Random Noise Sources Research Articles

Sound Absorption Performance of Sugar Palm Trunk Fibers

The purpose of this research is to investigate the effect of bulk density, thickness, and air gap to sound absorption performance on absorber based sugar palm trunk fibers. The fibers were obtained from solid waste on Small-Medium Enterprises of sago flour processing in Klaten, Central Java, Indonesia. The absorber specimens were formed from the fibers using a simple press molding in an oven at 150 °C. According to ISO 10534-2, the absorber samples were tested using two microphones impedance tube with random noise source to get the curve of the sound absorption coefficient. The result shows that the absorption performance can be improved by increasing bulk density and increasing of sample thickness. Especially at low frequencies, improvement of the sound absorption coefficient can be achieved (NAC > 0.8) by applying the air gap behind the sample. The best performance of absorber based sugar palm trunk fiber can be achieved for (1 000 to 6 000) Hz range frequency.

Quantum spatial search on graphs subject to dynamical noise

We address quantum spatial search on graphs and its implementation by continuous-time quantum walks in the presence of dynamical noise. In particular, we focus on search on the complete graph and on the star graph of order $N$, proving that also the latter is optimal in the computational limit $N \gg 1$, being nearly optimal also for small $N$. The noise is modeled by independent sources of random telegraph noise (RTN), dynamically perturbing the links of the graph. We observe two different behaviours depending on the switching rate of RTN: fast noise only slightly degrades performance, whereas slow noise is more detrimental and, in general, lowers the success probability. In particular, we still find a quadratic speed-up for the average running time of the algorithm, while for the star graph with external target node we observe a transition to classical scaling. We also address how the effects of noise depend on the order of the graphs, and discuss the role of the graph topology. Overall, our results suggest that realizations of quantum spatial search are possible with current technology, and also indicate the star graph as the perfect candidate for the implementation by noisy quantum walks, owing to its simple topology and nearly optimal performance also for just few nodes.

Noise Properties of the Faraday Effect Measurement Systems

Nowadays, nanomagnetic devices have a main role in computer industries. To observe magnetic features of the nanomagnetic device, Magneto-optical effects such as Kerr effect and Faraday effect can be used. We report the fabrication of the Faraday effect measurement setup for characterization of nanomagnetic elements. With achievement of low noise measurement configuration by precision electronic measurements, Faraday effect was observed. The essence of the experiment is to measure a light intensity that is transmitted from the transparent magnetic material. Light intensity is measured by a photodiode detector (Hamamatsu S5870) which produced the laser-induced photocurrent. Using transimpedance amplifier, the signal is converted to the voltage which is measured by the lock in amplifier (Stanford Research SR810). By performing the measurement at different lock-in frequencies and different analyzer angles, we systematically analyzed various random noise sources and their effect to the signal to noise ratio. The interestingly, the noise characteristics of the measured photocurrent exhibit a 1/f noise behavior with a scaling exponent practically 1.

Streaming orthogonal prediction filter in the t-x domain for random noise attenuation

In seismic exploration, there are many sources of random noise, for example, scattering from a complex surface. Prediction filters (PFs) have been widely used for random noise attenuation, but these typically assume that the seismic signal is stationary. Seismic signals are fundamentally nonstationary. Stationary PFs fail in the presence of nonstationary events, even if the data are cut into overlapping windows (“patching”). We have developed an adaptive PF method based on streaming and orthogonalization for random noise attenuation in the [Formula: see text]-[Formula: see text] domain. Instead of using patching or regularization, the streaming orthogonal PF (SOPF) takes full advantage of the streaming method, which generates the signal value as each new noisy data value arrives. The streaming signal-and-noise orthogonalization further improves the signal recovery ability of the SOPF. The streaming characteristic makes the proposed method faster than iterative approaches. In comparison with [Formula: see text]-[Formula: see text] deconvolution and [Formula: see text]-[Formula: see text] regularized nonstationary autoregression, we tested the feasibility of the proposed method in attenuating random noise on two synthetic data sets. Field-data examples confirm that the [Formula: see text]-[Formula: see text] SOPF has a reasonable denoising ability in practice.

Dynamics of entanglement and state-space trajectories followed by a system of four-qubit in the presence of random telegraph noise: common environment (CE) versus independent environments (IEs)

The paper investigates the dynamics of entanglement and explores some geometrical characteristics of the trajectories in state space, in four-qubit Greenberger-Horne-Zeilinger (GHZ) - and W-type states, coupled to common and independent classical random telegraph noise (RTN) sources. It is shown from numerical simulations that: (i) the dynamics of entanglement depends drastically not only on the input configuration of the qubits and the presence or absence of memory effects, but also on whether the qubits are coupled to the RTN in a CE or IEs; (ii) a considerable amount of entanglement can be indefinitely trapped when the qubits are embedded in a CE; (iii) the CE configuration preserves better the entanglement initially shared between the qubits than the IEs configuration, however, for W-type states, there is a period of time and/or certain values of the purity for which, the opposite can be found. Thanks to the results obtained in our earlier works on three-qubit models, we are able to conclude that entanglement becomes more robustly protected from decay when the number of qubits of the system increases. Finally, we find that the trajectories in state space of the system quantified by the quantum Jensen Shannon divergence (QJSD) between the time-evolved states of the qubits and some reference states may be curvilinear or chaotic.

A non-Gaussian option pricing model based on Kaniadakis exponential deformation

A way to make financial models effective is by letting them to represent the so called “fat tails”, i.e., extreme changes in stock prices that are regarded as almost impossible by the standard Gaussian distribution. In this article, the Kaniadakis deformation of the usual exponential function is used to define a random noise source in the dynamics of price processes capable of capturing such real market phenomena.

Seismic Exploration Random Noise on Land: Modeling and Application to Noise Suppression

In seismic exploration, random noise suppression is one of the key problems in seismic data processing. For random noise attenuation, the most important thing is the understanding of seismic random noise generation and propagation. Seismic random noise is considered as temporal and spatial random processes, and it can be analyzed only qualitatively for now, due to its high variability. In this paper, we classify seismic random noise sources by their generation factors and simulate the random noise of the desert in West China. According to Green’s function, it can be assumed that seismic random noise sources are point-like sources that are distributed around geophones. A seismic random noise record is taken as the superimposed wave field exited by all the independent sources in a homogeneous isotropy half-infinite surface. Based on the wind vibration theory and preliminary study about ambient vibrations, the noise source functions are determined. We obtain the waveforms of different kinds of noise by solving the inhomogeneous wave equations and analyze the characteristics qualitatively and quantitatively. The seismic synthetic record with a 1.6-s time and 250-m distances is obtained, and the characteristics are compared between the simulated and the real noise record in time domain and space domain, respectively. The comparative results show the same characteristics of the simulated noise and the real noise, which demonstrates the feasibility of the proposed method. According to the noise modeling, it is known that the near-field cultural noise is the main component of the random noise in the desert, on the basis of which complex diffusion filtering is selected. The filtered results by complex diffusion filtering is compared with the results of time–frequency peak filtering, which is a popular filtering method of seismic random noise suppression in recent years. The comparative results show that complex diffusion filtering is more suitable for the noise of the desert in the Tarim Basin. This result proves that seismic random noise modeling can provide the guidance for noise attenuation. It lays a foundation for researching the propagation characteristics and better attenuation of seismic random noise in the future.

The Research of the Characteristics of the Ocean Ambient Noise Under Varying Environment

The parabolic equation approximation method is applied to build the model of the vertical spatial correlation and vertical directivity characteristics of ocean ambient noise under varying environment. The random noise sources which have the same intensity are represented by uncorrelated monopoles distributed uniformly over an infinite plane located a certain depth below the sea surface. The spatial properties of noise field are analyzed under the varying ocean environments which are the slope, seamount and varying sound speed profiles. According to the results of simulation, the varying environment changes the propagating paths of noise, so the spatial properties (correlation and directionality) of the noise field change. When the remote noise intensity increases, the noise intensity in low grazing angle and the vertical correlations of nose field become stronger. At last, the experiment’s results support the results of simulation.

Generative adversarial networks recover features in astrophysical images of galaxies beyond the deconvolution limit

Abstract Observations of astrophysical objects such as galaxies are limited by various sources of random and systematic noise from the sky background, the optical system of the telescope and the detector used to record the data. Conventional deconvolution techniques are limited in their ability to recover features in imaging data by the Shannon–Nyquist sampling theorem. Here, we train a generative adversarial network (GAN) on a sample of 4550 images of nearby galaxies at 0.01 < z < 0.02 from the Sloan Digital Sky Survey and conduct 10× cross-validation to evaluate the results. We present a method using a GAN trained on galaxy images that can recover features from artificially degraded images with worse seeing and higher noise than the original with a performance that far exceeds simple deconvolution. The ability to better recover detailed features such as galaxy morphology from low signal to noise and low angular resolution imaging data significantly increases our ability to study existing data sets of astrophysical objects as well as future observations with observatories such as the Large Synoptic Sky Telescope (LSST) and the Hubble and James Webb space telescopes.

Measurement of the structural admittance matrix using external random noise sources

The structural admittance Ys also called the structural Green’s function characterizes the vibration, radiation, and scattering physics of a vibrator. When it is known, the vibration of the radiating surface, and hence the acoustic radiation from the surface, is also known for any specified surface load. We demonstrate in this talk that Ys can be constructed when the object is placed in an isotropic random noise field. This construction consists of ensemble averages of cross-correlations of the resulting total normal velocity and total pressure (incident plus scattered) measured over the complete surface of the object. However, the measurement of the surface fields could be prohibitive as the temporal frequency of interest increases. Instead of a surface measurement, one can use a dual conformal surface of microphones placed near to the object together with near-field acoustical holography (NAH) to determine the fields on the surface via the back projection capability of NAH. Although a large number of sensors may be required, the advent of inexpensive MEMS microphones combined with a 3D printing capability to construct the support structure makes this measurement very plausible. [Work supported by the Office of Naval Research.]

Particle and Photon Detection: Counting and Energy Measurement.

Fundamental limits for photon counting and photon energy measurement are reviewed for CCD and CMOS imagers. The challenges to extend photon counting into the visible/nIR wavelengths and achieve energy measurement in the UV with specific read noise requirements are discussed. Pixel flicker and random telegraph noise sources are highlighted along with various methods used in reducing their contribution on the sensor’s read noise floor. Practical requirements for quantum efficiency, charge collection efficiency, and charge transfer efficiency that interfere with photon counting performance are discussed. Lastly we will review current efforts in reducing flicker noise head-on, in hopes to drive read noise substantially below 1 carrier rms.

Analyses and Applications of the Second-Order Cross Correlation in the Passive Imaging

AbstractThe first-order cross correlation and corresponding applications in the passive imaging are deeply studied by Garnier and Papanicolaou in their pioneer works. In this paper, the results of the first-order cross correlation are generalized to the second-order cross correlation. The second-order cross correlation is proven to be a statistically stable quantity, with respective to the random ambient noise sources. Specially, with proper time scales, the stochastic fluctuation for the second-order cross correlation converges much faster than the first-order one. Indeed, the convergent rate is of order , with 0 < α < 1. Besides, by using the stationary phase method in both homogeneous and scattering medium, similar behaviors of the singular components for the second-order cross correlation are obtained. Finally, two imaging methods are proposed to search for a target point reflector: One method is based on the imaging function, and has a better signal-to-noise rate; Another method is based on the geometric property, and can improve the bad range resolution of the imaging results.

소음원 영상화 기술의 성능에 보간 함수가 미치는 영향 비교

To find the location of a random noise source present in the three-dimensional space is required at least four microphones. Using four microphones distributed in a three-dimensional space, noise source imaging technique was applied and evaluated on their performance. To compensate resolution problem which comes from both the position of the sensor array is fixed and the sampling frequency is low, up-sampling technique and interpolation function were applied. Five different interpolation methods were applied such as zero-padding, zero-order hold, first-order hold, spline function, and random signal padding. The up-sampling rate were chosen by two, four, eight times, and counting up 16 times. As a result, it was possible to more accurately estimate the position of the noise source according to the higher of the up-sampling rate. It also found that the first-order hold and the spline function`s performance were slightly falling relative to other methods.

Robust frequency estimation in three‐phase power systems using correntropy‐based adaptive filter

In this study, the authors propose a robust adaptive algorithm for frequency estimation in three-phase power systems when the voltage readings are corrupted by random noise sources. The proposed algorithm employs the Clarke's transformed three-phase voltage (a complex signal) and augmented complex statistics to deal with both of balanced and unbalanced system conditions. To derive the algorithm, a widely linear predictive model is assumed for the Clarke's transformed signal where the frequency of system is related to the parameters of this model. To estimate the model parameters with noisy voltage reading, they utilise the notions of maximum correntropy criterion and gradient-ascent optimisation. The proposed algorithm has the computational complexity of the popular complex least-mean-squares (CLMS) algorithm, along with the robustness that is obtained by using higher-order moments beyond just second-order moments. They compare the performance of the proposed algorithm with a recently introduced augmented CLMS (ACLMS) algorithm in different conditions, including the voltage sags and presence of impulsive noises and and higher-order harmonics. Their simulation results demonstrate that the proposed algorithm provides improved frequency estimation performance compared with ACLMS especially when the measured voltages are corrupted by impulsive noise.

Analysis of mirror soft-x-ray-EUV scattering using generalized continuous growth model of multiscale reliefs.

Combined computer simulations of the growth of multilayer mirrors and their exact differential reflection coefficients in the soft-x-ray-EUV range have been conducted. The proposed model describes the variation of the surface roughness of the multilayer Al/Zr mirror boundary profiles taking into account a random noise source. Theoretically calculated Al/Zr boundary profiles allow one to know real rough boundary statistics including rms roughnesses and correlation lengths and, to obtain rigorously EUV specular and diffuse reflection coefficients. The proposed integrated approach opens up a way to performing exact theoretical studies similar in accuracy to results obtained by quantitative microscopy investigations of nanoreliefs and synchrotron radiation measurements.

Photometric Defocus Observations of Transiting Extrasolar Planets

We have carried out photometric follow-up observations of bright transiting extrasolar planets using the CbNUOJ 0.6m telescope. We have tested the possibility of obtaining high photometric precision by applying the telescope defocus technique allowing the use of several hundred seconds in exposure time for a single measurement. We demonstrate that this technique is capable of obtaining a root-mean-square scatter of order sub-millimagnitude over several hours for a V $\sim$ 10 host star typical for transiting planets detected from ground-based survey facilities. We compare our results with transit observations with the telescope operated in in-focus mode. High photometric precision is obtained due to the collection of a larger amount of photons resulting in a higher signal compared to other random and systematic noise sources. Accurate telescope tracking is likely to further contribute to lowering systematic noise by probing the same pixels on the CCD. Furthermore, a longer exposure time helps reducing the effect of scintillation noise which otherwise has a significant effect for small-aperture telescopes operated in in-focus mode. Finally we present the results of modelling four light-curves for which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes have been achieved.

Improving automatic first-arrival picking by supervirtual interferometry: examples from Saudi Arabia

The objective of this study is to test the feasibility of using the supervirtual seismic interferometry method for improving automatic picking of first arrivals in petroleum seismic data. Fundamentally, interferometry is a mathematical technique used to position virtual sources at the location of actual receivers to gain the power of additional signals utilizing the physics of wavefield reciprocity and time reversal. Supervirtual interferometry extends the technique to far source-receiver offsets having very low signal-to-noise ratios. The benefits gained in more accurate first-arrival picking are significant, especially when near-surface velocity variations are severe and can have a detrimental impact on accurately mapping subtle structures. The supervirtual workflow consists of the following: windowing around first arrivals, cross-correlation, source stacking, convolution, and receiver stacking. The workflow is tested on a 2-D synthetic seismic data. In addition, the workflow has been tested on a 2-D petroleum seismic data from Saudi Arabia with considerable attenuation of first arrivals with offset. Results show that the workflow greatly improves first arrivals at all offsets, particularly at far offsets. Furthermore, testing the effect of a localized continuous random-noise source (e.g., due to machines) on the method’s performance show that such noise does not affect the method’s performance, which might be due to extensive trace mixing by the cross-correlation and convolution operations.

HiTSelect: a comprehensive tool for high-complexity-pooled screen analysis.

Genetic screens of an unprecedented scale have recently been made possible by the availability of high-complexity libraries of synthetic oligonucleotides designed to mediate either gene knockdown or gene knockout, coupled with next-generation sequencing. However, several sources of random noise and statistical biases complicate the interpretation of the resulting high-throughput data. We developed HiTSelect, a comprehensive analysis pipeline for rigorously selecting screen hits and identifying functionally relevant genes and pathways by addressing off-target effects, controlling for variance in both gene silencing efficiency and sequencing depth of coverage and integrating relevant metadata. We document the superior performance of HiTSelect using data from both genome-wide RNAi and CRISPR/Cas9 screens. HiTSelect is implemented as an open-source package, with a user-friendly interface for data visualization and pathway exploration. Binary executables are available at http://sourceforge.net/projects/hitselect/, and the source code is available at https://github.com/diazlab/HiTSelect.

Statistical properties of the seismic noise field: influence of soil heterogeneities

Seismic noise is generally considered as a reproducible and temporarily stationary natural source of energy. Based on the recording of seismic noise by a dense temporary network installed at various sites in the city of Dushanbe we have investigated the variations of the 3D average squared soil displacement on different time scales. This allows studying the statistical features of the soil motion due to the seismic noise wave field properties and its dependency on the near-surface geology. A selfaffine random medium is the most appropriate description of the heterogeneous material properties of the geological structures. In particular, the intrinsic properties show a clear dependency on the local shallow subsoil conditions with consolidated soils being characterized by a nearly ballistic behavior for short time scales. A distinct multi-fractal behavior, being characterized by a crossover to a diffusive character for longer time scales, indicates a long-range anti-correlated motion which can be seen as a mixture between uncorrelated noise and white noise. Although in a strict sense the seismic wave field is not completely isotropic, an ultimate pre-condition for a diffusive wave field, the deviations compared to a uniform distribution are rather small, meaning that the emergence of the Green's function is effective for all network sites after a sufficient self-averaging process that is provided by the scattering and the random spatial-temporal noise source distribution. By analyzing the transition in the dynamical character of the energy propagation process allows studying seismic noise from a different perspective. Complementary to a 1D description of the wave propagation for a diffusive field (e.g. Kawase et al. 2011) this enables quantifying also the 2D variability and the multiple scattering required to produce diffusive wave field.

A WIDE-RANGE PROGRAMMABLE PULSE WIDTH CONTROLLER

A very simple, wide range and programmable pulse width controller or duty cycle corrector (DCC) is presented. Simulating the circuit in 0.35 μm Complementary MOSFET (CMOS) technology shows that the frequency range of the input signal can be within 250 MHz to 1.6 GHz, with a duty cycle of 30–70%. The proposed circuit generates an output signal with programmable duty cycle in the range of 30–70% with steps of 10% which could be extended to more steps by simple variations. The systematic peak-to-peak jitter at center frequency (1 GHz) is 1ps, while adding a random noise source of 5% of the power supply, increases it to 13 ps. the power consumption at maximum speed (1.6 GHz) is 4.9 mW. Monte Carlo simulations show maximum of 3.4% error at the 1.5 GHz input frequency and 70% output duty cycle.