Suppression Of Drift Research Articles

Analysis and suppression of drain current drift in graphene FETs

The cause of drain current (ID) drift in graphene field-effect transistors is analyzed and a method to suppress the drift is proposed. By analyzing ID-time characteristics, a condition of reasonable gate, drain and source biases (VG, VD, and VS) is proposed to suppress ID drift. Based on this result, we find a condition for VG during off-time (Vbase), VD, and VS in pulsed I-V measurement to obtain the intrinsic ID-VG curves, and analyze the effect of Vbase on the Dirac point shift. Through an analysis of ID-time characteristics depending on VG, ID drift according to the range of VG is explained.

Few-femtosecond-resolution characterization and suppression of excess timing jitter and drift in indoor atmospheric frequency comb transfer

We characterize the timing jitter spectral density of the time-of-flight (TOF) in the indoor atmospheric transfer of optical pulse train over 10 decades of Fourier frequency range (10 μHz - 100 kHz) with sub-100-as resolution using a balanced optical cross-correlator (BOC). Based on the well-known theory for atmospheric transfer of a laser beam, we could fit the measured timing jitter power spectral density to the theory and analyze it with a fairly good agreement from 20 mHz to 10 Hz Fourier frequency range. Moreover, we demonstrate that the BOC-based timing stabilization method can suppress the excess fluctuations in timing from >200 fs (rms) to 2.6 fs (rms) maintained over 130 hours when an optical pulse train is transferred over a 76.2-m long free-space beam path in laboratory environment. The demonstrated stabilization result corresponds to 4 × 10(-20) overlapping Allan deviation at 117,000 s averaging time.

Application of Kalman Filtering Techniques and Simulation Analysis

The principles and methods of their combined mode SINS/celestial navigation, and applying the theory of error state Kalman filter integrated navigation systems were analyzed. Derivation of a new measurement equation, written Kalman filtering process filter analysis was carried out to prove that the model has a good combination of inertial devices drift suppression effect.

Real-time calibration of laser absorption spectrometer using spectral correlation performed with an in-line gas cell

A real-time drift correction and calibration method using spectral correlation based on a revolving in-line gas cell for laser-based spectroscopic trace-gas measurements has been developed and evaluated experimentally. This technique is relatively simple to implement in laser spectroscopy systems and assures long-term stability of trace-gas measurements by minimizing the effects of external sources of drift in real-time. Spectroscopic sensitivity sufficient for environmental monitoring and effective drift suppression has been achieved for long-term measurements of CO₂ with a quantum cascade laser based spectrometer.

A 7-bit, 1.4 GS/s ADC With Offset Drift Suppression Techniques for One-Time Calibration

This paper describes a digitally calibrated 7-bit, 1.4 GS/s flash analog-to-digital converter (ADC) implemented in 45-nm CMOS. The proposed offset drift suppression techniques for dynamic comparator and preamplifier make the ADC robust against environmental variation. As a result, once the ADC is calibrated at power up, no more calibration is necessary, even under VDD or temperature variations. The robustness is theoretically and experimentally verified. A calibration algorithm for doubling the ADC accuracy is also presented. The ADC occupies a small area of 0.085 mm2 and dissipates 33.24 mW at 1.4 GS/s from a 1.15 V supply.

Pesticide impacts on predator–prey interactions across two levels of organisation

In this study, we aimed to evaluate the effects of a short pulse exposure of the pyrethroid lambda-cyhalothrin (LC) on the predator and anti-predator behaviour of the same species; Gammarus pulex. Predator behaviour, at the level of the individual, was studied in indoor microcosms using video tracking equipment during simultaneous exposure of the predator (G. pulex) and its prey (Leuctra nigra) during 90min exposure of 1, 6.6 or 62.1ngL−1 LC. During an initial 30min of exposure, the predator and prey organisms were maintained physically separated, and the actual interaction was studied through the subsequent 60min of exposure. The anti-predator behaviour of G. pulex (drift suppression in response to the presence of brown trout) was studied in outdoor stream channels during a 90min pulse exposure to LC (7.4 or 79.5ngL−1) with, or without, brown trout. Based on survival curves for L. nigra we found that the mortality rate for L. nigra significantly decreased during exposure to 6.6 and 62.1ngL−1 LC (P<0.05 and P<0.001, respectively). We found no significant effects suggesting that G. pulex was repelled by contaminated prey items (P>0.05). We found that the exposure of G. pulex to 7.4 and 79.5ngL−1 LC significantly increased drift (from ∼0% to ∼100% in both treatments; P<0.001) independent of the presence of brown trout (P<0.05). In other words, the natural anti-predator behaviour of G. pulex was overruled by the stress response to LC exposure increasing G. pulex predation risk from drift feeding brown trouts. Our results show that the anti-predator and predator behaviour of G. pulex were significantly changed during exposure to very low and environmentally realistic LC concentrations and exposure duration. The potential implications for the field scenario are discussed.

Tunable Distributed Amplification (TDA-) DFB Laser with Asymmetric Structure

The wavelengths of tunable distributed amplification (TDA) distributed feedback (DFB) lasers consisting of multiple units including an active region and a tuning region can be changed without mode hopping. To expand the tuning range of TDA-DFB lasers, an asymmetric periodic structure is proposed where the units in the cavity have different lengths. It is shown theoretically that the asymmetric periodic structure is effective for expanding the mode-hop-free tuning range. In addition, a tunable laser array was fabricated consisting of six TDA-DFB lasers with an asymmetric periodic structure. A total wavelength tuning range of 44 nm was successfully obtained by expanding the tuning range of each laser, which corresponded to 110 channels with a 50-GHz grid. Moreover, the channel switching speed was investigated in relation to thermal drift. A switching time of less than 40 μs with a frequency deviation of less than 1 GHz was achieved with a thermal drift suppression technique that used the tuning regions of non-lasing lasers as heaters for temperature compensation.

Zwitterionic hydrogels crosslinked with novel zwitterionic crosslinkers: Synthesis and characterization

Two novel zwitterionic sulfobetaine dimethacrylate crosslinkersN,N-bis(methacryloxyethyl)-N-methyl-N-(3-sulfopropyl)ammonium (CL1) and N,N-bis(methacryloxyethyl)-N-methyl-N-(4-sulfobutyl)ammonium (CL2) betaines were synthesized and used for preparation of zwitterionic hydrogels formed from N-(methacryloxyethyl)-N,N-dimethyl-N-(3-sulfopropyl)ammonium betaine (SBDMA) via redox-initiated free-radical polymerization. The commercially available crosslinkers N,N′-methylene bisacrylamide (BIS) and ethylene glycol dimethacrylate (EDMA) were also used. Equilibrium water content, sorption degree, diffusion coefficient of water, state of water, degree of crosslinking and mechanical properties were determined for hydrogels crosslinked using different crosslinking conditions. A minor difference in the spacer length between the charged moieties in CL1 and CL2 crosslinkers, respectively, was shown to influence the hydrogel properties. The CL1 and CL2 crosslinkers with chemical structure similar to SBDMA resulted in hydrogels with higher stiffness, mechanical strength and crosslink density compared to hydrogels crosslinked by BIS and EDMA. This difference was assigned to suppression of the compositional drift during the hydrogel formation when crosslinkers with chemical structure similar to monomer were used. PolySBDMA hydrogels exhibited a low adhesion of RAT-2 fibroblasts-like cells.

Suppression of the frequency drift of modulational instability sidebands by means of a fiber system associated with a photon reservoir

We analyze fiber systems where the linear losses act as a strong perturbation, causing a frequency drift of the modulational instability sidebands. We achieve the total suppression of this frequency drift by means of a technique based on the concept of a photon reservoir, which feeds in situ the process of modulational instability by continually supplying it the amount of photons absorbed by the fiber.

Development of NMOR magnetometer for spin-maser EDM experiment

We have been developing a high sensitivity atomic magnetometer for atomic EDM experiments using a lowfrequency nuclear spin maser. In the developed nuclear spin maser of 129Xe, suppression of drift and fluctuation in the magnetic field is one of the important issues. The magnetometer being developed for spin maser EDM experiments utilizes the nonlinear magneto optical rotation (NMOR) e_ect in Rb atomic vapor. The enhancement of the optical rotation in a small magnetic field relies on the long spin-coherence time of Rb atoms in a vapor cell. The NMOR spectrum was measured by using fabricated Rb cells coated with an anti-relaxation material. The NMOR spectrum dependence on laser frequency, cell coating, and laser beam diameter were investigated. The magnetic sensitivity at present is 0:2μG/√Hz from observed NMOR and noise spectra.

Design criteria of the bolometer diagnostic for steady-state operation of the W7-X stellarator

A bolometric diagnostic system with features necessary for steady-state operation in the superconducting stellarator W7-X was designed. During a pulse length of 1800 s with an ECRH (electron cyclotron resonance heating) power of 10 MW, the components suffer not only from a large thermal load but also from stray radiation of the nonabsorbed isotropic microwaves. This paper gives an overview of the technical problems encountered during the design work and the solutions to individual problems to meet the special requirements in W7-X, e.g., component thermal protection, detector offset thermal drift suppression, as well as a microwave shielding technique.

Comparison of electrostatic and electromagnetic synchronization of drift waves and suppression of drift wave turbulence in a linear device

Experiments in a cylindrical magnetized plasma on the control of drift waves by means of two different spatiotemporal open-loop control systems—an electrostatic and an electromagnetic exciter—are reported. The drift wave dynamics is controlled by a mode-selective signal created with azimuthal arrangements of eight electrodes and eight saddle coils, respectively. Nonlinear interaction between the control signals and drift waves is observed, leading to synchronization of coherent drift waves and suppression of broadband drift wave turbulence. The cross-phase between density and potential fluctuations reduces from ≈π/2 in turbulence to ≈0 in controlled turbulence. Hence, the cross-field transport is reduced to the level of coherent drift waves. For both control systems the coupling to the drift wave can be ascribed to the drive of parallel currents, on the one hand via direct electric contact and, on the other hand, via electromagnetic induction.

Prediction of the acoustic environment on the launch pad for the Ares I rocket, including the effects of drift and water suppression.

A model, PAD, has been developed for prediction of noise in the vicinity of launch vehicles, with specific application to the mobile launcher and tower for the Ares I launch vehicle. It follows the basic principles of a traditional NASA model [NASA Report No. SP‐8072 (1971)] but uses an updated rocket sound power source model developed by Sutherland [AIAA Paper No. 93‐4383 (1993)] together with updates for the distribution and directivity of sources along the rocket plume. The effect of the deflector on plume geometry and shielding by the launcher deck are included in the model. Overall and spectral (octave band or psd) levels are predicted at specific points or on a regular grid of lateral and vertical positions on and around the launcher. A basic version of PAD was used for nominal acoustic predictions for vertical lift with all exhaust flow going through the flame hole in the deck and no water suppression (AIAA Paper No. 2009‐3163). The model has since been extended to account for lateral drift of the ...

Population genetics ofDrosophila ananassae

Drosophila ananassae Doleschall is a cosmopolitan and domestic species. It occupies a unique status among Drosophila species due to certain peculiarities in its genetic behaviour and is of common occurrence in India. Quantitative genetics of sexual and non-sexual traits provided evidence for genetic control of these traits. D. ananassae exhibits high level of chromosomal polymorphism in its natural populations. Indian natural populations of D. ananassae show geographic differentiation of inversion polymorphism due to their adaptation to varying environments and natural selection operates to maintain three cosmopolitan inversions. Populations do not show divergence on temporal scale, an evidence for rigid polymorphism. D. ananassae populations show substantial degree of sub-structuring and exist as semi-isolated populations. Gene flow is low despite co-transportation with human goods. There is persistence of cosmopolitan inversions when populations are transferred to laboratory conditions, which suggests that heterotic buffering is associated with these inversions in D. ananassae. Populations collected from similar environmental conditions that initially show high degree of genetic similarity have diverged to different degrees in laboratory environment. This randomness could be due to genetic drift. Interracial hybridization does not lead to breakdown of heterosis associated with cosmopolitan inversions, which shows that there is lack of genetic co-adaptation in D. ananassae. Linkage disequilibrium between independent inversions in laboratory populations has often been observed, which is likely to be due to suppression of crossing-over and random genetic drift. No evidence for chromosomal interactions has been found in natural and laboratory populations of D. ananassae. This strengthens the previous suggestion that there is lack of genetic co-adaptation in D. ananassae.

Relativistic ionization rescattering with tailored laser pulses

The interaction of relativistically strong tailored laser pulses with an atomic system is considered. Due to a special tailoring of the laser pulse, the suppression of the relativistic drift of the ionized electron and a dramatic enhancement of the rescattering probability is shown to be achievable. The high harmonic generation rate in the relativistic regime is calculated and shown to be increased by several orders of magnitude compared to the case of conventional laser pulses. The energies of the revisiting electron at the atomic core can approach the MeV domain, thus rendering hard x-ray harmonics and nuclear reactions with single atoms feasible.

Suppression of hydrogen-ion drift into underlying layers using plasma deposited silicon oxynitride film during high-density plasma chemical vapor deposition

Hydrogen ions drifting into underlying layers during HDP-CVD were successfully suppressed by the insertion of plasma deposited silicon oxynitride ( p-SiO x N y H z ) film, and the hydrogen-trapping mechanism was clarified. The hydrogen ions are trapped in bonding states, not in interstitial ones. After HDP-CVD undoped silicate glass (HDP-USG) film deposition on the p-SiO x N y H z film, the decrease of the dangling bonds in the p-SiO x N y H z film measured by ESR was much lower than the increase of the desorbed hydrogen concentration measured by TDS. These results suggest that new hydrogen-trapping sites are mainly generated from ESR-inactive bonds by drifted hydrogen ions and atomic hydrogen during HDP-CVD.

Smooth Pursuit in Patients with Downbeat Nystagmus

Smooth pursuit and gaze holding in light and darkness was investigated in 19 patients with downbeat nystagmus (DBN) and 17 control subjects. Vertical downward smooth pursuit was selectively impaired in patients, and gaze holding with a visible target was only slightly better than in darkness. The selective impairment of downward pursuit and the poor visual suppression of ocular drift in DBN support the involvement of the floccular lobe, which participates in gaze holding and contains gaze-velocity Purkinje cells with a downward on-direction for smooth pursuit.

Optimization of bi-directional digital filtering for drift suppression in electrocardiogram signals

Baseline drift may often impede automatic ECG measurement and interpretation. Known methods for drift suppression do not take into consideration specific waveform parameters of various ECG signals. We propose high-pass filtering with adaptable cut-off frequency in order to keep RS amplitude changes below a selectable threshold and to preserve ST segment shape within acceptable limits.

Anomalous transport in disordered dynamical systems

We consider simple extended dynamical systems with quenched disorder. It is shown that these systems exhibit anomalous transport properties such as the total suppression of chaotic diffusion and anomalous drift. The relation to random walks in random environments, in particular to the Sinai model, explains also the occurrence of ageing in such dynamical systems. Anomalous transport is explained by spectral properties of corresponding propagators and by escape rates in these systems. For special cases we provide a connection to quantum mechanical tight-binding models and Anderson localization. New classes of anomalous transport behavior with clear deviations from the behavior of Sinai type are found for generalizations of these models.

The behaviour of magnetic ripple wells along field lines in current heliotrons and stellarators: comparison with a classical heliotron

For the stellarator-type devices of today, which are very different from the quasi-symmetric ones, the analytical conditions for the existence of two kinds of ripple wells along field lines are derived taking into account the multiple helicity and multiple toroidicity of the magnetic field. It is shown that a typical feature of the above-mentioned devices, in contrast to a classical heliotron, is a considerable deformation of magnetic wells, both ordinary and secondary, by additional ripple fields. When this deformation exceeds a critical level, one kind of magnetic ripple well can be suppressed in some toroidal region. This happens if the amplitudes of the helical and toroidal magnetic fields and the amplitudes of the ripple fields are correlated with each other through the relations known as conditions for parametric resonance. When the parametric resonance conditions are fulfilled, charged particle confinement is improved because of a suppression of the toroidal drift.