표면치밀화 기술에 의해 제조된 소결 기어의 기계적 특성

김기정,김기범,이두환,박종관,정동국,Kim, Ki-Jung,Kim, Ki-Bum,Lee, Doo-Hwan,Park, Jong-Kwan,Jeong, Dong-Guk 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3

A novel PM (powder metallurgy) steel for automotive power-train gear components was developed to reduce manufacturing cost, while meeting application requirements. The high-density PM steel was manufactured by mixing using special Cr-Mo atomized iron powders, high-pressure compaction, and sintering. Tensile strength, charpy impact, bending fatigue, and contact fatigue tests for the PM steel were carried out and compared to conventional forged steel. Pinion gears for auto-transmission were also manufactured by helical pressing, sintering, and surface densification process. In order to evaluate the durability of the PM parts, auto-transmission durability tests were performed using dynamometer tests. Results showed that the PM steel fulfilled the requirements for pinion gears indicating suitable tensile, bending fatigue, contact fatigue strengths and improved gear tooth profile. The PM gears also showed good performance during the transmission durability tests. As a result, the PM gears showed significant potential to replace the conventional forged steel gears manufactured by tooth machining (hobbing, shaving, and grinding) processes.

셀 분할 알고리즘과 확장 칼만 필터를 이용한 쿼드로터 복귀 실외 위치 추정

김기정,김윤기,최승환,이장명,Kim, Ki-Jung,Kim, Yoon-Ki,Choi, Seung-Hwan,Lee, Jang-Myung 한국전기전자학회 2013 전기전자학회논문지 Vol.17 No.4

본 논문은 쿼드로터의 최단거리 복귀 시 위치인식을 위해 확장칼만필터를(EKF) 이용한 저가형 GPS/INS 융합시스템과 셀 분할 알고리즘이 결합된 위치추정시스템을 제안한다. 연구에서는 저가형 GPS가 가지는 위치오차와 INS가 가지는 가속도 값의 계속적인 적분으로 인한 누적 오차를 줄이기 위해 확장칼만필터를 이용하여 GPS/INS 융합시스템을 구성한다. 또한 쿼드로터는 원점 복귀 명령 시 최단거리의 경로 지점에 대한 위치 경로 측정이 가능하기 때문에 위치 경로를 기준으로 셀 분할 알고리즘을 적용하여 GPS/INS 결합 데이터 중 실제 위치와 근접한 데이터를 결정함으로써 위치오차를 더욱 줄인다. 본 논문에서 제안하는 기법의 성능은 실외에서 쿼드로터 복귀 중 GPS, GPS/INS 결합, 셀 분할 알고리즘 적용 각각의 실험 결과를 비교함으로써 평가된다. This paper proposes a local estimation system which combines Cell Divide Algorithm with low-cost GPS/INS fused by Extended Kalman Filter(EKF) for localization of Quad-rotor when it returns to the departure point. In the research, the low-cost GPS and INS are fused by EKF to reduce the local error of low-cost GPS and the accumulative error of INS due to continuous integration of sensor error values. When the Quad-rotor returns to the departure point in the fastest path, a moving path can be known because it moves straight, where Cell Divide Algorithm is used to divide moving route into the cells. Then it determines the closest position of data of GPS/INS system fused by EKF to obtain the improved local data. The proposed system was verified through comparing experimental localization results obtained by using GPS, GPS/INS and GPS/INS with Cell Divide Algorithm respectively.

A Study on the Mitigation of the Exposure Dose Applying Bolus Tracking in Brain Perfusion CT Scan

김기정,정홍량,임청환,홍동희,심재구,유인규,Kim, Ki-Jeong,Jung, Hong-Ryang,Lim, Cheong-Hwan,Hong, Dong-Hee,Shim, Jae-Goo,You, In-Gyu The Society of Digital Policy and Management 2014 디지털융복합연구 Vol.12 No.3

급성기 허혈성 뇌졸중 증상이 있는 뇌 관류 CT 검사를 시행한 환자를 대상으로 장비사가 제시한 고정 시간 기법(Fixed time technique)과 조영제 추적 기법(Bolus tracking technique)을 비교하여 환자의 피폭선량을 분석하고자 하였으며, 조영제 추적 기법의 유용성과 최적의 조영증강 구간을 구현하는 Time graph를 알아보기 위한 것이다. 환자에서는 PCT의 $CTDI_{VOL}$은 고정시간기법에서 431.72mGy, Bolus tracking에서 323.61mGy로 측정되었고, DLP값은 고정시간기법에서 $1243.47mGy{\cdot}cm$, Bolus tracking에서 $932mGy{\cdot}cm$로 측정되었다. Time graph는 고정시간기법에서 다양하게 나타났으나, Bolus tracking 기법에서는 최적의 Time graph를 얻을 수 있었으며, 뇌 관류 CT검사 시 Bolus tracking기법을 적용하여 피폭선량을 25% 정도 감소시킬 수 있었다. This study was conducted to analyze the patient's exposed dose targeting the patients who had acute ischemic stroke symptoms and CT brain perfusion scan, by comparing fixed time technique and bolus tracking technique which was provided by the manufacturer and to identify the Time graph to implement the usability of contrast medium's tracking technique the best contrast enhancement intervals. $CTDI_{VOL}$ of PCT in patient appeared to be 431.72mGy in fixed scan delay protocol, whereas 323.61mGy in Bolus tracking technique. The value of DLP appeared to be $1243.47mGy{\cdot}cm$ in fixed scan delay protocol, whereas $932mGy{\cdot}cm$ in Bolus tracking technique. Time graph appeared to be various in fixed scan delay protocol, whereas the optimal time graph could be obtained in Bolus tracking. The exposure dose could be reduced by 25% applying Bolus tracking technique when taking brain perfusion CT scan.

영상처리와 확장칼만필터를 이용한 쿼드로터의 동적 물체 추종

김기정,유호윤,이장명,Kim, Ki-jung,Yu, Ho-Yun,Lee, Jangmyung 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.7

This paper proposes a new strategy for a quad-rotor to track a moving object efficiently by using image processing and an extended Kalman filter. The goal of path planning for the quad-rotor is to design an optimal path from the start point to the destination point. To lengthen the freight time of the quad-rotor, an optimal path is required to reduce the energy consumption. To track a moving object, the mark signed on the moving object has been detected by a camera mounted first on the quad-rotor. The center coordinates of the mark and its area are calculated through the blob analysis which is one type of image processing. The mark coordinates are utilized to obtain information on the motion direction and the area of the mark is utilized to recognize whether the object moves backward or forward from the camera on the quad-rotor. In addition, an extended Kalman filter has been applied to predict the direction and speed of the dynamically moving object. Through these schemes, it is aimed that the quad-rotor can track the dynamic object efficiently in terms of flight distance and time. Through the two different route freights of the quad-rotor, the performance of the proposed system has been demonstrated.

서울시 일부 가정주부들의 가정간병인제도 및 간병교육에 대한 수용태도에 관한 연구

김기정,장임원,Kim, Ki-Jung,Chang, Im-Won 대한예방의학회 1988 Journal of Preventive Medicine and Public Health Vol.21 No.2

This study was conducted in order to find out the attitude of housewives toward the home attendants system, the type of institute managing home attendants, the education for home attendants, the basic requisites for home attendants, and home nursing education, and identify the factors influencing on the housewives's attitude. The data were collected through questionnaires obtained from 401 housewives from March 1 to March 31, 1988. The results summarized were as follows; 1) 90.2 percent of total housewives favored the home attendants system, and housewives who had have their family member with health problem especially showed favorable response. 2) The favored types of institution managing home attendants appeared to be private social work agency(33.0%), half-private and half-public agency(32.2%), government agency(19.9%) and profit agency (2.2%). In particular, housewives who had experienced nursing favored half-private and half-public ageney (37.6%). 3) As the basic requisites for home attendants, housewives wanted service attitude(37.2%), nursing education(34.4%) and nursing experience(28.4%). But, housewives with nursing experience favored nursing education rather than service attitude. 4) 91.1% of total housewives favored the home nursing education. In particular, housewives of high education level and nursing experience showed more favorable response to the home nursing education.

전산화단층촬영검사실 방사선사의 방사선피폭 방어행위에 영향을 미치는 요인 분석

김기정,정홍량,홍동희,Kim, Ki-Jeong,Jung, Hong-Ryang,Hong, Dong-Hee 대한방사선과학회 2018 방사선기술과학 Vol.41 No.6

This study was conducted to analyze factors Influencing Protective Behavior against Radiation Exposure using questionnaires for 231 radiological technologists working in Computed Tomography(CT) examination room with high radiation dose in diagnostic radiology field. Statistical analysis of the collected data revealed that the reasons for partially shielding the examination part in the CT scan were the lack of protective equipment, securing of radiation justification, being annoying and maybe not being harm to adults in order. It was also revealed that the variables influencing the protective behavior were protective behavior against radiation harm, self-efficacy, protective environment, organization culture, protective knowledge and protective instrument in order. The higher the radiological protective environment(${\beta}=0.245$) and the lower the radiological protective knowledge(${\beta}=-0.034$), the more influential the protective behavior against radiation harm was. In this study, it was shown that non examination parts were not shielded in the CT scan. Therefore, it is necessary to improve the level of protective environment, to cultivate knowledge to improve the protective behavior against radiation harm and to have an intervention strategy for concrete action.

북한 붕괴시 다국적군 파병 가능성과 한국의 외교적 대응

김기정 한국전략문제연구소 1999 전략연구 Vol.6 No.3

One cannot think of any possible change in the international politics of East Asia without considering North Korea, which is surely a decisive variable determining stability and change in the regional security. This paper examines the regime crisis and possible alteration in the nature of North Korean regime. Therefore, a very starting point that this paper is concerned is possible collapse of North Korea and possibility of intervention by multinational forces, should any dramatic events occur. For the first part of the paper argues that, in forecasting North Korean collapse, the definition of collapse should be presented with more precise definition. When setting scenarios for the collapse of North Korea, its collapse scenario must be multidimensional rather than linear dimensional Not only the collapse of North Korea occurs due to a single factor but also it will not proceed in a single dimension. Distinguishing implosion and explosion tends to oversimplify and, moreover, ignore externality which accounts for foreign policies by surrounding states (the Us, Japan, Russia and China) toward North Korea. Considering externality implies that the Korean problem is influenced by the international community and especially North Koreas survival is much more determined by what types of foreign policy are exerted by the surrounding states in the region. The second part of the paper entails the actual scenarios of North Korea and examines possibilities of intervention by multi-national forces in the courses of the collapse. Collapse can be seen in the forms of socio-economic, political regime and system collapse. The socio-economic collapse entails the breakdown of food-rationing, surveillance and production systems. In it, the existing social stratification and class tension will be apparent. The collapse of political regime defines power struggles, military-coup and civil wars. The final phase of collapse is the demise of the system. Once the socio-economic and political foundation become obsolete, new fungible groups must come in to replace the old one. This is where the intervention of international community may be visible and gradual unification. may come into reality. Should North Korea collapse, the surrounding states (the Us, Japan, China and Russia) may intervene by claiming that their intervention is to secure the regional and international stability as well as their own national security. Each state may justify its decision based on prior-bilateral agreements that are formed either by North or by South Korea. The complex web of alliance pacts around the Korean peninsula may enable them to participate in the advent of the collapse. The US may intervene with the Time Phased Force Deployment under the Operation Plan 5027. The US may do so through its policy of engagement and enlargement. China, self-advocate to be a regional stabilizer, may intervene under the China-North Korea Pact, formed in 1961, which agrees to provide any necessary assistance, including military means, should any engaging party falls into invasion by other states. Japan can play its role under the new US-Japan New Guide Line which explicitly allows Japan to engage in the Non-combat Evacuation Operation (NEO) if any crisis occur in the region. As seen in the case of Somalia, Bosnia and East-Timor recently, the role of the United Nation may play decisively in implementing its peace keeping mission. The last part of the paper reviews the German experience, especially the foreign policies of the Kohl government in the phase of the German unification, which effectively dealt with and prevented any foreign intervention including the former Soviet Union. From this, the paper conclude with implications for the Korean foreign policy readiness: Korea should tighten its current alliance with the US and at the same time should be able to secure its unification initiatives independent of external influences. If not, Korea must at least minimize foreign intervention so as to maximize its interest and lead its national destiny as a unitary actor.

선형동기전동기 추진 자기부상시스템 동특성 해석

김기정(Ki-Jung Kim) 대한전기학회 2016 전기학회논문지 Vol.65 No.11

This paper deals with dynamic characteristics of the experimental magnetic levitation vehicle employing LSM(Linear Synchronous Motor) for propulsion. To predict the dynamic characteristics of the system, the dynamic model which is composed of the electrical elements such as electromagnets and LSM and mechanical components and is developed based on multibody dynamics is developed. The resulting system equations of motion for the model are a coupled one representing all the mechanical and electrical parts. To verify the dynamic model of the system, air gaps are measured in both running tests and simulation, and the frequency characteristics of air gaps are analyzed. From the results, it can be seen that the frequency responses are almost the same. Finally, to evaluate the levitation stability and the designed controller, numerical simulations are carried out.

영상처리와 확장칼만필터를 이용한 쿼드로터의 동적 물체 추종

김기정(Ki-jung Kim),유호윤(Ho-Yun Yu),이장명(Jangmyung Lee) 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.18 No.1

This paper proposes a new strategy for a quad-rotor to track a moving object efficiently by using image processing and an extended Kalman filter. The goal of path planning for the quad-rotor is to design an optimal path from the start point to the destination point. To lengthen the freight time of the quad-rotor, an optimal path is required to reduce the energy consumption. To track a moving object, the mark signed on the moving object has been detected by a camera mounted first on the quad-rotor. The center coordinates of the mark and its area are calculated through the blob analysis which is one type of image processing. The mark coordinates are utilized to obtain information on the motion direction and the area of the mark is utilized to recognize whether the object moves backward or forward from the camera on the quad-rotor. In addition, an extended Kalman filter has been applied to predict the direction and speed of the dynamically moving object. Through these schemes, it is aimed that the quad-rotor can track the dynamic object efficiently in terms of flight distance and time. Through the two different route freights of the quad-rotor, the performance of the proposed system has been demonstrated.

가이드웨이 횡변형의 자기부상열차 안내특성에의 영향 분석

김기정(Ki-Jung Kim),이재경(Jae-Kyoung Lee),한형석(Hyung-Suk Han),양석조(Seok-Jo Yang) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.11

자기부상철도에서 전체 투자비의 약 70%를 차지하는 가이드웨이의 건설비를 줄이고 미관을 향상시키기 위하여 가이드웨이의 경량화가 요구된다. 그에 따라서 가이드웨이의 변형이 증가하며 그 변형에 의한 부상안정성과 안내성능 영향을 분석할 필요가 있다. 본 논문에서는 가이드웨이의 구조물의 횡변형과 레일의 수평불규칙도에 의한 차량의 안내 특성에의 영향성 분석에 목적을 두고 있다. 이를 위하여 가이드웨이 횡변형을 포함하는 3 차원 모델의 이용이 제안된다. 제안된 가이드웨이와 차량이 통합된 동적 해석 모델을 이용하여 가이드웨이 횡변형에 의한 차량의 안내특성 분석을 수행하였다. 해석 결과 가이드웨이 거더의 횡변형에 의한 효과는 미비하지만 가이드웨이 레일의 횡방향 불규칙도에 대해서는 속도에 따라 영향을 받는 것을 알 수 있었다. 따라서 타당한 레일의 횡 불규칙도 설계 공차의 제한이 필요함을 알 수 있다. A slender guideway is essential in improving aesthetically and reducing its construction cost which accounts for about 70% of overall investment for maglev system. As the slender guideway, however, may increase its deformation, its effect on levitation stability and guidance performance needs to be analyzed. The purpose of this study is to analyze the effect on guidance characteristics of maglev due to the lateral deformation of the guideway girder and lateral irregularity of guiderail. For doing this, 3D model considering lateral deformation of girder and irregularity of rail of the guideway is developed. Using the dynamic interaction model integrated with the proposed guideway and maglev vehicle including electromagnetics and its controller, guidance characteristics of maglev are analyzed. It is analyzed that the effect on lateral deformation of girder is relatively small compared to deformation on the lateral irregularities of guiderail.