• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.3
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• pp.237-242
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• 2016

The major advantage of slip-ring technology in Spiral CT is that it facilitates continuous rotation of the x-ray tube, so that volume data can be acquired from a patient quickly. Not only for such a fast scan, but also for the dose reduction purpose, high signal-to-noise ratio and fast data acquisition system is required. In this study, we have built a multi-channel photodetector and multi-channel data acquisition system for CT application. The detector module consisted of CdWO4 crystal and Si photodiode in 16 channels. For the performance test of the preamplifier stage, both the transimpedance and switched integrator types are optimized for the photodetector modules. Switched integrator showed better noise performance in the limited bandwidth which is suitable for the current CT application. The control sequence for data acquisition and 20 bit ADC is designed with VHDL(Very High Speed Integrated Circuit Hardware Description Language) and implemented on FPGA(Field Programmable Gate Array) chip. Our Si photodiode detector module coupled to CdWO4 crystal showed comparable signal with other commercially available photodiode for CT. Switched integrator type showed higher SNR but narrower bandwidth compared to transimpedance preamplifier. Digital hardware is designed by FPGA, so that the control signal could be redesigned without hardware alteration.

• Journal of radiological science and technology
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• v.33 no.2
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• pp.109-120
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• 2010

The purpose of this study was first to analyze the utilization of dental examination through questionnaire to develop a diagnostic reference level of patient doses for dental radiography in korea. 77 dental institutions were classified into three groups: A group for the dental hospitals of the college of dentistry (11 institutions), B group for dental hospitals (30 institutions) and C group for dental clinics (36 institutions). The results were as follows : The mean numbers of unit chairs and medical staffs were 140.2, 15.3 and 5.8 sets, 112.6, 7.3 and 1.7 dentists, 3.1, 0.5 and no one radiologic technologists, and 19.7, 12.5 and 3.3 dental hygienists in A, B and C groups, respectively. The mean numbers of dental X-ray equipments were 14.64, 3.21 and 2.19 in A, B and C groups, respectively. Intraoral dental X-ray unit was used the most, the following equipments were panoramic, cephalometric, and cone-beam CT units. The most used X-ray imaging system was also digital system (above 50%) in all three groups. Insight dental film (Kodak, USA) having high sensitivity was routinely used for periapical radiography. The automatic processor was not used in many dental institutions, but the film-holding device was used in many dental institutions. The utilization rates of PACS in A, B and C groups were 90.9%, 83.3% and 16.7% respectively, and the PACS software program was used the most PiView STAR (Infinitt, Korea). The annual mean number of radiographic cases in one dental institution in 2008 for A group was 6.8 times and 21.2 times more than those for B and C groups, and periapical and panoramic radiographs were taken mostly. Tube voltage (kVp) and tube current (mA) for periapical radiography were similar in all three groups, but exposure time in C group was 12.0 times and 3.5 times longer than those in B and C groups. The amount of radiation exposure in C group, in which dental hygienists take dental radiographs, was more than those in other groups. The exposure parameters for panoramic radiography were similar in all three groups. In conclusion, the exposure parameters in dental radiography should be determined with reference level, not past experiences. Use of automatic processor and film-holding devices reduces the radiation exposure in film system. The quality assurance of dental equipments are necessary for the reduction of the patient dose and the improvement of X-ray image quality.

• Information and Communications Magazine
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• v.14 no.12
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• pp.77-85
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• 1997

지금까지 access network에서의 xDSL의 위치를 살펴보고 DSL, HDSL, ADSL 및 VDSL을 중심으로 기술 및 최근의 표준화동향을 살펴보았다. ITU의 조사에 따르면 97년 기준으로 전세계 약 8억가구에 copper access line이 연결되어 있고 그중의 70%이상이 가정에 연결되어 있는데 증가추세도 북미의 경우 년3.5%, 서유럽과 태평양연안의 경우 년4.5%의 성장율을 보이고 있어 2000년경에는 10억가구에 다다를 전망이다. 미국은 97년기준 약 1억가구에 1억6000만 copper access line이 연결되어 있는데 Yankee Group이 조사한 바에 따르면 2000년을 기준으로 3백만가구에 ADSL/RADSL/SDSL이 연결되고 관련 revenue는 10억달러에 이를것으로 추산하고 있다. 전세계 xDSL 시장규모를 미국의 5배정도로 보면 2000년경에는 전세계 twist pair의 2%정도에 xDSL이 연결되어 ADSL/RADSL/SDSL 관련 세계시장규모가 50억달러에 이르고 시장성장률은 30%에 이를 것으로 보고 있다. 현재 이러한 xDSL의 표준화작업은 3장에서 언급한 바와 같이 ANSI T1, ETSI에서 주로 주도되고 있으나 ITU-T, IEEE, ADSL Forum, ATM Forum, DAVIC 등 다른 group과 활발한 liasion meeting 을 통해서도 협력안을 마련하려 노력하고 있다. 예를 들어 DAVIC은 long range(1.5Km이상) PMD규격으로 ADSL을, mid range($300m\sim1.5km$) PMD규격으로 VDSL을, short range(300m이하) PMD규격으로 CAP방식의 FTTC를 각각구정하여 xDSL을 수용하고 있다. Microsoft의 CEO인 Bill Gates가 'Bandwidth bottleneck. No question. that's the biggest obstacle.'이라고 천명한 바와 같이 정보사회로의 진전에 있어 bandwidth는 시급히 해결되어야 할 문제이다. 정보사회의 꿈을 실현하고자 1993년부터 시작된 In-formation Infrastructure의 구축노력이 그동안 다양하게 시도되어왔으나 숱한 우여곡절과 실패를 겪은 telco등의 서비스업자들이 이제는 너무 큰 꿈을 쫓기보다는 internet이라는 현실적인 시장에서 xDSL과 cablemodem을 바탕으로 차근차근 새로 시작하고 있다고 생각된다. 그동안 ADSL, Forum을 중심으로한 일부 technology evangelist들은 전세계 8억가구에 깔려있는 copper twist pair를 경제적인 'the last mile solution'으로 활용할 것을 줄기차게 주장해왔다. 그동안 xDSL은 VDSL이라는 차세대 대안을 제시하여 interim solution이라는 울타리를 벗어나는데 성공하였을 뿐만 아니라 IDSL, SDSL, RADSL등의 새로운 고객지향적 xDSL을 개발하여 선택의 폭을 넓혀주었다. xDSL vendor들간의 치열한 경쟁속에서 값싼 xDSL 시스템들이 속속 등장하고 있으며, DSLAM[8]과 같은 switch solution도 제시되어 기존의 copper twist pair를 이용해 값싸게 다양한서비스를 제공해 줄 수 있는 기틀을 마련한 것이 오늘날의 xDSL의 성공요인이라고 생각된다. 일찌기 Bell Atlantic의 CEO Ray Smith가 'Yes. ADSL is an interim solution that will be with us for forty years.'라고 간파한대로 xDSL은 fiber가 좀 더 값싼 해결책이 될 때까지 당분간 access network에서 확고한 자리를 구축할 것으로 보인다. 최근들어 우리나라의 초고속정보통신망도 ADSL 과 VDSL을 바탕으로 FTTH으로 진화하는 전략을 수립한것은 우리의 현실과 세계적인 추세를 반영한 일이라 여겨진다.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.380-386
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• 2001

A nuclear microprobe system with adjustable precision object slits and a magnetic quadrupole doublet was designed by the beam optics simulation using a first order matrix formalism, and installed in a $30^{\circ}$ beam line connected with KIGAM 1.7 MV Tandem VDG Accelerator. Demagnification factors for x and y axis are calculated to be 25 and 4.9, respectively, and a minimum beam spot side is expected to be about 5 $\mu\textrm{m}$ for 3 MeV proton beams with a current of about 1 nA. A multi-purpose octagonal target chamber has been built to facilitate MeV ion-beam analytical techniques of PIXE, RBS, ERDA, and ion beam micro-machining. It contains X-ray and particle detectors, a zoom microscope, a Faraday cup, a 4-axis sample manipulator and a high vacuum pumping system. The system performance of the nuclear microprobe is now being tested, and automatic manipulator control and data acquisition system will be installed for routine applications of micro ion-beam analytical techniques.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2323-2328
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• 2012

Over the world, the development of critical technology for the safety and security of coastal distribution based on ubiquitous computing is being processed to meet the bottom lines of governmental regulations. Currently, 3D detectors using X-rays for freight search technology are being developed concerning U-based shipping security systems. In addition to that, there are increasing needs for developing portable radiation detector to detect gamma rays. The purpose of the thesis is to suggest the research of high speed portable gamma rays detector platform to prevent disorder caused to humans and public objects.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.138-144
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• 2013

In XRF systems, various techniques have been developed for the synthesis of pulse shapes using digital methods instead of traditional analog methods. Trapezoidal pulse shaping algorithms can be used for digital multi-channel pulse height analysis in X-ray spectrometer systems. In this paper, an efficient trapezoidal filter architecture is presented. In addition, we present a hardware-efficient peak value detection algorithm. By the proposed algorithm, peak value detection error is decreased by half compared with the conventional algorithm. The proposed Digital Pulse Processing(DPP) algorithm is designed using Verilog HDL and implemented using an FPGA on a test board. It is demonstrated that the implemented DPP board works successfully in practical XRF systems.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.422-427
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• 2014

This study provides a method to detect blood vessels shape using image processing techniques with the help of fluoroscopy equipments, providing high precision information about vessels' location and shape of inner path. It will assist for checking and monitoring the position of operating tools during vascular interventional treatment. The blood vessels shapes are gathered with X-ray images when a fluorescent medications are injected into patient's vessel and those images are processed for getting the boundaries of vessels. Then these data are merged with real-time CT-images. These image processing systems and procedures recognize the catheter, though continued computing algorithms are very useful for observer part on the automatic control system.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.326-326
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• 2013

본 연구에서는 회전 원통형 마그네트론 스퍼터링 시스템(Cylindrical Magnetron Sputtering)을 이용하여 성막한 Sn-doped $In_2O_3$ (ITO) 투명전극의 두께 변화에 따른 전기적, 광학적, 구조적 특성을 연구하였다. 회전 원통형 마그네트론 스퍼터링 시스템을 이용한 ITO 투명전극은 박막의 두께가 50~1,000 nm의 두께로 증가함에 따라 비저항 값은 일정하게 유지되나 면저항 값이 $37.8{\Omega}$/square로부터 $1.5{\Omega}$/square로 점차적으로 감소됨을 확인할 수 있었다. 또한 ITO 박막의 두께 증가가 50 nm에서 1,000 nm로 증가함에 따라 400~800nm 파장 범위에서 71~83％의 높은 광투과도를 나타내었다. 두께 변화에 따른 광학적 특성 변화를 설명하기 위해 Spectroscopic ellipsometry 분석을 실시하였으며 이를 기반으로 박막 두께와 투과도의 상관관계를 설명하였다. 한편, 원통형 마그네트론 스퍼터로 성장시킨 ITO 박막은 두께가 50~200 nm의 범위에서는 (222) 방향으로 우월 성장하였으나, 200-1000 nm 두께 범위에서는 우월 성장방향이 (400)과 (622)로 바뀜을 X-ray diffraction (XRD) 분석을 통하여 확인하였다. 이를 통해 박막의 두께변화에 따른 전기적/광학적 특성의 변화는 박막의 구조와 매우 밀접한 상관관계가 있음을 알 수 있었다.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.274-282
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• 1999

The In doped ZnO(ZnO:In)thin films sensitive to $NH_3$ gas were prepared by the double layer depositions of In film by vacuum evaporation and ZnO film by rf magnetron sputtering method onto a $SiO_2$/Si wafer substrate, and subsequent heat treatment process. The structural and electrical characteristics of the ZnO:In thin films were studied as a function of heat treatment temperature by x-ray diffraction, scanning electron microscope and 4 point probing method. And the dependence of the sensitivity, the selectivity and the time response of the thin films on heat treatment temperature was investigated. The thin film heat-treated at $400^{\circ}C$ showed the highest sensitivity of 140% at an operating temperature of $300^{\circ}C$. The sensitivity towards CO, $NO_x$, gases observed in the same temperature.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.371-379
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• 2014

In this study, we conducted a survey on the limited examinations of the DR system to the 30 radiologic technologists engaging in the clinical sites and university hospitals in Daejeon metropolitan city from Oct. 15, 2012 to Nov. 15, 2012. Based on the survey results, we propose the conceptual design of a supplementary table for the conventional DR system to extend the examination capability and overcome the limitation of DR system. And, we evaluated the convenience and usefulness of the proposed table by applying it to five subjects. Ten experts were involved to evaluate the clinical usefulness of the obtained images. In this study, the experimental results show the feasibility to overcome the limited examination of the conventional DR system, and the proposed supplementary table may be beneficial to patients and hospitals.