Low Noise Sensitivity Research Articles

Estimation of the FRF Through the Improved Local Bandwidth Selection in the Local Polynomial Method

This paper presents a nonparametric method to measure an improved frequency response function (FRF) of a linear dynamic system excited by a random input. Recently, the local polynomial method (LPM) has been proposed as a technique to reduce the leakage errors on FRF measurements. The noise sensitivity of the LPM was similar to that of the classical windowing methods, while the leakage rejection is improved from an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) to an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ). This paper shows a methodology, to automatically tune the parameter of the LPM, viz., the local bandwidth that sets how many neighboring frequency lines are combined in a single-point estimate, to get lower noise sensitivity by increasing the smoothening of the original LPM, without any user interaction. The balance between noise reduction and bias error will be automatically retrieved.

Intelligent Ultraviolet Sensor Composed of GaN-Based Photodiode and N-Channel Metal Oxide Semiconductor Si-Charge Transfer Type Signal Processor

Au/n-GaN Schottky barrier diode combined with Si-charge transfer type signal processor was investigated to realize intelligent UV sensors with low noise and high sensitivity. A 10-nm-thick Au was used for the semitransparent Schottky contact. The dark current–voltage characteristic of the Schottky barrier diode exhibited the ideal factor of 1.28 and barrier height of 1.1 eV. The sensitivity of 26.3 mA/W was obtained at a wavelength of 296 nm for 12 µW/mm2 UV irradiation power. Furthermore, the Au/n-GaN Schottky barrier diode was connected with the Si-charge transfer type signal processor to examine the effectiveness of the combined device for a UV detector. The processor was driven by a programmable function generator. Using the open-circuit voltage Voc as the input signal, 350 mV output was achieved in a single integration cycle. The signal from the Schottky barrier diode was successfully amplified by accumulation operation of the Si-charge transfer type signal processor.

Analysis of the extra-aural dependence of hearing disorders in civil flight personnel

The correlation of incidence of hearing loss and concomitant pathologies in civil pilots with auditory analyzer sensitivity to aviation noise and length of service was investigated with the use of two-factor variance analysis w/o repetition. As a result of screening, 335 people (group-1) had only trace of audiometric noise impact; 108 people (group-2) displayed a sustained loss of hearing (chronic sensorineural hearing loss). In the aggregate, data of the investigation evidences that incidence of cardiovascular diseases (atherosclerosis of aorta and coronary arteries, atherosclerotic cardiosclerosis) and sensorineural hearing loss depend reliably on both individual sensitivity to noise and length of service. As for other pathologies, none of factorial criteria revealed itself as the categorical cause of a pathology. The significance and unit input of causative factor into health disorders vary as in type of non-auditory pathology, so length of flight service, and suggest linkage with the time of incipient loss of hearing. The flight personnel with low noise sensitivity and sustained deafness were diagnosed for a broader variety of extra-aural pathologies than the group with incipient hearing disorders. Variation analysis w/o repetition is applicable to evaluation of the risks of somatic pathologies in flight personnel.

A Modular Differential Dielectric Sensor for Use in Multiphase Separation, Process Measurement, and Control—Part II: Experimental Investigation

Accurate and continuous measurement of the percent water in crude oil production streams (watercut) over 0 to 100% range is critical for petroleum industry. High accuracy and stability are also required for surface measurement to support process control applications aimed at removing trace amounts of oil and particulates from produced water. This paper is a two-part paper—the first part [1] deals with analytical modeling of the differential dielectric sensors (DDS) and the second part (current paper) discusses the results of key experimental investigations. A dedicated closed-loop experimental facility is used to obtain in-line real-time measurement of DDS data in a controlled configuration. A complete description of test facility is presented followed by detailed experimental results. The results show that DDS is unique in its use of very low noise and high sensitivity differential measurements between two identical sensors. In a process control system, DDS shows good measurement stability and is adaptive to composition measurements compensating for changes in oil composition, gas fraction, emulsion state, water salinity, temperature, and flow rate. Because of its auto calibration capability, DDS can also perform real-time calibration for sensor configuration changes caused by factors such as corrosion and erosion.

Wavelength Selection Method with Standard Deviation: Application to Pulse Oximetry

Near-infrared spectroscopy provides useful biological information after the radiation has penetrated through the tissue, within the therapeutic window. One of the significant shortcomings of the current applications of spectroscopic techniques to a live subject is that the subject may be uncooperative and the sample undergoes significant temporal variations, due to his health status that, from radiometric point of view, introduce measurement noise. We describe a novel wavelength selection method for monitoring, based on a standard deviation map, that allows low-noise sensitivity. It may be used with spectral transillumination, transmission, or reflection signals, including those corrupted by noise and unavoidable temporal effects. We apply it to the selection of two wavelengths for the case of pulse oximetry. Using spectroscopic data, we generate a map of standard deviation that we propose as a figure-of-merit in the presence of the noise introduced by the living subject. Even in the presence of diverse sources of noise, we identify four wavelength domains with standard deviation, minimally sensitive to temporal noise, and two wavelengths domains with low sensitivity to temporal noise.

Global adaptive estimation of joint velocities in robotic manipulators

This study presents a method for global estimation of joint velocities in robotic manipulators. The authors consider a non-minimal model of a robotic manipulator and design an adaptive observer capable of handling uncertainties in robot dynamics. Smoothness of the dynamics of the proposed observer allows its easy implementation in comparison with non-smooth observers. Dimension of the proposed observer is shown to be at least 3n where n stands for the manipulator&apos;s degrees of freedom. This number is less than the dimension of most existing globally convergent adaptive observers. Global asymptotic convergence of state estimates to their true values is achieved under no persistency of excitation condition. Furthermore, under noisy position and force measurements, the proposed observer guarantees ultimate boundedness of estimation errors. Simulation results illustrate low noise sensitivity of the proposed observer in comparison with non-smooth observers.

Dynamic Phasor and Frequency Estimates Through Maximally Flat Differentiators

Estimates of the dynamic phasor and its derivatives are obtained through the weighted least squares solution of a Taylor approximation using classical windows as weighting factors. This solution leads to differentiators with ideal frequency response around the fundamental frequency and to very low sidelobe level over the stopband, which implies low noise sensitivity. The differentiators are maximally flat in the interval centered at the fundamental frequency and have a linear phase response. Therefore, their estimates are free of amplitude and phase distortion and are obtained at once. No further patch is needed to improve their accuracy. Examples of dynamic phasor estimates are illustrated under transient conditions. Special emphasis is put on frequency measurements.

Analysis of Digital Speckle‐Pattern Interferometry Fringe Patterns Issued from Transitory Mechanical Loadings

Abstract: During a dynamic mechanical loading, we cannot use a phase‐shifting technique because the mechanical parameters evolve according to the time. This problem can be avoided by the development of algorithms which can extract the mechanical information from only one fringe pattern. In this way, we present two algorithms, the modulated phase correlation (MPC) and the polynomial modulated phase correlation (pMPC). These processes are based on the use of the virtual fringe pattern which locally approaches the real fringe morphology. The similarity degree between real and virtual fringe pattern is estimated by digital correlation technique. When the best similarity is obtained, we suppose that the virtual phase function is very close to the real phase function. Some examples are presented to show the low noise sensitivity of these techniques. So, we propose to use the MPC or the pMPC algorithms to extract the relief from a single interferogram obtained by digital speckle‐pattern interferometry. In this paper, we present experimental tests of impact loading on plates. The frame rate is adapted to the dynamic conditions of loading. Recorded fringe patterns and results of the unwrapped phase demodulated with our algorithms are shown.

A Class of Globally Convergent Velocity Observers for Robotic Manipulators

We present a method for global estimation of joint velocities in rigid manipulators. A class of velocity observers with smooth dynamics are introduced whose structure depend on freely selectable functions and gains giving the flexibility of achieving multiple design objectives at the same time. Unlike most methods, no <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">priori</i> knowledge of an upper bound for velocity magnitude is used. An adaptive version of the observer is also presented to handle a class of structured uncertainties in manipulator model. Simulation example illustrates low noise sensitivity of the globally convergent observer in comparison with semi-globally convergent observers.

MS-qFRET: A quantum dot-based method for analysis of DNA methylation

DNA methylation contributes to carcinogenesis by silencing key tumor suppressor genes. Here we report an ultrasensitive and reliable nanotechnology assay, MS-qFRET, for detection and quantification of DNA methylation. Bisulfite-modified DNA is subjected to PCR amplification with primers that would differentiate between methylated and unmethylated DNA. Quantum dots are then used to capture PCR amplicons and determine the methylation status via fluorescence resonance energy transfer (FRET). Key features of MS-qFRET include its low intrinsic background noise, high resolution, and high sensitivity. This approach detects as little as 15 pg of methylated DNA in the presence of a 10,000-fold excess of unmethylated alleles, enables reduced use of PCR (as low as eight cycles), and allows for multiplexed analyses. The high sensitivity of MS-qFRET enables one-step detection of methylation at PYCARD, CDKN2B, and CDKN2A genes in patient sputum samples that contain low concentrations of methylated DNA, which normally would require a nested PCR approach. The direct application of MS-qFRET on clinical samples offers great promise for its translational use in early cancer diagnosis, prognostic assessment of tumor behavior, as well as monitoring response to therapeutic agents.

A Low Jitter Self-Calibration PLL for 10-Gbps SoC Transmission Links Application

A 2.5GHz 8-phase phase-locked loop (PLL) is proposed for 10-Gbps system on chip (SoC) transmission links application. The proposed PLL has several features which use new design techniques. The first one is a new variable delay cell (VDC) for the voltage control oscillator (VCO). Its advantages over the conventional delay cell are: wide-range output frequency and low noise sensitivity with low KVCO. The second feature is that, the PLL consists of a self-calibration circuit (SCC) which protects the PLL from variations in the process, voltage and temperature (PVT). The third feature is that, the proposed PLL has an 8-phase output frequency and also for avoiding the power/ground (P/G) effect and the substrate noise effect on the PLL, it also has a low jitter output frequency. The PLL is implemented in 0.13-µm CMOS technology. The PLL output jitter is 2.83ps (rms) less than 0.7% of the output period. The total power dissipation is 21mW at 2.5GHz output frequency, and the core area is 0.08mm2.

Design of Amplifier Circuit for the HT-7 Tokamak Thomson Scattering System

Thomson scattering diagnostic is important for measuring electron temperature and density profiles. To improve the signal-to-noise ratio, a silicon avalanche photodiode (APD) with high quantum efficiency, high sensitivity, and high gain up to 100 was adopted to measure the Thomson scattering spectrum. A preamplifier, which has low noise, high bandwidth, and high sensitivity, was designed with suitable transimpedance. Using AD8367 as the post-amplifier, good performance of the APD readout electronics have been obtained. A discussion is presented on the performance of the amplifier using a laser diode to simulate the Thomson scattering light. The test results indicate that the designed circuit has a high amplifying factor and fast rising edge. So reduction of the integral gate of the CAMAC ADC converter can improve the signal-to-noise ratio.

Design and fabrication of a capacitive infrared detector with a floating electrode and thermally isolatable bimorph legs

A new capacitive infrared detector structure that incorporates one electrically floated top electrode that acts as an infrared absorber and two bottom electrodes is proposed and fabricated. The concept begins from an attempt to remove metal lines, the main heat transfer media in the thermal-type infrared detector, from the device's thermal insulation section. A thermal insulation section can be composed without metal lines and instead be solely comprised of an insulator having very low thermal conductivity compared to metals. Therefore, low thermal conductance can be easily achieved with small dimensions of thermal insulation section material. The floating electrode is electrically disconnected from the substrate. Instead, the capacitance change is read only using the two bottom electrodes, which are separated from the absorber and placed on the substrate. The position of the top electrode (infrared absorber) is changed through a bimorph actuation in accordance with the absorption of LWIR (8–12 μm) rays, with an absorptance of 70%. This approach provides an enlarged fill-factor (25%) compared with earlier devices, because the portion of the leg in the pixel area is reduced, whereas the portion of the absorber area is increased. With the small dimension of the thermal insulation section (0.2 × 2 × 10 μm 3), thermal conductance of 1.27 × 10 −7 W/K is achieved. In addition, the shortened leg lends the device a higher spring constant relative to the conventional devices, and therefore a higher signal reading voltage can be achieved, resulting in increased temperature responsivity. With the bimorph-type infrared detector's characteristics of low noise and high sensitivity, the proposed structure can achieve a low NETD value of 12.7 mK.

Industrial silicon detectors, advancements in planar technology

Thirty years ago planar technology was first successfully applied to the manufacture of silicon detectors and this technique led to detectors with better performance than traditional surface barrier and diffused junction types. Today, these detectors are widely used in nuclear and high-energy physics research and are widely deployed in the industrial market as well. These silicon detectors are used in health physics, X-ray fluorescence and diffraction, medical imaging, space applications, and photon (light) detection. As an industrial company, Canberra was challenged to provide detectors with high reliability along with low leakage current, thin entrance windows, a wide range of thicknesses, low noise, and position sensitivity in both single devices and arrays. A new challenge is the readout of pixilated devices. Electronics integrated into or onto the detector chip is a topic of current interest.

Noise-sensitive measure for stochastic resonance in biological oscillators

There has been ample experimental evidence that a variety of biological systems use the mechanism of stochastic resonance for tasks such as prey capture and sensory information processing. Traditional quantities for the characterization of stochastic resonance, such as the signal-to-noise ratio, possess a low noise sensitivity in the sense that they vary slowly about the optimal noise level. To tune to this level for improved system performance in a noisy environment, a high sensitivity to noise is required. Here we show that, when the resonance is understood as a manifestation of phase synchronization, the average synchronization time between the input and the output signal has an extremely high sensitivity in that it exhibits a cusp-like behavior about the optimal noise level. We use a class of biological oscillators to demonstrate this phenomenon, and provide a theoretical analysis to establish its generality. Whether a biological system actually takes advantage of phase synchronization and the cusp-like behavior to tune to optimal noise level presents an interesting issue of further theoretical and experimental research.

Applications of fiber optic sensors for structural health monitoring

Large and complex structures are being built now-a-days and, they are required to be functional even under extreme loading and environmental conditions. In order to meet the safety and maintenance demands, there is a need to build sensors integrated structural system, which can sense and provide necessary information about the structural response to complex loading and environment. Sophisticated tools have been developed for the design and construction of civil engineering structures. However, very little has been accomplished in the area of monitoring and rehabilitation. The employment of appropriate sensor is therefore crucial, and efforts must be directed towards non-destructive testing techniques that remain functional throughout the life of the structure. Fiber optic sensors are emerging as a superior non-destructive tool for evaluating the health of civil engineering structures. Flexibility, small in size and corrosion resistance of optical fibers allow them to be directly embedded in concrete structures. The inherent advantages of fiber optic sensors over conventional sensors include high resolution, ability to work in difficult environment, immunity from electromagnetic interference, large band width of signal, low noise and high sensitivity. This paper brings out the potential and current status of technology of fiber optic sensors for civil engineering applications. The importance of employing fiber optic sensors for health monitoring of civil engineering structures has been highlighted. Details of laboratory studies carried out on fiber optic strain sensors to assess their suitability for civil engineering applications are also covered.

Modeling T cell antigen discrimination based on feedback control of digital ERK responses.

T-lymphocyte activation displays a remarkable combination of speed, sensitivity, and discrimination in response to peptide–major histocompatibility complex (pMHC) ligand engagement of clonally distributed antigen receptors (T cell receptors or TCRs). Even a few foreign pMHCs on the surface of an antigen-presenting cell trigger effective signaling within seconds, whereas 1 × 105–1 × 106 self-pMHC ligands that may differ from the foreign stimulus by only a single amino acid fail to elicit this response. No existing model accounts for this nearly absolute distinction between closely related TCR ligands while also preserving the other canonical features of T-cell responses. Here we document the unexpected highly amplified and digital nature of extracellular signal-regulated kinase (ERK) activation in T cells. Based on this observation and evidence that competing positive- and negative-feedback loops contribute to TCR ligand discrimination, we constructed a new mathematical model of proximal TCR-dependent signaling. The model made clear that competition between a digital positive feedback based on ERK activity and an analog negative feedback involving SH2 domain-containing tyrosine phosphatase (SHP-1) was critical for defining a sharp ligand-discrimination threshold while preserving a rapid and sensitive response. Several nontrivial predictions of this model, including the notion that this threshold is highly sensitive to small changes in SHP-1 expression levels during cellular differentiation, were confirmed by experiment. These results combining computation and experiment reveal that ligand discrimination by T cells is controlled by the dynamics of competing feedback loops that regulate a high-gain digital amplifier, which is itself modulated during differentiation by alterations in the intracellular concentrations of key enzymes. The organization of the signaling network that we model here may be a prototypic solution to the problem of achieving ligand selectivity, low noise, and high sensitivity in biological responses.

Nondestructive evaluation of as-implanted and annealed ultra shallow junctions by photothermal and photoluminescence heterodyne techniques

The control of implantation dose, ion energy and the junction depth after annealing are key points of the on-line metrology for ultra shallow junction fabrication. Nondestructive and non-contact optical methods are examined with respect to their applicability for related tasks. High sensitive low noise photothermal heterodyne (PTH) and photoluminescence heterodyne (PLH) techniques are applied to control implant parameters of 0.5keV B+ – implants both immediately after implantation and after spike annealing. The photothermal response shows that beside dose and energy dependencies monitored after implantation the spike annealing results in a layer with reduced carrier lifetime and mobility. By photoluminescence response the existence of an impurity band and the correlation with the p–n-junction depth is demonstrated by measuring the response of carrier dynamics.

The role of noise sensitivity in the noise–response relation: A comparison of three international airport studies

In order to examine the role of noise sensitivity in response to environmental noise, this paper presents detailed comparisons of socio-acoustic studies conducted around international airports in Amsterdam, Sydney, and London. Earlier findings that noise sensitivity moderates the effect of noise on annoyance were examined to see if they could be replicated in each of the datasets, independent of the technique of measuring noise sensitivity. The relation between exposure to aircraft noise and noise annoyance was studied separately for groups of individuals with low, medium, and high noise sensitivity, with statistical adjustment for relevant confounders. Results support the previous findings that noise sensitivity is an independent predictor of annoyance and adds to the prediction of noise annoyance afforded by noise exposure level by up to 26% of explained variance. There is no evidence of a moderating effect, whereby the covariation between noise exposure level and annoyance is weak for people who score at the extreme high or low end of the sensitivity scale, and strong for people who score in the middle of the sensitivity scale. Generally, noise sensitivity appears to increase annoyance independently of the level of noise exposure after adjustment for relevant confounders. These findings were consistent across the three datasets.

A New Improved Silicon Multi-Cathode Detector (SMCD) for Microanalysis and X-Ray Mapping Applications

Abstract A silicon multi-cathode detector (SMCD) has been developed for microanalysis and x-ray mapping applications. The SMCD has a large active area (∼0.5 cm2), excellent energy resolution, and high count rate capability. The detector utilizes novel structures that have produced very low dark current, high electric field, uniform charge collection, low noise and high sensitivity to low energy x-rays. The detector's spectral response was evaluated using a 55Fe radioisotope source, as well as by fluorescing materials with an x-ray generator. Figure 1 shows a 55Fe spectrum with an energy resolution of 125 eV FWHM at 5.9 keV collected at 12 μs peaking time. This energy resolution has been repeatably measured on many different detectors. To evaluate the high count rate x-ray performance, which is very important for fast x-ray mapping, a Cu sample was fluoresced using a Rh-anode x-ray tube.