• Journal of the Korea Society of Computer and Information
• /
• v.11 no.6 s.44
• /
• pp.87-97
• /
• 2006

This study aims to identify the effect that the perceived usefulness and perceived ease of use have on learner flow in e-learning community. Based on literature review and Technology Acceptance Model(TAM), a potential model and five hypotheses were suggested. Questionnaire was carried out among 62 members of one e-learning community for preparatory teacher Cronbach alpha of the questionnaire was.88. The collected data were analyzed through correlation analysis and path analysis. The results of this research are as follows. Three hypotheses were adopted: Perceived usefulness will affect on attitudinal flow, Perceived ease of use will affect on attitudinal flow. and Attitudinal flow will affect on behavioral flow. Two hypotheses were rejected;. Perceived usefulness will affect on perceived ease of use and Perceived ease of use will affect on behavioral flow. The model revised through the results of path analysis had good-fitness. That is. overall fit measures (RMSEA, CFI. NNFI). indexes that show the suitability of the model were quite good. Findings of this study suggested the important strategies for designing e-learning community in order to promote learner flow.

• Journal of Korean Society of Transportation
• /
• v.22 no.3 s.74
• /
• pp.109-125
• /
• 2004

In recent decades, microscopic simulation models have become powerful tools to analyze traffic flow on highways and to assist the investigation of level of service. The existing microscopic simulation models simulate an individual vehicle's speed based on a constant free-flow speed dominantly specified by users and driver's behavior models reflecting vehicle interactions, such as car following and lane changing. They set a single free-flow speed for a single vehicle on a given link and neglect to consider the effects of highway design elements to it in their internal simulation. Due to this, the existing models are limitted to provide with identical simulation results on both curved and tangent sections of highways. This paper presents a model developed to estimate the change of free-flow speeds based on highway design elements. Nine neural network models were trained based on the field data collected from seven different freeway curve sections and three different locations at each section to capture the percent changes of free-flow speeds: 100 m upstream of the point of curve (PC) and the middle of the curve. The model employing seven highway design elements as its input variables was selected as the best : radius of curve, length of curve, superelevation, the number of lanes, grade variations, and the approaching free-flow speed on 100 m upstream of PC. Tests showed that the free-flow speeds estimated by the proposed model were statistically identical to the ones from the field at 95% confidence level at each three different locations described above. The root mean square errors at the starting and the middle of curve section were 6.68 and 10.06, and the R-squares at these points were 0.77 and 0.65, respectively. It was concluded from the study that the proposed model would be one of the potential tools introducing the effects of highway design elements to free-flow speeds in simulation.

• Proceedings of the KIEE Conference
• /
• 2007.11a
• /
• pp.212-213
• /
• 2007

In case of a line-to-ground fault at transmission lines, a portion of fault current will flow into the earth through the footings of the faulted tower causing electrical potential rise nearby the faulted tower footings. In this situation, any buried pipelines or structures nearby the faulted tower can be exposed to the electrical stress by earth potential rise. Although many research works has been conducted on this phenomena, there has been no clear answer of the required separation distance between tower footings and neary buried pipeline because of its dependancy on the soil electrical charactersics of the concerned area and the faulted system. In this paper, an analytical formula to calculate the requried sepeartion distance from the faulted tower has been derived.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.193.1-193.1
• /
• 2010

Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong dam. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems.

• 한국태양에너지학회:학술대회논문집
• /
• 2011.04a
• /
• pp.235-240
• /
• 2011

Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong darn. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.62 no.3
• /
• pp.95-107
• /
• 2020

The failures of the agricultural reservoirs that most have more than 50 years, have increased due to the abnormal weather and localized heavy rains. There are many studies on the prediction of damage from reservoir collapse, however, these referenced studies focused on evaluating reservoir collapse as single unit and applyed to one and two dimensional hydrodynamic model to identify the fluid flow. This study is to estimate failure probability of spillway, sliding, bearing capacity and overflowing targeting small and medium scale agricultural reservoirs. In addition, we calculate failure probability by complex mode. Moreover, we predict downstream flood damage by reservoir failure applying three dimensional hydrodynamic model. When the reservoir destroyed, the results are as follows; (1) the flow of fluid proceeds to same stream direction and to a lower slope by potential and kinetic energy; (2) The predicted damage in downstream is evaluated that damage due to building destruction is the highest.

• Journal of the Society of Naval Architects of Korea
• /
• v.40 no.5
• /
• pp.17-25
• /
• 2003

Velocity field behind a container ship model with a rotating propeller has been investigated using PIV (particle image velocimetry) system. Four hundred instantaneous velocity fields were measured at 4 different blade phases and ensemble-averaged to investigate the spatial evolution of vortical structure of near wake within one propeller diameter downstream. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed due to the boundary layers developed on the blade surfaces. The interaction between bilge vortex developed along the hull surface and the tangential velocity component of incoming flow causes to have asymmetric flow structure in the transverse plane.

• International Journal of Concrete Structures and Materials
• /
• v.6 no.1
• /
• pp.59-64
• /
• 2012

Sand-concrete is being researched for potential usage in construction in Saharan regions of Algeria, because of shortage in coarse aggregate resources. This research work deals with the effect of dune sand, available in huge quantities in these regions, on the properties of flowing sand-concrete (FSC) prepared with different proportions of dune and river sands. Mini-cone slump test, v-funnel flow-time test and viscosity measurements were used to characterize the behaviour of FSC in fresh state. The 28-day compressive strength was also determined. Test results show that an optimal content of dune sand, which makes satisfied fresh and hardened properties of FSC, is obtained. Moreover, the obtained flow index (constant b) calculated by the help of power-law viscosity model is successfully correlated to the experimental results of v-funnel flow time.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.30 no.2
• /
• pp.95-104
• /
• 1988

This study refers to the development of a hydrologic model simulating daily inflow and release rates for inigation reservoirs. A daily - based model is needed for adequate operation of an irrigation reservoir sufficing the water demand for paddy fields which is closely related to meteorological conditions. And the objective of this study is to develop a reservoir release rate model and then to calibrata the parameters. The release rates model considers daily water demands , water supply for transplanting, minmum release for maintaining canal flow, and maxirnun and regular flooding depth for determining effective rainfall on paddy fields. Each of the factors in the model was regarded as a lumped pararuter representing the average condition of a whole irrigated area. The water demand was estimated form the potential evapotranspiration by Penman method, the effective rainfall, and the infiltration on paddy fields. The release model was found to be capable of adequately simulating daily reservoir releases based on meteorological data.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.8 no.2
• /
• pp.159-166
• /
• 2010

The block-scale groundwater flow system at Olkiluoto site in Finland was simulated. The heterogeneous and anisotropic hydraulic conductivity field for the domain was constructed from the discrete fracture network, which considered only the fractured zones identified in the deep boreholes installed in the study site. The groundwater flow model was calibrated by adjusting the recharge rate and the transmissivities of the fractured zones to fit the calculated hydraulic heads and into- and out-flow rates in the observation intervals of the boreholes with the observed ones. In the calibrated model, the calculated flow rates at some intervals were not in accordance with the observed ones although the calculated hydraulic heads fit well with the observed ones, which revealed that the number of the conduits for groundwater flow is insufficient in the conceptual model for groundwater flow modeling. Therefore, it was recommended that the potential local conduits such as background fractures should be added to the present conceptual model.