• Korea Real Estate Review
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• v.24 no.1
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• pp.7-14
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• 2014

This study, as the temporal and spatial data for the real price apartment in Seoul from January 2006 to June 2013, empirically compared and analyzed the estimation result of apartment price using OLS by hedonic price model for the problem of space-time correlation, temporal autoregressive model (TAR) considering temporal effect, spatial autoregressive model (SAR) spatial effect and spatiotemporal autoregressive model (STAR) spatiotemporal effect. As a result, the adjusted R-square of STAR model was increased by 10% compared that of OLS model while the root mean squares error (RMSE) was decreased by 18%. Considering temporal and spatial effect, it is observed that the estimation of apartment price is more correct than the existing model. As the result of analyzing STAR model, the apartment price is affected as follows; area for apartment(-), years of apartment(-), dummy of low-rise(-), individual heating (-), city gas(-), dummy of reconstruction(+), stairs(+), size of complex(+). The results of other analysis method were the same. When estimating the price of real estate using STAR model, the government officials can improve policy efficiency and make reasonable investment based on the objective information by grasping trend of real estate market accurately.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.407-416
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• 2011

This study expressed the reservoir's storage-discharge relation as a non-linear reservoir model and theoretically quantified the reservoir storage effect. Among those non-linear functions like exponential function, logarithmic function and power function considered, the exponential function of the storage-discharge relation was found to be the most valid. The non-linear reservoir model proposed was applied to the Chungju Dam and the Soyang River Dam, whose storage effects during flood were estimated to be about 23 hours and 43 hours, respectively. This result indicates that the Choongju Dam, even though its size and total storage volume are similar to those of the Soyang River Dam, does not achieve enough storage effect as its basin size and the inflow amount are much larger.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.3
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• pp.1-9
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• 1999

Effect of furnish on enzyme activity was investigated by using the three components (cellulose, enzyme, and cationic polyelectrolyte) model papermaking system. Avicel was used as a cellulose model compound to observe the effect of adsorption and desorption of enzyme with other component and the resultant change of particle size. As an experimental result, the enzyme loses considerably its apparent activity due to the adsorption onto cellulose and cationic polyelectrolyte. Activities of enzyme applied to the actual papermaking stocks having controlled fiber length showed different behavior in terms of pulp species UKP and KOCC stocks. That is, the enzyme activity in UKP was increased as fines content increased, however, vice versa in KOCC stock . This result can be considered to be the existence of various contaminants included in the fines of KOCC . The effect of possible contaminants such as inorganic materials, calcium ion, surfactant, and conductivity on enzyme activity were also investigated.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.121-130
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• 2000

Currently, in evaluating a flexural strength of a concrete member, the effect of specimen depth has not been systematically studied, even though its effect on ultimate strength of a section is very important. For all types of loading conditions, the trend is that the strength of a member tends to decrease when the member depth increases. In this study, the influence of specimen depth on flexural compressive strength of concrete member was examined experimentally. A series of C-shaped specimens subjected to axial compressive force and bending moment were tested using three geometrically similar specimens with different length-to depth ratios (h/c = 1, 2 and 4) which have compressive strength of 55 MPa. The results indicate that the flexural compressive strength decreased as the specimen depth increased. A model equation was derived based on regression analyses of the experimental data. Also, the results show that ultimate strain decreases as the specimen depth increases. Finally, a general model equation for the depth effect is proposed.

• Korean Journal of Childcare and Education
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• v.15 no.4
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• pp.115-134
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• 2019

Objective: This study was aimed to analyze the effects of activities using picture books for young children's language development and to identify factors that caused differences in these effects by applying meta-analysis. Methods: We conducted a homogeneity test of effect sizes on 21 Korean studies published in academic journals from 1990 to February 2018 and calculated the effect size by applying a random effect model. Additionally, we conducted a meta-ANOVA to investigate whether the effect sizes differed by types of language development, picture book activities, and environmental variables-such as place, time, and agent. Results: The results indicated that the effect sizes of the 21 studies were heterogeneous and the total effect size was 0.90, which was significantly large according to Cohen's standard. The effect sizes also varied by types of language development, picture book activities, and environmental variables. Conclusion/Implications: To increase the effects of activities using picture books for young children's language development, this study suggested the importance of picture book activities to be integrated with other play areas, teaching methods, and other print materials for the development of literacy abilities, and the link between home and early childhood education institutions.

• Spatial Information Research
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• v.22 no.2
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• pp.53-62
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• 2014

The floor field model is the micro pedestrian model based on a cellular automata for modeling pedestrian movement in the interior space using the static and dynamic floor field. It regards a form of pedestrian as square but the actual pedestrian's shape and size are similar to ellipsoid or rectangle. Because of this, we are difficult to give a rotation effect to pedestrians and there is a limit to reflect an impact of clogging and jamming. Also, this model is not able to reflect an impact of a posture and visibility effectively in the pedestrian movement. In this study, we suggest the improved pedestrian model incorporating the actual shape and size of pedestrian. The pedestrian's shape is defined not square but rectangle which is close to the actual body size of Korean. Also, we define the model which is able to represent the impact of clogging and jamming between pedestrians by adding the pedestrian's posture. We develop the simulator for testing the suggested model and study the difference between two models by comparing a number of effects. As a result, we could confirm solving the problem with dynamic value in the existed model and reflecting the panic effect in evacuation situation.

• Information Systems Review
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• v.19 no.1
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• pp.123-145
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• 2017

This study empirically examines the effects of regulation on online gaming. Going beyond ad hoc heuristic approaches on individual behavior, we investigate the effects of regulation on dynamic changes of games or service providers. In particular, we propose three theoretical perspectives: social influence to investigate the regulation effect, the role of prior experience to determine the difference in the regulation effect size through users' prior experience, and network externalities to discover the difference in the regulation effect size according to the number of users on an online gaming platform. We use the vector autoregression methodology to model patterns of the co-movement of online games and to forecast game usage. We find that online gamers are heterogeneous. Therefore, policy makers should make suitable regulations for each heterogeneous group to effectively avoid generating gaming addicts without interrupting the economic growth of the online gaming industry.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.343-348
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• 2009

In this study, an efficient sequential bridging method to characterize both the particle size effect and concentration effect on the mechanical properties of nanocomposites at high volume fraction is suggested through a molecular dynamics(MD) simulations and micromechanics of composites materials. The Young's modulus and the shear modulus of the nanocomposites at various particle radius and at 12% volume fraction were obtained from MD simulations and multi-inclusion model was adopted to describe both modulus in continuum model. In order to describe the particle size effect, an additional phase, effective interface, was adopted as characteristic phase and the non-dilute concentration effect which appears at 12% volume fraction was describe via the variation of the elastic modulus of the infinite medium. Both the elastic modulus of the interface and infinite medium were fitted into functions of particle radius for the applicability of the present bridging method at various particle radii. Using the present bridging method the elastic modulus of the nanocomposites was efficiently obtained with accuracy. In addition, the effect of the interface thickness and modulus on the elastic modulus of the nanocomposite was investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1463-1470
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• 2010

Microforming, which exploits the advantages of metal forming technology, appears very promising in manufacturing microparts since it enables the production of parts using various materials at a high production rate, it has high material utilization efficiency, and it facilitates the production of parts with excellent mechanical properties. However, the conventional macroscale forming process cannot be simply scaled down to the micro-scale process on the basis of the extensive results and know-how on the macroscale process. This is because a so-called "size effect" occurs as the part size decreases to the microscale. In this paper, we attempt to develop an effective analytical and experimental modeling technique for explaining the effects of the grain size and the specimen size on the behavior of metals in microscale deformation processes. Copper sheet specimens of different thicknesses were prepared and heat-treated to obtain various grain sizes for the experiments. Tensile tests were conducted to investigate the influence of specimen thickness and grain size on the flow stress of the material. In addition, an analytical model was developed on the basis of phenomenological experimental findings to quantify the effects of the grain size and the specimen size on the flow stress of the material in microscale and macroscale forming.

• Korean Journal of Optics and Photonics
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• v.24 no.1
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• pp.29-38
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• 2013

In this paper, the illumination performances of three freeform lenses optimally designed for a point source were investigated for several LEDs with different source sizes, and also the tolerance characteristics of the lenses were analyzed. For comparison, two lenses with different sizes were designed with a divergent illumination model, and the last one was done with an overlapped illumination model. As the LED source size increased, the illuminance uniformity decreased more strongly, and the influence of a source misalignment on illumination performance became insignificant. However, the variation of LED radiation characteristics had strong effect on the illumination performance, irrespective of LED source size. Even though the lens based on a divergent illumination model showed superior performance compared to the lens based on an overlapped illumination model, the latter was less sensitive to the variation of LED radiation characteristics.