Skin entrance dose for digital and film radiography in Korean dental schools

Cho, Eun-Sang,Choi, Kun-Ho,Kim, Min-Gyu,Lim, Hoi-Jeong,Yoon, Suk-Ja,,Kang, Byung-Cheol 대한구강악안면방사선학회 2005 Imaging Science in Dentistry Vol.35 No.4

Purpose : This study was aimed to compare skin entrance dose of digital radiography with that of film radiography and to show the dose reduction achievement with digital systems at 11 dental schools in Korea. Materials and Methods : Forty six intraoral radiographic systems in 11 dental schools were included in this study. Digital sensors were used in 33 systems and film was used in 13 systems. Researchers and the volunteer visited 11 dental schools in Korea. Researchers asked the radiologic technician (s) at each school to set the exposure parameters and aiming the x-ray tube for the periapical view of the mandibular molar of the volunteer. The skin entrance doses were measured at the same exposure parameters and distance by the technician for each system with a dosimeter (Multi-O-Meter : Unfors instruments, Billdal, Sweden). Results : The median dose was 491.2 μGy for digital radiography and 1,205.0 μGy for film radiography. The skin entrance dose digital radiography was significantly lower than that of film radiography (p<0.05). Conclusion : Fifty-nine percent skin entrance dose reduction with digital periapical radiography was achieved over the film radiography in Korean dental schools.

윈도우 분석법을 이용한 이동로보트의 장애물 회피와 경로계획

조규상 동양대학교 1998 동양대학교 논문집 Vol.4 No.1

PFM(Potential Field Method)에서는 전위의 균형상태에서 이동로보트가 이동하지 못하는 지역최소점(local minima)에 도달하는 문제가 발생할 수 있다. 본 논문에서는 이런 문제가 발생하지 않으며 빠르고 간편한 방식으로 로보트가 장애물 회피를 할 수 있는 윈도우 분석법을 이용한 새로운 장애물 회피와 경로계획 알고리듬 알고리듬을 제안한다. 미지의 경로상에서 주어진 크기의 장애물 윈도우에서의 특징을 이용하여 안전한 주행 경로를 선택하며 장애물 회피를한다. 시뮬레이션의 결과를 통하여 이 방법의 신뢰성과 우수성을 입증한다. In conventional Potential Field Method(PFM), a problem of local minima that a mobile robot stuck at a point can take place. In this paper, a new on-line local path planning algorithm called Window Analysis Method(WAM) which has a gird type window is proposed. This method has a feature that is simple and fast, and that can take a safe path and avoids obstacles in unknown environment. WAM has simulated on the mobile robot to demonstrate its reliability and feasibility.

2차원 Laplace 변환 경계요소법에 의한 이종재료의 충격해석

조상봉,김태규,임호성 慶南大學校 附設 工業技術硏究所 1993 硏究論文集 Vol.11 No.-

이종재료의 충격문제를 해석하기 위하여 기존의 단일영역 2차원 Laplace 변환 경계요소법 프로그램에 접합경계에서 완전결합조건을 이용한 다중영역 결합법을 부가하여 이종재료의 동적문제가 해석가능하도록 프로그램을 작성하였다. 등방성 재료에 대한 정적 및 동적문제에서 단일영역에 의한 해석 결과와 영역결합법에 의한 해석 결과가 잘 일치함을 확인하였다. 이종재료의 해석에 2차원 Laplace 변환 경계요소법 프로그램을 응용하여 몇가지 모델을 해석하였고, 해석결과를 물리적인 측면에서 타당성을 분석하여 이종재료의 충격해석이 가능함을 확인하였다. For BEM analyses of the impact problems of dissimilar materials, the method of connected multi-regions using perfect bonded conditions on the interface boundaries was implemented to the two-dimensional Laplace transformed-domain BEM program for a single-region and multi-regions for a homogeneous isotropic material are consistent well. The two-dimensional Laplace transformed-domain BEM program with the method of connected multi-regions was applied to analyse several impact problems of dissimilar materials and it was confirmed the possibility of BEM impact analyses for dissimilar materials by the analysis of the BEM results for impact problems of dissimilar materials on physical grounds.

처분장근처에서 침식에 의한 Sr 화학종의 평형

조윤정,김성현,이인화,김시욱,고문주,박성규,이범규 조선대학교 환경공해연구소 2000 環境公害硏究 Vol.16 No.1

Leaching and adsorption equilibria of Sr Chemical Species from the near field of a repository has been studied in solidified cement with Fe and oxidized Fe. The absorption percent, Ads %, and distribution coefficient, K_(d) were calculated using equilibrium concentration to predict the extent of leaching and adsorption. In the mixed aqueous solutions the Ads % increase as Cement(C)/Water(W) ratios increase and K_(d) was decreased for Sr. These behaviors were discussed by adsorption and equilibrium of spiked ions. Oxides Fe promoted the adsorption of spiked ions, but pure Fe had no effect. E_(h) values were also estimated and discussed to elucidate oxidation-reduction environment of experimental system.

궤환 선형화에 적용한 신경회로망 제어기 설계법

조규상 동양대학교 1999 동양대학교 논문집 Vol.5 No.1

In this paper, the design of a feedback linearization controller using multilayer neural networks is proposed. The existing neural network based feedback linearization controller is mainly implemented by using an inverse function of nonlinear system. However, the proposed feedback linearization control scheme is designed by finding Lie derivatives from an identified networks. The Lie derivatives are expressed as a combination of weights and neuron output. The proposed method is applied to an antenna arm problem and the simulation results show performance comparisons between the ordinary feedback linearization and the proposed method.

STD-11 와이어 컷 방전가공시 가공조건에 따른 북현상 고찰

조규재,김선진,조상현,김훈희 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

From the experimental study of W-EDM for alloyed steel STD-11, the characteristics such as Hand Drum Form and surface roughness have been observed and evaluated for various conditions. In square hole, the increase of IP as to made condition, the calculate high value of surface roughness. Also compare dimensionless square hole with circle hole' graph. In circle hole, if a value of surface roughness IP 6 in a side of circle it show a 0.4㎛ and in IP 8, 0.6㎛, in IP 10, 0.7㎛, in IP 12, 0.8㎛ higher than before. This figure show the surface roughness is higher than before, because a table move in either X-axis or Y-axis in square hole, on the contrary, in circle there table move in X-axis and Y-axis at the same time, hand drum form getting small when wire tension increase 1000gf to 1500gf, at the same working conditions, the smaller of off time, the maller of hand drum form in same condition and same wire tension. but if you compare square hole with circle hole' graph, hand drum form displayed in maintained term of working condision, on the contrary, in case of square hole variation of hand drum form is more increase than a grow of IP

지역최소 회피를 위한 이동로봇의 경로계획

조규상 東洋大學校 産業技術硏究所 1999 東洋大學校 産業技術硏究所 論文集 Vol.1 No.1

This paper proposes a path planning of two wheeled mobile robot for avoiding local minima. A circular obstacle detection window helps a robot take a safe path avoiding unknown obstacles in an unknown environment. Detected obstacles in the window used to calculate steering angle and calculate radius of safe angular velocity. An algorithm for escaping local minima is presented also. This has simulated on the mobile robot to demonstrate its reliability and feasibility.

北美 自由貿易協定(NAFTA)이 우리 貿易에 미치는 影響 : 纖維·衣類 産業과 電子 産業을 中心으로

趙相菊,金圭昌,裵基烈 효성여자대학교 산업경영연구소 1994 경영경제 Vol.11 No.-

USB I/O를 사용하는 산업용 제어기의 설계 및 제작

조규상,이종운 동양대학교 산업기술연구소 2001 東洋大學校 産業技術硏究所 論文集 Vol.3 No.1

PLC or PC I/O cards those are generally used in an industrial machines have some weak points. In this paper, to overcome these weak points, an industrial I/O controller using USB bus is designed and implemented and it has the features, such as, a shortened wiring, an ease of use, and a competitive price. Cypress' Ezusb chip, USB embeded microprocessor, is used to develop its hardware. Driver program for Widows are designed by using WDM(Windows Driver Model), And a library programs and sample application software are developed for user's convenience using Visual C++.

생체내 심근허혈-재관류 모델에서 멜라토닌의 재관류 부정맥에 대한 심근보호작용에 관한 연구

조규종,김원,홍정석,이미우,장성은,오세현,임경수 대한응급의학회 2001 대한응급의학회지 Vol.12 No.4

Background: Recently, a few studies demonstrated that melatonin reduced the severity of myocardial reperfusion injuries, such as reperfusion arrhythmias. However, it is uncertain whether the melatonin reduces reperfusion arrhythmias in thus anesthetized animals because results were obtained using isolated hearts. Thus, to see whether melatonin reduces reperfusion arrhythmias in anesthetized animals, we examined the effect of melatonin on the incidence of reperfusion arrhythmias in an anesthetized-cat model of regional ischemia. Method: Adult mongrel male cats(n=30, 2.9∼4.2 kg) were anesthetized under positive-pressure artificial ventilation with room air. The animals of the control group(n=15) were subjected to 20-minute left anterior descending coronary artery(LAD) occlusion followed by abrupt reperfusion. The animals in experimental group(n=15) were divided into two. Group I(n=6) was pretreated with melatonin, 1 mg/kg, before occluding the LAD. Group II(n=9) was pretreated with melatonin, 10 mg/kg. The animals in experimental group were subjected to ischemia/reperfusion insult following drug treatment: melatonin was applied intra-peritoneally for 3 minutes just before LAD coronary artery ligation. The Fisher's exact test was used to compare the data from different animal groups. p<0.05 was considered significant. Results: The incidence of ventricular fibrillation(VF) during the reperfusion phase in group II(pretreated with melatonin, 10 mg) was significantly smaller than that in the control group(p-value = 0.0029). However, no statistically significant difference of VF incidence was found between group I(pretreated with melatonin, 1 mg) and the control group. Conclusion: Employing an anesthetized-cat model of regional cardiac ischemia, we investigated the dose-dependant effects of melatonin on reperfusion-induced arrhythmia. The cats pretreated with 10 mg/kg of melatonin before ischemia had a significantly reduced incidence of lethal reperfusion-induced arrhythmia, but there was no difference between the cats pretreated with 1 mg/kg of melatonin before ischemia and the control group.