transition curves can be determined for all of the combinations of the haze and background distance. Experimental results indicate that the proposed method accurately estimates the degree of blurriness.

Content-Dependent Reduction of Static Color Breakup on Field Sequential Color LCDs

Field sequential color (FSC) LCDs form color images by sequentially displaying subfield images. Because color filter attenuating light transmission is not required, FSC LCDs can reduce power consumption considerably. However, their sequential display scheme results in undesirable color artifacts that degrade the perceived image quality. This paper proposes a new content-dependent static color breakup (CBU) reduction method for FSC LCDs with 240-Hz frame rate. In addition, two performance indices are defined to examine the effectiveness of the backlight color selections. Experimental results indicate that the proposed method effectively reduces the visibility of static CBU.

Optimum memory color extraction for digital TVs based on genetic algorithm

Perceptual image quality is one of the most important performance indicators for digital TVs. In order to provide pleasing impression on viewers, preferred color correction that modifies memory colors is often applied. The first step of the preferred color correction is to extract pixels of memory colors. This paper presents a new method to determine the optimized boundary of geometrical figures for memory color extraction. Genetic algorithm is utilized for optimization. Based on relationship between lightness and hue and/or chroma, range of lightness is subdivided into three groups. Boundary of geometrical figure is determined for each group. Performance of the proposed method is evaluated by calculating the extraction accuracies. Experimental results indicate that proposed method outperforms previous methods proposed for the memory color extraction.

An Image Analysis Technique for Exploration of Manganese Nodules

In order to develop the mineral resources contained in manganese nodules of the deep sea, the Korea Ocean Research & Development Institute (KORDI) has explored the area allocated by the United Nations in the Clarion-Clipperton Fracture Zone in the northeastern Pacific. During research cruises, the seabed surface was photographed every 30 s by the KORDI Deep Tow Imaging System (DTIS). Features such as the coverage and size distribution of manganese nodules on the photographs serve as the essential information to determine the potential mining areas. This article presents (semi)automatic procedures to extract the useful features from the photographs of the seabed surface using digital image processing techniques. The 35-mm films are first digitized by the film scanner. The depth information written on the film is then recognized to compensate for distortions due to nonuniform illumination. The nodule areas on the digitized image are recognized and separated from the background based on the characteristics o...

Estimation of error diffusion kernel using genetic algorithm

Error diffusion technique has been one of the most popular digital image halftoning methods. The quality of binary image resulting from the error diffusion technique is affected by the following three key factors; the values of error diffusion kernel, the locations of neighboring pixels for error propagation, and the quantization scheme. Among these factors, this paper is focused on the estimation of the values of error diffusion kernel. In previous efforts to propose modification to the original Floyd-Steinbergs algorithm, the values of error diffusion kernel have been determined by the trial and error method or by utilizing optimization techniques such as the least mean square estimation and neural network methods. This paper presents a new estimation method for the values of error diffusion kernel based on the genetic algorithm. Compared to the conventional optimization techniques, the genetic algorithm based approach lifts restrictions on the complexity of the error criterion for optimization. In this paper, two types of the error criteria are defined to improve image quality. They represent a measure of the reproduction of average brightness and an extent of undesirable artifacts appeared on the binary image for specific gray levels. The values of error diffusion kernel are estimated by simultaneously minimizing the defined error criteria using genetic algorithm. In the experiments, three types of error diffusion kernel are examined. The experimental results indicate that the binary images obtained based on the estimated error diffusion kernel exhibit less artifacts.

A camera-based color calibration of tiled display systems under various illumination environments

ABSTRACT Tiled display systems are widely utilized for digital signage application exceeding the size of a single flat-panel display. Smoothly varying spatial non-uniformity in luminance and color may cause visible difference in the boundary of two adjacent sub-displays. It is necessary to suppress such visible artifacts. Tiled display systems can be installed under various illumination environments and require routine color calibration to compensate for temporal change in display characteristics. This paper presents a simple and cost-effective color calibration method for tiled display systems. Consumer-level digital camera is utilized as a measuring device after the proposed vignetting correction was applied. Experimental results indicate that the proposed color calibration method for tiled display system is quite effective in suppressing the visible artifacts across two adjacent sub-displays.