• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.827-831
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• 2009

Recently, frequency occurring flood and drought has increased the necessity of an effective water resources control and management of river flows. Therefore, the simulation of the flow distribution in natural rivers is great importance to the solution of a wide variety of practical flow problems in water resources engineering. However The serious problem facing two-dimensional hydraulic model is the treatment of wet and dry areas. The objective of this study is to investigate the wet and dry parameters that have direct relevance to model performance in situations where inundation of initially dry areas occurs. Several numerical simulations were carried out, which examined the performance of the marsh porosity method for the purpose of sensitivity analysis. Experimental channel and a variety of channel were performed for model tests. The results were compared with those of the observation data and simulation data of existing model. The RMA-2 model displayed reasonable flow distribution compare to the observation data and simulation data of existing model in dry area for application of natural river flow. As a result of this study, effectively applied marsh porosity method provide a reliable results for flow distribution of wet and dry area, it could be further developed to basis for extending to water quality and sediment transport analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6B
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• pp.363-371
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• 2012

In this study, the low-flow frequency analysis was performed to determine the low-flow standard of dam maintenance flow for Hwacheon and Chuncheon dams. For this purpose, two methods (case 1: low-flow frequency analysis using the monthly inflow data of the specified return periods, case 2: low-flow frequency analysis using the difference of monthly accumulated inflow) were applied. As a result, it is found that the monthly inflow data of the return periods by reflecting the statistical characteristics of Hwacheon and Chuncheon dams can be utilized to determine the standard of maintenance flow or water level.

• Journal of Chest Surgery
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• v.56 no.3
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• pp.179-185
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• 2023

Background: Assessments of air leaks are usually performed subjectively, precluding the use of air leaks as an evaluation factor. We aimed to identify objective parameters as predictive factors for prolonged air leak (PAL) and air leak cessation (ALC) from air flow data produced by a digital drainage system. Methods: Flow data records of 352 patients who underwent lung lobectomy were reviewed, and flow data at designated intervals (1, 2, and 3 hours postoperatively [POH] and 3 times a day thereafter [06:00, 13:00, 19:00]) were extracted. ALC was defined by flow less than 20 mL/min over 12 hours, and PAL was defined as ALC after 5 days. Cumulative incidence curves were obtained using Kaplan-Meier estimates of time to ALC. Cox regression analysis was performed to determine the effects of variables on the rate of ALC. Results: The incidence of PAL was 18.2% (64/352). Receiver operating characteristic curve analysis showed cut-off values of 180 mL/min for the flow at 3 POH and 73.3 mL/min for the flow on postoperative day 1; the sensitivity and specificity of these values were 88.9% and 82.5%, respectively. The rates of ALC by Kaplan-Meier analysis were 56.8% at 48 POH and 65.6% at 72 POH. Multivariate Cox regression analysis revealed that the flow at 3 POH (≤80 mL/min), operation time (≤220 minutes), and right middle lobectomy independently predicted ALC. Conclusion: Air flow measured by a digital drainage system is a useful predictor of PAL and ALC and may help optimize the hospital course.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.38-43
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• 2009

The objective of this study is to get a fundamental data for the shape of a robot which operates in blood vessels. The overall analysis was calculated with a CFD code. The flow was idealized as a pulsatile flow, and first the robot was assumed as a simple capsule model. Then a drag of the body in the flow was calculated, and this process was repeated, varying the shape. To validate all the result, the pulastile velocity simulation was compared with the theoretical data, and the drag of a body was compared with the existing data of the other papers first. Then with the next calculation the guideline for the design of robot shape was presented.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.18-27
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• 2020

Air lift pump operated by buoyancy is mainly used for the continuous circulation and the purification of fluids. In this study, the computational flow analysis has been performed with the geometric and operating conditions of the air lift pump. The numerical data from the analysis have been verified by comparing with the previous experimental data. The following results are obtained which advance the efficiency of the air lift pump. As the submergence length of pipe increases and the pipe length over the water surface decreases, the non-dimensional mass flow ratio increases in both cases. When the position of the air injection hole is within the pipe, the circulation range of the surrounding fluid becomes widened with the distance between the air injection hole and the pipe inlet relatively becoming narrower. It is more efficient both when the air injection velocity is at 10 m/s and at 15 m/s, and when the diameter of the pipe with holes is doubled near the water surface. It is expected that these results can be provided as fundamental data for operating the air lift pump.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.4
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• pp.227-236
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• 1986

In this paper, an integrated voice/data packet network with window flow control is modeled by a colsed multichain queueing system, and its performance is analyzed by the mean value analysis method. Particularly, for the analysis of a packet network having various kinds of messages with different priority classes, we introduce an approach based on the mean value analysis and the concept of effective capacity. By the mathematical analysis and computer simulation, we obtain the following network statistics in the steady state: Mean buffer occupancy at each node, utilization of link throughput of a virtual channel, and mean delay time of each message. Our iterative analysis method can predict the link data status in most cases within about 10 percent of accurady, and the statistics of voice messages and external data within 5 percent as compared to simulation results.

• KSTLE International Journal
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• v.1 no.1
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• pp.21-28
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• 2000

A computer program fur the analysis of engine lubrication systems has been developed. And a case study of a four cylinders gasoline engine is illustrated. This paper gives the mathematical models far oil flow through hydraulic tappet as well as those of oil jet and plain journal bearings. And the flow from an oil pump and the flow resistance through an oil filter is considered at various temperatures. In the analysis, the various design guidelines are applied. The distribution of flow and pressure of an engine lubrication system are calculated, and the pressure data compared with the experimental data at a few points in the engine lubrication system. This method is helpful to design of engine lubrication system efficiently.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.2
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• pp.15-24
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• 2016

This study conducted an evaluation of the extent of debris flow damage using SINMAP, which is slope stability analysis software based on the infinite slope stability method, and FLO-2D, a hydraulic debris flow analysis program. Mt. Majeok located in Chuncheon city in the Gangwon province was selected as the study area to compare the study results with an actual 2011 case. The stability of the slope was evaluated using a DEM of $1{\times}1m$ resolution based on the LiDAR survey method, and the initiation points of the debris flow were estimated by analyzing the overlaps with the drainage network, based on watershed analysis. In addition, the study used measured data from the actual case in the simulation instead of existing empirical equations to obtain simulation results with high reliability. The simulation results for the impact of the debris flow showed a 2.2-29.6% difference from the measured data. The results suggest that the extent of damage can be effectively estimated if the parameter setting for the models and the debris flow initiation point estimation are based on measured data. It is expected that the evaluation method of this study can be used in the future as a useful hazard mapping technique among GIS-based risk mapping techniques.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.276-276
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• 2018

In this paper the potential of the Principle Component Analysis(PCA) technique that can be used to detect leaks in water pipe network blocks was evaluated. For this purpose the PCA was conducted to evaluate the relevance of the calculated outliers of a PCA model utilizing the recorded pipe flows and the recorded pipe leak incidents of a case study water distribution system. The PCA technique was enhanced by applying the computational algorithms developed in this study. The algorithms were designed to extract a partial set of flow data from the original 24 hour flow data so that the variability of the flows in the determined partial data set are minimal. The relevance of the calculated outliers of a PCA model and the recorded pipe leak incidents was analyzed. The results showed that the effectiveness of detecting leaks may improve by applying the developed algorithm. However, the analysis suggested that further development on the algorithm is needed to enhance the applicability of the PCA in detecting leaks in real-world water pipe networks.

• Journal of Korean Society of Transportation
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• v.12 no.1
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• pp.97-116
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• 1994

Today advanced traffic management systems are required because of a high increase in traffic demand. Accordingly, the objective of this study is to take advantage of image processing systems and present image processing methods available for collection of the data on traffic characteristics, and then to investigate the possibility of traffic flow analysis by means of comparison and analysis of measured traffic flow. Data were collected at two places of Daegu city and Kyongbu expressway by using VTR. Rear view (down stream) and frontal view (up stream) methods were employed to compare and analyze traffic characteristics including traffic volume, speed, time-headway, time-occupancy, and vehicle-length, by analysis of measured traffic flow and image processing respectively. Judging from the results obtained by this study, image processing techniques are sufficient for the analysis of traffic volume, but a frame grabber equipped with high speed processor is necessary as well, with low level system judged to be sufficient for traffic volume analysis.