• Tunnel and Underground Space
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• v.4 no.1
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• pp.1-16
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• 1994

The study on the flow characteristics and analysis of groundwater in discontinuous rock mass is very important, since the water inflow into the underground opening during excavation induces serious stability and environmental problems. To investigate the flow through single rock joint, the effect of various aperture distribution on the groundwater flow has been analyzed. Observed through the analysis is the "channel flow", the phenomenon that the flow is dominant along the path of large aperture for given joint. The equivalent hydraulic conductivity is estimated and verified through the application of the joint network analysis for 100 joint maps generated statistically. Both the analytic aproach based on isotropic continuum premise and the joint network analysis are tested and compared analyzing the gorundwater inflow for underground openings of different sizes and varying joint density. The joint network analysis is considered better to reflect the geometric properties of joint distribution in analyzing the groundwater flow.ater flow.

• ETRI Journal
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• v.30 no.2
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• pp.238-248
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• 2008

At the extremes of the complexity-performance plane, there are two exemplary QoS management architectures: Integrated Services (IntServ) and Differentiated Services (DiffServ). IntServ performs ideally but is not scalable. DiffServ is simple enough to be adopted in today' core networks, but without any performance guarantee. Many compromise solutions have been proposed. These schemes, called quasi-stateful IntServ or stateful DiffServ, however, have not attracted much attention due to their inherently compromising natures. Two disruptive flow-based architectures have been recently introduced: the flow-aware network (FAN) and the flow-state-aware network (FSA). FAN's control is implicit without any signaling. FSA's control is even more sophisticated than that of IntServ. In this paper, we survey established QoS architectures, review disruptive architectures, discuss their rationales, and points out their disadvantages. A new QoS management architecture, flow-aggregate-based services (FAbS), is then proposed. The FAbS architecture has two novel building blocks: inter-domain flow aggregation and endpoint implicit admission control.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.397-397
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• 2015

The frequency of urban floods is recently increased as a consequence of climate change and haphazard development in urban area. To mitigate and prevent the flood damage, we generally utilized a numerical model to investigate the causes and risk of urban flood. Contrary to general flood inundation model simulating only the surface flow, the model needs to consider flow of the sewer network system like SWMM and ILLUDAS. However, this kind of model can not consider the interaction between the surface flow and drainage network. Therefore, we tried to evaluate the impact of bidirectional interaction between sewer and surface flow in urban flooding analysis based on simulations using the quasi-interacted model and the interacted model. As a general quasi-interacted model, SWMM5 and FLUMEN are utilized to analyze the flow of drainage network and simulate the inundation area, respectively. Then, FLO-2D is introduced to consider the interaction between the surface flow and sewer system. The two method applied to the biggest flood event occurred in July 2011 in Sadang area, South Korea. Based on the comparison with observation data, we confirmed that the model considering the interaction the sewer network and surface flow, showed a good agreement than the quasi-interacted model.

• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.2
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• pp.153-171
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• 2002

In this paper, we present an efficient pricing strategy, the pivot and probe Algorithm for Network Flow Problems(PAPANET), specifically for solving capacitated, linear network flow problem (NPs). The PAPANET begins with an initial relaxed network problem(RNP), consisting of all the nodes and initial candidate arcs(possibly a few least cost arcs form the original problem and a set of all the artificial and slack arcs). After an initial solution to the RNP is derived by pivoting, the PROBE procedure identifies a set of most violated arcs from the noncandidate arcs that are not considered to be in the current RNP, and adds them to the RNP. The procedure also discards a set of least favorable, zero flow, nonbasic arcs from the RNP. The new RNP is solved to optimality and the procedure continues until all of the dual constraints of the noncandidate arcs are satisfied by the dual solution to the RNP. The PAPANET effectively reduces the problem size, time per pivot, and solution CPU time by eliminating noncandidate arcs. Computational tests on randomly generated problems indicate that PAPANET achieves and average savings of 50-80% of the solution CPU time of that of a comparable standard network simplex implementation.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.64-71
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• 2016

Void fraction is an important parameter in the oil industry. This quantity is necessary for volume rate measurement in multiphase flows. In this study, the void fraction percentage was estimated precisely, independent of the flow regime in gas-liquid two-phase flows by using ${\gamma}-ray$ attenuation and a multilayer perceptron neural network. In all previous studies that implemented a multibeam ${\gamma}-ray$ attenuation technique to determine void fraction independent of the flow regime in two-phase flows, three or more detectors were used while in this study just two NaI detectors were used. Using fewer detectors is of advantage in industrial nuclear gauges because of reduced expense and improved simplicity. In this work, an artificial neural network is also implemented to predict the void fraction percentage independent of the flow regime. To do this, a multilayer perceptron neural network is used for developing the artificial neural network model in MATLAB. The required data for training and testing the network in three different regimes (annular, stratified, and bubbly) were obtained using an experimental setup. Using the technique developed in this work, void fraction percentages were predicted with mean relative error of <1.4%.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.410-421
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• 2006

In this work, we propose an analytic framework for dimensioning the link capacity of broadband access networks which provide universal broadband access services to a diverse kind of customers such as patient and impatient customers. The proposed framework takes into account the flow-level quality of service (QoS) of a connection as well as the packet-level QoS, via which a simple and systematic provisioning and operation of the network are provided. To that purpose, we first discuss the necessity of flow-aware network dimensioning by reviewing the networking technologies of the current and future access network. Next, we propose an analytic model for dimensioning the link capacity for an access node of broadband convergence networks which takes into account both the flow and packet level QoS requirements. By carrying out extensive numerical experiment for the proposed model assuming typical parameters that represent real network environment, the validity of the proposed method is assessed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.22-24
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• 2008

This paper presents a numerical model of internal flows in a lubricant supplying and scavenging flow path of an aero-engine lubrication system. The numerical model was built in the General Analysis Software of Aero-engine Lubrication System, GASLS, developed by Northwestern Polytechnical University. The lubricant flow flux, pressure and temperature distribution at steady state were calculated. GASLS is a general purpose computer program employed a 1-D steady state network algorithm for analyzing flowrates, pressures and temperatures in a complex flow network. All kinds of aero-engine lubrication systems can be divided into finite correlative typical elements and nodes from which the calculation network be developed in GASLS. Special emphasis is on how to use combined elements which is a type of typical elements to replace some complex components like bearing bores, accessory gearboxes or heat exchangers. This method can reduce network complexity and improve calculation efficiency. Final computational results show good agreement with experimental data.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.3
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• pp.487-500
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• 1997

In this paper, we introduce the shortest flow-generating path problem in the generalized network. As the simplest generalized network model, this problem captures many of the most salient core ingredients of the generalized network flows and so it provides both a benchmark and a point of departure for studying more complex generalized network models. We show that the generalized label-correcting algorithm for the shortest flow-generating path problem has O(mn) time complexity if it starts with a good point and also propose an O($n^3m^2$) algorithm for finding a good starting point. Hence, the shortest flow-generating path problem is solved in O($n^3m^2$) time.

• Journal of Information Processing Systems
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• v.19 no.1
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• pp.130-138
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• 2023

The traffic flow in an urban area is affected by the date, weather, and regional traffic flow. The existing methods are weak to model the dynamic road network features, which results in inadequate long-term prediction performance. To solve the problems regarding insufficient capacity for dynamic modeling of road network structures and insufficient mining of dynamic spatio-temporal features. In this study, we propose a novel traffic flow prediction framework called shared spatio-temporal attention convolution optimization network (SSTACON). The shared spatio-temporal attention convolution layer shares a spatio-temporal attention structure, that is designed to extract dynamic spatio-temporal features from historical traffic conditions. Subsequently, the graph optimization module is used to model the dynamic road network structure. The experimental evaluation conducted on two datasets shows that the proposed method outperforms state-of-the-art methods at all time intervals.

• Proceedings of the Korea Water Resources Association Conference
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• 1989.07a
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• pp.63-70
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• 1989