Characteristics of Proton Beams and Secondary Neutrons Arising from Two Different Beam Nozzles

최연경,김유석 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.8

A tandem or a Van de Graaff accelerator with an energy of 3 MeV is typically used for Proton Induced X-ray Emission (PIXE) analysis. In this study, the beam line design used in the PIXE analysis, instead of the typical low-energy accelerator, was used to increase the production of isotopes from a 13-MeV cyclotron. For the PIXE analysis, the proton beam should be focused at the target through a nozzle after degrading the proton beams energy from 13 MeV to 3 MeV by using an energy degrader. Previous studies have been conducted to determine the most appropriate material for and the thickness of the energy degrader. From the energy distribution of the degraded proton beam and the neutron occurrence rate at the degrader, an aluminum nozzle of X thickness was determined to be the most appropriate nozzle construction. Neutrons are created by the collision of 3-MeV protons in the nozzle after passage through the energy degrader. In addition, a proton beam of sufficient intensity is required for a non-destructive PIXE analysis. Therefore, if nozzle design is to be optimized, the number of neutrons that arise from the collision of protons inside the nozzle, as well as the track direction of the generated secondary neutrons, must be considered, with the primary aim of ensuring that a sufficient number of protons pass through the nozzle as a direct beam. A number of laboratories are currently conducting research related to the design of nozzles used in accelerator fields, mostly medical fields. This paper presents a comparative analysis of two typical nozzle shapes in order to minimize the loss of protons and the generation of secondary neutrons. The neutron occurrence rate and the number of protons that pass through the nozzle were analyzed by using a Particle and Heavy Ion Transport code System (PHITS) program in order to identify the nozzle that generated the strongest proton beam.

‘지민바’에 놀러오세요!

최연경 샘터사 2017 월간 샘터 Vol.569 No.-

External Beam’s Nozzle Design for the CRC Cyclotron PIXE/PIGE

최연경,김유석 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.3

Recently, 13-MeV proton cyclotrons have been applied to non-destructive trace element analyticaltechniques, such as proton-induced X-ray emission (PIXE) and proton-induced gamma-ray emission(PIGE). A new extended beam line has been designed for PIXE/PIGE measurements in order todeliver protons to the target with minimal losses, thus reducing secondary radiation. A targetchamber for PIXE/PIGE measurements is installed at the end of the extended beam line, and thebeam size may be optimized by using a series of collimators that are located in front of the target. The optimized proton beam, with low currents (∼nA) for PIXE/PIGE experiments, requires a smallbeam size with variable energies from ∼10 keV to 3 MeV. Based on the ionization cross-sectioncurve, a 3-MeV proton beam has been determined to be suitable for PIXE/PIGE measurements. Therefore, the 13-MeV protons extracted from the cyclotron must be reduced to 3 MeV, and this isachieved through the incorporation of an energy degrader. The appropriate thickness of the energydegrader has been estimated by using the stopping range in matter (SRIM) program. Also, suitablematerials must be used for the construction of the collimator and the energy degrader in order tomeet the requirements of low neutron activation due to the application of protons. In this study,we evaluated a number of suitable materials with low neutron yields and with little energy spreadas the beam passes through the energy degrader and collimator. The appropriate thickness of theenergy degrader for the reduction of the proton energy from 13 MeV to 3 MeV was determinedusing the SRIM code. Also, the neutron yield at the nozzle was estimated using the MCNPX code.

Reconfigurable FPGA 시스템을 위한 위상기반 회로분할 ( Topology-Based Circuit Partitioning for Reconfigurable FPGA Systems )

최연경,임종석 대한전자공학회 1998 대한전자공학회 학술대회 Vol.1998 No.11

Metabolic Roles of AMPK and Metformin in Cancer Cells

최연경,박근규 한국분자세포생물학회 2013 Molecules and cells Vol.36 No.4

Metformin is one of the most widely used anti-diabetic agents in the world, and a growing body of evidence suggests that it may also be effective as an anti-cancer drug. Observational studies have shown that metformin reduces cancer incidence and cancer-related mortality in multiple types of cancer. These results have drawn attention to the mechanisms underlying metformin’s anti-cancer effects, which may include triggering of the AMP-activated protein kinase (AMPK) pathway, resulting in vulnerability to an energy crisis (leading to cell death under conditions of nutrient deprivation) and a reduction in circulating insulin/IGF-1 levels. Clinical trials are currently underway to determine the benefits, appropriate dosage, and tolerability of metformin in the context of cancer therapy. This review highlights fundamental aspects of the molecular mechanisms underlying metformin’s anti-cancer effects, describes the epidemiological evidence and ongoing clinical challenges, and proposes directions for future trans-lational research.

표준 셀 레이아웃 형태에서 기능 모듈 자동 생성

최연경 경민대학 산학기술연구소 2001 경민대학연구논총 Vol.2 No.1

This paper proposes a new functional module generator in the standard cell layout style. Traditional researches about cell generation try to minimize the width of the generated modules while considering the height manually. Nowadays cell height becomes an important factor because of arbitrary cell structure that comes from variable transistor sizes. We develope an automatic module cell generator which minimizes the area of the modules by considering both the cell height and the cell width. The developed generator efficiently generate functional module automatically and show improvement in the cell area compared to the previous results we've tested.

地域文化空間의 活性化方案

崔連卿 慶尙大學校 經營行政大學院 1991 最高管理者課程論文集 Vol.2 No.-

내분비-대사 : 새로운 MEN1 유전자 돌연변이를 동반한 제 1형 다발성 내분비 선종 1예 (초)

최연경,서현애,김종호,하인균,이정은,정지윤,전언주,김정국,이인규,김보완 대한내과학회 2010 대한내과학회 추계학술대회 Vol.2010 No.-

Field programmable circuit board를 위한 위상 기반 회로 분할

최연경,임종석 대한전자공학회 1997 電子工學會論文誌, C Vol.c34 No.2

In this paper, w describe partitioning large circuits into multiple chips on the programmable FPCB for rapid prototyping. FPCBs consists of areas for FPGAs for logic and interconnect components, and the routing topology among them are predetermined. In the partition problem for FPCBs, the number of wires ofr routing among chips is fixed, which is an additonal constraints to the conventional partition problem. In order to deal with such aconstraint properly we first define a new partition problem, so called the topologybased partition problem, and then propose a heuristic method. The heuristic method is based on the simulated annealing and clustering technique. The multi-level tree clustering technique is used to obtain faster and better prtition results. In the experimental results for several test circuits, the restrictions for FPCB were all satisfied and the needed execution time was about twice the modified K-way partition method for large circuits.

재구성 가능한 회로 보드를 위한 새로운 Quadratic Boolean Programming 수식에 의한 분할

최연경,임종석,Choe, Yeon-Gyeong,Im, Jong-Seok 대한전자공학회 2000 電子工學會論文誌-SD (Semiconductor and devices) Vol.37 No.2

본 논문에서는 IC(Integrated Circuits) 칩들간의 배선 위상(topology)이 정해진 재구성 가능한(reconfigurable) FPGA(Field Programmable Gate Array) 기반 보드로의 회로 분할 문제로써 새로운 quadratic boolean programming 수식(formulation)을 제안한다. 본 수식의 목적은 회로 분할 시 사용하는 핀수와 네트들의 배선 길이의 합을 최소화하는 것이며 기존의 분할 방법에서 고려하는 제약조건 외에 서로 인접하지 않은 IC 칩들을 연결하기 위하여 다른 IC 칩을 통과(pass through)하는 네트들에 의해 사용되는 핀수도 고려한다. 또한 본 논문에서는 제안한 분할 문제를 효율적으로 해결하기 위하여 모듈 할당 방법으로 구성되어 있는 휴리스틱(heuristic) 분할 방법을 제안한다. 입력된 회로에 대하여 다른 분할 방법과 비교하여 실험한 결과 분할 문제의 주어진 제한들을 모두 만족하였다. 대부분의 배선된 회로에 대하여 핀 사용률이 적게 나타났으며 네트들의 사용한 배선 길이의 합은 최대 34.7% 적게 나타났다. We propose a new formulation by quadratic boolean programming to partition circuits for FPGA based reconfigurable circuit boards, in which the routing topology among IC chips are predetermined. The formulation is to minimize the sum of the wire length by considering the nets passing through IC chips for the interconnections between chips which are not adjacent, in addition to the constraints considered by the previous partition methods. We also describe a heuristic method, which consist of module assignment method to efficiently solve the problem. Experimental results show that our method generates the partitions in which the given constraints are all satisfied for all the benchmark circuits tested. The pin utilization are reduced for the most of the circuits and the total wire length of the routed nets are improved up to 34.7% compared to the previous method.