Science and Technology Studies Commons^™

Optimization Of Frt Active Power Performance Of A Dfig During Transient Grid Faults, L Meegahapola, Damian Flynn, Tim Littler

Dr Lasantha G Meegahapola

Optimal fault ride-through (FRT) conditions for a doubly-fed induction generator (DFIG) during a transient grid fault are analyzed with special emphasis on improving the active power generation profile. The transition states due to crowbar activation during transient faults are investigated to exploit the maximum power during the fault and post-fault period. It has been identified that operating slip, severity of fault and crowbar resistance have a direct impact on the power capability of a DFIG, and crowbar resistance can be chosen to optimize the power capability. It has been further shown that an extended crowbar period can deliver enhanced inertial …

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 …

Buried Deep: How Data About Subseafloor Life Becomes Dark And Why, Peter Darch, Rebekah Cummings

Peter Darch

Earth scientists increasingly work in distributed, multidisciplinary projects. To promote the sharing of data across such a project, it is vital to improve long-term preservation of data in formats accessible to scientists in multiple disciplines with diverse needs, tools and scientific practices. When developing data management plans and infrastructure, it is important to ask: - What data are generated? - Where are these data preserved and shared? - What are the processes by which these data become 'dark'? - What are the infrastructural and social factors that shape these processes? In response to these questions, we present findings from the …

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 …

Does The Critical Shields Stress For Sediment Transport Depend On Channel-Bed Slope?, Ishraq Alfadhli, Shu-Qing Yang, Muttucumaru Sivakumar

Ishraq Hamdan Alfadhli

This paper investigates why the observed critical Shields stress for incipient sediment motion deviates from the Shields curve. This deviation is often described in the literature as due to measurement errors and non-uniformity of channel-bed slope or flows. On the contrary, this paper hypothesises the deviation as due to the presence of vertical velocity in open channel flows. We found that the existence of vertical velocity in non-uniform flows can lead to the deviation of critical shear stress from the standard Shield's diagram that is valid only in uniform flows, and the channel bed slope could not contribute to the …

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 …

A Real-Time In Vivo Dosimetric Verification Method For High-Dose Rate Intracavitary Brachytherapy Of Nasopharyngeal Carcinoma, Zhen-Yu Qi, Xiao-Wu Deng, X Cao, Shao-Min Huang, Michael Lerch, Anatoly Rosenfeld

Michael L.F. Lerch

Purpose: A real-time in vivo dosimetric verification method using metal-oxide-semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high-dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). Methods: The necessary calibration and correction factors for MOSFET measurements in 192Iridium source were determined in a water phantom. With the detector placed inside a custom-made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. Results: Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 ± 0.007 cGymV. …

Performance Comparison Of Two Compact Multiplexed Readouts With Sensl's Spmarray4 For High-Resolution Detector Module, Yujin Qi, Xiaohui Zhang, Cuilan Zhao, Lihong Chen, Marco Petasecca, Mitra Safavi-Naeini, Michael Lerch, Anatoly Rosenfeld

Michael L.F. Lerch

The purpose of this study was to investigate a compact readout for silicon photomultiplier (SiPM) array in the development of high-resolution imaging detector to reduce the readout channels while maximizing the detectors performance. The detector module was composed of a LYSO scintillation crystal array and a SensL's SPMArray4. The crystal array was coupled to the SiPM array with a 2mm-thick silicone pad to improve the light sharing among the SiPM array elements. Three LYSO crystal arrays of 4x4, 8x8 and 12x12 crystal elements with pixel sizes of 3.2, 1.6 and 1.0 mm were investigated in this study. Two compact multiplexed …

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 …

The Local Index Formula In Noncommutative Geometry Revisited, Alan Carey, John Phillips, Adam Rennie, Fyodor Sukochev

Associate Professor Adam Rennie

In this review we discuss the local index formula in noncommutative geomety from the viewpoint of two new proofs are partly inspired by the approach of Higson especially that in but they differ in several fundamental aspedcts, in particular they apply to semifinite spectral triples for a *s-subalgebra A of a general semifinite von Neumann algebra. Our proofs are novel even in the setting of the original theorem and reduce the hypotheses of the theorem to those necessary for its statement. These proofs rely on the introduction of a function valued cocycle which is 'almost' a (b, B)-cocycle in the …

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 …