Drift Measurements Research Articles

Comparison of Digisonde derived ion drifts and SuperDARN line-of-sight velocities over Zhongshan Station, Antarctica

In this study, ion drift velocities measured by Digisonde instruments over Zhongshan Station (ZHS, geog. 69.38°S, 76.38°E), Antarctica, are compared with measurements from Super Dual Auroral Radar Network (SuperDARN) HF radars. For SuperDARN Syowa East (SYE) and Kerguelen (KER) radars that intersect with ZHS, a data set comprised of adjacent range gates from nearest radar beams is used. Digisonde ion drift measurements were projected onto the direction of co-located and concurrent line-of-sight SuperDARN velocities. A comparison of the velocities shows a clear correlation (R = 0.92) between the two data sets. Projected Digisonde velocity was found to be, on average, larger than the line-of-sight SuperDARN radar velocities by a factor of 1.7. Time dependence distributions of Digisonde-SuperDARN SYE radars showed that the larger velocity discrepancies are more located at the dawnside convection cell. Considering the known features of the high-latitude convection patterns at cusp latitude, the statistical results imply the velocity discrepancies are related to the differences in the temporal and spatial evolution of plasma structures.

Procedural Drift: An Underappreciated Element of Clinical Treatment Fidelity.

Procedural fidelity involves delivering the correct guideline-supported treatment choice, in its designed manner, over the full care episode of the patient. Procedural drift is a subcomponent of procedural fidelity that involves performing the right treatment the right way initially, then drifting toward suboptimal treatment over time. Procedural drift occurs most often when providing intricate, patient-centered interventions that require attention to subtle nuances that potentially maximize their effectiveness. Drift comes from the belief that subtle nuances do not matter, or from a lack of motivation or incentive to maintain high fidelity. Strategies to reduce drift in practice include investment in early, high-quality training; using checklists and manuals when providing an intervention; using risk-adjusted patient data as a checks-and-balances system; and incorporating measures of drift in the practitioner's annual review. J Orthop Sports Phys Ther 2022;52(2):63-66. doi:10.2519/jospt.2022.10961.

Densified Pupil Spectrograph as High-precision Radial Velocimetry: From Direct Measurement of the Universe’s Expansion History to Characterization of Nearby Habitable Planet Candidates

Abstract The direct measurement of the universe’s expansion history and the search for terrestrial planets in habitable zones around solar-type stars require extremely high-precision radial-velocity measures over a decade. This study proposes an approach for enabling high-precision radial-velocity measurements from space. The concept presents a combination of a high-dispersion densified pupil spectrograph and a novel line-of-sight monitor for telescopes. The precision of the radial-velocity measurements is determined by combining the spectrophotometric accuracy and the quality of the absorption lines in the recorded spectrum. Therefore, a highly dispersive densified pupil spectrograph proposed to perform stable spectroscopy can be utilized for high-precision radial-velocity measures. A concept involving the telescope’s line-of-sight monitor is developed to minimize the change of the telescope’s line of sight over a decade. This monitor allows the precise measurement of long-term telescope drift without any significant impact on the Airy disk when the densified pupil spectra are recorded. We analytically derive the uncertainty of the radial-velocity measurements, which is caused by the residual offset of the lines of sight at two epochs. We find that the error could be reduced down to approximately 1 cm s−1, and the precision will be limited by another factor (e.g., wavelength calibration uncertainty). A combination of the high-precision spectrophotometry and the high spectral resolving power could open a new path toward the characterization of nearby non-transiting habitable planet candidates orbiting late-type stars. We present two simple and compact highly dispersed densified pupil spectrograph designs for cosmology and exoplanet sciences.

New measurement method for in-field measurements of liquid phase drift from cooling towers

This contribution introduces a newly proposed thermal based method for measurements of drift for in-field applications on real cooling towers up to an eliminator efficiency of approximately 0.0001% of circulating water flow. This method should thus become the main alternative to the methods used nowadays. The main advantage of this newly proposed measurement procedure should be its easy preparation and implementation and quick analysis of measurement results. The article summarizes the development of an innovative probe, and why this new probe and the entire method is needed for the industry. The design of this new probe consists of two main directions of development pathways: the electronic part and the aerodynamic part. The first one lies in the development of a sensor (and the accompanying electronics) and sums up the theoretical principle of the method (the calculation of droplet sizes scatter based on statistics, and the calculation of power needed for the sensor). The aerodynamics part derives from the desired efficiency and accuracy of the measurement and is based on precedent modelling and calculations of flow, containing droplets of various sizes through various uniquely shaped channels. The contribution also demonstrates an experiment made thus far, showing quantity measured and the drift evaluation process.

Rocket active drift measurement technology based on lidar

Rocket active drift measurement technology based on lidar

Anionic or neutral? the charge of Ni8 cubes in metal-organic framework compounds.

The cubic SBU Ni8X6L6 (X = OH-/H2O, L = ligand) is of great interest due to its stability and potential applications when integrated in MOFs. Here, we investigate by detailed DRIFTS measurements and exchange reactions whether it is found to be neutral in MOFs, as previously assumed in the literature, or whether it can show anionic character, as observed in complexes.

An in situ DRIFTS study on nitrogen electrochemical reduction over an Fe/BaZr0.8Y0.2O3−δ-Ru catalyst at 220 °C in an electrolysis cell using a CsH2PO4/SiP2O7 electrolyte

In situ DRIFTS measurements of an Fe/BZY-Ru cathode catalyst in an electrolysis cell using a CsH2PO4/SiP2O7 electrolyte were carried out in a mixed N2–H2 gas flow under polarization. The formation of N2Hx species was confirmed under polarization, and an associative mechanism in the electrochemical NRR process was verified.

Mean square displacement for a discrete centroid model of cell motion.

The mean square displacement (MSD) is an important statistical measure on a stochastic process or a trajectory. In this paper we find an approximation to the mean square displacement for a model of cell motion. The model is a discrete-time jump process which approximates a force-based model for cell motion. In cell motion, the mean square displacement not only gives a measure of overall drift, but it is also an indicator of mode of transport. The key to finding the approximation is to find the mean square displacement for a subset of the state space and use it as an approximation for the entire state space. We give some intuition as to why this is an unexpectedly good approximation. A lower bound and upper bound for the mean square displacement are also given. We show that, although the upper bound is far from the computed mean square displacement, in rare cases the large displacements are approached.

Ce-Containing MgAl-Layered Double Hydroxide-Graphene Oxide Hybrid Materials as Multifunctional Catalysts for Organic Transformations.

The combination of layered double hydroxides (LDH) with graphene oxide (GO) enables the formation of nanohybrids with improved properties. This work focuses on the structural and catalytic properties of Ce-containing MgAl LDH-GO composites bearing different concentrations of GO in the range of 5–25 wt.%. The synthesis of the composites was performed by co-precipitating the LDH phase in the presence of GO, while their characterization was performed using XRF, XRD, DRIFT, Raman, SEM, nitrogen adsorption-desorption, and acidity-basicity measurements. The LDH-GO composites, showing redox, basic, and acid catalytic functions, were tested in two different types of organic transformations: (i) Knoevenagel condensation and (ii) one-pot cascade oxidation-Knoevenagel condensation. (i) The cinnamic acid was synthesized by the Knoevenagel condensation of benzaldehyde with diethylmalonate. The composites showed catalytic performances in strong contrast to neat LDH or GO, suggesting a synergistic interaction between the two components. During Knoevenagel condensation, the catalytic activity increased with the GO content in the hybrids up to 15 wt.% and decreased afterwards. (ii) 2-Benzoyl-3-phenylacrylonitrile was synthesized by the aerobic oxidation of benzyl alcohol followed by the Knoevenagel condensation with benzoyl acetonitrile using three different non-polar solvents, i.e., toluene, benzene, and mesitylene. The conversion of benzyl alcohol was higher for the hybrid materials compared to the individual components but decreased with the increase of the graphene oxide concentration.

Using explainable machine learning to characterise data drift and detect emergent health risks for emergency department admissions during COVID-19

A key task of emergency departments is to promptly identify patients who require hospital admission. Early identification ensures patient safety and aids organisational planning. Supervised machine learning algorithms can use data describing historical episodes to make ahead-of-time predictions of clinical outcomes. Despite this, clinical settings are dynamic environments and the underlying data distributions characterising episodes can change with time (data drift), and so can the relationship between episode characteristics and associated clinical outcomes (concept drift). Practically this means deployed algorithms must be monitored to ensure their safety. We demonstrate how explainable machine learning can be used to monitor data drift, using the COVID-19 pandemic as a severe example. We present a machine learning classifier trained using (pre-COVID-19) data, to identify patients at high risk of admission during an emergency department attendance. We then evaluate our model’s performance on attendances occurring pre-pandemic (AUROC of 0.856 with 95%CI [0.852, 0.859]) and during the COVID-19 pandemic (AUROC of 0.826 with 95%CI [0.814, 0.837]). We demonstrate two benefits of explainable machine learning (SHAP) for models deployed in healthcare settings: (1) By tracking the variation in a feature’s SHAP value relative to its global importance, a complimentary measure of data drift is found which highlights the need to retrain a predictive model. (2) By observing the relative changes in feature importance emergent health risks can be identified.

Conversations about the Future of Dicamba: The Science Behind Off-Target Movement.

Dicamba is an important herbicide for controlling post-emergent resistant weeds in soybean farming. Recently, the scientific community and general public have further examined off-target transport mechanisms (e.g., spray drift, volatilization, and tank contamination) and the visual responses of soybeans to ultralow dicamba concentrations. This paper synthesizes key chemical concepts and environmental processes associated with dicamba formulations, transport mechanisms, drift measurements, and plant responses. This paper proposes additional areas of research and actions to increase our understanding and communicate the science findings, which should provide farmers with more robust tools and practices for sustainable dicamba use.

Influence of the Addition of Blast Furnace Slag to Alkali-Activated Mixtures Based on Natural Zeolites

This study focuses on a comparison of alkali-activated materials based on natural zeolites without and with the addition of blast furnace slag and their subsequent modification by acid leaching. The addition of slag to alkali-activated mixtures is generally used to increase the strength. The subsequent modification of its chemical, textural and mechanical properties by acid leaching makes this material usable in other industries, especially in the chemical industry. This study aimed to examine the influence of the addition of blast furnace slag to alkali-activated mixtures based on natural zeolites and observe the effect of subsequent acid leaching on the chemical, textural and mechanical properties and CO2 adsorption capacity of these materials. The modification of alkali-activated materials was carried out by acid leaching using 0.1 M HCl and then using 3 M HCl. The properties of these materials were determined using N2 physisorption, Hg porosimetry, XRF, XRD, DRIFT, TGA and strength measurements. The results showed that the addition of blast furnace slag significantly increased the cutting-edge strength of the obtained materials and affected the textural properties, especially in leached samples. The presence of blast furnace slag generated a higher proportion of mesopores, which are attributed to the presence of the calcium silicate hydrate (C–S–H) phase and are easily removed by leaching, as shown by the XRF results. The obtained data showed an improvement in properties and extension of the potential applicability of these materials in the chemical industry, especially for catalytic and adsorption applications.

Observing electric field and neutral wind with EISCAT 3D

Abstract. Measurements of height-dependent electric field (E) and neutral wind (u) are important governing parameters of the Earth's upper atmosphere, which can be used to study, for example, how auroral currents close or how energy flows between the ionized and neutral constituents. The new EISCAT 3D (E3D) incoherent scatter radar will be able to measure a three-dimensional ion velocity vector (v) at each measurement point, which will allow less stringent prior assumptions about E and u to be made when estimating them from radar measurements. This study investigates the feasibility of estimating the three-dimensional electric field and neutral wind vectors along a magnetic field-aligned profile from E3D measurements, using the ion momentum equation and Maxwell's equations. The uncertainty of ion drift measurements is estimated for a time and height resolution of 5 s and 2 km. With the most favourable ionospheric conditions, the ion wind at E region peak can be measured with an accuracy of less than 1 m/s. In the worst case, during a geomagnetically quiet night, the uncertainty increases by a factor of around 10. The uncertainty of neutral wind and electric field estimates is found to be strongly dependent on the prior constraints imposed on them. In the lower E region, neutral wind estimates have a lower standard deviation than 10 m/s in the most favourable conditions. In such conditions, also the F region electric field can be estimated with uncertainty of about 1 mV/m. Simulated measurements of v are used to demonstrate the ability to resolve the field-aligned profile of E and u. However, they can only be determined well at the heights where they dominate the ion drift, that is above 125 km for E and below 115 km for u. At the other heights, the results are strongly dependent on the prior assumptions of smoothness.

Thermal Performance of a Capacitive Comb-Drive MEMS Accelerometer: Measurements vs. Simulation

In this work, we analysed the difference between the measurement and simulation results of thermal drift of a custom designed capacitive MEMS accelerometer. It was manufactured in X-FAB XMB10 technology together with a dedicated readout circuit in X-FAB XP018 technology. It turned out that the temperature sensitivity of the sensor’s output is nonlinear and particularly strong in the negative Celsius temperature range. It was found that the temperature drift is mainly caused by the MEMS sensor and the influence of the readout circuit is minimal. Moreover, the measurements showed that this temperature dependence is the same regardless of applied acceleration. Simulation of the accelerometer’s model allowed us to estimate the contribution of post-manufacturing mismatch on the thermal drift; for our sensor, the mismatch-induced drift accounted for about 6% of total thermal drift. It is argued that the remaining 94% of the drift could be a result of the presence of residual stress in the structure after fabrication.

Investigation of the Relationships Among Clinical Measures of Foot Posture in Individuals with and Without Pronated Foot.

Many indirect clinical techniques have been developed to assess foot posture; however, there is relatively little research investigating the relationships among these techniques. We investigated the relationships among the most commonly used clinical measures of foot posture-Foot Posture Index-6 (FPI-6), navicular drop (NDP), navicular drift (NDT), and static and dynamic arch indices (SAI and DAI)-in individuals with normal foot posture and those with pronated foot. Sixty-three individuals with FPI-6 scores of 0 to 12 were included. A digital caliper was used to measure NDP and NDT; SAI and DAI were measured by electronic pedobarography. Assessments were applied on the dominant foot. Pearson correlation coefficients were calculated to determine the relationships among measures. Participants were classified into two groups, pronated foot (n = 33) and normal foot posture (n = 30), based on FPI-6 scores, providing a multisegmental and multiplanar assessment. The independent-samples t test was used to compare groups regarding NDP, NDT, SAI, and DAI. We found a high correlation between NDP and FPI-6 (r = 0.754) and between NDP and NDT (r = 0.778) (all P < .001). A moderate correlation was found between NDT and FPI-6 (r = 0.599) and between DAI and SAI (r = 0.519) (all P < .001). A negligible correlation was found between NDP and DAI (r = 0.268; P = .033). Furthermore, NDP, NDT, and DAI values were higher in individuals with pronated foot compared with those with normal posture (P < .001 for NDP and NDT; P = .022 for DAI), whereas SAI values were not (P = .837). These results suggest that there are moderate-to-strong relationships among FPI-6, NDP, and NDT and between SAI and DAI. The NDP, NDT, and DAI are suitable for the classification of foot posture based on FPI-6 scores. This study can guide clinicians and researchers to associate the foot posture measures with each other.

Electrical Characterization and Study of Current Drift Phenomena and Hysteresis Mechanism in Junctionless Ion-Sensitive Field-Effect Transistor

A comprehensive study of the drain current drift mechanism and hysteresis phenomena in fabricated p-channel junctionless ion-sensitive field-effect transistor (JL-ISFET) has been investigated for the first time. The current drift measurements have been performed through transient analysis of drain current, under different pH and liquid-gate bias (Vlg). Further, time-dependent gate-capacitance (CG) has also been analyzed to see the effect of hydroxyl ions (OH−) in the sensing film (Al2O3). The hysteresis has also been investigated for different pH loop (7 → 3 → 7 → 11 → 7 and 7 → 11 → 7 → 3 → 7) and times (960s, 1500s, and 1920s). It has been observed that the drift of JL-ISFET occurs because of chemical modification of the sensing film, due to OH−. The proposed device exhibits a threshold voltage sensitivity of 58.2 mV/pH that is near the Nernstian limit. Further, the hysteresis width and maximum drain current drift are measured as \(\sim \) 1.3 mV and 2.4 μ A (\(\sim \) 75%), respectively.

The Influence of the Preparation Method on the Physico-Chemical Properties and Catalytic Activities of Ce-Modified LDH Structures Used as Catalysts in Condensation Reactions.

Mechanical activation and mechanochemical reactions are the subjects of mechanochemistry, a special branch of chemistry studied intensively since the 19th century. Herein, we comparably describe two synthesis methods used to obtain the following layered double hydroxide doped with cerium, Mg3Al0.75Ce0.25(OH)8(CO3)0.5·2H2O: the mechanochemical route and the co-precipitation method, respectively. The influence of the preparation method on the physico-chemical properties as determined by multiple techniques such as XRD, SEM, EDS, XPS, DRIFT, RAMAN, DR-UV-VIS, basicity, acidity, real/bulk densities, and BET measurements was also analyzed. The obtained samples, abbreviated HTCe-PP (prepared by co-precipitation) and HTCe-MC (prepared by mechanochemical method), and their corresponding mixed oxides, Ce-PP (resulting from HTCe-PP) and Ce-MC (resulting from HTCe-MC), were used as base catalysts in the self-condensation reaction of cyclohexanone and two Claisen–Schmidt condensations, which involve the reaction between an aromatic aldehyde and a ketone, at different molar ratios to synthesize compounds with significant biologic activity from the flavonoid family, namely chalcone (1,3-diphenyl-2-propen-1-one) and flavone (2-phenyl-4H-1benzoxiran-4-one). The mechanochemical route was shown to have indisputable advantages over the co-precipitation method for both the catalytic activity of the solids and the costs.

Methane-selective oxidation to methanol and ammonia selective catalytic reduction of NOx over monolithic Cu/SSZ-13 catalysts: Are hydrothermal stability and active sites same?

This study investigated and compared the reactivities of NH3-SCR and methane-to-methanol reactions over the monolithic Cu/SSZ-13 catalysts with different zeolite crystal sizes before and after hydrothermal aging. It was found that the methanol yield decreases with the increase in crystal size in methane-to-methanol, and a severe deactivation was detected after aging. However, the NH3-SCR performance presents a higher thermal stability and even an enhanced low-temperature reactivity after aging. The fresh and aged catalysts were comprehensively characterized by XRD, SEM, N2 physisorption, NH3-TPD, H2-TPR, XPS, UV–vis-NIR and in-situ DRIFTS measurements. The results indicate that the isolated Cu2+ species, including those that interacted with two Al in 6MR and [CuII(OH)]+ motifs, and acid sites are main active centers for NH3-SCR. While CuxOy clusters, [CuII(OH)]+ motifs and Brønsted acid sites in the Cu-CHA frameworks could be important active sites for methane-to-methanol. Besides, the stable SCR performance is ascribed to the stable textural property, higher crystallinity of zeolite, increased NH3 storage capacity and isolated Cu2+ active sites. The loss of the catalytic activity in methane-to-methanol is mainly attributed to the decrease of Brønsted acid sites and CuxOy concentration and the break of zeolite crystal structure. This work concludes the differences in active sites and hydrothermal stability between NH3-SCR and methane-to-methanol reactions, it is very helpful to understand the two reactions.

Accurate measurement of wind drift and evaporation losses could improve water application efficiency of sprinkler irrigation systems − A comparison of measuring techniques

Wind drift and evaporation losses (WDEL) are some of the major sprinkler-irrigation losses which exist even in a well-managed irrigation system. Several research studies found a wide range of WDEL under different and nearly similar configurations of sprinkler irrigation systems under similar weather conditions but using different methodologies to measure the WDEL. The specific objective of this research was to evaluate the three most commonly used measuring techniques (standard catch-can tests (CC), an electrical conductivity method (EC), and a physical-based mathematical approach (PM)) for WDEL on a common sprinkler irrigation system under the same climatic conditions. We conducted 33 experiments from May to September of 2018 near Prosser, Washington. Twenty-two of these experiments were during the daylight hours, and 11 were during the night. We used catch-cans of 29.3 cm diameter and rain gauges (diameter of 10 cm) to collect water to measure the irrigation water's electrical conductivity. Mass and heat transfer approaches were used in the PM technique. The results showed that the three techniques yielded statistically different mean WDEL. The highest WDELs were in CC (22.8%), followed by EC (17.5%) and PM (6.8%) techniques. The CC WDELs were better correlated with PM than the EC approach. The mean nighttime WDEL for the EC and CC methods were not statistically different (p > 0.05). The CC WDELs were more closely related to wind speed than the vapor pressure deficit. The EC and PM approaches have a higher correlation to the vapor pressure deficit. The overall conclusion disclosed that the more we use indirect measurement methods, the more the chances of erroneous numbers. The EC and PM approaches are likely limited to measuring droplet evaporation as the latter includes several assumptions. The CC approach is a direct measurement of the WDEL.

Aqueous miscible organic solvent treated NiTi layered double hydroxide De-NOx photocatalysts

New efficient photocatalysts are required to remediate polluted urban atmospheres. We prepared a series of highly dispersed aqueous miscible organic (AMO) solvent treated NiTi layered double hydroxide (NixTi-AMO-LDHs (x = 2,3)) and studied their performance in the photocatalytic abatement of NOx gases. These photocatalysts can be prepared by a simple and scalable coprecipitation method at room temperature. NixTi-AMO-LDHs (x = 2,3) have been prepared with specific N2 BET surface areas and pore volumes up to to 492 m2g−1 and 1.37 cm3 g−1 respectively. Under sunlight simulation, the De-NOx performance of the conventional LDH and P25 (TiO2) benchmarks were surpassed by 40% and 17% respectively by the NixTi-AMO-LDHs. The NixTi-AMO-LDHs photocatalyst also exhibited outstanding reusability and unusually low release of the toxic NO2. The selectivity for the De-NOx process was investigated by in situ DRIFT measurements, the high surface area and pore volume was observed to play a significant role on the adsorption of the NO2 and N2O4 intermediates. The 2D character of the AMO-LDHs contributed to an enhancement in the production of radical species under illumination and reduction charge carrier recombination.