• International Journal of Highway Engineering
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• v.15 no.5
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• pp.21-29
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• 2013

PURPOSES: Simulation of aggregate slump test using equivalent sphere particle in DEM and its validity evaluation against lab aggregate slump test METHODS : In this research, aggregate slump tests are performed and compared with DEM simulation. To utilize spheric particles in YADE, equivalent sphere diameter concept is applied. As verification measures, the volume in slump cone filled with aggregate is used and it is compared with volume in slump cone filled with equivalent sphere particle. Slump height and diameter are also used to evaluate the suggested numerical method with equivalent concept RESULTS : Simulation test results show good agrement with lab test results in terms of loose packing volume, height and diameter of slumped particle clump. CONCLUSIONS : It is concluded that numerical simulation using DEM is applicable to evaluate the effect of aggregate morphological property in loose packing and optimum gradation determination based on the aggregate slump test simulation result.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.473-480
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• 2020

In this paper, we proposed a high frequency equivalent circuit considering parasitic impedance components for differential noise analysis on the input stage during DC-DC buck converter switching operation. Based on the proposed equivalent circuit model, we presented a method to measure parasitic impedance parameters included in DC bus plate, IGBT, and PCB track using the gain phase method of a network analyzer. In order to verify the validity of this model, a DC-DC prototype consisting of a buck converter, a signal analyzer, and a LISN device, and then resonance frequency was measured in the frequency range between 150 kHz and 30 MHz. The validity of the parasitic impedance measurement method and the proposed equivalent model is verified by deriving that the measured resonance frequency and the resonance frequency of the proposed high frequency equivalent model are the same.

• Journal of Korea Water Resources Association
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• v.44 no.4
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• pp.327-338
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• 2011

This study examined the quantification problem of a storm shape using the concept of equivalent ellipses. The equivalent ellipses of a storm event were estimated at every time step with respect to the several thresholds of rainfall intensity, which was also examined in terms of their size and number. In addition, the average equivalent ellipse was decided, and the confidence intervals of major axis, minor axis, and rotational angle were calculated to evaluate if the average equivalent ellipse could be the representative one. As results, the following results could be derived. First of all, the number of equivalent ellipses and the size of equivalent ellipses increase as the threshold increase. Secondly, the appropriate ratio of major and minor axises of equivalent ellipse is 2 : 1. Finally, the average rotational angle estimated with respect to several threshold rainfall intensities were all found not to be statistically different from that of all representative rotational angles.

• Journal of Radiation Protection and Research
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• v.40 no.3
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• pp.147-154
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• 2015

The scatter photons and photoneutrons from high energy photon beams (more than 10 MV) will increase the undesired dose to the patient and the staff working in linear accelerator room. This undesired dose which is found at out-of-field area can increase the probability of secondary malignancy. The purpose of this study is to determine the equivalent dose of scatter photons and neutrons generated by 3 different treatment techniques: 3D-conformal, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The measurement was performed using two types of the optically stimulation luminescence detectors (OSL and OSLN) in the Alderson Rando phantom that was irradiated by 3 different treatment techniques following the actual prostate cancer treatment plans. The scatter photon and neutron equivalent dose were compared among the 3 treatments techniques at the surface in the out-of-field area and the critical organs. Maximum equivalent dose of scatter photons and neutrons was found when using the IMRT technique. The scatter neutrons showed average equivalent doses of 0.26, 0.63 and $0.31mSv{\cdot}Gy^{-1}$ at abdominal surface region which was 20 cm from isocenter for 3D, IMRT and VMAT, respectively. The scattered photons equivalent doses were 6.94, 10.17 and $6.56mSv{\cdot}Gy^{-1}$ for 3D, IMRT and VMAT, respectively. For the 5 organ dose measurements, the scattered neutron and photon equivalent doses in out of field from the IMRT plan were highest. The result revealed that the scatter equivalent doses for neutron and photon were higher for IMRT. So the suitable treatment techniques should be selected to benefit the patient and the treatment room staff.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.47-53
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• 2021

The fatality rate is used to estimate each country's risk level. However, the fatality rate is calculated using the number of fatal accidents and workers, which is collected differently across countries. It is therefore problematic to use these numbers in an equivalent way. This study proposes a new approach for calculating the number of full-time equivalent workers when evaluating individual countries' fatality rate by suggesting an equivalent condition for the calculation of the number of full-time equivalent workers. This study proceeds in three steps: (i) analysis of the fatality rate among various countries; (ii) fatality rate calculation using the full-time equivalent workers; and (iii) comparison of the fatality rate among various countries. The study found that for the fatality rate based on national data, the fatality rate in South Korea (1.72‱) is 10 times higher than that in United Kingdom (0.17‱). However, according to the number of full-time equivalent workers, the fatality rate in South Korea (1.86‱) was three times higher than that in the United Kingdom (0.56‱). These findings reveal a difference in the fatality rate depending on the method used to calculate the number of full-time equivalent workers. Therefore, the number of full-time equivalent workers must be calculated for each country to accurately compare the fatality rate. Ultimately, the study's results highlight the need for clearer standards in the assessment of the fatality rate by country in international organizations such as the ILO.

• Structural Engineering and Mechanics
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• v.77 no.1
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• pp.137-149
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• 2021

In engineering design, the axial equivalent elastic modulus of laminated FRP pipe was mostly calculated by the average elastic modulus method or the classical laminated plate theory method, which are based on relatively simplified assumptions, and may be not accurate enough sometimes. A new analytical calculation method for the axial equivalent elastic modulus of laminated FRP pipe was established based on three-dimensional stress state. By comparing the results calculated by this method with those by the above two traditional analytical methods and the finite element method, it is found that this method for the axial equivalent elastic modulus fits well not only for thin-walled pipes with orthotropic layers, but also for thick-walled pipes with arbitrary layers. Besides, the influence of the layer stacking on the axial equivalent elastic modulus was studied with this method. It is found that a proper content of circumferential layer is beneficial for improving the axial equivalent elastic modulus of the laminated FRP pipe with oblique layers, and then can reduce its material quantity under the premise that its axial stiffness remains unchanged. Finally, the meso-mechanical mechanism of this effect was analyzed. The improving effect of circumferential layer on the axial equivalent elastic modulus of the laminated FRP pipe with oblique layers is mainly because that, the circumferential fibers can restrain the rigid body rotations of the oblique fibers, which tend to cause the significant deformations of the pipe wall units and the relatively low axial equivalent elastic modulus of the pipe.

• Steel and Composite Structures
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• v.18 no.4
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• pp.947-970
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• 2015

An equivalent friction element is proposed to simulate the friction in cable-strut joints. Equivalent stiffness matrixes and load vectors of the friction element are derived and are unified into patterns for FEM by defining a virtual node specially to store internal forces. Three approaches are described to verify the rationality of the new equivalent friction element: applying the new element in a cable-roller model, and numerical solutions match well with experimental results; applying the element in a continuous sliding cable model, and theoretical values, numerical and experimental results are compared; and the last is applying it in truss string structures, whose results indicate that there would be a great error if the cable of cable supported structures is simulated with discontinuous cable model which is usually adopted in traditional finite element analysis, and that the prestress loss resulted from the friction in cable-strut joints would have adverse effect on the mechanical performance of cable supported structures.

• Fire Science and Engineering
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• v.26 no.5
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• pp.1-7
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• 2012

We have studied on equivalent length tables which are used to calculate the friction loss of pipe fittings and valves of water-based fire systems in Korea. Three kinds of equivalent length tables are mainly used and unfortunately, the most extensively used table is not ascertained the reliable source. When the three tables are compared, each table has different equivalent length up to 2.4 times in same item. We should use unified equivalent length table which is scientifically reasonable in order to act up to globalization as performing lots of over-sea projects. Therefore, we propose the reasonable equivalent length tables.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.459-464
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• 2007

Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally, response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.571-575
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• 2010

Mutation testing is known as a very useful technique for measuring the effectiveness of a test data set and finding weak points of the test set. An equivalent mutant degrades the effectiveness of mutation testing. Elimination of equivalent mutants is a very important problem in mutation testing.In this paper, we proposed kinds of methods for detecting class-level equivalent mutants. These methods judge the equivalency of mutants through structural informations and behavioral information of the original program and mutants using static analysis. We found that our approach can detect not a few of equivalent mutants and expected that the cost of mutation testing can be saved considerably.