• Journal of Korean Society of Transportation
• /
• v.23 no.7 s.85
• /
• pp.99-110
• /
• 2005

Total travel cost of route which connects origin with destination (O-D) is consist of the total sum of link travel cost and route perception cost. If the link perception cost is different according to the origin and destination, optimal route search has limitation to reflect the actual condition by route enumeration problem. The purpose of this study is to propose optimal route searching formulation and algorithm which is enable to reflect different link perception cost by each route, not only avoid the enumeration problem between origin and destination. This method defines minimum unit of route as a link and finally compares routes using link unit costs. The proposed method considers the perception travel cost at both origin and destination in optimal route searching process, while conventional models refect the perception cost only at origin. However this two-way searching algorithm is still not able to guarantee optimum solution. To overcome this problem, this study proposed an orign based optimal route searching method which was developed based on destination based optimal perception route tree. This study investigates whether proposed numerical formulas and algorithms are able to reflect route perception behavior reflected the feature of origin and destination in a real traffic network by the example research including the diversity of route information for the surrounding area and the perception cost for the road hierarchy.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2001.10a
• /
• pp.605-608
• /
• 2001

다층 신경망의 학습에 쓰이는 오류 역전파 학습은 매우 효과적이지만 학습 속도가 너무 느리고 최적의 은닉충의 뉴런의 수를 결정하는 해답은 아직 없는 실정이다. 또한 가끔은 국부 최소점(Local maxima)에 빠져 학습이 끝내 이루어지지 않는 경우가 있다. 이에 본 논문에서는 이러한 Local maxima 를 효과적으로 탈출 할 수 있는 방법에 대해서 연구해 보았다. 국부 최소점은 연결강도와 전체 오차 사이의 이차원 공간에서 표현할 수 있는데 본 알고리즘은 이러한 연결강도와 오차와의 관계를 인위적으로 변화시켜 결론적으로 Local maxima 를 탈출하게 하는 방법을 소개한다. 본 연구에서 사용된 방법은 네트웍이 학습중에 Local maxima 에 빠졌을 때 은닉층의 뉴런의 수를 추가하여 인위적으로 연결강도 평면의 위상을 변조시킨다. 또한 은닉충의 뉴런의 수를 동적으로 변화 시키면서 최적의 뉴런의 수를 결정할 수 있게 하였다. 위 알고리즘의 성능을 평가하기 위해서 XOR 문제와 $10{\times}8$ 영문폰트와 숫자의 학습에 적용하여 일반적인 역전파 학습과 비교 평가하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.3
• /
• pp.225-232
• /
• 2018

This paper proposed the optimization method of the extremely low numerical-dispersion finite-difference time-domain (ELND-FDTD) method based on the H(2,4) scheme for wideband and extremely accurate electromagnetic properties of lossy material, which has a constant conductivity and relative permittivity. The optimized values of three variables are calculated for the minimum numerical dispersion errors of the proposed FDTD method. The excellent accuracy of the proposed method is verified by comparing the calculated results of three different FDTD methods and the analytical results of the two-dimensional dielectric cylinder scattering problem.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.6 no.1
• /
• pp.18-22
• /
• 2013

Input impedance of the inverted L antenna which is modified from a monopole antenna varies to very high input impedance value when the ratio of vertical height to horizontal length is reduced. So its impedance matching becomes very difficult. In this paper, we analyzed the input impedance variation range depending on the ratio of vertical height to horizontal length in the normal and ferrite thin film added configuration for the input impedance control. For the exact analysis involving the permittivity, permeability and conductivity of ferrite material, FDTD numerical method is used.

• Resources Recycling
• /
• v.13 no.6
• /
• pp.26-30
• /
• 2004

Input impedance of the inverted L antenna which is modified from a monopole antenna varies to very high input impedance value when the ratio of vertical height to horizontal length is reduced. So its impedance matching becomes very difficult. In this paper, we analyzed the input impedance variation range depending on the ratio of vertical height to horizontal length in the normal and ferrite thin film added configuration for the input impedance control. For the exact analysis involving the permittivity, permeability and conductivity of ferrite material, FDTD numerical method is used.

• Journal of the Korean Geophysical Society
• /
• v.7 no.2
• /
• pp.151-155
• /
• 2004

To solve the urban flood problems, it must get the enough channel conveyances and pumping capacities. It needs set up the detention system to control the flow over the channel capacity. Inspite of this detention system, the peak flow may increased by rainfall distribution and the delay of flow. This shows a design model of detention system which can consider the time problems from mutual connections of the detention storages and pumping flow using IDP(Incremental Dynamic Programming) method.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.2
• /
• pp.21-32
• /
• 1996

The performance of the energy density control algorithm for controlling a broadband noise is evaluated in a one-dimensional enclosure. To avoid noncausality problem of a control filter, which often happens in a frequency domain optimization, analyses presented in this paper are undertaken in the time domain. This approach provides the form of the causally constrained optimal controller. Numerical results are presented to predict the performance of the active noise control system, and indicate that imp개ved global attenuation of the broadband noise can be achieved by minimizing the energy density, rather than the squared pressure. It is shown that minimizing the energy density at a single location yields global attenuation results that are comparable to minimizing the potential energy. Furthermore, unlike the squared pressure control, the energy density control does not demonstrate any dependence on the error sensor location for this one-dimensional field. A practical implementation of the energy-based control algorithm is presented. Results show that the energy density control can be implemented using the two sensor technique with a tolerable margin of performance degradation.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.2
• /
• pp.236-242
• /
• 2008

In this paper, we propose an optimized fuzzy controller based on Hierarchical Fair Competition-based Genetic Algorithms (HFCGA) for rotary inverted pendulum system. We adopt fuzzy controller to control the rotary inverted pendulum and the fuzzy rules of the fuzzy controller are designed based on the design methodology of Linear Quadratic Regulator (LQR) controller. Simple Genetic Algorithms (SGAs) is well known as optimization algorithms supporting search of a global character. There is a long list of successful usages of GAs reported in different application domains. It should be stressed, however, that GAs could still get trapped in a sub-optimal regions of the search space due to premature convergence. Accordingly the parallel genetic algorithm was developed to eliminate an effect of premature convergence. In particular, as one of diverse types of the PGA, HFCGA has emerged as an effective optimization mechanism for dealing with very large search space. We use HFCGA to optimize the parameter of the fuzzy controller. A comparative analysis between the simulation and the practical experiment demonstrates that the proposed HFCGA based fuzzy controller leads to superb performance in comparison with the conventional LQR controller as well as SGAs based fuzzy controller.

• Journal of the Korean Magnetics Society
• /
• v.24 no.4
• /
• pp.107-113
• /
• 2014

In this paper, a optimum degaussing technique, which can minimize an underwater magnetic field anomaly generated by the ferromagnetic hull, was verified through the mock-up test of a ship. To predict degaussing field signals due to the degaussing coils installed in a ship, individual coil effects were measured. Exploiting the linearity of coil effects and analytical sensitivity formula, optimum degaussing current values fed to individual coils were decided. To identify degaussing performance of the proposed method, the obtained degaussing currents were applied to the coils. Then the field anomaly signals were measured and analyzed before and after degaussing. Experimental results show the magnitude of the field signal after degaussing is reduced up to 95% of that before degaussing.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.18 no.3
• /
• pp.191-204
• /
• 1998

One of the key issues in acoustic emission (AE) during hydroproof test of filament-wound composite rocket motor cases is the determination of the optimal component of elastic wave to be monitored. To solve this problem, broadband ultrasonic wave was generated into a symmetrically filament-wound composite motor case, and was received at 105 different locations after the propagation through the composite case with different distances and directions. By analysis of the received signals, characteristics of elastic wave propagation such as frequency components, the maximum propagating distance, and velocity surface were investigated. This analysis was performed for two different conditions of the motor case; air-filled and hydraulically pressurized. Based on these information, the effect of hydraulic pressure on the wave propagation characteristics was investigated and furthermore, the optimal component of elastic wave for AE during hydroproof test of the motor case was successfully determined.