Drift Characteristics Research Articles

Simultaneous Temperature Compensation and Synchronous Error Elimination for Axial Displacement Sensors Using an Auxiliary Probe

The output stability of the displacement sensors is an important issue for safe operations in magnetic bearing supported high-speed rotor system. This paper proposes an effective postprocessing solution to the problems of temperature drift and synchronous measuring error for the axial displacement sensor in a 10-kW magnetically suspended motor. The proposed configuration of the axial displacement sensor consists of three probes: one pair is used to eliminate the synchronous measuring error, and the third probe is employed for the consideration of temperature drift. First, the generating mechanism of the synchronous measuring error caused by the improper assemble is presented, and an operational amplifier is proposed to obtain an accurate position of the axial center by adjusting the weights of sensing signals from one pair of probes. Then the scheme of temperature compensation using an auxiliary probe is presented. In order to obtain accurately the characteristics of temperature drift at the operating point, the detailed procedure is given to determine the temperature–drift ratio. Finally, the terms related to temperature drift and synchronous error in the final output of the displacement sensor are both eliminated. Experimental results on a magnetically suspended motor test rig show the effectiveness of the proposed solution.

Temperature characteristics of Pockels electro-optic voltage sensor with double crystal compensation

Voltage sensors based on the Pockels electro-optic effect in LiNbO3 crystals have been applied to practical engineering measurements because of their passive nature, wide operating bands, and low transmission loss. However, the temperature of the measurement environment can greatly affect the dynamic responses of these sensors because the natural birefringence of a single LiNbO3 crystal voltage sensor (SVS) is related to its temperature. To improve the stability of this sensor over a wide temperature range, a double crystal compensation method is introduced in this paper to compensate for the natural birefringence of the SVS. A double LiNbO3 crystal voltage sensor (DVS) was fabricated, and its working point drift characteristics and amplitude-frequency response were investigated over the temperature range from 0°C to 50°C. The effects of two intrinsic parameters of the LiNbO3 crystal were also investigated. Comparison between an existing SVS and the proposed DVS showed that the DVS resisted environmental temperature fluctuations more strongly.

Eye movements between saccades: Measuring ocular drift and tremor

Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye movements. While these movements are often disregarded as noise, the temporal modulations they introduce to retinal receptors are significant. However, analysis of these input modulations is challenging because the intersaccadic eye motion is close to the resolution limits of most eyetrackers, including widespread pupil-based video systems. Here, we analyzed in depth the limits of two high-precision eyetrackers, the Dual-Purkinje Image and the scleral search coil, and compared the intersaccadic eye movements of humans to those of a non-human primate. By means of a model eye we determined that the resolution of both techniques is sufficient to reliably measure intersaccadic ocular activity up to approximately 80Hz. Our results show that the characteristics of ocular drift are remarkably similar in the two species; a clear deviation from a scale-invariant spectrum occurs in the range between 50 and 100Hz, generally attributed to ocular tremor, leading to intersaccadic retinal speeds as high as 1.5deg/s. The amplitude of this deviation differs on the two axes of motion. In addition to our experimental observations, we suggest basic guidelines to evaluate the performance of eyetrackers and to optimize experimental conditions for the measurement of ocular drift and tremor.

Method of Control of Ion Drag Force in Complex Plasmas

AbstractThe research of dust structures dynamics in striations of the glow discharge in the magnetic field in the mixture of gases is presented. A variation of an ion flux velocity at an additive in light plasma forming gas of a small changeable portion of heavy and easily ionized components makes the control of ion drag force. It is shown that the small part of xenon (up to 5 percent) changes the static and dynamic properties of dust structure essentially. The increase of angular velocity of dust structure is revealed upon transition from pure helium to the mixture with small impurity of xenon. A reduction of vertical interpartical distance in dust structure in the mixture with xenon is detected. Results are agreed with data of calculation of characteristics of drift of ions in mixtures of gases. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of Mg insertion on stress‐induced resistance drift in MgO‐based magnetic tunnel junctions

The stress-induced resistance drift in MgO-based magnetic tunnel junctions (MTJs) with Mg insertion layer above and below a MgO tunnel barrier is investigated. Mg insertion suppresses the resistance drift. Resistance drift characteristics are improved when electrons tunnel into the Mg-inserted barrier–electrode interface, indicating that Mg insertion significantly suppresses trap site formation at the anode-side barrier–electrode interface. However, transmission electron microscopy images confirm that there is little difference in interface crystallinity between the Mg-inserted and non-inserted interfaces. Therefore, it is shown that a slight modification of the barrier–electrode interface states has a significant impact on resistance drift characteristics, and Mg insertion on both interface sides appears to be an effective way to improve MTJ device reliability in practical applications.

Electrolyte-Gated Graphene Ambipolar Frequency Multipliers for Biochemical Sensing.

In this Letter, the ambipolar properties of an electrolyte-gated graphene field-effect transistor (GFET) have been explored to fabricate frequency-doubling biochemical sensor devices. By biasing the ambipolar GFETs in a common-source configuration, an input sinusoidal voltage at frequency f applied to the electrolyte gate can be rectified to a sinusoidal wave at frequency 2f at the drain electrode. The extraordinary high carrier mobility of graphene and the strong electrolyte gate coupling provide the graphene ambipolar frequency doubler an unprecedented unity gain, as well as a detection limit of ∼4 pM for 11-mer single strand DNA molecules in 1 mM PBS buffer solution. Combined with an improved drift characteristics and an enhanced low-frequency 1/f noise performance by sampling at doubled frequency, this good detection limit suggests the graphene ambipolar frequency doubler a highly promising biochemical sensing platform.

EGFET pH Sensor Performance Dependence on Sputtered TiO2Sensing Membrane Deposition Temperature

Titanium dioxide (TiO2) thin films were sputtered by radio frequency (RF) magnetron sputtering method and have been employed as the sensing membrane of an extended gate field effect transistor (EGFET) for pH sensing detection application. The TiO2thin films were deposited onto indium tin oxide (ITO) coated glass substrates at room temperature and 200°C, respectively. The effect of deposition temperature on thin film properties and pH detection application was analyzed. The TiO2samples used as the sensing membrane for EGFET pH-sensor and the current-voltage (I-V), hysteresis, and drift characteristics were examined. The sensitivity of TiO2EGFET sensing membrane was obtained from the transfer characteristic (I-V) curves for different substrate heating temperatures. TiO2thin film sputtered at room temperature achieved higher sensitivity of 59.89 mV/pH compared to the one deposited at 200°C indicating lower sensitivity of 37.60 mV/pH. Moreover the hysteresis and the drift of TiO2thin film deposited at room temperature showed lower values compared to the one at 200°C. We have also tested the effect of operating temperature on the performance of the EGFET pH-sensing and found that the temperature effect was very minimal.

Introduction of parameterized sea ice drag coefficients into ice free-drift modeling

Many interesting characteristics of sea ice drift depend on the atmospheric drag coefficient (C a) and oceanic drag coefficient (C w). Parameterizations of drag coefficients rather than constant values provide us a way to look insight into the dependence of these characteristics on sea ice conditions. In the present study, the parameterized ice drag coefficients are included into a free-drift sea ice dynamic model, and the wind factor α and the deflection angle θ between sea ice drift and wind velocity as well as the ratio of C a to C w are studied to investigate their dependence on the impact factors such as local drag coefficients, floe and ridge geometry. The results reveal that in an idealized steady ocean, C a/C w increases obviously with the increasing ice concentration for small ice floes in the marginal ice zone, while it remains at a steady level (0.2–0.25) for large floes in the central ice zone. The wind factor α increases rapidly at first and approaches a steady level of 0.018 when A is greater than 20%. And the deflection angle θ drops rapidly from an initial value of approximate 80° and decreases slowly as A is greater than 20% without a steady level like α. The values of these parameters agree well with the previously reported observations in Arctic. The ridging intensity is an important parameter to determine the dominant contribution of the ratio of skin friction drag coefficient (Cs’/Cs) and the ratio of ridge form drag coefficient (C r’/C r) to the value of C a/C w, α, and θ, because of the dominance of ridge form drag for large ridging intensity and skin friction for small ridging intensity among the total drag forces. Parameterization of sea ice drag coefficients has the potential to be embedded into ice dynamic models to better account for the variability of sea ice in the transient Arctic Ocean.

Ion drift in parent gas for cesium, rubidium, and mercury

The results of Monte Carlo calculations of the ion drift characteristics in a constant and homogeneous electricfield are presented for the values of the applied intensity in the range 1 <E / N <1000 Td for cesium, rubidiumand mercury. The results of molecular dynamics simulation are used together with the Monte Carlo method forcalculation of collisional characteristics. The drift velocity, mean kinetic energy, longitudinal and transversediffusion coefficients, mean free path, and the fraction of collisions with backward scattering are calculated. Itis shown that the introduction of dimensionless units makes it possible to reduce the characteristics for differentgases to universal curves. And the Bhatnagar, Gross, and Krook collision integral for the problem of ion drift inan own gas leads to significant errors. Also, an unexpected and nontrivial fact about the collisions with backwardscattering is obtained and conclusions provided. It is found that using the BGK collision integral foedeseviling of ion drift an own gas leads to significant errors. There are some discussions regarding the largedifference between present calculations and data of the BGK theory.

Nighttime morphology of vertical plasma drifts at Ouagadougou during different seasons and phases of sunspot cycles 20–22

AbstractThe nighttime morphology of vertical plasma drift (Vd) inferred from ground‐based measurements of the F layer height at Ouagadougou (12.4°N, 358.6°E) in the African Equatorial Ionization Anomaly trough was investigated. The observation covers four seasons, four sunspot cycle phases, annual, and 11 year sunspot cycle (SC) variations of the SCs 20–22 spanning 1966–1998 and a first attempt of such study. The annual mean peak magnitudes of Vd during the prereversal enhancement (PRE) and minimum reversal periods exhibit the 11 year sunspot cycle evolution with the sunspot number (Rz). The PRE peak/Rz and reversal peak/Rz relationships are 98.7% and 84.8%, respectively. PRE peak in June solstice appears 1 h later than for other seasons and is attributed to a decrease in the equatorial zonal wind/conductivity gradient. The highest PRE magnitude and downward perturbation drifts near dusk appear during the equinoxes and lowest in June solstice for all cycles. There is semiannual asymmetry in the variation of Vd during all cycles of the PRE event with peaks in March and September/October. A remarkable feature is the consistent local presunrise drift enhancement for two SCs 20 and 21, which is not a regular feature of the equatorial ionosphere. The rate of inhibition of scintillation effect increases with decreasing phase of sunspot activity and maximizes during the solstices. Both the PRE and minimum reversal peak magnitudes are influenced by the phase of sunspot cycle. Ouagadougou data in this study had shown reliable drift characteristics and can be integrated into the African regional empirical drift model.

The oculomotor resonance effect in spatial–numerical mapping

We investigated automatic Spatial–Numerical Association of Response Codes (SNARC) effect in auditory number processing. Two experiments continually measured spatial characteristics of ocular drift at central fixation during and after auditory number presentation. Consistent with the notion of a spatially oriented mental number line, we found spontaneous magnitude-dependent gaze adjustments, both with and without a concurrent saccadic task. This fixation adjustment (1) had a small-number/left-lateralized bias and (2) it was biphasic as it emerged for a short time around the point of lexical access and it received later robust representation around following number onset. This pattern suggests a two-step mechanism of sensorimotor mapping between numbers and space — a first-pass bottom-up activation followed by a top-down and more robust horizontal SNARC. Our results inform theories of number processing as well as simulation-based approaches to cognition by identifying the characteristics of an oculomotor resonance phenomenon.

Realistic respiratory motion margins for external beam partial breast irradiation.

Respiratory margins for partial breast irradiation (PBI) have been largely based on geometric observations, which may overestimate the margin required for dosimetric coverage. In this study, dosimetric population-based respiratory margins and margin formulas for external beam partial breast irradiation are determined. Volunteer respiratory data and anterior-posterior (AP) dose profiles from clinical treatment plans of 28 3D conformal radiotherapy (3DCRT) PBI patient plans were used to determine population-based respiratory margins. The peak-to-peak amplitudes (A) of realistic respiratory motion data from healthy volunteers were scaled from A = 1 to 10 mm to create respiratory motion probability density functions. Dose profiles were convolved with the respiratory probability density functions to produce blurred dose profiles accounting for respiratory motion. The required margins were found by measuring the distance between the simulated treatment and original dose profiles at the 95% isodose level. The symmetric dosimetric respiratory margins to cover 90%, 95%, and 100% of the simulated treatment population were 1.5, 2, and 4 mm, respectively. With patient set up at end exhale, the required margins were larger in the anterior direction than the posterior. For respiratory amplitudes less than 5 mm, the population-based margins can be expressed as a fraction of the extent of respiratory motion. The derived formulas in the anterior/posterior directions for 90%, 95%, and 100% simulated population coverage were 0.45A/0.25A, 0.50A/0.30A, and 0.70A/0.40A. The differences in formulas for different population coverage criteria demonstrate that respiratory trace shape and baseline drift characteristics affect individual respiratory margins even for the same average peak-to-peak amplitude. A methodology for determining population-based respiratory margins using real respiratory motion patterns and dose profiles in the AP direction was described. It was found that the currently used respiratory margin of 5 mm in partial breast irradiation may be overly conservative for many 3DCRT PBI patients. Amplitude alone was found to be insufficient to determine patient-specific margins: individual respiratory trace shape and baseline drift both contributed to the dosimetric target coverage. With respiratory coaching, individualized respiratory margins smaller than the full extent of motion could reduce planning target volumes while ensuring adequate coverage under respiratory motion.

Drift reduction in strapdown airborne gravimetry using a simple thermal correction

Previous work has shown, that strapdown airborne gravimeters can have a comparable or even superior performance in the higher frequency domain (resolution of few kilometres), compared to classical stable-platform air gravimeters using springs, such as the LaCoste and Romberg (LCR) S-gravimeter. However, the longer wavelengths (tens of kilometres and more) usually suffer from drifts of the accelerometers of the strapdown inertial measurement unit (IMU). In this paper, we analyse the drift characteristics of the QA2000 accelerometers, which are the most widely used navigation-grade IMU accelerometers. A large portion of these drifts is shown to come from thermal effects. A lab calibration procedure is used to derive a thermal correction, which is then applied to data from 18 out of 19 flights from an airborne gravity campaign carried out in Chile in October 2013. The IMU-derived gravity closure error can be reduced by 91 % on average, from 3.72 mGal/h to only 0.33 mGal/h (RMS), which is an excellent long-term performance for strapdown gravimetry. Also, the IMU results are compared to the LCR S-gravimeter, which is known to have an excellent long-term stability. Again, the thermal correction yields a significant reduction of errors, with IMU and LCR aerogravity results being consistent at the 2 mGal level.

Drift characteristics of mobile ions in SiNx films and solar cells

Low temperature (30–200°C) drift characteristics of mobile ions in PECVD SiNx films and solar cells were determined for the first time using a non-contact ion-drift spectrometry technique adopted from silicon integrated circuit (IC) metrology. The results demonstrate drift of Na+ ions in PECVD SiNx films that begin at temperatures as low as 50°C. This is a seemingly contrasting behavior as compared to SiNx films used in microelectronics where it provides excellent protection as a diffusion barrier. The present study was carried out on SiNx films and final solar cells intentionally contaminated with Na, K, and Cu. In non-contact ion-drift spectrometry an electric field across the dielectric is created by charge deposited on the dielectric surface with a corona discharge in air. Temperature stress is applied by ramping the temperature with time at a controlled rate. Ion drift decreases the dielectric voltage that is monitored with a vibrating Kelvin-probe. Voltage versus time, voltage versus temperature, and corresponding derivative characteristics are used to quantify drift velocity, ion concentration and drift activation energy. The latter produces characteristic ion peaks in the derivative spectra dV/dT versus temperature. The metrology version for mobile ion mapping is based on whole-wafer corona bias-temperature stress at selected temperatures corresponding to drift of different ions. The mapping is a powerful means for ion source identification, such as Na from cell encapsulation glass. It shall prove advantageous for further clarification of the role of Na in potential induced degradation (PID) effects i.e. the polarization effect and the potential induced shunting (PIS).

Fitness Trade-Offs Determine the Role of the Molecular Chaperonin GroEL in Buffering Mutations.

Molecular chaperones fold many proteins and their mutated versions in a cell and can sometimes buffer the phenotypic effect of mutations that affect protein folding. Unanswered questions about this buffering include the nature of its mechanism, its influence on the genetic variation of a population, the fitness trade-offs constraining this mechanism, and its role in expediting evolution. Answering these questions is fundamental to understand the contribution of buffering to increase genetic variation and ecological diversification. Here, we performed experimental evolution, genome resequencing, and computational analyses to determine the trade-offs and evolutionary trajectories of Escherichia coli expressing high levels of the essential chaperonin GroEL. GroEL is abundantly present in bacteria, particularly in bacteria with large loads of deleterious mutations, suggesting its role in mutational buffering. We show that groEL overexpression is costly to large populations evolving in the laboratory, leading to groE expression decline within 66 generations. In contrast, populations evolving under the strong genetic drift characteristic of endosymbiotic bacteria avoid extinction or can be rescued in the presence of abundant GroEL. Genomes resequenced from cells evolved under strong genetic drift exhibited significantly higher tolerance to deleterious mutations at high GroEL levels than at native levels, revealing that GroEL is buffering mutations in these cells. GroEL buffered mutations in a highly diverse set of proteins that interact with the environment, including substrate and ion membrane transporters, hinting at its role in ecological diversification. Our results reveal the fitness trade-offs of mutational buffering and how genetic variation is maintained in populations.

Effect of Annealing on Drift in Type S Thermocouples Below $$900\, ^{\circ }\hbox {C}$$ 900 ∘ C

Type R and Type S platinum/platinum–rhodium thermocouples are amongst the most widely used high-temperature thermocouples, both for process measurement and as reference thermocouples. To achieve the lowest practical uncertainties, below $$1\, ^{\circ }\hbox {C}$$ , the thermocouples must be in a well-defined thermoelectric state. There are two annealing procedures in common use that leave the thermocouples in different states, leading to a potential ambiguity and uncertainty. This paper reports on experiments with Type S thermocouples clearly exposing the different drift characteristics for the two different annealed states. Thermocouples used above $$800\, ^{\circ }\hbox {C}$$ show the least drift when annealed at $$1100\, ^{\circ }\hbox {C}$$ and then passively quenched to room temperature. If used at lower temperatures, they exhibit drift, at temperatures as low as $$170\, ^{\circ }\hbox {C}$$ , with the drift peaking at $$0.3\, ^{\circ }\hbox {C}$$ to $$0.4\, ^{\circ }\hbox {C}$$ around $$300\, ^{\circ }\hbox {C}$$ to $$600 \, ^{\circ }\hbox {C}$$ . Thermocouples used below $$800\, ^{\circ }\hbox {C}$$ are best annealed at $$1100\, ^{\circ }\hbox {C}$$ , and then again at $$450\, ^{\circ }\hbox {C}$$ . In this state, they exhibit practically zero drift for temperatures up to about $$600 \, ^{\circ }\hbox {C}$$ . Advice on calibration procedures to minimise the effects of drift is given.

Anion sensing and interfering behaviors of electrolyte–insulator–semiconductor sensors with nitrogen plasma-treated samarium oxide

In this article, we demonstrate a samarium oxide (Sm2O3) electrolyte–insulator–semiconductor (EIS) sensor with nitrogen plasma immersion ion implantation (PIII) treatment for anion sensing and interfering characterization. Chloride (Cl−), nitrite (NO2−), and nitrate (NO3−) ions were detected, and the sensitivity was about 49.75 mV/pCl, 53.8 mV/pNO2, and 56.19 mV/pNO3, respectively. Ion sensitivity was enhanced with the increase in ionic radius of the target ion. Titration was performed to analyze the interference of anions. To assess interferences from these ions (Cl−, NO2−, and NO3−), selectivity coefficients obtained by fixed interference method (FIM) measurements were presented. In result, the coefficients indicate that the interference can be ignored. Furthermore, characteristics of drift demonstrates that the sample exhibits long-term stability for significantly lower drift of chloride, nitrite, and nitrate ions, respectively. The Sm2O3 EIS sensor with nitrogen PIII treatment exhibits superior anion sensitivity, selectivity, and stability; therefore, this sensor is suitable for future biosensing applications.

艾里涡旋光束在大气湍流中的漂移特性研究

艾里涡旋光束在大气湍流中的漂移特性研究

Analysis of System Key Variables under Power Fluctuation from Wind Power Cluster

The influence of power fluctuation from wind power clusters on power system is more and more significant. In order to describe this influence, a key variable set which can perfectly reflect dynamic characteristics of power system under wind power fluctuation is determined based on a pratical power system. Then, drift characteristics of the key variables under typical power fluctuation of wind power cluster are analyzed. The comparison of the drift characteristics between the key variables and the non-key variables verifies the feasibility and validity of the method.

Modeling and optimizing of the random atomic spin gyroscope drift based on the atomic spin gyroscope.

In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.