• Korean Journal of Culture and Social Issue
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• v.17 no.4
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• pp.381-393
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• 2011

Eco driving is a strategy to reduce energy consumption and greenhouse gas emissions from motor vehicle. However, it has not received much attention until recently. Psychological studies on this issue have been limited and the majority of existing studies have primarily been based on engineering and educational approaches. This study examined the effects of a self-management technique on two driving behaviors: speeding and putting the gears in neutral while waiting at the signal. The self-management technique consisted of three behavior interventions: goal-setting, self-monitoring, and reward. Three drivers participated in this study. An AB multiple baseline design across participants was adopted. Results showed that the self-management technique was effective in increasing both driving behaviors. Implications of the present findings and suggestions for future research were discussed.

• Journal of the Korean Society of Radiology
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• v.84 no.2
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• pp.427-440
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• 2023

Purpose This study aimed to investigate the correlation between the fat signal fraction (FF) of the fat-dominant bone tissue of the knee joint, measured using the MRI Dixon method (DIXON) technique, and bone mineral density (BMD). Materials and Methods Among the patients who underwent knee DIXON imaging at our institute, we retrospectively analyzed 93 patients who also underwent dual energy X-ray absorptiometry within 1 year. The FFs of the distal femur metaphyseal (Fm) and proximal tibia metaphyseal (Tm) were calculated from the DIXON images, and the correlation between FF and BMD was analyzed. Patients were grouped based on BMD of lumbar spine (L), femoral neck (FN), and common femur (FT) respectively, and the Kruskal-Wallis H test was performed for FF. Results We identified a significant negative correlation between TmFF and FN-BMD in the entire patient group (r = -0.26, p < 0.05). In female patients, TmFF showed a negative correlation with FN-BMD, FT-BMD, and L-BMD (r = -0.38, 0.28 and -0.27, p < 0.05). In male patients, FmFF was negatively correlated with only FN-BMD and FT-BMD (r = -0.58 and -0.42, p < 0.05). There was a significant difference in the TmFF between female patients grouped by BMD (p < 0.05). In male patients, there was a significant difference in FmFF (p < 0.05). Conclusion Overall, we found that FF and BMD around the knee joints showed a negative correlation. This suggests the potential of FF measurement using DIXON for BMD screening.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.82-93
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• 2000

Purpose: We characterized the signals obtained from the components of a small gamma camera using Nal(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. Materials and Methods: The small gamma camera system consists of a Nal(Tl) crystal ($60{\times}60{\times}6mm^3$) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y -). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. Results: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately $8{\times}10^3$ counts/sec/${\mu}Ci$. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and $^{99m}Tc$ point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing $2{\sim}7mm$ diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.

• Journal of the Korean Society of Radiology
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• v.5 no.2
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• pp.93-96
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• 2011

Currently, the development of direct conversion radiation detector using photoconductor materials is progressing in widely. Among of theses photoconductor materials, mercuric iodide compound than amorphous selenium has excellent absorption and sensitivity of high energy radiation. Also, the detection efficiency of signal generated in photoconductor film varies by electric filed and geometric distribution according to top-bottom electrode size. Therefore, in this work, the x-ray detection characteristics are investigated about the size of top electrode in $HgI_2$ photoconductor film. For sample fabrication, to solve the problem that is difficult to make a large area film, we used the spatial paste screen-print method. And the sample thickness is $150{\mu}m$ and an film area size is $3cm{\times}3cm$ on ITO-coated glass substrate. ITO(Indium-Tin-Oxide) electrode was used as top electrode using a magnetron sputtering system and each area is $3cm{\times}3cm$, $2cm{\times}2cm$ and $1cm{\times}1cm$. From experimental measurement, the dark current, sensitivity and SNR of the $HgI_2$ film are obtained from I-V test. From the experimental results, it shows that the sensitivity increases in accordance with the area of the electrode but the SNR is decreased because of the high dark current. Therefore, the optimized size of electrode is importance for the development of photoconductor based x-ray imaging detector.

• Journal of the Korean Society of Radiology
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• v.10 no.8
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• pp.597-602
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• 2016

Recent clinical field utilizes the aluminium filter in order to reduce the low-energy photons. However, the usage of the filter can cause adverse effect on the image quality because of the scattered dose that is generated by X-ray hardening phenomenon. Further, usage of filter with improper thickness can be a reason of dose creep phenomenon where unnecessary exposure is generated towards the patient. In this study, the author evaluated the RMS and the RSD analysis in order to have a quantitative evaluation for the effect of forward scattering dose by the filter on the image. as a result of the study, the FSR and the RSD was increased together with the increasing of thickness of the filter. In this study the RSD means the standard deviation of the mean value is relatively size. It can be understood that the signal-to-noise ratio decreases when the average value is taken as a signal and the standard deviation is judged as a noise. The signal-to-noise ratio can understanding as index of resolution at image. Based on these findings, it was quantitatively verified that there is a correlation of the image quality with the FSR by using an additional filter. The results, a 2.5 mmAl which is as recommended by NCRP in the tube voltage of 70 kVp or more showed the 14.6% on the RSD when the filter was not in used. these results are considered able to be utilized as basic data for the study about the filter to improve the quality of the image.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.253-259
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• 2004

in this study, we developed a Monte Carlo imaging simulation code written by the visual C$\^$++/ programing language for design optimization of a digital X-ray imaging system. As a digital X-ray imaging system, we considered a Gd$_2$O$_2$S(Tb) scintillator and a photosensor array, and included a 2D parallel grid to simulate general test renditions. The interactions between X-ray beams and the system structure, the behavior of lights generated in the scintillator, and their collection in the photosensor array were simulated by using the Monte Carlo method. The scintillator thickness and the photosensor array pitch were assumed to 66$\mu\textrm{m}$ and 48$\mu\textrm{m}$, respertively, and the pixel format was set to 256 x 256. Using the code, we obtained X-ray images under various simulation conditions, and evaluated their image qualities through the calculations of SNR (signal-to-noise ratio), MTF (modulation transfer function), NPS (noise power spectrum), DQE (detective quantum efficiency). The image simulation code developed in this study can be applied effectively for a variety of digital X-ray imaging systems for their design optimization on various design parameters.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.185-205
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• 2014

SAR ground moving target indicator (GMTI) has long been an important issue for SAR advanced applications. As spatial resolution of space-borne SAR system has been significantly improved recently, the GMTI becomes a very useful tool. Various GMTI techniques have been developed particularly using multi-channel SAR systems. It is, however, still problematic to detect ground moving targets within single channel SAR images while it is not practical to access high resolution multi-channel space-borne SAR systems. Once a ground moving target is detected, it is possible to retrieve twodimensional velocities of the target from single channel space-borne SAR with an accuracy of about 5 % if moving faster than 3 m/s. This paper presents a quick-and-dirty method for detecting ground moving targets from single channel SAR single-look complex (SLC) images by differentiation. Since the signal powers of derivatives present Doppler centroid and rate, it is very efficient and effective for detection of non-stationary targets. The derivatives correlate well with velocities retrieved by a precise method with a correlation coefficient $R^2$ of 0.62, which is well enough to detect the ground moving targets. While the approach is theoretically straightforward, it is necessary to remove the effects of residual Doppler rate before finalizing the ground moving target candidates. The confidence level of results largely depends on the efficiency and effectiveness of the residual Doppler rate removal method. Application results using TerraSAR-X and truck-mounted corner reflectors validated the efficiency of the method. While the derivatives of moving targets remain easily detectable, the signal energy of stationary corner reflectors was suppressed by about 18.5 dB. It results in an easy detection of ground targets moving faster than 8.8 km/h. The proposed method is applicable to any high resolution single channel SAR systems including KOMPSAT-5.

• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.35-43
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• 2013

As texture images have become prevalent throughout a variety of industrial applications, copyright protection of these images has become important issues. For this reason, this paper proposes a color-texture image watermarking algorithm utilizing texture properties inherent in the image. The proposed algorithm selects suitable blocks to embed a watermark using the energy and homogeneity properties of the grey level co-occurrence matrices as inputs for the fuzzy c-means clustering algorithm. To embed the watermark, we first perform a discrete wavelet transform (DWT) on the selected blocks and choose one of DWT subbands. Then, we embed the watermark into discrete cosine transformed blocks with a gain factor. In this study, we also explore the effects of the DWT subbands and gain factors with respect to the imperceptibility and robustness against various watermarking attacks. Experimental results show that the proposed algorithm achieves higher peak signal-to-noise ratio values (47.66 dB to 48.04 dB) and lower M-SVD values (8.84 to 15.6) when we embedded a watermark into the HH band with a gain factor of 42, which means the proposed algorithm is good enough in terms of imperceptibility. In addition, the proposed algorithm guarantees robustness against various image processing attacks, such as noise addition, filtering, cropping, and JPEG compression yielding higher normalized correlation values (0.7193 to 1).

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.130-136
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• 2016

HEVC (High Efficiency Video Coding) extension considers screen content as one of its main candidate sources for encoding. Among the tools already included in HEVC version 1, the technique of using transform skip mode allows transform to be skipped and to perform quantization process only. It is known to improve video coding efficiency for screen contents which are characterized to have much high frequency energy. But encoding complexity increases since its encoder should decide whether transform should be used or not in each $4{\times}4$ transform block. Based on statistical correlation between IBC (Intra block copy) and transform skip modes both of which are known effective in screen contents, this paper proposes a combined method of the fast transform skip mode decision and a modified transform skip signaling which signals transform_skip_flag at CU level as a representative transform skip signal. By simulation, the proposed method is shown to reduce encoding time of $4{\times}4$ transform blocks by about 32%.

• Journal of The Korean Dental Society of Anesthesiology
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• v.14 no.1
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• pp.41-47
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• 2014

Background: Autophagy is a self-eating process that is important for balancing sources of energy at critical times in development and in response stress. Autophagy also plays a protective role in removing clearing damaged intracellular organelles and aggregated proteins as well as eliminating intracellular pathogens. The purpose of the present study was to examine the protective effect of propofol against hypoxic damage using keratinocytes. Methods: Human keratinocytes (HaCaT cells) were obtained from the American Type Culture Collection. Propofol which were made by dissolving them in DMSO were kept frozen at $-4^{\circ}C$ until use. The stock was diluted to their concentration with DMEM when needed. Prior to propofol treatment cells were grown to about 80% confluence and then exposed to propofol at different concentrations (0, 25, 50, 75, $100{\mu}M$) for 2 h pretreatment. Cell viability was measured using a quantitative colorimetric assay with thiazolyl blue tetrazolium bromide (MTT assay), and fluorescence microscopy and western blot analysis were used for evaluation of autophagy processes. Results: The viability of propofol-treated HaCaT cells was increased in a dose-dependent manner. Propofol did not show any significant toxic effect on the HaCaT cells. The autophagy inhibitor, 3-methyladenine, reduced cell viability of hypoxia-injured HaCat cells. Fluorescence microscopy and western blot analysis showed propofol induce autophagy pathway signals. Conclusions: Propofol enhanced viability of hypoxia-injured HaCaT cells and we suggest propofol has cellular protective effects by autophagy signal pathway activation.