• Journal of Korea Water Resources Association
• /
• v.50 no.6
• /
• pp.373-386
• /
• 2017

This study simulated water quality item and flow rate of subbasin for Saemangeum watershed using Soil and Water Assessment Tool (SWAT) model and Environmental Fluid Dynamics Code (EFDC) model which simulate hydraulic and water quality in three-dimensions. The simulated values corresponded to observed value well. The result of simulation for floodgate operations at the M3 and M5 points, it exceeds water quality standard and at the M3 and D3 points, change of range for concentration is too wide, and upstream of Saemangeum reservoir is sensitive to inflow flow rate. Compared to the annual average concentration for observed station according to the discharge conditions, improvement of water quality for upstream was apparently compared to the downstream. Range of influence for change of water quality presented that maximum discharge condition, the influence range is 22 km in the direction of the Saemangeum downstream from the Mankyung bridge, and 15 km in the downstream direction of saemangeum in the Dongjin bridge. This study result demonstrated that floodgate operating at upstream has significant influence on water quality management of Saemangeum reservoir and it needs to be considered in plans of water quality management for Floodgate operation on Saemangeum reservoir.

• Journal of Power System Engineering
• /
• v.21 no.5
• /
• pp.20-28
• /
• 2017

The steady-state, incompressible and three-dimensional numerical analysis was performed to investigate the flow fields around the seabed tiller used for soil improvement in coastal fisheries and the pulling force and buoyancy generated by tiller operation. The turbulence model used in this study is a realizable $k-{\varepsilon}$. As a results, at a stationary current or a current speed of 1.2 knots, where rotor rotates in a clockwise direction, a typical vortex pair appears near the tip of the rotor except for the edge, and the strength of the vortex pair increases with the number of revolutions of the rotor. The pulling force of the tiller rotating in the counterclockwise direction increases with the number of revolutions. Also, when the current flows at 1.2 knots and the rotor rotates clockwise, the pulling force of the tiller acts on the upstream side irrespective of the number of rotations of the rotor, so that no force is applied. The buoyancy of the tiller acts on the seawater surface if the flow direction inside the rotor is the same as the direction of rotation of the rotor, regardless of the current velocity, otherwise it acts on the seabed.

• Proceedings of the Optical Society of Korea Conference
• /
• 2005.02a
• /
• pp.162-163
• /
• 2005

One of the most important things in EPON(Ethernet Passive Optical Network) is that ONUs(Optical Network Units) have to share a channel in upstream direction. We proposed a new algorithm of Dynamic Bandwidth Allocation using Multiple LLID(Logical Link IDentifier). We show how to allocate bandwidth in Queues for improving performance from Bandwidth using Multiple LLID.

• Proceedings of the Optical Society of Korea Conference
• /
• 2005.02a
• /
• pp.164-165
• /
• 2005

As a channel is shared in upstream direction, a Dynamic Bandwidth Allocation(DBA) algorithm is necessary for Ethernet Passive Optical Network(EPON) to allocate bandwidths effectively. In this paper, we proposed a algorithm of DBA using a new Proportional Factor and analyzed it.

• 한국기계연구소 소보
• /
• v.4 no.2
• /
• pp.49-63
• /
• 1982

In this paper, a classical gust problem is treated by using the numerical lifting¬-surface theory to verify the effect of gust-a sudden fluctuating fluid velocity around an object, which is normal to the main stream direction-on the hydrody¬namic forces, especially the mean thrust in upstream direction, acting on the two¬-dimensional flat plate. In this case, the mean thrust wholly resorts to the leading edge suction, and it is the same situation to the case of the heaving plate in uniform flow. The ph¬enomenon of leading edge suction is very important for the flapping propulsion of animals, typical to fish and birds, and can be related to the prediction of the hydrodynamic forces acting on marine propellers operating in gustlike wakes of ships. The results of this paper can be easily superposed to those of the reference [1J in order to solve the problem of the two-dimensional oscillacting plate in gust

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.73-78
• /
• 2003

The InP thin films grown by metalorganic chemical vapor deposition (MOCVD) are widely used to optoelectronic devices such as laser diodes, wave-guides and optical modulators. Effects of various parameters controlling film growth rate such as gas-phase reaction rate constant, surface reaction rate constant and mass diffusivity are numerically investigated. Results show that at the upstream region where film growth rate increases with the flow direction, diffusion including thermal diffusion plays an important role. At the downstream region where the growth rate decreases with flow direction, film deposition mechanism is revealed as a mass-transport limited. Mass transport characteristics are also studied using systematic analyses.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.34 no.E
• /
• pp.45-59
• /
• 1992

At downstream part of the hydraulic structures such as spiliway or drainage gate, jet flow can occur by gate opening. If stream bed is not hard or bed protection is not sufficient, scour hole will be formed due to high shear stress of the jet flow. We call this primary scour. Once the scour hole is formed, a vortex occurs in it and this vortex causes additional scour. We call this secondary scour. The primary scour proceeds to downstream together with flow direction but the secondary one proceeds to upstream direction opposite to it. If the secondary one continues and reaches to the hydraulic structure, it can undermine the bottom of hydraulic structure and this will lead to failure of structure itself. Thus, it is necessary to know the physical features of the vortex structure in a scour hole, which is the main mechanism of the secondary scour. This study deals with the characteristics of the vortex structure and its shear stress which causes the secondary scour.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2420-2425
• /
• 2007

Heat transfer from three-dimensional heat-generating modules was investigated. A simulated electronic module in an array configured with dummy module elements was used to measure the average heat transfer coefficients. Various module arrangements were tested using module spacings of 0.85 and 1.15 cm for six Reynolds numbers ranging from 500 to 975. The results show that a module placed in-line with and upstream of a heated module results in the heat transfer enhancement due to a high level in turbulence prompted by upstream modules. The highest enhancement occurs when the separation distance between modules is close to the module length in the flow direction. Flow visualization reveals laminar flow on the front of the first module, slow recirculation regions on the sides parallel to the air stream, and turbulence on the back side. It appears that the first module serves to trip the air stream and produce a high level of turbulence, which enhances the heat transfer rate downstream.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.9
• /
• pp.784-790
• /
• 2012

In this paper, we propose a upstream transmission method to extend coverage in visible light communication (VLC) systems. We extend transmission distance by using focused infrared(IR) light emitting diodes(LEDs). Since the focused light covers just limited area, it might have a difficulty in transmitting data if the transmitter and receiver are not properly aligned. To solve this problem, we arrange multiple IR-LEDs in different direction and select a single best performing IR-LED among multiple IR-LEDs. Also, the transmission performance is periodically checked and another IR-LED is reselected to support the required quality of service (QoS) and to minimize battery consumption required by a mobile terminal.

• Proceedings of the KSRS Conference
• /
• v.2
• /
• pp.672-675
• /
• 2006

The geostrophic current component is estimated from the sea surface velocity observed by the long-range High-Frequency Ocean Radar (HF radar) system in the upstream of the Kuroshio, by comparing with geostrophic velocity determined from along-track T/P and Jason-1 altimetry data. However, the sea surface velocity of the HF radar (HF velocity) contains not only the geostrophic current but also the ageostrophic current such as tidal current and wind-driven Ekman current. Tidal current component is first extracted by the harmonic analysis of the time series of the HF velocity. Then, the Ekman current is further estimated from daily wind data of IFREMER by applying the least-square method to the residual difference between the HF velocity and the altimetry geostrophic velocity. As a result, the Ekman current in the HF velocity is estimated as 1.32 % of the wind speed and as rotated 45$^{\circ}$ clockwise to the wind direction. These parameters are found almost common in the Kuroshio area and in the Open Ocean. After these corrections, the geostrophic velocity component in the HF velocity agrees well with the altimetry geostrophic velocity.