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Articles 541 - 564 of 564

Full-Text Articles in Electrical and Computer Engineering

Micro-Raman Study Of Stress Distribution Generated In Silicon During Proximity Rapid Thermal Diffusion, M. Nolan, T. Perova, R. A. Moore, C. J. Moore, Kevin Berwick, H. S. Gamble Jan 2000

Micro-Raman Study Of Stress Distribution Generated In Silicon During Proximity Rapid Thermal Diffusion, M. Nolan, T. Perova, R. A. Moore, C. J. Moore, Kevin Berwick, H. S. Gamble

Articles

proximity rapid thermal diffusion (RTD). A compressive stress was found on the whole silicon wafer after 15 s RTD. After 165 s RTD, the distribution of the stress across the wafer was found to be different: compressive at the edge and tensile at the middle. Thermal stress was relieved in the RTD wafers via slip dislocations. These slip dislocations were observed in the product wafers using optical microscopy. Slip lines propagated from the wafer edge to the wafer centre in eight preferred positions of maximum induced stress. The thermally induced stress and the slip dislocation density increased with time spent …

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Investigation Of The Thickness Mode In Surface Stabilized Ferroelectric Liquid Crystal Cells, O.E. Kalinovskaya, J.K. Vij, Yu. V. Tretyakov, Yuri Panarin, Yu. P. Kalmykov Jan 1999

Investigation Of The Thickness Mode In Surface Stabilized Ferroelectric Liquid Crystal Cells, O.E. Kalinovskaya, J.K. Vij, Yu. V. Tretyakov, Yuri Panarin, Yu. P. Kalmykov

Articles

Dielectric properties of surface stabilized ferroelectric liquid crystal (SSFLC) cells have been investigated both experimentally and theoretically. The thickness mode is found to consist of two relaxation processes. A decomposition of an analytical solution of the complex dielectric permittivitye(v) in terms ofthese processesis given. Theexperimental results showagreement with theory and lead to the conclusion that the thickness mode can be separated into two processes. It has been found that the ratio of the dielectric strengths for the two processes depends on the cell thickness, and that the ratio of their frequencies is approximately equal to 10. The lower frequency process …

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The Dynamic Properties Of 5cb Filled With Aerosil Particles Investigated By Pcs, F.M. Aliev, M. Kreuzer, Yuri Panarin Jan 1999

The Dynamic Properties Of 5cb Filled With Aerosil Particles Investigated By Pcs, F.M. Aliev, M. Kreuzer, Yuri Panarin

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Nematic liquid crystal filled with Aerosil particles, a prospective composite material for optoelectronic application, has been investigated by static light scattering and Photon Correlation Spectroscopy (PCS). The Aerosil particles in filled nematic liquid crystals (FN) form a network structure with LC domains about 2500 Å in size with a random distribution of the director orientation of each domain. We found that the properties of 5CB are considerably affected by the network. The N-I phase transition in filled 5CB was found to be smeared out and depressed. PCS experiments show that two new relaxation processes appear in filled 5CB in addition …

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The Appearance Of Ferrielectric Phases In Confined Liquid Crystal Studied By Photon Correlation Spectroscopy, Yuri Panarin, Fouad M. Aliev, Charles Rosenblatt Jan 1999

The Appearance Of Ferrielectric Phases In Confined Liquid Crystal Studied By Photon Correlation Spectroscopy, Yuri Panarin, Fouad M. Aliev, Charles Rosenblatt

Articles

The influence of confinement on the dynamic properties and appearance of ferrielectric phases has been investigated by dynamic light scattering, performed in the bulk AFLC as well as confined in 200 8, and 2000 8, cylindrical pores. The analysis of the experimental results shows that the ferrielectric phases are not formed in 200 A pores, while they appear in 2000 8, pores as well as in bulk.

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The Dynamic Properties Of Confined Antiferroelectric Liquid Crystal Investigated By Photon Correlation Spectroscopy, Yuri Panarin, C. Rosenblatr, F.M. Aliev Jan 1999

The Dynamic Properties Of Confined Antiferroelectric Liquid Crystal Investigated By Photon Correlation Spectroscopy, Yuri Panarin, C. Rosenblatr, F.M. Aliev

Articles

Dynamic light scattering was used to examine ferrielectric liquid crystalline phases in porous media. Whereas in larger pores (200 Å) ferrielectric phases were observed, they were not found in the smallest pores (200 Å). Additionally, the temperatures of SmC - SmA phase transition were found to be suppressed in the pores relative to bulk, while SmCA - SmCγ phase transition is not affected by the confinement. These observations have been explained by the structural aspects of antiferroelectric liquid crystalline materials in a confined geometry and show the importance of long range electrostatic interaction for existence of ferrielectric phases.

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The Investigation Of The Relaxation Process In Antiferroelectric Liquid Crystals By Electro-Optic Spectroscopy, Yuri Panarin, O. Kalinovskaya, J.K. Vij Jan 1998

The Investigation Of The Relaxation Process In Antiferroelectric Liquid Crystals By Electro-Optic Spectroscopy, Yuri Panarin, O. Kalinovskaya, J.K. Vij

Articles

Electrooptic spectroscopy of an antiferroelectric liquid crystal is carried out over a range of frequencies from 1 Hz to 100 kHz. In the antiferroelectric SmCA phase two relaxation processes are found, one at the fundamental frequency of a mode and the second at twice the frequency of a different mode. A comparison of the results of the electro-optic spectroscopy with a theoretical study of the motion of the director of an antiferroelectric helix subject to a weak alternating field enables a determination of the origin of the relaxation processes in antiferroelectric phases. © 1998 American Institute of Physics.

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Observation And Investigation Of The Ferrielectric Subphase With High Qt Parameter, Yuri Panarin, O. Kalinovskaya, J.K. Vij, J.W. Goodby Jan 1997

Observation And Investigation Of The Ferrielectric Subphase With High Qt Parameter, Yuri Panarin, O. Kalinovskaya, J.K. Vij, J.W. Goodby

Articles

Dielectric relaxation processes in an antiferroelectric liquid crystal (AFLC) have been investigated over a wide range of frequencies from 1 Hz to 1 GHz. The AFLC under investigation possesses a variety of different ferrielectric, ferroelectric, and antiferroelectric phases. Dielectric and polarization measurements under direct bias voltage have been made with a view to clarifying the origin of the high-temperature ferrielectric phase, which appears between the AF and smectic-C phases. This phase is assigned to an unstable ferrielectric phase with qT parameter greater than 1/2 (according to the Ising model) or a doubly modulated incommensurate phase (according to the expanded Landau …

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Observation And Investigation Of The Ferrielectric Subphase With Qt>1/2, Yuri Panarin, O. Kalinovskaya, J. K. Vij Jan 1997

Observation And Investigation Of The Ferrielectric Subphase With Qt>1/2, Yuri Panarin, O. Kalinovskaya, J. K. Vij

Articles

The high-temperature femelectric phase with qT > 1/2 has been found to exist in a antiferroelectric liquid crystal. This phase has been identified using dielectric spectroscopy and conoscopy.

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Investigation Of The Ferrielectric Subphase With Qt>1/2 Under Bias Voltage, Yuri Panarin, O.E. Kalinovskaya, J.K. Vij Jan 1997

Investigation Of The Ferrielectric Subphase With Qt>1/2 Under Bias Voltage, Yuri Panarin, O.E. Kalinovskaya, J.K. Vij

Articles

The properties of Femelectric phase with qT > 112 have been investigated using broadband dielectric spectroscopy and polarization measurements under the bias voltage. The field -induced sequence of phase transitions is found to be different fiom those of the conventional femelectric phases with qTS 112

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A Study Of Antiferroelectric Liquid Crystals Using The Pyroelectric Technique, J.W. O'Sullivan, Yuri Panarin, J.K. Vij, A.J. Seed, M. Hird, J.W. Goodby Jan 1997

A Study Of Antiferroelectric Liquid Crystals Using The Pyroelectric Technique, J.W. O'Sullivan, Yuri Panarin, J.K. Vij, A.J. Seed, M. Hird, J.W. Goodby

Articles

Antiferroelectric liquid crystals are studied using the pyroelecmc technique. The effects of temperature and applied voltage on the pyroelectric signal are examined. The pyroelecmc signal can detect phase changes that occur due to temperature and bias voltage. A high temperature femelecmc phase FiLC is found and the stability of this phase under different bias voltages is examined

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The People: The Least Accountable Branch, Marci A. Hamilton Jan 1997

The People: The Least Accountable Branch, Marci A. Hamilton

Articles

No abstract provided.

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Theoretical Investigations Of Electro-Optical Synchonisation Of Self-Pulsating Laser Diodes, A. Egan, P. Rees, J. O'Gorman, M. Harley-Stead, Gerald Farrell, Joe Hegarty, P. Phelan Jan 1996

Theoretical Investigations Of Electro-Optical Synchonisation Of Self-Pulsating Laser Diodes, A. Egan, P. Rees, J. O'Gorman, M. Harley-Stead, Gerald Farrell, Joe Hegarty, P. Phelan

Articles

The synchronisation mechanism of selfpulsating laser diodes is determined and it is shown how this results in a frequency-dependent phase difference between the electrical input and optical output. The time-to-lock of the electrical input to the optical output is examined, particularly with regard to the importance of the initial phase difference between the signals. The effect of synchronisation on timing jitter in self pulsating lasers is also investigated.

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Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell Dec 1994

Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell

Articles

The effect of short- and long-term frequency instability in self pulsation on all-optical synchronization using a twin-section laser diode is experimentally investigated. Short-term frequency instability broadens the unlocked full width at half maximum (FWHM) of the fundamental of the rf spectrum of the self-pulsating laser diode. We show experimentally that the value of the unlocked FWHM, and thus the level of short-term instability, has a direct effect on the optical power required to maintain synchronization. A novel means of reducing the FWHM is presented based on a reflective transmission line stub connected to the absorber of the twin-section self-pulsating laser …

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Comparison Of Self Pulsation In Multisection Lasers With Distributed Feedback And Intracavity Satuarable Absorbers, P. Phelan, D. Mcdonald, A. Egan, Joe Hegarty, R. O'Dowd, Gerald Farrell, S. Lingren Jan 1994

Comparison Of Self Pulsation In Multisection Lasers With Distributed Feedback And Intracavity Satuarable Absorbers, P. Phelan, D. Mcdonald, A. Egan, Joe Hegarty, R. O'Dowd, Gerald Farrell, S. Lingren

Articles

The authors report a comparison of the self-pulsing characteristics of two types of semiconductor laser. They show that the self-pulsing frequency of the DFB laser is decoupled from the resonance frequency. They discuss the various characteristics, their significance in relation to optical synchronisation, and use the results to suggest a possible explanation for the mechanism for self-pulsation in the DFB laser.

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All Optical Timing Extraction With Frequency Division Using A Twin Section Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty, J. A. Shields Jan 1993

All Optical Timing Extraction With Frequency Division Using A Twin Section Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty, J. A. Shields

Articles

All-optical timing extraction from a coded line signal with division of the extracted clock frequency is demonstrated using a single twin-section self-pulsating laser diode. Either the bit-rate clock or a submultiple of the bit-rate clock can be extracted, depending only on the dc biases applied to the self-pulsating laser diode. Timing extraction is carried out for the first time without optical injection locking of the self-pulsating laser diode by the optical data source.

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The Influence Of The Unlocked Characteristics Of A Self-Pulsating Laser Diode On Synchronisation, Gerald Farrell, P. Phelan, Joe Hegarty Jan 1993

The Influence Of The Unlocked Characteristics Of A Self-Pulsating Laser Diode On Synchronisation, Gerald Farrell, P. Phelan, Joe Hegarty

Articles

All-optical synchronization and timing extraction based on self-pulsating twin section lasers has been demonstrated. We investigate the variation of the unlocked full-width at- half-maximum of the fundamental of the RF spectrum of a self-pulsating laser diode. We show for the first time that the value of the unlocked FWHM has a direct influence on the power required to maintain synchronization. We also show that the variation of the FWHM with frequency is dependent on the slope of the absorber bias versus self-pulsation frequency characteristic. The results have important implications for the design and selection of self-pulsating laser diodes for synchronization …

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All-Optical Timing Extraction With Frequency Division Using A Twin-Section Laser Diode, Gerald Farrell, Paul Phelan, Joe Hegarty, J. Shields Jan 1993

All-Optical Timing Extraction With Frequency Division Using A Twin-Section Laser Diode, Gerald Farrell, Paul Phelan, Joe Hegarty, J. Shields

Articles

All-optical timing extraction from a coded line signal with division of the extracted clock frequency is demonstrated using a single twin-section self-pulsating laser diode. Either the bit-rate clock or a submultiple of the bit-rate clock can be extracted, depending only on the DC biases applied to the self-pulsating laser diode. Timing extraction is carried out for the first time without optical injection locking of the self-pulsating laser diode by the optical data source

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All Optical Synchronisation With Frequency Division Using A Self Pulsating Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty Jan 1992

All Optical Synchronisation With Frequency Division Using A Self Pulsating Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty

Articles

A master optical clock from a mode locked laser is distributed to two slave twin section lasers. One slave laser divides the optical modulation frequency by 2, the other slave laser multiplies the frequency by 2. It is also possible to vary the multiplication4ivision ratio in a slave laser using only DC control of the absorber of the twin section laser.

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All Optical Clock Distribution With Synchronous Frequency Division And Multiplication, Gerald Farrell, P. Phelan, Joe Hegarty Jan 1992

All Optical Clock Distribution With Synchronous Frequency Division And Multiplication, Gerald Farrell, P. Phelan, Joe Hegarty

Articles

A master optical clock from a mode locked laser is distributed to two slave twin section lasers. One slave laser divides the optical modulation frequency by 2, the other slave laser multiplies the frequency by 2. It is also possible to vary the multiplication4ivision ratio in a slave laser using only DC control of the absorber of the twin section laser.

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All-Optical Synchronisation And Multiplication Of The Frequency Of Mode-Locked Signals, P. Phelan, Gerald Farrell, Joe Hegarty Jan 1992

All-Optical Synchronisation And Multiplication Of The Frequency Of Mode-Locked Signals, P. Phelan, Gerald Farrell, Joe Hegarty

Articles

We report all-optical synchronized multiplication by rational fractions of the modulation frequency of optical signals in self-pulsing two-section semiconductor laser diodes. The effect is based on the overlap of harmonics of the input signal with harmonics of the self-pulsation. We illustrate this new generic function with modelocked inputs rich in harmonics were fractions of 1,2, and 3 / 2 are generated, and we identify a number of applications for this effect.

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Self-Pulsation Operating Regime For The Absorber Of A Twin Section Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty Jan 1991

Self-Pulsation Operating Regime For The Absorber Of A Twin Section Laser Diode, Gerald Farrell, P. Phelan, Joe Hegarty

Articles

The voltage-current characteristic of the absorber of a twin section laser diode is investigated as a function of the gain section current. For self pulsation to occur the absorber must be operated within a specific region of the voltage-current characteristics. This region only exists for absorber voltage current characteristics which contain an S-shaped negative resistance.

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Bistabiity By Induced Waveguiding In Coupled Semiconductor Lasers, Daniel Heffernan, J. Mcinerney, L. Reekie, D. Bradley Jan 1985

Bistabiity By Induced Waveguiding In Coupled Semiconductor Lasers, Daniel Heffernan, J. Mcinerney, L. Reekie, D. Bradley

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Recently, McInerney, Reekie, and Bradley observed bistability in twin diode GaAs/GaAlAs injection lasers in an external cavity when both diodes were above threshold. We show that this bistability may be explained by a form of self-focusing which is produced by induced waveguiding in the wide stripe lasers. A detailed analysis is performed on a standard model of these diodes in an external cavity. We have found very good agreement between theory and experiment.

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Proposal For A Digital Pseudorandom Number Generator, C. Downey Jan 1984

Proposal For A Digital Pseudorandom Number Generator, C. Downey

Articles

A digital hardware implementation of a linear congruential sequence generator using shift and add techniques of multiplication is described. The sequence is of long period, low serial correlation and is rectangularly distributed. The method has certain advantages over conventional feedback shift register techniques.

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Algorithms For The Solution Of Systems Of Coupled Second-Order Ordinary Differential Equations, Brendan O'Shea Jan 1978

Algorithms For The Solution Of Systems Of Coupled Second-Order Ordinary Differential Equations, Brendan O'Shea

Articles

Several step-by-step methods for the computer solution systems of coupled second-order ordinary differential equations, are examined from the point of view of efficiency “time-wise” and “storage-wise”. Particular reference is made to a system arising in the close-coupling approximation of the Schroedinger equation. The stability of the solution is also considered.

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