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Conceptual Design of a Table-top Terahertz Free-electron Laser
Y. U. Jeong,S. H. Park,K. Lee,J. Mun,K. H. Jang,J. Y. Lee,J. Sunwoo,김경남,Y.-H. Cha,B. H. Cha,D. H. Kim,G. M. Kazakevich 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.51
We have designed a table-top terahertz (THz) free electron laser (FEL). The main issue of the FEL design is to decrease radiation losses at the FEL resonator except outcoupling ratio. Also reducing the number of undulator periods and total undulator length is important to increase FEL conversion efficiency and to reduce its size. The FEL consists of a magnetron-based microtron having an energy of ∼5 MeV, a strong electromagnetic helical undulator having the period of ∼25 mm, and a cylindrical waveguide-mode optical resonator. The total diameter of the microtron is approximately 60 cm and the macropulse current is more than 50 mA. The condition for low-loss and high-gain oscillator of the table-top FEL has been studied by using a 2-D FEL code. Injection scheme of the electron beam to the undulator was optimized by calculating beam trajectories with a 3-D PIC code. The average THz power is calculated to be 1 W with the tunable wavelength range from 200 μm to 500 μm. The size of the system is expected to be 1 × 2 m<SUP>2</SUP>. The FEL is expected to be used for the real-time imaging of security inspection.
M. SHIN,M. SUNWOO 한국자동차공학회 2007 International journal of automotive technology Vol.8 No.1
This paper addresses the problem of period and priority assignment in networked control systems (NCSs) using a fixed priority scheduler. The problem of assigning periods and priorities to tasks and messages is formulated as an optimization problem to allow for a systematic approach. The temporal characteristics of an NCS should be considered by defining an appropriate performance index (PI) which represents the temporal behavior of the NCS. In this study, the sum of the end-to-end response times required to process all I/Os with precedence relationships is defined as a PI. Constraints are derived from the task and message deadline requirements to guarantee schedulability. Genetic algorithms are used to solve this constrained optimization problem because the optimization formulation is discrete and nonlinear. By considering the effects of communication, an optimum set of periods and priorities can be holistically derived.
DEVELOPMENT OF A NEW MISFIRE DETECTION SYSTEM USING NEURAL NETWORK
M. LEE,M. YOON,M. SUNWOO,S. PARK,K. LEE 한국자동차공학회 2006 International journal of automotive technology Vol.7 No.5
The detection of engine misfire events is one of major concerns in engine control due to its negative effect on air pollution and engine performance. In this paper, a misfire detection system based on crankshaft angular speed fluctuation is developed. Synthetic variable method is adopted for the preprocessing of crankshaft angular speed. This method successfully estimates the work output of each cylinder by finding the effect of combustion energy on the crankshaft rotational speed or acceleration after virtually removing the effect of the internal inertia forces from the measured crankshaft speed signals. The detection system is developed using neural network with the revised synthetic angular acceleration as input which is derived from the preprocessing. Mathematical simulation is carried out for developing and verifying the misfire detection system. Finally, the reliability of the developed system is validated through an experiment.
OPTIMAL PERIOD SELECTION TO MINIMIZE THE END-TO-END RESPONSE TIME
M. SHIN,W. LEE,M. SUNWOO 한국자동차공학회 2005 International journal of automotive technology Vol.6 No.1
This paper presents a systematic approach which determines the optimal period to minimize performance measure subject to the schedulability constraints of a real-time control system by formulating the scheduling problem as an optimal problem. The performance measure is derived from the summation of end-to-end response times of processed I/Os scheduled by the static cyclic method. The schedulability constraint is specified in terms of allowable resource utilization. At first, a uniprocessor case is considered and then it is extended to a distributed system connected through a commUnication link, local-inter network, LIN. This approach is applied to the design of an automotive body control system in order to validate the feasibility through a real example. By using the approach, a set of optimal periods can easily be obtained without complex and advanced methods such as branch and bound (B&B) or simulated annealing.
M. YOON,W. LEE,M. SUNWOO 한국자동차공학회 2005 International journal of automotive technology Vol.6 No.2
A distributed hardware-in-the-loop simulation (HILS) platform is developed for designing an automotive engine control system. The HILS equipment consists of a widely used PC and commercial-off-the-shelf (COTS) I/O boards instead of a powerful computing system and custom-made I/O boards. The distributed structure of the HILS system supplements the lack of computing power. These features make the HILS equipment more cost-effective and flexible. The HILS uses an automatic code generation extension, REAL-TIME WORKSHOP? (RTW?) of MATLAB? tool-chain and RT-LAB?, which enables distributed simulation as well as the detection and generation of digital event between simulation time steps. The mean value engine model, which is used in control design phase, is imported into this HILS. The engine model is supplemented with some I/O subsystems and I/O boards to interface actual input and output signals in real-time. The I/O subsystems are designed to imitate real sensor signals with high fidelity as well as to convert the raw data of the I/O boards to the appropriate forms for proper interfaces. A lot of attention is paid to the generation of a precise crank/cam signal which has the problem of quantization in a conventional fixed time step simulation. The detection of injection/command signal which occurs between simulation time steps are also successfully compensated. In order to prove the feasibility of the proposed environment, a simple PI controller for an air-to-fuel ratio (AFR) control is used. The proposed HILS environment and I/O systems are shown to be an efficient tool to develop various control functions and to validate the software and hardware of the engine control system.
-Synuclein pathology is related to postoperative delirium in patients undergoing gastrectomy
Sunwoo, M. K.,Hong, J. Y.,Choi, J.,Park, H. J.,Kim, S. H.,Lee, P. H. Ovid Technologies (Wolters Kluwer) - American Acad 2013 Clinical Neurophysiology Vol.80 No.9
<P>The clinical characteristics of postoperative delirium are similar to core features of α-synuclein-related cognitive disorders, such as dementia with Lewy bodies or Parkinson disease dementia. We therefore investigated the α-synuclein pathology in patients who experienced postoperative delirium after gastrectomy for stomach cancer.</P>
YOON M.,LEE W.,SUNWOO M. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.2
A distributed hardware-in-the-loop simulation (HILS) platform is developed for designing an automotive engine control system. The HILS equipment consists of a widely used PC and commercial-off-the-shelf (COTS) I/O boards instead of a powerful computing system and custom-made I/O boards. The distributed structure of the HILS system supplements the lack of computing power. These features make the HILS equipment more cost-effective and flexible. The HILS uses an automatic code generation extension, REAL-TIME WORKSHOP$^{ (RTW$^{) of MATLAB$^{ tool-chain and RT-LAB$^{, which enables distributed simulation as well as the detection and generation of digital event between simulation time steps. The mean value engine model, which is used in control design phase, is imported into this HILS. The engine model is supplemented with some I/O subsystems and I/O boards to interface actual input and output signals in real-time. The I/O subsystems are designed to imitate real sensor signals with high fidelity as well as to convert the raw data of the I/O boards to the appropriate forms for proper interfaces. A lot of attention is paid to the generation of a precise crank/ earn signal which has the problem of quantization in a conventional fixed time step simulation. The detection of injection! command signal which occurs between simulation time steps are also successfully compensated. In order to prove the feasibility of the proposed environment, a simple PI controller for an air-to-fuel ratio (AFR) control is used. The proposed HILS environment and I/O systems are shown to be an efficient tool to develop various control functions and to validate the software and hardware of the engine control system.
DEVELOPMENT OF A NEW MISFIRE DETECTION SYSTEM USING NEURAL NETWORK
Lee, M.,Yoon, M.,SunWoo, M.,Park, S.,Lee, K. The Korean Society of Automotive Engineers 2006 International journal of automotive technology Vol.7 No.5
The detection of engine misfire events is one of major concerns in engine control due to its negative effect on air pollution and engine performance. In this paper, a misfire detection system based on crankshaft angular speed fluctuation is developed. Synthetic variable method is adopted for the preprocessing of crankshaft angular speed. This method successfully estimates the work output of each cylinder by finding the effect of combustion energy on the crankshaft rotational speed or acceleration after virtually removing the effect of the internal inertia forces from the measured crankshaft speed signals. The detection system is developed using neural network with the revised synthetic angular acceleration as input which is derived from the preprocessing. Mathematical simulation is carried out for developing and verifying the misfire detection system. Finally, the reliability of the developed system is validated through an experiment.
Shin, M.,SunWoo, M. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.1
This paper addresses the problem of period and priority assignment in networked control systems (NCSs) using a fixed priority scheduler. The problem of assigning periods and priorities to tasks and messages is formulated as an optimization problem to allow for a systematic approach. The temporal characteristics of an NCS should be considered by defining an appropriate performance index (PI) which represents the temporal behavior of the NCS. In this study, the sum of the end-to-end response times required to process all I/Os with precedence relationships is defined as a PI. Constraints are derived from the task and message deadline requirements to guarantee schedulability. Genetic algorithms are used to solve this constrained optimization problem because the optimization formulation is discrete and nonlinear. By considering the effects of communication, an optimum set of periods and priorities can be holistically derived.