• Journal of Ubiquitous Convergence Technology
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• 제2권2호
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• pp.78-87
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• 2008

Received signal strength indicator (RSSI) is used as one of the ranging techniques to locate dynamic sensor nodes in wireless sensor network. Before it can be used for position estimation, RSSI values must be converted to distances using path loss model. These distances among sensor nodes are combined using trilateration method to find position. This paper presents an idea which attempts to integrate both path loss model and trilateration as one algorithm without going through RSSI-distance conversion. This means it is not simply formulas combination but a whole new model was developed. Several advantages were found after integration: it is able to reduce processing load, and ensure that all values do not exceed the maximum range of 16-bit signed or unsigned numbers due to antilog operation in path loss model. The results also show that this method is able to reduce estimation error while inaccurate environmental parameters are used for RSSI-distance conversion.

• Bulletin of the Korean Chemical Society
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• 제26권10호
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• pp.1505-1511
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• 2005

The excitation energy transfer process occurring in energy donor-acceptor linked porphyrin array system is theoretically simulated using the on-the-fly filtered propagator path integral method. The compound consists of an energy donating meso-meso linked Zn(II) porphyrin array and an energy accepting 5,15-bisphenylethynylated Zn(II) porphyrin, in which the donor array and the acceptor are linked via a 1,4-phenylene spacer. Real-time path integral simulations provide time-evolution of the site population and the excitation energy transfer rate constants are determined. Simulations and experiments show an excellent agreement indicating that the path integration is a useful tool to investigate the energy transfer dynamics in molecular assemblies.

• Ocean Systems Engineering
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• 제1권3호
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• pp.249-261
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• 2011

The stochastic nonlinear dynamic behavior and probability density function of ship rolling are studied using the nonlinear dynamical systems approach and probability theory. The probability density function of the rolling response is evaluated through solving the Fokker Planck Equation using the path integral method based on a Gauss-Legendre interpolation scheme. The time-dependent probability of ship rolling restricted to within the safe domain is provided and capsizing is investigated from the probability point of view. The random differential equation of ships' rolling motion is established considering the nonlinear damping, nonlinear restoring moment, white noise and colored noise wave excitation.

• 대한기계학회논문집
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• 제13권3호
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• pp.479-489
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• 1989

본 논문에서는 Ｊ$_{1}$,Ｊ$_{2}$ 적분과 Ｋ$_{I}$,Ｋ$_{II}$ 사이의 완전한 관계를 좁은 직사각형 경로를 택하여 간판하게 유도하였다. 그리고 유한요소의 해로 Ｊ$_{2}$적분을 효율적으로 계산하는 방법을 제시하였다.이미 해가 존재하는 문제 를 본 방법으로 다루어 그 결과를 비교하였고 일방향(unidirectional) 적층판 cantil- ever 평판 내의 single edge crack에 대한 해를 제시하였다.

• 인터넷정보학회논문지
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• 제7권4호
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• pp.23-32
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• 2006

본 논문에서는 최근 방대해지는 XML문서의 효율적인 관리를 위해서 노드 범위와 Pre-Order List를 이용한 XML문서들의 인덱싱 기법을 제안한다. 기존의 제안된 인덱싱 기법들은 크게 패스(Poth)와 넘버링(Numbering)을 기반으로 하고 있다. 그러나, 패스기반의 인덱싱 기법은 중간 노드와 최하위 노드의 검색과 조상-후손관계의 조인연산에 의해 효율이 떨어지는 단점을 가진다. 또한, 넘버링기반의 방법은 XML문서의 모든 노드에 번호를 부여하기 때문에 검색-오버헤드가 증가하는 문제를 가지며, 인덱스를 위해 많은 공간이 낭비된다. 따라서 본 논문에서는 이러한 문제점들을 해결하기 위해서 모든 XML문서에 노드범위 (Node Range)와 Pre-Order List를 이용한 인덱싱 기법을 제안한다. 이 방법은 유사한 구조의 XML문서가 많을수록 인덱스의 크기를 효과적으로 줄일 수 있으며, 검색 성능을 효율적으로 높일 수 있다. 또한 XML문서의 삽입, 삭제가 용이하다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1993년도 추계학술대회발표논문집; 서강대학교, 서울; 25 Sep. 1993
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• pp.24-30
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• 1993

When modeling a complex system we use an event tree to analyze propagation of failure. An event tree cannot represent the statistical interrelationships among parameters, but it can be represented as a statistically identical influence diagram so that parameter updating can be easily performed. After updating parameters we can calculate posterior distribution of the failure rate for each path. But exact distribution requires considerably complex numerical integration. We propose an approximation method to calculate the posterior and derive the predictive distribution of the time to next failure. Finally we introduce the system which implements our methodology.

• 대한기계학회논문집
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• 제18권6호
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• pp.1455-1464
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• 1994

A new and efficient algorithm for the integration of the thermal-elasto-plastic constitutive equation is proposed. While it falls into the category of the return mapping method, the algorithm adopts the three point approximation of plastic corrector within one time increment step. The results of its application to a von Mises-type thermal-elasto-plastic model with combined hardening and temperature-dependent material properties show that the accurate iso-error maps are obtained for both angular and radial errors. The accuracy achieved is because the predicted stress increment in a single step calculation follows the exact value closely not only at the end of the step but also through the whole path. Also, the comparison of the computational time for the new and other algorithms shows that the new one is very efficient.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.33-36
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• 2006

This paper describes an efficient optimal design method for an arrayed waveguide grating (AWG) with flattened transfer function. The objective function is the norm of the difference between calculated and target spectra. To analyze the AWG transfer function, the Fresnel-Kirchhof diffraction formula was employed and the design variable was optical path difference of each array waveguide. The (1+1) Evolution Strategy was applied to an eight-channel coarse wavelength division multiplexing (CWDM) AWG as the optimization tool. The optimized transfer function will considerably improve the system performance.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.15-20
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• 2010

This paper deals with minimizing layout area of FPGA design. FPGAs are becoming increasingly important in the design of ASICs since they provide both large scale integration and user-programmability. This paper describes a method to obtain tight bound on the worst-case increase in area when drivers are introduced along many long wires in a layout. The area occupied by minimum-area embedding for a circuit can depend on the aspect ratio of the bounding rectangle of the layout. This paper presents a separator-based area-optimal embeddings for FPGA graphs in rectangles of several aspect ratios which solves the longest path problem in the constraint graph.

• ETRI Journal
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• 제45권5호
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• pp.746-757
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• 2023

This study presents a novel safe landing algorithm for urban drone deliveries. The rapid advancement of drone technology has given rise to various delivery services for everyday necessities and emergency relief efforts. However, the reliability of drone delivery technology is still insufficient for application in urban environments. The proposed approach uses the "landing angle control" method to allow the drone to land vertically and a rapidly exploring random tree-based collision avoidance algorithm to generate safe and efficient vertical landing paths for drones while avoiding common urban obstacles like trees, street lights, utility poles, and wires; these methods allow for precise and reliable urban drone delivery. We verified the approach within a Gazebo simulation operated through ROS using a six-degree-of-freedom drone model and sensors with similar specifications to actual models. The performance of the algorithms was tested in various scenarios by comparing it with that of stateof-the-art 3D path planning algorithms.