Operating Characteristics Of Networks Research Articles

Research on high-proportion distributed photovoltaic access planning method considering voltage over limit risk

The current distributed PV access planning method mainly controls the access capacity, ignoring the impact of different access locations on the distribution network operation, which leads to the inability of PV to be fully consumed and generates large disturbances. To improve the utilization efficiency of PV power generation and solve the above-mentioned shortcomings, a high-proportion distributed PV access planning method that considers the risk of voltage crossing limits is studied. After analyzing the changes in distribution network operation characteristics after accessing a high-proportion distributed PV, the voltage crossing risk is estimated by calculating the network current. Multiple optimization objectives including voltage crossing risk are established to build the access planning model. The access planning results are obtained by solving the model with the multi-intelligence algorithm. After the distribution network experiment, the method considering the voltage crossing risk improves the PV consumption by about 18.3%, the connected PV generates less disturbance to the distribution network, and the access point is better.

Analysis of cascading failures of power cyber-physical systems considering false data injection attacks

This study considers the performance impacts of false data injection attacks on the cascading failures of a power cyber-physical system, and identifies vulnerable nodes. First, considering the monitoring and control functions of a cyber network and power flow characteristics of a power network, a power cyber-physical system model is established. Then, the influences of a false data attack on the decision-making and control processes of the cyber network communication processes are studied, and a cascading failure analysis process is proposed for the cyber-attack environment. In addition, a vulnerability evaluation index is defined from two perspectives, i.e., the topology integrity and power network operation characteristics. Moreover, the effectiveness of a power flow betweenness assessment for vulnerable nodes in the cyber- physical environment is verified based on comparing the node power flow betweenness and vulnerability assessment index. Finally, an IEEE14-bus power network is selected for constructing a power cyber-physical system. Simulations show that both the uplink communication channel and downlink communication channel suffer from false data attacks, which affect the ability of the cyber network to suppress the propagation of cascading failures, and expand the scale of the cascading failures. The vulnerability evaluation index is calculated for each node, so as to verify the effectiveness of identifying vulnerable nodes based on the power flow betweenness.

Online Spatiotemporal Popularity Learning via Variational Bayes for Cooperative Caching

Herein, we focus on an end-to-end design of a proactive cooperative caching strategy for a multi-cell network. The design is challenging as it involves two interrelated problems: the ability to predict future content popularity and to meet network operation characteristics. To this end, we first formulate a cooperative content caching in order to optimize the aggregated network cost for delivering contents to users. An efficient proactive caching policy requires an accurate prediction of time-varying content popularity. Content popularity has temporal and spatial dependencies and therefore, we develop a probabilistic dynamical model for content popularity prediction by exploiting its spatiotemporal correlations. To achieve an accurate tracking and prediction of content popularity evolution, the proposed dynamical model is non-linear and incorporates non-Gaussian distributions. We use Variational Bayes (VB) approach for estimating the model parameters. The VB provides mathematical tractability. We then develop an online VB method that works with streaming data where content request arrives sequentially. Using extensive simulations study on a real-world dataset, we show that our online VB based dynamical model provides improved performance compared to conventional content caching policies.

Optimal design of reward-penalty demand response programs in smart power grids

In smart and sustainable power grids, incentive-based demand response programs (DRPs) encourage customers to shift their demand from peak load periods. Broad participation of customers in these programs may lead to a peak rebound and the distribution system congestion in lower load periods, endangering the supply of reliable and sustainable electricity to urban consumers. To tackle these issues, this paper proposes a reward-penalty DRP for customers in smart distribution networks. In the proposed program, the customers receive rewards as they reduce or shift their demands in requested hours. The customers may also be penalized if their demands exceed predefined thresholds. An optimization problem is proposed to determine the optimal penalty and reward values. The objective function is to maximize the distribution company's profit, considering operational constraints of the distribution system. The proposed program is examined on a test system, and the results are compared with the broad application of conventional incentive-based DRPs. The results indicate that the proposed reward-penalty DRP can improve the network operational characteristics and mitigate the peak rebound, without imposing more costs on customers.

A Simplified Analytical Approach for Optimal Planning of Distributed Generation in Electrical Distribution Networks

DG-integrated distribution system planning is an imperative issue since the installing of distributed generations (DGs) has many effects on the network operation characteristics, which might cause significant impacts on the system performance. One of the most important characteristics that mostly varies because of the installation of DG units is the power losses. The parameters affecting the value of the power losses are number, location, capacity, and power factor of the DG units. In this paper, a new analytical approach is proposed for optimally installing DGs to minimize power loss in distribution networks. Different parameters of DG are considered and evaluated in order to achieve a high loss reduction in the electrical distribution networks. The algorithm of the proposed approach has been implemented using MATLAB software and has been tested and investigated on 12-bus, 33-bus, and 69-bus IEEE distribution test systems. The results show that the proposed approach can provide an accurate solution via simple algorithm without using exhaustive process of power flow computations.

Optimal Energy Flow Calculation of Combined Natural Gas, Cooling, Heating and Power Joint Supply Park Microgrid

The combined natural gas, cooling, heating and power joint supply (CNCHP) microgrid of an industrial park has the advantages of cascaded use of energy, which can effectively improve energy efficiency and reduce pollutant emissions. In this paper, the optimal energy flow calculation model of CNCHP microgrid is established. Minimizing the total running cost of the microgrid is as the objective function, and the network operation characteristics of the cooling network, heating network, power supply network and gas supply network is considered. The model includes the loss characteristics and security operation constraints of various types of energy networks, and the obtained optimal operation schedule can meet the actual operational requirements of the microgrid. Taking a CNCHP microgrid of an industrial park as an example, the correctness and validness of the proposed optimal calculation model are verified. The results show that the optimal operation scheme of the CNCHP microgrid can effectively reduce the operating cost and improve the energy efficiency.

Robustness analysis of the European air traffic network

The European air traffic network (ATN), consisting of a set of airports and area control centres, is highly complex. The current indicator of its performance, air traffic flow management delays, is insufficient for planning and management purposes. Topological analysis of ATNs of this kind has highlighted betweenness centrality (BC) as an indicator of network robustness, although such an indicator assumes no knowledge of actual traffic flows and the network's operational characteristics. This paper conducts topological and operational analyses of the European ATN in order to derive a more relevant and appropriate indicator of robustness. By applying a flow maximisation model to the network influenced by a range of capacity reductions at the local level, we propose a new index called the Relative Area Index (RAI). The RAI quantifies the importance of an individual node relevant to the performance of the entire network when it suffers from capacity reduction at a local scale. Air traffic data from three typical busy days in Europe are utilised to show that the RAI is more flexible and capable than BC in capturing the network impact of local capacity degradation. This index can be used to assess network robustness and provide a valuable tool for airspace managers and planners.

Survivability Analysis of Large-Scale Intelligent Transportation System Networks

A case study to assess the survivability of a large-scale urban intelligent transportation system (ITS) network is presented. The ITS for Boise, Idaho, was analyzed on the basis of two survivability assessment techniques, which are discussed and summarized. The first approach provides a qualitative assessment of the Boise ITS; it is based on the survivable systems analysis method as modified for critical infrastructure. The second approach provides a quantitative assessment of network survivability by using a multilayer graph-based approach consisting of the greater Boise area power grid and surface transportation system. The power grid and the physical and control transportation graphs were analyzed to determine the relative criticality of various network components. Macroscopic modeling was used to investigate the effect of components' failure on the network's operational characteristics. The greater Boise area has a population of more than half a million. The analysis presented here serves as a case study showing the means of assessing the importance of various components in critical infrastructure layers. The results have enabled traffic operators and decision makers in the Boise area to understand the effects of failure events and to prioritize threat mitigation alternatives.

Provision of a synchronising power characteristic on DFIG-based wind farms

The significant increase in wind penetration expected in the near future imposes the requirement that the bulk addition of wind farms to the network should not be detrimental to the overall network-operating characteristics. One way of ensuring this is to aim to provide a wind farm with a dynamic characteristic that is similar to that of a conventional synchronous-generator-based power station. A control strategy is presented that provides a DFIG-based wind farm with a power-response characteristic to network disturbances that dynamically resembles that of a synchronous generator. The DFIG controller is aimed at minimising the effect on network operation that the replacement of a conventional generator by a DFIG-based wind farm will have. A simple but realistic test network that combines synchronous and wind-farm generation has been modelled and used to assess dynamic performance. Simulation results are presented and discussed that demonstrate the capabilities of the new DFIG controller, although these are gained at the expense of losing some of the damping provided by conventional DFIG operation.

Strategic Service Network Design for DHL Hong Kong

We developed a two-phase network planning methodology to design a service network for DHL(HK) based on two measures of service performance: service coverage and service reliability. The methodology consists of first using an optimization model to determine a least-cost distribution network, which forms the basis of a simulation model for analyzing the network's operational characteristics. It takes into consideration such design issues as inbound and outbound shipment, equivalent shipment, cutoff time, demand fluctuation, and random behaviors. DHL decision makers can now examine trade-offs between coverage and reliability by adjusting workforce, changing cutoff time, or redesigning the service network.

Strategic Service Network Design for DHL Hong Kong

AboutSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked InEmail Go to Section HomeInterfacesVol. 31, No. 4 Strategic Service Network Design for DHL Hong KongWaiman Cheung, Lawrence C. Leung, Y. M. WongWaiman Cheung, Lawrence C. Leung, Y. M. WongPublished Online:1 Aug 2001https://doi.org/10.1287/inte.31.4.1.9663AbstractWe developed a two-phase network planning methodology to design a service network for DHL(HK) based on two measures of service performance: service coverage and service reliability. The methodology consists of first using an optimization model to determine a least-cost distribution network, which forms the basis of a simulation model for analyzing the network's operational characteristics. It takes into consideration such design issues as inbound and outbound shipment, equivalent shipment, cutoff time, demand fluctuation, and random behaviors. DHL decision makers can now examine trade-offs between coverage and reliability by adjusting workforce, changing cutoff time, or redesigning the service network. Back to Top Next FiguresReferencesRelatedInformationCited by“Make no little plans”: Impactful research to solve the next generation of transportation problems16 November 2020 | Networks, Vol. 77, No. 2Decomposition methods for large-scale network expansion problemsTransportation Research Part B: Methodological, Vol. 144Optimizing Long-Haul Transportation Considering Alternative Transportation Routes Within a Parcel Distribution Network28 November 2014CPEL Redesigns Its Land Express NetworkJianjun Zhang, Ou Tang, Jin Zhao, Jiazhen Huo, Yonggang Xia, 21 February 2013 | Interfaces, Vol. 43, No. 3A Genetic Algorithm Based Heuristic for the Design of Pick-up and Delivery Routes for Strategic Alliance in Express Delivery ServicesIFAC Proceedings Volumes, Vol. 46, No. 9LTL logistics networks with differentiated servicesComputers & Operations Research, Vol. 39, No. 11Compromised network design model for the strategic alliance of service centers and consolidation terminals in express courier servicesThe influence of value factors and pricing strategies on product development of computer peripheralsNetwork Design for Strategic Alliance in Express Courier ServicesProfit-Based Network Design in Express Courier ServicesDetermination of cutoff time for express courier services: a genetic algorithm approachInternational Transactions in Operational Research, Vol. 14, No. 2Retail consolidation in synchronized supply chainsZeitschrift für Betriebswirtschaft, Vol. 76, No. 2An intelligent decision support system for service network planningDecision Support Systems, Vol. 39, No. 3 Volume 31, Issue 4July-August 2001Pages 1-137 Article Information Metrics Information Published Online:August 01, 2001 © 2001 INFORMSCite asWaiman Cheung, Lawrence C. Leung, Y. M. Wong, (2001) Strategic Service Network Design for DHL Hong Kong. Interfaces 31(4):1-14. https://doi.org/10.1287/inte.31.4.1.9663 KeywordsINDUSTRIES—TRANSPORTATION—SHIPPINGFACILITIES—EQUIPMENT PLANNING—DESIGNPDF download

The Marketing Engineering Imperative: Introduction to the Special Issue

We developed a two-phase network planning methodology to design a service network for DHL(HK) based on two measures of service performance: service coverage and service reliability. The methodology consists of first using an optimization model to determine a least-cost distribution network, which forms the basis of a simulation model for analyzing the network's operational characteristics. It takes into consideration such design issues as inbound and outbound shipment, equivalent shipment, cutoff time, demand fluctuation, and random behaviors. DHL decision makers can now examine trade-offs between coverage and reliability by adjusting workforce, changing cutoff time, or redesigning the service network.

How antidepressants work: new perspectives on the pathophysiology of depressive disorder.

New research in animals is beginning to change radically our understanding of the biology of stress and the effects of antidepressant agents. To relate recent findings from the basic neurosciences to the pathophysiology of depressive disorder. Drawing together findings from molecular and physiological studies in rats, social studies in primates and neuropsychological studies in humans, we review the neurotrophic and neuroplastic effects of antidepressants and stress. Stress and antidepressants have reciprocal actions on neuronal growth and vulnerability (mediated by the expression of neurotrophins) and synaptic plasticity (mediated by excitatory amino acid neurotransmission) in the hippocampus and other brain structures. Stressors have the capacity to progressively disrupt both the activities of individual cells and the operating characteristics of networks of neurons throughout the life cycle, while antidepressant treatments act to reverse such injurious effects. We propose a central role for the regulation of synaptic connectivity in the pathophysiology of depressive disorder.

Electronic funds transfer networks: Modeling their impact on bank service goals

The purpose of this research is to illustrate how an EFTS decision support model can assist bankers. It demonstrates how such a model is constructed and applied to the simulation and evaluation of a proposed EFTS network design. Furthermore, it shows how the model is altered to reflect changes in the network's design and, thus, its performance. A simple case is used to do this. In addition, the paper describes: (1) the simulation technique; (2) the network components to be modeled; (3) the method of altering the network's operational characteristics; (4) the model's computer program; (5) validation of the model; and (6) the model's output statistics for measuring the network's performance.

Maintenance and Operating Characteristics of Communication Networks

The communication facilities of a communication network constitute a stochastic service system. To maintain such a network, an optimal distribution of the given manpower to stations is desirable, and this paper considers such a distribution under the assumption that the maintenance capability of an m-man team is mr (O ≦ r ≦ 1) times the maintenance capability of a single-man team. The method employed is the Lagrange multiplier, which, aided by charts, produces optimal numbers of service windows as well as numbers of men to be assigned. Finally, for known statistical maintenance data, the paper considers operating characteristics of the network such as average up time and down time, average number of renewals (ups or downs) in an interval [0, T], availability, restoration rate, failure rate of a connection, etc.

Fonctionnement et entretien des fossés d'assainissement dans le marais Charentais

The formation and structure of the Charente-Maritime marshes are described and the leading features of their drainage networks stated. This is followed by a brief analysis of the governing ditch design principles and network operating characteristics, especially those having a direct bearing on maintenance requirements, i.e. the following: (i) The importance of the tertiary ditch network as regards the regulating capacity of the network, in which the flow is tidal; (ii) The low flow velocities, which are conductive to weed growth; (iii) Water level variations due to the intermittent flow. The main ditch maintenance methods are then described, i.e. the following: 1. Chemical weed destruction. The most important weeds todestroy are listed, also produets in current use and the most frequent forms of treatment, i.e. treatment of the plants in situ above or under water, and sterilization. 2. Mechanical weeding. The main types of mechanical ditch-clearing equipment are briefly reviewed, including mechanical shovels, suction dredgers, helical clearers, etc. The author dwells at length on special equipment of the helical type made in Germany and prototypes of similar equipment produced in the Charente-Maritime region. The report closes with a few words on maintenance methods for wideditches, tidal ditches and small ditches, the common feature of which is that they aIl involve the use of chemical weed-killing techniques and mechanical maintenance equipment.