• Journal of the Semiconductor & Display Technology
• /
• v.15 no.3
• /
• pp.35-39
• /
• 2016

Extreme Ultraviolet Lithography (EUVL) is the most promising technique in the field of Next Generation Lithography (NGL) expected to be used in the 1x-nm node for High Volume Manufacturing (HVM). But there exits remaining challenges for proper defect control of EUV mask. It was considered development of EUV pellicle for protecting the EUV mask has many obstacles due to high extinction coefficient of EUV wavelength. Recently researchers in the industry of semiconductor argue about the necessity of EUV pellicle and make effort to achieve it. In this paper, we investigated that the relationship between imaging performance and transmittance of EUV pellicle quantitatively. We made in-house EUV pellicle and analyzed its imaging performance of the dependence of pellicle transmittance using Coherent Scattering Microscopy(CSM). The imaging performance of EUV mask with pellicle is affected by its transmittance and we found that the performance of EUV mask improved with higher transmittance pellicle.

• Journal of the Ergonomics Society of Korea
• /
• v.28 no.4
• /
• pp.91-99
• /
• 2009

A visual stress may provoke migraine, cephalalgia, intervene a long term reading and learning capability and reduce the productivity of a laborer who uses computer for a good while. In this study, a web based screening tool for visual stress was developed, it applied to 72 visually normal young persons in parallel with traditional questionnaire about symptoms of visual stress. To estimate visual stress, It is proposed to measure difference of visual search time of Han Gul characters as targets between visual stressful pattern and non-visual stressful pattern as global background of characters. As a result of test, 5 subjects were screened whose mean visual search time in the stressful pattern with 6 CPD spatial frequency increase significantly more than in none stressful pattern(t-test, one-tailed, p=$1.0407\times10^{-11}$). 2 of them were diagnosed as mild visual stress syndrome in the clinic. None had visual distortion and 50% of subjects had visual discomfort in results of the questionnaire. Correlation between visual search time increase rate and normalized number of visual discomfort may be slight(C. coefficient=0.1355). This study may contribute as a basic research for screening person with migraine, visual reading disabilities and VDT syndrome. It is required to apply the test to visual reading disabilities, migraine with visual distortion and/or visual discomfort as well as normal person for higher reliability of the screening tool.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.20 no.4
• /
• pp.47-54
• /
• 1983

The performance of an intra-frame DCT/DPCM hybrid coding is investigated with the criteria of normalized mean square error and subjective test for various system parameters. It includes the prediction coefficient in transform domain, normalization factor and bit-map in block quantizer, and adaptive coding. It is shown that the generalized covariance model of image is a convenient tool for bit-map and adaptive coding, and for a fast low bit-rate coding.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.1
• /
• pp.81-86
• /
• 2011

Watermarking is one of the methods that insist on a copyright as it append digital signals in digital informations.(image, video, ets) In this paper, we proposed a digital watermarking algorithm which improved Gradient of DCT Coefficient. This method targets MPEG-2 TM5 system and watermarking process is to be performed during Quantization DCT. Watermark was inserted on Y components of each frames. The PSNR difference between the compressed images with and without watermarking was only 0..23dB. In each case that the resulting image was reusable the normalized correlation between the extracted watermark and the original one was above 0.99.

• Nuclear Engineering and Technology
• /
• v.49 no.4
• /
• pp.810-816
• /
• 2017

A graphite calorimetry system was built and tested under irradiation. The noise level of the temperature measurement system was approximately 0.08 mK (peak to peak). The temperature of the core part rose by approximately 8.6 mK at 800 MU (monitor unit) for 6-MV X-ray beams, and it increased as X-ray energy increased. The temperature rise showed less spread when it was normalized to the accumulated charge, as measured by an external monitoring chamber. The radiation energy absorbed by the core part was determined to have values of $0.798J/{\mu}C$, $0.389J/{\mu}C$, and $0.352J/{\mu}C$ at 6 MV, 10 MV, and 18 MV, respectively. These values were so consistent among repeated runs that their coefficient of variance was less than 0.15%.

• Journal of Ocean Engineering and Technology
• /
• v.11 no.3
• /
• pp.76-88
• /
• 1997

Constant .DELTA.K fatigue crack growth rate experiments were performed by applying an intermediate single and multiple overload for structural steel, SM45C. The purpose of the present study is to investigate the influence of multiple overloads at various stress intensity factor ranges and the effect of statistical variability of crack retardation behavior. The normalized delayed load cycle, delayed crack length and the minimum crack growth rate are increased with increasing baseline stress intensity factor range when the overload ratio and the number of overload application were constant. The crack retardation under low baseline stress intensity factor range increases by increasing the number of overload application, but the minimum crack growth rate decreases by increasing the number of overload application. A strong linear correlation exists between the minimum crack growth rate and the number of overload applications. And, it was observed that the variability in the crack growth retardation behavior are presented, the probability distribution functions of delayed load cycle, delayed crack length and crack growth life are 2-parameter Weibull. The coefficient of variation of delayed load cycle and delayed crack length for the number of 10 overload applications data are 14.8 and 9.2%, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 1999.11a
• /
• pp.244-247
• /
• 1999

in this paper, we propose the recognition system of face using polynomial coefficients to recognize fact images using neural network. The system consists of following steps. First step, the sizes of fare images is reduced sizes of input images to 1/4 using wavelet transform. Second step, the polynomial coefficients is obtained from low frequency coefficient matrix after 3 level wavelet transform. Third step, polynomial coefficients is normalized. The of range of normalization is from -1 to 1. Last, Face images is trained and recognized using neural network with error back propagation algorithm.

• Nuclear Engineering and Technology
• /
• v.51 no.3
• /
• pp.719-722
• /
• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.439-443
• /
• 2019

To improve the noise characteristics, software-based noise reduction algorithms are widely used in cadmium zinc telluride (CZT) pixelated semiconductor gamma camera system. The purpose of this study was to develop an improved median filtering algorithm using a thresholding method for noise reduction in a CZT pixelated semiconductor gamma camera system. The gamma camera system simulated is a CZT pixelated semiconductor detector with a pixel-matched parallel-hole collimator and the spatial resolution phatnom was designed with the Geant4 Application for Tomography Emission (GATE). In addition, a noise reduction algorithm with a median filter using an improved thresholding method is developed and we applied our proposed algorithm to an acquired spatial resolution phantom image. According to the results, the proposed median filter improved the noise characteristics compared to a conventional median filter. In particular, the average for normalized noise power spectrum, contrast to noise ratio, and coefficient of variation results using the proposed median filter were 10, 1.11, and 1.19 times better than results using conventional median filter, respectively. In conclusion, our results show that the proposed median filter using improved the thresholding method results in high imaging performance when applied in a CZT semiconductor gamma camera system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.9
• /
• pp.4390-4407
• /
• 2019

The paucity of pilot signals in Massive MIMO system is a vital issue. To accommodate substantial number of users, pilot signals are reused. This leads to interference, resulting in pilot contamination and degrades channel estimation at the Base Station (BS). Hence, mitigation of pilot contamination is exigency in Massive MIMO system. The proposed Time Shifted Pilot Signal Transmission with Pilot signal Hopping (TSPTPH), addresses the pilot contamination issue by transmitting pilot signals in non-overlapping time interval with hopping of pilot signals in each transmission slot. Hopping is carried by switching user to new a pilot signal in each transmission slot, resulting in random change of interfering users. This contributes to the change in channel coefficient, which leads to improved channel estimation at the BS and therefore enhances the efficiency of Massive MIMO system. In this system, Uplink Signal Power to Interference plus Noise Power Ratio (SINR) and data-rate are calculated for pilot signal reuse factor 1 and 3, by estimating the channel with Least Square estimation. The proposed system also reduces the uplink Signal power for data transmission of each User Equipment for normalized spectral efficiency with rising number of antennas at the BS and thus improves battery life.