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Amaratunga, Piyadarsha,Lee, Myeongsoon,Kim, Junhyung,Lee, Dongil Canadian Science Publishing 2011 Canadian journal of chemistry Vol.89 No.8
<P> We report the preparation and photocatalytic activity of TiO2 nanocomposites modified with monolayer-protected gold clusters (MPCs). Highly monodisperse tiopronin-coated MPCs with core diameters of 2.2 ± 0.2 nm were pre-prepared and then anchored onto a TiO2 surface using the bifunctional tiopronin linker. In this method, the gold core size was preserved after calcination at 260 °C as well as the anchoring process, and the gold loading on TiO2 could be precisely controlled by the experimental condition. The photocatalytic degradation of Rhodamine 590 (Rh-590) was carried out with thus prepared MPC-TiO2 composites. Mechanistic study of the photocatalytic reactions revealed that the degradation of Rh-590 occurs via the oxidative pathway by photogenerated holes. The photocatalytic activity of the MPC-TiO2 composites was found to increase significantly upon calcination at 260 °C, whereas the size of gold particles remained at their initial size. The photocatalytic activity of the composites, however, drastically decreased when the composites were calcined at 400 °C. X-ray photoelectron spectroscopy analysis of the calcined composites was conducted to understand the vastly different calcination results. A significant amount of oxidized sulfur remained in the composites after calcination at 400 °C, which appears to be responsible for the drastic decrease in the photocatalytic activity. </P>
Aruna Wimalarathna,Indika Thilakumara,Vajira Jayasinghe,Prasad Amaratunga,Ruwan Jayasinghe 대한치과이식임플란트학회 2021 The Korean Academy of Implant Dentistry Vol.40 No.4
Purpose: The purpose of this study was to evaluate a cohort of edentulous Sri Lankan patients and to consider important anatomical landmarks and available bone seen in dental panoramic tomography (DPT) for the placement of implants. Materials and Methods: A total of 152 clinically edentulous arches were selected from the DPTs of 81 patients. DPTs were taken following standard protocols. Radiographs were evaluated by a specialist for the following: the relative thickness of the soft tissue coverage of the alveolar ridge, location of the mandibular canal, mental foramen and the maxillary sinus, bone height at the maxillary canine, first premolar region, mandibular canine, and symphyseal region, and for the presence of buried roots or impacted teeth and foreign bodies. Results: The mean age of the patients in the sample was 68.4±9.8 years. The sample comprised 59.0% females and 41.0% males. Out of 152 edentulous arches, 75 (49.0%) were mandibular and 77 (51.0%) were maxillary arches. The mean soft tissue thickness was 2.2±0.89 mm. The average bone height from the lower alveolar crest to the mandibular canal was 10.5 mm in the first molar region. The position of the mental foramen was at 21.1±5.32 mm on the right side and 22.4±4.63 mm on the left from the midline. The bone height from the floor of the maxillary sinus and the alveolar crest was <5 mm in 73.3% of patients on the right side and 72.0% on the left side. Conclusions: Standard conventional implants were possible in the anterior segment and only short implants were possible in the posterior segment for the majority of edentulous Sri Lankan patients without the risk of damaging vital structures and with no additional pre-implant corrective surgical procedures. The average readings of anatomical parameters revealed in this study will be useful in the clinical and radiographical assessment of edentulous patients for dental implants.
Aligned carbon nanotubes/fibers for applications in vacuum microwave devices
W.I.Milne,K.B.K.Teo,G.A.J.Amaratunga,R.Lacerda,P.Legagneux,G.Pirio,V.Semet,V.Thien Binh 한국물리학회 2004 Current Applied Physics Vol.4 No.5
Carbon nanotubes exhibit extraordinary eld emission properties because of their high electrical conductivity, ideal high aspectratio whisker-like shape for geometrical eld enhancement, and remarkable thermal stability. This paper will describe the PECVDgrowth of vertically aligned arrays of carbon nanotubes which are suitable for use as the electron emitters in a novel type ofmicrowave amplier capable of producing of order 10 W at 30 GHz.
Electron emission from arrays of carbon nanotubes/fibres
W. I. Milne,K. B. K. Teo,M. Chhowalla,G. A. J. Amaratunga,D. Pribat,P. Legagneux,G. Pirio,Vu Thien Binh,V. Semet 한국물리학회 2002 Current Applied Physics Vol.2 No.6
The overall aim of this work is to produce arrays of eld emitting microguns, based on carbon nanotubes, which can be utilised inthe manufacture of large area eld emitting displays, parallel e-beam lithography systems and electron sources for high frequency(MWCNTs) using a dc plasma technique and a Ni catalyst. We will discuss how the density of the carbon nanotube/bres can bevaried by reducing the deposition yield through nickel interaction with a diusion layer or by direct lithographic patterning of the Nicatalyst to precisely dene the position of each nanotube/bre. Details of the eld emission behaviour of the dierent arrays ofMWCNTS will also be presented.. 2002 Published by Elsevier Science B.V.
Biswas, Partha P.,Suganthan, P.N.,Mallipeddi, R.,Amaratunga, Gehan A.J. Elsevier 2018 ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENC Vol.68 No.-
<P><B>Abstract</B></P> <P>Optimal power flow (OPF) is a highly non-linear complex optimization problem where the steady state parameters of an electrical network need to be determined for its economical and efficient operation. The complexity of the problem escalates with ubiquitous presence of constraints in the problem. Solving OPF remains a popular but challenging task among power system researchers. In last couple of decades, numerous evolutionary algorithms (EAs) have been applied to find optimal solutions with different objectives of OPF. However, the search method adopted by EAs is unconstrained. An extensively used methodology to discard infeasible solutions found during the search process is the static penalty function approach. The process requires appropriate selection of penalty coefficients decided largely by tedious trial and error method. This paper presents performance evaluation of proper constraint handling (CH) techniques — superiority of feasibly solutions (SF), self-adaptive penalty (SP) and an ensemble of these two constraint handling techniques (ECHT) with differential evolution (DE) being the basic search algorithm, on the problem of OPF. The methods are tested on standard IEEE 30, IEEE 57 and IEEE 118-bus systems for several OPF objectives such as cost, emission, power loss, voltage stability etc. Single objective and weighted sum multi-objective cases of OPF are studied under the scope of this literature. Simulation results are analyzed and compared with most recent studies on the problem.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimal power flow problems for IEEE 30, 57 and 118-bus systems are studied. </LI> <LI> Several single and multi-objective case studies are performed. </LI> <LI> Performances of 3-constraint handling techniques are analyzed. </LI> <LI> Differential evolution (DE) is used as basic search algorithm. </LI> <LI> Results are compared with most recent studies and improvement is observed. </LI> </UL> </P>
Biswas, Partha P.,Mallipeddi, R.,Suganthan, P.N.,Amaratunga, Gehan A.J. Elsevier 2017 Applied soft computing Vol.60 No.-
<P>Both active and reactive power play important roles in power system transmission and distribution networks. While active power does the useful work, reactive power supports the voltage that necessitates control from system reliability aspect as deviation of voltage from nominal range may lead to inadvertent operation and premature failure of system components. Reactive power flow must also be controlled in the system to maximize the amount of real power that can be transferred across the power transmitting media. This paper proposes an approach to simultaneously minimize the real power loss and the net reactive power flow in the system when reinforced with distributed generators (DGs) and shunt capacitors (SCs). With the suggested method, the system performance, reliability and loading capacitycan be increased by reduction of losses. A multiobjective evolutionary algorithm based on decomposition (MOEA/D) is adopted to select optimal sizes and locations of DGs and SCs in large scale distribution networks with objectives being minimizing system real and reactive power losses. MOEA/D is the process of decomposition of a multiobjective optimization problem into a number of scalar optimization subproblems and optimizing those concurrently. Case studies with standard IEEE 33-bus, 69-bus, 119-bus distribution networks and a practical 83-bus distribution network are performed. Output results of MOEA/D method are compared with similar past studies and notable improvement is observed. (C) 2017 Elsevier B.V. All rights reserved.</P>
Hot Electron Field Emission <i>via</i> Individually Transistor-Ballasted Carbon Nanotube Arrays
Li, Chi,Zhang, Yan,Cole, Matthew T.,Shivareddy, Sai G.,Barnard, Jon S.,Lei, Wei,Wang, Baoping,Pribat, Didier,Amaratunga, Gehan A. J.,Milne, William I. American Chemical Society 2012 ACS NANO Vol.6 No.4
<P>We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source–drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-4/nn300111t/production/images/medium/nn-2012-00111t_0006.gif'></P>