• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.9-14
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• 2021

Recently, magnetic resonance imaging (MRI), which can acquire images with good contrast without exposure to radiation, has been widely used for diagnosis. However, noise that reduces the accuracy of diagnosis is essentially generated when acquiring the MR images, and by adjusting the parameters, the noise problem can be solved to obtain an image with excellent characteristics. Among the parameters, the number of excitation (NEX) can acquire images with excellent characteristics without additional degradation of image characteristics. In contrast, appropriate NEX setting is required since the scan time increases and motion artifacts may occur. Therefore, in this study, after fixing all MRI parameters through the MRiLab simulation program, we tried to evaluate the tendency of image characteristics according to changing NEX through quantitative evaluation of brain T2 weighted images acquired by adjusting only NEX. To evaluate the noise level and similarity of the acquired image, signal to noise ratio (SNR), contrast to noise ratio (CNR), root mean square error (RMSE) and peak signal to noise ratio (PSNR) were calculated. As a result, both noise level and similarity evaluation factors showed improved values as NEX increased, while the increasing width gradually decreased. In conclusion, we demonstrated that an appropriate NEX setting is important because an excessively large NEX does not affect image characteristics improvement and cause motion artifacts due to a long scan.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.544-551
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• 2023

Speech enhancement used to improve the perceptual quality and intelligibility of noise speech has been studied as a method using a complex-valued spectrum that can improve both magnitude and phase in a method using a magnitude spectrum. In this paper, a study was conducted on how to apply attention mechanism to complex-valued spectrum-based speech enhancement systems to further improve the intelligibility and quality of noise speech. The attention is performed based on additive attention and allows the attention weight to be calculated in consideration of the complex-valued spectrum. In addition, the global average pooling was used to consider the importance of the feature map. Complex-valued spectrum-based speech enhancement was performed based on the Deep Complex U-Net (DCUNET) model, and additive attention was conducted based on the proposed method in the Attention U-Net model. The results of the experiments on noise speech in a living room environment showed that the proposed method is improved performance over the baseline model according to evaluation metrics such as Source to Distortion Ratio (SDR), Perceptual Evaluation of Speech Quality (PESQ), and Short Time Object Intelligence (STOI), and consistently improved performance across various background noise environments and low Signal-to-Noise Ratio (SNR) conditions. Through this, the proposed speech enhancement system demonstrated its effectiveness in improving the intelligibility and quality of noisy speech.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1322-1325
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• 2009

Adaptive black band insertion improve blur phenomenon that caused by hold type issue of LCD, the approach regulate charge time by OE signal to control black inserted ratio, and the charge time be modified according the motion quantity of displaying content.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.179-182
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• 1988

Since the bits in any encoded PCM word are of different importance to the bit positions, in order to improve the signal to noise ratio the technique that the encoded signal bits are weighted for the QPSK transmission system, is presented. Also the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. Two weighting methods are shown here. One is the method that the same weighting profile is used to Q and I dimension in QPSK signal constellations. The other is diferent weighting to Q and I dimension. The gains of this new technique in overall signal s/n compared to conventional QPSK transmission system were 5 db and 2db, respectively.

• Journal of Digital Contents Society
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• v.11 no.3
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• pp.283-290
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• 2010

The effectiveness of 3.0T phase array coil images was tested by comparing signal-to-noise ratios for the same coil images relative to 1.5T endorectal coil images. Signal intensities were measured in the three regions of prostate, central and peripheral (right and left) after 40 patients with prostate cancer were imaged during the period between Jan. 2008 and Oct. 2009 with T2 W, T1 W, and DW images obtained respectively using endorectal coil on a 1.5T MR scanner and phase array coil on a 3.0T MR scanner. For quantitative analysis, comparisons of average SNRs for the same ROIs were made between groups scanned with a 1.5T and a 3.0T MR scanner. The signal-to-noise ratios were shown to increase more sharply when using a phase array coil at a 3.0T MR scanner compared to using an endorectal coil at a 1.5T MR scanner.

• Journal of Korean Neurosurgical Society
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• v.29 no.1
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• pp.101-107
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• 2000

Objectives : The evaluation of peripheral nerve injuries has traditionally relied on a clinical history, physical examination, and electrodiagnostic studies. The purpose of the present study was to examine serial magnetic resonance image(MRI) changes following acute muscle denervation under experimental conditions and to identify potential advantages and disadvantages of this use of MRI. Methods : An experimental transection of right sciatic nerve on Spargue-Dawley rats was performed. MRI was performed with T1-weighted spin-echo and STIR sequences. The imaging findings were compared with EMG in order to determine its sensitivity relative to this standard procedure. A simultaneous histopathological study provided information about the morphological basis of the imaging findings. Signal intensities were expressed as a ratio of abnormal to normal. Results : The signal intensity ratio of muscles with the STIR sequence was increased significantly at 2 weeks after sciatic nerve transection(p<0.05), although definite signal change was seen as early as 4 days postdenervation in one. EMG revealed significant denervation potential from 3 days after nerve transection. Diffuse cell atrophy was revealed hostologically at 2 weeks after transection, which was at the same time of significant signal change in MRI. Conclusion : MRI signal changes in denervated muscles secondary to nerve injury correlate with the degree of muscle atrophy on histologic examination. In addition to EMG, MRI can document the course of muscle atrophy and mesenchymal abnormalities in denervation. These results indicate that MRI can play a complementary role in the evaluation of patients with denervation.

• Archives of Pharmacal Research
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• v.10 no.1
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• pp.1-8
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• 1987

One of the problems of derivatie spectrophotometry, the decrease of signal-to-noise ratio by derivative operations, was solved by three concepts of digital filtering, ensemble averaging, least squares polynomial smoothing and Fourier smoothing. The suthors made several compouter programs written in APPLE SOFT BASIC language for the actual applications of the concepts of these digital filters on UV spectrophotometer system. As a result, ensemble averaging could not be used as a routine operation for the spectrophotometer used. The maximum S/N ratio enhancement factors achieved by least squares polynomial smoothing were 6.17 and 7.47 for the spectra of Gaussian and Lorentzian distribution models, and by Fourier smoothing 16.42 and 11.78 for the spectra of two models, respectively.

• ETRI Journal
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• v.45 no.1
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• pp.150-162
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• 2023

The polar delta-sigma modulator (DSM) transmitter architecture exhibits good coding efficiency and can be used for software-defined radio applications. However, the necessity of high clock speed is one of the major drawbacks of using this transmitter architecture. This study proposes a low-complexity timeinterleaved architecture for the polar DSM transmitter baseband part to reduce the clock speed requirement of the polar DSM transmitter using an upsampling technique. Simulations show that using the proposed four-branch timeinterleaved polar DSM transmitter baseband part, the clock speed requirement of the transmitter is reduced by four times without degrading the signal-tonoise-and-distortion ratio.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.499-505
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• 2012

TPMS(Tire Pressure Monitoring System) using the wireless communication technique is defined as the safety aid system to efficiently realize and manage the condition of tires in the vehicle. The wireless communication system of TPMS should suffers from various noise and interferences such as signals of each tire sensor or outside electrical equipments. In order to retain the data reliability of TPMS, we propose an assessment method of the data reliability based on signal-to-interference and noise ratio (SINR) of the received signal. The proposed technique can be widely applied to wireless duplex communication systems based on various sensors. We verify critical SINR values to satisfy data reliabilities of 95%, 97%, and 99% through computer simulation.

• Progress in Medical Physics
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• v.21 no.1
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• pp.70-77
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• 2010

This study tested how S/N (Signal to Noise Ratio) ratios and ADC (apparent diffusion coefficient) values vary with different T-scores in a group of patients with osteoporosis. Based on DEXA (Dual Energy X-ray Absorptiometry) T-scores for L1.L4 for two groups of subjects consisting of 30 healthy people without osteoporosis and 30 patients who came for treatment of waist (lumbar or low back) pain and were suspected to have osteoporosis as judged from the simple X-ray findings, this study classified every spine into two groups of osteoporosis and osteopenia. Signal intensity measurements were made in the four regions of L1 to L4 on diffusion-weighted MR images obtained using 1.5T MR scanner, while ADC measurements were obtained from ADC map images. As an approach for quantitative analysis, the comparison of the variances in S/N ratios and ADC values for varying T-scores in the selected regions of interest was carried out based on averaged T-scores, S/N ratios, and ADC values. Also, the variances in S/N ratios and ADC values for each of the groups of osteoporosis and osteopenia, which were classified into by T-scores, were compared. For qualitative analysis, a careful naked eye examination of signal intensity differences in the area of L4 was made on T1-weighted sagittal images for each of the healthy (normal), osteopenia, and osteoporosis groups. In the qualitative analysis, it was found that for both the osteopenia group and the osteoporosis group, as T-scores deceased, the S/N ratios on diffusion-weighted MR images also decreased, with the greatest decrease in the S/N ratio found in the osteoporosis group. Additionally, among the three groups, the lowest S/N ratio was found in the osteoporosis group. With respect to ADC map, it was found that for both the osteopenia group and the osteoporosis group, as T-scores deceased, the ADC values on diffusion-weighted MR images also decreased, with the greatest decrease in the ADC values found in the osteoporosis group. Additionally, among the three groups, the lowest ADC value was found in the osteoporosis group. On the other hand, in the qualitative analysis, the osteoporosis group showed the highest signal intensity. Additionally, among the three groups, the lowest signal intensity was found in the healthy (normal) group. It was found that as osteoporosis progressed, S/N ratio and ADC decreased, whereas signal intensity increased on T1-weighted images. Also, in diagnosing osteoporosis, MRI tests turned out to be (more) effective.