Random Pulse Research Articles

ACHIEVING A LINEAR DOSE RATE RESPONSE IN PULSE-MODE SILICON PHOTODIODE SCINTILLATION DETECTORS OVER A WIDE RANGE OF EXCITATIONS

We are developing a new dose calibrator for nuclear pharmacies that can measure radioactivity in a vial or syringe without handling it directly or removing it from its transport shield “pig”. The calibrator's detector comprises twin opposing scintillating crystals coupled to Si photodiodes and current-amplifying trans-resistance amplifiers. Such a scheme is inherently linear with respect to dose rate over a wide range of radiation intensities, but accuracy at low activity levels may be impaired, beyond the effects of meager photon statistics, by baseline fluctuation and drift inevitably present in high-gain, current-mode photodiode amplifiers. The work described here is motivated by our desire to enhance accuracy at low excitations while maintaining linearity at high excitations. Thus, we are also evaluating a novel “pulse-mode” analog signal processing scheme that employs a linear threshold discriminator to virtually eliminate baseline fluctuation and drift. We will show the results of a side-by-side comparison of current-mode versus pulse-mode signal processing schemes, including perturbing factors affecting linearity and accuracy at very low and very high excitations. Bench testing over a wide range of excitations is done using a Poisson random pulse generator plus an LED light source to simulate excitations up to ∼106 detected counts per second without the need to handle and store large amounts of radioactive material.

Digital configurable instrument for emulation of signals from radiation detectors

The paper presents a digital instrument characterized by a specially designed architecture that is able to emulate in real time signals from a generic radiation detection system. The instrument is not a pulse generator of recorded shapes but a synthesizer of random pulses compliant to programmable statistics for height and starting time of events. Completely programmable procedures for emulation of noise, disturbances, and reference level variation are implemented.

A new method for the pulsar signals simulation

Since X-ray pulsar signals cannot be detected on the ground, the pulsar signals need be simulated using the ground experiments. In this paper,two new simulation methods to obtain the time of arrival are put forward. The first method is based on a statistical physics model, which should overcome the shortcomings of narrow adaptation, low speed, and low time resolution in normal simulation method. This method has a high time-resolution and rapid simulation for any random pulse signals. 23 Another one is for the optimization of statistical models that satisfy signals in non-homogeneous Poisson process. The is second method has an improved simulation speed at least 30 times higher than the common Poisson model, even achieves four orders of magnitude greater than that for low flow pulsars, and this method also achieves a nanosecond time resolution simulation.

Enhanced stability of dispersion-managed mode-locked fiber lasers with near-zero net cavity dispersion by high-contrast saturable absorbers

We experimentally investigate the stability of dispersion-managed mode-locked fiber lasers using carbon-nanotube-based saturable absorbers (SAs) with different modulation depths. An unstable operation region of the mode-locked fiber laser with near-zero net cavity dispersion is observed, where the laser produces random pulse burst rather than stable pulse train. Through the implementation of high-contrast SAs in the laser, the unstable region is found to be shrunk by ~31.3% when the modulation depth of the SAs increases from 6.4% to 12.5%. The numerical simulation is consistent with the experimental observation.

The Realization of Random Frequency Modulation Pulse Compression Signal Based on AD9858

A scheme producing non-linearity frequency-modulated signal which can be updated on-line based on AD9858 is mentioned. A method to design NLFM signal using immediate data update is introduced. Circuit structure is designed. Major factor that impacting data is analyzed and its solution is presented. Experiments certify that this method can generate broadband and narrow pulse width non-linearity frequency-modulated signal, whose frequency spectrum can be updated on-line in real time.

A Digitally Controlled Switching Regulator With Reduced Conductive EMI Spectra

This paper presents the use of a combined random pulse position modulation (RPPM)/digital pulsewidth modulation (DPWM) digital controller for a buck converter to simultaneously achieve low-conductive electromagnetic interference (EMI) and a fast transient response. An area-efficient RPPM/DPWM controller suitable for advanced system-on-chip integration is proposed and implemented in a field-programmable gate array-based prototype to verify its EMI-suppression capability. The experimental results for a 1.2-V digital buck converter show that the proposed digital switching regulator can switch between RPPM and DPWM modes smoothly and automatically. Closed-loop system measurements demonstrate that, compared to DPWM, up to 17.27 and 14.99 dB power spectra reductions are obtained in the input current and switching node, respectively.

Noise Prevents Collapse of Vlasov‐Poisson Point Charges

We elucidate the effect of noise on the dynamics of N point charges in a Vlasov‐Poisson model with a singular bounded interaction force. A too simple noise does not affect the structure inherited from the deterministic system and, in particular, cannot prevent coalescence of point charges. Inspired by the theory of random transport of passive scalars, we identify a class of random fields generating random pulses that are chaotic enough to disorganize the structure of the deterministic system and prevent any collapse of particles. We obtain the strong unique solvability of the stochastic model for any initial configuration of distinct point charges. In the case where there are exactly two particles, we implement the “vanishing noise method” for determining the continuation of the deterministic model after collapse. © 2014 Wiley Periodicals, Inc.

Cell-Cycle Dependence of Transcription Dominates Noise in Gene Expression

The large variability in mRNA and protein levels found from both static and dynamic measurements in single cells has been largely attributed to random periods of transcription, often occurring in bursts. The cell cycle has a pronounced global role in affecting transcriptional and translational output, but how this influences transcriptional statistics from noisy promoters is unknown and generally ignored by current stochastic models. Here we show that variable transcription from the synthetic tetO promoter in S. cerevisiae is dominated by its dependence on the cell cycle. Real-time measurements of fluorescent protein at high expression levels indicate tetO promoters increase transcription rate ∼2-fold in S/G2/M similar to constitutive genes. At low expression levels, where tetO promoters are thought to generate infrequent bursts of transcription, we observe random pulses of expression restricted to S/G2/M, which are correlated between homologous promoters present in the same cell. The analysis of static, single-cell mRNA measurements at different points along the cell cycle corroborates these findings. Our results demonstrate that highly variable mRNA distributions in yeast are not solely the result of randomly switching between periods of active and inactive gene expression, but instead largely driven by differences in transcriptional activity between G1 and S/G2/M.

Aliasing-Free Moving Target Detection in Random Pulse Repetition Interval Radar Based on Compressed Sensing

The electronic counter-countermeasures capabilities of staggered pulse repetition interval (PRI) signal is limited by its repetitive character, and a random PRI radar is an alternative to improve the range and velocity coverage. However, the high sidelobe pedestal of the target Doppler spectrum caused by randomness prevents its development. In this paper, based on the compressed sensing theory, we present a novel framework in random PRI radar to generate the Doppler spectrum with low sidelobe for moving target detection. As a precondition, the equivalent sensing matrix is proved to satisfy the restricted isometry property by testifying its independent sub-Gaussian elements and comparing its mutual coherence as well as eigenvalues of its Gram matrices to a typical random compressed sensing matrix in a statistical sense. To cover the concerned velocity, multichannel processing is used and the iterative grid optimization algorithm is employed to eliminate the grid mismatch effect. The simulation results demonstrate that this scheme has high performance of detection and free aliasing characteristic, which can also shorten the coherent processing interval compared with traditional staggered PRI mode.

Research on the Anti-Interference of Mine Soft-Start Controller

According to QJR-400 mine explosion-proof and intrinsically safe AC motor soft-start controllers are subject to various interference, to analyze interference source, interference factors and its consequences, and to study on the those interferences that has taken measures. In the hardware design, to use photoelectric isolation, anti-interference regulated power supply and reasonable grounding and other measures, which can effectively avoid interference. In the software design, digital filtering program can effectively eliminate the interference of random signals and pulse signals. The experimental results show that these measures can effectively inhibition of external interference.

Analysis of random laser scattering pulse signals with lognormal distribution

The statistical distribution of natural phenomena is of great significance in studying the laws of nature. In order to study the statistical characteristics of a random pulse signal, a random process model is proposed theoretically for better studying of the random law of measured results. Moreover, a simple random pulse signal generation and testing system is designed for studying the counting distributions of three typical objects including particles suspended in the air, standard particles, and background noise. Both normal and lognormal distribution fittings are used for analyzing the experimental results and testified by chi-square distribution fit test and correlation coefficient for comparison. In addition, the statistical laws of three typical objects and the relations between them are discussed in detail. The relation is also the non-integral dimension fractal relation of statistical distributions of different random laser scattering pulse signal groups.

Estimation of CNC machine–tool dynamic parameters based on random cutting excitation through operational modal analysis

Dynamic properties of the whole machine tool structure including tool, spindle, and machine tool frame contribute greatly to the reliability of the machine tool in service and machining quality. However, they will change during operation compared with the results from static frequency response function measurements of classic experimental modal analysis. Therefore, an accurate estimation of the dynamic modal parameters of the whole structure is of great value in real time monitoring, active maintenance, and precise prediction of a stability lobes diagram.Operational modal analysis (OMA) developed from civil engineering works quite efficiently in modal parameters estimation of structure in operation under an intrinsic assumption of white noise excitation. This paper proposes a new methodology for applying this technique in the case of computer numerically controlled (CNC) machine tools during machining operations. A novel random excitation technique based on cutting is presented to meet the white noise excitation requirement. This technique is realized by interrupted cutting of a narrow workpiece step while spindle rotating randomly. The spindle rotation speed is automatically controlled by G-code part program, which contains a series of random speed values produced by MATLAB software following uniform distribution. The resulting cutting produces random pulses and excites the structure in all three directions. The effect of cutting parameters on the excitation frequency and energy was analyzed and simulated. The proposed technique was experimentally validated with two different OMA methods: the Stochastic Subspace Identification (SSI) method and the poly-reference least square complex frequency domain (pLSCF or PolyMAX) method, both of which came up with similar results. It was shown that the proposed excitation technique combined successfully with OMA methods to extract dynamic modal parameters of the machine tool structure.

Cortical Plasticity Induced by Spike-Triggered Microstimulation in Primate Somatosensory Cortex

Electrical stimulation of the nervous system for therapeutic purposes, such as deep brain stimulation in the treatment of Parkinson’s disease, has been used for decades. Recently, increased attention has focused on using microstimulation to restore functions as diverse as somatosensation and memory. However, how microstimulation changes the neural substrate is still not fully understood. Microstimulation may cause cortical changes that could either compete with or complement natural neural processes, and could result in neuroplastic changes rendering the region dysfunctional or even epileptic. As part of our efforts to produce neuroprosthetic devices and to further study the effects of microstimulation on the cortex, we stimulated and recorded from microelectrode arrays in the hand area of the primary somatosensory cortex (area 1) in two awake macaque monkeys. We applied a simple neuroprosthetic microstimulation protocol to a pair of electrodes in the area 1 array, using either random pulses or pulses time-locked to the recorded spiking activity of a reference neuron. This setup was replicated using a computer model of the thalamocortical system, which consisted of 1980 spiking neurons distributed among six cortical layers and two thalamic nuclei. Experimentally, we found that spike-triggered microstimulation induced cortical plasticity, as shown by increased unit-pair mutual information, while random microstimulation did not. In addition, there was an increased response to touch following spike-triggered microstimulation, along with decreased neural variability. The computer model successfully reproduced both qualitative and quantitative aspects of the experimental findings. The physiological findings of this study suggest that even simple microstimulation protocols can be used to increase somatosensory information flow.

Time-resolved chirp properties of semiconductor optical amplifiers in high-speed all-optical switches

The chirp properties of semiconductor optical amplifiers in all-optical switches are numerically investigated using a field propagation model. The chirp dynamics in the blue-shift and red-shift sideband are analyzed under the injection of random optical pump pulses. We also analyze the impact of the blue-detuned filtering scheme that is used to eliminate the pattern effect and enhance the operating speed of the optical switching. The reason for overshoots in eye diagrams in the blue-detuned filtering scheme is explained. We find that overshoots result from the ultrafast blue chirp induced by carrier heating and two-phonon absorption. These results are very useful for semiconductor optical amplifier-based ultrafast all-optical signal processing.

Brownian motion of magnetic nanoparticles as a source of energy?

Brownian motion of magnetic nanoparticles in a low–density gas can induce random voltage pulses in a microscopic electric circuit containing a high–number–of–turns coil and a classical diode rectifier. The amplitude of the voltage pulses is estimated and the rectification condition examined. We have shown that in our toy–model nanogenerator where the motion of the magnetic nanoparticle is restricted to one–dimensional rotation around its vertical axis and the nanoparticle is inserted into a very low number–density gas (3 × 1016 m-3) one can generate voltage pulses of the amplitude of 3 × 10-8 V in one coil turn. The total number of 106 turns is then necessary to reach the rectifying region.

0309 ランダムパルス列電磁場刺激による培養骨芽細胞の活性化(OS08-1 バイオエンジニアリング(1)医療と福祉を支えるバイオエンジニアリング,オーガナイズドセッション 8:「バイオエンジニアリング(1)医療と福祉を支えるバイオエンジニアリング」)

0309 ランダムパルス列電磁場刺激による培養骨芽細胞の活性化(OS08-1 バイオエンジニアリング(1)医療と福祉を支えるバイオエンジニアリング,オーガナイズドセッション 8:「バイオエンジニアリング(1)医療と福祉を支えるバイオエンジニアリング」)

The Two-parameter Analyzing Model and Statistical Distribution Law of the Random Signal in Optical Sensor

In this paper, on the basis of giving a reference amplitude value, the two-parameter analyzing model of the random signal is established by introducing two basic conceptions---the amplitude and the width. Based on which, the statistical distribution law of the random signal group’s characteristic parameters is studied. The experimental results show that the amplitude and the width counting statistical distributions of the random pulse signal group and subsets are obviously asymmetric. Besides, the distribution functions of the whole signal group and its characteristic subsets match well with the lognormal distribution while the natural number as the independent variable. That is to say, the statistical self-similarity character of the random signals’ internal structure is definitely shown by applying the two-parameter analyzing model to deal with them.

A Flexible Multichannel Digital Random Pulse Generator Based on FPGA

The present paper describes a multichannel digital random pulse generator implemented in a 65-nm FPGA device. The random time interval generation is based on inverse transformation method. The output pulse generation rate, pulse width and the probability distribution function (PDF) of each channel might be individually selected by the computer through a USB cable connection. Statistical properties of the output channels can be adjusted and recorded in a fully dynamic flexible manner. The Poisson and uniform PDFs were tested and implemented for up to eight different channels in experiment, however, the implementation of any arbitrary PDF is possible by programming capability of the device as well. Detailed experimental results are expressed in the manuscript. The proposed equipment makes it possible to verify the complicated multichannel detection systems without having the radioactive experimental tests. This is a low cost instrumentation due to the FPGA-based construction.

Comparative analysis of modulation and demodulation methods of the control signals of rail line

Introduction: One of the ways of increasing the noise stability rail circuit is the use more informative waveform of control signal. Use in rail circuit modulated signals gives several informative selective traits in relatively narrow spectrum. The study of features of various modulation and demodulation methods with considering operating conditions of rail circuits is urgent. Purpose: the search for more informative forms of rail line control signal, the search for improved methods of signal processing of control current. Methods: For carrying out researches the method of signals decomposition in Fourier series and the simulation with the method of statistical tests have been sed. Results: Spectrum of frequency shift signal is wider than the spectrum of amplitude shift and phase shift signals by an amount equal to twice the frequency deviation. The research of correlation coherent and incoherent reception methods of rail line control signal has been carried out. In this case, we used the following models of interferences: white Gaussian noise, random pulse sequence and sinusoidal interference. It has been found that the transition from amplitude to frequency shift keying reduces signal/noise ratio by 2...4 dB, depending from the signal level and the type of noise. Losing amplitude shift keying receiver compared with the phase shift keying receiver is 5...6 dB. Conclusions: The use of more advanced methods of modulation and demodulation improves noise stability of rail circuit. When using correlation methods reception phase shift keying provides the best noise stability, and amplitude – the worst.

A PSO-Based UWB Pulse Waveform Design Method

The pulse waveform design method for ultra wideband (UWB) communication based on particle swarm optimization (PSO) technique is discussed, and the performance of UWB system with designed pulse is analyzed. According to analysis, the design of pulse is transformed into a process of finding the minimal solution of a function about weighting coefficient. The weighting coefficients are made certain based on PSO algorithm. The properties such as bit error rate (BER) performance in both single link and multi-user, link budget of the UWB system employing the designed pulse are simulated. Compared with Scholtz’s monocycle and random combined pulse, the results showed that the pulse designed based on the PSO algorithm has better BER performance and communication performance.