• KCI Concrete Journal
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• 제12권1호
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• pp.23-34
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• 2000

Experiments were carried out to investigate the seismic behaviors, such as lateral strength, ductility and energy-dissipation capacity. of high-strength concrete (HSC) square short column confined in thin steel shell. The primary objective of the study was to investigate the suitability of using HSC square columns confined in thin steel shell in region of moderate-to-high seismic risk. A total of six columns, consisting of two ordinarily reinforced concrete square short columns and four reinforced concrete square short columns confined in thin steel shell was tested. Column specimens, short columns in a moment resisting frame with girder. were tested under a constant axial and reversed cyclic lateral loads. To design the specimens. transverse reinforcing methods, level of axial load applied, and the steel tube width-thickness ratio (D/t) were chosen as main parameters. Test results were also discussed and compared in the light of improvements in general behaviors, ductility, and energy-absorption capacities. Compared to conventionally reinforced concrete columns, the HSC columns confined in thin steel shell had similar load-displacement hysteretic behavior but exhibited greater energy-dissipation characteristics . It is concluded that, in strong earthquake areas, the transverse reinforcing method by using a thin steel shell (D/t=125) is quite effective to make HSC short columns with very strong and ductile.

• Steel and Composite Structures
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• 제17권4호
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• pp.497-516
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• 2014

The ultimate carrying capacity of axially loaded welded square box section members made of medium and high strength steels (nominal yield stresses varying from 345 MPa to 460 MPa), with large width-to-thickness ratios ranging from 35 to 70, is analyzed by finite element method (FEM). At the same time, the numerical results are compared with the predicted results using Direct Strength Method (DSM), modified DSM and Effective Yield Strength Method (EYSM). It shows that curve a, rather than curve b recommended in Code for design of steel structures GB50017-2003, should be used to check the local-overall interaction buckling strength of welded square section columns fabricated from medium and high strength steels when using DSM, modified DSM and EYSM. Despite all this, EYSM is conservative. Compared to EYSM and modified DSM, DSM provides a better prediction of the ultimate capacities of welded square box compression members with large width-thickness ratios over a wide range of width-thickness ratios, slenderness ratios and steel grades. However, for high strength steels (nominal yield strength greater than 460 MPa), the numerical and existent experimental results indicate that DSM overestimates the load-carrying capacities of the columns with width-thickness ratio smaller than 45 and slenderness ratio less than 80. Further, for the purpose of making it suitable for a wider scope, DSM has been modified (called proposed modified DSM). The proposed modified DSM is in excellent agreement with the numerical and existing experimental results.

• Journal of information and communication convergence engineering
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• 제14권4호
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• pp.222-226
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• 2016

A design method for a compact square loop antenna fed by a microstrip (MS) line for indoor digital television (DTV) applications is proposed. The proposed antenna consists of a square loop, circular sectors, and an MS line. The square loop combined with circular sectors is printed on one side of a substrate, and a $75-{\Omega}$ MS line is printed on the other side. The circular sectors are used as a wideband balun or transition to connect the MS line and the square loop. A prototype of the proposed square loop antenna operating in the DTV band (470-806 MHz) is designed and fabricated on an FR4 substrate. Experimental results show that the proposed antenna has the desired impedance characteristics in the frequency band of 464-1,220 MHz (89.8%) for a voltage standing wave ratio (VSWR) of <2 covering the DTV band, and a broadside gain of 0.8-3.3 dBi in the DTV band.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2000년도 종합학술발표회 논문집 Vol.10 No.1
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• pp.319-323
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• 2000

A method for miniaturization of microstrip patch antenna without degrading its radiation characteristics is investigated. The ring geometry introduces additional parameters to the antenna that can be used to control its resonance frequency and bandwidth. For a single square ring increasing the size of patch decreases the resonance frequency and bandwidth. To match the antenna to a transmission line and also enhance its bandwidth. the square ring patch is stacked by a square ring patch. The computed results are compared with experiment and good agreement is obtained.

• East Asian mathematical journal
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• 제29권5호
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• pp.511-519
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• 2013

There are various methods for evaluating a matrix square root, which is a solvent of the quadratic matrix equation $X^2-A=0$. We consider new iterative methods for solving matrix square roots of M-matrices. Particulary we show that the relaxed binomial iteration is more efficient than Newton-Schulz iteration in some cases. And we construct a formula to find relaxation coefficients through statistical experiments.

• Journal of the Korean Data and Information Science Society
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• 제20권3호
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• pp.587-592
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• 2009

The most frequent use of the chi-square distribution is in the area of goodness-of-t of a distribution. The likelihood ratio test is a commonly used test statistic as the maximum likelihood estimate in statistical inferences. The recently revised versions of the likelihood ratio test statistics are used in estimating the parameter in the chi-square distribution. The estimates are compared with the commonly used method of moments and the maximum likelihood estimate.

• 한국환경복원기술학회지
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• 제10권6호
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• pp.130-138
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• 2007

To protect the surface of ground-cutting slopes occurring at the national road substitute detour [roundabout road]construction jobsite between Munduk and Wubokgu within the jurisdiction of Pohang-si and environment-friendly road construction, a test execution of re-vegetation measures on the major slopes was done and the results are as follows : As a result of finding out the number of sprouting individuals on the test construction site, the average number of sprouting individuals on the three test spots by the method of revegetation measures D, revegetation measures A, and revegetation measures B was 1,292 number of per square meter, 1,190 number of per square meter, and 1,095 number of per square meter respectively, which statistics were higher than those of test spot by the revegetation measures C. As a result of finding out living plant's breeding index [weight in dried state], the average dried weight of living plant at the test spot by the method of revegetation measures B, in case of foreign herbal species, was the highest marking 8.96 grams per square meter, and the next was 6.86grams per square meter by the method of revegetation measures D, and the next after was 6.80 grams per square meter by the method of revegetation measures A, and the last 5.93 grams per square meter by the method of revegetation measures C. As a result of finding out the covering degree on the slopes, the same average covering degree of 80% and 77.5% in revegetation measures A and revegetation measures D individually, which showed a somewhat higher covering degree than those of revegetation measures B and revegetation measures C. As a result of finding out appearing plants on the test construction site, seeding plant life was found to be sprouting on all test spot while native and foreign herbal species and herbaceous plant as well as shrubs were growing in good harmony with each other. However, in case of revegetation measures B and revegetation measures C method, foreign plant species are dominantly growing. As a result of inspecting rifts on the slopes and the excavated state by water, there existed cracks in some of base materials only in revegetation measures C method applied spot.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1232-1240
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• 2002

Recently, linear motors are applied to many small precision products. Thus high generating power with small size is required of it. In order to increase the motor efficiency, the design variables need to be optimized. In this study, Vector Fields FEM software, OPERA-3d, was used for simulating linear motor. The thrust and magnetic flux density at the air-gap center were simulated and compared with the experimental results. Taguchi method was applied to investigate the effects of each variables. As a result, the thickness of conductor and magnet was important for the thrust but the thickness of the yoke. The temperature of the conductor was determined by finding the thermal conductivity that was determined by experimentation. Correlation equation relating to the thrust and temperature was proposed by Latin square and Least Square method. The optimum design variables were determined by correlation equation, and compared with simulation results. According to this analysis, thrust force of linear motor was improved about 7% comparing with conventional model.

• 한국소음진동공학회논문집
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• 제24권12호
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• pp.962-968
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• 2014

The lattice Boltzmann method(LBM) has attracted attention as an alternative numerical algorithm for solving fluid mechanics since the end of the 90's. In these days, its intrinsic unsteadiness and rapid increase in computing power make the LBM be more applicable for computing flow-induced noise as well as fluid dynamics. The lattice Boltzmann method is a weakly compressible scheme, so we can get information about both aerodynamics and aeroacoustics from single simulation. In this paper, numerical analysis on Aeolian tone noise generated by tandem-twin square cylinders in duct is performed using the LBM. For simplicity, laminar two-dimensional fluid models are used. To verify the validity and accuracy of the current numerical techniques, numerical results for the laminar duct and the cylinder flows are compared with the analytical solution and the measurement, respectively. Then, aerodynamic noise of the twin tandem square cylinders is investigated. It is shown that the aerodynamic noise from the twin tandem square cylinders can be reduced by controlling the distance between the cylinders.

• Journal of Electrical Engineering and Technology
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• 제4권2호
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• pp.272-276
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• 2009

In this paper, the arc region of a gas circuit breaker (GCB) is analyzed using the fast moving least square reproducing kernel method (FMLSRKM) which can simultaneously calculate an approximated solution and its derivatives. For this problem, an axisymmetric and inhomogeneous formulation of the FMLSRKM is used and applied. The field distribution obtained by the FMLSRKM is compared to that of the finite element method. Then, a whole breaking period of a GCB is simulated, including analysis of the arc gas flow by finite volume fluid in the cell, and the electric field of the arc region using the FMLSRKM.