THE GENERALIZED LEVEQUE SOLUTION

In the conventional Leveque analysis, three assumptions are made: (a) that the curvature effect is negligible; (b) that the velocity profile can be linearized; and (c) that the symmetry condition can be replaced by an infinity condition. In the present, more exact, analysis all three assumptions have been relaxed by introducing a new transverse coordinate. The results indicate that the curvature effect is quite important and that the assumption of an infinity condition is reasonable. Consequently, results obtained by neglecting the curvature effects should be used with caution.     

Investigation on mechanical properties of woven alovera/sisal/kenaf fibres and their hybrid composites

The go-green concept results in multipoint focus towards materials made from nature; easily decomposable and recyclable polymeric materials and their composites along with natural fibres ignited the manufacturing sectors to go for higher altitudes in engineering industries. This is due to the health hazard and environmental problems faced in manufacturing and disposal of synthetic fibres. This study was undertaken to analyse the suitability of new natural fibre as an alternative reinforcement for composite materials. In this paper, tensile, flexural and impact test is made for the woven alovera and kenaf (AK), sisal and kenaf (SK), alovera, sisal and kenaf fibre hybrid epoxy composites (ASK). The composite laminates are made through a hand-layup process. The surface analysis is studied through scanning electron microscopy. From the investigation the SK hybrid composite shows good tensile property, AK hybrid composite shows better flexural property and the best impact strength is observed for ASK hybrid composite. The natural fibres slowly replace the synthetic fibres from its environmental impact, marching towards a revolution in engineering materials.     

Individual learning of coordination knowledge

Abstract. Social agents, both human and computational, inhabiting a world containing multiple active agents, need to coordinate their activities. This is because agents share resources, and without proper coordination or ‘rules of the road’, everybody will be interfering with the plans of others. As such, we need coordination schemes that allow agents to effectively achieve local goals without adversely affecting the problem-solving capabilities of other agents. Researchers in the field of Distributed Artificial Intelligence (DAI) have developed a variety of coordination schemes under different assumptions about agent capabilities and relationships. Whereas some of these researchers have been motivated by human cognitive biases, others have approached it as an engineering problem of designing the most effective coordination architecture or protocol. We evaluate individual and concurrent learning by multiple, autonomous agents as a means for acquiring coordination knowledge. We show that a uniform reinforcement learning algorithm suffices as a coordination mechanism in both cooperative and adversarial situations. Using a number of multi-agent learning scenarios with both tight and loose coupling between agents and with immediate as well as delayed feedback, we demonstrate that agents can consistently develop effective policies to coordinate their actions without explicit information sharing. We demonstrate the viabilityof using both the Q-learning algorithm and genetic algorithm based classifier systems with different pay-off schemes, namely the bucket brigade algorithm (BBA) and the profit sharing plan (PSP), for developing agent coordination on two different multi-agent domains. In addition, we show that a semi-random scheme for action selection is preferable to the more traditional fitness proportionate selection scheme used in classifier systems.     

MEASUREMENT OF PARTICLE VELOCITY IN PNEUMATIC TRANSPORT OF COAL USING CROSS-CORRELATION TECHNIQUE

ABSTRACT

Particle velocity has been determined experimentally in a solid-gas flow using the cross-correlation technique. Signals from two flow-monitoring devices, one based on the measurement of the dielectric constant of coal/air and the other based on the rate of static charge transfer technique, have been utilized to determine the cross-correlation function and hence the time delays between the signals. Other pertinent fluid dynamic parameters have been evaluated using experimentally determined particle velocities.     

RADIAL FLOW HOLLOW FIBERREVERSE OSMOSIS: EXPERIMENTS AND THEORY

The performance of a hollow fiber reverse osmosis system is studied both theoretically and experimentally. Experiments were carried out for applied pressure ranging from 200 to 400 psig, feed rates varying from 75 to 380 cc/sec and for feed concentrations up to 34,000 ppm of sodium chloride.

A mathematical model is proposed to predict productivity, ?, and product concentration, θ_p. The model involves solving membrane transport equations simultaneously with the hydrodynamic equations. The solubility-diffusion-imperfection, or pore diffusion model, is used to describe solute and solvent transport across the membrane. The axial gradients of shell side concentration, neglected in previous investigations, are taken into account. The differential equations are solved numerically by the 4th Order Runge-Kutta method.

Predicted values of ? and θ_p agree within 8% and 17% respectively, with experimental data over the entire range of operating conditions. However, membrane transport coefficients were found to be concentration dependent.

An approximate analysis shows that the concentration polarization is negligible in present day hollow fiber systems.     

INFECTIVE DOSE OF FOODBORNE PATHOGENS IN VOLUNTEERS: A REVIEW

Risk assessment and impact of foodborne pathogens on the health of different populations was one of the goals identified in the Presidential Food Safety Initiative three-year plan. This entailed estimation of dose-response relationship for foodborne pathogens to humans, either by feeding studies or from outbreaks. For certain pathogens, such as Listeria monocytogenes and Escherichia coli O157:H7, there are no feeding studies due to ethical reasons, and the results from outbreaks are normally used to estimate the infectious dose. The focus of this review is to compile dose-response information in volunteers for several foodborne pathogens including Salmonella, Shigella spp. , Campylobacter jejuni, Vibrio spp. , Escherichia coli, Cryptosporidium parvum and Entamoeba coli. The infectious dose for different serovars of Salmonella and strains of E. coli was quite large (> 10⁵ organisms), while the infectious dose for some Shigella spp. seemed to be as low as less than 10 organisms. Toxigenic V. cholerae (O1 and O139 serotypes) were infective at a dose of 10⁴ organisms; a non-O1 strain was infective at a much higher dose (10⁶ organisms). C. jejuni, C. parvum and Entamoeba coli appeared to have infectious doses as low as 500 organisms, 10 oocysts, and 1 cyst, respectively. The infectious dose and the dose response are dependent upon the strains used, and the age and physical condition of the individuals, and can therefore show wide variations. In addition, since many of the volunteer studies are carried out by feeding the organisms in a nonfood matrix after neutralizing the stomach acidity, results obtained may not reflect the true dose response.     

Visualization and Modeling of Flow Boiling of R-134A in Minichannels with Transverse Ribs

This research was undertaken to investigate the flow boiling of R-134a in minichannels with transverse ribs. The test channel consisted of two parallel plates; the lower plate was heated, and the upper plate was adiabatic. A number of transverse ribs were deployed along the lower plate. The hydraulic diameter of the channel was 1.93 mm. In these experiments, the main test parameters were mass flux, saturation temperature, heat flux, and average vapor quality. With these parameters, the convective and boiling numbers ranged from 0.04 to 0.90 and 7.49 × 10^{? 4} to 8.98 × 10^{? 4} , respectively. Of a total of 60 data points recorded, 78% of the data fell in the convective boiling region, while the remaining 22% were in the nucleate boiling region. A two-equation model was fit to a total of 60 experimental data, resulting in a correlation that predicted 58 data points to within ± 10%.