Utilizing multi-commodity flow formulations to solve network protection problems

2017 ◽  
Author(s):  
◽  
Gokhan Karakose
Keyword(s):  
Network Performance ◽  
Optimal Allocation ◽  
Valid Inequalities ◽  
User Equilibrium ◽  
Dual Model ◽  
Minimax Optimization ◽  
University Of Missouri ◽  
Commodity Flow ◽  
Network Protection ◽  
The Impact

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The identification of critical network components is of interest to both interdictors wishing to degrade the network's performance, and to defenders aiming to preserve network performance in the face of disruption. This dissertation focuses on methods for identifying critical subsets of nodes and/or arcs to fortify and/or disable for the purpose of network protection. A common link connecting all studies in this dissertation is our incorporation of the multi-commodity flow formulations into larger multi-level (e.g., minimax) optimization models. ... The last study examines network fortification models that are able to differentiate between failures that are random (e.g., caused by nature) and strategic network failures (e.g., caused by terrorist activities) when performing the allocation of protective resources. This distinction cannot be achieved in the models presented previously in this dissertation. The desired properties of such differentiating formulations are derived by specifying a set of priori assumptions. The criticality indexes in these models, which are necessary to assess the impact of a disruption, are pre-computed through the resolution of the multi-commodity based User Equilibrium (UE) traffic assignment model and applied to urban transportation networks. Novel valid inequalities and linearization techniques are applied to the dual version of the nonlinear UE multi-commodity model to improve its computational efficiency. Computational results demonstrate that the reformulated linear dual model is effective to solve large size instances to near-optimality; and that the optimal allocation of resources as identified by a component-based formulation may potentially be suboptimal when a network is at risk of multiple simultaneous failures for both types of disruptions (i.e., nature- and terrorist-based). We also demonstrate that fortification models for component or scenario-based disruptions can provide different resource allocations for both types of disruptions.

Simulating Automobile Emissions in an Integrated Urban Model

1996 ◽  
Vol 1520 (1) ◽  
pp. 71-80 ◽  
Author(s):  
William P. Anderson ◽  
Pavlos S. Kanaroglou ◽  
Eric J. Miller ◽  
Ronald N. Buliung
Keyword(s):  
Network Performance ◽  
User Equilibrium ◽  
Performance Information ◽  
Automobile Emissions ◽  
Peak Period ◽  
Urban Model ◽  
Assignment Algorithm ◽  
Combined Models ◽  
The Impact ◽  
Network Component

The network component of an integrated urban model called IMULATE is interfaced with the MOBILE5.C emissions models. IMULATE produces estimates of traffic flows and average speeds on each link in an urban road network using a user equilibrium assignment algorithm. This information is combined with speed-dependent emissions factors generated by MOBILE5.C to calculate estimates of the three types of emissions on a link-by-link basis. The combined models are implemented for the Hamilton, Ontario, Canada, metropolitan area. Simulations are conducted to illustrate the spatial patterns of emissions in the morning peak period and to demonstrate the impact of congestion on emissions estimates. The incorporation of detailed network performance information yields significant benefits in the estimation of regional automobile emissions.

scholarly journals HTPC: heterogeneous traffic-aware partition coding for random packet spraying in data center networks

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jiawei Huang ◽  
Shiqi Wang ◽  
Shuping Li ◽  
Shaojun Zou ◽  
Jinbin Hu ◽  
...  
Keyword(s):  
Data Center ◽  
Large Scale ◽  
Network Performance ◽  
Rooted Tree ◽  
Heterogeneous Traffic ◽  
Data Center Networks ◽  
Packet Reordering ◽  
Traffic Characteristics ◽  
Network Utilization ◽  
The Impact

AbstractModern data center networks typically adopt multi-rooted tree topologies such leaf-spine and fat-tree to provide high bisection bandwidth. Load balancing is critical to achieve low latency and high throughput. Although the per-packet schemes such as Random Packet Spraying (RPS) can achieve high network utilization and near-optimal tail latency in symmetric topologies, they are prone to cause significant packet reordering and degrade the network performance. Moreover, some coding-based schemes are proposed to alleviate the problem of packet reordering and loss. Unfortunately, these schemes ignore the traffic characteristics of data center network and cannot achieve good network performance. In this paper, we propose a Heterogeneous Traffic-aware Partition Coding named HTPC to eliminate the impact of packet reordering and improve the performance of short and long flows. HTPC smoothly adjusts the number of redundant packets based on the multi-path congestion information and the traffic characteristics so that the tailing probability of short flows and the timeout probability of long flows can be reduced. Through a series of large-scale NS2 simulations, we demonstrate that HTPC reduces average flow completion time by up to 60% compared with the state-of-the-art mechanisms.

scholarly journals A new meta-heuristic pathfinder algorithm for solving optimal allocation of solar photovoltaic system in multi-lateral distribution system for improving resilience

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Varaprasad Janamala
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Voltage Stability ◽  
Optimal Allocation ◽  
Photovoltaic System ◽  
Solar Photovoltaic ◽  
Voltage Profile ◽  
Pv System ◽  
Solar Photovoltaic System ◽  
The Impact

AbstractA new meta-heuristic Pathfinder Algorithm (PFA) is adopted in this paper for optimal allocation and simultaneous integration of a solar photovoltaic system among multi-laterals, called interline-photovoltaic (I-PV) system. At first, the performance of PFA is evaluated by solving the optimal allocation of distribution generation problem in IEEE 33- and 69-bus systems for loss minimization. The obtained results show that the performance of proposed PFA is superior to PSO, TLBO, CSA, and GOA and other approaches cited in literature. The comparison of different performance measures of 50 independent trail runs predominantly shows the effectiveness of PFA and its efficiency for global optima. Subsequently, PFA is implemented for determining the optimal I-PV configuration considering the resilience without compromising the various operational and radiality constraints. Different case studies are simulated and the impact of the I-PV system is analyzed in terms of voltage profile and voltage stability. The proposed optimal I-PV configuration resulted in loss reduction of 77.87% and 98.33% in IEEE 33- and 69-bus systems, respectively. Further, the reduced average voltage deviation index and increased voltage stability index result in an improved voltage profile and enhanced voltage stability margin in radial distribution systems and its suitability for practical applications.

scholarly journals Co-Simulation Framework for Optimal Allocation and Power Management of DGs in Power Distribution Networks Based on Computational Intelligence Techniques

Electronics ◽  
2021 ◽  
Vol 10 (14) ◽  
pp. 1648
Author(s):  
Marinko Barukčić ◽  
Toni Varga ◽  
Vedrana Jerković Jerković Štil ◽  
Tin Benšić
Keyword(s):  
Power System ◽  
Power Management ◽  
Computational Intelligence ◽  
Input Data ◽  
Optimization Problem ◽  
Optimal Allocation ◽  
Distribution Networks ◽  
Distributed Generations ◽  
Data Resolution ◽  
The Impact

The paper researches the impact of the input data resolution on the solution of optimal allocation and power management of controllable and non-controllable renewable energy sources distributed generation in the distribution power system. Computational intelligence techniques and co-simulation approach are used, aiming at more realistic system modeling and solving the complex optimization problem. The optimization problem considers the optimal allocation of all distributed generations and the optimal power control of controllable distributed generations. The co-simulation setup employs a tool for power system analysis and a metaheuristic optimizer to solve the optimization problem. Three different resolutions of input data (generation and load profiles) are used: hourly, daily, and monthly averages over one year. An artificial neural network is used to estimate the optimal output of controllable distributed generations and thus significantly decrease the dimensionality of the optimization problem. The proposed procedure is applied on a 13 node test feeder proposed by the Institute of Electrical and Electronics Engineers. The obtained results show a huge impact of the input data resolution on the optimal allocation of distributed generations. Applying the proposed approach, the energy losses are decreased by over 50–70% by the optimal allocation and control of distributed generations depending on the tested network.

A Optimization Traffic Grooming Algorithm Based on Bidirectional SONET Ring Topology Network

2015 ◽  
Vol 727-728 ◽  
pp. 996-999 ◽  
Author(s):  
Su Xia Cui
Keyword(s):  
Resource Utilization ◽  
Network Performance ◽  
Minimum Weight ◽  
Routing Algorithm ◽  
Traffic Grooming ◽  
Network Routing ◽  
Ring Network ◽  
Network Resource ◽  
Blocking Rate ◽  
The Impact

The issue of WDM network traffic grooming has been a hot in the field of research. The implementation of traffic grooming technology can improve the utilization of wavelength channels, reducing the link delay and the blocking rate of the network, which to improve network resource utilization and optimize network performance. This article mainly studies all-optical network routing algorithm utilizing WDM technology to achieve the dynamic traffic grooming and propose a optimization grooming policy -HaffmanGroom (M) algorithms which based on SONET / WDM ring network. The most important feature of this algorithm is that the SONET / WDM ring network of multiple multicast request packet , with a minimum weight of the light path priority selection method, the flow of requests each group effectively optimize ease . The algorithm takes into account the impact of the link request factor and link hops to optimize the link selection. The simulation results show that under the conditions of factors and the number of hop a request fully consider the impact of these two factors to the link, and can achieve optimal link with the smallest weights for effective data transmission, improving resource utilization, reducing blocking rate in order to achieve the purpose of optimizing network performance.

scholarly journals Performance Analysis of Wireless Local Area Network for a High-/Low-Priority Traffic Ratio at Different Numbers of Access Categories

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 693
Author(s):  
Kvitoslava Obelovska ◽  
Olga Panova ◽  
Vincent Karovič
Keyword(s):  
Network Performance ◽  
Wireless Local Area Network ◽  
Local Area Network ◽  
Local Area ◽  
Area Network ◽  
Large Network ◽  
Medium Access ◽  
Massive Growth ◽  
Adaptive Adjustment ◽  
The Impact

The performance of Wireless Local Area Network (WLAN) is highly dependent on the processes that are implemented in the Medium Access Control (MAC) sublayer regulated by the IEEE 802.11 standard. In turn, various parameters affect the performance of the MAC sublayer, the most important of which is the number of stations in the network and the offered load. With the massive growth of multimedia traffic, research of the network performance depending on traffic types is relevant. In this paper, we present the impact of a high-/low-priority traffic ratio on WLAN performance with different numbers of access categories. The simulation results show different impact of high-/low-priority traffic ratio on the performance of the MAC sublayer of wireless LANs depending on different network-sizes and on network conditions. Performance of the large network with two access categories and with the prevalent high-priority traffic is significantly higher than in the case of using four categories on the MAC sublayer. This allows us to conclude that the performance improvement of the large network with the prevalent high-priority traffic can be achieved by an adaptive adjustment of the access categories number on the MAC sublayer.

scholarly journals Developing a Hybrid Optimization Algorithm for Optimal Allocation of Renewable DGs in Distribution Network

2021 ◽  
Vol 3 (2) ◽  
pp. 409-423
Author(s):  
Ayman Awad ◽  
Hussein Abdel-Mawgoud ◽  
Salah Kamel ◽  
Abdalla A. Ibrahim ◽  
Francisco Jurado
Keyword(s):  
Power Systems ◽  
Distribution System ◽  
Optimal Allocation ◽  
Hybrid Technique ◽  
Radial Distribution System ◽  
Hybrid Optimization Algorithm ◽  
Power Quality Improvement ◽  
Sine Cosine Algorithm ◽  
Optimized Allocation ◽  
The Impact

Distributed generation (DG) is becoming a prominent key spot for research in recent years because it can be utilized in emergency/reserve plans for power systems and power quality improvement issues, besides its drastic impact on the environment as a greenhouse gas (GHG) reducer. For maximizing the benefits from such technology, it is crucial to identify the best size and location for DG that achieves the required goal of installing it. This paper presents an investigation of the optimized allocation of DG in different modes using a proposed hybrid technique, the tunicate swarm algorithm/sine-cosine algorithm (TSA/SCA). This investigation is performed on an IEEE-69 Radial Distribution System (RDS), where the impact of such allocation on the system is evaluated by NEPLAN software.

Friends in high places : two essays on the importance of corporate political connections

2015 ◽  
Author(s):  
◽  
Reza Houston
Keyword(s):  
Initial Public Offering ◽  
Political Connections ◽  
Target Firm ◽  
University Of Missouri ◽  
Accounting Performance ◽  
The Public ◽  
Public Offering ◽  
The University ◽  
The Impact ◽  
The Relationship

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This study is an examination of the relationship between political connections and the undertaking of major firm events. In our first essay, presented in Chapter 3, we examine the impact politically connected appointments have on firm acquisition behavior. Using proxy statements, we create a unique database of politically connected bidders and merger targets. We find that bidders who hire connected individuals to the board or management team are more likely to avoid merger litigation. Connected bidders make more bids after the appointment. These firms also bid on larger targets. We determine there is a positive relation between the control premium and the relative of the target's connections. Connected acquirers have superior post-merger accounting performance, particularly when they acquire a connected target firm. In the second essay, presented in Chapter 4, we examine the relationship between political connections of private firms and the initial public offering process. Using registration statement information, we create a unique database of politically connected IPO firms. We find that political connections are substitutes to high-quality underwriters and big four auditors. Politically connected firms manage earnings more highly upward than non-connected firms prior to the public offering. Politically connected firms also exhibit less underpricing than non-connected firms. Politically connected IPO firms also have superior post-IPO returns relative to non-connected IPO firms.

Differences of instructor presence levels in predominately online versus predominately not online courses within the community college setting

2018 ◽  
Author(s):  
◽  
Marcie M. Cutsinger
Keyword(s):  
Community Of Inquiry ◽  
Online Courses ◽  
Online Course ◽  
University Of Missouri ◽  
Significance Level ◽  
Learning Modalities ◽  
Significant Difference ◽  
Instructor Presence ◽  
Community Of Inquiry Framework ◽  
The Impact

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The purpose of this study was to gain insight into the level of instructor presence in the predominately online versus the predominately not online course. The increase in both the number of students enrolling on online courses and the number of courses/programs offered magnifies the need to address instructor presence. This case study considers students' perception of instructor presence in a predominately online and predominately not online course. Instructor presence was examined using the Community of Inquiry framework. The Community of Inquiry is a framework used to examine social, teaching and cognitive presence and the impact of such. Data was gathered from two courses in the different learning modalities. Students were enrolled in the courses at the same time with the same instructor. Statistical analysis utilized in this study included the Mann Whitney U, Spearman's rho and Kendall tau. A significance level of P less than (.05) was used for all tests. This research found no statistically significant difference in the levels of instructor presence in a predominately online course when compared to a predominately not online course. The two significant results in relation to instructor presence and course satisfaction were mixed. Course outcome and instructor presence are addressed with discussion and recommendations for further research included. This study contributes to the research by providing further data regarding students' perception of and the significance of instructor presence.

scholarly journals Equitable Allocation of Blue and Green Water Footprints Based on Land-Use Types: A Case Study of the Yangtze River Economic Belt

2018 ◽  
Vol 10 (10) ◽  
pp. 3556 ◽  
Author(s):  
Gang Liu ◽  
Lu Shi ◽  
Kevin Li
Keyword(s):  
Land Use ◽  
Water Resources ◽  
Agricultural Land ◽  
Optimal Allocation ◽  
Water Footprint ◽  
Agricultural Water ◽  
Land Area ◽  
Lexicographic Optimization ◽  
The Impact

This paper develops a lexicographic optimization model to allocate agricultural and non-agricultural water footprints by using the land area as the influencing factor. An index known as the water-footprint-land density (WFLD) index is then put forward to assess the impact and equity of the resulting allocation scheme. Subsequently, the proposed model is applied to a case study allocating water resources for the 11 provinces and municipalities in the Yangtze River Economic Belt (YREB). The objective is to achieve equitable spatial allocation of water resources from a water footprint perspective. Based on the statistical data in 2013, this approach starts with a proper accounting for water footprints in the 11 YREB provinces. We then determined an optimal allocation of water footprints by using the proposed lexicographic optimization approach from a land area angle. Lastly, we analyzed how different types of land uses contribute to allocation equity and we discuss policy changes to implement the optimal allocation schemes in the YREB. Analytical results show that: (1) the optimized agricultural and non-agricultural water footprints decrease from the current levels for each province across the YREB, but this decrease shows a heterogeneous pattern; (2) the WFLD of 11 YREB provinces all decline after optimization with the largest decline in Shanghai and the smallest decline in Sichuan; and (3) the impact of agricultural land on the allocation of agricultural water footprints is mainly reflected in the land use structure of three land types including arable land, forest land, and grassland. The different land use structures in the upstream, midstream, and downstream regions lead to the spatial heterogeneity of the optimized agricultural water footprints in the three YREB segments; (4) In addition to the non-agricultural land area, different regional industrial structures are the main reason for the spatial heterogeneity of the optimized non-agricultural water footprints. Our water-footprint-based optimal water resources allocation scheme helps alleviate the water resources shortage pressure and achieve coordinated and balanced development in the YREB.

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