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Articles 1 - 30 of 35
Full-Text Articles in Engineering
A Fiber Bragg Grating-Based All-Fiber Sensing Systems For Telerobotic Cutting Applications, Ginu Rajan, Dean Callaghan, Yuliya Semenova, Mark Mcgrath, Eugene Coyle, Gerald Farrell
A Fiber Bragg Grating-Based All-Fiber Sensing Systems For Telerobotic Cutting Applications, Ginu Rajan, Dean Callaghan, Yuliya Semenova, Mark Mcgrath, Eugene Coyle, Gerald Farrell
Articles
A fiber Bragg grating (FBG)-based strain sensing system for minimally invasive telerobotic cutting applications is presented in this paper. Investigations assume that a scissor blade can be approximated as a uniformly tapered cantilever beam. A replica of the scissor blade is produced and strain characterization has been carried out using an FBG sensor system. Results are validated against measurements obtained using conventional electrical resistance strain gauges. The scissor blade experiences both direct and lateral forces during cutting, hence the system is characterized for a direct load range of 0-30 N and a lateral load range of 0-10 N. The results …
The Generation Of Domestic Electricity Load Profiles Through Markov Chain Modelling, Fintan Mcloughlin, Aidan Duffy, Michael Conlon
The Generation Of Domestic Electricity Load Profiles Through Markov Chain Modelling, Fintan Mcloughlin, Aidan Duffy, Michael Conlon
Articles
Micro-generation technologies such as photovoltaics and micro-wind power are becoming increasing popular among homeowners, mainly a result of policy support mechanisms helping to improve cost competiveness as compared to traditional fossil fuel generation. National government strategies to reduce electricity demand generated from fossil fuels and to meet European Union 20/20/20 targets is driving this change. However, the real performance of these technologies in a domestic setting is not often known as high time resolution models for domestic electricity load profiles are not readily available. As a result, projections in terms of reducing electricity demand and financial paybacks for these micro-generation …
A Hybrid Highly Birefringent Fiber Optic Sensing System For Simultaneous Strain And Temperature Measurement, Piotr Lesiak, Ginu Rajan, Yuliya Semenova, Gerald Farrell, Anna Boczkowska, Andrzej Domanski, Tomasz Wolinkski
A Hybrid Highly Birefringent Fiber Optic Sensing System For Simultaneous Strain And Temperature Measurement, Piotr Lesiak, Ginu Rajan, Yuliya Semenova, Gerald Farrell, Anna Boczkowska, Andrzej Domanski, Tomasz Wolinkski
Articles
A novel hybrid fiber optic sensor based on integration of polarimetric fiber sensors for simultaneous strain and temperature measurement is presented in this paper. Two types of polarimetric fibers are used: a side-hole fiber and a polarization maintaining photonic crystal fiber. The disadvantage of each sensor type can be overcome by using the sensors in a complementary manner to measure temperature independently from average strain.
Microstrip-Fed Wideband Circularly Polarized Printed Antenna, Xiulong Bao, Max Ammann, Patrick Mcevoy
Microstrip-Fed Wideband Circularly Polarized Printed Antenna, Xiulong Bao, Max Ammann, Patrick Mcevoy
Articles
A wideband circularly-polarized printed antenna is proposed, which employs an asymmetrical dipole and a slit in the ground plane which are fed by an L-shaped microstrip feedline using a via. The proposed antenna geometry is arranged so that the orthogonal surface currents, which are generated in the dipole, feedline and ground plane, have the appropriate phase to provide circular polarization. A parametric study of the key parameters is made and the mechanism for circular polarization is described. The measured results show that the impedance bandwidth is approximately 1.34 GHz (2.45 GHz to 3.79 GHz) and the 3 dB axial ratio …
A Monocular Marker-Free Gait Measurement System, Jane Courtney, Annraoi M. De Paor
A Monocular Marker-Free Gait Measurement System, Jane Courtney, Annraoi M. De Paor
Articles
This paper presents a new, user-friendly, portable motion capture and gait analysis system for capturing and analyzing human gait, designed as a telemedicine tool to monitor remotely the progress of patients through treatment. The system requires minimal user input and simple single-camera filming (which can be acquired from a basic webcam) making it very accessible to nontechnical, nonclinical personnel. This system can allow gait studies to acquire a much larger data set and allow trained gait analysts to focus their skills on the interpretation phase of gait analysis. The design uses a novel motion capture method derived from spatiotemporal segmentation …
Validated Real-Time Energy Models For Small-Scale Grid-Connected Pv-Systems, Lacour Ayompe, Aidan Duffy, Sarah Mccormack, Michael Conlon
Validated Real-Time Energy Models For Small-Scale Grid-Connected Pv-Systems, Lacour Ayompe, Aidan Duffy, Sarah Mccormack, Michael Conlon
Articles
This paper presents validated real-time energy models for small-scale grid-connected PV-systems suitable for domestic application. The models were used to predict real-time AC power output from a PV system in Dublin, Ireland using 30-min intervals of measured performance data between April 2009 and March 2010. Statistical analysis of the predicted results and measured data highlight possible sources of errors and the limitations and/or adequacy of existing models, to describe the temperature and efficiency of PV-cells and consequently, the accuracy of power prediction models. PV-system AC output power predictions using empirical models for PV-cell temperature and efficiency prediction showed lower percentage …
Development Of A 12 Kva Dsp-Controlled Laboratory Prototype Upqc, Iurie Axente, Jayanti Navilgone Ganesh, Malabika Basu, Michael Conlon, Kevin Gaughan
Development Of A 12 Kva Dsp-Controlled Laboratory Prototype Upqc, Iurie Axente, Jayanti Navilgone Ganesh, Malabika Basu, Michael Conlon, Kevin Gaughan
Articles
This paper reports the development of a laboratory prototype of a fully digital DSP-controlled 12-kVA unified power quality conditioner (UPQC), capable of compensating for both the supply voltage and the load current imperfections. A fully digital controller based on the TMS320F2812 DSP platform is implemented for the reference generation as well as control purposes. The delay problem in the digital controller is overcome by application of a fast DSP, a compact control technique and proper flow of control steps in the DSP software. A phase-locked loopless software grid synchronization method has been implemented for the effective operation of the UPQC …
Projected Costs Of A Grid-Connected Domestic Pv System Under Different Scenarios In Ireland, Using Measured Data From A Trial Installation, Lacour Ayompe, Aidan Duffy, Sarah Mccormack, Michael Conlon
Projected Costs Of A Grid-Connected Domestic Pv System Under Different Scenarios In Ireland, Using Measured Data From A Trial Installation, Lacour Ayompe, Aidan Duffy, Sarah Mccormack, Michael Conlon
Articles
This paper presents results of a study of projected costs for a grid-connected PV system for domestic application in Ireland. The study is based on results from a 1.72kWpPV system installed on a flat rooftop in Dublin, Ireland. During its first year of operation a total of 885.1kWh/kWp of electricity was generated with a performance ratio of 81.5%. The scenarios employed in this study consider: a range of capital costs; cost dynamics based on a PV module learning rate of 2+/-75%; projections for global annual installed PV capacity under an advanced and moderate market growth conditions; domestic electricity cost growth …
Reconfigurable Antenna With Elevation And Azimuth Beam Switching, S. Shynu, Max Ammann
Reconfigurable Antenna With Elevation And Azimuth Beam Switching, S. Shynu, Max Ammann
Articles
A reconfigurable microstrip antenna is proposed for low-cost adaptive beam-switching applications. A small patch-slot-ring structure is used as the radiating element where an asymmetrical arrangement of p-i-n diodes is employed to switch the pattern in four directions. The antenna provides pattern switching of 65° and 45° in its fundamental mode for the elevation and azimuth planes, respectively. By maintaining the resonant frequency and beamwidth as relatively constant, beam switching is realized using a single feed point.
Input-Output Analysis Of Irish Construction Sector Greenhouse Gas Emissions, Adolf Acquaye, Aidan Duffy
Input-Output Analysis Of Irish Construction Sector Greenhouse Gas Emissions, Adolf Acquaye, Aidan Duffy
Articles
Ireland is committed to limiting its greenhouse gas (GHG) emissions to 113% of 1990 levels over the period 2008-12 and to 84% of 2005 levels by 2020 under the Kyoto Agreement and the EU’s ’20 20’ by 2020 respectively. National policies have targeted many industry sectors but have failed to directly tackle GHG emissions associated with construction activity. This paper estimates energy and GHG emissions intensities of the Irish construction sector and subsectors and estimates its contribution to Irish national emissions. This information is used to identify and assess the impacts of policy measures which would result in a reduction …
Miniature Ceramic Pifa For Uwb Band Group 3 And 6, David Kearney, Matthias John, Max Ammann
Miniature Ceramic Pifa For Uwb Band Group 3 And 6, David Kearney, Matthias John, Max Ammann
Articles
A ceramic chip planar inverted-F antenna (PIFA) is proposed for integration into a mobile handset providing UWB functionality across band groups 3 and 6. The antenna design exhibits a total efficiency of greater than 50% across the entire 6.39 GHz bandwidth while maintaining a very small volume of 57.6 mm^3 . The antenna uses a combination of the normal PIFA resonance and a second resonance due to the ceramic block to achieve a broad ultrawideband (UWB) bandwidth.
Spontaneous Periodic Deformations In Nonchiral Planar-Aligned Bimesogens With A Nematic-Nematic Transition And A Negative Elastic Constant, V. P. Panov, J. K. Vij, Yuri Panarin, A. Kohlmeier, M. G. Tamba, R. A. Lewis, G. H. Mehl
Spontaneous Periodic Deformations In Nonchiral Planar-Aligned Bimesogens With A Nematic-Nematic Transition And A Negative Elastic Constant, V. P. Panov, J. K. Vij, Yuri Panarin, A. Kohlmeier, M. G. Tamba, R. A. Lewis, G. H. Mehl
Articles
Hydrocarbon linked mesogenic dimers are found to exhibit an additional nematic phase below the conventional uniaxial nematic phase as confirmed by x-ray diffraction. The phase produces unusual periodic stripe domains in planar cells. The stripes are found to be parallel to the rubbing direction (in rubbed cells) with a well-defined period equal to double the cell gap. The stripes appear without external electromagnetic field, temperature or thickness gradients, rubbing or hybrid alignment treatments. Simple modeling proposes a negative sign for at least one of the two elastic constants: splay and twist, as a necessary condition for the observed pattern.
Single Channel Vocal Separation Using Median Filtering And Factorisation Techniques, Derry Fitzgerald, Mikel Gainza
Single Channel Vocal Separation Using Median Filtering And Factorisation Techniques, Derry Fitzgerald, Mikel Gainza
Articles
This paper deals with the problem of the extraction of vocals from single channel audio signals containing both vocals and other instruments, including both pitched instruments and percussion instruments. A novel median filtering-based approach for the extraction of vocal tracks is described, which is simple and efficient to implement. Further improvements in separation quality are then obtained by the application of tensor factorisation techniques to further extract residual instruments from the vocal mix. Finally, a novel use of non-negative partial matrix cofactorisation is demonstrated as a means of further improving separation quality. Here the original single channel mixture is partially …
Protection Of Upqc Against The Load Side Short Circuits, Iurie Axente, Malabika Basu, Michael Conlon, Kevin Gaughan
Protection Of Upqc Against The Load Side Short Circuits, Iurie Axente, Malabika Basu, Michael Conlon, Kevin Gaughan
Articles
This study presents a protection scheme for protecting the series inverter of a unified power quality conditioner (UPQC). The proposed scheme protects the series inverter from overcurrents and overvoltages, which appear during short-circuit faults on the load side of the UPQC. The main protection element is a crowbar connected across the secondary of the series transformer and consists of a pair of antiparallel connected thyristors, which is governed by a simple Zener diode-based control circuit. In the case of an overvoltage, the crowbar short circuits the secondary of the transformer, thus removing the overvoltage and diverting the fault current from …
A Hybrid Fiber Optic Sensing System For Simultaneous Strain And Temperature Measurement And Its Application, Ginu Rajan, Karolina Milenko, Piotr Lesiak, Yuliya Semenova, Anna Boczkowska, Manjusha Ramakrishnan, Kazimierz Jedrzejewski, Andrzej Domanski, Tomasz Wolinski, Gerald Farrell
A Hybrid Fiber Optic Sensing System For Simultaneous Strain And Temperature Measurement And Its Application, Ginu Rajan, Karolina Milenko, Piotr Lesiak, Yuliya Semenova, Anna Boczkowska, Manjusha Ramakrishnan, Kazimierz Jedrzejewski, Andrzej Domanski, Tomasz Wolinski, Gerald Farrell
Articles
A hybrid fiber optic sensor by integrating polarimetric fiber sensors and fiber Bragg grating sensors for simultaneous strain and temperature measurement is presented in this paper. Two types of polarimetric fiber sensors are used; a Panda fiber and a polarization maintaining photonic crystal fiber. The polarimetric strain sensors give the average strain and temperature information, while the fiber Bragg grating sensors give localized strain information. Two applications of the proposed configuration are also demonstrated in this paper. In the composite materials three fiber sensors are used while for other engineering applications a temperature insensitive polarimetric fiber sensor can be used …
A Macrobending Singlemode Fiber Refractive Index Sensor For Low Refractive Index Liquids, Pengfei Wang, Yuliya Semenova, Yong Li, Qiang Wu, Gerald Farrell
A Macrobending Singlemode Fiber Refractive Index Sensor For Low Refractive Index Liquids, Pengfei Wang, Yuliya Semenova, Yong Li, Qiang Wu, Gerald Farrell
Articles
An all-fiber refractive index sensor with a simple configuration is proposed and investigated. The proposed fiber refractometer consists of a full-loop structure of bare high-bend loss singlemode fiber-1060XP, employing the well-known whispering gallery mode (WGM) effect induced by the evanescent wave excitation to measure the refractive index of an external medium. A competitive sensitivity is achieved (average 725.76nm/RIU at a bend diameter of 19.3mm) compared with other fiber-optic sensors, plus benefits resulting from simplicity, low cost and ease of fabrication.
Experimental Demonstration Of A Simple Displacement Sensor Based On A Bent Singlemode-Multimode-Singlemode (Sms) Fiber Structure, Qiang Wu, Yuliya Semenova, Pengfei Wang, Agus Hatta, Gerald Farrell
Experimental Demonstration Of A Simple Displacement Sensor Based On A Bent Singlemode-Multimode-Singlemode (Sms) Fiber Structure, Qiang Wu, Yuliya Semenova, Pengfei Wang, Agus Hatta, Gerald Farrell
Articles
A simple displacement sensor based on a bent singlemode-multimode-singlemode (SMS) fiber structure is proposed and experimentally investigated. The sensor offers a wider displacement range, not limited by the risk of fiber breakage, as well as a three-fold increase in displacement sensitivity by comparison with a straight SMS structure sensor. This sensor can be interrogated by either an optical spectral analyzer (OSA) or a ratiometric interrogation system: (1) if interrogated by an OSA assuming a resolution of 1 pm, it has a sensitivity of 28.2 nm for a displacement measurement range from 0 to 280 μm; (2) if interrogated by a …
A Liquid Crystal Coated Tapered Photonic Crystal Fiber Interferometer, Ginu Rajan, Sunish Mathews, Gerald Farrell, Yuliya Semenova
A Liquid Crystal Coated Tapered Photonic Crystal Fiber Interferometer, Ginu Rajan, Sunish Mathews, Gerald Farrell, Yuliya Semenova
Articles
An experimental investigation on liquid crystal coated tapered photonic crystal fiber (PCF) interferometer is presented in this paper. The interferometer is fabricated by tapering a small section of a PCF by collapsing the air holes and thinning down the air hole collapsed region to a micron size. Several interferometers are fabricated from different types of photonic crystal fibers and the temperature dependence studies are carried out to select an intrinsically temperature insensitive interferometer that can be used with liquid crystal (LC) materials. The properties of the LC materials to be used with the tapered PCF interferometers are also discussed. Temperature …
Bent Sms Fiber Structure For Temperature Measurement, Qiang Wu, Yuliya Semenova, Agus Hatta, Pengfei Wang, Gerald Farrell
Bent Sms Fiber Structure For Temperature Measurement, Qiang Wu, Yuliya Semenova, Agus Hatta, Pengfei Wang, Gerald Farrell
Articles
We have proposed a temperature sensor fabricated using a bent SMS fiber structure. Our experimental results show, that by comparison to a sensor based on a straight SMS fiber structure, this temperature sensor has a much higher sensitivity of 31.97 pm/°C over a temperature range from 20 to 80 °C based on the measurement of the mean 3 dB wavelength shift and offers a resolution of 0.1 °C for temperature range from 45 to 80 °C when demodulated by a simple ratiometric interrogation technique.
Use Of A Bent Single Sms Fiber Structure For Simultaneous Measurement Of Displacement And Temperature Sensing, Qiang Wu, Agus Hatta, Pengfei Wang, Yuliya Semenova, Gerald Farrell
Use Of A Bent Single Sms Fiber Structure For Simultaneous Measurement Of Displacement And Temperature Sensing, Qiang Wu, Agus Hatta, Pengfei Wang, Yuliya Semenova, Gerald Farrell
Articles
We have proposed the use of a single bent single-multiple-single mode (SMS) fiber structure to measure both displacement and temperature simultaneously and independently. Our experimental results show that this sensor has a sensitivity of 5.89 pm/μm for displacement and 11.6 pm/ºC for temperature.
A Voltage Sensor Based On A Singlemode-Multimode-Singlemode Fiber Structure, Agus Hatta, Yuliya Semenova, Ginu Rajan, Gerald Farrell
A Voltage Sensor Based On A Singlemode-Multimode-Singlemode Fiber Structure, Agus Hatta, Yuliya Semenova, Ginu Rajan, Gerald Farrell
Articles
A voltage sensor based on a singlemode-multimodesinglemode (SMS) fiber structure, attached to a piezoelectric (PZT), utilized in a ratiometric optical power measurement scheme is proposed. The elongation of the PZT due to an applied voltage induces a strain on the SMS fiber structure and in turn results in a change in the transmission loss response of the SMS fiber structure. It is found that at selected wavelengths, a strong voltage dependence for the transmission loss of the SMS fiber structure can be achieved. The voltage information can be obtained from the power ratio of the system, assuming the system is …
Optimum Design For Maximun Wavelength Resolution For An Edge Filter Based Ratiometric System, Qiang Wu, Ginu Rajan, Pengfei Wang, Yuliya Semenova, Gerald Farrell
Optimum Design For Maximun Wavelength Resolution For An Edge Filter Based Ratiometric System, Qiang Wu, Ginu Rajan, Pengfei Wang, Yuliya Semenova, Gerald Farrell
Articles
In this letter, we propose a high resolution temperature insensitive interrogation technique for FBG sensors where one FBG acts as an edge filter to interrogate a separate FBG sensor. A high resolution of better than 5 με in strain measurement range from 0 to 1100 με and the best resolution of better than 1 με were verified by experiments. An error of only ±2.2 με is achieved over a temperature range from 15 to 50 °C, indicating that this strain interrogation technique is temperature insensitive. Using an altered system configuration, the temperature was also measured simultaneously with a resolution better …
A Study Of The Effect Of The Position Of An Edge Filter Within A Ratiometric Wavelength Measurement System, Qiang Wu, Pengfei Wang, Yuliya Semenova, Gerald Farrell
A Study Of The Effect Of The Position Of An Edge Filter Within A Ratiometric Wavelength Measurement System, Qiang Wu, Pengfei Wang, Yuliya Semenova, Gerald Farrell
Articles
The effect of the position of an edge filter within a ratiometric wavelength measurement system was investigated based on three cases: (1) the reflected fibre Bragg grating (FBG) signal passes through both the reference arm and the edge filter arm, (2) the reflected FBG signal is connected directly to the edge filter arm and does not pass through the reference arm, (3) the edge filter sits in line with the FBG and thus the source power is filtered prior to reaching the FBG. Both numerical simulations and experimental results show that cases 1 and 2 have similar system performance whilst …
Strain Sensor Based On A Pair Of Single-Mode-Multimode-Single-Mode Fiber Structures In A Ratiometric Power Measurement Scheme, Agus Hatta, Yuliya Semenova, Qiang Wu, Gerald Farrell
Strain Sensor Based On A Pair Of Single-Mode-Multimode-Single-Mode Fiber Structures In A Ratiometric Power Measurement Scheme, Agus Hatta, Yuliya Semenova, Qiang Wu, Gerald Farrell
Articles
The strain and temperature dependencies of a step-index single-mode–multimode–single-mode (SMS) fiber structure are investigated numerically and experimentally. For intensity-based strain measurement using a single SMS fiber structure, at a selected wavelength, it is found that there is a high strain dependence, but also a temperature dependence that will induce strain measurement error. To minimize the temperature-induced strain measurement error, two SMS fiber structures are proposed and demonstrated in a ratiometric power measurement scheme; one SMS structure acts as the strain sensor, and the other SMS structure acts as the temperature monitor. The extracted temperature information is used to determine a …
Study Of The Effect Of Source Signal Bandwidth On Ratiometric Wavelength Measurement, Qiang Wu, Yuliya Semenova, Ginu Rajan, Pengfei Wang, Gerald Farrell
Study Of The Effect Of Source Signal Bandwidth On Ratiometric Wavelength Measurement, Qiang Wu, Yuliya Semenova, Ginu Rajan, Pengfei Wang, Gerald Farrell
Articles
We derive an analytic equation for a ratiometric wavelength measurement system and analyze the influence of the optical source signal bandwidth. Our investigation shows that in a particular optical sensing system, the higher the bandwidth of the optical signal, the better resolution the system will achieve. Experiments based on two types of optical signals (output signal of a tunable laser and a fiber Bragg grating) were carried out, and experimental results verified both the simulation results and the theoretical analysis.
Temperature Performance Of A Macrobending Single-Mode Fiber-Based Refractometer, Pengfei Wang, Yuliya Semenova, Qiang Wu, Zie Zheng, Gerald Farrell
Temperature Performance Of A Macrobending Single-Mode Fiber-Based Refractometer, Pengfei Wang, Yuliya Semenova, Qiang Wu, Zie Zheng, Gerald Farrell
Articles
The temperature dependence of polarization-dependent loss (PDL) for a macrobending standard single-mode fiber (SMF28) is investigated both theoretically and experimentally. The experimental results show an overall agreement with the proposed theoretical model over a temperature range from 0 C to 70 C. An SMF28-based edge filter is used as an example regarding temperature- dependent PDL performance. It is shown that the temperature variations have a significant influence on the polarization dependence of macrobending loss, and further impact on such a fiber bend loss edge filter used in a wavelength measurement application. It is also concluded that by using the proposed …
Simple Design Technique For A Triangular Fbg Filter Based On A Linearly Chirped Grating, Qiang Wu, Gerald Farrell, Yuliya Semenova
Simple Design Technique For A Triangular Fbg Filter Based On A Linearly Chirped Grating, Qiang Wu, Gerald Farrell, Yuliya Semenova
Articles
A novel and simple design technique for triangular spectrum response of fibre Bragg grating (FBG) is pre- 21 sented based on a linear chirped grating. It is shown that this method is fast and can give a straightfor- 22 ward solution to meet a design target. The numerical simulation examples verified the effectiveness of 23 the design method. A general approach to design for multichannel triangular spectral responses for 24 FBG filters is proposed, which provides a solution that achieves a minimum change of refractive index 25 for the fibre.
Dissociative Cdse/Zns Quantum Dot-Molecule Complex For Luminescent Sensing Of Metal Ions In Aqueous Solutions, A. V. Baranov, A. O. Orlova, V. G. Maslov, Yu. A. Toporova, E. V. Ushakova, A. Federov, M. V. Artemyev, T. S. Perova, Kevin Berwick
Dissociative Cdse/Zns Quantum Dot-Molecule Complex For Luminescent Sensing Of Metal Ions In Aqueous Solutions, A. V. Baranov, A. O. Orlova, V. G. Maslov, Yu. A. Toporova, E. V. Ushakova, A. Federov, M. V. Artemyev, T. S. Perova, Kevin Berwick
Articles
The optical properties of dissociative luminescent sensors based on a complex consisting of highly luminescent hydrophobic core/shell CdSe/ZnS quantum dots (QDs) and 1-(2-pyridilazo)-2-naphtol (PAN) molecules in organic solutions and a polymer film are reported. It is demonstrated, using Ni2+ and Co2+ ions as an illustrative example, that the QD/PAN sensor may have applications in the quantitative luminescent sensing of metal ions in aqueous solutions.
Double Quantum Dot Photoluminescence Mediated By Incoherent Reversible Energy Transport, S. Yu Kruchinin, A. V. Federov, A. V. Baranov, T. S. Perova, Kevin Berwick
Double Quantum Dot Photoluminescence Mediated By Incoherent Reversible Energy Transport, S. Yu Kruchinin, A. V. Federov, A. V. Baranov, T. S. Perova, Kevin Berwick
Articles
We present a theoretical study of the stationary photoluminescence of two, direct-gap, semiconductor nanocrystals, taking into account electronic excitation energy-transfer processes due to electrostatic interaction. The results obtained here allow for the incoherent reversible energy transport that occurs when the intraband relaxation rate in a quantum dot acceptor is comparable to, or less than, the energy-transfer rate. We investigate the secondary emission of two different electronic level schemes that can be realized experimentally, obtain analytical expressions for the luminescence differential cross section, and perform an analysis of its spectrum. It is shown that when excitation is not in resonance with …
Electric Field Induced Biaxiality And The Electro-Optic Effect In A Bent-Core Nematic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, U. Manna, J. K. Vij, C. Keith, C. Tschierske
Electric Field Induced Biaxiality And The Electro-Optic Effect In A Bent-Core Nematic Liquid Crystal, Mamatha Nagaraj, Yuri Panarin, U. Manna, J. K. Vij, C. Keith, C. Tschierske
Articles
We report the observation of a biaxial nematic phase in a bent-core molecular system using polarizing microscopy, electro-optics, and dielectric spectroscopy, where we find that the biaxiality exists on a microscopic scale. An application of electric field induces a macroscopic biaxiality and in consequence gives rise to electro-optic switching. This electro-optic effect shows significant potential in applications for displays due to its fast high-contrast response. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field. © 2010 American Institute of Physics.