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김영삼(Young-Sam Kim),탁민제(Min-Jea Tahk),유혁(Hyeok Ryu) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.8
본 논문에서는 추적-회피 게임의 해를 기반으로 한 유도법칙을 제안하고, 성능을 분석한다. 추적자를 유도하는데 게임 해의 초기 값을 사용하고, 다음 단계에서 추적-회피 게임의 해를 다시 계산한다. 이 점에 있어서 제안된 유도법칙은 모델예측제어와 유사하다. 회피자가 요격시간을 최대화하는 방향으로 항상 기동하는 추적-회피 시나리오에 대하여, 비례항법유도와 비교한 결과, 제안된 유도기법이 더 넓은 요격영역을 가진다는 것을 확인하였다. We propose a guidance law based on pursuit-evasion game solutions, and analyze its performance, The game solutions are obtained from the pursuit-evasion game solver developed by Tahk. The initial value of the game solution is used for guidance, and then the pursuit-evasion game is solved again at the next time step. In this respect, the proposed guidance laws are similar to the approach of model predictive control. The proposed guidance method is compared with proportional navigation guidance for a pursuit-evasion scenario, in which the evader always tries to maximize the capture time. According to the comparison, it has larger a capture set than ones of proportional navigation guidance law.
Rapid large area fabrication of multiscale through-hole membranes
Tahk, D.,Paik, S. M.,Lim, J.,Bang, S.,Oh, S.,Ryu, H.,Jeon, N. Royal Society of Chemistry 2017 Lab on a chip Vol.17 No.10
<P>There are many proposed mechanisms by which single cells can be trapped; among them is the through-hole membrane for the characterization of individual microorganisms. Due to the small scale of the fabricated pores, the construction of through-hole membranes on a large scale and with relatively large areas faces many difficulties. This paper describes novel fabrication methods for a large-area, freestanding micro/nano through-hole membrane constructed from versatile membrane materials using through-hole membranes on a microfluidic chip (THMMC). This process can rapidly (< 20 min) fabricate membranes with high fidelity multiscale hole size without residual layers. The through-hole site was easily customizable from the micro to the nanoscale, with a low or high aspect ratio giving rise to reliable membranes. Also, the rigidity and biocompatibility of the through-hole membrane are easily tunable by simple injection of versatile membrane materials to obtain a large area (up to 3600 mm(2)). Membranes produced in this manner were then applied as a proof of concept for the isolation, cultivation, and quantification of individual micro-algal cells for selection with respect to the growth rate, while controlling the quorum sensing mediated metabolic and proliferative changes.</P>
Tahk, Kyung-Mo,Shin, Kee-Hyun The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.12
Rollers in the continuous process systems are ones of key components that determine the quality of web products. The condition of rollers (e.g. eccentricity, runout) should be consistently monitored in order to maintain the process conditions (e.g. tension, edge position) within a required specification. In this paper, a new diagnosis algorithm is suggested to detect the defective rollers based on the frequency analysis of web tension signals. The kernel of this technique is to use the characteristic features (RMS, Peak value, Power spectral density) of tension signals which allow the identification of the faulty rollers and the diagnosis of the degree of fault in the rollers. The characteristic features could be used to train an artificial neural network which could classify roller conditions into three groups (normal, warning, and faulty conditions) The simulation and experimental results showed that the suggested diagnosis algorithm can be successfully used to identify the defective rollers as well as to diagnose the degree of the defect of those rollers.
A hybrid optimization method of evolutionary and gradient search
Tahk, Min-Jea,Woo, Hyun-Wook,Park, Moon-Su Gordon and Breach 2007 Engineering optimization Vol.39 No.1
<P> This article proposes a hybrid optimization algorithm, which combines evolutionary algorithms (EA) and the gradient search technique, for optimization with continuous parameters. Inheriting the advantages of the two approaches, the new method is fast and capable of global search. The main structure of the new method is similar to that of EA except that a special individual called the gradient individual is introduced and EA individuals are located symmetrically. The gradient individual is propagated through generations by means of the quasi-Newton method. Gradient information required for the quasi-Newton method is calculated from the costs of EA individuals produced by the evolution strategies (ES). The symmetric placement of the individuals with respect to the best individual is for calculating the gradient vector by the central difference method. For the estimation of the inverse Hessian matrix, symmetric Rank-1 update shows better performance than BFGS and DFP. Numerical tests on various benchmark problems and a practical control design example demonstrate that the new hybrid algorithm gives a faster convergence rate than EA, without sacrificing the capability of global search.</P>
Impact Time Control Based on Time-to-Go Prediction for Sea-Skimming Antiship Missiles
Tahk, Min-Jea,Shim, Sang-Wook,Hong, Seong-Min,Choi, Han-Lim,Lee, Chang-Hun IEEE 2018 IEEE transactions on aerospace and electronic syst Vol.54 No.4
<P>This paper proposes a novel approach for guidance law design to satisfy the impact-time constraints for a certain class of homing missiles. The proposed guidance law provides proper lateral acceleration commands that make the impact time error converge to zero by the time of impact. This scheme can be applied to any existing guidance law for which a formula of predicted time to go is available. Convergence of time-to-go errors is supported by Lyapunov stability. The optimal guidance law and the impact angle control guidance law are extended by the proposed method for impact-time-control guidance and impact-time-and-angle-control guidance, respectively. The performance of the extended guidance laws is demonstrated by numerical simulation.</P>
Perch Landing Assisted by Thruster (PLAT): Concept and Trajectory Optimization
Tahk, Min-Jea,Han, Seungyeop,Lee, Byung-Yoon,Ahn, Jaemyung The Korean Society for Aeronautical and Space Scie 2016 International Journal of Aeronautical and Space Sc Vol.17 No.3
A concept of the perch landing assisted by thruster (PLAT) for a fixed wind aircraft is proposed in this paper. The proposed concept is applicable to relatively large unmanned aerial vehicles (UAV), hence can overcome the limitation of existing perch landing technologies. A planar rigid body motion of an aircraft with aerodynamic and thruster forces and moments is modeled. An optimal control problem to minimize the fuel consumption by determining the histories of thruster and elevator deflection angle with specified terminal landing condition is formulated and solved. A parametric study for various initial conditions and thruster parameters is conducted to demonstrate the practicability of the proposed concept.
Hyun-tahk Chay 한국외국어대학교 영미연구소 2006 영미연구 Vol.14 No.-
This paper analyzes the East Asian (Chinese, Japanese, Korean) EFL learners’ overpassivization (OP) of the English ergative constructions (as in 1a) and transitivization of related intransitive verbs (as in 1b): 1 a. *What was happened yesterday? b. *He disappeared himself. Most EFL studies of individual languages (e.g., Masuko on Japanese; Chung on Korean) attribute the source of the errors mainly to the pragmatic factor, so called ADVERSITY PASSIVE. However, a close cross-linguistic investigation has shown that only the OP of event verbs is due to the adverse feelings common to the East Asian culture and that other types of OP and strange transitivization depend on L1-specific adverse feelings and whether intransitive verbs of concern can passivize in the L1.