Thermodynamic optimization of a solar system for cogeneration of water heating and absorption cooling

This paper presents a contribution to understanding the behavior of solar‐powered air conditioning and refrigeration systems with a view to determining the manner in which refrigeration rate, mass flows, heat transfer areas, and internal architecture are related. A cogeneration system consisting of a solar concentrator, a cavity‐type receiver, a gas burner, and a thermal storage reservoir is devised to simultaneously produce heat (hot water) and cooling (absorption refrigerator system). A simplified mathematical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, mass and heat transfer, is developed. The proposed model is then utilized to simulate numerically the system transient and steady‐state response under different operating and design conditions. A system global optimization for maximum performance (or minimum exergy destruction) in the search for minimum pull‐down and pull‐up times, and maximum system second law efficiency is performed with low computational time. Appropriate dimensionless groups are identified and the results are presented in normalized charts for general application. The numerical results show that the three‐way maximized system second law efficiency, η_{II,max,max,max}, occurs when three system characteristic mass flow rates are optimally selected in general terms as dimensionless heat capacity rates, i.e. (ψ_ss, ψ_wxwx, ψ_Hs)_opt=(0.335, 0.28, 0.2). The minimum pull‐down and pull‐up times, and maximum second law efficiencies found with respect to the optimized operating parameters are sharp and, therefore, important to be considered in actual design. As a result, the model is expected to be a useful tool for simulation, design, and optimization of solar energy systems in the context of distributed power generation. Copyright © 2008 John Wiley & Sons, Ltd.     

Qualitative economics: An implementation in PROLOG

In this paper, we describe a formalism for qualitative reasoning in economics. The framework may serve as a common basis for the intuitive reasoning practised by experienced economists and the more formal qualitative models recently established in the field of artificial intelligence. The emphasis is on representation and implementation aspects of qualitative models. The formalism is illustrated in a well-known Keynesian model.     

Intensive regional vaccination with a gI-deleted vaccine markedly reduces pseudorabies virus infections

The development of marker vaccines against pseudorabies virus (PRV) and companion diagnostic tests have enabled us to perform a unique field trial. In this study, the effect of intensive regional vaccination on pig-finishing herd immunity was directly measured by comparing the seroprevalence of antibodies to glycoprotein I in trial and control groups. The seroprevalence of infected finishing herds in the trial region decreased from 81% at the start of the trial to 19% after 2 years (p < 0.001). The mean seroprevalence of infected pigs in these herds diminished from 49 to 5% (p < 0.001). In the control group, representing routine PRV control, no significant change in seroprevalences was noticed.     

Finite-Element Method Simulations of Guided Wave Phenomena at Terahertz Frequencies

As the science and engineering associated with terahertz time-domain spectroscopy and imaging evolves past the use of conventional free-space optics, the continued development of waveguides for terahertz pulses is increasingly relevant. The ability to model and simulate terahertz wave propagation aids in the development, visualization, and understanding of novel terahertz devices and phenomena. We discuss the use of the finite-element method, a powerful computational tool for the modeling of guided wave phenomena and devices at terahertz frequencies.     

Dynamics of differentiation: Similarity as the precursor and product of stereotype formation.

The degree of data-based and expected coherence within groups was predicted to enhance intergroup differentiation in the illusory correlation paradigm. Results of Study 1 indicated that data-based coherence was a prerequisite for illusory correlation, and this effect was further enhanced by expected coherence. Reinterpretations of the behaviors also augmented illusory correlation, especially when instructions provided greater scope for this, but only under conditions of data-based coherence. The finding that group coherence enhances illusory correlation contradicts recent findings of A. R. McConnell, S. J. Sherman, and D. L. Hamilton ( 1997). This anomaly was resolved by showing that the relation between group coherence and illusory correlation is curvilinear (Study 2). Illusory correlation increased with coherence but diminished when group coherence was sufficiently high to undermine meaningful evaluative differentiation between groups. Results showed that intragroup similarity is both a precursor and a product of differentiation and illusory correlation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Touch-typing VDU operation: workstation adjustment,working posture and workers' perceptions

At a VDU workstation professional touch-typing operators worked at eight different combined adjustments of visual target height and chair backrest inclination. Working posture, workers' perceptions and work performance were measured. Two conclusions were drawn. First, in order to minimize the load on the musculoskeletal system for touch-typing VDU operators, the gaze inclination to a visual target (screen, document) should be 6-9 degrees (range 0-15 degrees ) below the horizontal and, second, the gaze inclination recommended is independent of sitting posture (that is with the backrest between upright and 15 degrees inclined backwards).