• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.47-54
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• 2005

One of the standard procedures of discontinuity survey is the joint set identification from the population of field orientation data. Discontinuity set identification is fundamental to rock engineering tasks such as rock mass classification, discrete element analysis, key block analysis. and discrete fracture network modeling. Conventionally, manual method using contour plot had been widely used for this task, but this method has some short-comings such as yielding subjective identification results, manual operations, and so on. In this study, the method of discontinuity set identification using genetic algorithm was introduced, but slightly modified to handle the orientation data. Finally, based on the genetic algorithm, we developed a FORTRAN program, Genetic Algorithm based Clustering(GAC) and applied it to two different discontinuity data sets. Genetic Algorithm based Clustering(GAC) was proved to be a fast and efficient method for the discontinuity set identification task. In addition, fitness function based on variance showed more efficient performance in finding the optimal number of clusters when compared with Davis - Bouldin index.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.121-126
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• 2013

Cycloconverter used as a power conversion device in the speed and torque control system of AC machines has the advantage of a simple control and a large torque at low speed. In addition, because a rectifier, a DC link, and an inverter are not installed, this system is simple and suitable for large power system. If a power conversion device, which is currently used as a propulsion motor of large vessel, is changed into cycloconverter, the system is simplified and then the installation costs can be significantly reduced. However, conventional cycloconverter has the increased harmonics because the power loss is large and the waveform of output voltage is distorted, due to the high-speed switching of power semiconductor devices. In order to improve these shortcomings, this paper describes a phase shifting filter which is composed of two inputs with different phases in the primary side and one output in the secondary one. As the voltage waveforms with two different phases are added and transformed into the secondary side, these outputs are close to sinusoidal waves. Thereby the voltage waveforms, which are applied to the propulsion motors, are improved and total harmonic distortions (THDs) are significantly reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.283-288
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• 2014

The use of robots is no longer limited to the field of industrial robots and is now expanding into the fields of service and medical robots. In this light, a trajectory generation method that can respond instantaneously to the external environment is strongly required. Toward this end, this study proposes a method that enables a robot to change its trajectory in real-time using a convolution operation. The proposed method generates a trajectory in real time and satisfies the physical limits of the robot system such as acceleration and velocity limit. Moreover, a new way to improve the previous method (11), which generates inefficient trajectories in some cases owing to the characteristics of the trapezoidal shape of trajectories, is proposed by introducing a triangle shape. The validity and effectiveness of the proposed method is shown through a numerical simulation and a comparison with the previous convolution method.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.20-30
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• 2012

The biggest advantage of AR is that it allows unique experience in the real world through a virtual object. However, there is a limit in the marker techniques to do registration for the virtual object. Therefore, it is possible for a complication that only allows restrictive interaction to come up. This paper provides marker technique of the next generation which can supplement limitations of existing marker technique. Such marker is a combination of IR LED's, and is a convergence of LED VCL concepts of M2M. Environment where the user belongs to and their unique choice will be expressed into one context. Also, the context will be delivered to the system through OOK IR LED marker algorithm. Marker can be operated on the spot to change virtual objects according to the user's taste, registration can be done at the same time for several virtual objects, and control become possible.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.167-176
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• 2009

Traditional cluster-based routing method is a representative method for increasing the energy efficiencies. In these cluster-based routing methods, the selected cluster head collect/aggregate the information and send the aggregated information to the base station. But they have to solve the unnecessary energy dissipation of frequent information exchange between the cluster head and whole member nodes in cluster. In this paper, we minimize the frequency of the information exchange for reducing the unnecessary transmit/receive frequencies as calculate the overlapped area or number of overlapped member nodes between the selected cluster head and previous cluster head in the setup phase. So, we propose the modified cluster selection protocol method that optimizes the energy dissipation in the setup phase and reuses the saved energy in the steady-state phase efficiently that prolongs the whole wireless sensor network lifetime by uniformly selecting the cluster head.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3C
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• pp.201-210
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• 2002

A number or MPLS ATM switching system have been proposed to increase the access speed or current routers, but they cannot satisfy the Internet users who use diverse applications. So they are required to support the so-called differential service, which discriminates service behaviors according to the service class. In this paper, to support this differential service we suggest an LSP control method, which uses the extended LDP message and establishes several different LSPs for each FEC according to the service class. Also, we propose an marking algorithm using the cell loss priority field or ATM cells in order to process the differential service according to application categories. In addition, we present a forwarding procedure based on the LSP control method and the marking algorithm. A forwarding model applied this forwarding procedure can be easily implemented with a minimum modification of existing MPLS ATM switching systems. Therefore, we can save cost and time needed to implement the proposed model. Finally, we estimate the performance behaviors of the proposed application-based forwarding model by the AweSim simulation package.

• Journal of Korean Society of Transportation
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• v.31 no.4
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• pp.58-66
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• 2013

Due to the characteristics of urban freeways such as heavy traffic and high speed, work zone on urban freeways causes the increase of not only the likelihood of crash occurrence but also traffic congestion caused by lane drop, lane change, acceleration/deceleration, and etc. This paper aims to determine the proper length of transition area that satisfies two criteria, mobility and safety, to make the operation of work zone more efficient. For the analysis, three different scenarios were developed by the number of lanes and the proper length of transition area were determined by changing the length from 100m to 500m in 100m increments. The results showed that the proper length of transition area for 3- and 4-lane freeways is 300m, whereas the proper length of 2-lane freeways is 200m. The results indicated that the different length of transition area based on the number of lanes is more desirable and efficient.

• Progress in Medical Physics
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• v.22 no.2
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• pp.85-91
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• 2011

The energy spectra for electron beam of medical linear accelerator were calculated using a GEANT4 Medical Linac 2 example code. The incident electron mean energy were 6, 9, 12, 16, 20 MeV. This code was designed to calculate electron beam energy spectra according to material, thickness and location of electron scattering foil affecting electron beam characteristic. Lead, Copper, Aluminum and Gold were used for scattering foil. The energy distribution for electron and photon were analyzed by changing position of scattering foil in the head of linear accelerator. The effect of electron scattering foil on energy spectra which is basic data of simulation for medical linear accelerator were presented. The calculated results would be used in design of medical accelerator head.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.727-736
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• 2009

In this paper, the $arccos(cos^{-1})$ arithmetic unit for mobile graphics accelerator is designed. The mobile vector graphics applications need tight area, execution time, power dissipation, and accuracy constraints compared to desktop PC applications. The designed processor adopts 2nd-order polynomial approximation scheme based on IEEE floating point data format to satisfy speed and accuracy conditions and reduces area via hardware sharing structure. The arccosine processor consists of 15,280 gates and its estimated operating frequency is about 125Mhz at operating condition of $0.35{\mu}m$ CMOS technology. Because the processor can execute arccosine function within 7 clock cycles, it has about 17 MOPS(million arccos operations per second) execution rate and can be applicable to mobile OpenVG processor. And because of its flexible architecture, it can be applicable to the various transcendental functions such as exponential, trigonometric and logarithmic functions via replacement of ROM and minor hardware modification.

• Journal of the Korean Institute of Intelligent Systems
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• v.5 no.4
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• pp.101-110
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• 1995

In this paper, a DC servo motor position control system based on acceleration control is proposed. The proposed control system consists of an acceleration controller and an auto-tuqing fuzzy PID controller. The auto-tuning fuzzy PID controller provides corrections for an acceleration reference to remove the effect of parametric uncertainties. And it comprises of the expert system which performs the automatic tuning of the PID controller parameters and the conventional PID controller. Expermental results demonstrate strate thi~tth e proposed overall control system has robust properties and good control performances with regard to unmeasurable disturbances and parameter variations. Therefore, the proposed control scheme enhances the applicability of an acceleration control approach and especially performs accurate position control under such an operating environment that model uncertainties exist and/or load, etc. change significantly.