양성자 치료에서 Moving Phantom을 이용한 Single Scan PBS와 Layered Rescanning PBS의 선량비교

김경태,김선영,김대웅,김재원,박지연,전상민,Kim, Kyeong Tae,Kim, Seon Yeong,Kim, Dae Woong,Kim, Jae Won,Park, Ji Yeon,Jeon, Sang Min 대한방사선치료학회 2019 대한방사선치료학회지 Vol.31 No.1

목 적: 움직이는 장기에 취약한 Pencil Beam Scanning(PBS)을 보완하기 위해 고안된 Layered Rescanning PBS 기법을 Moving Phantom에 적용하여 Single Scan PBS와 선량비교를 통해 Homogeneity를 비교해 본다. 대상 및 방법: Matrix X(IBA, Belgium)와 Moving Phantom(standard imaging, USA)을 이용하였다. 가상의 tumor $10{\times}10{\times}5cm$에 AP 방향에서 200 cGy의 선량을 조사하였다. 치료계획은 single scan PBS, rescan 4, 8, 12회 총 4가지로 하였고 각 치료계획별로 3번씩 반복 측정하였다. 측정 시 Moving Phantom의 호흡주기는 한 cycle당 4초로 설정 후 S-I 방향 움직임 2 cm으로 설정하였다. 추가로 beam on time을 측정하였다. 결 과: PTV 내에서 $D_{max}$의 평균값은 single scan, 4, 8, 12회 rescan 순서로 각각 $246.47{\pm}18.8cGy$, $223.43{\pm}8.92cGy$, $222.47{\pm}7.7cGy$, $213.9{\pm}6.11cGy$ $D_{min}$의 평균값은 각각 $165.53{\pm}4.32cGy$, $173.13{\pm}11.94cGy$, $184.13{\pm}8.04cGy$, $182.67{\pm}4.38cGy$으로 $D_{mean}$ $192.77{\pm}6.98cGy$, $196.7{\pm}4.01cGy$, $198.17{\pm}4.96cGy$, $195.77{\pm}3.15cGy$으로 측정되었다. 그리고 rescan 횟수가 늘어날수록 Homogeneity Index가 1에 가까워졌으며, beam on time은 평균 2분 15초, 3분 15초, 4분 30초, 5분 37초로 rescan 횟수가 증가할수록 치료시간이 증가되었다. 측정하는 과정에서 MU가 낮은 선량 layer에서는 설정한 rescan 횟수만큼 실제로 rescan하지 못하는 문제점이 발견되었다. 결 론: 장기 움직임이 있는 종양 치료 시 Layered Rescanning PBS을 적용했을 때 single scan PBS보다 균일한 선량분포를 확인할 수 있었다. 그리고 rescan 횟수가 증가할수록 균일한 선량분포를 보였다. single scan PBS와 12회 Layered rescanning 비교 시 HI 수치가 0.32 향상되었다. 추후 연구를 통하여 호흡동조 방사선치료가 불가능환자에게 적용이 가능할 것으로 사료된다. Purpose : We apply the Layered Rescanning PBS designed to complement the Pencil Beam Scanning(PBS), which is vulnerable to moving organs with the Moving Phantom, and compare the homogeneity with the single scan PBS. Methods and materials: Matrix X (IBA, Belgium) and Moving Phantom (standard imaging, USA) were used. A dose of 200 cGy was measured in the AP direction on a hypothetical tumor $10{\times}10{\times}5cm$. The plan type was planned as 4 kinds of sinlge scan PBS, rescan number 4, 8, 12 times. Were measured three times for each types. During the measurement, the respiratory cycle of the Moving Phantom was generally set to 4 seconds per cycle, and the movement radius in the S-I direction was set to 2 cm. In addition, beam on time was measured. Results : The mean values of $D_{max}$ in the PTV were $246.47{\pm}18.8cGy$, $223.43{\pm}8.92cGy$, and $222.47{\pm}7.7cGy$, $213.9{\pm}6.11cGy$ and the mean values of $D_{min}$ were $165.53{\pm}4.32cGy$, $173.13{\pm}11.94cGy$, $184.13{\pm}8.04cGy$, $182.67{\pm}4.38cGy$ and the mean values of $D_{mean}$ $192.77{\pm}6.98cGy$, $196.7{\pm}4.01cGy$, $198.17{\pm}4.96cGy$, $195.77{\pm}3.15cGy$ respectively. As the number of rescanning increased, the Homogeneity Index converged to 1. The beam on time was measured as 2:15, 3:15, 4:30, 5:37 on average. In the measurement process, in the low dose layer of the MU, the problem was found that it was not rescanned as many times as the set number of rescan. Conclusions : In the treatment of tumors with long-term movements, the application of layered rescanning PBS showed a more uniform dose distribution than single scan PBS. And as the number of rescan increase, the distribution of homogeneity is uniform. Compared with single scan plan and 12 rescan plan, HI value was improved by 0.32. Further studies are expected to be applicable to patients who can not be treated with respiratory synchronous radiation therapy.

탄소나노튜브가 분산된 비스무스 텔루라이드 기지 복합재료의 제조 및 열전특성

김경태,장경미,김경주,하국현,Kim, Kyung-Tae,Jang, Kyeong-Mi,Kim, Kyong-Ju,Ha, Gook-Hyun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2

Carbon-nanotube-embedded bismuth telluride (CNT/$Bi_2Te_3$) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with $Bi_2Te_3$ alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/$Bi_2Te_3$ composites by spark plasma sintering process at $350^{\circ}C$ for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the $Bi_2Te_3$ matrix. Seebeck coefficient of CNT/$Bi_2Te_3$ composites reveals that the composite has n-type semiconducting characteristics with values ranging $-55\;{\mu}V/K$ to $-95\;{\mu}V/K$ with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.

P형 열전분말의 수소환원처리가 상온열전특성에 미치는 영향

김경태,장경미,하국현,Kim, Kyung-Tae,Jang, Kyeong-Mi,Ha, Gook-Hyun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2

Bismuth-telluride based $(Bi_{0.2}Sb_{0.8})_2Te_3$ thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging $400\;nm\;{\sim}\;2\;{\mu}m$. The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at $350^{\circ}C$ for 10 min at the heating rate of $100^{\circ}C/min$ and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity ($0.8\;m{\Omega}{\cdot}cm$) than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.

젊은이들의 노래 차스뚜시까

김경태(Kim Kyeong Tae) 한국노어노문학회 2009 노어노문학 Vol.21 No.4

19세기 후반에 등장한 차스뚜시까는 새로운 장르의 구비문학이었다. 차스뚜시까는 내용의 전체적인 특징으로 볼 때 젊은이들의 장르라 할 수 있다. 차스뚜시까는 청소년부터 결혼 전 연령대까지의 청년과 아가씨들의 관심을 끄는 것들에 대해 노래하고 있기 때문이다. 사랑에 대한 동경, 수줍은 첫 고백과 첫 만남, 구애, 유혹, 데이트, 이별, 의심, 고뇌, 사랑에 빠진 연인들의 고통과 실망, 결혼에 대한 동경, 결혼의 성사 또는 결혼의 좌절 등이 차스뚜시까라는 사랑의 서정시를 수놓는 원천이다. 차스뚜시까는 20세기 농민 서정시에서 가장 중요한 자리를 차지하는 장르이다. 농촌사람들의 관점에서 바라보는 세상과 사람들 사이의 관계가 이 차스뚜시까안에 그대로 드러나 있기 때문이다. 차스뚜시까는 농민에게서 나왔고, 또 그들을 대상으로 한다. 차스뚜시까의 인물들은 땅을 일구고, 밭을 갈며 씨를 뿌리고, 풀을 베며 곡식을 거두고, 건초를 거두며 곡식을 빻고, 고기를 잡고, 오두막과 다리를 세우고, 나무를 하고, 이웃 마을로 놀러 다닌다. 하지만 도시는 차스뚜시까까의 인물들이 장을 보거나 돈을 벌기 위해 거처가게 되는 장소일 뿐이다. 도시는 차스뚜시까 인물들의 삶 속에서 겉모습만 드러나는 어떤 외부의 세계에 지나지 않는다. 차스뚜시까는 자연묘사나 일상적인 경제생활의 묘사는 비중있게 다루지 않는다. 하지만 인간의 운명에 깊이 개입되어 있기 때문에, 자연과 시골생활 면면에 대한 세세한 표현들은 노래하고, 눈물짓고, 기뻐하고, 괴로워하는 주인공들의 모습을 선명하게 보여준다. 혁명 전의 삶을 노래하는 차스뚜시까에서 나타난 시골 고향에 대한 애착은 20-30년대의 차스뚜시까들에서도 변함없이 찾아볼 수 있다. 하지만 시골 고향에 대한 태도는 종전 후 첫 10년간 현저히 달라진다. 연인들은 전장에서 영원히 돌아오지 않거나 도시에 남아 버렸으며, 사람들이 고향을 등지고 도시로 떠나기 시작한 것이다. 이제 고향은 처녀들에게 더 이상 사랑스러운 곳이 아니었다. 차스뚜시까에는 이제 고향을 떠나고 싶어 하는 내용이 속속 등장하고, 고향과 헤어지려는 모티브나 예전에는 타향에 불과했던 낯선 도시에서 보다 나은 삶과 자신의 자리를 차지하고픈 소원들이 목소리를 내기 시작한다. 이렇게 농민 차스뚜시까의 소멸이 시작되었다. 남녀 모두 함께 하는 거리놀이(총각들과 처녀들, 남정네들과 여인네들)에서 무례하고 거친 차스뚜시까는 전혀 환영받지 못했다. 농촌이 “청년들이 없는” 시기와 “처녀들이 없는” 시기를 거치면서, 남녀가 서로를 의식하며 차스뚜시까가 절제되고 고상한 내용을 유지하도록 하던 상호작용이 현저히 약화되었기 때문이다. 밤 모임이나 야유회가 사람들의 기억 속에서 완전히 멀어지고, 차스뚜시까가 시골이나 도시의 거리놀이에서 흥겨운 춤을 출 때만(젊은이들은 빠진 가운데) 겨우 불리어지면서, 차스뚜시까의 시대가 서서히 빛을 잃게 된다. Chastushka made its appearance as a new genre of Russian oral literature towards the end of the 19th century. The basic contents of Chastushka can be considered a Russian youth genre since the contents refer to the interests of young men and women between their adolescence and pre-marriedlife. The lyric poetry of Chastushka covered many themes of romance such as the longing for love, the insecurities with confessions of love and first meetings, courtships, temptations, dating, break-ups, doubts, anguish, the pain and disappointment for those who fall in love, the longing for marriage, the realization of marriage, and the setbacks of marriage. Chastushka occupies the most significant genre position within 20th century agrarian lyric poetry. Chastushka revealed the relationship as it truly exists between the world and people through the eyes of the farming community. Chastushka came from peasants and they were its characters. Chastushkan characters cultivated their land, plowed their fields and sowed their seeds, removed weeds and harvest grain, collected hay and ground grain, butchered meat, built sheds and bridges, cut firewood, and visited neighboring villages. However, Chastushkan urban characters merely traveled to local markets for food and earned money for a living. Chastushka was no longer a part of an individual’s economic life and lost its relevance as a natural portrayal of everyday life. Yet it remained deeply intertwined with the fate of man and Chastushka vividly expressed every aspect in detail between nature and rural life through the songs, tears, happiness, and suffering of its characters. The bond with one’s home village as sung in Chastushka concerning pre-revolutionary life did not change in Chastushka from the 20s and 30s. Young men never returned to their farms, instead remained in the cities, while others began leaving their homes in the country for the city. The countryside was no longer an area loved by youths. These sentiments concerning youths choosing to leave the country were included in Chastushka and the desire to part from one’s hometown for a new life in a strange city began to be told. This was the beginning of the disappearance of agrarian Chastushka. The crude and wild nature of Chastushka was not welcomed in the new lifestyles of men and women. As rural communities entered eras where there were either a lack of young men or a lack of young women, the lewd and wild character of Chastushka became considerably weaker. Chastushka became more and more a distant memory for those gathering at night or picnicking. Chastushka is almost exclusively sung in the country or city as fun and entertaining vital street performance and this is the image of Chastushka in the minds of many. This is the bias in which Chastushka is judged and it is reflected in author’s writings about it.

알파반수석고가 모르타르의 응결 및 건조수축에 미치는 영향

김경태(Kim, Gyeong Tae),김규용(Kim, Gyu Yong),이보경(Lee, Bo Kyeong),이상규(Lee, Sang Kyu),황의철(Hwang, Eui Chul),손민재(Son, Min Jae) 한국콘크리트학회 2017 한국콘크리트학회 학술대회 논문집 Vol.29 No.1

대규모 고신뢰 IoT 서비스를 위한 IEEE 802.15.4e TSCH 기반 MAC(Media Access Control) 프로토콜

김경태(Kyeong Tae Kim),김해용(Haeyoung Kim),박희웅(Huing Park),김선태(Seon-Tae Kim) 한국통신학회 2017 한국통신학회 학술대회논문집 Vol.2017 No.6

HVDC 컨버터의 Thyristor Valve 시험을 위한 새로운 합성시험회로

김경태(Kyeong-Tae Kim),한병문(Byung-Moon Han),정재헌(Jae-Hun Jung),노의철(Eui-Cheol Nho),정용호(Yong-Ho Chung),백승택(Seung-Taek Baek) 전력전자학회 2012 전력전자학회 논문지 Vol.17 No.3

센서 네트워크를 위한 경량 키 관리 프로토콜

김경태 ( Kyeong Tae Kim ),김형찬 ( Hyung Chan Kim ),( R. S. Ramakrishna ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.2

본 논문에서는 센서네트워크에서 키 관리 및 안전한 채널을 통한 개체 인증, 메시지의 기밀성 및 무결성을 보장하는 프로토콜을 제안한다. 제안된 프로토콜은 레벨기반의 트리 라우팅 프로토콜을 지원하여 외부 공격, 노드 실패, 그리고 노트 전복에 대하여 강인하며, 노드 상호간의 통신을 위하여 경량 키 관리 알고리즘을 사용하였다. 또한, In-networking 프로세싱을 통해 Data-aggregation 과 Trusted-delivery 메커니즘을 적용하여 가볍고, 견고한 특성을 지니고 있다. 제안된 프로토콜은 TinyOS/Mica 플래폼을 기반으로 TinySec 과 함께 구현된 결과를 제시한다.

하이브리드 연삭시스템 초음파 공구 개발

김경태(Kyeong Tae Kim),홍윤혁(Yun Hyuck Hong),박경희(Kyung Hee Park),이석우(Seok Woo Lee),최헌종(Hon Zong Choi),최영재(Young Jae Choi) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.11

Ultrasonic grinding system is that the ultrasonic vibration by ultrasonic actuator is applied on conventional grinding system during grinding process. The Ultrasonic vibration with a frequency of over 20kHz can reduce grinding forces and increase surface quality, material removal rate (MRR) and grinding wheel life. In addition, ultrasonic vibration assisted grinding can be used for the materials that are difficult to cut. In this paper, methodology for ultrasonic tools is studied based on finite element method, and in turn the ultrasonic tools are designed and fabricated. It is found that the ultrasonic tool can vibrate with a frequency of 20kHz and amplitude of 25μm. In order to verify the machining performance, the grinding experiment is performed on titanium alloy. By applying ultrasonic vibration, the grinding force and temperature are reduced and MRR is increased compared with the conventional grinding.

차세대 하이브리드 연삭시스템에 관한 연구

김경태(Kyeong-Tae Kim),박경희(Kyung-Hee Park),홍윤혁(Yun-Hyuck Hong),최헌종(Hon-Zong Choi),최영재(Young-Jae Choi) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4

In modern industry, grinding is one of the most important processes, especially for components used in high technology device. This is mainly because the grinding process can produce ultra precision parts in mass production system with high quality. Recently, the effort on development of multi-function grinding systems, called hybrid grinding systems, has been made for integration of the process, high efficiency and automation with high speed. In this paper, study on an ultrasonic assisted grinding system among the hybrid grinding systems was performed for an optimal design of ultrasonic grinding tool. Using FEM simulation, various types of ultrasonic horns were modeled for ultrasonic frequency of 20㎑ and maximum longitudinal amplitude based on predicting a natural frequency of the ultrasonic horn designed.