• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.377-390
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• 2019

A method for estimating the floor response spectra (FRS) of elastic structures under earthquake excitations is proposed. The method is established based on a previously proposed direct estimation method for single degree of freedom systems, which generally overestimates the FRS of a structure, particularly in the resonance period range. A modification factor is introduced to modify the original method; the modification factor is expressed as a function of the period ratio and is determined through regression analysis on time history analysis results. Both real and artificial ground motions are considered in the analysis, and it is found that the modification factors obtained from the real and artificial ground motions are significantly different. This suggests that the effect of ground motion should be considered in the estimation of FRS. The modified FRS estimation method is further applied to a 10-story building structure, and it is verified that the proposed method can lead to a good estimation of FRS of multi-story buildings.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.5
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• pp.269-277
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• 1999

In this paper, a novel dead time minimization algorithm is proposed for improving the output waveform of an inverter. The adverse effects of the dead time are mainly described by the voltage drop and the distortion factor of waveforms. The principle of the proposed algorithm is organized with forbidding unnecessary firings fo the inverter switches which are not conducted even though the gate signal is impressed. The proposed methods are explained with the conduction mode of output currents. The H/W and S/W implementation method of the proposed algorithm are also presented. The validity of the proposed algorithm is verified by comparing the simulation and experimental results with conventional methods. It can be concluded from the results that the proposed algorithm has the advantage which is able to reduce the harmonics in the output voltages and which the output voltage can nearly be equal to the reference value. Another advantage of the proposed method is the reduction of total numbers of switching so that the switching losses of inverter drives can be minimized.

• Journal of The Korean Society of Grassland and Forage Science
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• v.9 no.2
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• pp.88-95
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• 1989

This experiment 'was conducted to investigate the grazing cattle's palatability by the method of grazing time on the pasture dominated orchardgrass and on the pasture dominated perennial ryegrass from June to October, 1987. The experiment was carried out on the experimental field at Livestock Ex- Experiment Station. The results are summarized as follows: 1. In summer, the grazing time on the pasture dominated orchardgrass increased in 49.7 min, 57.4 min, 102 min, 118.7 min, respectively as sward height decreased in 50 cm, 45 cm, 35 cm, 23 cm, respectively and their correlation coefficiet was -0.9722*(P <0.05). 2. In autumn, the grazing time on the pasture dominated perennial ryegrass decreased in 182 min, 98.5 min, 49.4 min, 31.9 min, respectively as sward height decreased in 43 cm, 34 cm, 25 cm, 18 cm, respectively and their correlation coefficient was 0.9684*. (P <0.05). 3. Grazing time increased as sward height increased on the pasture dominated perennial ryegrass because the composition rate of orchardgrass and red clover which were palatability on the plot of the high sward height.was many. It was suggested that the factor that could be first related to palatability on mixture pasture was the factor of species than the factor of sward height. 4. When the eating rate on the plot of the low sward height was over 55% as the grazing day went by, it gradually decreased because the eating rate on it was high but the fresh yield was low. After all it seemed that it affected palatability because forage availability on the plot of the low sward height was degenerating.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.77-89
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• 2023

This study aims to establish the correlations between variables related to a slope during rainfall and factor of safety (FOS) and displacement using a coupling analysis method that is designed to consider both in rainfall conditions. With the recent development of measurement technologies, the approach of using the measurement data in the field has become easier. Particularly, they have been obtained in tests to determine the real-time safety and movement of a slope; however, a specific method has not been finalized. In addition, collected measurement data for recognizing the FOS and displacement in real-time with a specific relevance is difficult, and risks of uncertainty, such as in soil parameters and time, exist. In this study, the correlations between various slope-related variables (i.e., rainfall intensity, rainfall duration, angle of the slope, and mechanical properties including strength parameters of selected three types of soil; loamy sand, silt loam, sand) and the FOS and displacement are analyzed in order of seepage analysis, slope stability analysis and slope displacement analysis. Moreover, the methodology of coupling analysis is verified and a fundamental understanding of the factors that need to be considered in real-time observations is gained. The results show that the contributions of the abovementioned variables vary according to the soil type. Thus, the tendency of the displacement also differs by the soil type and variables but not same tendency with FOS. The friction angle and cohesion are negative while the rainfall duration and rainfall intensity are positive with the displacement. This suggests that understanding their correlations is necessary to determine the safety of a slope in real-time using displacement data. Additionally, databases considering rainfall conditions and a wide range of soil characteristics, including hydraulic and mechanical parameters, should be accumulated.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.412-418
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• 1994

Efficient algorithm for the solidification simulation by FDM is described from the practical point of views. If a proper time step ${\Delta}t$ is selected, the calculation is accelerated by implicit algorithm with the temperature recovery method of latent heat method. The implicit routine in the calculation is processed by SOR method(relaxation factor＝1.5, truncation error＝$10^{-4}$). The calculation is more accelerated by linear-interpolated explicite algorithm with a time step larger than the minimum value of the time step. This explicit method, which is applicable to the practical casting simulation problems, produces almost same results with about 40% faster calculation speed compared with the conventional explicit method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.161-168
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• 2002

To evaluate seismic performance of bridges, two procedures far capacity spectrum method are presented. The capacity spectrum procedures include the reduction factor-ductility-period relationship in order to construct the inelastic demand spectra from the elastic demand spectra. Application of the procedures is illustrated by example analysis. Maximum displacements estimated by the procedures are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the maximum displacements estimated by the procedures are, on overall, smaller than those by the inelastic time history analysis

• The Korean Journal of Ecology
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• v.4 no.1_2
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• pp.38-51
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• 1981

The present investigation was estimated the effect of temperature, precipitatiion, and time on the decomposition of litters with litter bags of Pinus densiffora and Quercus mongolica at Gure where elevation in 50m, and at Nogodan where elevation in 1300m on Mt. Jiri. As the above results, decomposition model was proposed to relation of the environmental conditions. And was investigated the production and decomposition of litters from the stands of various forest communities in Kwangneung, Mt. Jiri and Mt. Halla. The results are as follows; The models for the decay of organic carbon (C) was as follows: $C=Coe^{-Kt}$ (limiting factor;time) $C=Coe^{-K'te}$ (limiting factor;tempedrature) $C=Coe^{-KnP}$ (limiting factor:precipitation) As observed in litter bag method, the decomposition rate of litter in Pinus densiflora was slower than that of Quercus mongolica. The higher elevation, the slower decomposition rate. The decomposition of litters at Gure where elevation in 50m was equally influenced by temperature and precipitation. But at Nogodan where elevation in 1300m was much inflenced by precipitation. The decay constant of litters was larger in hardwood forest than in coniferous forest. In the same species, the more elevatiion, the less decomposition constant. The time required for the decay of 50%, 95^, 99% of the accumulated litters in the forest floor were faster in hardwood forest than in coniferous forest. In the same species, the higher elevatiion, the longer time required.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.1
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• pp.165-171
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• 2014

We develop an optimization algorithm for a periodic review inventory system under a stochastic budget constraint. While most conventional studies on the periodic review inventory system consider a simple budget limit in terms of the inventory investment being less than a fixed budget, this study adopts more realistic assumption in that purchasing costs are paid at the time an order is arrived. Therefore, probability is employed to express the budget constraint. That is, the probability of total inventory investment to be less than budget must be greater than a certain value assuming that purchasing costs are paid at the time an order is arrived. We express the budget constraint in terms of the Lagrange multiplier and suggest a numerical method to obtain optional values of the cycle time and the safety factor to the system. We also perform the sensitivity analysis in order to investigate the dependence of important quantities on the budget constraint. We find that, as the amount of budget increases, the cycle time and the average inventory level increase, whereas the Lagrange multiplier decreases. In addition, as budget increases, the safety factor increases and reaches to a certain level. In particular, we derive the condition for the maximum safety factor.

• Current Optics and Photonics
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• v.4 no.4
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• pp.310-316
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• 2020

We propose and experimentally demonstrate an all-optical radio frequency (RF) spectrum broadening system based on time compression. By utilizing the procedure of dispersion compensation values, the frequency domain is broadened by compressing the linear chirp optical pulse which has been multiplexed by the radio frequency. A detailed mathematical description elucidates that the time compression is a very preferred scheme for spectrum broadening. We also report experimental results to prove this method, magnification factor at 2.7, 8 and 11 have been tested with different dispersion values of fiber, the experimental results agree well with the theoretical results. The proposed system is flexible and the magnification factor is determined by the dispersion values, the proposed scheme is a linear system. In addition, the influence of key parameters, for instance optical bandwidth and the sideband suppression ratio (SSR), are discussed. Magnification factor 11 of the proposed system is demonstrated.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.357-360
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• 1991

In this paper, we have introduced a network and showed how this can be realised as an adaptive equalizer. The walsh equlizer is built from a set of Walsh-Block pulse functions and LMS algorithms with the optimal convergence factor(C.F.). The convergence and the adaptation speed of this algorithms depends on the proper choice of a design factor $\mu$ called the C.F.. Conventional adaptation techniques use the fixed time constant C.F. by the method of trial and error. In this paper, we propose to adaptive C.F. which are optimally tailored to adapt C.F. in real time so that their values are kept optimum for a new set of input variables.