• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.360-374
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• 2016

Since WSNs (Wireless Sensor Networks) applied to their application areas such as smart home, smart factory, environment monitoring, etc., depend on sensor data, the sensor data is the most important among WSN components. The resources of each node consisting of WSN are extremely limited in energy, hardware and so on. Due to these limitation, communication failure probabilities become much higher and the communication failure causes data loss to occur. For this reason, this paper proposes 2MC (Maximum/Minimum Compression) that is a method to compress sensor data by selecting circular queue-based maximum/minimum sensor data values. Our proposed method reduces sensor data losses and value errors when they are recovered. Experimental results of 2MC method show the maximum/minimum 35% reduction efficiency in average sensor data accumulation error rate after the 3 times compression, comparing with CQP (Circular Queue Compression based on Period) after the compressed data recovering.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1285-1293
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• 1992

The fracture behavior of glass/epoxy plain woven composite plates containing circular holes is experimentally investigated to examine the effects of hole size and specimen width on notched tensile strength. It is shown in this paper that the characteristic length according to the point stress criterion depends on the hole size and specimen width. For predicting the notched tensile strength, a modified failure criterion is developed. An excellent agreement is found between the experimental results and the analytical prediction of modified failure criterion. The notched strength and the characteristic length have an increase and decrease relations. When the unstable fracture occured, the critical crack length equivalent for the damage zone size at the edge of hole is about twice the characteristic length. The critical energy release rate G$_{c}$ is independent of hole size(0.03 .leq. 2R/W .leq. 0.5) under the same specimen width. However G$_{c}$ increases with an increase in specimen width which can be explained by stress relaxation due to the notch insensitivity.ity.

• Steel and Composite Structures
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• v.5 no.1
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• pp.17-34
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• 2005

This paper presents an experimental study and its findings of the behavior of circular and square stub columns filled with high strength concrete ($f_c^{\prime}$=49MPa) and polymer cement concrete (PCC) under concentric compressive load. Twenty-four specimens were tested to investigate the effects of variations in the tube shape (circular, square), wall thickness, and concrete type on the axial strength of stub columns. The characteristics of CFT stub columns filled with two types of concrete were investigated in order to collect the basic design data for using the PCC for the CFT columns. The experimental investigations included consideration of the effects of the concrete fill on the failure mode, ultimate strength, initial stiffness and deformation capacity. One of the key findings of this study was that circular section members filled with PCC retain their structural resistance without reduction far beyond the ultimate capacity. The results presented in this paper will provide experimental data to aid in the development of design procedures for the use of advanced concretes in CFT columns. Additionally, these results give structural designers invaluable insight into the realistic behavior of CFT columns.

• Earthquakes and Structures
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• v.27 no.3
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• pp.165-176
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• 2024

In this study, a direct Lagrangian-based three-dimensional computational procedure is developed to evaluate the seismic performance of reinforced concrete liquid-containing circular tanks (RC-LCT). In this approach, fluid-structure interaction (FSI), material nonlinearity, and liquid-structure large deformations are formulated realistically. Liquid is modeled using Mie-Grüneisen equation of state (EOS) in compressible form considering the convective and impulsive motions of fluid. The developed numerical framework is validated based on a previous study. Further, nonlinear analyses are carried out to assess the seismic performance of RC-LCT with various diameter-to-liquid height ratios ranging from 2.5 to 4.0. Based on observations, semi-deep tanks (i.e., D/H_l=2.5) show low collapse ductility due to their shear failure mode while shallow tanks (i.e., D/H_l=4.0) behave in a more ductile manner due to their dominant wall membrane action. Furthermore, the semi-deep tanks provide the least over-strength and ductility due to their catastrophic failure with little energy dissipation. This study shows that LCTs can be categorized as between immediately operational and life safety levels and therefore a drift limiting criterion is necessary to prevent probable damages during earthquakes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.5
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• pp.603-608
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• 2010

In this study, one type of circular shaped composite tube was used, combined with reinforcing foam and without foam. Furthermore, CFRP(Carbon Fiber Reinforced Plastic) circular member manufactured from CFRP prepreg sheet for lightweight design. CFRP is an anisotropic material which is the most widely adapted lightweight structural member. The crashworthy behavior of circular composite material tubes subjected to static axial compression under same conditions is reported in this paper. Test was executed in order to compare the results to the energy absorption and collapse shape. The collapse mode during the failure process were observed and analyzed. The behavior of polymeric foams to the tubes crashworthiness were also investigated. According to the experimental results, specimens filled with foam are higher total energy absorption than the other specimens not filled with the foam.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.350-353
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• 2005

It is a feature of primary importance for a backing material for circular saw blades having teeth which are tipped with cermet, that the steel has not a too high hardenability in order that the backing material shall not be completely hardened through brazing, welding or grinding, etc. in connection with the finishing operation in the manufacturing of circular saw blade. It is believed that V-(2Mo+W) added steel from this point of view had best conditions. Using V-(2Mo+W) added backing steel, the tool failure can be effectively prevented due to superior damping performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.605-610
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• 2002

The purpose of this study is to develop an analytic model which can describe the behavior or concrete compressive member strengthened by CFS(Carbon Fiber Sheet) with various cross-sectional shapes such as circular. square, and octagonal and various laminate angles. The failure criterion of laminated CFS is based on Tsai-Wu failure criterion. The stress strain model of confined concrete compressive member is based on an equation proposed by Mander. The effective lateral confining pressure is considered and modified according to various cross-sectional shapes. Octagonal cross-section shows the best results in the aspect of ductility, while circular does in compressive strengthening effects. In addition, [0/0/0/0] laminate in which the direction of fiber is parallel to the direction of principal stress shows the superior strength and ductility than other laminates. The analytic results show that strength and ductility of the analytic model depend on the cross-sectional shapes as well as the laminate angles.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.783-799
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• 2015

In this study, effect of horizontal in situ stress on failure mechanism around underground openings excavated in isotropic, elastic rock zones is investigated. For estimating the plastic zone occurrence, an induced stress influence area approach (Bray Equations) was modified to define critical stress ratio according to the Mohr-Coulomb failure criterion. Results obtained from modified calculations were compared with results of some other analytical solutions for plastic zone thickness estimation and the numerical modelling (finite difference method software, FLAC2D) study. Plastic zone and its geometry around tunnels were analyzed for different in situ stress conditions. The modified equations gave similar results with those obtained from the other approaches. However, safer results were calculated using the modified equations for high in situ stress conditions and excessive ratio of horizontal to vertical in situ stresses. As the outcome of this study, the modified equations are suggested to use for estimating the plastic zone occurrence and its thickness around the tunnels with circular cross-section.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.250-253
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• 2006

This paper presents experimental studies on investigating the seismic retrofit performance of reinforced concrete circular columns with poor lap-splice details using GFRP wrapping. Four 1/2 scale-down model columns have been tested. The as-built column is expected to suffer brittle failure due to the bond failure of lap-spliced longitudinal reinforcement. The retrofitted columns using GFRP wrapping showed significant improvement of seismic performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.339-342
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• 2003

The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to deterioration of the lap-spliced longitudinal reinforcements without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP wrapping showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by quasi-static experiments.