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Search Results: 1 - 10 of 69 matches for " Gehan Amaratunga "
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Quantum Computation with Ballistic Electrons
Radu Ionicioiu,Gehan Amaratunga,Florin Udrea
Physics , 2000, DOI: 10.1142/S0217979201003521
Abstract: We describe a solid state implementation of a quantum computer using ballistic single electrons as flying qubits in 1D nanowires. We show how to implement all the steps required for universal quantum computation: preparation of the initial state, measurement of the final state and a universal set of quantum gates. An important advantage of this model is the fact that we do not need ultrafast optoelectronics for gate operations. We use cold programming (or pre-programming), i.e., the gates are set before launching the electrons; all programming can be done using static electric fields only.
Ballistic Single-Electron Quputer
Radu Ionicioiu,Gehan Amaratunga,Florin Udrea
Physics , 1999,
Abstract: We propose a new solid state implementation of a quantum computer (quputer) using ballistic single electrons as flying qubits in 1D nanowires. We use a single electron pump (SEP) to prepare the initial state and a single electron transistor (SET) to measure the final state. Single qubit gates are implemented using quantum dots as phase shifters and electron waveguide couplers as beam splitters. A Coulomb coupler acts as a 2-qubit gate, using a mutual phase modulation effect. Since the electron phase coherence length in GaAs/AlGaAs heterostructures is of the order of 30$\mu$m, several gates (tens) can be implemented before the system decoheres.
FEM Modeling of Periodic Arrays of Multiwalled Carbon Nanotubes
Haider Butt;Timothy D. Wilkinson;Gehan A. J. Amaratunga
PIER M , 2012, DOI: 10.2528/PIERM11090504
Abstract: Multiwalled carbon nanotubes display dielectric properties similar to those of graphite, which can be calculated using the well known Drude-Lorentz model. However, most computational softwares lack the capacity to directly incorporate this model into the simulations. We present the finite element modeling of optical propagation through periodic arrays of multiwalled carbon nanotubes. The dielectric function of nanotubes was incorporated into the model by using polynomial curve fitting technique. The computational analysis revealed interesting metamaterial filtering effects displayed by the highly dense square lattice arrays of carbon nanotubes, having lattice constants of the order few hundred nanometers. The curve fitting results for the dielectric function can also be used for simulating other interesting optical applications based on nanotube arrays.
Fabrication of Carbon Nanotubes on Inter-Digitated Metal Electrode for Switchable Nanophotonic Devices
Qing Dai;Haider Butt;Ranjith Rajasekharan;Timothy D. Wilkinson;Gehan A. J. Amaratunga
PIER , 2012, DOI: 10.2528/PIER12022603
Abstract: This paper reports the modeling and characterization of interdigitated rows of carbon nanotube electrodes used to address a liquid crystal media. Finite Element Method modeling of the nanotube arrays was performed to analyze the static electric fields produced to find suitable electrode geometry. A device was fabricated based on the simulation results and electro optics characteristics of the device are presented. This finding has applications in the development of micron and submicron pixels, precise beem steering and nanotube based active back planes.
Photonic Crystals & Metamaterial Filters Based on 2D Arrays of Silicon Nanopillars
Haider Butt;Qing Dai;Timothy D. Wilkinson;Gehan A. J. Amaratunga
PIER , 2011, DOI: 10.2528/PIER10122501
Abstract: Highly dense two-dimensional periodic arrays of nano-scaled silicon pillars present interesting photonic band gaps and the capacity to act as photonic crystals which can mould, manipulate and guide light. We demonstrate finite element modelling of silicon pillars based photonic crystals and their effective use in applications like waveguides, optical power dividers, multiplexers and switches. The optical wave propagation through these structures was thoroughly simulated and analysed, confirming their high efficiency. The band gaps studied through the plane wave expansion method are also presented. Later the fabrication of highly periodic two-dimensional arrays of silicon pillars through the process of etching is also explained. The arrays with pillar radius of 50 nm and lattice constant of 400 nm were successfully utilised as photonic crystal waveguides and their measured results are reported. Moreover, the silicon nanopillars sputtered with noble metals can also display artificial optical properties and act as metamaterials due to the mutual plasmonic coupling effects. We report the theoretical results for the silicon nanopillars based metamaterial high-pass filter.
Electrical transport between epitaxial manganites and carbon nanotubes
Luis E. Hueso,Gavin Burnell,Seung Nam Cha,Jae Eun Jang,Jose L. Prieto,Leticia P. Granja,Christopher Bell,Dae-Joon Kang,Manish Chhowalla,Gehan A. J. Amaratunga,Neil D. Mathur
Physics , 2005, DOI: 10.1063/1.2170431
Abstract: The possibility of performing spintronics at the molecular level may be realized in devices that combine fully spin polarized oxides such as manganites with carbon nanotubes. However, it is not clear whether electrical transport between such different material systems is viable. Here we show that the room temperature conductance of manganite-nanotube-manganite devices is only half the value recorded in similar palladium-nanotube-palladium devices. Interestingly, the former shows a pseudogap in the conductivity below the relatively high temperature of 200 K. Our results suggest the possibility of new spintronics heterostructures that exploit fully spin polarized sources and drains.
An Empirical Investigation on Leadership Styles Applied for Global Brand Management of Multinational Organizations in the United States  [PDF]
Tilokie Depoo, Gehan Dhameeth Shanmuganathan
Open Journal of Business and Management (OJBM) , 2013, DOI: 10.4236/ojbm.2013.12003
Abstract: Purpose: The purpose of this study is to understand the application of leadership styles in multinational organizations operating in the United States for their global brand management. Design/Methodology/Approach: This quantitative study design uses three hundred and seventy (370) sample units that were drawn from all levels in organizations in collecting data for the final analysis. Findings: Situational leadership style is the most dominant leadership style applied in global brand management. However, certain critical perspectives at the time of investigation revealed from the study are discussed in the paper. Originality/Value: This study is the first to provide underpinnings of employee’s perception of leadership.
A New Approach to Evaluate the Hygienic Condition of Commercial Hatcheries
Z. Moustafa Gehan
International Journal of Poultry Science , 2009,
Abstract: Hatchery hygiene was evaluated in two commercial broiler hatcheries using open-plate method, surface swabbing and microbiological examination of hatchery fluff. Air samples and surface swabs were collected from: inside the hatch unit, the corridor outside the hatch unit and the chick processing room, while, fluff samples were collected after hatching from the hatch unit and the chick processing room. After cleaning and disinfection process of the hatch, four commercial disinfectants were evaluated for their effectiveness for controlling the hatchery contaminants, TH4 (combination of glutaraldehyde + quaternary ammonium compound), Virucidal extra (chlorine preparation), Advantage 256 (phenolics) and Perasan (per-acetic acid). The obtained results indicated that surface swabbing and microbiological examination of hatch fluff could detect higher degree of contamination than open-plate method in the two investigated hatcheries. Per-acetic acid preparations and (glutaraldehyde + quaternary ammonium compound) could reduce completely hatchery contaminants after 30 min of application. Conclusively, open-plate method is easy to perform and inexpensive but may give false indication that the air is clean when it is not. So, surface swabbing and microbiological examination of hatch fluff are more reliable methods for evaluating the hygienic status of a hatchery. Moreover, Surface swabbing method is more accurate than open-plate method in evaluating the decontamination process of the hatch. Hatchery sanitation and the proper use of effective disinfectant are essential for successful operation of any commercial poultry hatchery. Per-acetic acid and (glutaraldehyde + quaternary ammonium compound) proved their efficiency in controlling hatchery contaminants and can be used as safe alternatives to formalin in poultry hatcheries.
Short Term Prognostic Utility of Tc-99m DMSA Renal Imaging in Sepsis Induced Acute Renal Failure; Provisional Data  [PDF]
Amr Amin, Hatem Nasr, Gehan Younis, Hatem Gamal
International Journal of Clinical Medicine (IJCM) , 2013, DOI: 10.4236/ijcm.2013.412094
Abstract:

Background: Sound prognostic data in sepsis induced acute renal failure (SARF) are lacking especially on the short term outcome [STO] in the intensive care unit [ICU]. We addressed the use of Tc-99m DMSA [2,3-dimercaptosuccinicacid] renal cortical imaging as a prognostic tool in SARF. Methods: Forty patients with acute renal failure due to sepsis [age range 15-74 years; median 44.5] were subjected for full history taking complete physical examination, routine ICU monitoring, routine laboratory investigations, APACHE II [Acute Physiology and Chronic Health Evaluation] and SOFA [Sequential Organ Failure Assessment] together with Tc-99m DMSA cortical renal scintigraphy. Patients’ death in the ICU or discharge was considered as the end point of the study representing the so-called short term outcome [STO]. Results: 25% mortality rate [10/40] was found along the admission period in the ICU. All non-survivors were abnormal with DMSA imaging [NPV & PPV 100% & 66.7% respectively]. Abnormal DMSA cases showed significant positive associations with serum creatinine at admission [r = 0.5; P 0.02]; admission duration [r = 0.4; P 0.002]; APACHE II score [r = 0.5; P 0.004] and STO [r = 0.4; P 0.03]. Statistically significant difference was elicited between subjects with normal and abnormal DMSA regarding the same parameters. Conclusion: This preliminary data could raise Tc-99m DMSA renal imaging as a prognostic tool in SARF that could allow influential interference to prohibit dramatic outcomes as mortality.

Implementation of critical success factors in construction research and development process
U Kulatunga, D Amaratunga, R Haigh
International Journal of Engineering, Science and Technology , 2010,
Abstract: Construction research and development (R&D) process has a number of issues that affect its success. These issues imply that Critical Success Factors (CSFs) of construction R&D process are not properly addressed. Not knowing CSFs could lead to not implementing them and not paying proper attention for them. The study investigates CSFs of construction R&D process and their implementation/consideration during the R&D process. A comprehensive literature review was used first to develop construction R&D process. CSFs and their implementation/consideration were evaluated by a questionnaire survey. Construction R&D process was derived with four phases namely Initiation, Conceptualizing, Development and Launch and Management activities that support coordination and resourcing of R&D process. Study revealed that, as a whole there is a gap between the importance of success factors against their implementation/consideration as majority of CSFs are not properly implemented compared to the importance attached to them.
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