Conductance Noise Research Articles

Simultaneous Evaluation of Conductive/Near-Field Noise Suppression in Co-Zr-Nb Film Using Magnetic Circuit

This paper discusses the integrated evaluation of the conductive and near-field noise suppression using magnetic circuit network. The proposed magnetic circuit evaluated the ferromagnetic resonance (FMR) loss and near-field intensity simultaneously and agreed with the measured value. The validity of the evaluation is successfully clarified. It is clarified that the near-field shielding effectiveness is maximized at the intrinsic FMR frequency, because the reluctance of the magnetic film is minimized. It is also clarified that the conductive noise suppression is maximized and the near-field shielding effectiveness is simultaneously minimized at the shifted FMR frequency by the demagnetizing field, because the magnetic circuit resonates. These results demonstrate that the proposed magnetic network model is of great usefulness for developing the integrated design method of the magnetic film-type noise suppressor.

The calculations of conductive noise and heating of the screen in a control cable

Lighting strokes and short circuits (SCs) are the main sources of conductive noise that propagates along control cables and can lead to the failure of microprocessor equipment in the protection and control systems of electric power substations. Two-sided grounding of the screen of a control cable substantially reduces the pulse and high-frequency conductive noise level, but leads to heating of the screen under short-circuit conditions. The existing standards determine the conductive noise and screen heating as a function of screen voltage that is suitable for a single cable. A more general case that takes into account the cable magnetic coupling with other conductors when current is used as a calculation parameter has been considered. The conductive noise at the first pulse of lightning current is determined using the transfer impedance “screen–cable core” or 3D cable model in the general case. To calculate the heating, the formula of GOST (State Standard) 28895-91, which is rejected in modern standards because of the assumption that short-circuit current is invariable (in fact, the current decreases with heating of the screen), has been used. Using this formula in a step algorithm leads to correct results. The cable magnetic coupling with other conductors is expressed as insertion impedance that increases the screen impedance and decreases the current and screen heating. A numerical experiment for a typical cable has shown that conductive noise and heating of the screen of the cable can be substantially reduced because of the parallel laying of conductors. It has been concluded that, to decrease the conductive noise and heating of the screen of a control cable, it is necessary to decrease the screen current.

Exact Nonequilibrium Transport in the Topological Kondo Effect.

A leading candidate for the experimental confirmation of the nonlocal quantum dynamics of Majorana fermions is the topological Kondo effect, predicted for mesoscopic superconducting islands connected to metallic leads. We identify an anisotropic, Toulouse-like, limit of the topological Kondo problem where the full nonequilibrium conductance and shot noise can be calculated exactly. Near the Kondo fixed point, we find novel asymptotic features including a universal conductance scaling function and fractional charge quantization observable via the Fano factor. In the universal regime, our results apply for generic anisotropy and even away from the Kondo limit as long as the system supports an emergent topological Kondo fixed point. Our approach thus provides key new qualitative insights and exact expressions for quantitative comparisons to future experimental data.

Spin-dependent conductance and shot noise in graphene based periodic velocity barrier

We theoretically investigate the spin-dependent conductance and shot noise properties in graphene based periodic velocity barrier structure under Rashba spin–orbit interaction (RSOI). The system consists of graphene sheet in which the Fermi velocity and the electrostatic potential vary in space. We find that the spin-dependent conductance and shot noise in graphene can be efficiently controlled by tuning the Fermi velocity. Moreover, changing the Fermi velocity allows us to change the positions of the Dirac points. The spin-dependent Fano factor without and with spin flip increases and decreases, respectively with increasing the RSOI strength. When Fermi velocity in the barriers is smaller than the velocity outside the barriers, we find that the Fano factor for outgoing electrons with opposite spins has an oscillatory behavior with respect to the RSOI strength. Specifically, as the number of velocity barriers increases or Fermi velocity decreases the spin polarization increases.

Novel Flicker Migration and EMI Noise Reduction Circuit for AC Direct LED Lightings

A novel AC direct light emitting diode (LED) driver circuit that uses flicker mitigation and the electromagnetic interference (EMI) noise reduction method is proposed in this study. This method is based on the current controls of the flicker mitigation capacitor using MOSFET. The core block of the proposed circuit is fabricated as an IC chip. LED lightings are fabricated with the IC chip. The lightings show a flicker index of 0.15, and a 20dBμV peak value and 35dBμV average value of conduction noise margin for EMI regulation. It can be applied to the low power and low cost single chip LED lightings.

First Implementation of a two-stage DC-DC conversion powering scheme for the CMS Phase-2 outer tracker

The ``2S'' silicon strip modules for the CMS Phase-2 tracker upgrade will require two operating voltages. These will be provided via a two-step DC-DC conversion powering scheme, in which one DC-DC converter delivers 2.5 V while the second DC-DC converter receives 2.5 V at its input and converts it to 1.2 V. The DC-DC converters will be mounted on a flex PCB, the service hybrid, together with an opto-electrical converter module (VTRx+) and a serializer (LP-GBT). The service hybrid will be mounted directly on the 2S module. A prototype service hybrid has been developed and its performance has been evaluated, including radiative and conductive noise emissions, and efficiency. In addition system tests with a prototype module have been performed. In this work the service hybrid will be described and the test results will be summarized.

Functional Cortical Connectivity is Disturbed in Patients with Cirrhosis Even When Neuropsychometric Performance is Unimpaired

Introduction: Disordered brain connectivity, generally defined as failure of effective functional integration within/between brain areas, is thought to be the core deficit in several mental health disorders. Functional connectivity is the term used to define the temporal synchrony or correlation among signals of two or more segregated regions. Most methods for assessing functional connectivity within EEG analysis investigate the phase-relationships between the signals from different scalp electrodes. The main drawback of most previous methods, however, is that volume conduction of the signal through cortical membranes, scalp and skin may introduce noise in the signal and bias accurate assessment of connectivity. The phase-lag index (PLI) is a new assessment method that discards volume conduction noise. The aim of this study was to investigate EEG functional connectivity, measured by PLI, in a large well-characterized population of patients with cirrhosis. Methods: The study population comprised of 268 patients with cirrhosis (174 men: 94 women: mean [range] age 55.3 [24-81] yr; 67% alcohol-related). The reference population comprised of 137 healthy individuals (73 men: 94 women; mean age 39.2 [17-75] years). Psychometric performance was assessed using the PHES battery. The raw PHES data were adjusted and scored using UK normative values and patients ranked by their composite final score into the following groups: PHES >0; PHES -2 to -0; PHES -4 to -2; and PHES <-4; composite scores of <2SD below mean reference values were considered abnormal. EEG recordings were undertaken for 10 minutes in a state of eyes-closed, relaxed, wakefulness. The PLI was calculated and divided into standardized frequency bands viz.: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz) and beta (12–32 Hz), employing the implementation from The Neurophysiological Biomarker Toolbox (NBT) (http://www.nbtwiki.net/). Results: Significant EEG changes were observed in patients in whom the PHES would ordinarily be considered normal viz. PHES scores -2 to 0, compared to the reference population: Delta (0.139 ± 0.014 vs. 0.144 ± 0.014; P < 0.01), Alpha (0.141 ± 0.036 vs. 0.154 ± 0.036; P < 0.01) and Beta (0.065 ± 0.008 vs. 0.069 ± 0.011; P < 0.05). More pronounced changes, were observed with increasing psychometric impairment; viz. PHES scores -4 to -2: Delta (0.138 ± 0.012 vs. 0.144 ± 0.014; P < 0.01), Theta (0.117 ± 0.018 vs. 0.103 ± 0.009; P < 0.0001): Alpha (0.124 ± 0.026 vs. 0.154 ± 0.036; P < 0.0001) and Beta (0.062 ± 0.006 vs. 0.069 ± 0.011; P < 0.0001). No significant differences were observed, by cirrhosis aetiology. Significant correlations were observed between the results of the individual psychometric tests and functional connectivity in all but the delta band. Conclusion: Cortical connectivity is disturbed in patients with cirrhosis even when neuropsychometric performance is unimpaired. These finding attests to the spectral nature of the neuropsychiatric changes in this patient population and may provide a new and objective mean for assessments and early identification of clinically relevant hepatic encephalopathy; further validation is needed. The authors have none to declare.

Effects of Small-World Rewiring Probability and Noisy Synaptic Conductivity on Slow Waves: Cortical Network.

Physiological rhythms play a critical role in the functional development of living beings. Many biological functions are executed with an interaction of rhythms produced by internal characteristics of scores of cells. While synchronized oscillations may be associated with normal brain functions, anomalies in these oscillations may cause or relate the emergence of some neurological or neuropsychological pathologies. This study was designed to investigate the effects of topological structure and synaptic conductivity noise on the spatial synchronization and temporal rhythmicity of the waves generated by cells in the network. Because of holding the ability of clustering and randomizing with change of parameters, small-world (SW) network topology was chosen. The oscillatory activity of network was tried out by manipulating an insulated SW, cortical network model whose morphology is very close to real world. According to the obtained results, it was observed that at the optimal probabilistic rates of conductivity noise and rewiring of SW, powerful synchronized oscillatory small waves are generated in relation to the internal dynamics of cells, which are in line with the network's input. These two parameters were observed to be quite effective on the excitation-inhibition balance of the network. Accordingly, it may be suggested that the topological dynamics of SW and noisy synaptic conductivity may be associated with the normal and abnormal development of neurobiological structure.

Computer Simulation of Noise Effects of the Neighborhood of Stimulus Threshold for a Mathematical Model of Homeostatic Regulation of Sleep-Wake Cycles

The noise effects on a homeostatic regulation of sleep-wake cycles’ neuronal mathematical model determined by the hypocretin/orexin and the local glutamate interneurons spatiotemporal behaviors are studied within the neighborhood of stimulus threshold in this work; the neuronal noise added to the stimulus, the conductance, and the activation variable of the modulation function are investigated, respectively, based on a circadian input skewed in sine function. The computer simulation results suggested that the increased amplitude of external current input will lead to the fact that awakening time is advanced but the sleepy time remains the same; for the bigger conductance and modulation noise, the regulatory mechanism of the model sometimes will be collapsed and the coupled two neurons of the model show very irregular activities; the falling asleep or wake transform appears at nondeterminate time.

Numerical approach of the quantum circuit theory

In this paper we develop a numerical method based on the quantum circuit theory to approach the coherent electronic transport in a network of quantum dots connected with arbitrary topology. The algorithm was employed in a circuit formed by quantum dots connected each other in a shape of a linear chain (associations in series), and of a ring (associations in series, and in parallel). For both systems we compute two current observables: conductance and shot noise power. We find an excellent agreement between our numerical results and the ones found in the literature. Moreover, we analyze the algorithm efficiency for a chain of quantum dots, where the mean processing time exhibits a linear dependence with the number of quantum dots in the array.

Evaluating the Optoelectronic Quality of Hybrid Perovskites by Conductive Atomic Force Microscopy with Noise Spectroscopy.

Organic-inorganic hybrid perovskite solar cells have emerged as promising candidates for next-generation solar cells. To attain high photovoltaic efficiency, reducing the defects in perovskites is crucial along with a uniform coating of the films. Also, evaluating the quality of synthesized perovskites via facile and adequate methods is important as well. Herein, CH3NH3PbI3 perovskites were synthesized by applying second solvent dripping to nonstoichiometric precursors containing excess CH3NH3I. The resulting perovskite films exhibited a larger average grain size with a better crystallinity compared to that from stoichiometric precursors. As a result, the performance of planar perovskite solar cells was significantly improved, achieving an efficiency of 14.3%. Furthermore, perovskite films were effectively analyzed using a conductive AFM and noise spectroscopy, which have been uncommon in the field of perovskite solar cells. Comparing the topography and photocurrent maps, the variation of photocurrents in nanoscale was systematically investigated, and a linear relationship between the grain size and photocurrent was revealed. Also, noise analyses with a conductive probe enabled examination of the defect density of perovskites at specific grain interiors by excluding the grain-boundary effect, and reduced defects were clearly observed for the perovskites using CH3NH3I-rich precursors.

Low-energy spectra of differential conductivity and shot noise in tunnel junctions based on superconductors with suppression of the order parameter at the S-N interface

The possibility of an anomalous structure in the differential conductivity of tunnel junctions based on high-temperature superconductors as a result of degradation of their surface layer is analyzed. This feature is in the form of two peaks near an energy gap separated by a region of suppressed conductivity. One peak is usually high and sharp, while the other is much more spread out. Differential conductivity and shot noise spectra in contacts of a normal injector with s- and d-type superconductors are calculated and compared. It is shown that combined measurements of these two characteristics can provide new information on the kinetics of transport processes in these structures.

Using Noise and Fluctuations for In Situ Measurements of Nitrogen Diffusion Depth

In manufacturing processes involving diffusion (of C, N, S, etc.), the evolution of the layer depth is of the utmost importance: the success of the entire process depends on this parameter. Currently, nitriding is typically either calibrated using a “post process” method or controlled via indirect measurements (H2, O2, H2O + CO2). In the absence of “in situ” monitoring, any variation in the process parameters (gas concentration, temperature, steel composition, distance between sensors and furnace chamber) can cause expensive process inefficiency or failure. Indirect measurements can prevent process failure, but uncertainties and complications may arise in the relationship between the measured parameters and the actual diffusion process. In this paper, a method based on noise and fluctuation measurements is proposed that offers direct control of the layer depth evolution because the parameters of interest are measured in direct contact with the nitrided steel (represented by the active electrode). The paper addresses two related sets of experiments. The first set of experiments consisted of laboratory tests on nitrided samples using Barkhausen noise and yielded a linear relationship between the frequency exponent in the Hooge equation and the nitriding time. For the second set, a specific sensor based on conductivity noise (at the nitriding temperature) was built for shop-floor experiments. Although two different types of noise were measured in these two sets of experiments, the use of the frequency exponent to monitor the process evolution remained valid.

Symmetrical SOI MESFET with a dual cavity region (DCR-SOI MESFET) to promote high-voltage and radio-frequency performances

A novel symmetrical SOI-MESFET is reported to enhance high-voltage and radio-frequency performances, successfully. Two p-type cavity regions with certain features are embedded in the proposed structure to control the channel region. The cavity regions absorb the channel potential lines resulting in an evener potential profile throughout the channel region. Hence, the critical electric field at the end of gate edge near the drain will be considerably reduced thus increasing the breakdown voltage, finally. A comprehensive comparison in terms of breakdown voltage, radio-frequency parameters, drain-source conductance and minimum noise figure shows that the reported new device reaches a superior electrical performance when compared with a conventional SOI MESFET.

패시브 공진 스너버를 이용한 플라이백형 ZVS PWM DC-DC 컨버터의 특성해석

In this paper, a high frequency flyback type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of active power switches and a flyback high frequency transformer. In addition to these, passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view and the comparative electromagnetic conduction and radiation noise characteristics of both DC-DC power converter circuits are also depicted.

Electrical conduction noise and its correlation with structural properties of Cu2ZnSnS4 thin films

Cu2ZnSnS4 (CZTS) thin films have been deposited by ultrasonic assisted chemical vapor deposition in a single step process at different substrate temperatures and structural, morphological, electrical and conduction noise characteristics of the CZTS thin films have been studied. Single phase CZTS thin films are formed at 275 °C and 325 °C deposition temperatures, whereas the CZTS thin film deposited at 375 °C showed secondary phase also. The crystallinity of the films improves and resistivity decreases with the increases of the deposition temperature. The temperature dependent electrical conductivity of the films reveals that in the temperature range 300–250 K, thermally activated conduction is observed. The conduction noise in the CZTS thin films, exhibits 1/f noise in the low frequency region and found to be strongly dependent on the film deposition temperatures. The film deposited at 275 °C and 375 °C shows larger conduction noise, whereas the film deposited at 325 °C shows smaller noise. For the low frequency 1/f noise, the value of α is also found to be the minimum for the film deposited at 325 °C. The higher value of conduction noise in the film deposited at 275 °C is related to poor crystallinity and less compact morphology. For the film deposited at 375 °C, crystallinity and compactness improves, but the presence of the secondary phases seems to be responsible for generating higher noise. The smallest conduction noise of the film deposited at 325 °C is due to single phase film with better crystallinity and smaller trap density ∼5.1 × 1015 cm−2 eV−1.

Hopping conduction and LF noise in structures with Ge nanoclusters grown on oxidized Si(001)

Conductivity, capacitance, and the low-frequency noise in structures with Ge nanoclusters grown on oxidized Si(001) have been investigated for the temperature range of 120–290 K and frequencies from 1 kHz to 1 MHz in co-planar geometry. The Mott’s variable range hopping through quasi-band of localized states at the Fermi level of nanoclusters and their interfaces was found to be the dominant transport mechanism in the surface conductivity channel. The quasi-band width was found to be about 110 meV, while the middle is located at Ev + 140 meV. The maximum of reduced conductivity and capacitance were observed under conditions when Fermi level is in the middle of this band. A significant increase of the 1/f noise level with decreasing temperature found for the structures studied was ascribed to accompany hopping transport of charge carriers within the quasi-band with a high density of localized states.

Enhanced current noise correlations in a Coulomb-Majorana device

Majorana bound states (MBSs) nested in a topological nanowire are predicted to manifest nonlocal correlations in the presence of a finite energy splitting between the MBSs. However, the signal of the nonlocal correlations has not yet been detected in experiments. A possible reason is that the energy splitting is too weak and seriously affected by many system parameters. Here we investigate the charging energy induced nonlocal correlations in a hybrid device of MBSs and quantum dots. The nanowire that hosts the MBSs is assumed in proximity to a mesoscopic superconducting island with a finite charging energy. Each end of the nanowire is coupled to one lead via a quantum dot with resonant levels. With a floating superconducting island, the devices shows a negative differential conductance and giant super-Poissonian shot noise, due to the interplay between the nonlocality of the MBSs and dynamical Coulomb blockade effect. When the island is strongly coupled to a bulk superconductor, the current cross correlations at small lead chemical potentials are negative by tuning the dot energy levels. In contrast, the cross correlation is always positive in a non-Majorana setup. This difference may provide a signature for the existence of the MBSs.

Enhancing detection sensitivity of SST-1 Thomson scattering experiment

Thomson Scattering System (TSS) is the main diagnostic to extract electron temperature and density of steady state superconducting (SST-1) tokamak plasma. Silicon avalanche photo diode is used with low noise and fast signal conditioning electronics (SCE) to detect incoming Thomson scattered laser photons. A stringent requirement for the measurement is to detect high speed and low level light signal (detection of 100 numbers of Thomson scattered photons for 50ns pulse width at input of active area of detector) in the presence of wide band electro-magnetic interference (EMI) noise. The electronics and instruments for different sub-systems kept in laboratory contribute to the radiated and conductive noise in a complex manner to the experiment, which can degrade the resultant signal to noise ratio (SNR <1). In general a repeated trial method with flexible grounding scheme are used to improve system signal to noise ratio, which is time consuming and less efficient. In the present work a simple, robust, cost-effective instrumentation system is used for the measurement and monitoring with improved ground scheme and shielding method to minimize noise, isolating the internal sub-system generated noise and external interference which leads to an improved SNR.

High frequency cut-off in 1/f conductivity noise of hole-doped La1−xCaxMnO3 manganite single crystals

High frequency bias and temperature-dependent Lorentzian cut-off has been observed in the 1/f spectra of the conductivity fluctuations in low hole-doped ferromagnetic insulating La1−xCaxMnO3 manganite at low temperatures. The cut-off frequency depends on dc current bias and temperature. The high frequency cut-off has been tentatively associated with intrinsic limits of the appearance of 1/f noise in the hopping regime of the Coulomb glass state. The assumption is validated by the fact that the Efros–Shklovskii temperature , estimated from the fit of the model to the experimentally measured temperature dependence of the cut-off frequency, has the same value as the temperature evaluated independently from the temperature dependence of the resistivity in the corresponding temperature range.