• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.285-293
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• 2016

This study conducted the evaluations of stable channel and physical disturbance improvement for optimal construction of river structures by focusing on Wonju River. A stable slope was analyzed sectionally for stable channel design, and in order to satisfy the stable slope, river structure improvement scenarios were deduced. Accordingly, through physical disturbance improvement evaluation for each scenario, the study extracted the optimal scenario for stable channel design and physical disturbance improvements. The changes in physical habitat were analyzed when river structure improvements were made for stable channel design and physical disturbance improvement. Zacco koreanus, an indicator fish of the soundness of the aquatic ecosystem, was selected as a restoration target species by investigating the community characteristics of fish fauna and river environments in the Wonju River. The habitat suitability was investigated by the PHABSIM model with the habitat suitability index of Zacco koreanus. The results of the prediction evaluation showed a slight decrease in habitat suitability and weighted usable area. However, it was not influenced by the improvements in the river structure. The study suggested river structure arrangement methods that can improve physical soundness and safety of Wonju River, and confirmed that there were no effects to the changes in the physical habitat.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.815-827
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• 2014

The current study was undertaken to verify appropriateness of muscle endurance test at three different angles ($30^{\circ}C$, $40^{\circ}C$, $50^{\circ}C$) of isometric contraction position, and to sought valid and reliable testing method that provide an alternative to sit-ups. Total 92 young and healthy subjects (68 males and 24 females) were recruited, and the following results were obtained. 1. A low correlations in males, but a high correlations in females was found when the comparisons were made between aerobic and muscle endurance capability. 2. Measuring tolerance time, by using isometric contraction was showed a significant correlation with the repetition numbers of sit-ups. 3. The highest correlation was found at 40 inclined degrees of plane, and the lowest correlation was drawn from 50 inclined degrees of plane. Based on these results, it was concluded that measuring tolerance time during maintaining an isometric contraction at 40 inclined degrees of plane is a valid and effective tool for measuring abdominal muscle endurance, and it can be used as an alternative way of sit-up, which potentially risky for inducing many back-associated injuries. Further studies need to be undertaken to determine for optimal angles, that can safely be applied for people of various age groups and physical conditions.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.3
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• pp.195-202
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• 2007

The normalized difference in incident solar energy between a target surface and a level surface (overheating index, OHI) is useful in eliminating estimation error of site-specific maximum temperature in complex terrain. Due to the complexity in its calculation, however, an empirical proxy variable called northern exposure index (NEI) which combines slope and aspect has been used to estimate OHI based on empirical relationships between the two. An experiment with real-world landscape and temperature data was carried out to evaluate performance of the NEI - derived OHI (N-OHI) in reduction of spatial interpolation error for daily maximum temperature compared with that by the original OHI. We collected daily maximum temperature data from 7 sites in a mountainous watershed with a $149 km^2$ area and a 795m elevation range ($651{\sim}1,445m$) in Pyongchang, Kangwon province. Northern exposure index was calculated for the entire 166,050 grid cells constituting the watershed based on a 30-m digital elevation model. Daily OHI was calculated for the same watershed ana regressed to the variation of NEI. The regression equations were used to estimate N-OHI for 15th of each month. Deviations in daily maximum temperature at 7 sites from those measured at the nearby synoptic station were calculated from June 2006 to February 2007 and regressed to the N-OHI. The same procedure was repeated with the original OHI values. The ratio sum of square errors contributable by the N-OHI were 0.46 (winter), 0.24 (fall), and 0.01 (summer), while those by the original OHI were 0.52, 0.37 and 0.15, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.49-56
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• 2002

In this study, the InGaP epilayers were grown on the exact and the $2^{\circ}$, $6^{\circ}$, $10^{\circ}$ of cut GaAs substrates by metal-organic vapor phase epitaxy, and the effects of interfacial elastic strains determined by the substrate offcut angle upon the resulting dislocation density of epilayer were investigated for the first time. The elastic strains were obtained from lattice mismatch and lattice misfit by TXRD, and the dislocation densities from epilayer x-ray FWHM. For the offcut angle range used in this study, the elastic strain was maximum and x-ray FWHM minimum at offcut angle $6^{\circ}$. From 11K PL measurements, PL wavelength was found to decrease with an increase of offcut angle. PL intensity was maximum at offcut angle $6^{\circ}$. TEM results showed that the electron diffraction pattern was of typical zincblende structure, and that the dislocation density was minimum for substrate offcut angle $6^{\circ}$. The results obtained in this study, along with the device fabrication process and beam characteristics, clearly demonstrated that the optimum substrate offcut angle for the InGaP/GaAs heterostructures is $6^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.145-153
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• 1984

In the present work, a computer simulation is performed employing Hottel-Whillier-Bliss model for thermal performance of solar collectors. The major collector parameters examined in the computer simulation are: number of transparent glass covers(N), thermal emissivity of the absorbing plate surface (.epsilon.$_{P}$), absorptivity of absorber plate (.alpha.$_{p}$), flow rate per unit area of collector (G), $L_{b}$ / $k_{b}$ of insulation material, tilt angle of collector (S), and solar insolation(I). By varying numerical values of the major collector parameters around their typical values, the corresponding variations in thermal efficiency curves are examined. In addition, an experimental investigation has been carried out with a slightly modified KAIST collector test loop under a real sun condition in order to compare with the simulation results, examine the applicability of the mathematical model of the collector thermal performance, and study the effect of variation of flow rate (G) on thermal efficiency and the range of optimum flow rate.e.

• Composites Research
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• v.23 no.2
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• pp.24-30
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• 2010

Interfacial evaluation and hydrophobicity of Ni-nanopowder/epoxy composites were investigated for self-sensing and actuation. Contact resistance and resistivity were measured using gradient micro-specimens. The actuation of the composites in the electromagnetic field was studied with three wave functions, i.e., sine, triangle and square functions. Due tothe presence of hydrophobic domains on the heterogeneous surface, the static contact angle of Ni-nanopowder/epoxy nanocomposite wasabout $100^{\circ}$, which was rather lower than that for super-hydrophobicity. The dynamic contact angle showed the similar trend of static contact angle. Ni-nanopowder/epoxy composite was responded wellfor both self-sensing and actuation in electromagnetic field due to the intrinsic metal property of Ni-nanopowder. Displacement of the actuator of Ni-nanopowder/epoxy composite was evaluated to obtain the maximum and the optimum performance using laser displacement sensor as functions of the wave type, frequency, and voltage. Actuation of Ni-nanopowder/epoxy composites also increased as functions of applied frequency and voltage. Actuated strain increased more rapidly at sine wave with increasing voltage compared to those of triangle or rectangular waves.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.1-19
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• 2008

This research is to analyze the force on landing 3 Type of Halfpipe Curves(Ellipse, Circle, Brachistochrone) based on the mechanical calculation of normal force on a sloping surface. Jumping off a platform on a bard horizontal surface, the flexing of the legs, the softness of the snow, the angle of the landing surface, initial velocity and the forward motion of the snowboarder can contribute to reducing the force on landing. But halfpipe is significantly determined by the curvature of surface. It is definitely verified that the Brachistochrone curve is more safety than others. However currently using the Ellipse curve is mostly safe too. If we consider the efficiency of construction, we can easily think there is no use of another curves except normal ellipse curved halfpipe. It would better that geometrically verity curved halfpipe should be designed for improving fluent skills to snowboarders. This methode of research can be a model of scientifical research on sports safety how can sportsman reduce critical injury by designing optimal halfpipe facilities and manual.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.744-751
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• 2010

In this paper, the design of multilayer radome within, the insertion loss, －0.3 dB in X-band with PSO was carried out based on two cases. The first is that, deciding material constant of skin and core, each layer thickness of c-sandwich radome with PSO is found and the second is that, deciding material constant and thickness of the skins of both sides, the material constant and thickness of three layers between skins of both sides using PSO is decided. The performance of the designed radome almost agreed with the required performance. It was showed that the radome design applying PSO algorithm is easy and fast and the optimum radome is also designed in combination of the various parameters of radome. From these results, the radome having various performance can be designed except the tedious calculation and also be applied to various radome structure.

• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.57-63
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• 2009

In order to effectively isolate the marine wastes with an effluent standard, the pretreatment process is required to isolate solid materials from the liquid-solid mixed wastes. The more effective the pretreatment becomes, the more processing capacity of posttreatment will be improved and process facilities will be downsized. In this paper, we suggested the vibrating reverse-slant screen, investigated the optimal vibration frequency and vibrator installation angle for the separation of the liquid solid mixed wastes. Several experiments for separation efficiency were conducted under the condition of various vibration frequency($35{\sim}60Hz$, 5Hz interval) and vibrator angle($0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $90^{\circ}$) considering the crack of screen. The screen inclination angle is set up the gradient as $3^{\circ}{\sim}5^{\circ}$ through the preliminary experiments. Also, we made two types of screen(respectively rectangle and square screen). The separation device has shown the optimum efficiency at vibrator angle $0^{\circ}$ and vibration frequency 60Hz, and has no relation with the shape of screen. And the proposed technology is verified by comparing with quantity of suspended solids before and after filtration.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.324-329
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• 2016

Constructed wetlands are widely applied in urban and rural areas for various purposes such as pollutants reduction, acquisition of eco-spaces and habitats, flooding reduction, acquisition of water resources and environmental education. Since the design of constructed wetlands utilizes ecosystems, special consideration must be given to ecological mechanisms, environmental mechanisms and hydrological mechanisms. To ensure the sustainable functionality of constructed wetlands, it is necessary to achieve stable flow rate and velocity, and remove sediments to ensure sufficient space for detention. To enhance the efficiency of constructed wetland sedimentation basins, this study determined the optimal position for baffle installation, and applied Computational Fluid Dynamics (CFD) to the cross-sectional design of wetlands. CFD analysis revealed that the decrease in flow velocity with baffle installation enhanced the efficiency of sedimentation of particulate matters. Vertical baffles had higher sedimentation efficiency than those with an inclined angle. When vertical baffles were installed in the sedimentation basin of a hybrid constructed wetland to reduce non-point source pollutants in urban areas, the average flow velocity within the basin decreased by 10~30%, while the sedimentation efficiency improved by 1.3~1.5 times. The application of CFD to constructed wetlands is expected to improve the cost efficiency of designing hybrid constructed wetlands with high removal efficiency.