Efficiency convergence processes and effects of regulation in the nonspecialized retail sector in Spain

This work analyzes the effects of the regulation/deregulation processes carried out on the evolution of efficiency in Spanish retail-sector firms in the period 1996–2004. The results suggest that the regulation in this sector has had a considerable influence on firms’ efficiency, in particular, the legislation on the expansion of commercial opening hours after 2000. The results provide clear evidence of a convergence in firms’ efficiency from the initial year considered to superior levels. Moreover, the pattern of convergence differs in function of the region in which the firm operates. The evolution of efficiency given by the means of different groups of regulation intensity levels through the time seems to show clearly in the groups of high and low regulation. It is observed that the group of high regulation is the most efficient. The analysis of the firms as a whole confirms the convergence process. Considering the analysis for subperiods an improvement is observed for all regions in the period 2000 at 2004.     

Nonlinear optimization tools for the design of high-efficiency microwave oscillators

A new systematic method is presented for the design of high-efficiency microwave oscillators. It is based on the control of the transistor output-voltage waveform, through the combined use of a nonperturbing auxiliary generator and a substitution generator. The nonperturbing generator sets the oscillation frequency at the desired value during the entire design process. The combination of the two generators allows obtaining a quasisquare output-voltage waveform, with optimum harmonic components to maximize the efficiency. Attention is paid to the stability and phase noise of the implemented oscillator, which are analyzed versus technological parameters. A 6-GHz oscillator has been designed using these techniques, with good experimental results.     

A FLAVOUR MODEL FOR BEER FERMENTATION

A new beer fermentation model is developed based upon fundamental knowledge of biochemical pathways. The model can be subdivided into a growth model, an amino acid model, and a flavour/aroma model. Experimentation allowed for accurate model parameter identification. The results demonstrate the capability to accurately describe batch beer fermentation dynamics.     

Fluorescent protein tomography scanner for small animal imaging

Microscopy of fluorescent proteins has enabled unprecedented insights into visualizing gene expression in living systems. Imaging deeper into animals, however, has been limited due to the lack of accurate imaging methods for the visible. We present a novel system designed to perform tomographic imaging of fluorescent proteins through whole animals. The tomographic method employed a multiangle, multiprojection illumination scheme, while detection was achieved using a highly sensitive charge-coupled device camera with appropriate filters. Light propagation was modeled using a modified solution to the diffusion equation to account for the high absorption and high scattering of tissue at the visible wavelengths. We show that the technique can quantitatively detect fluorescence with sub millimeter spatial resolution both in phantoms and in tissues. We conclude that the method could be applied in tomographic imaging of fluorescent proteins for in vivo targeting of different diseases and abnormalities.     

Artificial neural network approach to distance protection oftransmission lines

A distance relay for the protection of transmission lines is usually designed on the basis of fixed settings. The reach of such relays is therefore affected by the changing network conditions. The implementation of a pattern recognizer for power system diagnosis can provide great advances in the protection field. This paper demonstrates the use of an artificial neural network as a pattern classifier for a distance relay operation. The scheme utilizes the magnitudes of three phase voltage and current phasors as inputs. An improved performance with the use of an artificial neural network approach is experienced once the relay can operate correctly, keeping the reach when faced with different fault conditions as well as network configuration changes     

Surface copper enrichment by reduction of copper chromite catalyst employed for carbon monoxide oxidation

The effect of prereduction on CO oxidation activity of unsupported copper-chromite oxide catalysts was examined. Results were found to be in good agreement with two mechanisms for a surface copper enrichment due to CO prereduction which produced an activity increase in the copper-chromite catalyst.     

Ultrasonic Dispersion of Ceramic Powders

Ultrasonication is very effective in dispersing alumina and barium titanate slurries. When optimum conditions are used, very short durations (2 to 3 min) are enough to achieve well-dispersed, stable suspensions.     

Harmonic-balance analysis and synthesis of coupled-oscillator arrays

A new harmonic-balance technique for the analysis and synthesis of coupled-oscillator systems with adjustable phase progression is presented here. It allows an accurate determination of the phase-shift versus the tuning elements, since detailed models are used for the individual oscillator circuits. It is also possible to impose the synchronization frequency at which the in-phase oscillation takes place and calculate the values of the tuning elements for a pre-fixed phase distribution. The phase noise of the system is analyzed through the carrier modulation approach. The phase-change rapidity versus a control voltage is analyzed through the envelope-transient method. A four-element oscillator array at 5 GHz has been designed through this method and experimentally characterized obtaining very good agreement with the simulation results.     

Analysis of stabilization circuits for phase-noise reduction in microwave oscillators

Two configurations for oscillator phase-noise reduction using stabilization circuits have been demonstrated in the literature. One of them is based on the self-injection of the oscillator signal, after it passes through a long delay line or a high-quality-factor resonator. The second one is a stabilization loop, containing a frequency discriminator. In this paper, an in-depth analytical comparison of these two configurations, respectively based on injection locking and phase-locking principles, is presented. Analytical expressions are provided for the variation of the steady-state solution and its phase noise versus the parameters of the feedback network. The expressions are rigorously validated with harmonic balance. Instabilities reported by other authors are investigated through bifurcation analysis. The new expressions enable a good understanding of the amplitude and frequency jumps and sharp phase-noise maxima obtained simulations and measurements versus the feedback parameters. A practical 5-GHz voltage-controlled oscillator has also been implemented, for validation purposes.