Modeling liquid jet breakup in high speed cross-flow with finite-conductivity evaporation

Numerical study of liquid atomization/spray process in a high speed cross-flow is described in this paper. Due to the strong aero-thermal dynamics/spray interaction, droplet evaporation process plays an important role even for non-chemical reacting cold-flow systems. Further to the development of the finite-conductivity spray evaporation model, an improved drag coefficient correlation which would capture the spray phenomenon more accurately specifically for application to high speed flow applications was also incorporated. Numerical results indicated that jet penetration increased rapidly in the vicinity of the injector exit and then gradually increased due to increase in the drag of the air stream. The predicted results were reasonably comparable to measured data and showed more accurate comparisons to that of the infinite-conductivity model.     

Pressure measurement in a blow-down wind tunnel

An automatic system for steady pressure measurement in a small hand-controlled supersonic wind tunnel is described. The ratio of model surface pressure to tunnel blowing pressure was measured using a Scanivalve controlled by a small digital computer. The software contained provision for the rejection of samples which were not sufficiently steady, and a transducer calibration routine was included to enable a variety of transducers to be used with the system. Typically, 18 pressure tappings could be sampled in a 50 s run (including start-up time) with an error of ±2% in the pressure ratio. The system should be applicable to any situation where run times are limited and difficulty is experienced in maintaining precise control over blowing pressure.     

The validity of ultrasonic pulse velocity testing of in-place concrete for strength

It is generally accepted that the use of ultrasonic methods for assessment of concrete suffers many disadvantages, particularly where a strength estimation is required. The absence of alternative non-destructive methods capable of giving significantly better results, however, means that despite these difficulties ultrasonics have a valuable role to play, especially in the field of in-place evaluation of structural concrete. It is thus worthwhile to examine in some detail those factors having a major influence on ‘field’ results, with the aim of assessing the confidence with which they may be viewed.     

Efficient architectures for sparsely-connected high capacity associative memory models

In physical implementations of associative memory, wiring costs play a significant role in shaping patterns of connectivity. In this study of sparsely-connected associative memory, a range of architectures is explored in search of optimal connection strategies that maximize pattern-completion performance, while at the same time minimizing wiring costs. It is found that architectures in which the probability of connection between any two nodes is based on relatively tight Gaussian and exponential distributions perform well and that for optimum performance, the width of the Gaussian distribution should be made proportional to the number of connections per node. It is also established from a study of other connection strategies that distal connections are not necessary for good pattern-completion performance. Convergence times and network scalability are also addressed in this study.     

Improving reinforcement learning in stochastic RAM-based neural networks

RAM-based neural networks are designed to be efficiently implemented in hardware. The desire to retain this property influences the training algorithms used, and has led to the use of reinforcement (reward-penalty) learning. An analysis of the reinforcement algorithm applied to RAM-based nodes has shown the ease with which unlearning can occur. An amended algorithm is proposed which demonstrates improved learning performance compared to previously published reinforcement regimes.     

Modeling Chirp and Phase Inversion in Wavelength Converters based on Symmetrical MZI-SOAs for use in All-Optical Networks

All-optical wavelength conversion based on multi-section semiconductor optical amplifiers (SOAs) in a symmetrical Mach-Zehnder interferometer (SMZI) is modeled for use in optical networks. It incorporates an enhanced SOA model that is implemented using the time domain transfer matrix approach and hence the overall numerical model determines simultaneously the wavelength and gain parameters for the wavelength converter. The overall model accurately predicts the optimal conditions for the SMZI arrangement in order to achieve the best results for the chirp, the phase inversion and the converted probe signal power. It is also demonstrated that large chirp and mismatch of the phase inversion reduces the eye opening ratio (EOR) which can seriously affect the performance of the wavelength converter to be used as a sub-system component in all-optical networks.     

Chirp Control of an Electroabsorption Modulator to be used for Regeneration and Wavelength Conversion at 40 Gbit/s in All-Optical Networking

Chirp control to produce low or negative values of chirp at the output of an electroabsorption modulator (EAM) is an important mechanism for reducing the signal degradation due to chromatic dispersion in high-speed transmission over standard single-mode fibre. An analytical model for the chirp performance of an EAM capable of optical regeneration and simultaneous wavelength conversion operating at 40 Gbit/s is derived. A chirp control approach is identified using this model by exploring the tradeoff between the α-parameter describing the chirp factor (based on the nonlinear absorption coefficients) and bias voltage requirements of an EAM. In particular, an optimum range of bias voltage is determined to ensure reduced chirp operation when a two-tone signal (i.e., comprised of bias and modulating voltages) is applied to the EAM. It is also demonstrated for large signal operation at 40 Gbit/s that the optimum range of reverse bias voltage is between 0 and 2 V to obtain low values for the chirp factor (between +1 and −2) in order to facilitate the necessary chirp control in all-optical networking. In addition, it is identified that at 40 Gbit/s higher positive values of the second- and third- order nonlinear coefficients of chirp must be avoided when operating at reverse bias voltages less than 1 V.     

An experimental and computational study of the aerodynamic and passive ventilation characteristics of small livestock trailers

This paper presents a combined experimental and computational study of the aerodynamics and passive ventilation characteristics of small livestock trailers within which the majority of animals in the United Kingdom are transported to market. Data obtained from a series of wind tunnel experiments using a 1/7th scale model of a simplified towing vehicle and trailer are compared with complementary computational fluid dynamics (CFD) analyses, based on steady-state RANS turbulence modelling, of the coupled external/internal flow field. Good agreement between the two is obtained everywhere except at the rear of the trailer. Since the internal flow field and overall ventilation rates contribute to animal welfare, CFD is used to generate detailed internal flow fields and air residence times for use within an overall welfare assessment. The results demonstrate that the flow fields in the upper and lower decks differ significantly and that ventilation rates are much larger and air residence times much smaller on the upper deck.     

FRPs and FOSs lead to innovation in Canadian civil engineering structures

Modern and innovative technologies, developed as part of ISIS Canada activities, are described; these technologies involve new building materials, comprising polymers and super-strong fibers, and innovative sensors incorporating fiber optics. It is argued that the ISIS technologies will pave the way to innovation as well as for rehabilitating and rejuvenating Canada's aging and fast-crumbling infrastructure in a cost-effective manner. This article chronicles the latest developments of ISIS technologies.