Random Pulse Research Articles

On random pressure pulses in the turbine draft tube

The flow in the conical part of the hydroturbine draft tube undergoes various instabilities due to deceleration and flow swirling at off-design operation points. In particular, the precessing vortex rope develops at part-load regimes in the draft tube. This rope induces periodical low-frequency pressure oscillations in the draft tube. Interaction of rotational (asynchronous) mode of disturbances with the elbow can bring to strong oscillations in the whole hydrodynamical system. Recent researches on flow structure in the discharge cone in a regime of free runner had revealed that helical-like vortex rope can be unstable itself. Some coils of helix close to each other and reconnection appears with generation of a vortex ring. The vortex ring moves toward the draft tube wall and downstream. The present research is focused on interaction of vortex ring with wall and generation of pressure pulses.

Performance Characterization of Random Pulse Width Modulation Algorithms in Industrial and Commercial Adjustable-Speed Drives

One of the problems of the pulse-width-modulation (PWM)-controlled ac machines is the acoustic noise that could become unacceptable when used in sensitive environments. Random PWM (RPWM) in industrial and commercial adjustable-speed drives (ASD) results in the partial transfer of power from the discrete spectrum (narrowband noise) of the output voltage to the continuous spectrum (wideband noise), with advantageous effects on reducing the acoustic noise in the motor drive system. In this paper, the theoretical power spectrum analysis as the basis for RPWM is presented. Five state-of-the-art RPWM strategies, their voltage, current, and acoustic noise spectra characteristics are quantitatively evaluated. The PWM schemes and theoretical analysis are validated through a 2.2-kW 380-V 50-Hz ASD induction machine experimental setup. The results provide valuable data for practicing engineering community to choose the best option in real-world applications.

Pulse Control Assisted Dynamical Decoupling in a Central Spin Model

We study pulse control assisted dynamical decoupling through a central spin model in a total Hilbert space. We find that the effective decoupling can be realized by applying a sequence of external pulses. Compared with the bang-bang control which needs infinite strength and infinitesimal short pulses, we show that there is a large parameter space that allows an effective nonperturbative dynamical control. Furthermore, our numerical calculation shows that the reliability can be held for random pulses, such as random pulse time interval or random strength.

3-Gb/s High-Speed True Random Number Generator Using Common-Mode Operating Comparator and Sampling Uncertainty of D Flip-Flop

True random number generators (TRNGs) are important in data encryption for information security applications. In this paper, we propose a TRNG that utilizes a comparator in the common-mode operation and the sampling uncertainty of a D flip-flop (DFF). The comparator output is affected by the input common-mode noise and the noise that is simultaneously self-induced. A slicer generates an unpredictable and asynchronous pulse to the input of the DFF according to the output-referred noise of the comparator. By sampling the random pulse with a 3-GHz external clock, there is a sampling uncertainty, which helps to increase the random quality. As a result, we use the independent two random sources for TRNG. The area of the designed circuit is 1609 $\mu \text{m}^{\mathrm { {2}}}$ . In spite of the small size, the data rate of the proposed TRNG is 3 Gb/s. We verify that the output bit stream passes all of the National Institute of Standards and Technology test suites. We fabricate the TRNG in a 65-nm CMOS process with a 1.2 V supply voltage. The power consumption of the proposed TRNG is 5 mW, and the energy per bit is 1.6 pJ/b.

Glucose Levels and Hemodynamic Changes in Patients submitted to Routine Dental Extraction under Local Anesthesia with and without Adrenaline.

In maxillofacial surgery, the simplest procedure that we perform is dental extraction. However, this simple procedure is challenged by the patient's poor medical condition. We generally use local anesthesia in combination with adrenaline; however, as we come across patients with diabetes mellitus and cardiovascular diseases who seek dental extraction, we need to be doubly cautious while using adrenaline. In this study, we intend to compare the effects of local anesthesia with adrenaline and local anesthesia without adrenaline on hemodynamic changes (blood pressure and pulse rate) and random blood sugar levels. The comparison is both within the group and between the two groups. Healthy patients between the ages 20 and 60 years were included and randomized into two groups of 50 each. In one group, plain local anesthesia was used, whereas in the other group, local anesthetic solution containing adrenaline was used. Medically compromised patients were excluded from the study. Random blood sugar levels, blood pressures, and pulse rates were recorded in both groups before and 10 minutes after injecting the solutions. The findings were compared. When results are compared within the group, a modest increase in the blood sugar level was noted with the group receiving local anesthetic with adrenaline. However, blood pressure and pulse rate showed no significant difference. Similarly, when between-the-groups comparison was done, not a single variable showed any significant difference. The patients injected with local anesthesia containing adrenaline showed similar results to that observed in the patients injected with local anesthesia without adrenaline. However, there is a statistically significant rise in blood sugar levels when a local anesthetic is injected with adrenaline. Dental extractions in healthy individuals can be safely performed with local anesthetic containing adrenaline. However, in diabetic patients, it should be cautiously used.

Random pulse detection against white noise and correlated interference in the conditions of parametrical prior uncertainty

Random pulse detection against white noise and correlated interference in the conditions of parametrical prior uncertainty

Implementation and Evaluation of FPGA-based Annealing Processor for Ising Model by use of Resource Sharing

The non-von Neumann computer architecture has been widely studied to prepare us for the post-Moore era. The authors implemented this kind of architecture, which finds the lower energy state of the Ising model using circuit operations inspired by simulated annealing in SRAM-based integrated circuits. Our previous prototype was suited for the Ising model because of its simple and typical structure such as its three-dimensional lattice topology, but it could not be used in real world applications. A reconfigurable prototyping environment is needed to develop the architecture and to make it suitable for applications. Here, we describe an FPGA-based prototyping environment to develop the annealing processor's architecture for the Ising model. We implemented the new architecture using a prototyping environment. The new architecture performs approximated simulated annealing for the Ising model, and it supports a highly complex topology. It consists of units having fully-connected multiple spins. Multiple units are placed in a two-dimensional lattice topology, and neighboring units are connected to perform interactions between spins. The number of logic elements was reduced by sharing the operator among multiple spins within the unit. Furthermore, a pseudo-random number generator, which produces random pulse sequences for annealing, is also shared among all the units. As a result, the number of logic elements was reduced to less than 1/10, and the solution accuracy became comparable to that of a conventional computer's simulated annealing.

Frequency Spectrum Customization and Optimization by Using Monte Carlo Method for Random Space Vector Pulse Width Modulation Strategy

Frequency Spectrum Customization and Optimization by Using Monte Carlo Method for Random Space Vector Pulse Width Modulation Strategy

Response to Discussion on “A Variable Switching Frequency PWM Technique for Induction Motor Drive to Spread Acoustic Noise Spectrum With Reduced Current Ripple”

In random pulse width modulation (RPWM) category, a wide variety of schemes is seen as described in the paper. The discussion part is mainly focused on the randomized carrier frequency approach, where the switching periods are selected randomly, irrespective of the ripple voltage. For prediction of rms current ripple over a switching cycle as well as rms current ripple over the line cycle, precise knowledge of the switching period is required; this is not possible with random PWM techniques, though these methods are following a probability distribution function. However, accurate prediction of current total harmonic distortion (THD) is possible with the variable frequency PWM (VFPWM) method, as the switching period is a function of the fundamental angle. The procedure followed for current THD prediction is explained in [1].

Shortcuts to adiabaticity in cutting a spin chain

“Shortcuts to adiabaticity” represents a strategy for accelerating a quantum adiabatic process, is useful for preparing or manipulating a quantum state. In this paper, we investigate the adiabaticity in the dynamics of an XY spin chain. During the process of cutting one long chain into two short chains, a “shortcut” can be obtained by applying a sequence of external pulses. The fidelity which measures the adiabaticity can be dramatically enhanced by increasing the pulse strength or pulse duration time. This reliability can be kept for different types of pulses, such as random pulse time interval or random strength. The free choice of the pulse can be explained by the adiabatic representation of the Hamiltonian, and it shows that the control effects are determined by the integral of the control function in the time domain.

Statistics of a space-time random pulse train.

A general approach for obtaining the statistics of a pulse train is developed, where the pulses are space and time dependent, and where the initial distribution of the pulses may be non-uniform. Explicit expressions for the moments up to fourth order, in terms of the moments of the elementary signals constituting the pulse train, are obtained. This is done for elementary signals that are waves. The expressions obtained are totally general as long as the elementary signals are not correlated. In contrast to the standard scintillation index, it may be space and time dependent, in which case it is called the dynamical scintillation index. This allows one to understand how a space-time pulse train approaches stationarity at different positions and times. The scintillation index using both the raw and central moments is defined. For the raw moments, both exact expressions and expansions in 1/N, where N is the number of elementary signals are obtained. For central moments, particularly simple exact expressions are given.

Variable-Switching Frequency PWM Technique for Induction Motor Drive to Spread Acoustic Noise Spectrum With Reduced Current Ripple

Pulse-width modulation (PWM) of a motor drive at a fixed switching frequency leads to harmonic currents in narrow bands around integral multiples of the switching frequency resulting in tonal frequency acoustic noise components, which are irritating to the human ear. Random variation of carrier frequency to spread the spectrum poses challenges in device loss calculation, thermal design, and closed-loop controller design. Random pulse positioning is not quite effective at high speeds of the drive, where the problem of acoustic noise is most pronounced. This paper proposes a simple variable-frequency PWM and evaluates the performance of the same experimentally on a 6-kW induction motor drive. The experimental results show that the acoustic noise is spread uniformly over a range of frequencies without introducing low-frequency current harmonics. Compared with fixed-frequency PWM, the dominant acoustic noise is reduced significantly over a wide range of speeds. The variable-frequency PWM is further shown to reduce line current total harmonic distortion at high speeds of the drive. The computational effort required by the variable-frequency PWM is only marginally higher than that required by fixed-frequency PWM.

Predator population depending on lemming cycles

In this paper, a Langevin equation for predator population with multiplicative correlated noise is analyzed. The noise source, which is a nonnegative random pulse noise with regulated periodicity, corresponds to the prey population cycling. The increase of periodicity of noise affects the average predator density at the stationary state.

Refined Analysis of Sparse MIMO Radar

We analyze a multiple-input multiple-output (MIMO) radar model and provide recovery results for a compressed sensing (CS) approach. In MIMO radar different pulses are emitted by several transmitters and the echoes are recorded at several receiver nodes. Under reasonable assumptions the transformation from emitted pulses to the received echoes can approximately be regarded as linear. For the considered model, and many radar tasks in general, sparsity of targets within the considered angle-range-Doppler domain is a natural assumption. Therefore, it is possible to apply methods from CS in order to reconstruct the parameters of the targets. Assuming Gaussian random pulses the resulting measurement matrix becomes a highly structured random matrix. Our first main result provides an estimate for the well-known restricted isometry property (RIP) ensuring stable and robust recovery. We require more measurements than standard results from CS, like for example those for Gaussian random measurements. Nevertheless, we show that due to the special structure of the considered measurement matrix our RIP result is in fact optimal (up to possibly logarithmic factors). Our further two main results on nonuniform recovery (i.e., for a fixed sparse target scene) reveal how the fine structure of the support set—not only the size—affects the (nonuniform) recovery performance. We show that for certain “balanced” support sets reconstruction with essentially the optimal number of measurements is possible. Indeed, we introduce a parameter measuring the well-behavedness of the support set and resemble standard results from CS for near-optimal parameter choices. We prove recovery results for both perfect recovery of the support set in case of exactly sparse vectors and an $$\ell _2$$ -norm approximation result for reconstruction under sparsity defect. Our analysis complements earlier work by Strohmer & Friedlander and deepens the understanding of the considered MIMO radar model. Thereby—and apparently for the first time in CS theory—we prove theoretical results in which the difference between nonuniform and uniform recovery consists of more than just logarithmic factors.

Early Gut Colonization of Preterm Infants: Effect of Enteral Feeding Tubes.

The aim of the study was to evaluate the potential colonization of nosocomial bacteria in enteral feeding systems and its effect on early gut colonization of preterm neonates. Mother's own milk, donor milk, and preterm formula samples obtained after passing through the external part of the enteral feeding tubes were cultured. In addition, meconium and fecal samples from 26 preterm infants collected at different time points until discharge were cultured. Random amplification polymorphism DNA and pulse field gel electrophoresis were performed to confirm the presence of specific bacterial strains in milk and infant fecal samples. Approximately 4000 bacterial isolates were identified at the species level. The dominant species in both feces from preterm infants and milk samples were Staphylococcus epidermidis, S aureus, Enterococcus faecalis, E faecium, Serratia marcescens, Klebsiella pneumoniae, and Escherichia coli. All of them were present at high concentrations independently of the feeding mode. Random amplification polymorphism DNA and pulse field gel electrophoresis techniques showed that several bacteria strains were found in both type of samples. Furthermore, scanning electron microscopy revealed the presence of a dense bacterial biofilm in several parts of the feeding tubes and the tube connectors. There is a sharing of bacterial strains between the neonates' gastrointestinal microbiota and the feeding tubes used to feed them.

ENGLISH

This paper addresses random pulse width modulation (RPWM) and its applications to the power electronic converters. RPWM differentiate from conventional PWM, which produces switching functions that have non deterministic variables. This paper presents new RPWM scheme developed with the help of virtual Instrumentation (VI) software. The comparative investigations of proposed RPWM scheme against the normal PWM for the buck boost converter is presented. The effectiveness of randomization on spreading the dominating frequencies that normally exist in constant frequency PWM schemes is evaluated by the power spectral density (PSD) estimations in the low-frequency range.

FPGA-based Digitally Controlled Isolated Full-Bridge DC-DC Converter with Voltage Doubler (IFBVD)

An isolated full-bridge dc-dc converter with voltage doubler (IFBVD) is mainly used in higher power applications. This paper presents the testing and implementation of a digitally controlled Random pulse width modulated isolated full-bridge DC-DC converters with voltage doubler (IFBVD). Different PWM techniques for full-bridge DC/DC converter are investigated. Field Programmable Gate Array (FPGA) is used to obtain different PWM techniques. It is most commonly used in designing PWM Generator for Power Converter Applications. A comprehensive comparison between the various PWM techniques, including current stress, ripple and efficiency, is presented. Simulation is done using Matlab/Simulink. An experimental setup has been provided to validate the theoretical and simulation results using FPGA control. Experimental results of a 0.5kW, 50kHz prototype are presented.

Effect of DC Link Fluctuations on Harmonic Spreading Effect in Voltage Source Inverter Fed Three Phase Induction Motor Drives

The aim of the study is to analyze the effect of DC link fluctuations on the output voltage of the inverter. Voltage Source Inverters (VSI) plays a dominant role in the industrial world. Most of the industries use rectifiers to convert single phase AC supply to DC supply. DC supply is fed to the Voltage Source Inverter (VSI) through a DC link capacitor. The capacitor decides the quality of output fed to the Voltage Source Inverter. Six pulses are given to the Voltage Source Inverter by means of MCBRCPWM (Multiple Carrier Based Random Carrier Pulse Width Modulation) technique. The output of Voltage Source Inverter is fed to a three phase squirrel cage induction motor. The investigation of MCBRCPWM with different capacitor values provided in the DC link has been effectively discussed. The results of harmonic spectra and Total Harmonic Distortion (THD) are given in the paper. Simulation results prove that as the value of capacitor increases, the evaluation parameters such as Total Harmonic distortion, Fundamental Voltage and Harmonic Spread Factor (HSF) are improved.

Intensive random carrier pulse width modulation for induction motor drives based on hopping between discrete carrier frequencies

The existing random carrier pulse-width modulation (RCPWM) schemes result in poor non-deterministic characteristics. They basically use a single-frequency triangular carrier and its inverted version to synthesise the random carrier by a pseudo-random binary sequence (PRBS) bit selector. Even though the bits are highly random in nature with large pattern repetition rate, the resulting random carrier does not possess required level of randomness. Rather it can make slight positional variation in the resulting PWM pulses. Moreover, the harmonic spreading effects of these randomness may not be sufficient to meet the expectations of modern drives. Hence, this study proposes a multiple carriers based RCPWM (MCBRCPWM) scheme for the voltage-source inverter fed induction motor drive to enhance the harmonic power spreading ability of the modulator. The proposed MCBRCPWM scheme utilises the non-deterministic characteristics of both the PRBS and hopping action between the MCs involved. The simulation results using MATLAB 7.1.0 (2010a)-Simulink software and the experimental results with hardware implemented using XC6SLX45 field programmable gate array for a 3O squirrel cage induction motor load prove the excellent harmonic spectra spreading capability of the proposed scheme as compared with existing non-deterministic methods.

Multi-Channel Autonomous Information System Performance with Positional Signal State Analyzers at the Channel Outputs

The article presents a statement of technique to research performances of multi-channel combo standalone information systems with positional analyzers of the signal states at the channel outputs. In most cases, in considered multi-channel systems there has been impossible to coincide in time the random moments of signals coming from the objects through various channels in all ways of encounter environment and conditions of practical application. The analyzer makes decision on the signal using the discrete operations on the quantized signals of the certain duration from the channel outputs. The analyzer performance is described by a set of Boolean algebra functions defined for all possible states of the signals at the outputs of the channels, and in the general case is specified in a perfect disjunctive normal form. To determine the validity or falsity of functions of the algebra of logics, which are calculated statements concerning the available or unavailable useful signal at the system input, on the authority of the Poretsky’s theorem and the theory of coincidence in time of the random pulse flow of the channels response because of uncorrelated and correlated noise, are obtained dependences to calculate the probabilities of false alarms and omissions of the signals in discrete combined systems. It is shown that the flows of false alarms because of noise at the channel outputs in the system are Poisson streams. On the basis of the ordinary Poisson flows the paper justifies the relationships for calculating the false alarms of the system with uncorrelated and correlated noise in the channels. The paper also justifies the relationships for performance of multichannel combined systems with positional analyzers of the channels states. Based on the obtained relationships was calculated the average coincidence frequency of the extended pulses of the channel response in a dualchannel system, depending on the noise cross-correlation coefficient with different extended pulse durations and relative response thresholds in the channels. The impact of cross-correlation noise has been analysed. The obtained results enable us to examine the performance of the multichannel autonomous information systems with positional analyzers of the signal states at the outputs of channels operating under uncorrelated and correlated noise.