Maximum Drift Rate Research Articles

Influence of cationic vacancy diffusion on the aging behavior of low-temperature SrCo1-xRuxO3 thermosensitive ceramics

The thermosensitive ceramics of negative temperature coefficient (NTC), SrCo1-xRuxO3 (0 ≤ x ≤ 0.8), were synthesized using the solid-phase method. The research systematically explored the phase structure, microstructure, elemental chemical states, electrical properties, and aging performance. X-ray diffraction (XRD) data indicates that with the increase of Ru content, the lattice parameter increases. Scanning electron microscopy (SEM) images reveal a dense and uniform microstructure. X-ray photoelectron spectroscopy (XPS) data indicates the presence of Co2+/Co3+ and Ru4+/Ru5+ ion pairs. Resistive temperature data indicates its potential use as a low-temperature thermosensitive resistance material in the range of 2–300 K. Fitting the resistance-temperature curve using the thermally activated band conduction model and Mott's 3D variable range hopping model. Proposed the Ru–O2--Co hopping model, elucidating the hole hopping transport mechanism in NTC ceramics. Impedance spectroscopy analysis indicates that grain boundary resistance dominates the overall resistance of the sample. After aging at 77 K for 864 h, the maximum aging drift rate of the ceramic material is 1.55 %. Proposed a novel cationic vacancy diffusion model to explain aging phenomena, offering a new perspective for designing high-stability low-temperature NTC thermistors.

Developing a Drift Rate Distribution for Technosignature Searches of Exoplanets

A stable-frequency transmitter with relative radial acceleration to a receiver will show a change in received frequency over time, known as a “drift rate.” For a transmission from an exoplanet, we must account for multiple components of drift rate: the exoplanet’s orbit and rotation, the Earth’s orbit and rotation, and other contributions. Understanding the drift rate distribution produced by exoplanets relative to Earth, can (a) help us constrain the range of drift rates to check in a Search for Extraterrestrial Intelligence project to detect radio technosignatures, and (b) help us decide validity of signals-of-interest, as we can compare drifting signals with expected drift rates from the target star. In this paper, we modeled the drift rate distribution for ∼5300 confirmed exoplanets, using parameters from the NASA Exoplanet Archive (NEA). We find that confirmed exoplanets have drift rates such that 99% of them fall within the ±53 nHz range. This implies a distribution-informed maximum drift rate ∼4 times lower than previous work. To mitigate the observational biases inherent in the NEA, we also simulated an exoplanet population built to reduce these biases. The results suggest that, for a Kepler-like target star without known exoplanets, ±0.44 nHz would be sufficient to account for 99% of signals. This reduction in recommended maximum drift rate is partially due to inclination effects and bias toward short orbital periods in the NEA. These narrowed drift rate maxima will increase the efficiency of searches and save significant computational effort in future radio technosignature searches.

A Green Bank Telescope Search for Narrowband Technosignatures between 1.1 and 1.9 GHz During 12 Kepler Planetary Transits

Agrowing avenue for determining the prevalence of life beyond Earth is to search for “technosignatures” from extraterrestrial intelligences/agents. Technosignatures require significant energy to be visible across interstellar space and thus intentional signals might be concentrated in frequency, in time, or in space, to be found in mutually obvious places. Therefore, it could be advantageous to search for technosignatures in parts of parameter space that are mutually derivable to an observer on Earth and a distant transmitter. In this work, we used the L-band (1.1–1.9 GHz) receiver on the Robert C. Byrd Green Bank Telescope to perform the first technosignature search presynchronized with exoplanet transits, covering 12 Kepler systems. We used the Breakthrough Listen turboSETI pipeline to flag narrowband hits (∼3 Hz) using a maximum drift rate of ±614.4 Hz s−1 and a signal-to-noise threshold of 5—the pipeline returned ∼3.4 × 105 apparently-localized features. Visual inspection by a team of citizen scientists ruled out 99.6% of them. Further analysis found two signals of interest that warrant follow up, but no technosignatures. If the signals of interest are not redetected in future work, it will imply that the 12 targets in the search are not producing transit-aligned signals from 1.1 to 1.9 GHz with transmitter powers >60 times that of the former Arecibo radar. This search debuts a range of innovative technosignature techniques: citizen science vetting of potential signals of interest, a sensitivity-aware search out to extremely high drift rates, a more flexible method of analyzing on-off cadences, and an extremely low signal-to-noise threshold.

Dopamine and Risky Decision-Making in Gambling Disorder.

Gambling disorder is a behavioral addiction associated with impairments in value-based decision-making and cognitive control. These functions are thought to be regulated by dopamine within fronto-striatal circuits, but the role of altered dopamine neurotransmission in the etiology of gambling disorder remains controversial. Preliminary evidence suggests that increasing frontal dopamine tone might improve cognitive functioning in gambling disorder. We therefore examined whether increasing frontal dopamine tone via a single dose of the catechol-O-methyltransferase (COMT) inhibitor tolcapone would reduce risky choice in human gamblers (n = 14) in a randomized double-blind placebo-controlled crossover study. Data were analyzed using hierarchical Bayesian parameter estimation and a combined risky choice drift diffusion model (DDM). Model comparison revealed a nonlinear mapping from value differences to trial-wise drift rates, confirming recent findings. An increase in risk-taking under tolcapone versus placebo was about five times more likely, given the data, than a decrease [Bayes factor (BF) = 0.2]. Examination of drug effects on diffusion model parameters revealed that an increase in the value dependency of the drift rate under tolcapone was about thirteen times more likely than a decrease (BF = 0.073). In contrast, a reduction in the maximum drift rate under tolcapone was about seven times more likely than an increase (BF = 7.51). Results add to previous work on COMT inhibitors in behavioral addictions and to mounting evidence for the applicability of diffusion models in value-based decision-making. Future work should focus on individual genetic, clinical and cognitive factors that might account for heterogeneity in the effects of COMT inhibition.

Flexible four-point conjugate thin film thermocouples with high reliability and sensitivity.

Thin film thermocouples (TFTCs) are designed by finite element analysis and fabricated on the flexible substrate (polyimide) based on radio frequency magnetron sputtering technology, which can be used to measure the temperature of the curved surface. Various novel structures of TFTCs with several multi-junctions are designed to improve the stability and the reliability of measurement. The characteristics of its thermoelectric output are simulated by software. As the temperature range varies between 10 °C and 200 °C, the electromotive force behavior experiments show that the average Seebeck coefficient of the TFTCs can reach 25.8 µV/°C, the resolution of sensor is less than 0.1 °C, and the temperature drift is only 1.3%, 1.2%, 1.0% at 84 °C, 110 °C, and 142 °C, respectively. The maximum drift rate of TFTCs is 0.234 °C/min at 142 °C. The flexible TFTC temperature sensor shows great advantages in sensitivity, stability, reliability resolution, and measuring range.

Choosing a Maximum Drift Rate in a SETI Search: Astrophysical Considerations

Abstract A radio transmitter that is accelerating with a non-zero radial component with respect to a receiver will produce a signal that appears to change its frequency over time. This effect, commonly produced in astrophysical situations where orbital and rotational motions are ubiquitous, is called a drift rate. In radio SETI (Search for Extraterrestrial Intelligence) research, it is unknown a priori which frequency a signal is being sent at, or even if there will be any drift rate at all besides motions within the solar system. Therefore drift rates across the potential range need to be individually searched and a maximum drift rate needs to be chosen. The middle of this range is zero, indicating no acceleration, but the absolute value for the limits remains unconstrained. A balance must be struck between computational time and the possibility of excluding a signal from an ETI. In this work, we examine physical considerations that constrain a maximum drift rate and highlight the importance of this problem in any narrowband SETI search. We determine that a normalized drift rate of 200 nHz (e.g., 200 Hz s−1 at 1 GHz) is a generous, physically motivated guideline for the maximum drift rate that should be applied to future narrowband SETI projects if computational capabilities permit.

Development of a temperature controlled container for high accuracy capacitance manometers

National Institute of Metrology of Turkey (UME) has developed a new temperature-controlled container for high accuracy capacitance manometers (CDG). In the proposed design, due to the direct (metal-metal) contact of the temperature-controlled plate of the container with the aluminum shell of the sensor, the influence of the temperature of the electronics on the pressure sensor is minimized. Inside the aluminum shell, the temperature of the pressure sensor can be controlled at any fixed temperature with stability of ± 2 mK in the temperature range from 15 °C to 30 °C. The use of a pressure sensor inside an appropriate container minimizes the effect of the ambient temperature on the sensor, eliminates the need for correction for the effect of thermal transpiration and thus improves sensor accuracy. CDGs inside containers showed excellent short-term stability at zero pressure, which does not exceed ± 5 mPa as well as a maximum drift rate of 0.03 mPa h−1. The measurement results of ambient temperature influence on CDG’s zero showed a maximum change of 0.001% of full scale per degree Celsius. Control of CDG at ambient temperature significantly reduces the effects of thermal transpiration, which increases slightly to a maximum of 0.3% at the lowest pressures.

Synthesis of pilot-scale Co2Mn1.5Fe2.1Zn0.4O8 fabricated by hydrothermal method for NTC thermistor

Contrarily to previous synthesis work performed on a laboratory-scale, this paper investigates an automated hydrothermal process to prepare pilot-scale Co2Mn1.5Fe2.1Zn0.4O8 for NTC (negative temperature coefficient) thermistors. The influence of the hydrothermal temperature and time on the material properties was investigated in detail. The thermistors were fabricated with high-quality morphology samples and their electrical properties were measured. The resistance values at 25 °C and 50 °C were tested to obtain the B constant of the device. The electrical parameters measured for the 150°C-9h thermistor are: B25/50 = 3895 K and ρ25 = 10.314 kΩ cm. The maximum drift rate of the device is 0.26%, which is much lower than the one measured for previously reported thermistors. The investigated devices exhibit a uniform particle size and outstanding and stable performances. This work lays good foundations for future engineering applications of thermistors.

Temperature controlled transfer standard package for high accuracy pressure transducers with improved temperature stability

A new temperature controlled transfer standard package for absolute and differential pressure transducers has been developed at the Ulusal Metroloji Enstitusu (UME). Due to direct (metal-metal) touching of the temperature controlled plate of the temperature controlled unit with the pressure sensor housing the temperature influence of electronics on the pressure sensor is ruled out. The pressure sensor temperature inside of cast aluminum housing can be controlled at any fixed temperature in the temperature range of 15 °C − 30 °C with stability ± 2 mK. The mentioned transfer standard package minimizes the ambient temperature effects upon the sensor, denies the need to apply a correction for thermal transpiration effect and thereby increases accuracy of the transducer. The transfer standard packages have demonstrated excellent short-term zero stability which does not exceed ± 5 mPa and a maximum drift rate of 0.03 mPa h−1.

Accurate oxygen measurements on modified Argo floats using in situ air calibrations

AbstractOxygen is an important tracer for biological processes in the ocean. Measuring changes in oxygen over annual cycles provides information about photosynthesis and respiration and their impact on the carbon cycle. Long‐term, accurate oxygen measurements over wide areas are needed to determine changes in ocean oxygen content and oxygen deficient zones. Oxygen sensors have been increasingly mounted on Argo floats that profile between 2000 m and the surface. Most of these measurements are currently too inaccurate to calculate the air‐sea gas flux, which is the dominant flux of oxygen in the surface ocean and typically driven by surface oxygen supersaturation states of only several percent. In this study, we present data from 17 Aanderaa oxygen optodes mounted on 11 Argo floats modified to make atmospheric measurements for calibration. Optodes measure oxygen equally well in air and water, allowing the use of atmospheric oxygen to perform on‐going, in situ calibrations throughout the float lifetime. We find that it is necessary to make atmospheric measurements at night, that raising optodes higher into the air reduces variance in measurements, and that multiple measurements each time a float surfaces provide the best calibration data. Initial optode calibration on deployment has an average uncertainty of ± 0.1% (1 σ) and drift can be calculated to ± 0.1% yr−1. Measurable drift was determined in 10–12 optodes out of the 14 that were deployed for ∼ 2 yr. The maximum drift rate measured was −0.5% yr−1, which is large enough to strongly impact calculations of air‐sea oxygen fluxes.

Long-term wavelength drift compensation of tunable pulsed dye laser for sodium detection lidar

Wavelength stabilization for a pulsed laser presents more challenges than that of continuous wave laser. We have developed a simple and efficient long-term wavelength drifts compensation technique for tunable pulsed dye lasers (PDL) applied in sodium detection lidar system. Wavelength calibration and locking are implemented by using optogalvanic (OG) spectroscopy in a Na hollow cathode lamp (HCL) in conjunction with a digital control software. Optimization of OG signals for better laser wavelength discrimination and feedback control is performed. Test results indicate that locking the multimode broadband PDL to the Na atomic transition corresponding to 589.158nm is well achieved although the temperature in the laboratory is unstable. Through active compensation, the maximum wavelength drift is reduced from over 5pm to 0.42pm in 10h and the maximum wavelength drift rate of the PDL is improved from 3.3pm/h to 0.3pm/h. It has been used to efficient sodium resonance fluorescence lidar detection. This technique is economical and easy to implement, and it provides flexible wavelength control and allows generalization for some other applications which require the wavelength of tunable pulsed lasers to be fixed at an atomic resonance transition references.

Compass/BeiDou‐2 spaceborne clock performance assessment and its error detection, mitigation

The performance of a spaceborne atomic clock on a navigation satellite and the accuracy of the clock data in broadcast ephemeris are two critical factors for real‐time high‐accuracy global navigation satellite systems applications. A novel clock performance assessment method is proposed, which is indexed by the maximum clock error, clock rate, and clock drift rate, and the performance of the BeiDou‐2 satellite‐borne clock is assessed by this method compared to the GPS. To mitigate the negative effects of clock errors on pseudo‐range measurements and positioning results, an integrated clock prediction method is also presented in this paper based on polynomial modeling, wavelet denoising, and autoregressive integrated moving average modeling. An example is shown to test and verify the effectiveness of the integrated clock prediction method. Real data clock assessment results demonstrate the equivalent quality of BeiDou‐2 and GPS spaceborne clocks. The proposed clock prediction method can be used to detect and mitigate clock errors in broadcast ephemeris. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A long-term frequency stabilized deep ultraviolet laser for Mg+ ions trapping experiments

As many precision laser spectroscopy experiments require frequency stabilized lasers, development of long-term stabilized lasers is of great interest. In this work, we report long-term frequency stabilization of a 280 nm deep ultraviolet laser to a high precision wavemeter with digital servo control such that the long-term drift of the laser frequency was greatly reduced. Long-term laser frequency drift was measured with a fiber frequency comb system over 8 h. After locking, the maximum drift rate of the 280 nm laser was lowered from 576 MHz/h to 6.4 MHz/h. With proper environment control of the wavemeter, the maximum drift rate of the 280 nm laser was further lowered to less than 480 kHz/h. The locked laser system was successfully used in a Mg(+) ions trapping experiment, which was also discussed in this work.

EFFECTS OF SPATIAL VARIATIONS IN CORONAL ELECTRON AND ION TEMPERATURES ON TYPE III BURSTS. II. VARIATIONS IN ION TEMPERATURE

Quasilinear-based simulations are presented for the effects on coronal type III bursts of spatially varying ion temperature Ti in the corona. The simulations use a newly developed method for integrating spatial variations of coronal temperatures into our previous simulations for constant temperatures. The effects are simulated for monotonic Ti variations and/or for spatially localized enhancements in Ti . Generally, a localized enhancement in Ti has stronger effects on type III bursts than a corresponding monotonic variation in Ti . A localized Ti enhancement causes modulations to the dynamic spectra of fp and 2fp emission at frequencies corresponding to the disturbance: a narrowband slowly drifting intensification for both fp and 2fp emission and a narrowband suppression for 2fp emission. The fp emission may become observable due to the disturbance, although still much weaker than the 2fp emission. Signatures of the Ti enhancement are found in the 2fp spectral characteristics, e.g., the maximum flux and frequency drift rate. Importantly, these signatures are distinct from those of localized disturbances in electron temperature Te . The results indicate that coronal type III bursts provide a new tool to probe and distinguish localized disturbances in Ti or Te in the corona. Additionally, the presence of multiple spatially confined Ti enhancements at different heights may produce some observed fine structures in type III bursts; e.g., stria bursts and associated flux modulations in type IIIb bursts, and flux modulations in type IIIs whose beams traverse coronal shocks.

Differential rotation of geomagnetic field

The latitudinal dependence of the westward drift in the main geomagnetic field is examined by using the correlation analysis of moving random pattern. The study reveals the characteristics in the differential rotation of the main field. The results show that the global geomagnetic field drifts westward with an average speed of 0.18°/a during 1900 –2000. The westward drift rate is not symmetrical with respect to the equator. The maximum westward drift rate, 0.31°/a, occurs at the latitude φ=−15°, forming a Rapid Westward Drift Belt (RDB) around this latitude. Going northward and southward from this belt, the drift rate decreases and reaches the minimum (0.12°/a) at φ= 50° and the minimum (0.14°/a) at φ= −56°, forming a Northern Hemisphere Slow Westward Drift Belt (N-SDB) and a Southern Hemisphere Slow Westward Drift Belt (S-SDB). Three phases can be detected in the evolution of the westward drift. In the first phase (1900–1940), the RDB dominates the global drift pattern. The westward drifts in this belt are much faster than those in other areas. In the second phase (1940–1960), the drift rates in the RDB are less than those in the first phase, while the drifts in the N-SDB and S-SDB are relatively large. In this phase, the differential rotation becomes less obvious. In the third phase (1960–2000), the westward drift in the RDB increases again and the differential rotation gradually becomes apparent.

Polarization control in optical-fiber gyroscopes

Analysis indicates that strict attention must be paid to polarization control in fiber gyroscopes in order to ensure drift stability. It is shown that the maximum drift rate that is due to faulty polarization control is proportional to the amplitude-extinction ratio for the rejected polarization channel. Consequently, in the worst circumstances, which on present evidence cannot be excluded, the intensity extinction for the rejected polarization channel in a typical fiber gyroscope must approach 10(-6). Options for achieving this control are indicated by the analysis.

Further observations on drift in two brooks in Auvergne (France)

In two brooks, at about 1000 m altitude, drift rates were measured at hourly intervals during 48 hours.Hydracarina were day-active with a maximum drift rate coincidently starting with the increasing phase of the sinusoidal water temperature curve. Nymphs ofEphemeroptera andPlecoptera as well as gammarids were night-active with maximum numbers of animals caught that start and end shortly after the greatest changes in light intensity during resp. sunset and sunrise. Analysis of the activity during 48 hours of a drifting ephemeroptean and a non-drifting trochopteran did not reveal a periodical pattern. The results have been discussed. The relationship between periodically occurring increases in drift and activity, with attention to exogenous control and endogenous rhythms, deserves thorough experimental studies.