Research_Online@UCD

Dielectric charge control in electrostatic MEMS positioners / varactors

Mon, 06 Feb 2012 01:00:00 GMT

Author: Blokhina, Elena; Lopez, David; Gorreta, Sergi; Molinero, David; Feely, Orla; Pons Nin, Joan; Dominguez, Manuel

Abstract: A new dynamical closed-loop method is proposed to control dielectric charging in capacitive MEMS positioners/ varactors for enhanced reliability and robustness. Instead of adjusting the magnitude of the control voltage to compensate the drift caused by the dielectric charge, the method uses a feedback loop to maintain it at a desired level: the device capacitance is periodically sampled and bipolar pulses of constant magnitude are applied. Specific models describing the dynamics of charge and a control map are introduced. Validation of the proposed method is accomplished both through discrete-time simulations and with experiments using MEMS devices that suffer from dielectric charging.

Charge resolved electrostatic diagnostic of colliding copper laser plasma plumes

Sat, 01 Jan 2011 01:00:00 GMT

Author: Yeates, P; Fallon, Conor; Kennedy, E.T.; Costello, John T.

Abstract: The collision of two laser generated plasma plumes can result, under appropriate conditions, in the formation of ‘stagnation layer’. The processes underlying this phenomenon are complex and time dependent. The majority of experiments over the last few decades have focused upon spectroscopic diagnostic of colliding plasmas. We have performed electrostatic diagnosis of multiply charged copper ions (Cu+ to Cu5+) generated via Q-switched pulsed laser (λ=1.06 μm, τ=6 ns, EL=52-525 mJ) generation of copper plasma plumes from a planar target. Time dependent current traces, charge yields and kinetic energy (Ke) distributions are obtained for single plasma plumes (Sp) and colliding plasma plumes (Cp). The charge yield from a Cp relative to twice that from a Sp is characterized by a charge yield ratio (CYR) parameter. Superior ion yields for all charge states occur for a discrete range of fluences (F) from colliding plasma plumes leading to a CYR parameter exceeding unity. The kinetic energy distributions from colliding plasma plumes display well defined energy compression via narrowing of the distributions for all fluences and charge states. The extent of this energy compression is charge dependent. Space charge forces within the stagnation layer and the resulting charge dependent acceleration of ions is proposed to account for the transfer of ion kinetic energy in favour of collisional ionization mechanisms.

A non-destructive grammar modification approach to modularity in grammatical evolution

Tue, 12 Jul 2011 00:00:00 GMT

Author: Swafford, John Mark; Hemberg, Erik; O'Neill, Michael; Nicolau, Miguel; Brabazon, Anthony

Abstract: Modularity has proven to be an important aspect of evolutionary computation. This work is concerned with discovering and using modules in one form of grammar-based genetic programming, grammatical evolution (GE). Previous work has shown that simply adding modules to GE’s grammar has the potential to disrupt fit individuals developed by evolution up to that point. This paper presents a solution to prevent the disturbance in fitness that can come with modifying GE’s grammar with previously discovered modules. The results show an increase in performance from a previously examined grammar modification approach and also an increase in performance when compared to standard GE.

Conference details: Presented at GECCO '11, the 13th annual conference companion on Genetic and evolutionary computation, Dublin, Ireland, 12-16, July 2011

COPOLAN : non-invasive occupancy profiling for preliminary assessment of HVAC fixed timing strategies

Tue, 01 Nov 2011 01:00:00 GMT

Author: Schoofs, Anthony; Delaney, Declan T.; O'Hare, G. M. P. (Greg M. P.); Ruzzelli, Antonio G.

Abstract: Nowadays, control of heating, cooling and ventilation equipment operation is mainly achieved via timers with fixed setback schedules, configured using experience and standard models of space occupancy. Applying generic timing strategies is however rarely optimal. Sensor-based systems offer a solution for dynamic control of equipment operation using real-time space occupancy input, but both deployment time and cost constraints hinder their integration if savings and return on investment are uncertain. This work introduces COPOLAN, a tool that correlates power consumption pat- terns and computers’ VLAN activity. Utilising computers’ VLAN activity auditing is key to obtain the power state of employees’ computer equipment over time, a prime indicator of employees’ presence within a building. At low cost and non-invasively, COPOLAN uncovers misalignment and pro- duces ground for (1) determining opportunities of improv- ing HVAC timing strategies and (2) helping decision making prior to integrating new equipment such as sensor-based systems. COPOLAN has been experimented on within a University department, where misalignment between power consumption and space occupancy patterns have highlighted 10 % energy saving opportunities.

Conference details: BuildSys 2011, 3rd ACM Workshop On Embedded Sensing Systems For Energy-Efficiency In Buildings, Seattle, USA, 1 November 2011

Soil nailing in glacial till : a design guide evaluation based on Irish and American field sites

Fri, 01 Jan 2010 01:00:00 GMT

Author: Laefer, Debra F.; Flahavan, Tom; Joy, James

Abstract: The French in-situ earth retaining system soil nailing began in 1970 and benefited greatly from that government’s investment in the 1986 study ‘Clouterre’. As such, French geology strongly influenced both practice and expectations world wide over the past four decades. Yet, recent studies in glacial till, a non-French soil type, have shown significant strength under-estimation using conventionally accepted design approaches. The paper reconsiders skin friction expectations for soil nail installations in glacial till. Installation at three glacial till sites (one American and two Irish) are examined in detail. Traditional British, French, and American de-sign methods and parameters are applied. Conventional methods under-predicted capacity by more than 50%, thereby raising serious questions as to the appropriateness of such design guidelines in glacial tills. New correlations based on pile installation design are proposed.

Conference details: 2010 Earth Retention Conference August 1–4, 2010 Bellevue, Washington

Engineering properties of historic brick – variability considerations as a function of stationary versus nonstationary kiln type

Thu, 01 Jan 2004 01:00:00 GMT

Author: Laefer, Debra F.; Boggs, Justin; Cooper, Nicole

Abstract: Brick produced prior to the mid-twentieth century exhibit high levels of variability in appearance, geometry, and mechanical properties. Understanding historic brick variability is important for accurate performance prediction of existing structures, and for the selection of appropriate replacement units. A lack of uniformity amongst historic brick can be caused by the molding and firing methods, as well as the composition of their raw materials. This paper focuses on one aspect of production-induced disparities: kiln type. Tremendous variance can be shown from this alone, between both kiln type and even within a single firing. Although kilns of past eras were constantly improved for energy efficiency, their products continued to be highly inconsistent in appearance and performance. This paper presents the mechanics of heat distribution in kilns and demonstrates its direct impact on the variability of engineering properties due to inconsistent heat application.

Assessment and code considerations for the combined effect of seismic base-isolation and viscoelastic dampers

Sat, 01 Jan 2011 01:00:00 GMT

Author: Erkal, Aykut; Tezcan, Semih S.; Laefer, Debra F.

Abstract: To propose an initial formulation for the passive control section of the Turkish Earthquake Code, the impact of base isolation and viscoelastic dampers on a four-story reinforced concrete (RC) frame building was considered under various one-dimensional earthquake excitations. Both statically equivalent seismic load methods (comparing Turkish Earthquake code with Uniform Building Code) and linear time history analyses were applied to the RC building based on a portion of the 1999 Kocaeli Earthquake ground motion record (modified to possess predominant spectral periods of T1=0.13 sec and T2=1.43 sec). Effective peak ground acceleration was set to 0.40g representing hard and soft soil conditions, respectively. Time history variations of upper column displacements and bending moments were compared, as well as story drift ratios. Reductions of the fixed-base case displacements and column bending moments were obtained of up to 73% under base-isolation, up to 25% with viscoelastic dampers, and up to 83% (with a unified response reduction factor) when both devices were both present.

The experience of Chinese students in Irish third level libraries: an investigation of current challenges and an analysis of possible solutions

Sat, 01 Oct 2011 00:00:00 GMT

Author: Mannion, David; Thornley, Clare V.

Abstract: Past research has shown that international students often experience difficulty in the library due to cultural differences and difficulties with language and communication. This can cause a gap between the quality of library service experienced by international students and indigenous students in any country. Previous studies have tended to investigate international students as one entire group rather than a multitude of different nationalities with different needs. In the Irish context little has been done to investigate the library experiences of international students, despite the constant efforts being made to attract international students to study here and the huge revenues they generate into the economy. This article, based on a Masters thesis in Library and Information Studies (2010), provides an insight into the academic library experiences of Chinese students (both under-graduate and post-graduate) studying at an Irish third level institution. Corroborating past research conducted elsewhere, it found that they do not always enjoy the same quality of library service as indigenous students or those whose first language is English. This is due to factors such as limited communication skills, diverse cultural traits, and a lack of understanding of library services. It also found that the library failed to adapt to a diverse user base in areas such as policy making and user instruction. It suggests that the library should acknowledge the cultural traits of Chinese students, and others, when developing library induction and training courses. It recommends that library staff undergo training in how best to serve an international user base. Finally, it suggests that co-operation with the International office and student societies are essential to find ways to establish a library service that is useful to all patrons.

Do RFIDs (radio frequency identifier devices) provide new ethical dilemmas for librarians and information professionals?

Thu, 01 Dec 2011 01:00:00 GMT

Author: Thornley, Clare V.; Gibb, Forbes; Ferguson, Stuart; Weckert, John

Abstract: Abstract: This paper provides an analysis of the current and potential ethical implications of RFID technology for the library and information professions. These issues are analysed as a series of ethical dilemmas, or hard-to-resolve competing ethical obligations, which the librarian has in relationship to information objects, library users and the wider social and political environment or state. A process model of the library is used as a framework for the discussion to illustrate the relationship between the different participants in the library system and it is argued that ethical analysis should involve the identification of future developments as well as current issues. The analysis shows that RFIDs do currently pose some dilemmas for librarians in terms of the conflicts between efficient service, privacy of users and an obligation to protect the safety of society as a whole, and that these are likely to become more problematic as the technology develops. This paper is part 2 of a series of papers on RFIDs and the library and information professions.

Dilemmas in information science (IS) and information retrieval (IR): recurring challenges or new solutions?

Thu, 01 Jan 2009 01:00:00 GMT

Author: Thornley, Clare V.

Abstract: Purpose: This paper analyses the extent to which understanding IS and IR as disciplines characterised by intractable dilemmas is a useful conceptual framework through reviewing and re-evaluating an important contribution to the field (Neill, 1987, 1992) in light of more recent developments. Design/methodology/approach: This paper reviews the discussion of central dilemmas within information science (IS) and information retrieval (IR), through literature review and conceptual analysis. It assesses the extent to which they remain intractable problems or whether improved solutions have been developed and discusses the implications of these ongoing challenges. The main problem addressed is, in Neill’s (1987, 1992) terminology “the dilemma of the subjective in information organisation and retrieval” which is understood as the problem of how the meaning of documents can be represented to meet the needs of the user. Findings: Many of the dilemmas discussed within IS and IR remain fairly intractable primarily because information and meaning have both subjective and objective qualities which often have a complex relationship. Recent technological developments have, however, altered the nature of some of these dilemmas and also created some new dilemmas for the subject. Research implications/limitations: Historical perspectives within IR and IS should be used when discussing theoretical and technological developments in the subject. The conceptual framework of dilemmas remains a useful theoretical tool for IS and IR in terms of examining the nature of problems in research and practice. Originality/value: This paper re-visits an important theme in IS and IR and provides an updated perspective on some central issues.

A dialectical approach to information retrieval

Mon, 01 Jan 2007 01:00:00 GMT

Author: Thornley, Clare V.; Gibb, Forbes

Abstract: Purpose:The paper explores the question of whether the often paradoxical and conceptually contradictory discipline of information retrieval (IR) can be understood more clearly when it is analysed from a dialectical perspective. Methodology/Approach:Conceptual analysis and literature review. Findings:A dialectical understanding of meaning can assist in clarifying some aspects of the complex nature of current IR theory. Research Implications:Philosophy has the potential to explore the conflicts and contradictions in IR and should not be used just as a means of synthesis and resolution. The use of the philosophy of meaning should include a broader understanding of the philosophical oppositions which lie behind the nature of meaning. Originality/value of paper:This paper suggests a new perspective on the role of meaning in IR: the dialectical model.

Dendrochronological analysis of oak from a shipwreck, Rostock Ost FPL71, Germany

Thu, 01 Sep 2011 00:00:00 GMT

Author: Daly, Aoife

Abstract: Marie Curie funded project: Chronology, Culture and Archaeology, based at the School of Archaeology, University College Dublin. In this report the dendrochronological analysis of eight oak samples from a shipwreck found at Rostock Ost is described.

Schooling and voter turnout : is there an American exception?

Sun, 01 Apr 2012 00:00:00 GMT

Author: Chevalier, Arnaud; Doyle, Orla

Abstract: One of the most consistent findings in studies of electoral behaviour is that individuals with higher education have a greater propensity to vote. The nature of this relationship is much debated, with US studies generally finding evidence of a causal relationship, while European studies generally reporting no causal effect. To assess whether the US is an exception we rely on an international dataset incorporating 38 countries, the ISSP (International Social Survey Programme) from 1985 to 2010. Both instrumental variable and multi-level modelling approaches reveal that the US is an outlier regarding the relationship between education and voter turnout. Moreover country-specific institutional and economic factors do not explain the heterogeneity in the relationship of interest. Alternatively, we show that disenfranchisement laws in the U.S. mediates the effect of education on voter turnout, such that the education gradient in voting is greater in U.S. States with the harshest disenfranchisement legislature. As such, the observed relationship between education and voting is partly driven by the effect of education on crime.

An egalitarian case for basic income

Wed, 01 Jan 1992 01:00:00 GMT

Author: Baker, John

Abstract: In section 1, I set out a general perspective on the nature of egalitarianism and relate it to some familiar conceptions of economic equality. In section 2, I argue in keeping with the popular notion of equality that it makes sense to think of equal income as a baseline against which departures need to be justified. Section 3 discusses some problems which arise concerning departures from equal income justified by different needs, and argues for a particular approach based on what I shall call a 'background agreement' on need. Section 4 looks at the issue of relating income to work, and tries to construct and defend an interpretation of the idea that income inequalities should compensate people for differences in their work. I argue for a system of 'compensating differentials' based on a background agreement regarding the benefits and burdens of different kinds and amounts of work. Section 5 considers the principles of free choice of occupation and of the right not to work, with particular reference to their role in a system of compensating differentials. In section 6, I show how the case for a basic income follows from the conception of economic equality I have put forward.

Systematic investigation of self-absorption property and conversion efficiency of 6.7-nm extreme ultraviolet sources

Wed, 01 Dec 2010 01:00:00 GMT

Author: Otsuka, Takamitsu; White, John; Kilbane, Deirdre; Higashiguchi, Takeshi; Yugami, Noboru; Yatagai, Toyohiko; Jiang, Weihua; Endo, Akira; Dunne, Padraig; O’Sullivan, Gerry

Abstract: We have demonstrated rare-earth plasma extreme ultraviolet sources at 6.7 nm to investigate the spectral behavior and the conversion efficiencies to different laser wavelength and the initial target densities. The conversion efficiency was maximized to be 0.9% at laser intensity of 7 × 1012 W/cm2 at its wavelength of 1064 nm, which is attributed to the minimum self-absorption effect by use of the low initial density target, together with the narrow spectrum. It is important to use a low initial density target and to produce low electron density plasmas for efficient EUV sources using the high-Z targets.

Rotor angle stability with high penetrations of wind generation

Wed, 01 Feb 2012 01:00:00 GMT

Author: Vittal, Eknath; O'Malley, Mark; Keane, Andrew

Abstract: This paper explores the relationship between wind generation, particularly the control of reactive power from variable speed wind turbine generators, and the rotor angle stability of the conventional synchronous generators in the system. Rotor angle stability is a dynamic phenomenon generally associated with changes in active power flows that create angular separation between synchronous units in the system. With larger penetrations of wind generation being introduced into power systems, there will be large flows of active power from asynchronous generation in the system. These asynchronous active power flows can aid in maintaining the rotor angle stability of the system. However, the manner in which wind generation injects reactive power into the system can be critical in maintaining angular stability of the synchronous units. Utilizing wind generation to control voltage and reactive power in the system can ease the reactive power burden on synchronous generators, and minimize angular separation in the system following a contingency event and can provide a significant level of support which will become increasingly important in future power systems.

Minimising transmission reactive support required by high penetration of distributed wind power distribution

Tue, 01 Nov 2011 01:00:00 GMT

Author: Ochoa, Luis; Keane, Andrew; Dent, Chris; Harrison, Gareth

Abstract: Wind power generation is the fastest growing renewable technology worldwide with large on- and off-shore wind farms being connected to the transmission networks. A significant share of it, however is still being deployed at distribution levels. While distributed wind generation presents traditionally passive distribution networks with well-established technical challenges, reactive support needed by high penetrations of such new generation capacity might also have an impact on the week areas of the transmission grid. In this work, a multi-period AC optimal power flow-based technique is proposed to find power factor and substation settings that minimise the transmission reactive support required by variable distributed generation while also considering N-1 contingencies. A section of Irish distribution network is analysed. Results show the significant benefits that a passive approach such as the use of optimal power factor and substation settings can achieve.

Sirolimus enhances cyclosporine a-induced cytotoxicity in human renal glomerular mesangial cells

Mon, 23 Jan 2012 01:00:00 GMT

Author: O'Connell, Séin; Slattery, Craig; Ryan, Michael P.; McMorrow, Tara

Abstract: End Stage Renal Disease (ESRD) is an ever increasing problem worldwide. However the mechanisms underlying disease progression are not fully elucidated. This work addressed the nephrotoxicity induced by the immunosuppressive agents’ cyclosporine A (CsA) and sirolimus (SRL). Nephrotoxicity is the major limiting factor in the long term use of CsA. SRL causes less nephrotoxicity than CsA. Therefore investigations into the differential effects of these agents may identify potential mechanisms of nephrotoxicity and possible means to prevent ESRD induced by therapeutic drugs. Using ELISA, western blotting, quantitative PCR and a reporter gene assay we detailed the differential effects of the immunosuppressive agents CsA, and SRL in human renal mesangial cells. CsA treatment increased profibrotic TGF-β1 secretion in human mesangial cells whereas SRL did not, indicating a role for TGF-β in CsA toxicity. However we observed a synergistic nephrotoxic effect when CsA and SRL were co-administered. These synergistic alterations may have been due to an increase in CTGF which was not evident when the immunosuppressive drugs were used alone. The CsA/SRL combination therapy significantly enhanced Smad signalling and altered the extracellular matrix regulator matrix metalloproteinase 9 (MMP-9). Inhibition of the ERK 1/2 pathway, attenuated these CsA/SRL induced alterations indicating a potentially significant role for this pathway.

Linearized discrete-time model of higher order charge-pump PLLs

Mon, 29 Aug 2011 00:00:00 GMT

Author: Bi, Chuang; Curran, Paul F.; Feely, Orla

Abstract: In this paper, we derive linearized discrete-time models of higher order Charge-Pump Phase-Locked Loops (CPPLLs). The behaviour of CP-PLLs in the steady state is analysed and an important feature is developed. The nonlinear state equations of CP-PLLs are linearized around the equilibrium point. The linearized discrete-time model is finally verified using behavioral simulations in Matlab and PSpice.

Conference details: European Conference on Circuit Theory and Design (ECCTD), Linkoping, Sweden, 29-31 August, 2011

Output-jitter performance of second-order digital bang-bang phase-locked loops with nonaccumulative reference clock jitter

Wed, 01 Jun 2011 00:00:00 GMT

Author: Tertinek, Stefan; Feely, Orla

Abstract: Bang-bang phase-locked loops (BBPLLs) are inherently nonlinear systems due to the binary phase detector (BPD). While they are typically used for clock and data recovery, the ongoing trend toward digital loop implementations has resulted in several digital BBPLLs (DBBPLLs) suitable for frequency synthesis. This brief investigates the effect of nonaccumulative reference clock jitter (due to white phase noise) in second-order DBBPLLs, comparing the output jitter with that of first-order DBBPLLs. For small clock jitter, the nonlinear loop behavior is modeled as a two-dimensional Markov chain, and the output jitter is smaller than but close to that of a first order loop. For large clock jitter, the BPD nonlinearity is linearized, and the output jitter is larger than that of a first order loop; it is proportional to clock jitter and inversely proportional to the square root of the stability factor—the ratio of the proportional path gain to the integral-path gain of the digital loop filter.