• Wind and Structures
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• v.24 no.2
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• pp.119-144
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• 2017

The traditional method for the simulation of high Reynolds number (Re) effects on wind loads on cooling tower models in wind tunnels focuses only on the mean wind pressure distribution. Based on observed effects of some key factors on static/dynamic flow characteristics around cooling towers, the study reported in this paper describes a comprehensive simulation method using both mean and fluctuating wind pressure distributions at high Re as simulation targets, which is indispensable for obtaining the complete full-scale wind effects in wind tunnels. After being presented in this paper using a case study, the proposed method is examined by comparing the full covariance matrices and the cross-spectral densities of the simulated cases with those of the full-scale case. Besides, the cooling tower's dynamic structural responses obtained using the simulated wind pressure fields are compared with those obtained by using the full-scale one. Through these works, the applicability and superiority of the proposed method is validated.

• Korean Journal of Child Studies
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• v.35 no.4
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• pp.223-247
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• 2014

This study aimed to verify the positive effects of forest activities for children from economically underprivileged households in local children's centers and the effect of such activities on the protective factors of their development. One hundred and eighty five children participated in the Forest Activities Program, which conducted over a total 8 sessions. Pre-post tests of the subjective well-being scale, DAS, multiple life satisfaction scale, ego-resilience scale were conducted and the children then made picture stories during the program itself. The results of the analysis of differences between pre-post tests were as follows: first, the negative emotions of participating children decreased significantly. Second, the school-satisfaction and self-satisfaction levels of the participating children increased. Third the participating children's positive perceptions of self and interpersonal relationships also increased through the forest activities. Finally, there were differences of the change types of picture stories that children created while they were participating in the program; and these divergences were related to the effectiveness of the program. These forest activities had positive effects upon the economically disadvantaged children who participated in this study. However, in order to increase the effects of such forest activities qualitatively, greater support for the active involvement of children is required.

• Human Ecology Research
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• v.51 no.6
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• pp.583-590
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• 2013

The purpose of this study was to examine the effects of parental abuse and neglect, as well as that of children's peer attachment, on mobile phone dependency. Data were obtained from the Korean Child-Youth Panel Survey (KCYPS), and the participants were 1,892 (909 boys, 983 girls) elementary students (5th graders) who had a mobile phone. To measure the variables, this study used such scales as the parental abuse and neglect scale, peer attachment scale, and mobile phone dependency scale. The data were analyzed using descriptive statistics, Pearson's correlation, and structural equation modeling analysis. The results of the study were as follows: First, parental abuse and neglect had direct negative effects on children's peer attachment; that is, the more parental abuse and neglect, the less children's peer attachment. Second, parental abuse and neglect had direct positive effects on mobile phone dependency; that is, the more parental abuse and neglect, the greater children's mobile phone dependency. However, children's peer attachment did not directly affect mobile phone dependency; that is, children's peer attachment did not have a mediating effect between parental abuse and neglect, and mobile phone dependency. In conclusion, parental abuse and neglect influence children's peer attachment and mobile phone dependency. Thus this study showed that parental abuse and neglect, rather than children's peer attachment, affect children's mobile phone dependency.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.75.2-75.2
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• 2012

Turbulence is ubiquitous in astrophysical fluids such as the interstellar medium and intracluster medium. To maintain turbulent motion, energy must be injected into the fluids. In turbulence studies, it is customary to assume that the fluid is driven on a scale, but there can be many different driving mechanisms that act on different scales in astrophysical fluids. We expect different statistical properties of turbulence between turbulence with single driving scale and turbulence with double driving scales. In this work, we perform 3-dimensional incompressible MHD turbulence simulations with energy injection in two ranges, 2${\surd}$12 (large scale) and 15

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.83-87
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• 2003

Experimental blast studies were carried out in a limestone quarry to study the effects of blasting on structures. To have an in-depth understanding of the possible relation between parameters like vibrations, frequency and scale distance and ten trial blast were conducted. 29 monitoring stations were located in such a pattern to give a true representation of blast induced vibrations for the entire mining in this area. The vibrations were monitored in the vicinity of structures surrounding the quarry in the direction towards the village, road, railway line, office building, etc. Scale distances were determined to identify the maximum charge permissible to cause damage to structures.

• Journal of Powder Materials
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• v.8 no.3
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• pp.192-196
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• 2001

Ag doped Hydroxyapatite powder in nano-scale was successfully synthesized either by co-precipitation or by ion exchange route. The fabricated powder was successfully dispersed through freeze drying due to the prevention of secondary particles. The antimicrobial effects of nano-HAp against E.coli was superior to micron ones not only in its strength but also in duration.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.867-873
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• 2004

It has been known that debonding failures between CFS(Carbon Fiber Sheet) and concrete in the strengthened RC beams are initiated by the peeling of the sheets in the region of combined large moment and shear forces, being accompanied by the large shear deformation after flexural cracks. These shear deformation effects are seldom occurred in small-scale model tests, but debondings due to the large shear deformation effects are often observed in a full-scale model tests. The premature debonding failure of CFS, therefore, must be avoided to confirm the design strength of full-scale RC beam in strengthening designs. The reinforcing details, so- called 'U-Shape fiber wrap at mid-span' which wrapped the RC flexural members around the webs and tension face at critical section with CFS additionally, were proposed in this study to prevent the debonding of CFS. Other reinforcing detail, so called 'U-Shape fiber wrap at beam end' were included in this tests and comparisons were made between them.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.24-31
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• 2012

Effects of the subgrid length-scale in the Delayed-Detached Eddy Simulation(DDES) are investigated based on the Spalart-Allmaras(S-A) and the k-$\omega$ Shear Stress Transport(SST) turbulence models. Driver & Seegmiller's experimental results are used to validate numerical results. Grid convergence with grid resolution and subgrid length-scale is investigated. The simulation results show that the volume method for the subgrid length-scale is more resistant to unfavorable effects of the grid size in the periodic direction than the maximum method. Using a sufficient grid resolution and an appropriate subgrid length-scale, both S-A based DDES and SST based DDES methods can provide a good correlation with the experimental data.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.445-452
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• 2018

In this paper the effects of particle size and model scale of concrete have been investigated on point load index, tensile strength, and the failure processes using a PFC2D numerical modeling study. Circular and semi-circular specimens of concrete were numerically modeled using the same particle size, 0.27 mm, but with different model diameters of 75 mm, 54 mm, 25 mm, and 12.5 mm. In addition, circular and semi-circular models with the diameter of 27 mm and particle sizes of 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, and 1.27 mm were simulated to determine whether they can match the experimental observations from point load and Brazilian tests. The numerical modeling results show that the failure patterns are influenced by the model scale and particle size, as expected. Both Is(50) and Brazilian tensile strength values increased as the model diameter and particle sizes increased. The ratio of Brazilian tensile strength to Is(50) showed a reduction as the particle size increased but did not change with the increase in the model scale.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.316-325
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• 1998

The objective of this study is to investigate the role of large-scale coherent structures in a spatially developing plane mixing layers. To achieve this, we have to look into the mutual interactions between three-dimensional large-scale coherent structures and the mean flow. Our attention will be focused on the energy exchange mechanism between the various modes, and the effects of the nonlinear evolution of the phases of the interacting modes. Linear stability of the three-dimensional viscous shear layer is formulated and solved as the basis for the solution of the nonlinear formulation based on the energy method. The importance of the initial conditions that may affect the evolution of the flow has been examined. It has been numerically calculated the nonlinear effects arising from the interactions among the three-dimensional large-scale coherent structures in a spatially developing plane mixing layers. The results of this study provide useful parametric information for the control of shear layer in practical applications in the mixing and transport augmentation.