Fast adders using enhanced multiple-output domino logic

Using an enhanced multiple output domino logic (EMODL) implementation of a carry lookahead adder (CLA), sums of several consecutive bits can be built in one nFET tree with a single carry-in. Based on this result, a new sparse carry chain architecture is proposed for the CLA adder. We demonstrate the design approach using a 32-b adder, and show that only four carries are sufficient for generating all sums, with a consequent reduction in the number of stage delays. Using a 1.2-μm CMOS technology, we verify our simulation procedures by fabrication and measurement of a 2.7 ns critical path     

A series active power filter based on a sinusoidalcurrent-controlled voltage-source inverter

A series active power filter working as a sinusoidal current source, in-phase with the mains voltage, has been developed and tested. The amplitude of the fundamental current in the series filter is controlled through the error signal generated between the load voltage and a pre-established reference. The control allows an effective correction of power factor, harmonic distortion and load voltage regulation. Compared with previous methods of control developed for series active filters, this method is simpler to implement because it is only required to generate a sinusoidal current, in-phase with the mains voltage, the amplitude of which is controlled through the error in the load voltage. The proposed system has been studied analytically and tested using computer simulations and experiments. In the experiments, it has been verified that the filter keeps the line current almost sinusoidal and in-phase with the line voltage supply. It also responds very quickly under sudden changes in load conditions, reaching its steady-state in about two cycles of the fundamental     

Monte Carlo simulations of homogeneous upconversion in erbium-dopedsilica glasses

Quenching of Er³⁺ ions by homogeneous energy-transfer upconversion in high-concentration erbium-doped silica glasses has been theoretically investigated, The results indicate that at Er³⁺ concentrations of 1.0-2.0·10²⁶ m^-3 or below, the kinetic limit of strong migration is not reached, and hence the widely accepted quadratic upconversion model is not generally valid. Nevertheless, the results offer an explanation of the experimental observations of quadratic upconversion. Furthermore, it has been shown that at a given population inversion, the quenching rate depends on the rate of exchange of the excited Er³⁺ ions by emission and absorption     

Generation of frequency-chirped optical pulses in a large-slippagefree-electron laser

We have investigated the optical output of the free-electron laser for infrared experiments (FELIX) when it is driven by an electron beam with a ramped energy. We show that the applied slow ramp on the electron beam energy leads to a frequency chirp on each picosecond optical pulse. Typical values for the chirp are 0.2% frequency sweep across a 1.5-ps-long optical pulse. The optical pulses were analyzed with a double-grating pair and with a second-order autocorrelator. The pulse duration was reduced in the double-grating pair by 20%. A linear dependence of the chirp on the cavity desynchronization was measured     

Characterisation and modelling of VBR video traffic

The impact of VBR video traffic characteristics on broadband network performance is analysed. In particular, the authors compare in a queue the behaviour of several models that adjust different statistical parameters of actual MPEG traces. It is proved that a good fit of the probability density function (PDF) is essential to approximate queuing behaviour while the effects of short range dependence (SRD) are of secondary importance and those of long range dependence (LRD) could be neglected for practical purposes if realistic scenarios, with strict QoS requirements, are considered     

Measurement of PLL phase error caused by power supply noise

The measurement of the accumulated phase error of phase-locked loops (PLLs) in microprocessor systems is discussed. A system which creates controlled power supply noise and measures the PLL response is described. Examples of the use of this technique are shown for a PLL used in a 400 MHz microprocessor     

Invariant image classification using triple-correlation-basedneural networks

Triple-correlation-based neural networks are introduced and used in this paper for invariant classification of 2D gray scale images. Third-order correlations of an image are appropriately clustered, in spatial or spectral domain, to generate an equivalent image representation that is invariant with respect to translation, rotation, and dilation. An efficient implementation scheme is also proposed, which is robust to distortions, insensitive to additive noise, and classifies the original image using adequate neural network architectures applied directly to 2D image representations. Third-order neural networks are shown to be a specific category of triple-correlation-based networks, applied either to binary or gray-scale images. A simulation study is given, which illustrates the theoretical developments, using synthetic and real image data.     

Longitudinal bone mineral density changes in early rheumatoid arthritis

A prospective longitudinal study of patients with early RA was performed to examine the influence of disease duration, disease activity and physical activity on bone loss. Sixty-seven patients with non-steroid treated RA of less than 5 yr duration, including 16 patients with disease duration less than 6 months, had BMD measurements of the femoral neck and the lumbar spine over a 12-month period using dual energy X-ray absorptiometry. The BMD changes were compared with values from 72 control patients and were also correlated with serial measurements of disease activity (measured by the Stoke Index) and disability [measured by the Health Assessment Questionnaire (HAQ) score], at 3-monthly intervals over the 12-month period. No significant differences in BMD changes were found between RA patients and controls overall. Patients with disease duration of less than 6 months had significantly greater loss of BMD at the femoral neck (-3.9%, S.E.M. 1.5) than the remainder of the cohort (-0.2%, S.E.M. 0.7) (P = 0.02) and controls (-0.8%, S.E.M. 0.6). Lumbar spine BMD changes correlated with the initial Stoke Index (Rs-0.373, P = 0.01) but not mean Stoke Indices. There was no correlation of BMD changes with age or HAQ scores. These findings suggest that significant bone loss occurs within the first few months of disease in patients with RA.