• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.182-186
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• 2011

A poling method using multiple negative voltage was introduced to fabricate periodically poled lithium niobate (PPLN) devices with quasi-phase matching (QPM) period of $12.9\;{\mu}m$ by utilizing an real-time visualization system. We also performed variation of the electric field during the poling. Two different conventionally used poling method, negative and positive single pulses, were used and the poling quality compared through microscopic images and far-field diffraction pattern analysis. Etched images on the +z and -z surfaces of PPLN showed that negative multiple pulse poling presented the highest periodicity in domain structures among the three methods. Duty ratio and its standard deviation were measured by analyzing far-field diffraction patterns. The newly introduced method of negative multiple pulse poling had duty ratio of 0.42 which was close to the ideal value of 0.50 and standard deviation of 0.020 that was about 3 times smaller than that of the other conventional methods.

• 디지털융복합연구
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• 제7권1호
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• pp.111-123
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• 2009

IT projects need engineers with various backgrounds to cooperate to build an IT system that satisfy the requirements of users given a limited expense and time. Such diversity of team members and the complexity of task naturally involve considerable amount of conflict among team members. High level of conflict among team members is known to be detrimental to the performance of the team. The purpose of this study is to examine the reasons for conflicts among team members in IT projects and to check how the level of conflict affects the performance of a project and the satisfaction of the members of the project team. To test the relationship, a survey on 166 participants in IT projects was conducted. The reasons for conflicts in IT projects were categorized into five types. The level of ambiguity was found to have a significant correlation with the level of conflict. And the level of conflict, in turn, is found to have a significant effect on the degree of satisfaction among team members and the project results. Based on the research results, it is suggested that a clear definition of tasks and their boundaries is required to reduce ambiguity and thus, the level of conflict and improve the level of satisfaction of IT project team members.

• 기본간호학회지
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• 제12권3호
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• pp.395-403
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• 2005

Purpose: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen in the intensive care units (ICUS). The purpose of this case-control study is to identify risk factors for acquisition of MRSA during ICU stays in patients with and without MRSA. Method: The study was conducted in a 16 beds-neurosurgical intensive care unit of a 2200-bed tertiary care university hospital in Seoul, Korea. Medical record and Critical Classification Scoring System were reviewed retrospectively in patients who were admitted more than 3 days from August 1, 2003 to May 30, 2004. Cases and controls were matched for age and gender. The obtained specimens were nasal swab and sputum. Result: There were 950 patients' admissions during the period. Among them, MRSA was isolated from twenty-three patients who were considered as hospital acquired. Artificial airway (p=.045), frequency of suction (p=.002), nasogastric tube (p=.004), wound drain (p=.045), and vancomycin (p=.019) were risk factors for MRSA acquisition in univariate analysis. Frequency of suction (p=.012, OR 3.5) was revealed as the only risk factor in multivariate conditional logistic regression. Conclusion: Our findings give support to recent studies that suggest that frequent physical contact maγ increase the nosocomial acquisition of MRSA in a neurosurgical ICU.

• 복식
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• 제61권10호
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• pp.16-31
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• 2011

This paper aims to identify the similarities and differences of color preference for mountain climbing wear according to gender, season and item. Total of 749 photos of mountain climbers were taken in 2009 during weekends in May and October at two mountains in Seoul. In order to analyze color by hue and tone, all the data were digitalized using Photoshop and converted to HV/C by using the Munsell Conversion software. For the purpose of data analysis, 13 colors of hue, including 10 base colors of the Munsel color system plus white, gray and black, and 12 tones of PCCS were grouped into 5 groups according to close distance. Jumper, t-shirts, vest and pants were selected as the 4 item categories. Results showed that there were clear differences in color preference based on gender. Women, with a preference for red, reddish purple, black, purple and blue, displayed wider range of choices in color as compared to men, who preferred black and blue color throughout all seasons. Yellow, green, and greenish blue were less preferred by both men and women. For pants, black represented over 90% as the main color for both genders. Overall, men preferred dark tones and women preferred vivid and bright tones. Moreover, there were less distinct differences in color preference according to season and item.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2687-2698
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• 2020

Most of the machine learning-based intrusion detection tools developed for Industrial Control Systems (ICS) are trained on network packet captures, and they rely on monitoring network layer traffic alone for intrusion detection. This approach produces weak intrusion detection systems, as ICS cyber-attacks have a real and significant impact on the process variables. A limited number of researchers consider integrating process measurements. However, in complex systems, process variable changes could result from different combinations of abnormal occurrences. This paper examines recent advances in intrusion detection algorithms, their limitations, challenges and the status of their application in critical infrastructures. We also introduce the discussion on the similarities and conflicts observed in the development of machine learning tools and techniques for fault diagnosis and cybersecurity in the protection of complex systems and the need to establish a clear difference between them. As a case study, we discuss special characteristics in nuclear power control systems and the factors that constraint the direct integration of security algorithms. Moreover, we discuss data reliability issues and present references and direct URL to recent open-source data repositories to aid researchers in developing data-driven ICS intrusion detection systems.

• Investigative Magnetic Resonance Imaging
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• 제25권4호
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• pp.229-251
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• 2021

Arteriosclerosis is the leading cause of stroke, with a fatality rate surpassing that of ischemic heart disease. High-resolution vessel wall magnetic resonance imaging is generally recognized as a non-invasive and panoramic method for the evaluation of arterial plaque; however, this method requires improved signal-to-noise ratio and scanning speed. Recent advances in high-density head and neck coil arrays are characterized by broad coverage, multiple channels, and closefitting designs. This review analyzes fast magnetic resonance imaging from the perspective of accelerated algorithms for vessel wall imaging and demonstrates the need for effective algorithms for signal acquisition using advanced radiofrequency system. We summarize different phased-array structures under various experimental objectives and equipment conditions, introduce current research results, and propose prospective research studies in the future.

• Advances in nano research
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• 제14권2호
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• pp.155-164
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• 2023

Grain size in sheet metals in one of the main parameters in determining formability. Grain size control in industry requires delicate process control and equipment. In the present study, effects of grain size on the formability of steel sheets is investigated. Experimental investigation of effect of grain size is a cumbersome method which due to existence of many other effective parameters are not conclusive in some cases. On the other hand, since the average grain size of a crystalline material is a statistical parameter, using traditional methods are not sufficient for find the optimum grain size to maximize formability. Therefore, design of experiment (DoE) and artificial intelligence (AI) methods are coupled together in this study to find the optimum conditions for formability in terms of grain size and to predict forming limits of sheet metals under bi-stretch loading conditions. In this regard, a set of experiment is conducted to provide initial data for training and testing DoE and AI. Afterwards, the using response surface method (RSM) optimum grain size is calculated. Moreover, trained neural network is used to predict formability in the calculated optimum condition and the results compared to the experimental results. The findings of the present study show that DoE and AI could be a great aid in the design, determination and prediction of optimum grain size for maximizing sheet formability.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4684-4692
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• 2022

Radionuclide identification is an important part of the nuclear material identification system. The development of artificial intelligence and machine learning has made nuclide identification rapid and automatic. However, many methods directly use existing deep learning models to analyze the gamma-ray spectrum, which lacks interpretability for researchers. This study proposes an explainable radionuclide identification algorithm based on the convolutional neural network and class activation mapping. This method shows the area of interest of the neural network on the gamma-ray spectrum by generating a class activation map. We analyzed the class activation map of the gamma-ray spectrum of different types, different gross counts, and different signal-to-noise ratios. The results show that the convolutional neural network attempted to learn the relationship between the input gamma-ray spectrum and the nuclide type, and could identify the nuclide based on the photoelectric peak and Compton edge. Furthermore, the results explain why the neural network could identify gamma-ray spectra with low counts and low signal-to-noise ratios. Thus, the findings improve researchers' confidence in the ability of neural networks to identify nuclides and promote the application of artificial intelligence methods in the field of nuclide identification.

• Biomolecules & Therapeutics
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• 제31권6호
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• pp.648-654
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• 2023

Oxidative stress-induced melanocyte apoptosis is linked to the immune system and plays a critical role in the pathogenesis of vitiligo. Aquaporin-3 (AQP3), which is downregulated in vitiligo keratinocytes, regulates intracellular H₂O₂ accumulation. However, the role of AQP3 in oxidative stress is uncertain in vitiligo. This study investigated the effect of downregulated AQP3 on oxidative stress in vitiligo using lesional and non-lesional skin specimen sets from vitiligo patients and primary cultured adult normal human epidermal keratinocytes, with or without downregulation and overexpression of AQP3 in the presence or absence of H₂O₂ treatment. The levels of nuclear factor E2-related factor 2 (NRF2) and/or its main target, NAD(P)H quinone dehydrogenase 1 (NQO-1), were lower in the lesional keratinocytes and cultured keratinocytes with AQP3 knockdown, but were increased in keratinocytes upon AQP3 overexpression. Ratios of NRF2 nuclear translocation and NQO-1 expression levels were further reduced in AQP3-knockdown keratinocytes following H₂O₂ treatment. The conditioned media from AQP3-knockdown keratinocytes treated with H₂O₂ contained higher concentrations of reactive oxygen species (ROS). Moreover, the number of viable melanocytes was reduced when the conditioned media were added to the culture media. Overall, AQP3 downregulation in the keratinocytes of patients with vitiligo can induce oxidative stress in neighboring melanocytes, leading to melanocyte death.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2007년도 춘계학술발표대회
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• pp.923-926
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• 2007

유비쿼터스 환경에서 소형, 저전력의 임베디드 시스템은 저가로 구성되는 시스템이라는 특성으로 인해 넓고 다양한 지역에 분포될 수 있고 분포 시킬 시스템의 개수와 설치 방법등에 있어 큰 유연성을 가지고 있어 그 활용에 있어 매우 큰 잠재적인 요소를 보유하고 있다. 이러한 시스템에 채용되는 마이크로컨트롤러는 매우 제한된 메모리 용량과 낮은 클럭속도, 낮은 레벨의 연산 성능을 가지는게 일반적이다. 본 논문에서의 마이크로 컨트롤러를 위한 영상 촬영 및 압축 시스템은 이러한 소형의 마이크로 컨트롤러를 사용한 소형의 저전력 임베디드 시스템에서 사용하기 위한 목적의 영상 촬영 및 압축을 위한 시스템이다. 본 시스템은 영상을 촬영하고 촬영된 영상을 JPEG로 압축하며 이를 내부 메모리에 보관함으로써 저사양의 마이크로컨트롤러를 가지는 시스템과 낮은 데이터 전송률을 가지는 통신 환경에서도 이미지 기반의 서비스를 제공할 수 있는 환경을 제공하면서 동시에 매우 소형의 시스템으로 배터리 동작 기반의 저전력 시스템을 위한 설계로 유비쿼터스 환경의 구성에 매우 유용한 기능을 제공한다.