• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.1
• /
• pp.8-17
• /
• 2006

It is essential for robot to have the sensing and communication abilities in the swarm robot system. In general, as the number of robot goes on increasing, the limitation of communication capacity and information overflow occur in global communication system. Therefore a local communication is more effective than global one. In this paper, we analyze information propagation mechanism based on local communication. To find an optimal communication radius, we propose several methods with different conditions. Also, to avoid chaotic behavior which occurs when a robot obtains and loses information, we will suggest the stable condition of information propagation.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.7
• /
• pp.774-781
• /
• 2014

This paper presents a fingerprint database construction method for WLAN RSSI (Received Signal Strength Indicator)-based indoor positioning. When RSSI is used for indoor positioning, the fingerprint method can achieve more accurate positioning than trilateration and centroid methods. However, a FD (Fingerprint Database) must be constructed before positioning. This step is a very laborious process. To reduce the drawbacks of the fingerprint method, a radio propagation model-based FD construction method is presented. In this method, an FD can be constructed by a simulator. Experimental results show that the constructed FD-based positioning has a 3.17m (CEP) error. In this paper, a spatial correlation method is presented to estimate the NLOS(Non-Line of Sight) error included in the FD constructed by a simulator. As a result, the NLOS error of the FD is reduced and the performance of the error compensated FD-based positioning is improved. The experimental results show that the enhanced FD-based positioning has a 2.58m (CEP) error that is a reasonable performance for indoor LBS (Location Based Service).

• Steel and Composite Structures
• /
• v.27 no.3
• /
• pp.255-271
• /
• 2018

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 2000.09a
• /
• pp.229-234
• /
• 2000

The propagation of blast vibration and the damping characteristics depend on both the mechanical properties of rock mass and weight charge. In this study, the characteristics of propagation and damping were analyzed by FLAC. The construction site was the second Kwang-ju circulating read. Taguchi method which is one of experimental design methods was used for determination of input data and parameter levels. The results showed that rock density was the most dominant of variables being concerned in this study, which affect the propagation of blast vibration.

• Tunnel and Underground Space
• /
• v.10 no.3
• /
• pp.475-480
• /
• 2000

The propagation of blast vibration and the damping characteristics depend on both the mechanical properties of rock mass and weight charge. In this study, the characteristics of propagation and damping were analyzed by FLAC. The construction site was the second Kwang-ju circulating road. Taguchi method which is one of experimental design methods was used for determination of input data and parameter levels. The results showed that rock density was the most dominant of variables being concerned in this study, which affect the propagation of blast vibration.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.6
• /
• pp.67-75
• /
• 1999

The sensing and communication abilities of a mobile robot are essential to cooperative behavior in distributed autonomous robotic systems. In general, as the number of robot goes on increasing, the limitation of communication capacity and information overflow occur in global communication capacity and information overflow occur in global communication system. Therefore a local communication is more effective than global one. In this paper, we analyze information propagation mechanism based on local communication. To find an optimal communication radius, we propose three methods with different conditions. Also, to avoid chaotic behavior which occurs when a robot obtains and loses information, we find stable condition of information propagation.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.2
• /
• pp.168-176
• /
• 2015

Due to the reduction in device feature size, transient faults (soft errors) in logic circuits induced by radiations increase dramatically. Many researches have been done in modeling and analyzing the susceptibility of sequential circuit elements caused by soft errors. However, to the best knowledge of the authors, there is no work which has well considerated the feedback characteristics and the multiple clock cycles of sequential circuits. In this paper, we present a new method for evaluating the susceptibility of sequential circuit elements to soft errors. The proposed method uses four Error Propagation Probability Matrixs (EPPMs) to represent the error propagation probability of logic gates and flip-flops in current clock cycle. Based on the predefined matrix union operations, the susceptibility of circuit elements in multiple clock cycles can be evaluated. Experimental results on ISCAS'89 benchmark circuits show that our method is more accurate and efficient than previous methods.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.1
• /
• pp.26-32
• /
• 2008

The safe operation of high pressure pipe line systems is of significant importance. Leaks due to faulty operation from the pipelines can lead to considerable product losses and to exposure of community to dangerous gases. There are several leak detection methods of pipeline network which have recently been suggested. The negative pressure wave detection technology, which has advantages of short time detection availability, accurate leaking location estimate capability and cost effective, is concentrated in this study. Theoretical analysis of the flow characteristics for leaking through a hole on the pipe wall has been performed by using Fluent 6.3, commercial CFD package. The results of 3-dimensional analysis near leaking hole confirm the occurrence of negative pressure wave, and the results of 2-dimensional analysis verify the characteristics of propagation of the wave which travels with speed equal to the speed of sound in the pipeline contents. Characteristics of leakage and pressure in a pipe with a hole have been analyzed for the various pipe and hole sizes.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.3
• /
• pp.61-69
• /
• 1997

A simple and relatively new experimental method is proposed to estimate the plane stress fracture toughness by using compact tension (CT) specimen. The anti-buckling plates (fabricated to prevent the buckling caused by the 45 plastic yielding around crack tip under the plane stress condition) help to determine the relatively accurate plane stress fracture toughness of two stainless steels (SS304 and SS316). The fatigue crack propagation behavior of two stainless steels under two different loading conditions such as 10Hz and 5Hz frequency fatigue loadings was investigated by using image analysis technique (IAT) which renders several technical advantages over various conventional measuring methods. It was found that the IAT could be used to estimate fatigue crack lengths more effectively. Furthermore, it was suggested that we might control the measuring time interval for fatigue crack propagation by nearly automatically controlled technical process with the help of IAT.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.209-214
• /
• 2007

In Korean geology that crystalline rock is dominant, the properties of subsurface including the anisotropy are distributed complexly and changed abruptly. Because of such geological environments, cross-hole seismic traveltime tomography is widely used to obtain the high resolution image of the subsurface for the engineering purposes in the geotechnical sites. However, because the cross-hole tomography has a wide propagation angle coverage relatively, its data tend to include the seismic velocity anisotropy comparing with the surface seismic methods. It can cause the misinterpretation that the cross-hole seismic data including the anisotropic effects are analyzed and treated with the general processing techniques assuming the isotropy. Therefore, we need to consider the seismic anisotropy in cross-hole seismic traveltime tomography. The seismic anisotropic tomography algorithm, which is developed for evaluation of the velocity anisotropy, includes several inversion schemes in order to make the inversion process stable and robust. First of all, the set of the inversion parameters is limited to one slowness, two ratios of slowness and one direction of the anisotropy symmetric axis. The ranges of the inversion parameters are localized by the pseudo-beta transform to obtain the reasonable inversion results and the inversion constraints are controlled efficiently by ACB(Active Constraint Balancing) method. Especially, the inversion using the Fresnel volume is applied to the anisotropic tomography and it can make the anisotropic tomography more stable than ray tomography as it widens the propagation angle coverage.