• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.535-542
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• 2007

The Geumho river watershed located in the middle of the Nakdong river has been threatened by high population growth and urbanization. Of concern specifically is the potential impact of future developments in the watershed on the reduction of base flow and the consequent risk of degradation of ecological habitats in Geumho river. Anticipated increase in imperviousness, on the other hand, is expected to elevate flood risk and the associated environmental damage. A watershed hydrology based modeling study is initiated in this study to assist in planning for sustainable future development in the Geumho river watershed. The Soil and Water Assessment Tool (SWAT) is selected to model the impact of urbanization in the Geumho river watershed on the hydrologic response thereof. The modeling results show that in general the likelihood that the watershed will experience high and low stream flows will increase in view of the urbanization so far achieved.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.603-609
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• 2020

The purpose of this study is to research dampers, which are applied mainly to buildings adjacent to the coast, such as nuclear facilities, and used for ventilation and can safely protect lives and equipment in emergency situations. Comparing the equivalent stress for three models with hinge reinforcement and support reinforcement based on the early design model for Damper, in the Base model, the highest stress occurred in the part of hinge, especially in the centrally mounted hinge, and after reinforced the hinge, it was occurred in the rear support. For models reinforced hinges and supports, it is considered that reinforcement for stiffness will be required in the future as it entered within the range of allowable stress. For the safety factor distribution, the minimum safety ratio was sufficiently secured at least 1 and was high at the edge of the Damper frame and the Blade. As the hinge was reinforced, the safety factor distribution of Blade was increased, and it was verified that the safety factor was secured through the support reinforcement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4724-4747
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• 2016

To efficiently reduce on-grid energy consumption, the admission control algorithm in the hybrid energy powered cellular network (HybE-Net) with base stations (BSs) powered by on-grid energy and solar energy is studied. In HybE-Net, the fluctuation of solar energy harvesting and energy consumption may result in the imbalance of solar energy utilization among BSs, i.e., some BSs may be surplus in solar energy, while others may maintain operation with on-grid energy supply. Obviously, it makes solar energy not completely useable, and on-grid energy cannot be reduced at capacity. Thus, how to control user admission to improve solar energy utilization and to reduce on-grid energy consumption is a great challenge. Motivated by this, we first model the energy flow behavior by using stochastic queue model, and dynamic energy characteristics are analyzed mathematically. Then, fuzzy logic based admission control algorithm is proposed, which comprehensively considers admission judgment parameters, e.g., transmission rate, bandwidth, energy state of BSs. Moreover, the index of solar energy utilization balancing is proposed to improve the balance of energy utilization among different BSs in the proposed algorithm. Finally, simulation results demonstrate that the proposed algorithm performs excellently in improving solar energy utilization and reducing on-grid energy consumption of the HybE-Net.

• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.206-211
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• 2012

Process analysis was carried out during deposition of MgO by inductively coupled plasma assisted reactive magnetron sputtering in Ar and $O_2$ ambient. At the initiation of Mg sputtering with bipolar pulsed dc power in Ar ambient, total pressure showed sharp increase and then slow fall. To analyse partial pressure change, QMS was used in downstream region, where the total pressure was maintained as low as $10^{-5}$ Torr during plasma processing, good for ion source and quadrupole operation. At base pressure, the major impurity was $H_2O$ and the second major impurity was $CO/N_2$ about 10%. During sputtering of Mg in Ar, $H_2$ soared up to 10.7% of Ar and remained as the major impurity during all the later process time. When $O_2$ was mixed with Ar, the partial pressure of Ar decreased in proportion to $O_2$ flow rate and that of $H_2$ dropped down to 2%. It was understood as Mg target surface was oxidized to stop $H_2$ emission by Ar ion sputtering. With ICP turned on, the major impurity $H_2$ was converted into $H_2O$ consuming $O_2$ and C was also oxidized to evolve CO and $CO_2$.

• Earthquakes and Structures
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• v.12 no.4
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• pp.457-468
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• 2017

When studying the vibration of a suspension bridge based on the traffic-bridge coupled system, most researchers ignored the contribution of the pavement response. For example, the pavement was simplified as a rigid base and the deformation of pavement was ignored. However, the action of deck pavement on the vibration of vehicles or bridges should not be neglected. This study is mainly focused on establishing a new methodology fully considering the effects of bridge deck pavement, probabilistic traffic flows, and varied road roughness conditions. The bridge deck pavement was modeled as a boundless Euler-Bernoulli beam supported on the Kelvin model; the typical traffic flows were simulated by the improved Cellular Automaton (CA) traffic flow model; and the traffic-pavement-bridge coupled equations were established by combining the equations of motion of the vehicles, pavement, and bridge using the displacement and interaction force relationship at the contact locations. The numerical studies show that the proposed method can more rationally simulate the effect of the pavement on the vibrations of bridge and vehicles.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.241-244
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• 2009

Recently car navigation systems which are widely spreaded and provide routes exactly have been evolved. The systems use various information and techniques as follows. In order to provide shortest path with good flow, realtime traffic information provided by DMB is used. Augmented reality technique is also introduced to give the sense of real to driver by displaying real images captured by camera during driving. But these operate well when the GPS receives data normally. Exact information about the position of vehicles becomes a base that supports the above function with realities. This paper proposes a method for compensating a given path. It uses various information by integrated vehicle networks when the GPS does not operates normally.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.520-526
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• 2012

The appearance of the negative differential pressure(NDP), in which the shot base pressure is higher than the breech pressure, indicates that a potential damage on the gun system is increased. In order to safeguard the gun system, the igniter must be designed to minimize the NDP during the firing process. From this reason, the effect of igniter's burning rate on the NDP of the interior ballistics has been investigated through the numerical simulations. The NDP has been increased with increment of the coefficient in the burning rate of the igniter. A sudden change of the chamber pressure has been shown in case of using a singular coefficient.

• Asian Journal of Turfgrass Science
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• v.11 no.4
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• pp.303-309
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• 1997

The investigation was cycle of aluminum of surface soil elements in dynamic grassland ecosystems at a steady state in a Zoysia japonica and a Miscanthus sinensis ecosystem in Mt. Kwanak, Korea. Average amounts of total storage for aluminum in Z japonica and M. sinensis grasslands were 8,426mg /$m^2$ and 7,849mg /$m^2$ respectively. Decay constants estimated on the base of experimental and mathematical model, were 0.04 in Z japonica grassland, and 0.08 in M. sinensis grassland. Half time to decay aluminum of litter soils were 17.33 years in Z japonica grass-land, and 8.66 years in Al. sinensis grassland. 95% decay times in Z japonica, and in M. sinensis grassland were 75.0 years and 35.0 years respectively. Needed times to lose almost all of elements in Z japonica and M. sinensis grassland were 125.0 years, and 62.50 years respectively. The metals were losed more rapidly in M. sinensis than in Z japonica grassland. The cycle of aluminum was investigated to be related with soil acidity. Key words: Cycle of aluminum, Zoysia japonica. Miscanthus sinensis, Mt. Kwanak, Decay constants, Soil acidity.

• Journal of Ship and Ocean Technology
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• v.9 no.3
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• pp.1-13
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• 2005

A design procedure for a ship with minimum total resistance has been developed using a numerical optimization method called SQP (Sequential Quadratic Programming) to search for optimized hull form and CFD(Computational Fluid Dynamics) technique. The friction resistance is estimated using the ITTC 1957 model-ship correlation line formula and the wave making resistance is evaluated using a potential-flow panel method based on Rankine sources with nonlinear free surface boundary conditions. The geometry of hull surface is represented and modified using B-spline surface patches during the optimization process. Using the Series 60 hull ($C_B$ =0.60) as a base hull, the optimization procedure is applied to obtain an optimal hull that produces the minimum total resistance for the given constraints. To verify the validity of the result, the original model and the optimized model obtained by the optimization process have been built and tested in a towing tank. It is shown that the optimal hull obtained around $13\%$ reduction in the total resistance and around $40\%$ reduction in the residual resistance at a speed tested compared with that of the original one, demonstrating that the present optimization tool can be effectively used for efficient hull form designs.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.168-175
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• 2006

An experimental study was conducted to investigate the effect of the morphology of CNT on the thermal conductivity of suspensions. The effective thermal conductivities of the samples were measured using asteady-state cut bar apparatus method. Enhancements based on the thermal conductivity of the base fluid are presented as functions of both the volume fraction and the temperature, Although functionalized SWNT produiced a more stable and homogeneous suspension, the addition of small amounts of surfactant to suspensions of 'as produced' SWNT demonstrated a greater increase in effective thermal conductivity than functionalized SWNT alone. The effective thermal conductivity enhancement corresponding to 1.0 percent by volume approached 10%, which was observed to be lower than expected, but more than twice the values, 3.5%, obtained for similar tests conducted using aluminum oxide suspensions. However, for suspensions of MWNT, the degree of enhancement was measured to be approximately 37%. It was postulated that the effect of clustering, resulting from the multiple heat-flow passages constituted by interconnecting neighboring CNT clusters, played an important role in significant enhancement of effective thermal conductivity.