• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.27 no.1
• /
• pp.54-61
• /
• 2023

With the development of IoT technologies and artificial intelligent, diverse digital image equipments are being used in industrial sites. Because image data can be easily damaged by noise while it's obtained with a camera or a sensor and the damaged image has a bad effect on the process of image processing, noise removal is being demanded as preprocessing. In this thesis, for the restoration of image damaged by the noise of random impulse, a switching filter algorithm based on noise estimation was suggested. With the proposed algorithm, noise estimation and error distraction were carried out according to the similarity of the pixel values in the local mask of the image, and a filter was chosen and switched depending on the ratio of noise existing in the local mask. Simulations were conducted to analyze the noise removal performance of the proposed algorithm, and as a result of magnified image and PSNR comparison, it showed superior performance compared to the existing method.

• Resources Recycling
• /
• v.33 no.1
• /
• pp.31-36
• /
• 2024

The separation of Ag and Zn from the nitrate leachate of spent silver oxide batteries using Cyanex272 as an extractant was investigated. The extraction of Ag and Zn was affected by the concentrations of nitric acid and the extractant. Cyanex-272 selectively extracted Zn over Ag when the HNO₃ concentration was lower than 0.1 mol/L. The co-extracted Ag was removed by stripping with 1 mol/L thiourea. Stripping of Zn from the loaded Cyanex-272 was accomplished using 0.5 mol/L HNO₃ after the removal of Ag. The McCabe-Thiele diagrams for the extraction of Zn with Cyanex-272, the scrubbing tripping of Ag with thiourea, and the stripping of Zn with HNO₃ were constructed. The results were verified by simulated counter-current extraction and stripping experiments. Finally, a process for the separation of Ag and Zn from silver oxide batteries was proposed.

• Smart Media Journal
• /
• v.13 no.2
• /
• pp.44-51
• /
• 2024

The construction of a stress measurement detaset plays a curcial role in various modern applications. In particular, for the efficient training of artificial intelligence models for stress measurement, it is essential to compare various biases and construct a quality-controlled dataset. In this paper, we propose the construction of a stress measurement dataset with quality management through the comparison of various biases. To achieve this, we introduce strss definitions and measurement tools, the process of building an artificial intelligence stress dataset, strategies to overcome biases for quality improvement, and considerations for stress data collection. Specifically, to manage dataset quality, we discuss various biases such as selection bias, measurement bias, causal bias, confirmation bias, and artificial intelligence bias that may arise during stress data collection. Through this paper, we aim to systematically understand considerations for stress data collection and various biases that may occur during the construction of a stress dataset, contributing to the construction of a dataset with guaranteed quality by overcoming these biases.

• The Journal of the Acoustical Society of Korea
• /
• v.27 no.6
• /
• pp.309-318
• /
• 2008

In this paper, we discuss a method for efficiently coding the high-band signal in the split-band coding approach where an input signal is divided into two bands and then each band may be encoded separately. Generally, and especially through the research on the artificial bandwidth extension (BWE), it is well known that there is a correlation between the two bands to some degree. Therefore, some coding gain could be achieved by utilizing the correlation. In the BWE-prediction-based coding approach, using a simple linear BWE function may not yield optimal results because the correlation has a non-linear characteristic. In this paper, we investigate the new coding scheme more in details. A few representative BWE functions including linear and non-linear ones are investigated and compared to find a suitable one for the coding purpose. In addition, it is also discussed whether there are some additional gains in combining the BWE coder with the predictive vector quantizer which exploits the temporal correlation.

• Journal of the Korean Society of Radiology
• /
• v.82 no.3
• /
• pp.551-561
• /
• 2021

Atherectomy has become a promising treatment option for peripheral artery disease caused by diabetes mellitus or end-stage renal disease. Atherectomy refers to the removal of atheromatous tissue by mechanical method, resulting in an enlarged lumen of the treated blood vessel. Based on this method, the term is limited to the percutaneous minimally invasive approach, and there are currently two types of atherectomy devices available in Korea. The increased prevalence of atherectomy has led to the concept of "vascular preparation" and a new treatment concept of "leave nothing behind." Various studies have proven the safety and effectiveness of atherectomy; however, there are some limitations. We need to remain focused on patient selection and subsequent large-scale research.

• Membrane Journal
• /
• v.22 no.2
• /
• pp.142-154
• /
• 2012

In order to remove $CO_2$ from the DME plant process, we investigated the composite membrane with rubbery polymers as the separation layer and its separation performance of $CO_2$ and $H_2$. Hollow fiber membranes for supporting layer were prepared by solution spinning method. In case of using PDMS as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 300 GPU and minimum $CO_2/H_2$ selectivitties were 4.3 and in case of using PEBAX as a separation layer, the composite membranes showed the permeation rates of $CO_2$ were over 120 GPU and minimum $CO_2/H_2$ selectivities were 5.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.22-22
• /
• 2009

최근 산화물 반도체와 나노소자 대한 관심이 날로 높아지고 있는 가운데 산화아연(ZnO) 나노구조를 이용한 나노소자 제작이 많이 연구되고 있다. 산화아연은 c축으로 우선 배향성을 가지는 우르짜이트 구조로써, 나노선 성장이 다른 산화물에 비해 용이하고 그 물리적, 화학적 특성이 안정 무수하다. 이러한 산화아연 나노선 제작법 가운데, 유기금속화학기상증착법은 다른 성장법에 비해 결정학적 광학적 특성이 우수하고 성장속도가 빨라 고품질 나노선 성장에 용이한 장비로 각광받고 있다. 하지만 bottom-up 공정을 기반으로 한 나노소자제작에서 몇 가지 문제점을 가지고 있다. 1) 수직형 대면적 성장, 2) 나노선 밀도 조절의 어려움, 3) 기판과의 계면층에 자발적으로 생성되는 계면층의 제거, 4) 고온성장시 precursor의 증발 문제 등이 그것이다. 본인은 이러한 문제점을 해결하기 위해 산화아연 나노구조 성장 시, 마그네슘(Mg)을 도입하여, 각 원소의 함량 분포 정도에 따라 기판 표면에 30nm 두께 미만의 상분리층(단결정+비정질층)을 자발적으로 형성시켰다. 성장이 진행됨에 따라, 아연이 rich한 단결정 층에서는 나노선이 선택적으로 성장하게 하였고, 마그네슘이 rich한 비정질 층에서는 성장이 이루어지지 않게 하였다. 따라서 산화아연이 증발되는 온도영역에서 10nm 이하 직경을 가지는 나노선을 자발적으로 계면층 없이 수직 성장하였다. 또한, 표면의 단결정, 비정질의 사이즈를 Mg 함량으로 적절히 조절한 결과, 산화아연계 나노월 구조성장이 가능하였다.

• Clean Technology
• /
• v.22 no.3
• /
• pp.196-202
• /
• 2016

In this study, ceria- based catalysts were prepared for dimethyl carbonate (DMC) synthesis and reaction conditions were evaluated for finding the optimal reaction route. In order to find optimal catalysts for DMC synthesis, calcination temperature and Cu(II) impregnation amount were evaluated. The oxidative carbonylation using methanol, carbon monoxide and oxygen and the direct synthesis using methanol and carbon dioxide were introduced for producing DMC. Following the law of Le Chatelier, the dehydration reaction was applied for enhancing the reactivity (methanol conversion) as removing water during the reaction. 2-cyanopyridine, as a chemical dehydration agent, was used. In the case of the oxidative carbonylation, methanol conversion rate increased from 15.1% to 38.7% and the DMC selectivity increased from 0% to 98.8%. In the case of the direct synthesis, methanol conversion rate increased from 1.0% to 77.8% and the DMC selectivity increased from 41.2% to 100.0%.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.2
• /
• pp.210-216
• /
• 2017

Recovery of low level nitric acid and sulfuric acid ions, which were contained in wastewater of a wet scrubber for de-NOx and de-SOx from ship engines, was attempted as fertilizing materials. This study utilized a selective extraction method using four organic solvents to precipitate the solid salts of ammonium nitrate and ammonium sulfate. The IR analysis showed almost same composition of the extracted ammonium salts with a commercial product, and recovery rate of nitrogen and sulfuric ions was 89% and 80% respectively. It was found that the selectivity and solubility consequently could be the crucial factors to recover the low level ions from the waste scrubbing water.

• Journal of the Korea Society for Simulation
• /
• v.16 no.4
• /
• pp.13-22
• /
• 2007

Fault detection of cycle-based signals is typically performed using statistical approaches. Univariate SPC using few representative statistics and multivariate analysis methods such as PCA and PLS are the most popular methods for analyzing cycle-based signals. However, such approaches are limited when dealing with information-rich cycle-based signals. In this paper, process fault defection method based on wavelet analysis is proposed. Using Haar wavelet, coefficients that well reflect the process condition are selected. Next, Hotelling's $T^2$ chart using selected coefficients is constructed for assessment of process condition. To enhance the overall efficiency of fault detection, the following two steps are suggested, i.e. denoising method based on wavelet transform and coefficient selection methods using variance difference. For performance evaluation, various types of abnormal process conditions are simulated and the proposed algorithm is compared with other methodologies.