• Journal of radiological science and technology
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• v.26 no.4
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• pp.39-46
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• 2003

Digital radiographic systems based on solid-state detectors, commonly referred to as flat-panel detectors, are gaining popularity in clinical practice. Large area, flat panel solid state detectors are being investigated for digital radiography. The purpose of this work was to evaluate the active matrix flat panel digital x-ray detectors in terms of their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). In this paper, development and evaluation of a selenium-based flat-panel digital x-ray detector are described. The prototype detector has a pixel pitch of $139\;{\mu}m$ and a total active imaging area of $14{\times}8.5\;inch^2$, giving a total 3.9 million pixels. This detector include a x-ray imaging layer of amorphous selenium as a photoconductor which is evaporated in vacuum state on a TFT flat panel, to make signals in proportion to incident x-ray. The film thickness was about $500\;{\mu}m$. To evaluate the imaging performance of the digital radiography(DR) system developed in our group, sensitivity, linearity, the modulation transfer function(MTF), noise power spectrum (NPS) and detective quantum efficiency(DQE) of detector was measured. The measured sensitivity was $4.16{\times}10^6\;ehp/pixel{\cdot}mR$ at the bias field of $10\;V/{\mu}m$ : The beam condition was 41.9\;KeV. Measured MTF at 2.5\;lp/mm was 52%, and the DQE at 1.5\;lp/mm was 75%. And the excellent linearity was showed where the coefficient of determination ($r^2$) is 0.9693.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.11-21
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• 2008

• Journal of Digital Contents Society
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• v.15 no.2
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• pp.219-225
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• 2014

Competition between corporations is getting more intense, so they need customer feedback in order to fulfill an effective management. Recently, SNS (Social Network Service) such as Twitter and Facebook has grown dramatically because of smart phones. Social media like Twitter and Facebook let customers to express their needs, and using big data such as data on SNS is a very effective method for getting customer's feedback. Collecting and analyzing social big data are operated by Buzz monitoring system. This research suggests how to utilize big data for getting customer's feedback on hotel CRM(Customer Relationship Management), which considers customer itself as asset of business. This paper demonstrates the research of buzz monitoring system that analyzes big data, and presents results of hotel customer reputation using buzz monitoring system. It would analyze the result from the hotel customer reputation, and research the implication in this paper.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.757-763
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• 2019

Recently, Following the recent development of flat panel detector with wide dynamic ranges, increasing numbers of healthcare providers have begun to use digital radiography. As a result, filter thickness standards should be reestablished, as current clinical practice requires the use of thicknesses recommended by the National Council on Radiation Protection and Measurements, which are based on information, acquired using conventional analog systems. Here we investigated the possibility of minimizing dose creep and optimizing patient dose using Al filters in digital radiography. The use of thicker Al filters resulted in a maximum 19.3% reduction in the entrance skin exposure dose when medical images with similar sharpness values were compared. However, resolution, which is a critical factor in imaging, had a significant change of 1.01 lp/mm. This change in resolution is thought to be due to the increased amount of scattered rays generated from the object due to the X-ray beam hardening effect. The increase in the number of scattered rays was verified using the scattering degradation factor. However, the FPD, which has recently been developed and is widely used in various areas, has greater response to radiation than analog devices and has a wide dynamic range. Therefore, the FPD is expected to maintain an appropriate level of resolution corresponding to the increase in the scattered-ray content ratio, which depends on filter thickness. Use of the FPD is also expected to minimize dose creep by reducing the exposure dose.

• Journal of Venture Innovation
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• v.7 no.2
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• pp.57-76
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• 2024

A virtual influencer is a digital artifact that primarily operates on social media and acts like the human influencer. This study investigate how the attractiveness and reputation of virtual influencers affect consumers' purchase intentions. Based on previous studies, we developed a research model and questionnaire, and analyzed a total of 371 survey questionnaires using a structural equation model. The study results show that reputation positively affect attachment, imitation desire, and interaction, while attractiveness positively influence attachment and imitation desire but not interaction. Lastly, purchase intention was positively influenced by imitation desire, attachment, and interaction; which indicates that attractiveness, reputation, and interactivity are crucial factors in virtual influencer implementation strategies. The quality and reliability of contents provided by virtual influencers are essential not only for gaining popularity but also for maintaining a good reputation. Additionally, continuous interaction is necessary in order to foster close relationships with consumers. A few practical insights are presented for firms considering to implement a virtual influencer.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.533-542
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• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• The Optical Journal
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• s.119
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• pp.35-37
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• 2009

지난 수년 간 국내 광학산업은 눈부신 발전을 했다. 디지털카메라, 핸드폰카메라, 정보저장기기, 복사기와 같은 전자제품 시장의 성장, 평판디스플레이의 도약, LED 조명의 출현, 매 순간이 숨 가쁜 변화와 팽창의 연속이었다. 작년에 시작된 미국발 금융위기가 전 세계 신용경색, 실물경제 침체로 이어지면서 국내 광학산업에 먹구름이 드리워지고 위기감이 고조되고 있다. 본 원고는 해외 광학회사, 연구기관들과 협력하면서 고찰한 내용에 필자의 의견을 덧붙인 것이다. 이제는 국내회사들이 지속적으로 성장하기 위해서 세계 시장을 대상으로 '그레이트 게임'을 할 시기이다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.109-109
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• 2004

구조물에 있어서 진동은 소음을 유발하며 구조물을 불안정하게 만드는 요인이 된다. 특히, 저주파 진동은 구조물에 미치는 영향이 크므로, 유연구조물의 저주파 진동모드들을 우선적으로 제어할 필요가 있다. 본 논문에서는 압전세라믹을 작동기로, 압전필름을 감지기로 사용하였고, 능동 제어 알고리즘의 하나인 적응형 디지털 PPF(Positive Position Feedback) 제어기를 구성하여 유연 외팔 평판과 열린 박스 구조물에서 저주파 진동을 감소시켰다.(중략)

• The Science & Technology
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• v.33 no.4 s.371
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• pp.14-15
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• 2000

91년부터 서울대교수 재직중인 정덕균 교수는 95년 재미교포와 손잡고 미국에서 '실리콘이미지'라는 벤처기업을 창업해 4년만에 주식이 나스닥에 상장되면서 그 수익금 일부인 1백만달러(약 12억원)을 서울대에 기부했다. 이 벤처기업은 기존 컴퓨터의 모니터방식을 아날로그에서 디지털로 바꿔 해상도를 크게 향상시키는 컴퓨터용 차세대 평판모니터를 개발해 세계적인 컴퓨터회사인 컴펙, 인텔 등에 납품하고 있다.

• Korean Journal of Digital Imaging in Medicine
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• v.6 no.1
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• pp.9-18
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• 2003

디지털 영상 검출기와 디스플레이 기술의 발달과 의료영상전달시스템(PACS)의 출현은 전통적 필름방식에 비하여 디지털 방식으로 방사선과 영상을 획득하고 전송, 저장하는 매우 효과적인 수단을 제공하고 있다. 2002년 8월, 연세의료원 세브란스병원은 진단 영상 판독 목적으로 18 대의 CRT(Braco View, Belgium)와 32대의 평판 LCD(Totoku Electric Co., Ltd., Japan) 디스플레이 장치를 GE full-PACS(GE 메디칼시스템코리아 : GEMSK)와 연계하여 설치 완료하였다. 본 연구에서, 기하학적 왜곡, 반사, 휘도 반응, 휘도 균일도, 분해능, 노이즈,베일링 글레어, 칼라 균일도 항목들을 AAPM TG18 보고서 9.0에 따라서 시각적 그리고 부분적으로는 정량적인 방법으로 인수검사를 실시하여 보고한다. 사용된 장비는 색도계로도 사용되는 간편한 휘도계, TG18 테스트 패던, AAPM Tg18 AT plug-in software(Barco View Ltd., Kortrijk, Belgium)이었다. 칼라 균일도를 제외한 모든 테스트 결과는 AAPM TG18에서 권고하는 기준에 일치하였으며 진단 영상 판독에 사용하기에 전적으로 수락할 수 있는 성능이었다. 결론으로, 사용된 인수검사는 단지 인수 검사 표준을 제공하는 것 뿐만 아니라 품질검사(QC)의 지침, 판독 환경의 최적화 그리고 교체 시기나 업그레이드 시기를 결정하여주는 중요한 역할을 할 수 있을 것이다.