Social and Behavioral Sciences Commons^™

Impact Of Wind Generator Control Strategies On Flicker Emission In Distribution Networks, Lasantha Meegahapola, Sarath Perera

Dr Lasantha G Meegahapola

Renewable power generators are increasingly being integrated to electricity networks to achieve future renewable energy targets in power generation. In particular, wind power generation has already reported substantial penetration levels in electricity networks. Traditionally, flicker phenomenon is considered to be one of the power quality issues in power distribution networks due to fluctuating consumer loads connected to the network. Large-scale integration of wind power generators may create significant voltage fluctuations in distribution feeders due to stochastic and intermittent nature of the wind resources. This study aims to investigate and characterize the flicker emission under different control strategies for DFIG based …

Characterisation Of Flicker Emission And Propagation In Distribution Networks With Bi-Directional Power Flows, D Perera, L Meegahapola, S Perera, P Ciufo

Dr Lasantha G Meegahapola

With the increasing penetration levels of intermittent and fluctuating energy sources such as wind generating systems in the electricity grid, resulting voltage fluctuations and flicker can be expected to become an important power quality considerations. Due to significant bidirectional power flows resulting from large renewable power generation systems connected to downstream, voltage fluctuations may propagate from downstream to upstream. The work presented in this paper investigates and characterises flicker emission and propagation resulting from fluctuating generating sources connected to a distribution network. Mathematical models are developed for flicker emission under different generator control strategies and flicker propagation to upstream network. …

Comparative Analysis Of Dynamic Line Rating Models And Feasibility To Minimise Energy Losses In Wind Rich Power Networks, Mathew Simms, Lasantha Meegahapola

Dr Lasantha G Meegahapola

Wind power generation has indicated an exponential increase during last two decades and existing transmission network infrastructure is increasingly becoming inadequate to transmit remotely generated wind power to load centres in the network. The dynamic line rating (DLR) is one of the viable solutions to improve the transmission line ampacity during high wind penetration without investing on an additional transmission network. The main objective of this study is to identify the basic differences between two main line rating standards, since transmission network service providers (TNSPs) heavily depend on these two standards when developing their line rating models. Therefore, a parameter …

Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo

Dr Lasantha G Meegahapola

Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …

Large Networks Of Vertical Multi-Layer Graphenes With Morphology-Tunable Magnetoresistance, Zengji Yue, Igor Levchenko, Shailesh Kumar, Donghan Seo, Xiaolin Wang, S X. Dou, Kostya Ken Ostrikov

Zengji Yue

We report on the comparative study of magnetotransport properties of large-area vertical few-layer graphene networks with different morphologies, measured in a strong (up to 10 T) magnetic field over a wide temperature range. The petal-like and tree-like graphene networks grown by a plasma enhanced CVD process on a thin (500 nm) silicon oxide layer supported by a silicon wafer demonstrate a significant difference in the resistance-magnetic field dependencies at temperatures ranging from 2 to 200 K. This behaviour is explained in terms of the effect of electron scattering at ultra-long reactive edges and ultra-dense boundaries of the graphene nanowalls. Our …

Connected: To Everyone And Everything, Katherine Albrecht, Katina Michael

Associate Professor Katina Michael

The activist group CASPIAN (Consumers Against Supermarket Privacy Invasion and Numbering) was founded in 1999 by Katherine Albrecht, the very same year that Kevin Ashton co-founder and executive director of the then Auto-ID Center at MIT made a presentation to Proctor & Gamble with a title that included the phrase “Internet of Things”. According to Ashton, “the most numerous and important routers of all” are people but people have limitations and are not very good at capturing data about objects in the physical world. In 2001, Ashton’s automatic identification vision had become a lot clearer. At the Auto-ID Center during …

A Multiagent Approach For Decentralized Voltage Regulation In Power Distribution Networks Within Dgs, Fenghui Ren, Minjie Zhang, Danny Sutanto

Dr Fenghui Ren

Voltage regulation (VR) is a procedure to keep voltages in a distribution network (DN) within normal limits. Conven- tionally, a voltage regulator can read voltage levels from pre- dened measures, and regulate the voltages. However, due to lacking of a distributed generator's (DG) information, the unexpected electricity from a DG will mislead readings on voltages levels, so as to disturb the VR in a DN. Adjust- ing a DG's reactive power output is an alternative way for VR. However, because of limited penetration levels, DGs need to collaborate with other devices in order to provide an eective voltage regulation. Therefore, …

Securing Dsr Against Wormhole Attacks In Multirate Ad Hoc Networks, Shams Qazi, Raad Raad, Yi Mu, Willy Susilo

Dr Raad Raad

A wormhole attack is one of the hardest problems to detect whereas it can be easily implanted in any type of wireless ad hoc network. A wormhole attack can easily be launched by the attacker without having knowledge of the network or compromising any legitimate nodes. Most existing solutions either require special hardware devices or make strong assumptions in order to detect wormhole attacks which limit the usability of these solutions. In this paper, we present a security enhancement to dynamic source routing (DSR) protocol against wormhole attacks for ad hoc networks which relies on calculation of round trip time …

Playing In The Sandbox: Using Mixed Methods And Social Network To Examine Interorganizational Relationships Between Nonprofit Housing Organizations In The Richmond Metropolitan Area, Tamarah Holmes

Theses and Dissertations

Nonprofit housing organizations primarily exist to address the housing needs of low-income residents, whose housing needs are not sufficiently met by the public or private housing market. NHOs are very similar to private corporations in their size, productivity and commitment to the “bottom line.” However, unlike private firms, NHOs are “mission driven” instead profit-driven corporations. The development of affordable housing in the nonprofit housing sector requires a myriad of financial and non-financial resources. As competition for financial resources intensifies many organizations are adopting strategies as a means to not only reduce organizational uncertainty and sustain them, but also increase or …

Collaborative Preference: The Role Of Homophily, Multiplexity, And Advantageous Network Position Across Small And Medium-Sized Organizations, Troy A. Voelker, William C. Mcdowell, Michael L. Harris

Administrative Issues Journal

The purpose of this paper is to examine collaboration between individuals across organizations. While both for profit and not-for-profit organizations utilize collaborative efforts, the factors that are important for bringing individuals and businesses together for collaboration still remain somewhat unresolved. In this paper, colleague similarity, the quality of pre-existing relationships, and the relative power of the other colleague are all examined for their correlation with the desirability of collaboration with that individual. In a study of pastors of small and medium sized churches in a southwestern protestant conference, we examined these areas through the lenses of homophily theory, multiplicity theories, …

Location, Location, Location: The Importance Of Proximity In Student Peer Evaluation, Roger White

Economics

The appropriateness of physical distances as a proxy for interpersonal networks is examined using data on peer evaluation scores collected from undergraduate student presentations in econometrics courses during the spring 2010 and spring 2011 semesters at Franklin & Marshall College. Employing the Tobit regression technique and decomposing the resulting coefficient estimates into marginal effects, we find that greater physical distance is negatively related to peer evaluation scores in the sense that greater distance lowers scores and reduces the likelihood that the evaluating student will assign the maximum possible score. Similarly, evaluating students assign higher scores to those student presenters they …

Diffusion Of Innovation Across A National Local Health Department Network: A Simulation Approach To Policy Development Using Agent-Based Modeling, Mark Orr, Jacqueline Merrill

Frontiers in Public Health Services and Systems Research

The network that local health officials use to communicate about professional issues is sparsely connected, which may limit the spread of innovative practices. We used agent-based simulation modeling to find out if a policy to promote more connections improved the network’s capability to diffuse innovation. We found that unanticipated effects could result, depending on the requirements of the policy and the proportion of health officials involved. With carefully crafted assumptions and reliable data it is possible to untangle complex processes using simulation modeling. The results represent how the world might actually work which may provide useful decision support for policymakers …

Private Debt Syndicates: Governance, Networks, And Syndicate Structure, William R. Mccumber

Graduate Theses and Dissertations

I examine the primary market for syndicated private credit agreements to U.S. firms within the context of contract theory with information asymmetries between contracting parties in a repeated game. Specific governance mechanisms determine a firm's cost of borrowing in syndicated credit agreements. Firms with governance mitigating agency risk between stakeholders, i.e. independent boards, strong shareholder monitoring, and greater CEO pay-performance sensitivity, enjoy lower borrowing costs. The interests of creditors and shareholders diverge with regard to external governance. Lenders charge higher spreads to firms at greater risk of acquisition and reward stronger firms with price concessions when they possess staunch anti-takeover …

Essays In Economic Growth And Development, Zhen Zhu

Graduate Theses and Dissertations

This dissertation consists of three chapters exploring the Solow Residual of the Solow growth model. Two central components of the Solow Residual have been studied in my doctoral dissertation. The first is the structural transformation, an internal adjustment process that helps the economy attain the optimal points on its Production Possibility Frontier by reallocating resources from the low-productivity sectors to the high-productivity sectors. The second is the technology diffusion, a positive externality process that pushes forward the economy's Production Possibility Frontier if it adopts the newer technology.

The first chapter of my dissertation is devoted to a case study of …

Congolese Cultural Landscapes, Transnational Networks, And Identity Formation In Milwaukee, Claire Marie Reuning

Theses and Dissertations

Following national trends, between 2000 and 2010, the city of Milwaukee's foreign-born African population doubled. Previous research attributes this population growth to various socio-economic and political factors on the African continent, the United State's implementation of the Diversity Visa Lottery (DVL) program, and perceived economic opportunities. Applying a mixed methods approach, I analyze the spatial distribution of foreign-born Africans in Milwaukee County to contextualize a case study of people from the Democratic Republic of the Congo (DRC) worshipping at Milwaukee's International Lutheran Church of Zion (Zion Church). Using information gathered from participant observation, semi-structured interviews, census and demographic data, I …

Elements Of Cohesion: The Role Of Business Improvement Districts In Neighborhood Cohesion, Bo Scarim

Psychology Honors Projects

The current research examines the relationship between sense of community and business improvement districts (BIDs) in urban neighborhoods. Study 1 employed the method of imagined scenarios to distinguish sense of community ratings between hypothetical neighborhoods with and without BIDs. This study found that participants in the imagined BID neighborhood scenario reported higher sense of community than those in the imagined non-BID neighborhood scenario. In Study 2, residents of two neighborhoods in Brooklyn, New York, one with a BID and one without a BID, were surveyed on their neighborhood experience and sense of community. This study found no difference in sense …

Banking Records, Business And Networks In Colonial Sydney, 1817-24, Leanne Johns, Simon Ville

Simon Ville

Examining accounting transactions between depositors in the first accounts ledger of the Bank of New South Wales contributes to our knowledge of early Australian colonial businesspeople and their business activities. A social network analysis framework is applied to the transactions to disclose business networks and prominent individuals in the networks. The analysis seeks to ascertain the importance of these people to commerce and the significance of their networks in facilitating commercial relationships in a business environment fraught with uncertainty. The results illustrate the importance of networks to colonial trade and mercantile activity, especially for smaller scale businesspeople.aehr_348

Comparison Of Methodologies For Assessment Of Harmonic Current Emission Limits For Large Installations Connected To Lv Networks, Biyanvilage Perera, Sarath Perera, Philip Ciufo, Victor J. Gosbell

Dr Philip Ciufo

With the proliferation of large, disturbing installations (loads and distribution generators) connected to public low voltage networks, managing the harmonic voltage levels in the network has become a key concern to distribution network service providers (DNSPs). Therefore, it is important that DNSPs limit the harmonic current emission by individual installations. This paper reviews a number of methodologies that exist in the current technical literature in relation to the assessment of harmonic current emission limits for disturbing installations connected to the public LV network. Application of these methodologies is demonstrated through a case study on a test network. The study shows …

Flicker Propagation Analysis In Distribution Networks With Embedded Generation, D Perera, L Meegahapola, S Perera, P Ciufo

Dr Philip Ciufo

Embedded generators such as wind generators can produce observable voltage fluctuations during variable wind conditions hence flicker. The flicker produced by such intermittent and fluctuating generating sources can propagate to other parts of the distribution network while creating power quality issues in distribution feeders. This study presents a flicker emission analysis for a doubly-fed induction generator (DFIG) based wind farm and investigate the pertinent factors which influence flicker propagation and attenuation in distribution feeders. Study has shown that voltage fluctuations are significantly influenced by the attenuation characteristics of various load types (i.e. constant power, impedance and current loads) connected to …

The Coevolution Of Networks And Political Attitudes, David Lazer, Brian Rubineau, Carol Chetkovich, Nancy Katz, Michael Neblo

Brian Rubineau

How do attitudes and social affiliations co-evolve? A long stream of research has focused on the relationship between attitudes and social affiliations. However, in most of this research the causal relationship between views and affiliations is difficult to discern definitively: Do people influence each other’s views so that they converge over time or do they primarily affiliate (by choice or happenstance) with those of similar views? Here we use longitudinal attitudinal and whole network data collected at critical times (notably, at the inception of the system) to identify robustly the determinants of attitudes and affiliations. We find significant conformity tendencies: …

Examining Multi-Level And Inter-Organizational Collaborative Response To Disasters: The Case Of Pakistan Floods In 2010, Sana Khosa

Electronic Theses and Dissertations

Catastrophic disasters are different than routine disasters and managing them requires the mobilization of inter-organizational, inter-governmental, cross-sectoral and international humanitarian support. The role of the international community through International Nongovernmental Organizations (INGOs), and multi-lateral organizations such as the United Nations (UN) becomes imperative when the scale of the disaster is unprecedented and difficult for a country to manage on its own. The initial response and relief phase of managing disasters is one in which many agencies with different expertise, capacities, working mandates, resources, skills, working cultures and norms come together to coordinate and collaborate to provide timely response and relief …

Factors That Contribute To Effectiveness Of Foster Care Networks In Securing Permanency For Children: An Exploration Of Network Participants' Perceptions In Urban And Rural Settings, Reza M. Khoramshahi

ETD Archive

The purpose of this study was to identify possible factors that may contribute to the variations in effectiveness of foster care networks in a rural and an urban Ohio county. The effectiveness of the networks was assessed based on the success of the foster care networks to provide permanency for children who are placed in out-of-home care. For the purpose of this study the foster care network organizations in each county included the child welfare agencies, the juvenile courts, private foster care agencies and foster families. The child welfare agencies in each of Ohio counties operate independently, and their success …

The Added Value Of Understanding Informal Social Networks In An Adaptive Capacity Assessment: Explorations Of An Urban Water Management System In Indonesia, Silva Larson, Kim S. Alexander, Riyanti Djalante, Dewi G.C Kirono

Faculty of Science, Medicine and Health - Papers: part A

Social networks play an important role in environmental governance regimes, and they are a key to the adaptive capacity of systems that deal with complex, contextual and multi-faceted issues. Urban water systems are typical examples of complex systems facing many pressures, such as increased population, water quality deterioration, and climate change. This paper explores social networks of the key stakeholders engaged in urban water management, in Makassar City, Indonesia, in the context of exploring ways to improve management of an increasingly complex urban water system. Three social networks were explored; those constituted by formal and informal interactions and networks perceived …

A Model Of The Effects Of Authority On Consensus Formation In Adaptive Networks: Impact On Network Topology And Robustness, Brenton J. Prettejohn, Matthew J. Berryman, Mark D. Mcdonnell

Faculty of Engineering and Information Sciences - Papers: Part A

Opinions of individuals in real social networks are arguably strongly influenced by external determinants, such as the opinions of those perceived to have the highest levels of authority. In order to model this, we have extended an existing model of consensus formation in an adaptive network by the introduction of a parameter representing each agent's level of 'authority' based on their opinion relative to the overall opinion distribution. We found that introducing this model, along with a randomly varying opinion convergence factor, significantly impacts the final state of converged opinions and the number of interactions required to reach that state. …

A Multiagent Approach For Decentralized Voltage Regulation In Power Distribution Networks Within Dgs, Fenghui Ren, Minjie Zhang, Danny Sutanto

Faculty of Engineering and Information Sciences - Papers: Part A

Voltage regulation (VR) is a procedure to keep voltages in a distribution network (DN) within normal limits. Conven- tionally, a voltage regulator can read voltage levels from pre- dened measures, and regulate the voltages. However, due to lacking of a distributed generator's (DG) information, the unexpected electricity from a DG will mislead readings on voltages levels, so as to disturb the VR in a DN. Adjust- ing a DG's reactive power output is an alternative way for VR. However, because of limited penetration levels, DGs need to collaborate with other devices in order to provide an eective voltage regulation. Therefore, …

A Sax-Based Advanced Computational Tool For Assessment Of Clustered Rooftop Solar Pv Impacts On Lv And Mv Networks In Smart Grid, M J. E Alam, K M. Muttaqi, D Sutanto

Faculty of Engineering and Information Sciences - Papers: Part A

Future distribution networks with increasing level of solar PV penetration will be managed using smart grid technologies capable of producing appropriate and timely response during normal and abnormal operational events. Distribution feeder loads vary throughout the day according to the trend of consumption of the customers. Solar PV outputs fluctuate in proportion to irradiance level of sun. Simultaneous occurrence of both of these variations would result in various operating conditions that may lead to unexpected events, and would require a large amount of network data to be processed and analyzed for decision making. It is envisaged that such data will …

Security Analysis Of A Single Sign-On Mechanism For Distributed Computer Networks, Guilin Wang, Jiangshan Yu, Qi Xie

Faculty of Engineering and Information Sciences - Papers: Part A

Single sign-on (SSO) is a new authentication mechanism that enables a legal user with a single credential to be authenticated by multiple service providers in a distributed computer network. Recently, Chang and Lee proposed a new SSO scheme and claimed its security by providing well-organized security arguments. In this paper, however, we demonstrative that their scheme is actually insecure as it fails to meet credential privacy and soundness of authentication. Specifically, we present two impersonation attacks. The first attack allows a malicious service provider, who has successfully communicated with a legal user twice, to recover the user's credential and then …

A Three-Phase Power Flow Approach For Integrated 3-Wire Mv And 4-Wire Multigrounded Lv Networks With Rooftop Solar Pv, Md J E Alam, K M. Muttaqi, Darmawan Sutanto

Faculty of Engineering and Information Sciences - Papers: Part A

With increasing level of rooftop solar photovoltaic (PV) penetration into low voltage (LV) distribution networks, analysis with realistic network models is necessary for adequate capturing of network behavior. Traditional three-phase 3-wire power flow approach lacks the capability of exact analysis of 4-wire multigrounded LV networks due to the approximation of merging the neutral wire admittance into the phase wire admittances. Such an approximation may not be desirable when neutral wire and grounding effects need to be assessed, especially in the presence of single-phase solar power injection that may cause a significant level of network unbalance. This paper proposes a three-phase …

Efficiency And Equity Of Speed Limits In Transportation Networks, Shuaian Wang

Faculty of Engineering and Information Sciences - Papers: Part A

This paper examines the impact of speed limits on network efficiency, in terms of total travel time of all road users, and equity among road users from different origin-destination (OD) pairs, in terms of the change of travel time after imposing a speed limit scheme. We find that after imposing a speed limit scheme, the total travel time of all road users may decrease or increase; road users of some OD pairs may experience longer travel time, while other OD pairs may have shorter travel time. In view of the importance of speed limits on network efficiency and equity, we …

Approximation Algorithm For Data Broadcasting In Duty Cycled Multi-Hop Wireless Networks, Dianbo Zhao, Kwan-Wu Chin

Faculty of Engineering and Information Sciences - Papers: Part A

Broadcast is a fundamental operation in wireless networks. To this end, many past studies have studied the NP-hard, broadcast problem for always-on multi-hop networks. However, in wireless sensor networks, nodes are powered by batteries, meaning, they have finite energy. Consequently, nodes are required to have a low duty cycle, whereby they switch between active and sleep state periodically. This means that a transmission from a node may not reach all of its neighbors simultaneously. Consequently, any developed broadcast protocols must consider collisions and the wake-up times of neighboring nodes. Henceforth, this paper studies the minimum latency broadcast scheduling problem in …