• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.556-558
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• 1995

This paper presents a new simplified method for finding the multiple load flow solutions and through their solutions the voltage stability can be evaluated. Line flow($P_{ij}$, $Q_{ij}$) may be formulated with the second-order equations for $V_{i}^{2}$ in polar coordinates or two circle equations for $e_{i}$ and $f_{i}$ in rectangular coordinates. Based on this feature, multiple load flow solutions are calculated with simple works, results of multiple load flow solutions are used for sensitivity analysis of voltage stability. Also, in the case that reactive power sources is considered, method of evaluating the voltage stability is introduced. The proposed method was validated to 2-bus and IEEE 6-bus system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.27-30
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• 2009

This study is to evaluate the basic properties of concrete panels for surface finishing and to introduce the case of its application. As a result, the records of bending, abrasion resistance, impact strength were shown satisfied with KS standard. In a case of its application it was found production process can be simplified through a simplified manufacturing process. And also its cost-effective production and utilization practices are highly expected than imitation stone or native rock.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.60-69
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• 2003

The simplified two-color method is proposed which can estimate the temperature distribution and the soot density of the whole flame with the image analysis of the high-speed photographs. The factors influenced on its processing were examined, for example, the selection of the wave length, the kind of films, the preparation of the calibration curve between the radiance of flame and the luminance temperature. The simplified two-color method reported in this paper can be used as a tool for the improvement of the combustion process in direct injection diesel engine.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.337-344
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• 2006

This paper is concerned with the simplified criterion given in ASCE 4-98, for determining whether soil-structure interaction (SSI) analysis is required for seismic response analysis of nuclear power plant structures. In this study, the criterion is evaluated for a couple of example structures including an existing nuclear power plant and the Hualien large-scale seismic test building. Forced vibration analysis and seismic response analysis are carried out using the simple stick model with soil springs and an elaborated SSI analytical model. From the numerical analyses, it is found that the criterion may not allow the fixed-base analysis for bedrock with shear wave velocity of greater than 1,100m/s which is a well-known criterion for a rock site. In addition, it is indicated that peak amplification as well as the peak broadening specified in NRC RG 1.122. shall be considered to include the effects of SSI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.794-801
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• 2000

In this paper, the efficient new performance evaluation method for digital communication channels is suggested and verified its efficiency in terms of simulation run-tim for the digital satellite broadcasting satellite TV channel. In order to solve the difficulties of the existing Importance Sampling(IS) Technics, we adopted the discrete probability mass function(PMF) in the new method for estimating the statistical characteristics of received signals from the measured Nth order central moments. From the discrete probability mass function obtained with less number of the received signal than the one required in the IS technic, continuous cumulative probability function and its inverse function are exactly estimated by using interpolation and extrapolation technic. And the overall channel is simplified with encoding block, inner channel performance degra-dation modeing block which is modeled with the Uniform Random Number Generator (URNG) and concatenated Inverse Cummulative Pr bility Distribution function, and decoding block. With the simplified channel model, the overall performance evaluation can be done within a drastically reduced time. The simulation results applied to the nonlinear digital satellite broadcasting TV channel showed the great efficiency of the alogrithm in the sense of computer run time, and demonstrated that the existing problems of IS for the nonlinear satellite channels with coding and M-dimensional memory can be completely solved.

• KIEAE Journal
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• v.13 no.5
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• pp.79-88
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• 2013

This study creates the evaluation criteria to analyze the $CO_2$ emission quantity in the complex of apartment house among domestic buildings and proposes how to calculate the $CO_2$ emission quantity by the only simple information of apartment house. The study shows that in order to create the index of carbon emission evaluation criteria, $CO_2$ emission quantity for its input materials in these 27 apartment houses are 445,412g-$CO_2/m^2$ for apartment building, 474,322g-$CO_2/m^2$ for the basement parking lot, 483,523g-$CO_2/m^2$ for welfare facility, 729,957g-$CO_2/m^2$ for sales facility, 743,560g-$CO_2/m^2$ for other facility, 26,782g-$CO_2/m^2$ for public facility, 43,659g-$CO_2/m^2$ for landscape, 1,113g-$CO_2/m^2$ for indoor facility, 11,251g-$CO_2/m^2$ for outdoor facility and 891g-$CO_2/m^2$ for common temporary based on the average $CO_2$ emission by facility. We can also see the analysis data that in case of using the selected factors only, the rate of error is 7.51% comparing with the emission quantity by using simplified LCA method this study suggests for the whole range of apartment houses and the rate of error is average 3.24% using selective and main materials. And this it is evaluated that we can get the result which is similar to the actual $CO_2$ emission quantity with only the simple information about the apartment house.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.47-56
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• 2017

Aseismic designs of pile-supported wharves are commonly performed utilizing simplified dynamic analyses, such as multi-mode spectral analyses. Simplified analyses can be useful for evaluating the limit state of structures. However, several pile-supported wharves, that have been damaged during past earthquakes, have shown that soil deformation and soil-pile dynamic interaction significantly affect the entire behavior of structures. Such behavior can be captured by performing nonlinear effective stress analyses, which can properly consider the dynamic interactions among the soil-pile-structure. The present study attempts to investigate the earthquake performance of a pile-supported wharf utilizing a three-dimensional numerical method. The damaged pile-supported wharf at the Kobe Port during the Hyogo-ken Nambu earthquake (1995) is selected to verify the applicability of the numerical modeling. Analysis results showed a suitable agreement with the observations on the damaged wharf, and the significant effect of excess pore pressure development and pile-soil dynamic interaction on the seismic performance of the wharf.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.29-43
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• 2022

Various underground facilities are being constructed to improve the urban environment. Therefore, it is more necessary than ever to reasonably evaluate the seismic response of underground utility tunnels, playing a significant part in urban infrastructure. In this study, the major features and differences of two types of existing pseudo-static analysis methods are reviewed. Each method uses a simplified 2D frame model to represent the seismic behavior of underground structures. Applying each method to a one-barrel rectangular utility tunnel in Korea, the suitability in predicting seismic responses, especially the racking deformation of the tunnel, is examined. In addition, several precautions and suggestions are provided in this study against the inattentive application of the methods to seismic evaluation of underground structures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.221-243
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• 2023

The use of roadheaders has been increasing to mitigate the problems of noise and vibration during tunneling operations in urban area. Since lack of experience of roadheader for hard rock, the selection of appropriate machines and the evaluation of cutting rates have been challenging. Currently, empirical models developed overseas are commonly used to evaluate cutting rates, but their effectiveness has not been verified for domestic rocks. In this paper, a comprehensive literature review was conducted to assess the rock cutting force, cutterhead capacity, and cutting rate to select the appropriate machine and evaluate its performance. The cutterhead capacity was reviewed based on the literature results for the site. Furthermore, a new empirical model and simplified method for predicting cutting rates were proposed through data analysis in relation to operation time and rock strength, and compared with those of the conventional model from the manufacturer. The results show good agreement for high strength range upper 80 MPa of uniaxial compressive strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.49-55
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• 2017

In the seventies, a number of researchers carried out experiments on pullout tests with prototype equipment, and the pullout test was certified as a reliable nondestructive testing(NDT) method for determining the strength of concrete. To estimate the strength of high-strength concrete, we propose a simplified pullout test that uses as a break-off bolt a standard 10mm bolt with a groove on the shaft, an insert nut, and a pullout instrument that includes a hydraulic oil pump without a load cell. To verify the advantages of the simplified pullout test(low cost, simplicity, and convenience), four wall specimens were tested with two levels of concrete strength, 30 MPa and 50 MPa, using a simplified pullout tester with a load cell. The pullout load and concrete compressive strength were measured every day until day 7, day 14, day 21 and day 28. It was found that the pullout load was very similar to the compressive strength. Therefore, we have verified that a simplified pullout test can be used to evaluate the in-place strength of high-strength concrete in structures. The prediction equation of the groove diameter of the break-off bolt(y) with the concrete strength(x) was derived as y=0.05x+3.79, with a coefficient of determination of 0.88 found through regression analysis.