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 Mitigation Strategy For Dfigs During Variable Wind Conditions, Lasantha Meegahapola, Brendan Fox, Damian Flynn

Dr Lasantha G Meegahapola

This paper presents a flicker mitigation scheme for the doubly-fed induction generator (DFIG) during variable wind conditions. The flicker mitigation strategy was developed based on the distribution line X/R ratio and the active power deviation from the average active power during variable wind conditions. Flicker emission was analyzed using a flicker meter based on the IEC standards. Both short-term and long-term flicker severities were analyzed during the time period of study. The flicker mitigation strategy was evaluated under different system conditions such as X/R ratio, distribution line length, shortcircuit capacity (SCC), and wind variability. It is shown that the proposed …

Multi-Objective Reactive Power Support From Wind Farms For Network Performance Enhancement, Lasantha Meegahapola, Brendan Fox, Tim Littler, Damian Flynn

Dr Lasantha G Meegahapola

This paper examines the ability of the doubly fed induction generator (DFIG) to deliver multiple reactive power objectives during variable wind conditions. The reactive power requirement is decomposed based on various control objectives (e.g. power factor control, voltage control, loss minimisation, and flicker mitigation) defined around different time frames (i.e. seconds, minutes, and hourly), and the control reference is generated by aggregating the individual reactive power requirement for each control strategy. A novel coordinated controller is implemented for the rotor-side converter and the grid-side converter considering their capability curves and illustrating that it can effectively utilise the aggregated DFIG reactive …

Voltage Security Constrained Reactive Power Optimization Incorporating Wind Generation, L G. Meegahapola, E Vittal, A Keane, D Flynn

Dr Lasantha G Meegahapola

This paper presents a comparative analysis between conventional optimal power flow (OPF) and voltage constrained OPF strategies with wind generation. The study has been performed using the New England 39 bus system with 12 doublyfed induction generator (DFIG) based wind farms installed across the network. A voltage security assessment is carried out to determine the critical wind farms for voltage stability enhancement. The power losses and individual wind farm reactive power generation have been compared with and without voltage stability constraints imposed on the OPF simulation. It is shown that voltage constrained OPF leads to much greater active power losses …

Dynamic Characteristics Of A Hybrid Microgrid With Inverter And Non- Inverter Interfaced Renewable Energy Sources: A Case Study, A V. Jayawardena, L G. Meegahapola, S Perera, D A. Robinson

Dr Lasantha G Meegahapola

Microgrids are becoming important constituents of electric power distribution networks. Microgrids are typically comprised of both inverter interfaced (e.g. double-fed induction generator (DFIG), solar-photovoltaic (PV) system) and non-inverter interfaced (e.g. synchronous generator) renewable energy generators (REGs), hence their dynamic characteristics are significantly different from the conventional grids comprised of centralised synchronous generators. Different inherent characteristics of REGs, power dispatch levels, relative REG capacities, and external grid characteristics are some of the important features of significant interest in relation to microgrid dynamic behaviour. For this study a microgrid model was developed in DIgSILENT Power Factory based on the IEEE-13 bus system …

Capability Curve Based Enhanced Reactive Power Control Strategy For Stability Enhancement And Network Voltage Management, Lasantha Meegahapola, Tim Littler, Sarath Perera

Dr Lasantha G Meegahapola

Reactive power has become a vital resource in modern electricity networks due to increased penetration of distributed generation. This paper examines the extended reactive power capability of DFIGs to improve network stability and capability to manage network voltage profile during transient faults and dynamic operating conditions. A coordinated reactive power controller is designed by considering the reactive power capabilities of the rotor-side converter (RSC) and the grid-side converter (GSC) of the DFIG in order to maximise the reactive power support from DFIGs. The study has illustrated that, a significant reactive power contribution can be obtained from partially loaded DFIG wind …

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 …

Velocity Distribution In Non-Uniform/Unsteady Flows And The Validity Of Log Law, Ishraq Alfadhli, Shu-Qing Yang, Muttucumaru Sivakumar

Ishraq Hamdan Alfadhli

This study investigates the longitudinal velocity profiles in steady and unsteady non-uniform open channel flows by analyzing the data available in the literature. It was found that for steady/unsteady flow in the Log law is applicable only in the inner region where y/hg

Distribution Of Reynolds Shear Stress In Steady And Unsteady Flows, Ishraq Alfadhli, Shu-Qing Yang, Muttucumaru Sivakumar

Ishraq Hamdan Alfadhli

This study investigates the Reynolds shear stress distribution in steady and unsteady non-uniform flows. Specifically, it deals with how to express the deviation of this turbulence characteristic from that of uniform flow line; it is found that flow acceleration can well represent the deviation of Reynolds shear stress from its standard linear distribution. By connecting the flow acceleration with Reynolds shear stress, the study demonstrates empirically that the linear distrubiton of Reynolds shear stress can be observed when the flow acceleration is zero; the concave distribution of Reynolds shear stress can be observed when the flow acceleration is negative or …

Information Visualization For Learning Words In The Qur’An, Raja Jamilah Raja Yusof Dr

Raja Jamilah Raja Yusof Dr

Qur’an is a source of guidance to Muslims around the world. Although the language of the Qur’an is Arabic, many Muslims with different native languages attempt to learn the language to understand the message of the Qur’an. Qur’an contains many repeated words. Even though there are approximately 77 430 words in the Qur’an, there are only 5155 words used repeatedly or at least once to make up those words. This means that in theory for non-native Arabic speakers, these words can be added to their vocabulary to understand the literal meaning of the message of the Qur’an. In this paper, …

Organic Interfaces; Or, How Human Beings Augment Their Digital Devices, John Hunter

Faculty Journal Articles

It is a central premise of the advertising campaigns for nearly all digital communication devices that buying them augments the user: they give us a larger, better memory; make us more “creative” and “productive”; and/or empower us to access whatever information we desire from wherever we happen to be. This study is about how recent popular cinema represents the failure of these technological devices to inspire the enchantment that they once did and opens the question of what is causing this failure.

Using examples from the James Bond films, the essay analyzes the ways in which human users are frequently …

The Feasibility Study And Characterziation Of A Two-Dimensional Diode Array In “Magic Phantom” For High Dose Rate Brachytherapy Quality Assurance, A Espinoza, B Beeksma, M Petasecca, I Fuduli, C Porumb, D L. Cutajar, S Corde, M A. Jackson, M Lf Lerch, Anatoly B. Rosenfeld

Michael L.F. Lerch

High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly 192Ir with an air KERMA strength range between 20 000 and 40 000 U, where 1 U = 1 uGy m2/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the …

Skills Needs Of The Ict Sector In Tanzania, Deirdre Lillis, Fredrick Mtenzi, Diana Mauricaite, Said Jafari, Peter Manifold

Reports

Information and Communication Technology will play a critical role in sustaining the high growth rates experienced by African economies in the last decade. Investment in the ICT sector enables the creation of high quality jobs and acts as an enabling technology for other key industries such as agriculture, mining, finance, health and education. ‘New Software Economy’ models mean international location and company scale are less relevant and enable small organisations to compete globally in niche markets. Unlike many traditional industries which have heavy infrastructure requirements, the key resource of the ICT Sector is its people and the knowledge, skills and …

Shear Lag And Eccentricity Effects Of Bolted Connections In Cold-Formed Steel Sections, Lip H. Teh, Veysel Yazici

Veysel Yazici

This paper examines the "three factors" approach previously presented by the senior author for determining the net section efficiency of a bolted cold-formed steel open profile. One objective is to ascertain that the net section efficiency is governed by three factors: the in-plane shear lag associated with stress concentration around a bolt hole that is also present in a flat sheet, the out-of-plane shear lag that is also present in a bi-symmetric I-section bolted at the flanges only, and the bending moment arising from the connection eccentricity with respect to the neutral axis. This paper presents the test results of …

Unconventional Block Shear Failures Of Bolted Connections In Cold-Reduced Steel Sheets, Lip H. Teh, Veysel Yazici

Veysel Yazici

This paper examines the block shear design equation proposed by the first author based on laboratory tests of bolted connection specimens failing in the conventional block shear failure mode. It shows that the explanation regarding the feasible mechanism of block shear failures previously provided by the first author does not necessarily apply to staggered bolted connections, in which the downstream bolts do not have the same edge distance. For staggered bolted connections, a block shear failure may occur through the shear rupture and tensile yielding mechanism for particular configurations, as demonstrated for the first time in this paper. The present …

Patent Value And Citations: Creative Destruction Or Strategic Disruption?, David S. Abrams, Ufuk Akcigit, Jillian Popadak

All Faculty Scholarship

Prior work suggests that more valuable patents are cited more and this view has become standard in the empirical innovation literature. Using an NPE-derived dataset with patent-specific revenues we find that the relationship of citations to value in fact forms an inverted-U, with fewer citations at the high end of value than in the middle. Since the value of patents is concentrated in those at the high end, this is a challenge to both the empirical literature and the intuition behind it. We attempt to explain this relationship with a simple model of innovation, allowing for both productive and strategic …

Semi-Finite Noncommutative Geometry And Some Applications, Alan L. Carey, Adam C. Rennie, John Phillips

Associate Professor Adam Rennie

These notes are a summary of talks given in Shonan, Japan in February 2008 with modifications from a later series of talks at the Hausdorff Institute for Mathematics in Bonn in July 2008 and at the Erwin Schr¨odinger Institute in October 2008. The intention is to give a short discussion of recent results in noncommutative geometry (NCG) where one extends the usual point of view of [22] by replacing the bounded operators B(H) on a Hilbert space H by certain sub-algebras; namely semi-finite von Neumann algebras. These are weakly closed subalgebras of the bounded operators on a Hilbert space that …

Simplifying Inventive Standards (Part-5), Umakant Mishra

Umakant Mishra

As the “inventive standards” are really complicated, Generich Altshuller and other creators of “inventive standards” created a set of standards (grouped under class-5) to help using the standards. There are totally 17 standards in class-5. This article will try to simplify all these 17 standards under class-5.

While writing these articles the author realized that although the grouping and ordering of the 76 standards don’t appear to be systematic there is no easy method of regrouping or reorganizing the standards. The author tried regrouping and reordering the standards in various different ways but nothing really came out satisfactory. Much more …

Simplifying Inventive Standards (Part-3), Umakant Mishra

Umakant Mishra

According to TRIZ most problems are “standard” problems. The standard problems are those which are known to have occurred many times in many places. Besides these problems have been solved by different people in different places (may be in different contexts) at different times. As there are many known solutions to such problems it is possible to abstract the rules of solution from the group of individual solutions. TRIZ provides a set of 76 rules to solve such standard problems.

Although “Inventive Standards” (or standard solutions) is one of the most powerful techniques of TRIZ it is hardly used by …

Simplifying Inventive Standards (Part-4), Umakant Mishra

Umakant Mishra

Although “Inventive Standards” (or standard solutions) is one of the most powerful techniques of TRIZ it is hardly used by any TRIZ practitioner because of its complexity. The objective of this series of articles is to explain the rules in simple language. In this article we will discuss all the solutions in class-4. There are 17 solutions in class-4 all of which deal with the problems relating to measurement and detection. For example some objects may be extremely large (e.g. earth) or extremely small (e.g., atoms) and cannot be easily measured. Some items like germs and viruses are not visible …

The Killer Idea: How Some Gunslinging Anarchists Held Freedom Of Speech At Gunpoint, Gert A. Van Vugt Msc

Gert A van Vugt MSc

In May 2013, the first all-plastic, 3D printed gun was fired. This paper offers a detailed description of the origins and development of the printable gun. It elucidates the transformation of the principal narrative in the increasing media coverage from circumventing arms regulation to defending free speech, highlighting the role of Defense Distributed and their strategic framing of the printable gun. Finally, the uptake of the latter narrative by early popular and scholarly contributions is discussed. The paper highlights the political impact of narrative formation in debates about regulating 3D printing and the communication of printable designs, and suggests an …

Automatic Domain Identification For Linked Open Data, Sarasi Lalithsena, Pascal Hitzler, Amit P. Sheth, Prateek Jain

Kno.e.sis Publications

Linked Open Data (LOD) has emerged as one of the largest collections of interlinked structured datasets on the Web. Although the adoption of such datasets for applications is increasing, identifying relevant datasets for a specific task or topic is still challenging. As an initial step to make such identification easier, we provide an approach to automatically identify the topic domains of given datasets. Our method utilizes existing knowledge sources, more specifically Freebase, and we present an evaluation which validates the topic domains we can identify with our system. Furthermore, we evaluate the effectiveness of identified topic domains for the purpose …

Semantics-Empowered Big Data Processing With Applications, Krishnaprasad Thirunarayan, Amit P. Sheth

Kno.e.sis Publications

We discuss the nature of Big Data and address the role of semantics in analyzing and processing Big Data that arises in the context of Physical-Cyber-Social Systems. We organize our research around the Five Vs of Big Data, where four of the Vs are harnessed to produce the fifth V - value. To handle the challenge of Volume, we advocate semantic perception that can convert low-level observational data to higher-level abstractions more suitable for decision-making. To handle the challenge of Variety, we resort to the use of semantic models and annotations of data so that much of the intelligent processing …

Effects Of Feed And Draw Solution Temperature And Transmembrane Temperature Difference On The Rejection Of Trace Organic Contaminants By Forward Osmosis, Ming Xie, William E. Price, Long D. Nghiem, Menachem Elimelech

William E. Price

The effects of feed and draw solution temperature and transmembrane temperature difference on the rejection of 12 trace organic contaminants (TrOCs) by two forward osmosis (FO) membranes were investigated. The membrane structure parameter (S) and the reverse salt (NaCl) flux selectivity (RSFS) were constant over the temperature range of 20-40 1C, suggesting that within this range, the solution temperature did not significantly influence the membrane polymeric structure. Draw solution properties, including diffusivity, viscosity, and osmotic pressure, played an important role in water and reverse salt (NaCl) flux behaviour and TrOC rejection. Pure water and salt (NaCl) permeability coefficients of the …

Coupling Granular Activated Carbon Adsorption With Membrane Bioreactor Treatment For Trace Organic Contaminant Removal: Breakthrough Behaviour Of Persistent And Hydrophilic Compounds, Luong N. Nguyen, Faisal I. Hai, William E. Price, Jinguo Kang, Long D. Nghiem

William E. Price

This study investigated the removal of trace organic contaminants by a combined membrane bioreactor - granular activated carbon (MBR-GAC) system over a period of 196 days. Of the 22 compounds investigated here, all six hydrophilic compounds with electron-withdrawing functional groups (i.e., metronidazole, carbamazepine, ketoprofen, naproxen, fenoprop and diclofenac) exhibited very low removal efficiency by MBR-only treatment. GAC post-treatment initially complemented MBR treatment very well; however, a compound-specific gradual deterioration of the removal of the above-mentioned problematic compounds was noted. While a 20% breakthrough of all four negatively charged compounds namely ketoprofen, naproxen, fenoprop and diclofenac occurred within 1000-3000 bed volumes …

Impact Of Chemical Cleaning On The Nanofiltration Of Pharmaceutically Active Compounds (Phacs): The Role Of Cleaning Temperature, Alexander Simon, William E. Price, Long D. Nghiem

William E. Price

This study investigated the impact of chemical cleaning on the physicochemical properties of a nanofiltration membrane and its subsequent separation efficiency of inorganic salts and two pharmaceutically active compounds (PhACs), sulfamethoxazole and carbamazepine. Chemical cleaning was simulated by immersing virgin membrane samples in aqueous citric acid, sodium hydroxide (NaOH), ethylenediaminetetraacetic-acid (EDTA) and sodium dodecyl sulphate (SDS) at various temperatures for 18 h. The cleaning temperature did not exert any discernible impact on the surface charge of the NF270 membrane selected in this study. However, high cleaning temperatures were shown to either amplify or reduce the impact of chemical cleaning on …

Predicting The Fate Of Emerging Trace Organic Contaminants Of Concern During Mbr Treatment Based On Their Molecular Properties, K C. Wijekoon, L D. Nghiem, F I. Hai, J Kang, W E. Price

William E. Price

We demonstrate that the fate of emerging trace organic contaminants during membrane bioreactor (MBR) treatment can be qualitatively predicted by assessing their molecular properties. This work futher expands the qualitative framework for the prdiction of trace organic removal by MBR treatment reported in our recent study.