Forward biased safe operating area of emitter switched thyristors

The physical mechanisms for current saturation and destructive failure of the dual channel emitter switched thyristor (EST) are described. Forward Biased Safe Operating Areas (FBSOAs) at short-circuit state of the 600 V and 2500 V dual channel ESTs are reported. It is demonstrated by numerical simulation that the EST offers a better FBSOA than the IGBT. Experimental measurements are reported that corroborate these calculated results     

Average- and Median-Based Smoothing Techniques for Improving Digital Speech Quality in the Presence of Transmission Errors

In digital speech communication, transmission errors generally introduce impulsive distortions in the received speech waveform. Smoothing of this waveform results at once in a squelching of the distortion component, and in an undesirable smearing of the speech. However, our experience with practical differential PCM (DPCM) codes (with adaptive quantizers and first-order predictors) has shown that if the error probability is fairly significant (for example, 0.025), the noise attenuation is perceptually desirable in spite of the attendant speech-muffling. Our observations are based on computer simulations and informal listening tests. The smoothing can be performed either on the received DPCM word (prediction error signal) or the reconstructed speech amplitude. (The two signals are identical in nondifferential PCM.) Smoothing algorithms can be either linear (based, for example, on running averages) or nonlinear (based, for example, on running medians). Studies with 3-bit quantizers indicate that with independently occurring transmission errors, smoothing of the prediction error signal is perceptually desirable, although the benefits decrease as a function of the predictor coefficient a, with the maximum advantage showing up fora = 0(PCM). Running averages and running medians seem to work equally well, and suggested block lengths for their computations are three or five samples. Results with clustered transmission errors show a higher advantage due to smoothing and a preference of linear methods and longer block lengths.     

Enhancement of ADPCM speech coding with backward-adaptivealgorithms for postfiltering and noise feedback

It is shown that postfiltering circuits based on higher order LPC (linear predictive coding) models can provide very low distortion in terms of special tilt. Thus, they can provide better speech enhancement than circuits based on the backward-adaptive pole-zero predictor in ADPCM (adaptive digital pulse code modulation). Quantitative criteria for designing postfiltering circuits based on higher-order LPC models are discussed. These postfilters are particularly attractive for systems where high-order LPC analysis is an integral part of the coding algorithm. In a subjective test that used a computer-simulated version of these circuits, enhanced ADPCM obtained a mean opinion score of 3.6 at 16 kb/s     

The structure of boron in boron fibres

The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behaviour of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.     

On Soft-Decision Demodulation for PCM- and DPCM- Encoded Speech

In a simulation of soft decision demodulation-interpolation for digital speech transmission, it has been noted that signal-to-noise ratio gains due to the technique are greater with nonadaptive and periodically adaptive quantizers than with instantaneously adaptive quantizers; further, the gains are greater with PCM than with differential PCM. Our results for nonadaptive PCM reinforce those in a recent analytical paper by Sundberg [1].     

The di/dt capability of field-controlled thyristors

Limitations to the di/dt capability of field controlled thyristors are discussed. Although the di/dt rating of these devices is not limited by plasma spreading as in conventional thyristors, destructive di/dt induced failure in surface gate devices has been observed. This failure has been shown to be due to non uniform turn-on in these devices due to inhomogeneities in the base region resistivity. Based upon this failure mechanism, it can be concluded that devices with higher di/dt ratings can be fabricated by decreasing the cathode and gate finger lengths and using thicker cathode metallization. In addition an improved device structure with vertical current flow is described with which further increases in di/dt ratings of these devices can be expected.     

Anomalous diffusion from doped oxides due to dopant depletion effects

An anomalous decrease in junction depth with increasing diffusion time has been observed for the first time for diffusions from doped oxides into semiconductors. Experimental data on the diffusion of tin into gallium arsenide is provided, with a simple theoretical analysis of the phenomena.     

Developmental changes in storage proteins and peptidyl prolyl cis–trans isomerase activity in grains of different wheat cultivars

In the present study, storage proteins from five different wheat cultivars were extracted, fractionated and evaluated for their accumulation at different stages of development. SDS–PAGE analysis revealed that the accumulation of high molecular weight glutenin subunits was cultivar and stage dependent. However, low molecular weight glutenin subunits’ accumulation was not altered significantly after 16 days post anthesis in any of the cultivars. The rheological parameters (storage- and loss-modulus) of dough and gluten showed close association with either gliadins or glutenins. Peptidyl prolyl cis–trans isomerase (PPIase) activity, measured at different stages of grains development, showed variability with both the developmental stage and cultivar, and appeared to be primarily due to cyclophilins. Principal component analysis revealed the association of PPIase activity with either gliadin or total proteins, suggesting their significant role in the deposition of storage proteins in wheat.     

Benchmarking large-scale data management for Internet of Things

The Journal of Supercomputing - In the current era of the Internet of Things (IoT), massive number of sensors are used in our daily lives. Sensors are everywhere around us. They exist in our homes,...