• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.43-54
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• 1992

For shallow arches with large dynamic loading, linear analysis is no longer considered as practical and accurate. In this study, a method is presented for the dynamic analysis of shallow arches in which geometric nonlinearity must be considered. A program is developed for the analysis of the nonlinear dynamic behavior and for evaluation of critical buckling loads of shallow arches. Geometric nonlinearity is modeled using Lagrangian description of the motion. The finite element analysis procedure is used to solve the dynamic equation of motion and Newmark method is adopted in the approximation of time integration. A shallow arch subject to radial step loads is analyzed. The results are compared with those from other researches to verify the developed program. The behavior of arches is analyzed using the non-dimensional time, load, and shape parameters. It is shown that geometric nonlinearity should be considered in the analysis of shallow arches and probability of buckling failure is getting higher as arches are getting shallower. It is confirmed that arches with the same shape parameter have the same deflection ratio at the same time parameter when arches are loaded with the same parametric load. In addition, it is proved that buckling of arches with the same shape parameter occurs at the same load parameter. Circular arches, which are under a single or uniform normal load, are analyzed for comparison. A parabolic arch with radial step load is also analyzed. It is verified that the developed program is applicable for those problems.

• The Journal of the Korea Contents Association
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• v.11 no.2
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• pp.238-250
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• 2011

In 2006, the number of days of the screen quota (theatrical movie screening days of Korean produced films in a year required by the law) was reduced to 73 days from 146 days per year. Three years after the reduction of screen quota, this paper studies the impact of reduction of screen quota system on Korean produced films. Using Non-parametric statistics, Gini Index and Regression analysis, this study shows that the average number of Korean moviegoer of Korean films which was released last three years(2007-2009) after the cutback of screen quota in 2006 is reduced to 640,109.9123 from 1,107,217.82 for three years(2003-2005) before the cutback. And this is significant in statistics. while Hollywood film gets 76,168,518 more audiences than the total number of audience for 2003-2005, the total numbers of Korean films is cut to 218,917,590 (2007-2009) from 245,802,356 (2003-2005). Gini Index of 2009(0.84) indicates that the inequality of a distribution of box office performance of Korean films is getting worse after the cutback. For now, the reduction of screen quota has negative effects for Korean films. Only the technological advance, education of relates personnel, redesigning of the related infrastructure, market-driven movies, creative production, and the promotion of the independent films can reduced the negative effects.

• Journal of Distribution Science
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• v.13 no.5
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• pp.71-82
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• 2015

Purpose - The purpose of this study is to investigate risk price implied from the pricing kernel of Korean stock distribution market. Recently, it is considered that the quantitative easing programs of major developed countries are contributing to a reduction in global uncertainty caused by the 2007~2009 financial crisis. If true, the risk premium as compensation for global systemic risk or economic uncertainty should show a decrease. We examine whether the risk price in the Korean stock distribution market has declined in recent years, and attempt to provide practical implications for investors to manage their portfolios more efficiently, as well as academic implications. Research design, data and methodology - To estimate the risk price, we adopt a non-parametric method; the minimum norm pricing kernel method under the LOP (Law of One Price) constraint. For the estimation, we use 17 industry sorted portfolios provided by the KRX (Korea Exchange). Additionally, the monthly returns of the 17 industry sorted portfolios, from July 2000 to June 2014, are utilized as data samples. We set 120 months (10 years) as the estimation window, and estimate the risk prices from July 2010 to June 2014 by month. Moreover, we analyze correlation between any of the two industry portfolios within the 17 industry portfolios to suggest further economic implications of the risk price we estimate. Results - According to our results, the risk price in the Korean stock distribution market shows a decline over the period of July 2010 to June 2014 with statistical significance. During the period of the declining risk price, the average correlation level between any of the two industry portfolios also shows a decrease, whereas the standard deviation of the average correlation shows an increase. The results imply that the amount of systematic risk in the Korea stock distribution market has decreased, whereas the amount of industry-specific risk has increased. It is one of the well known empirical results that correlation and uncertainty are positively correlated, therefore, the declining correlation may be the result of decreased global economic uncertainty. Meanwhile, less asset correlation enables investors to build portfolios with less systematic risk, therefore the investors require lower risk premiums for the efficient portfolio, resulting in the declining risk price. Conclusions - Our results may provide evidence of reduction in global systemic risk or economic uncertainty in the Korean stock distribution market. However, to defend the argument, further analysis should be done. For instance, the change of global uncertainty could be measured with funding costs in the global money market; subsequently, the relation between global uncertainty and the price of risk might be directly observable. In addition, as time goes by, observations of the risk price could be extended, enabling us to confirm the relation between the global uncertainty and the effect of quantitative easing. These topics are beyond our scope here, therefore we reserve them for future research.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.2
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• pp.114-120
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• 2011

The characteristics of a helical turbine to be used for tidal stream energy conversion have been numerically studied with varying a few design parameters. The helical turbines were proposed aiming at mitgating the well known poor cut-in characteristics and the structural vibration caused by the fluctuating torque, and the basic concept is introducing some twisting angle of the vertical blade along the rotation axis of the turbine. Among many potential controling parameters, we focused, in this paper, on the twisting angle and the height to diameter ratio of the turbine, and, based on the numerical experiment, We tried to propose a configuration of such turbine for which better performance can be expected. The three-dimensional unsteady RANS equations were solved by using the commercial CFD software, FLUENT with k-${\omega}$ SST turbulence model, and the grid was generated by GAMBIT. It is shown that there are a range of the twisting angle producing better efficiency with less vibration and the minimum height to diameter ratio above which the efficiency does not improve considerably.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.579-589
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• 2003

Most beam-to-column connections are symmetrically reinforced because of the reverse action caused by earthquakes. However, in weak-earthquake regions like Korea, asymmetrically reinforced connections could be used. In particular, the connections between concrete-filled tube (CFT) column and H-shape beam could be applied using a simplified lower diaphragm. The tensile capacity or Combined Cross Diaphragm for upper reinforcing was tested using a simple tension test. Four types for lower reinforcing combined Cross, none, horizontal T-bar, and vertical plate were tested using the ANSI/AISC SSPEC 2002 loading program. Horizontal T-bar and stud bolts in vertical flat, bar transmit tensile stress from the beam's bottom flange to filled concrete. All test specimens satisfied 0.01 radian inelastic rotational requirement in ordinary moment frame of AISC seismic provision. According to the results of the parametric studies simplified lower diaphragms demonstrated outstanding strength, stiffness, and plastic deformation capacity which could lead to more sufficient seismic performance in the field.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.157-160
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• 2008

The generation of high-purity hydrogen from hydrocarbon fuels is essential for efficient operation of fuel cell. In general, most feasible strategies to generate hydrogen from hydrocarbon fuels consist of a reforming step to generate a mixture of $H_2$, CO, $CO_2$ and $H_2O$ (steam) followed by water gas shift (WGS) and CO clean-up steps. The WGS reaction that shifts CO to $CO_2$ and simultaneously produces another mole of $H_2$ was carried out in a two-stage catalytic conversion process involving a high temperature shift (HTS) and a low temperature shift (LTS). In a typical operation, gas emerges from the reformer is taken through a high temperature shift catalyst to reduce the CO concentration to about 3~5%. The HTS reactor was designed and tested in this study to produce hydrogen-rich gas with CO to a range of 2~4%. The iron based catalysts (G-3C) was used for the HTS to convert the most of CO in the effluent from the partial oxidation (POX) to $H_2$ and $CO_2$ at a relatively high rate. Parametric screening studies were carried out for variations of the following variables: reaction temperature, steam flow rate, components ratio ($H_2/CO$), and reforming gas flow rate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.40-48
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• 2017

RC flat plates may be governed by a serviceability as well as a strength condition, and a construction sequence and its impact on the distributions of gravity loads among slabs tied by shores are decisive factors influencing short and long term behaviors of flat plate. Over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction, and a reshoring work may be helpful in reducing slab deflections by controlling the vertical distributions of loads in a multi-shored flat plate system. In this study, a effect of reshoring works on short and long term deflections of flat plate systems are analyzed. The slab construction loads with various reshoring schemes and slab design and construction conditions are defined by a simplified method, and the practical calculation of slab deflections with considering construction sequences and concrete cracking and long term effects is applied. From parametric studies, the reshoring works are verified to reduce slab deflections, and the optimized conditions for the reshoring works and slab design and constructions are discussed.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.107-117
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• 2004

This paper is to investigate the reinforcing effects of newly devised Tire-cell mat made of waste tires in sand. Parametric study on number of connection bolts between Tirecells, relative density of sand, embedded depth, number of reinforced layers and width of Tirecell mat was made by using plate loading tests. It is found that the number of connection bolt was enough to maintain the given pressure. The bearing capacity ratio(BCR), which is defined as the rate of ultimate bearing capacity of reinforced soil to that of unreinforced soil, is the highest at the lowest density. And the reinforcing effect can be obtained in case of embedded depth within 1.0B, where B is loading width. Also settlement reduction is the highest at the lowest density of sand. The effect of number of Tirecell reinforced layers with 0.4B to 0.5B interval is limited to 2 layers and further reinforcing effects can not be obtained beyond 3 layers. Especially, the bearing capacity increased remarkably at 1 layer of reinforcement and the degree of increase was small from 1 layer to 2 layers of reinforcement. The effect of mat width of Tirecell was not significant because of high stiffness of Tirecell although the maximum bearing capacity was shown at the 2.0B mat width and the reinforcing effects of Tirecell, in general, was prominent compared with those of commercial Geoweb.

• Journal of Radiation Protection and Research
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• v.23 no.3
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• pp.149-157
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• 1998

An analysis has been performed to estimate the additional number of workers and the additional collective dose in man-cSv which would be required, nuclear industry-wide as a result of reducing individual dose limit. This analysis can be extended to the reduction in the dose limits recommended by ICRP Publ.60 and BEIR V report as well as the proposed dose limits by regulatory authorities. An industry-wide database was employed in the analysis based on a summary of industry-wide occupational radiation exposure compiled by the Korea Radioisotope Association. Correlation model was employed to compute the affects of setting specific annual individual dose limits. In this study, we have addressed worker non-productivity while in the radiation environment on a parametric or 'sensitivity analysis' basis. This alleviates the need for developing such data underlying a summation of many individual tasks at many nuclear facilities. It has the advantage that very low non-productivity assumptions can readily be defended as conservative, in that it is difficult to approach such low worker non-productivity factors even in the best of environments in any industry. On a per facility basis, for calendar year 1997, the number of workers required would be increased from 231 workers to 269 workers and collective man-cSv dose would be also increased by approximately fourteen percent if the individual dose limit was reduced to 2 cSv/y and an individual worker non-productivity fraction of 0.1 is assumed.

• Korean Journal of Construction Engineering and Management
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• v.14 no.5
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• pp.35-43
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• 2013

Nowadays the widely used media in architecture include visualizations, animations and three-dimensional models. 3D digital methods using active CAM(Computer Aided Manufacturing) and CNC(Computerized Numerical Control) imaging have been developed for accurate shape and 3D measurements in freeform buildings. In contrast to a conventional building using auto CAD system and others, the proposed digital optimization method is based on a combination of 3D numerical data and parametric 3D model for design and construction. The objective of this paper is therefore to present digital optimization process for constructability of freeform building. The method can be useful in the effective implementation of an error-proofing process of freeform building during design and construction phase. 3D digital coordinate data can be used effectively to identify correct size of structural and finish members and installation location of each members in construction field. In addition, architects, engineers and contractors can evaluate design, materials, constructability and identify error-proofing opportunities. Other project participants can also include representatives from all levels of management, departments as well as workers and key subcontractors' personnel, if necessary. The 3D digital optimization process is therefore appropriate to serious variations in freeform shape. For future study, the developed digital optimization method is necessary to be carried out to verify the robustness and accuracy for constructability in construction field.