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Articles 4381 - 4410 of 4606

Full-Text Articles in Engineering

Repointing Mortars For Conservation Of A Historic Stone Building In Trinity College, Dublin, Aidan Duffy, Tim P. Cooper, Simon H. Perry Jan 1993

Repointing Mortars For Conservation Of A Historic Stone Building In Trinity College, Dublin, Aidan Duffy, Tim P. Cooper, Simon H. Perry

Articles

With atmospheric pollution causing building stone to decay at accelerated rates, conservation of historic stone monuments is becoming an increasingly important issue. Mortar joints have a marked effect on how moisture moves in a wall and, hence, on how the wall weathers. Not only does mortar bind stones together, but also a good mortar will prevent the ingress of moisture (and pollutants), enable the buildings to dry out, accommodate movement and will not act as a source of harmful chemicals capable of attacking the surrounding stone. Thus, poor mortar can have deleterious effects on the stonework. This paper, which is …


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 …


Bs News Jan 1993

Bs News

Building Services Engineering

No abstract provided.


A Comparison Of Techniques For Time Delay Estimation, Aidan O'Dwyer Jan 1993

A Comparison Of Techniques For Time Delay Estimation, Aidan O'Dwyer

Conference papers

This paper reviews some of the techniques used for the identification of unknown lumped time delays in single input, single output (SISO) control systems and evaluates a number of these techniques in simulation and in implementation. Both off line and on line identification techniques are considered.


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


Hysteresis And Anchoring Energy In Ferroelectric Liquid Crystals, Yuri Panarin Jan 1993

Hysteresis And Anchoring Energy In Ferroelectric Liquid Crystals, Yuri Panarin

Articles

The frequency dispersion of the coercive force of Ferroelectric Liquid Crystals (FLC) cells has been detected and examined in the range of infralow (lower than 0.1 Hz) frequencies. To clarify the low-frequency dispersion, the model has been suggested, based on the arrangement of free charges and well describing the experimental curves. The method for determination of the energy of FLC anchoring at the surface, developed on the basis of the static hysteresis loop, has been proposed. The dependence of bistability and the anchoring energy upon the orientant layer thickness has experimentally been investigated.


Bs News Dec 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Nov 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Sep 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Jul 1992

Bs News

Building Services Engineering

No abstract provided.


A Virtual-System Concept For Exergy Analysis Of Flow Network Plant; Part I: Principles, Jim Mcgovern, Francis O'Toole Jun 1992

A Virtual-System Concept For Exergy Analysis Of Flow Network Plant; Part I: Principles, Jim Mcgovern, Francis O'Toole

Conference Papers

A new type of virtual system, named a flow constraint system (FCS), is proposed to facilitate, clarify, and simplify exergy analyses of plant that involve material flow networks. The need for the virtual system is outlined and the concept is demonstrated by applying it to a CHP steam cycle. The FCS concept allows the physical constraints on the exergy interactions associated with flow streams to be taken into account fully. It also simplifies the treatment of bifurcations in material flows and considerably reduces the need for absolute exergy evaluations. The new concept follows from the work already published by the …


A Virtual-System Concept For Exergy Analysis Of Flow Network Plant; Part Ii: Exergetic And Exergonomic Analysis Illustration, Jim Mcgovern, Francis O'Toole Jun 1992

A Virtual-System Concept For Exergy Analysis Of Flow Network Plant; Part Ii: Exergetic And Exergonomic Analysis Illustration, Jim Mcgovern, Francis O'Toole

Conference Papers

This paper is a continuation of Part I — Principles, to which it refers extensively. The virtual system concept and the methodology introduced in Part I are illustrated by means of a numerical example. This is an exergetic and exergoeconomic analysis of the CHP steam plant that was described in Part I without operating values and parameters. Matrix methods developed by Valero et al. (1986) are adapted to the new concept. It is shown that these methods are made simpler and less subjective. Bond-graph-type diagrams for exergetic and economic costs are presented.


Bs News May 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Apr 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Mar 1992

Bs News

Building Services Engineering

No abstract provided.


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.


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.


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.


Bs News Jan 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Jan 1992

Bs News

Building Services Engineering

No abstract provided.


Bs News Nov 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News Oct 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News Sep 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News Jul 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News Jun 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News May 1991

Bs News

Building Services Engineering

No abstract provided.


Bs News Mar 1991

Bs News

Building Services Engineering

No abstract provided.


The Use Of Expert Systems In Demand Forecasting, Edward Sweeney Jan 1991

The Use Of Expert Systems In Demand Forecasting, Edward Sweeney

Books/Book chapters

No abstract provided.


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.


Shadow Casting Phenomena At Newgrange, Frank Prendergast Jan 1991

Shadow Casting Phenomena At Newgrange, Frank Prendergast

Articles

A digital model of the Newgrange passage tomb and surrounding ring of monoliths known as the Great Circle is used to investigate sunrise shadow casting phenomena at the monument. Diurnal variation in shadow directions and lengths are analysed for their potential use in the Bronze Age to indicate the passage of seasonal time. Computer-aided simulations are developed from a photogrammetric survey to accurately show how three of the largest monoliths, located closest to the tomb entrance and archaeologically coded GC1, GC-1 and GC-2, cast their shadows onto the vertical face of the entrance kerbstone, coded K1. The phenomena occur at …