Drift Analysis Research Articles

Unravelling the effect of Ti3+/Ti4+ active sites dynamic on reaction pathways in direct gas-solid-phase CO2 photoreduction

Converting CO2 to CH4 by solar-powered catalysis involves complex steps that produce a range of by-products. Therefore, designing efficient heterostructures for a particular chemical synthesis is challenging. The optimisation of photocatalyst surfaces can achieve the desired CO2 photoreduction pathway. Herein, we developed TiO2/CdSe nanocrystals with both amorphous and crystalline TiO2 surfaces. In situ EXAFS analysis revealed that the amorphous surface contains abundant active Ti3+ sites, while the crystalline surface is limited. Moreover, the amorphous surface of TiO2/CdSe exhibits self-regenerating Ti3+ active sites, which enable a novel CH4 cycle. Density functional theory calculation showed that an amorphous structure enhances electron transfer and localisation to Ti3+, favouring CO2 adsorption. In situ DRIFTS analysis showed different CO2 to CH4 pathways on both surfaces. These results show the potential for enhanced photocatalytic CO2 reduction through surface engineering, which has far-reaching implications for sustainable energy conversion.

Intra-scan RF power amplifier drift correction.

The drift in radiofrequency (RF) power amplifiers (RFPAs) is assessed and several contributing factors are investigated. Two approaches for prospective correction of drift are proposed and their effectiveness is evaluated. RFPA drift assessment encompasses both intra-pulse and inter-pulse drift analyses. Scan protocols with varying flip angle (FA), RF length, and pulse repetition time (TR) are used to gauge the influence of these parameters on drift. Directional couplers (DICOs) monitor the forward waveforms of the RFPA outputs. DICOs data is stored for evaluation, allowing calculation of correction factors to adjust RFPAs' transmit voltage. Two correction methods, predictive and run-time, are employed: predictive correction necessitates a calibration scan, while run-time correction calculates factors during the ongoing scan. RFPA drift is indeed influenced by the RF duty-cycle, and in the cases examined with a maximum duty-cycle of 66%, the potential drift is approximately 41% or 15%, depending on the specific RFPA revision. Notably, in low transmit voltage scenarios, FA has minimal impact on RFPA drift. The application of predictive and run-time drift correction techniques effectively reduces the average drift from 10.0% to less than 1%, resulting in enhanced MR signal stability. Utilizing DICO recordings and implementing a feedback mechanism enable the prospective correction of RFPA drift. Having a calibration scan, predictive correction can be utilized with fewer complexity; for enhanced performance, a run-time approach can be employed.

Effect of loading method on catalytic performance of Pt/CeO2 system for CO oxidation

The oxygen vacancies of CeO2 play a pivotal role in effectively dispersing and stabilizing noble metal nanoparticles (NPs). During the NPs loading process, the post-treatment condition, e.g. atmosphere, has a certain influence on the oxygen vacancy concentration of CeO2, highlighting the importance of suitable choice of loading technique. Herein, A-Pt/HCeO2 and I-Pt/HCeO2 catalysts are prepared by loading Pt NPs on HCeO2 with abundant oxygen vacancies (obtained from the calcination of a Ce(OH)CO3 precursor under H2) using ALD deposition and impregnation methods, respectively. Through detailed characterization and in situ DRIFTS analysis, it was noted that compared to the I-Pt/HCeO2 catalyst, the A-Pt/HCeO2 catalyst processes a uniform distribution of Pt NPs, more Pt0 active sites and oxygen vacancies, thus exhibiting an outstanding catalytic performance for CO oxidation. The ALD deposition technique mitigates the effects of high-temperature sintering and atmospheric exposure during the loading process of noble metal NPs, offering a more accurate assessment of the catalytic performance of catalysts.

Unraveling the multi-pollutant removal using M-MoWTi (M = Fe, Mn, Cr) catalyst: experiment and mechanistic study of competition for active sites.

Multi-pollutant removal (MPR) of NO and VOCs simultaneously is efficient of flue gas treatment in coal-fired power plants. But reducing the competition for active sites between NH3, NO, C6H6, and C7H8 remains challenging. Herein, Cr, Mn, and Fe were respectively doped to MoWTi catalyst via wet impregnation. The Fe3+ + Mo5+ ↔ Fe2+ + Mo6+ redox cycle led to an increased proportion of low valence ions (Mo5+ and W5+) and facilitated the creation of active oxygen vacancies with several active sites. It also possessed plentiful mild to strong acid sites with ideal ratio. These factors enhanced catalytic activity of Fe-MoWTi. Remarkable MPR efficiencies of NO, C6H6, and C7H8 were achieved under industrial SCR condition, characterized by low oxygen but high SO2 levels at 340 °C, with removal rates reaching 89.85%, 97.57%, and 86.30% respectively. Theory calculations further revealed that Fe-MoWTi favor NH3 and O2 adsorptions. NO elimination was found to follow both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) processes, supported by in situ DRIFTS analysis. The reactions involving NO/NO2/nitrite/nitrate occurred with NH3(ads)/ NH4+(ads)/NH2 (ads). C6H6 and C7H8 underwent gradual oxidation, formatting alcohols, aldehydes, acids, and maleic acids, before eventually being mineralized to gaseous CO2 and H2O. Findings hold significant potential for application, providing guidance for the development of catalysts with improved resistance against SO2 poisoning and enhanced MPR capabilities.

Enhanced and Sustainable Removal of Indoor Formaldehyde by Naturally Porous Bamboo Activated Carbon Supported with MnOx: Synergistic Effect of Adsorption and Oxidation

Novel bamboo activated carbon (BAC) catalysts decorated with manganese oxides (MnOx) were prepared with varying MnOx contents through a facile one-step redox reaction. Due to the physical anchoring effect of the natural macropore structure for catalyst active components, homogeneous MnOx nanoparticles (NPs), and high specific surface area over catalyst surface, the BAC@MnOx-N (N = 1, 2, 3, 4, 5) catalyst shows encouraging adsorption and catalytic oxidation for indoor formaldehyde (HCHO) removal at room temperature. Dynamic adsorption and catalytic activity experiments were conducted. The higher Smicro (733 m2/g) and Vmicro/Vt (82.6%) of the BAC@MnOx-4 catalyst could facilitate its excellent saturated and breakthrough adsorption capacity (5.24 ± 0.42 mg/g, 2.43 ± 0.22 mg/g). The best performer against 2 ppm HCHO is BAC@MnOx-4 catalyst, exhibiting a maximum HCHO removal efficiency of 97% for 17 h without any deactivation as RH = 0, which is higher than those of other MnOx-based catalysts. The average oxidation state and in situ DRIFTS analysis reveal that abundant oxygen vacancies on the BAC@MnOx-4 catalyst could be identified as surface-active sites of decomposing HCHO into the intermediate species (dioxymethylene and formate). This study provides a potential approach to deposit MnOx nanoparticles onto the BAC surface, and this hybrid BAC@MnOx material is promising for indoor HCHO removal at room temperature.

Investigation of intermediates formation in the CO2 hydrogenation to methanol reaction over Ni5Ga3-ZrO2-SBA-15 materials prepared via ZrO2 atomic layer deposition

The production of methanol through CO2 hydrogenation holds great promise for efficient CO2 utilization. The development of catalysts that exclusively favor the formate route is desirable as this enhances methanol selectivity and avoids CO formation. Here, the synthesis of two groups of Ni5Ga3-ZrO2-SBA-15 based materials was studied through the atomic layer deposition (ALD) of ZrO2. The first group was prepared applying ZrO2 ALD over a Ni5Ga3/SBA-15 material and the second group was prepared doing ZrO2 ALD over a mesoporous silica, Santa Barbara Amorphous (SBA-15), followed by impregnation with Ni5Ga3. Some characterization techniques were employed to assess the effectiveness of the ZrO2 ALD on both groups. Interestingly, it was observed that ZrO2 deposition was less effective over the Ni5Ga3/SBA-15 sample compared to its deposition over pure SBA-15, and through XPS analysis was noticed that ZrO2 is probably covering part of the Ni5Ga3 alloys. Furthermore, in situ DRIFTS analysis was performed during reaction conditions and revealed that ZrO2 deposition facilitated the formation of formate and methoxy intermediates in both material groups. The increase in the ZrO2 ALD cycles increased the formate and methoxy bands and decreased CO-related bands. After 6 cycles, only the ZrSBANG_6 catalyst exclusively followed the formate route, as only formate and methoxy bands were present.

Atomic level transition of graphene layer to carbon nanotubes over cobalt during ethanol decomposition reaction

Herein we report the catalytic ethanol decomposition over cobalt catalyst synthesized using conventional solution combustion synthesis (SCS). The reaction pathway proposed in-situ DRIFT analysis shows that the decomposition reaction proceeds through the formation of surface ethoxy intermediates that transformed into acetates and aldehydes which further decompose to releases CH4, H2 and CO2 with some deposition of carbon on the catalyst surface. The catalytic reaction shows 100 % ethanol conversion at 420 °C, with high selectivity of H2 in the output. The structural transformation of the catalyst and deposited carbon was analyzed using high-resolution transmission electron microscope (HRTEM). Presence of small Co nanoparticles (size <30 nm) surrounded with graphene and larger metal nanoparticles trapped inside MWCNTs was visible during a stability run over 50 h that motivates in proposing the reaction mechanism of the fluctuating metal nanoparticle along with carbon on the catalyst surface. Moreover, this work opens up the possibility of synthesizing highly dispersed Co nanoparticles in an efficient way without any complex experimental procedures and equipment that can further be used as effective catalysts in many industrial reactions.

Reversal of drift direction during the Laschamp geomagnetic excursion

Earth's magnetic field changes in both space and time: the temporal changes are called geomagnetic and paleomagnetic secular variations. Westward drift has been noted as a feature of secular variation for several centuries, but eastward drift has received less attention. We use three global geomagnetic field models covering the past 100 kyr to extend temporal coverage for tracking the zonal (azimuthal) motion of the radial magnetic field. The models we use are GGF100k (100–0 ka), GGFSS70 (70–15 ka), LSMOD.2 (50–30 ka); the extent of the models enables the inclusion of the extreme secular variations found during excursions, particularly the Laschamp excursion (42–40 ka). GGFSS70 and LSMOD.2 have higher temporal resolution than GGF100k, but their underlying data have poorer spatial coverage. Spatial structure is greatly diminished in all models for spherical harmonic degrees l>4.We use two types of time-longitude plots, one of the full radial field to expose reverse and intense flux patches at the core-mantle boundary. The second time-longitude plot is processed to enhance zonal motion signatures and allows us to use Radon drift analyses to uncover characteristic time scales of both westward and eastward drift at mid to high latitudes in both the northern and southern hemispheres. Our results differ across the three models, which we attribute to varying degrees of resolution, accuracy, and data distribution. Nevertheless, recurrent episodes of both eastward and westward drift ranging from ±0.05o/yr to ±0.18o/yr occur in both the northern and southern hemispheres. Westward drift dominates. We also observe 8–20 kyr intervals between occurrences of high-latitude reverse flux patches correlated with strong drift signals. Focusing on the period 50–30 ka, we observe dominant eastward drift preceding the Laschamp excursion and westward drift subsequently. In a period not associated with an excursion, 90–80 ka, we see strong mid to high latitude drift signatures in the northern hemisphere.

Dry reforming of methane over Ni/Al2O3 catalysts: Support morphological effect on the coke resistance

Flower-like (Al2O3-F), wire-like (Al2O3-W) and sphere-like (Al2O3-S) alumina supported nickel catalysts (designated as Ni/Al2O3-F, Ni/Al2O3-W and Ni/Al2O3-S) were prepared for catalytic dry reforming of methane (DRM). The resultant catalysts exhibited variable catalytic activities and coke resistance performances in the reaction, which was closely dependent on their various physicochemical properties from the morphological effect of Al2O3 supports. To be precise, Ni/Al2O3-W presented adequately high catalytic activity and promising anti-coke behavior, which was attributed to its strong metal-support interaction, the surface dispersion of small-sized Ni nanoparticles and noticeable activation ability towards CO2. Ni/Al2O3-F possessed high anti-coke performance as well in terms of its significant CO2 activation ability. However, the encapsulation effect of Al2O3-F nanostructure resulted in insufficient abundance of metallic Ni active sites on the surface of Ni/Al2O3-F, thus giving rise to poor initial catalytic activity. The weak CO2 activation ability and the large particle size of metallic Ni on Ni/Al2O3-S induced the considerable formation of filamentous carbon after long-term DRM test. With regard to in situ DRIFTs analysis, the existence of OH* as the coke precursor scavenger and its reaction with the CHx* intermediate species from CH4 cracking were demonstrated to play crucial roles in dominating the overall anti-coke performances of Ni/Al2O3 catalysts. This work provides new insights into the development of high coke-resistance Ni-based catalysts from the perspective of support morphology modulation.

Open-source Python repository for data drift analysis

In this paper, we propose practical Python programs together with appropriate environments for the analysis of data stream drift, including the analysis of feature drift. The proposed approach contains a description of both, synthetic and real datasets. These datasets include different types of drifts like sudden, incremental, or gradual. Also, the location of the drift can be programmed. Additionally, we propose Java scripts that allow specifying the number and place of drift locations. The software is focused on prequential error methodology.Our proposition can be used by scientists interested in machine learning and concept drift detection because the proposed solution makes it easier to conduct practical experiments on that matter. The proposed solution allows for conducting experiments in a homogeneous programming environment. Versions of Python programs, stored in the GitHub repository, contain implementations of popular classifiers and drift detectors. The GitHub repository is located in the Public Domain.

Achieving 1-µg Weighing Resolution of Light Pressure by Drift Analysis and Compensation for Precision Sub-Kilowatt Laser Power Measurement

Achieving 1-<i>µ</i>g Weighing Resolution of Light Pressure by Drift Analysis and Compensation for Precision Sub-Kilowatt Laser Power Measurement

Kinetic Monte Carlo simulation analysis of the conductance drift in Multilevel HfO2-based RRAM devices.

The drift characteristics of valence change memory (VCM) devices have been analyzed through both experimental analysis and 3D kinetic Monte Carlo (kMC) simulations. By simulating six distinct low-resistance states (LRS) over a 24-hour period at room temperature, we aim to assess the device temporal stability and retention. Our results demonstrate the feasibility of multi-level operation and reveal insights into the conductive filament (CF) dynamics. The cumulative distribution functions (CDFs) of read-out currents measured at different time intervals provide a comprehensive view of the device performance for the different conductance levels. These findings not only enhance the understanding of VCM device switching behaviour but also allow the development of strategies for improving retention, thereby advancing the development of reliable nonvolatile resistive switching memory technologies.

Red mud-fly ash-based geopolymers as an eco-friendly material for immobilization of toxic pollutants (Pb and Cu) from wastewater

The use of waste materials as a precursor for synthesizing geopolymer materials is increasingly being utilized. This research aimed to examine the potential use of red mud-fly ash geopolymers to remove toxic pollutants such as copper and lead ions from wastewater. Samples of different ratios of red mud (RM) and fly ash (FA) were synthesized through alkaline activation. Based on compressive strength a geopolymer (RMFAGP1) with the highest value of 29.54 MPa, was chosen for further research. The physical-chemical characterization of RMFAGP1 in terms of mineral composition and structure was performed using XRD, DRIFT and SEM analysis. BET analysis was used to define porosity, as well as the specific surfaces necessary for efficient adsorption. The batch equilibration method was used to determine the PZC value, which serves as a guide for predicting the adsorption process. The best adsorption efficiency was achieved at pH =4 (88,5%) i.e. at pH=5 (99,4%) for Cu and Pb, respectively. The performed analyses indicate that waste materials, such as red mud and fly ash, can be used as raw materials for obtaining a geopolymer that can effectively immobilize Pb and Cu from wastewater, offering a low-cost and eco-friendly solution.

Mechanism of SO2/H2O enhanced rare earth tailings catalysts in NH3-SCR at medium and high temperature.

Rare earth tailings (RET) NH3-SCR catalysts were prepared by mechanical and microwave activation of a large amount of rare earth tailings after beneficiation of Bayan Ebo rare earth ore. The effects of SO2/H2O on the denitrification performance of the RET catalysts were evaluated by conducting denitrification activity tests, SO2/H2O tolerance tests and in situ DRIFTs mechanistic analysis. The results showed that the denitrification activity was significantly increased in the presence of SO2/H2O. And in situ DRIFTs analysis showed that in the presence of SO2/H2O, SO2 could be adsorbed as SO32- groups by the hydroxyl groups on the catalyst surface and react with SO42- to form S2O72- species. And in the presence of NH3, S2O72- would decompose into unstable SO42- species and SO32- and continue to react cyclically to form S2O72- species, providing the RET catalyst provides more acid sites, facilitating the SCR reaction.

Thermal-Induced Drift Analysis and Algorithm Compensation Technology of Fiber Optic Gyroscope

Thermal-Induced Drift Analysis and Algorithm Compensation Technology of Fiber Optic Gyroscope

Rare Earth Metal (La, Ce, Nd, Eu) Doped Cu/Zr-PILC Catalysts for the Efficient NH3-SCR at Low Temperature

ABSTRACT A series of RE-3Cu/Zr-PILC (RE = La, Ce, Nd, Eu) catalysts were prepared via an impregnation method and activities for NH3-SCR were evaluated. The physicochemical properties of each catalyst were explored using XRD, BET, H2-TPR, NH3-TPD, XPS and in-situ DRIFTS techniques. The doping of RE had enhanced the NH3-SCR efficiency of 3Cu/Zr-PILC. Among them, the 6Ce-3Cu/Zr-PILC sample demonstrated exceptional performance, achieving NO conversion rates exceeding 90% within the temperature range of 250–350°C. Moreover, it reached its peak NO conversion rate of 96.3% at 300°C while maintaining an impressive resistance to SO2. According to the results of TPR, TPD and XPS analysis, the modification of RE (especially Ce) enhanced the redox properties, the surface acidity, the atomic ratio of Cu2+/Cu+ and the amount of surface chemisorbed oxygen in the 3Cu/Zr-PILC samples, all of these are favorable for the NH3-SCR reaction. Furthermore, in-situ DRIFTS analysis reveals that the NH3-SCR reaction of RE-3Cu/Zr-PILC samples at low temperatures is governed by the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms, with the L-H mechanism being the predominant factor.

Estimating the long-term drift of travelling measurement standards for comparisons

In metrology, it is essential to analyse the instrumental drift of measuring instruments and measurement standards. Each reference instrument is periodically calibrated according to a frequency determined by the laboratory. Calibration establishes the metrological state of the instrument on a certain date of calibration. However, it is necessary to know the state of the measuring instrument during or after the calibration.&#x0D; Reliable accounting for drift plays an important role in maintaining measurement accuracy. Otherwise, it can lead to significant measurement errors. Accounting for time drift is mandatory when conducting international comparisons of national measurement standards. The drift uncertainty can be evaluated from its history of successive calibrations. In the absence of such a history, the magnitude order of the calibration uncertainty can be estimated.&#x0D; The analysis of the long-term drift of travelling measurement standards is limited to examples of key and supplementary comparisons of measurement standards of electrical capacitance. Quite a lot of such comparisons were conducted both by the Consultative Committee for Electricity and Magnetism (CCEM) and by most of the Regional Metrology Organizations (RMOs). There are international standards and guides that describe various statistical methods of analysing the measurement results.&#x0D; For capacitance measurement standards, time drift is predictable and nearly linear. For comparisons of measurement standards, a linear model is more than often applied, as a travelling measurement standard with excellent stability characteristics is used. The consistent results have been obtained. The linear model was applied to estimate the drift of travelling measurement standards during the key and supplementary comparisons (COOMET.EM-K4, COOMET.EM-S4, and COOMET.EM-S13) of measurement standards of electrical capacitance. The estimation of the long-term drift of measurement standards of electrical capacitance as travelling measurement standards for comparisons using a polynomial regression are presented.

Comparative removal of pharmaceuticals in aqueous phase by agricultural waste-based biochars.

The intensification of pharmaceutical use globally has led to an increase in the number of water bodies contaminated by drugs, and an effective strategy must be developed to address this issue. In this work, several biochars produced from Miscanthus straw pellets (MSP550, MSP700) and wheat straw pellets (WSP550, WSP700) at 550 and 700°C, respectively, were selected as adsorbents for removing various pharmaceuticals, such as pemetrexed (PEME), sulfaclozine (SCL), and terbutaline (TBL), from the aqueous phase. The biochar characterizations (physicochemical properties, textural properties, morphological structures, and zeta potentials) and adsorptive conditions (contact times, temperatures, and pH effect) were investigated. The infrared and Raman spectra of biochars before and after pharmaceutical adsorption, as well as quantum chemical computations, were carried out to explore the adsorption mechanisms. The results showed that the general adsorption abilities of biochars for pharmaceuticals were in the order of WSP700 > MSP700 > MSP550 > WSP550. Both the higher drug concentration and higher temperature improved biochar adsorption. By decreasing the pH, the adsorption amounts increased for PEME and SCL. However, TBL exhibited the best adsorption at pH7, whereas a weakening of affinity occurred at lower or higher pH values. Electrostatic interactions and hydrogen bonding were the main adsorptive mechanisms between all biochars and pharmaceuticals. π-π interactions played a role in the adsorption process of low-temperature-prepared biochars (MSP550 and WSP550). This work can provide new insights into the control of pharmaceuticals from water with low-cost adsorbents. PRACTITIONER POINTS: Use of biochars for pharmaceuticals removal from aqueous phase. Characterization of biochars : physical and chemical properties, textural and surface properties. Simulation calculation for characterization of pharmaceuticals. Kinetic studies of pharmaceuticals adsorption on biochars. DRIFTS and Raman analysis for the understanding of adsorption process.

Catalytic oxidation of propane over nanorod-like TiO2 supported Ru catalysts: Structure-activity dependence and mechanistic insights

Nanorod-like titanium dioxide (TiO2-Rod) supported ruthenium catalysts with variable metal loadings (designated as x-Ru/TiO2-Rod, x = 0.1, 0.5, 1.0 and 1.5 wt.%) were prepared for the catalytic oxidation of propane. The unique nanorod-like structure and high specific surface area of TiO2-Rod support was favorable for the surface distribution of ruthenium nanoparticles, constructing highly active redox sites for propane oxidation. Light-off experimental results indicated that the x-Ru/TiO2-Rod catalysts exhibited diverse catalytic activities for propane oxidation, giving a volcanic sequence of 0.1-Ru/TiO2-Rod < 0.5-Ru/TiO2-Rod < 1.5-Ru/TiO2-Rod < 1.0-Ru/TiO2-Rod with the increasing ruthenium content. Additionally, the optimal 1.0-Ru/TiO2-Rod delivered adequate catalytic stability and CO2/water resistant ability under complex industrial conditions. Characterization results revealed that the metallic Ru0 and the surface lattice oxygen species from the Ru-TiO2 interface were demonstrated to be the catalytic active components, which played an essential role in the reaction. In situ DRIFTs analysis verified the formation of acetate, acetone and formate species as the predominant organic intermediates in propane oxidation, which may result from two plausible reaction pathways depending on the activation of terminal methyl group (–CH3) and the central methylene (CH2) group in propane molecule. This work provides fundamental guidance for the development of Ru-based catalysts and the reaction mechanism understanding for light alkanes oxidation.

Dynamic Ti3+ and In3+ dual active sites on In2TiO5 to enhance visible-light-driven gas-phase photocatalytic CO2 reduction

Amorphous materials offer novel and cooperative active sites that challenge the limits of heterogeneous crystalline catalysts. This work represents an initial development of a feasible amorphous photocatalyst for CO2 photoreduction. We optimise the bandgap and crystal structure of amorphous In2TiO5 to facilitate the conversion of CO2 to CH4. The XAFS analysis identifies Ti3+ as the active site. The reaction between H2O and In3+ produces protons that lower the oxidation state of In3+ to In2+. Moreover, adding 2D nanolayers of MoSe2 to In2TiO5 increases CH4 production from 4.14 to 6.15 µmol/g. We report the effect of multiphoton flux and find that it leads to a 1.28-fold increase in CH4 production. The combined in situ DRIFTS and DFT analyses elucidate underlying chemical pathways in photocatalytic CO2 reduction.