• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2064-2071
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• 2020

For proton pencil beam scanning (PBS) technology, the accuracy of the dose distribution in a patient is sensitive to the properties of the incident beam. However, mechanical deformation of the proton therapy facility may occur, and this could be an important factor affecting the proton dose distribution in patients. In this paper, we investigated the effect of deformation on an SC200 proton facility's beam isocenter properties. First, mechanical deformation of the PBS nozzle, L-shape plate, and gantry were simulated using a Finite Element code, ANSYS. Then, the impact of the mechanical deformation on the beam's isocenter properties was evaluated using empirical formulas. In addition, we considered the simplest case that could affect the properties of the incident beam (i.e. if only the bending magnet (BG3) has an error in its mounting alignment), and the effect of the beam optics offset on the isocenter characteristics was evaluated. The results showed that the deformation of the beam position in the X and Y direction was less than 0.27 mm, which meets the structural design requirements. Compared to the mechanical deformation of the L-shape plate, the deformation of the gantry had more influence on the beam's isocenter properties. When the error in the mounting alignment of the BG3 is equal to or more than 0.3 mm, the beam deformation at the isocenter exceeds the maximum accepted deformation limits. Generally speaking, for the current design of the SC200 scanning beam delivery system, the effects of mechanical deformation meet the maximum accepted beam deformation limits. In order to further study the effect of the incident beam optics on the isocenter properties, a fine-scale Monte Carlo model including factors relating to the PBS nozzle and the BG3 should be developed in future research.

• 한국전자파학회논문지
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• 제17권7호
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• pp.659-664
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• 2006

본 논문에서는 $0.12{\mu}m$ 게이트 전극을 가진 metamorphic InAIAs/InGaAs high electron-mobility transistors (mHEMT)를 이용하여 제작된 60 GHz push-push 발진기의 특성을 고찰하였다. 전극 길이가 $0.12{\mu}m$ 인 mHEMT는 700 mA/mm의 최대 전류, 600 mS/mm의 최대 전달정수, 170 GHz $f_T$, 그리고 300 GHz 이상의 $f_{MAX}$ 등 우수한 특성을 나타내었다. 두 개의 $6{\times}50{\mu}m$ 크기를 가지는 mHEMT 를 이용하여 제작된 발진기는 59.5 GHz 에서 6.3 dBm의 출력 전력과 -35 dBc 이상의 기저 주파수 억압도를 나타내었다. 페이즈 노이즈 (phase noise)는 발진 주파수의 1 MHz 오프셋에서 -81.2 dBc/Hz 의 특성을 나타내었다. 본 연구 결과는 60 GHz 대역에서 mHEMT를 이용하여 제작된 push-push 발진기로는 최대 출력을 나타낸 결과이며, 이 연구 결과는 상용화와 저가격에 InP HEMT 보다 유리한 mHEMT를 이용하여 고출력 발진기 특성을 얻을 수 있음을 보여준다.

• 한국인쇄학회지
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• 제31권1호
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• pp.51-64
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• 2013

When it comes to current growth trend for the printing process in Asia printing market, offset printing, gravure printing and screen printing are reduced respectively -4%, -19%, -55%. In judging from the fact, the change in the printing production system from mass production on small amount to small production on mass amount is the biggest issue. For this reason, digital printing shows the significant growth. According to the increase of the growth 78% for electro photography way and 67% for ink-jet, it's not enough to catch up with digital printing which is increasing as time goes by to equip with hardware like as digital press. There's been necessary to install the BOD(Book on Demand) system which is the advanced and regular publication edit solution based on web-to-print model in the prepress, and it has made the BOD system be considered in relation to maximization of efficiency and production. Therefore, this research tries to step forward from the POD concept, which is refired to "Print along with the ordered quantities, the ordered appropriate time and the demanded place", so that it could expand the range of the printing/publishing environment using the BOD system, the order-made publication based on automatically operating template. And it tried to make the relation to digital web press on ink-jet method which is adequate to "mass production on small amount" with such advanced concept. This research also aims to use actively BOD solution model to promote the productivity of labor, and then to produce the printings across all related industries, which means to manufacture maximally the products on the shortest time at minimum place through PC equipments.

• 한국산학기술학회논문지
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• 제10권1호
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• pp.58-66
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• 2009

본 논문은 전동기에서 기계적인 파라미터의 변화와 함께 외란의 변화에 대하여 외란상쇄 피드포워드 루프 제어를 적용한 유도전동기의 벡터제어를 고려하였다. 제안한 시스템에서 부하토크는 유도전동기의 토크를 최소차원 상태관측기를 근거로 하여 추정한다. 최소차원 상태관측기를 통해 추정된 부하토크에 의해 토크 전류를 얻어내고 토크 전류분을 피드포워드 보상해 줌으로서 외란에 의한 영향을 상쇄시켜 외란이 유입되거나 부하가 가변되는 등의 조건에서도 안정되게 동작하는 강인한 속도제어 시스템을 실현할 수 있다. 본 연구에서는 속도 센서가 없이 검출된 전압과 전류에 의해 속도를 추정하여 사용 하므로서 신뢰도를 높일 수 있도록 하였다. 제시한 제어기의 타당성을 입증하기 위하여 Matlab Simulink를 이용하여 시뮬레이션을 수행하여 타당성과 안정성을 검토하였고, 이를 실제 시스템을 구성하여 ADMC300를 이용하여 실험을 수행한 결과 기존의 시스템에 비하여 강인한 시스템으로 구동됨을 증명할 수 있었다.

• Journal of Welding and Joining
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• 제16권5호
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• pp.119-133
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• 1998

To implement full automation in pipe welding, it si most important to develop special sensors and their related systems which act like human operator when detecting irregular groove conditions. In this study, an automatic pipe Gas Metal Arc Welding (GMAW) system was proposed to full control pipe welding procedure with intelligent sensor systems. A five-axes manipulator was proposed for welding torch to automatically access to exact welding position when pipe size and welding angle were given. Pool status and torch position were measured by using a weld-pool image monitoring and processing technique in root-pass welding for weld seam tracking and weld pool control. To overcome the intensive arc light, pool image was captured at the instance of short circuit of welding power loop. Captured image was processed to determine weld pool shape. For weld seam tracking, the relative distance of a torch position from the pool center was calculated in the extracted pool shape to move torch just onto the groove center. To control penetration of root pas, gap was calculated in the extracted pool image, and then weld conditions were controlled for obtaining appropriate penetration. welding speed was determined with a fuzzy logic, and welding current and voltage were determined from a data base to correspond to the gap. For automatic fill-pass welding, the function of human operator of real time weld seam control can be substituted by a sensor system. In this study, an arc sensor system was proposed based on a fuzzy control logic. Using the proposed automatic system, root-pass welding of pipe which had gap variation was assured to be appropriately controlled in welding conditions and in torch position by showing sound welding result and good seam tracking capability. Fill-pass welding by the proposed system also showed very successful result by tracking along the offset welding line without any control of human operator.

• 한국전자파학회논문지
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• 제28권12호
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• pp.941-947
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• 2017

본 논문에서는 $0.35{\mu}m$ CMOS 공정으로 FRS 대역 무전기용 반송파 신호를 쿼드러쳐(Quadrature) 형식으로 출력하는 Fractional-N 위상 고정루프(PLL) 주파수 합성기를 설계 및 제작하였다. 설계한 주파수 합성기의 주요 블록은 전압 제어 발진기(VCO), 전하 펌프(CP), 루프 필터(LF), 위상 주파수 검출기(PFD) 그리고 주파수 분주기이다. VCO는 우수한 위상잡음과 전력 특성을 얻을 수 있는 LC 공진 방식으로 설계했고, CP는 참조 주파수에 따라 펌핑 전류를 조절할 수 있도록 설계하였다. 주파수 분주기는 16분주의 전치 분주기와 3차 델타-시그마 모듈레이터($3^{rd}$ DSM) 방식의 Fractional-N 분주기로 설계하였다. LF는 외부의 3차 RC 루프 필터로 구성하였다. 측정결과, 주파수 합성기의 동작 주파수 영역은 최소 460 MHz에서 최대 510 MHz이고, 출력전력으로는 약 -3.86 dBm을 얻었다. 출력의 위상잡음은 100 Hz offset 주파수에서 -94.8 dBc/Hz이며 위상 루프 고착 시간은 약 $300{\mu}s$이다.

• Journal of Communications and Networks
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• 제2권1호
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• pp.58-68
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• 2000

In this paper we introduce the correlation-aided distributed sample acquisition (CDSA) scheme for fast cell search in IMT-2000 W-CDMA cellular system. The proposed scheme incorporates the state symbol correlation process into the comparison-correction based synchronization process of the original DSA scheme to enable fast acquisition even under very poor channel environment. for its realization, each mobile station (MS) has to store in its memory a set of state sample sequences. which are determined by the long-period scrambling sequences used in the system and the sampling interval of the state samples. CDSA based cell search is carried out in two stages : First, the MS first acquires the slot timing by using the primary synch code (PSC) and then identifies the igniter code which conveys the state samples of the current cell . Secondly. the MS identifies the scrambling code and frame timing by taking the comparison-correction based synchronization approach and, if the identification is not done satisfactorily within preset time. it initiates the state symbol correlation process which correlates the received symbol sequence with the pre-stored state sample sequences for a successful identification. As the state symbol SNR is relatively high. the state symbol correlation process enables reliable synchronization even in very low chip-SNR environment. Simulation results show that the proposed CDSA scheme outperforms the 3GPP 3-step approach, requiring the signal power of about 7 dB less for achieving the same acquisition time performance in low-SNR environments. Furthermore, it turns out very robust in the typical synchronization environment where large frequency offset exists.

• 대한전자공학회논문지SD
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• 제46권4호
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• pp.72-78
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• 2009

본 논문에서는 $0.13{\mu}m$ CMOS 공정의 이득(Kvco) 제어 지연 단을 이용한 위상동기루프에 사용되는 저 위상잡음 CMOS 링 전압제어발진기를 설계 및 제작한다. 제안하는 지연 단은 출력 단자를 잇는 MOSFET을 이용한 능동저항으로 전압제어발진기의 이득을 감소시킴으로써 위상잡음을 개선한다. 그리고 캐스코드 전류원, 정귀환 래치와 대칭부하 등을 이용한다. 제안한 전압제어 발진기의 위상잡음 측정결과는 1.9GHz가 동작 할 때, 1MHz 오프셋에서 -119dBc/Hz이다. 또한 전압제어발진기의 이득과 전력소모는 각각 440MHz/V와 9mW이다.

• 한국전자통신학회논문지
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• 제6권1호
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• pp.7-12
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• 2011

본 논문은 1 V 미만의 전원 전압에서 저 위상잡음을 갖는 발진 신호의 발생에 적합한 차동 콜피츠 전압제어 발진기 (VCO: Voltage Controlled Oscillator) 회로를 제안한다. 제안된 회로는 전류원으로 인덕터를 사용함으로써 1 V 미만의 전원 전압에서 저 위상잡음의 발진을 보다 용이하게 한다. 공진기 손실을 보다 줄이기 위하여 단일 콜피츠 발진기의 두 개의 궤환 커패시터 중의 하나를 바렉터 (varactor)로 대체하였다. $0.18{\mu}m$ RF CMOS 기술을 사용하는 포스트 레이아웃 (post-layout) 시뮬레이션 결과는 0.6 V에서 0.9 V 사이의 전원 전압에서 제안된 회로가 1MHz 오프셋 주파수에서 나타내는 위상잡음은 널리 알려진 교차 결합 전압제어 발진기의 위상잡음보다 적어도 7 dBc/Hz 이상 낮음을 보여준다.

• 한국환경복원기술학회지
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• 제21권2호
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• pp.77-85
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• 2018

The intensive habitats loss of natural organisms as a consequence of anthropogenic activities has lead to the use of alternative habitats for species conservation. We reviewed the current status of alternative habitats and suggest the improvement of alternative habitats. Most of alternative habitats regarded in this study are not following the pre-arranged consultation at environmental impact assessment. These alternative habitats are rendered useless due to the insufficient consideration of ecological characteristics of species and lack of detailed plans. A number of alternative habitats are influenced by disturbance such as environmental pollution and construction. Post-monitoring of alternative habitats are needed to estimate immigration rate of species. Post management is also needed to assess the status of population stability. Overall, low effectiveness of alternative habitats is presented in this study. According to the status survey, methods for improvement of alternative habitats are required such as detailed guidelines, establishment of post-monitoring system, improvement of habitat restoration techniques, and guidelines for management and operation of alternative habitats.