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Journal articles on the topic 'Distribution H∞ filtering'
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Hu, Songlin, Dong Yue, and Jinliang Liu. "H∞ filtering for networked systems with partly known distribution transmission delays." Information Sciences 194 (July 2012): 270–82. http://dx.doi.org/10.1016/j.ins.2011.12.026.
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Wang, Guoliang, and Chengli Su. "Delay-distribution-dependent H? filtering for linear systems with stochastic time-varying delays." Journal of the Franklin Institute 350, no. 2 (March 2013): 358–77. http://dx.doi.org/10.1016/j.jfranklin.2012.11.009.
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Qian, Xueming, and Baotong Cui. "Distributed H ∞ Consensus Filtering for Parabolic Distributed Parameter Systems with Multiple Missing Measurements: A Mobile Sensing Approach." Journal of Control Science and Engineering 2023 (February 13, 2023): 1–17. http://dx.doi.org/10.1155/2023/9740248.
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This paper investigates the distributed H ∞ consensus filtering issue for a class of distributed parameter systems with bounded disturbance. In a framework of optimizing performance, a new approach to improving filter performance is proposed by employing mobile sensor networks. Moreover, the information missing in mobile sensor networks is modeled as a conditional probability distribution. The aim of the filtering challenge is to construct a distributed consensus filter such that the filtering error system is globally asymptotically stable in the mean square, and what disturbances do to the estimation accuracy is attenuated at the H ∞ consensus performance level. Utilizing the Lyapunov direct approach and the spatial operator technique, several sufficient criteria are given for the proposed filter to satisfy the H ∞ consensus performance constraint. Finally, a numerical simulation is given to demonstrate the effectiveness of the design scheme of the proposed filter.
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Yu, Haiyang, Rubo Zhang, Junwei Wu, and Xiuwen Li. "Distributed Field Estimation Using Sensor Networks Based on H∞ Consensus Filtering." Sensors 18, no. 10 (October 20, 2018): 3557. http://dx.doi.org/10.3390/s18103557.
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This paper is concerned with the distributed field estimation problem using a sensor network, and the main purpose is to design a local filter for each sensor node to estimate a spatially-distributed physical process using the measurements of the whole network. The finite element method is employed to discretize the infinite dimensional process, which is described by a partial differential equation, and an approximate finite dimensional linear system is established. Due to the sparsity on the spatial distribution of the source function, the ℓ 1 -regularized H ∞ filtering is introduced to solve the estimation problem, which attempts to provide better performance than the classical centralized Kalman filtering. Finally, a numerical example is provided to demonstrate the effectiveness and applicability of the proposed method.
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Ristic, Dragan, Milan Pavlovic, Miomir Mijic, and Irini Reljin. "Improvement of the multifractal method for detection of early reflections." Serbian Journal of Electrical Engineering 11, no. 1 (2014): 11–24. http://dx.doi.org/10.2298/sjee131201002r.
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This paper presents the research that was aimed at examining the possibilities for improving the multifractal method for detecting early reflections in the room impulse response. Multifractal method for the detection of early reflections uses distribution of H?lder?s exponent calculated for the acoustic impulse response. Modifications of algorithm proposed in this paper perform filtering of the distribution of H?lder?s exponent to improve the detection of significant early reflections. The results obtained in this way provide guidance how to improve detection of early reflections and to make it more precise.
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Tokarz, Elizabeth L., Pablo Álvia, Renato Valencia, and Simon A. Queenborough. "Habitat filtering of six coexisting Heliconia species in a lowland tropical rain forest in Amazonian Ecuador." Journal of Tropical Ecology 35, no. 2 (March 2019): 91–94. http://dx.doi.org/10.1017/s0266467419000026.
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AbstractHerbaceous plants are often under-studied in tropical forests, despite their high density and diversity, and little is known about the factors that influence their distribution at microscales. In a 25-ha plot in lowland Amazonian rain forest in Yasuní National Park, Ecuador, we censused six species of Heliconia (Heliconiaceae) in a stratified random manner across three topographic habitat types. We observed distribution patterns consistent with habitat filtering. Overall, more individuals occurred in the valley (N = 979) and slope (N = 847) compared with the ridge (N = 571) habitat. At the species level, Heliconia stricta (N = 1135), H. spathocircinata (N = 309) and H. ortotricha (N = 36) all had higher abundance in the valley and slope than ridge. Further, H. vellerigera (N = 20) was completely absent from the ridge. Conversely, H. velutina (N = 903) was most common in the drier ridge habitat. The two most common species (H. stricta and H. velutina) had a reciprocal or negative co-occurrence pattern and occurred preferentially in valley versus ridge habitats. These results suggest that taxa within this family have different adaptations to the wetter valley versus the drier ridge and that habitat partitioning contributes to coexistence.
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Rigatos, Gerasimos, Dimitrios Serpanos, Vasilios Siadimas, Krishna Busawon, Zhiwei Gao, Pierluigi Siano, and Masoud Abbaszadeh. "Condition monitoring for the quadruple water tank system using H-infinity Kalman Filtering." MATEC Web of Conferences 188 (2018): 05008. http://dx.doi.org/10.1051/matecconf/201818805008.
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The problem of statistical fault diagnosis for the quadruple watertanks system is examined. The solution of the fault diagnosis problem for the dynamic model of the four-water tanks system is a non-trivial case, due to nonlinearities and the system’s multivariable structure. In the article’s approach, the system’s dynamic model undergoes first approximate linearization around a temporary operating point which is recomputed at each sampling period. The linearization procedure relies on Taylor series expansion and on the computation of the Jacobian matrices of the state-space description of the system. The H-infinity Kalman Filter is used as a robust state estimator for the approximately linearized model of the quadruple water tanks system. By comparing the outputs of the H-infinity Kalman Filter against the outputs measured from the real water tanks system the residuals sequence is generated. It is concluded that the sum of the squares of the residuals’ vectors, being weighted by the inverse of the associated covariance matrix, stands for a stochastic variable that follows the χ2 distribution. As a consequence, a statistical method for condition monitoring of the quadruple water tanks system is drawn, by using the properties of the χ2 distribution and the related confidence intervals. Actually, normal functioning can be ensured as long as the value of the aforementioned stochastic variable stays within the previously noted confidence intervals. On the other side, one can infer the malfunctioning of the quadruple water tanks system with a high level of certainty (e.g. of the order of 96% to 98%), when these confidence intervals are exceeded. The article’s method allows also for fault isolation, that is for identifying the specific component of the quadruple water tanks system that has been subject to fault or cyber-attack.
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Jung, Woohyung, Su Hyun Seok, Soyoung Shin, Sung Ha Ryu, Kyu-Bong Kim, Beom Soo Shin, and Tae Hwan Kim. "Toxicokinetics, Percutaneous Absorption and Tissue Distribution of Benzophenone-3, an UV Filtering Agent, in Rats." Toxics 10, no. 11 (November 7, 2022): 672. http://dx.doi.org/10.3390/toxics10110672.
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The aim of this study was to evaluate in vitro skin permeation and deposition, in vivo toxicokinetics, percutaneous absorption and tissue distribution of benzophenone-3 (BP-3) in rats. Four transdermal formulations containing BP-3 were prepared and evaluated for in vitro skin permeation and deposition of BP-3 using Franz diffusion cells. A gel formulation was used in subsequent in vivo percutaneous absorption due to its high in vitro skin permeation and deposition. Compared to intravenous (i.v.) injection, the prolonged terminal t1/2 (3.1 ± 1.6 h for i.v. injection and 18.3 ± 5.8 h for topical application) was observed indicating occurrence of flip-flop kinetics after topical application. The bioavailability of BP-3 after topical application was 6.9 ± 1.8%. The tissue-to-plasma partition coefficient (kp) for testis, considered a toxic target for BP-3, was less than 1.. Overall, findings of this study may be useful for risk assessment of BP-3.
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Voltolini, Marco, Maria Chiara Dalconi, Gilberto Artioli, Matteo Parisatto, Luca Valentini, Vincenzo Russo, Anne Bonnin, and Remi Tucoulou. "Understanding cement hydration at the microscale: new opportunities from `pencil-beam' synchrotron X-ray diffraction tomography." Journal of Applied Crystallography 46, no. 1 (January 17, 2013): 142–52. http://dx.doi.org/10.1107/s0021889812046985.
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The present work describes some new improvements concerning the analysis of cement hydration processes using `pencil-beam' synchrotron X-ray diffraction tomography. (i) A new filtering procedure, applied to the diffraction images, has been developed to separate the powder-like contribution from that of the grains in the diffraction images. (ii) In addition to improving the quality of the diffraction images for the subsequent analysis and tomographic reconstruction, the filtering procedure can also be used to perform a qualitative analysis of the crystallite size distribution, whenever the more standard approaches cannot be applied. (iii) Given the importance of the calcium silicate hydrate phase (C–S–H) in cements, a procedure to obtain its spatial distribution using the diffraction signal has been successfully applied, even though C–S–H is a highly disordered phase, almost amorphous to X-ray diffraction. (iv) The main result of this study has been to show that, in spite of the long measurement times required, it is possible to usein situexperiments at different aging times of cement pastes to monitor the cement evolution. This allowed the evolution of the microstructure during the acceleration and deceleration periods of the hydration process to be checked with unprecedented detail, since the quantitative spatial distribution of each phase (including C–S–H) dissolved or precipitated in the sample has been obtained. The reported approach opens up a range of opportunities for the investigation of complex multiphase systems and processes, including hydration and microstructural development in cements.
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Wang, Jinxia, Jinfeng Gao, Tian Tan, Jiaqi Wang, and Miao Ma. "Event-Triggered H ∞ Filtering for Markovian Jump Neural Networks under Random Missing Measurements and Deception Attacks." Complexity 2020 (December 28, 2020): 1–19. http://dx.doi.org/10.1155/2020/4151542.
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This paper concentrates on the event-triggered H ∞ filter design for the discrete-time Markovian jump neural networks under random missing measurements and cyber attacks. Considering that the controlled system and the filtering can exchange information over a shared communication network which is vulnerable to the cyber attacks and has limited bandwidth, the event-triggered mechanism is proposed to relieve the communication burden of data transmission. A variable conforming to Bernoulli distribution is exploited to describe the stochastic phenomenon since the missing measurements occur with random probability. Furthermore, seeing that the communication networks are vulnerable to external malicious attacks, the transferred information via the shared communication network may be changed by the injected false information from the attackers. Based on the above consideration, sufficient conditions for the filtering error system to maintain asymptotically stable are provided with predefined H ∞ performance. In the end, three numerical examples are given to verify the proposed theoretical results.
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Zhang, Shuaishuai, Youhong Wan, Jie Ding, and Yangyang Da. "State of Charge (SOC) Estimation Based on Extended Exponential Weighted Moving Average H∞ Filtering." Energies 14, no. 6 (March 17, 2021): 1655. http://dx.doi.org/10.3390/en14061655.
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When the classical H∞ algorithm (HIF) is applied to estimate the state of charge (SOC) of a lithium battery, the influence of historical data is usually ignored, resulting in an increase in the estimation error. In order to improve the accuracy of SOC estimation, this paper proposes an extended exponential weighted moving average H∞ algorithm (EE-HIF) in view of the influence of historical data. By designing the Gaussian function, the weighted distribution of the data at different times can effectively reduce the estimation error caused by the inaccuracy of the lithium battery model. In addition, when the system contains Gaussian white noise and alternating current input, the proposed method can achieve a faster convergence speed and better robustness. Simulation results show the advantages of the proposed algorithm, as compared to an HIF filtering algorithm and an exponentially weighted moving average H∞ algorithm (EWMA).
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Nithya, Venkatesan, Rathinasamy Sakthivel, and Yong Ren. "Resilient H-infinity filtering for networked nonlinear Markovian jump systems with randomly occurring distributed delay and sensor saturation." Nonlinear Analysis: Modelling and Control 26, no. 2 (March 1, 2021): 187–206. http://dx.doi.org/10.15388/namc.2021.26.22355.
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The H∞ filtering problem for a class of networked nonlinear Markovian jump systems subject to randomly occurring distributed delays, nonlinearities, quantization effects, missing measurements and sensor saturation is investigated in this paper. The measurement missing phenomenon is characterized via a random variable obeying the Bernoulli stochastic distribution. Moreover, due to bandwidth limitations, the measurement output is quantized using a logarithmic quantizer and then transmitted to the filter. Further, the output measurements are affected by sensor saturation since the communication links between the system and the filter are unreliable and is described by sector nonlinearities. The objective of this work is to design a quantized resilient filter that guarantees not only the stochastic stability of the augmented filtering error system but also a prespecified level of H∞ performance. Sufficient conditions for the existence of desired filter are established with the aid of proper Lyapunov–Krasovskii functional and linear matrix inequality approach together with stochastic analysis theory. Finally, a numerical example is presented to validate the developed theoretical results.
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Xie, Mengjun, Dagang Liu, Huihui Wang, and Laqun Liu. "Study on the Correlation between Magnetic Field Structure and Cold Electron Transport in Negative Hydrogen Ion Sources." Applied Sciences 12, no. 9 (April 19, 2022): 4104. http://dx.doi.org/10.3390/app12094104.
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In most negative hydrogen ion sources, an external magnet is installed near the extraction region to reduce the electron temperature. In this paper, the self-developed CHIPIC code is used to simulate the mechanism of a magnetic filter system, in the expansion region of the negative hydrogen ion source, on “hot” electrons. The reflection and the filtering processes of “hot” electrons are analyzed in depth and the energy distribution of electrons on the extraction surface is calculated. Moreover, the effects of different collision types on the density distribution of “cold” electrons along the X-axis and the spatial distribution of “cold” electrons on the X−Z plane are discussed. The numerical results show that the electron reflection is caused by the magnetic mirror effect. The filtering of “hot” electrons is due to the fact that the magnetic field constrains most of the electrons from reaching the vicinity of the extraction surface, being that collisions cause a decay in electron energy. Excitation collision is the main decay mechanism for electron energy in the chamber. The numerical results help to explain the formation process of “cold” electrons at the extraction surface, thus providing a reference for reducing the loss probability of H−.
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Adeyemo, I. A., O. A. Adegbola, and O. W. Adebiyi. "Reactive Power Compensation and Harmonic Mitigation in Single-Phase Distribution System using Multilevel Converter Based D-STATCOM." International Journal of Engineering and Applied Computer Science 04, no. 04 (June 4, 2022): 47–52. http://dx.doi.org/10.24032/ijeacs/0404/011.
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This paper presents a study of a single-phase cascaded H-bridge multilevel converter-based Distribution Static Synchronous Compensator (D-STATCOM) with active harmonic filtering capability. For the proper operation of the proposed D-STATCOM, a constant voltage is maintained at its DC bus link using a proportional and integral (PI) controller. Based on instantaneous current errors, gate pulses for controlling duty cycles of the D-STATCOM operation are generated using the hysteresis current control (HCC) technique. The proposed D-STATCOM was modeled and simulated in MATLAB. Simulation results show that the proposed method effectively compensates for reactive power and mitigates current harmonics. The proposed method offers structural simplicity and efficiency without complex calculations.
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Lynn, Barry H., Guy Kelman, and Gary Ellrod. "An Evaluation of the Efficacy of Using Observed Lightning to Improve Convective Lightning Forecasts." Weather and Forecasting 30, no. 2 (April 1, 2015): 405–23. http://dx.doi.org/10.1175/waf-d-13-00028.1.
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Abstract Dynamic lightning forecasts [total and cloud to ground (CG)] were produced on a convection-allowing forecast grid with 4-km grid spacing with lightning assimilation (ASML) and without lightning assimilation [control (CNTL)]. A dynamic scheme produces time- and space-dependent potential electrical energy, which then converts this energy into lightning (e.g., number per hour per grid element). The assimilation scheme uses observed, gridded total lightning to determine how much water vapor is added at constant temperature in the mixed-phase region, leading to a convective response. ASML and CNTL lightning forecasts were compared to observed total and CG lightning. Four case studies—each representing a different type of convective regime—demonstrate that the spatial distribution and intensity of forecast lightning were improved when lightning assimilation was used. Over 3 days in March 2012, eight 18-h lightning forecasts quantified the advantages in forecast accuracy. Equitable threat scores for forecast CG lightning associated with strong [25 (3 h)−1], very strong [50 (3 h)−1], and extreme [100 (3 h)−1] events were significantly more accurate for convective storms that developed in forecasts with lightning assimilation than without. Improvements in forecasts of very strong and extreme events occurred out to 9 h of forecast time, while the forecasts of strong events showed improvement out to 15 h. Spurious convection was removed with filtering in one case study, which led to a notable improvement in the timing and intensity of the squall line. Sensitivity tests examined the utility of this filtering approach, and the importance of reducing mass imbalances liable to occur when too much water vapor mass is introduced into the model.
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Jiao, Yang, Derong Zhang, Yiwen Xu, Yang Chen, Zhe Wu, and Yaoyao Cui. "H-scan Subtraction Doppler Imaging: A Novel Ultrasound Small Blood Vessel Flow Characterization with Scattering and Reflection Identification." Applied Sciences 10, no. 21 (October 28, 2020): 7604. http://dx.doi.org/10.3390/app10217604.
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Ultrafast compound Doppler imaging (UCDI), which can be used to acquire Doppler information at very high spatial and temporal sampling rates, provides a great improvement to the characterization of the vasculature. The singular value decomposition (SVD) technique takes advantage of the different features of tissue and blood motion in terms of spatiotemporal coherence and strongly outperforms conventional clutter rejection filters in small animals. However, a major challenge of conventional UCDI with SVD clutter filtering for small vessel imaging is that it is not sensitive enough to detect the hemodynamic changes in deep tissue where the majority of the remaining signal is usually noise-saturated. In this study, with the first attempt to apply ultrasonic tissue characterization techniques to UCDI, we propose an H-scan subtraction Doppler imaging method to bypass the limitations associated with the high-order singular value thresholding selection and improve the image quality of fine vessels. The flow phantom experiments with different blood concentrations show that H-Scan is capable of estimating the relative size and spatial distribution of acoustic scattering objects. In the in vivo rabbit brain experiment, the H-Doppler method, together with the global and block-wise local SVD clutter filtering, are proposed to facilitate better power Doppler images with a significant improvement of background noise suppression. These results demonstrate that the contrast-to-noise-ratio (CNR) of the H-scan subtraction Doppler imaging is 15% to 65% higher than that of the conventional UCDI methods. Therefore, this approach can be potentially applied to the clinical applications of the functional ultrasound (fUS) imaging method.
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Юрченко, А. В., Д. М. Николенко, И. А. Рачек, Д. К. Топорков, and Ю. В. Шестаков. "Моделирование движения молекул H-=SUB=-2-=/SUB=- и D-=SUB=-2-=/SUB=- в секступольных магнитах." Журнал технической физики 89, no. 9 (2019): 1325. http://dx.doi.org/10.21883/jtf.2019.09.48057.378-18.
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The simulation of the movement of hydrogen and deuterium molecules in the magnetic system of the installation designed to obtain nuclear spin-polarized molecules is produced. For the spatial separation of molecules with different projections of the magnetic moments of spin filtering method in a nonuniform magnetic field, superconducting sextupole magnets are used. The calculation was performed when the induction of the magnetic field near the poles of 3.7 T and the nozzle temperature of the 7K. The simulation showed that the ratio of the polarized flux of hydrogen molecules into the detector to the total flux from the source nozzle is 2.3 × 10-6, and the nuclear polarization is about 100%. For deuterium, the calculations showed that this ratio is 7 times less because of the smallness of the magnetic moment with respect to hydrogen molecules. The graphs of molecular trajectories in the magnetic system and their spatial distribution are presented. The mathematical aspects of the developed computer program algorithm are considered.
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Sağlam, Üstün, and Ahmet Tekin. "Resonance-filtering combo system for continuous wireless charging range coverage." Wireless Power Transfer 7, no. 2 (September 2020): 116–25. http://dx.doi.org/10.1017/wpt.2020.12.
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AbstractDistribution of wireless power charging field uniformly on a large area pad is critical for power receivers, particularly for wearable devices, wherein small form factor coils are involved. Since the receiver coil size is quite limited in these types of applications, the device is very sensitive to the amount of field it could retain and hence, it needs special placement or snapping mechanism to fix it at an optimum location for reliable wireless charging. In order to overcome this limitation for the end-user, a dual-mode multi-coil power transceiver system is proposed; utilizing resonance filtering to increase the amount of total power delivered with the rather uniform spatial distribution. Two concentric coils; center one driven by 6.78-MHz high-frequency driver (A4WP) and the outer larger one with a 200-KHz low-frequency driver (Qi) with resonant blocker could transfer up to 50 mW standards compliant flat power to a 13-mm radius 30-turns wearable receiver coil everywhere across an 8-cm radius charging pad area without any alignment requirement or snapping. Two different feedback topologies corresponding to each of the H-Bridge power drivers were also presented as an automatic series resonance coil drive frequency lock mechanism, extracting peak powers for each system individually from a standard 5 V-1A USB wall charger.
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Williams, Stephen R., and Greg J. Stuart. "Site Independence of EPSP Time Course Is Mediated by DendriticI h in Neocortical Pyramidal Neurons." Journal of Neurophysiology 83, no. 5 (May 1, 2000): 3177–82. http://dx.doi.org/10.1152/jn.2000.83.5.3177.
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Neocortical layer 5 pyramidal neurons possess long apical dendrites that receive a significant portion of the neurons excitatory synaptic input. Passive neuronal models indicate that the time course of excitatory postsynaptic potentials (EPSPs) generated in the apical dendrite will be prolonged as they propagate toward the soma. EPSP propagation may, however, be influenced by the recruitment of dendritic voltage-activated channels. Here we investigate the properties and distribution of I h channels in the axon, soma, and apical dendrites of neocortical layer 5 pyramidal neurons, and their effect on EPSP time course. We find a linear increase (9 pA/100 μm) in the density of dendritic I hchannels with distance from soma. This nonuniform distribution of I h channels generates site independence of EPSP time course, such that the half-width at the soma of distally generated EPSPs (up to 435 μm from soma) was similar to somatically generated EPSPs. As a corollary, a normalization of temporal summation of EPSPs was observed. The site independence of somatic EPSP time course was found to collapse after pharmacological blockade of I h channels, revealing pronounced temporal summation of distally generated EPSPs, which could be further enhanced by TTX-sensitive sodium channels. These data indicate that an increasing density of apical dendritic I hchannels mitigates the influence of cable filtering on somatic EPSP time course and temporal summation in neocortical layer 5 pyramidal neurons.
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Di Gioia, Serafina, Stefano Cristiani, Gabriella De Lucia, and Lizhi Xie. "Damped Ly α absorbers and atomic hydrogen in galaxies: the view of the GAEA model." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 22, 2020): 2469–85. http://dx.doi.org/10.1093/mnras/staa2067.
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ABSTRACT Using the GAEA semi-analytic model, we analyse the connection between Damped Ly α systems (DLAs) and H i in galaxies. Our state-of-the-art semi-analytic model is tuned to reproduce the local galaxy H i mass function, and that also reproduces other important galaxy properties, including the galaxy mass–gas metallicity relation. To produce catalogues of simulated DLAs we throw 105 random lines of sight in a composite simulated volume: dark matter haloes with log$(\frac{M_{200}}{ {\rm M}_{\odot }}) \ge 11.5$ are extracted from the Millennium Simulation, while for $9.2 \le \log (\frac{M_{200}}{ \mathrm{M}_{\odot }})\lt 11.5$ we use the Millennium II, and for $8 \le \log (\frac{M_{200}}{\mathrm{M}_{\odot }}) \lt 9.2$ a halo occupation distribution model. At 2 < z < 3, where observational data are more accurate, our fiducial model predicts the correct shape of the column density distribution function, but its normalization falls short of the observations, with the discrepancy increasing at higher redshift. The agreement with observations is significantly improved increasing both the H i masses and the disc radii of model galaxies by a factor of 2, as implemented ‘a posteriori’ in our 2M−2R model. In the redshift range of interest, haloes with $M_{200} \ge {10}^{11} \, \mathrm{M}_{\odot }$ give the major contribution to ΩDLA, and the typical DLA host halo mass is $\sim \!{10}^{11} \, \mathrm{M}_{\odot }$. The simulated DLA metallicity distribution is in relatively good agreement with observations, but our model predicts an excess of DLAs at low metallicities. Our results suggest possible improvements for the adopted modelling of the filtering mass and metal ejection in low-mass haloes.
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Bárdossy, András, Jochen Seidel, and Abbas El Hachem. "The use of personal weather station observations to improve precipitation estimation and interpolation." Hydrology and Earth System Sciences 25, no. 2 (February 10, 2021): 583–601. http://dx.doi.org/10.5194/hess-25-583-2021.
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Abstract. The number of personal weather stations (PWSs) with data available through the internet is increasing gradually in many parts of the world. The purpose of this study is to investigate the applicability of these data for the spatial interpolation of precipitation using a novel approach based on indicator correlations and rank statistics. Due to unknown errors and biases of the observations, rainfall amounts from the PWS network are not considered directly. Instead, it is assumed that the temporal order of the ranking of these data is correct. The crucial step is to find the stations which fulfil this condition. This is done in two steps – first, by selecting the locations using the time series of indicators of high precipitation amounts. Then, the remaining stations are then checked for whether they fit into the spatial pattern of the other stations. Thus, it is assumed that the quantiles of the empirical distribution functions are accurate. These quantiles are then transformed to precipitation amounts by a quantile mapping using the distribution functions which were interpolated from the information from the German National Weather Service (Deutscher Wetterdienst – DWD) data only. The suggested procedure was tested for the state of Baden-Württemberg in Germany. A detailed cross validation of the interpolation was carried out for aggregated precipitation amount of 1, 3, 6, 12 and 24 h. For each of these temporal aggregations, nearly 200 intense events were evaluated, and the improvement of the interpolation was quantified. The results show that the filtering of observations from PWSs is necessary as the interpolation error after the filtering and data transformation decreases significantly. The biggest improvement is achieved for the shortest temporal aggregations.
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Davies, Patrick, Roland Baatz, Heye Reemt Bogena, Emmanuel Quansah, and Leonard Kofitse Amekudzi. "Optimal Temporal Filtering of the Cosmic-Ray Neutron Signal to Reduce Soil Moisture Uncertainty." Sensors 22, no. 23 (November 25, 2022): 9143. http://dx.doi.org/10.3390/s22239143.
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Cosmic ray neutron sensors (CRNS) are increasingly used to determine field-scale soil moisture (SM). Uncertainty of the CRNS-derived soil moisture strongly depends on the CRNS count rate subject to Poisson distribution. State-of-the-art CRNS signal processing averages neutron counts over many hours, thereby accounting for soil moisture temporal dynamics at the daily but not sub-daily time scale. This study demonstrates CRNS signal processing methods to improve the temporal accuracy of the signal in order to observe sub-daily changes in soil moisture and improve the signal-to-noise ratio overall. In particular, this study investigates the effectiveness of the Moving Average (MA), Median filter (MF), Savitzky–Golay (SG) filter, and Kalman filter (KF) to reduce neutron count error while ensuring that the temporal SM dynamics are as good as possible. The study uses synthetic data from four stations for measuring forest ecosystem–atmosphere relations in Africa (Gorigo) and Europe (SMEAR II (Station for Measuring Forest Ecosystem–Atmosphere Relations), Rollesbroich, and Conde) with different soil properties, land cover and climate. The results showed that smaller window sizes (12 h) for MA, MF and SG captured sharp changes closely. Longer window sizes were more beneficial in the case of moderate soil moisture variations during long time periods. For MA, MF and SG, optimal window sizes were identified and varied by count rate and climate, i.e., redestimates temporal soil moisture dynamics by providing a compromise between monitoring sharp changes and reducing the effects of outliers. The optimal window for these filters and the Kalman filter always outperformed the standard procedure of simple 24-h averaging. The Kalman filter showed its highest robustness in uncertainty reduction at three different locations, and it maintained relevant sharp changes in the neutron counts without the need to identify the optimal window size. Importantly, standard corrections of CRNS before filtering improved soil moisture accuracy for all filters. We anticipate the improved signal-to-noise ratio to benefit CRNS applications such as detection of rain events at sub-daily resolution, provision of SM at the exact time of a satellite overpass, and irrigation applications.
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Salah, F. Abdellah Ali, and Said Gad Ehab. "Synthesis and Evaluation of Polysulfone/Polyaniline Nanocomposite Reverse Osmosis Membranes using Sodium Butyl Sulfate." Research Journal of Chemistry and Environment 25, no. 8 (July 25, 2022): 90–99. http://dx.doi.org/10.25303/258rjce9099.
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The most prevalent problems of the desalination process are the clogging of membranes and their deterioration utilising free chlorine. As a substratum for the active polyamide layer, a mixture of nanocomposite polysulfone/polyaniline was produced. In this work, the use of a simple chemical oxidative polymerisation process was used for nano polyaniline emeraldine salt. In the presence of sodium butyl sulphate, it has been added to the substratum layer of polysulfone (PS) as a hydrophilic agent to increase the composite membrane reverse osmosis characteristics. Nano-particle membranes with XRD, EDX, FT-IR, SEM, particle size distribution and contact angle were studied in both non-modified and modified polyaniline. The membrane efficiency has been assessed using a crossflow filtering device in terms of water flow and salt rejection. The results demonstrated that the water permeability of the nano-composite membrane (65 L/m2/h) was substantially superior to that of the control membrane (56 L/m2/h) without any significant change in the percentage of salt repulsion. Bovine serum albumin (BSA) as fouling model has been studied and sodium hypochlorite is used for the resistance of membranes to biofouling and chlorine degradation. Due to significant electrostatic repulsion between polyaniline PANI and BSA, the modified membrane was more resistant to biofouling and chlorine assault. Increased performance in reverse osmosis of a thin film composite was achieved using the polysulfonepolyaniline nano-composite substrate produced.
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LAMSKOVA, M. I., M. I. FILIMONOV, Y. I. SUKHAREV, A. E. NOVIKOV, and S. V. BORODYCHEV. "OPTIMIZATION OF THE DESIGN-OPERATING PARAMETERS OF THE HYDROCYCLONE TAKING INTO ACCOUNT FIELD RESEARCH." Prirodoobustrojstvo, no. 4 (2020): 61–67. http://dx.doi.org/10.26897/1997-6011-2020-4-61-67.
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Cylindrical-conical pressure hydrocyclones are characterized by high productivity and efficiency indicators of water treatment from mechanical impurities at a relatively small size and cost, low resource costs for operation, which makes their use promising as a water treatment unit in the circulating water distribution systems of domestic and foreign industry. The purpose of the research is development of the construction of a filtering hydrocyclone and assessment of the impact of the fl ow characteristics and size of the sand pipe on the separative power of the apparatus in the process of water teratment from mechanical impurities. The presented design of the hydrocyclone apparatus with a filter drain pipe allows to increase water treatment rates from mechanical impurities including by trapping the smallest suspensions. As a result of experimental research of the effect of the flow characteristics and size of the sand pipe on the separative power of the apparatus, the technological and construction parameters of the PH-100 hydrocyclone with various versions of the drain pipe providing maximum efficiency of water treatment from mechanical impurities have been established. The graphoanalytic solution of the obtained regression equations has allowed us to establish that a hydrocyclone with a solid side wall drain pipe provides the maximum degree of water treatment from mechanical impurities at the level of 85.4% at a flow rate of 6.5 m3/h and a 12 mm diameter of the sand pipe. Replacing the standard construction drain pipe with a filtering side surface drain pipe increases the integral degree of water treatment from mechanical impurities to 96.4% with the same flow parameters and diameter of the sand pipe.
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Alzoubi, Islam, Guoqing Bao, Rong Zhang, Christina Loh, Yuqi Zheng, Svetlana Cherepanoff, Gary Gracie, et al. "An Open-Source AI Framework for the Analysis of Single Cells in Whole-Slide Images with a Note on CD276 in Glioblastoma." Cancers 14, no. 14 (July 15, 2022): 3441. http://dx.doi.org/10.3390/cancers14143441.
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Routine examination of entire histological slides at cellular resolution poses a significant if not insurmountable challenge to human observers. However, high-resolution data such as the cellular distribution of proteins in tissues, e.g., those obtained following immunochemical staining, are highly desirable. Our present study extends the applicability of the PathoFusion framework to the cellular level. We illustrate our approach using the detection of CD276 immunoreactive cells in glioblastoma as an example. Following automatic identification by means of PathoFusion’s bifocal convolutional neural network (BCNN) model, individual cells are automatically profiled and counted. Only discriminable cells selected through data filtering and thresholding were segmented for cell-level analysis. Subsequently, we converted the detection signals into the corresponding heatmaps visualizing the distribution of the detected cells in entire whole-slide images of adjacent H&E-stained sections using the Discrete Wavelet Transform (DWT). Our results demonstrate that PathoFusion is capable of autonomously detecting and counting individual immunochemically labelled cells with a high prediction performance of 0.992 AUC and 97.7% accuracy. The data can be used for whole-slide cross-modality analyses, e.g., relationships between immunochemical signals and anaplastic histological features. PathoFusion has the potential to be applied to additional problems that seek to correlate heterogeneous data streams and to serve as a clinically applicable, weakly supervised system for histological image analyses in (neuro)pathology.
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Jindal, Silky, G. S. S. Saini, Ranjan Kumar, and S. K. Tripathi. "Ultrahigh power factor in thermally evaporated Bi/Ag2Se bi-layer obtained using thermal inter-diffusion." Journal of Applied Physics 132, no. 23 (December 21, 2022): 235303. http://dx.doi.org/10.1063/5.0127015.
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Bi/Ag2Se bi-layer (ASB) has been deposited using simple thermal evaporation. Both the layers are interdiffused thermally at transition temperatures of 130 (ASB-130) and at 210 °C (ASB-210) for a soaking time of 1 h each. ASB-210 shows a promising in-plane thermoelectric power factor of 1.4 mW/m K2 at 30 °C and 1.5 mW/m K2 at 90 °C. This ultrahigh value in ASB-210 is due to simultaneous improvement in carrier concentration and mobility values (enhances σ). Moreover, (013) grain orientation and uniform distribution of Ag and Bi in Ag2Se matrix are inferred to be other reasons for power factor improvement. The power factor of ASB-210 is found to be nearly stable in the temperature range of 30–90 °C. This constant value is accredited to suppression of bipolar effect in Ag2Se by Ag and Bi nano-inclusions. Ag, Bi impurities are held responsible for carrier scattering. Moreover, formation of Ag/Ag2Se and Bi/Ag2Se heterostructures promotes hot carrier filtering, which enhances the Seebeck coefficient. Thus, decoupling of electrical conductivity and Seebeck coefficient is achieved. This technique of enhancing thermoelectric performance has not been reported for Ag2Se films.
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Churnside, James H., Eirik Tenningen, and James J. Wilson. "Comparison of data-processing algorithms for the lidar detection of mackerel in the Norwegian Sea." ICES Journal of Marine Science 66, no. 6 (February 21, 2009): 1023–28. http://dx.doi.org/10.1093/icesjms/fsp026.
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Abstract Churnside, J. H., Tenningen, E., and Wilson, J. J. 2009. Comparison of data-processing algorithms for the lidar detection of mackerel in the Norwegian Sea. – ICES Journal of Marine Science, 66: 1023–1028. A broad-scale lidar survey was conducted in the Norwegian Sea in summer 2002. Since then, various data-processing techniques have been developed, including manual identification of fish schools, multiscale median filtering, and curve fitting of the lidar profiles. In the automated techniques, applying a threshold to the data, as carrried out already to eliminate plankton scattering, has been demonstrated previously to improve the correlation between lidar and acoustic data. We applied these techniques to the lidar data of the 2002 survey and compared the results with those of a mackerel (Scomber scombrus) survey done by FV “Endre Dyrøy” and FV “Trønderbas” during the same period. Despite a high level of variability in both lidar and trawl data, the broad-scale distribution of fish inferred from the lidar agreed with that of mackerel caught by the FV “Endre Dyrøy”. This agreement was obtained using both manual and automated processing of the lidar data. This work is the first comparison of concurrent lidar and trawl surveys, and it demonstrates the utility of airborne lidar for mackerel studies.
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Vo, Evanly, Samy Rengasamy, and Ronald Shaffer. "Development of a Test System To Evaluate Procedures for Decontamination of Respirators Containing Viral Droplets." Applied and Environmental Microbiology 75, no. 23 (October 2, 2009): 7303–9. http://dx.doi.org/10.1128/aem.00799-09.
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ABSTRACT The aim of this study was to develop a test system to evaluate the effectiveness of procedures for decontamination of respirators contaminated with viral droplets. MS2 coliphage was used as a surrogate for pathogenic viruses. A viral droplet test system was constructed, and the size distribution of viral droplets loaded directly onto respirators was characterized using an aerodynamic particle sizer. The sizes ranged from 0.5 to 15 μm, and the sizes of the majority of the droplets were the range from 0.74 to 3.5 μm. The results also showed that the droplet test system generated similar droplet concentrations (particle counts) at different respirator locations. The test system was validated by studying the relative efficiencies of decontamination of sodium hypochlorite (bleach) and UV irradiation with droplets containing MS2 virus on filtering facepiece respirators. It was hypothesized that more potent decontamination treatments would result in corresponding larger decreases in the number of viable viruses recovered from the respirators. Sodium hypochlorite doses of 2.75 to 5.50 mg/liter with a 10-min decontamination period resulted in approximately 3- to 4-log reductions in the level of MS2 coliphage. When higher sodium hypochlorite doses (≥8.25 mg/liter) were used with the same contact time that was used for the dilute solutions containing 2.75 to 5.50 mg/liter, all MS2 was inactivated. For UV decontamination at a wavelength of 254 nm, an approximately 3-log reduction in the level of MS2 virus was achieved with dose of 4.32 J/cm2 (3 h of contact time with a UV intensity of 0.4 mW/cm2), while with higher doses of UV irradiation (≥7.20 J/cm2; UV intensity, 0.4 mW/cm2; contact times, ≥5 h), all MS2 was inactivated. These findings may lead to development of a standard method to test decontamination of respirators challenged by viral droplets.
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Schott, Wolfgang, Erwin Gutsmiedl, Karina Bernert, Ralf Engels, Roman Gernhäuser, Stefan Huber, Igor Konorov, et al. "Towards a first measurement of the free neutron bound beta decay detecting hydrogen atoms at a throughgoing beamtube in a high flux reactor." EPJ Web of Conferences 219 (2019): 04006. http://dx.doi.org/10.1051/epjconf/201921904006.
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In addition to the common 3-body decay of the neutron n → pe-ν̅e there should exist an effective 2-body subset with the electron and proton forming a Hydrogen bound state with well defined total momentum, total spin and magnetic quantum numbers. The atomic spectroscopic analysis of this bound system can reveal details about the underlying weak interaction as it mirrors the helicity distributions of all outgoing particles. Thus, it is unique in the information it carries, and an experiment unravelling this information is an analogue to the Goldhaber experiment performed more than 60 years ago. The proposed experiment will search for monoenergetic metastable BoB H atoms with 326 eV kinetic energy, which are generated at the center of a throughgoing beamtube of a high-flux reactor (e.g., at the PIK reactor, Gatchina). Although full spectroscopic information is needed to possibly reveal new physics our first aim is to prove the occurrence of this decay and learn about backgrounds. Key to the detection is the identification of a monoerergtic line of hydrogen atoms occurring at a rate of about 1 s−1 in the environment of many hydrogen atoms, however having a thermal distribution of about room temperature. Two scenarios for velocity (energy) filtering are discussed in this paper. The first builds on an purely electric chopper system, in which metastable hydrogen atoms are quenched to their ground state and thus remain mostly undetectable. This chopper system employs fast switchable Bradbury Nielsen gates. The second method exploits a strongly energy dependent charge exchange process of metastable hydrogen picking up an electron while traversing an argon filled gas cell, turning it into manipulable charged hydrogen. The final detection of hydrogen occurs through multichannel plate (MCP) detector. The paper describes the various methods and gives an outlook on rates and feasibility at the PIK reactor in Gatchina.
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Liu, Xiang, Juan Wang, Junliang Shang, Jinxing Liu, Lingyun Dai, and Shasha Yuan. "Epileptic Seizure Detection Based on Variational Mode Decomposition and Deep Forest Using EEG Signals." Brain Sciences 12, no. 10 (September 22, 2022): 1275. http://dx.doi.org/10.3390/brainsci12101275.
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Electroencephalography (EEG) records the electrical activity of the brain, which is an important tool for the automatic detection of epileptic seizures. It is certainly a very heavy burden to only recognize EEG epilepsy manually, so the method of computer-assisted treatment is of great importance. This paper presents a seizure detection algorithm based on variational modal decomposition (VMD) and a deep forest (DF) model. Variational modal decomposition is performed on EEG recordings, and the first three variational modal functions (VMFs) are selected to construct the time–frequency distribution of the EEG signals. Then, the log−Euclidean covariance matrix (LECM) is computed to represent the EEG properties and form EEG features. The deep forest model is applied to complete the EEG signal classification, which is a non-neural network deep model with a cascade structure that performs feature learning through the forest. In addition, to improve the classification accuracy, postprocessing techniques are performed to generate the discriminant results by moving average filtering and adaptive collar expansion. The algorithm was evaluated on the Bonn EEG dataset and the Freiburg long−term EEG dataset, and the former achieved a sensitivity and specificity of 99.32% and 99.31%, respectively. The mean sensitivity and specificity of this method for the 21 patients in the Freiburg dataset were 95.2% and 98.56%, respectively, with a false detection rate of 0.36/h. These results demonstrate the superior performance advantage of our algorithm and indicate its great research potential in epilepsy detection.
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Tan, Weiwei, Chunzhu Wei, Yang Lu, and Desheng Xue. "Reconstruction of All-Weather Daytime and Nighttime MODIS Aqua-Terra Land Surface Temperature Products Using an XGBoost Approach." Remote Sensing 13, no. 22 (November 22, 2021): 4723. http://dx.doi.org/10.3390/rs13224723.
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Generating spatiotemporally continuous land surface temperature (LST) data is in great demand for hydrology, meteorology, ecology, environmental studies, etc. However, the thermal infrared (TIR)-based LST measurements are prone to cloud contamination with missing pixels. To repair the missing pixels, a new XGBoost-based linking approach for reconstructing daytime and nighttime Moderate Resolution Imaging Spectroradiometer (MODIS) LST measurements was introduced. The instantaneous solar radiation and two soil-related predictors from China Data Assimilation System (CLDAS) 0.0625°/1-h data were selected as the linking variables to depict the relationship with instantaneous MODIS LST data. Other land surface properties, including two vegetation indices, the water index, the surface albedo, and topographic parameters, were also used as the predictor variables. The XGBoost method was used to fit an LST linking model by the training datasets from clear-sky pixels and was then applied to the MODIS Aqua-Terra LSTs during summer time (June to August) in 2017 and 2018 across China. The recovered LST data was further rectified with the Savitzky–Golay (SG) filtering method. The results showed the distribution of the reconstructed LSTs present a reasonable pattern for different land-cover types and topography. The evaluation results using in situ longwave radiation measurements showed the RMSE varies from 3.91 K to 5.53 K for the cloud-free pixels and from 4.42 K to 4.97 K for the cloud-covered pixels. In addition, the reconstructed LST products correlated well with CLDAS LST data with similar LST spatial patterns. The variable importance analysis revealed that the two soil-related predictors and the elevation variable are key parameters due to their great contribution to the XGBoost model performance.
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Williams, Jack G., Nick J. Rosser, Richard J. Hardy, Matthew J. Brain, and Ashraf A. Afana. "Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency." Earth Surface Dynamics 6, no. 1 (February 26, 2018): 101–19. http://dx.doi.org/10.5194/esurf-6-101-2018.
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Abstract. We present a monitoring technique tailored to analysing change from near-continuously collected, high-resolution 3-D data. Our aim is to fully characterise geomorphological change typified by an event magnitude–frequency relationship that adheres to an inverse power law or similar. While recent advances in monitoring have enabled changes in volume across more than 7 orders of magnitude to be captured, event frequency is commonly assumed to be interchangeable with the time-averaged event numbers between successive surveys. Where events coincide, or coalesce, or where the mechanisms driving change are not spatially independent, apparent event frequency must be partially determined by survey interval.The data reported have been obtained from a permanently installed terrestrial laser scanner, which permits an increased frequency of surveys. Surveying from a single position raises challenges, given the single viewpoint onto a complex surface and the need for computational efficiency associated with handling a large time series of 3-D data. A workflow is presented that optimises the detection of change by filtering and aligning scans to improve repeatability. An adaptation of the M3C2 algorithm is used to detect 3-D change to overcome data inconsistencies between scans. Individual rockfall geometries are then extracted and the associated volumetric errors modelled. The utility of this approach is demonstrated using a dataset of ∼ 9 × 103 surveys acquired at ∼ 1 h intervals over 10 months. The magnitude–frequency distribution of rockfall volumes generated is shown to be sensitive to monitoring frequency. Using a 1 h interval between surveys, rather than 30 days, the volume contribution from small (< 0.1 m3) rockfalls increases from 67 to 98 % of the total, and the number of individual rockfalls observed increases by over 3 orders of magnitude. High-frequency monitoring therefore holds considerable implications for magnitude–frequency derivatives, such as hazard return intervals and erosion rates. As such, while high-frequency monitoring has potential to describe short-term controls on geomorphological change and more realistic magnitude–frequency relationships, the assessment of longer-term erosion rates may be more suited to less-frequent data collection with lower accumulative errors.
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Rohm, Witold, Jakub Guzikowski, Karina Wilgan, and Maciej Kryza. "4DVAR assimilation of GNSS zenith path delays and precipitable water into a numerical weather prediction model WRF." Atmospheric Measurement Techniques 12, no. 1 (January 18, 2019): 345–61. http://dx.doi.org/10.5194/amt-12-345-2019.
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Abstract. The GNSS data assimilation is currently widely discussed in the literature with respect to the various applications for meteorology and numerical weather models. Data assimilation combines atmospheric measurements with knowledge of atmospheric behavior as codified in computer models. With this approach, the “best” estimate of current conditions consistent with both information sources is produced. Some approaches also allow assimilating the non-prognostic variables, including remote sensing data from radar or GNSS (global navigation satellite system). These techniques are named variational data assimilation schemes and are based on a minimization of the cost function, which contains the differences between the model state (background) and the observations. The variational assimilation is the first choice for data assimilation in the weather forecast centers, however, current research is consequently looking into use of an iterative, filtering approach such as an extended Kalman filter (EKF). This paper shows the results of assimilation of the GNSS data into numerical weather prediction (NWP) model WRF (Weather Research and Forecasting). The WRF model offers two different variational approaches: 3DVAR and 4DVAR, both available through the WRF data assimilation (WRFDA) package. The WRFDA assimilation procedure was modified to correct for bias and observation errors. We assimilated the zenith total delay (ZTD), precipitable water (PW), radiosonde (RS) and surface synoptic observations (SYNOP) using a 4DVAR assimilation scheme. Three experiments have been performed: (1) assimilation of PW and ZTD for May and June 2013, (2) assimilation of PW alone; PW, with RS and SYNOP; ZTD alone; and finally ZTD, with RS and SYNOP for 5–23 May 2013, and (3) assimilation of PW or ZTD during severe weather events in June 2013. Once the initial conditions were established, the forecast was run for 24 h. The major conclusion of this study is that for all analyzed cases, there are two parameters significantly changed once GNSS data are assimilated in the WRF model using GPSPW operator and these are moisture fields and rain. The GNSS observations improves forecast in the first 24 h, with the strongest impact starting from a 9 h lead time. The relative humidity forecast in a vertical profile after assimilation of ZTD shows an over 20 % decrease of mean error starting from 2.5 km upward. Assimilation of PW alone does not bring such a spectacular improvement. However, combination of PW, SYNOP and radiosonde improves distribution of humidity in the vertical profile by maximum of 12 %. In the three analyzed severe weather cases PW always improved the rain forecast and ZTD always reduced the humidity field bias. Binary rain analysis shows that GNSS parameters have significant impact on the rain forecast in the class above 1 mm h−1.
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Gonzalez, Luis. "Adaptive algorithms: a bibliographic review." ATH 2, no. 5 (September 18, 2021): 35–40. http://dx.doi.org/10.47460/athenea.v2i5.24.
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The analysis of a research work developed in the company C.V.G CARBONORCA of Venezuela is presented, which has two gas purification plants for the cooking area, designed to purify the gas that comes from the cooking ovens. Each plant is made up of solenoid valves, pneumatic valves, transmitters, process mimic panel and a supervisory system. All these elements are governed by a SIEMENS S5-115U PLC which is in a state of obsolescence, which is why the replacement of these automata by ALLEN BRADLEY ContolLogix automata was designed, in order to guarantee continuity in operations in plant. The research was done with a descriptive design of the field experimental type. A code for each gas treatment plant was obtained in RSLOGIX 5000 v17.00.00 and the update of the database of the supervisory system. The operation of the program was also verified through a simulation of the plant in a supervisory system, the deployment of which was designed for this purpose.
Keywords: Automation, Modernization, ControlLogix, Supervisory System, Mimic Panel
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Guo, Lei, Yumin Zhang, and Hong Wang. "FAULT DIAGNOSTIC FILTERING USING STOCHASTIC DISTRIBUTIONS IN NONLINEAR GENERALIZED H∞ SETTING." IFAC Proceedings Volumes 39, no. 13 (2006): 216–21. http://dx.doi.org/10.3182/20060829-4-cn-2909.00035.
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Guo, L., and Y. Zhang. "Generalized robust H∞ fault diagnosis filtering based on conditional stochastic distributions of system outputs." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 221, no. 6 (September 1, 2007): 857–64. http://dx.doi.org/10.1243/09596518jsce348.
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The efficiency of fault detection and diagnosis by using output probability density functions (PDFs) for stochastic time-delayed systems has been shown in practical processes. Neural network modelling has been applied to characterize the output PDFs and to the dynamical weighting system. In this paper, the system perturbations and disturbance are considered and the robust fault diagnosis design is studied for the general stochastic system in the presence of time delays. The main objective is to design linear matrix inequality (LMI)-based fault diagnostic filtering (FDF) to estimate the fault and attenuate the disturbances. The modelling errors and system uncertainties resulting from both B-spline expansion and the weighting system are merged into system disturbance. It can be seen that the resulting weighting system comprises non-linearities, uncertainties, disturbances, and time delays, and includes the non-zero initial condition. The generalized H∞ optimization is presented and applied to the fault diagnosis problem of the weighting system with the non-zero initial condition and truncated norms. Simulations are given to demonstrate the efficiency of the proposed approach.
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Wei, Guoliang, Zidong Wang, Wangyan Li, and Lifeng Ma. "A Survey on Gain-Scheduled Control and Filtering for Parameter-Varying Systems." Discrete Dynamics in Nature and Society 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/105815.
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This paper presents an overview of the recent developments in the gain-scheduled control and filtering problems for the parameter-varying systems. First of all, we recall several important algorithms suitable for gain-scheduling method including gain-scheduled proportional-integral derivative (PID) control,H2,H∞and mixedH2/H∞gain-scheduling methods as well as fuzzy gain-scheduling techniques. Secondly, various important parameter-varying system models are reviewed, for which gain-scheduled control and filtering issues are usually dealt with. In particular, in view of the randomly occurring phenomena with time-varying probability distributions, some results of our recent work based on the probability-dependent gain-scheduling methods are reviewed. Furthermore, some latest progress in this area is discussed. Finally, conclusions are drawn and several potential future research directions are outlined.
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Vytiaganets, Valentin, Valeriy Shaporev, Inna Pitak, and Antonina Baranova. "CONSTRUCTIVE DESIGN AND FEATURES OF THE PROCESSES IN THE ROASTING SHAFT FURNACES BY USING GASEOUS FUEL." Bulletin of the National Technical University «KhPI» Series: New solutions in modern technologies, no. 2(8) (June 15, 2021): 96–100. http://dx.doi.org/10.20998/2413-4295.2021.02.14.
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The article analyzes shaft furnaces for lime production. According to the method of firing, shaft furnaces are of bulk type, semi-gas type, gaseous and liquid fuels. The disadvantages of the operation of the main modern kilns during lime burning have been established. The main aggregates for high-tonnage lime production are mine lime kilns, in which blast furnace coke or anthracite, or high-quality coals are used as fuel. Generally, lean fuels are used in industries where, together with the technological cycle, carbon dioxide is used, which are contained in flue gases with a concentration of 36−40%mass. The data on the operation of six furnaces on the territory of Ukraine at the enterprises showed that gas shaft furnaces of cylindrical and slotted type with a straight-lining profile were widely used. The parameters of such furnaces are productivity from 100 to 250 tons per day, shaft diameter from 3.2 to 5.4 m, and height 6−8 furnace diameters. Most often, they use heating systems with central and two rows of peripheral injection burners without protrusion. The most critical part of all furnaces is the distribution of gas flow rates over the cross-section of the furnace shaft and the depth of radial penetration of the gas flow into the material layer. Calculations of τ1 and τП were carried out in the following way: for τ1, the temperature range of the medium was chosen from 1300 to 250−300 °С, τox − the temperature range for the material was chosen from 1000 to 100 °С and the density of the product was taken into account at the degree of decomposition of limestone 98% (=1700 kg/m3). In the preheating zone, the limiting stage is the supply of heat from the gas to the lump material, and at the same time can be taken equal to ⁓400−450 kJ/(m2∙h∙К) and τ1 is estimated as 0.8÷1 hour. The total residence time of the material in the furnace (in the heating zone and in the firing zone) is estimated at 1.4÷1.5 hours. The average speed of material movement in the cylindrical part of the furnace is estimated as 0.004 m/s, which makes it possible to consider the filtering layer conditionally stationary. These characteristics affect the quality of limestone and the uniformity of limestone firing that was the basis for the design of roasting shaft kilns using gaseous fuel.
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TAŞKINOĞLU, EZGI S., and JOSETTE BELLAN. "Subgrid-scale models and large-eddy simulation of oxygen stream disintegration and mixing with a hydrogen or helium stream at supercritical pressure." Journal of Fluid Mechanics 679 (May 11, 2011): 156–93. http://dx.doi.org/10.1017/jfm.2011.130.
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For flows at supercritical pressure, p, the large-eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equations utilize transport properties depending on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid-scale (SGS) fluxes but also new SGS terms, each denoted as a ‘correction’. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations and represent differences, other than contributed by the convection terms, between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) which is the difference between the filtered divergence of the molecular heat flux and the divergence of the molecular heat flux computed as a function of the filtered flow field. We revisit here a previous a priori study where we only had partial success in modelling the q-correction term and show that success can be achieved using a different modelling approach. This a priori analysis, based on a temporal mixing-layer direct numerical simulation database, shows that the focus in modelling the q-correction should be on reconstructing the primitive variable gradients rather than their coefficients, and proposes the approximate deconvolution model (ADM) as an effective means of flow field reconstruction for LES molecular heat-flux calculation. Furthermore, an a posteriori study is conducted for temporal mixing layers initially containing oxygen (O) in the lower stream and hydrogen (H) or helium (He) in the upper stream to examine the benefit of the new model. Results show that for any LES including SGS-flux models (constant-coefficient gradient or scale-similarity models; dynamic-coefficient Smagorinsky/Yoshizawa or mixed Smagorinsky/Yoshizawa/gradient models), the inclusion of the q-correction in LES leads to the theoretical maximum reduction of the SGS molecular heat-flux difference; the remaining error in modelling this new subgrid term is thus irreducible. The impact of the q-correction model first on the molecular heat flux and then on the mean, fluctuations, second-order correlations and spatial distribution of dependent variables is also demonstrated. Discussions on the utilization of the models in general LES are presented.
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Högberg, Charlotta, Stefan Lossow, Farahnaz Khosrawi, Ralf Bauer, Kaley A. Walker, Patrick Eriksson, Donal P. Murtagh, Gabriele P. Stiller, Jörg Steinwagner, and Qiong Zhang. "The SPARC water vapour assessment II: profile-to-profile and climatological comparisons of stratospheric <i>δ</i>D(H<sub>2</sub>O) observations from satellite." Atmospheric Chemistry and Physics 19, no. 4 (February 27, 2019): 2497–526. http://dx.doi.org/10.5194/acp-19-2497-2019.
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Abstract. Within the framework of the second SPARC (Stratosphere-troposphere Processes And their Role in Climate) water vapour assessment (WAVAS-II), we evaluated five data sets of δD(H2O) obtained from observations by Odin/SMR (Sub-Millimetre Radiometer), Envisat/MIPAS (Environmental Satellite/Michelson Interferometer for Passive Atmospheric Sounding), and SCISAT/ACE-FTS (Science Satellite/Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) using profile-to-profile and climatological comparisons. These comparisons aimed to provide a comprehensive overview of typical uncertainties in the observational database that could be considered in the future in observational and modelling studies. Our primary focus is on stratospheric altitudes, but results for the upper troposphere and lower mesosphere are also shown. There are clear quantitative differences in the measurements of the isotopic ratio, mainly with regard to comparisons between the SMR data set and both the MIPAS and ACE-FTS data sets. In the lower stratosphere, the SMR data set shows a higher depletion in δD than the MIPAS and ACE-FTS data sets. The differences maximise close to 50 hPa and exceed 200 ‰. With increasing altitude, the biases decrease. Above 4 hPa, the SMR data set shows a lower δD depletion than the MIPAS data sets, occasionally exceeding 100 ‰. Overall, the δD biases of the SMR data set are driven by HDO biases in the lower stratosphere and by H2O biases in the upper stratosphere and lower mesosphere. In between, in the middle stratosphere, the biases in δD are the result of deviations in both HDO and H2O. These biases are attributed to issues with the calibration, in particular in terms of the sideband filtering, and uncertainties in spectroscopic parameters. The MIPAS and ACE-FTS data sets agree rather well between about 100 and 10 hPa. The MIPAS data sets show less depletion below approximately 15 hPa (up to about 30 ‰), due to differences in both HDO and H2O. Higher up this behaviour is reversed, and towards the upper stratosphere the biases increase. This is driven by increasing biases in H2O, and on occasion the differences in δD exceed 80 ‰. Below 100 hPa, the differences between the MIPAS and ACE-FTS data sets are even larger. In the climatological comparisons, the MIPAS data sets continue to show less depletion in δD than the ACE-FTS data sets below 15 hPa during all seasons, with some variations in magnitude. The differences between the MIPAS and ACE-FTS data have multiple causes, such as differences in the temporal and spatial sampling (except for the profile-to-profile comparisons), cloud influence, vertical resolution, and the microwindows and spectroscopic database chosen. Differences between data sets from the same instrument are typically small in the stratosphere. Overall, if the data sets are considered together, the differences in δD among them in key areas of scientific interest (e.g. tropical and polar lower stratosphere, lower mesosphere, and upper troposphere) are too large to draw robust conclusions on atmospheric processes affecting the water vapour budget and distribution, e.g. the relative importance of different mechanisms transporting water vapour into the stratosphere.
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Bunt, Christopher M., Hugh J. Maclsaac, and W. Gary Sprules. "Pumping Rates and Projected Filtering Impacts of Juvenile Zebra Mussels (Dreissena polymorpha) in Western Lake Erie." Canadian Journal of Fisheries and Aquatic Sciences 50, no. 5 (May 1, 1993): 1017–22. http://dx.doi.org/10.1139/f93-117.
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Small-bodied (2–11 mm), settled zebra mussels (Dreissena polymorpha Pallas) comprise up to 90% of individuals inhabiting reefs in western Lake Erie. We assessed pumping rates of these size classes of D. polymorpha by injecting an inert dye into inhalant filtering currents and monitoring exhalant flows using high-resolution videography. Pumping rates ranged between 0.20 and 4.45 mL∙ind−1∙h−1 and increased in relation to mussel shell length. Based on 1990 size–frequency distributions for reefs in western Lake Erie and our pumping rate – shell length regression, small settled D. polymorpha were theoretically capable of pumping between 39 and 96% of the water column daily. Small-bodied mussels inhabiting Sunken Chicken Reef were collectively capable of processing between 110 and 400% of the values previously reported for Daphnia. Recent changes in water quality in western Lake Erie could be primarily related to zebra mussel filtering activities, including those of small-bodied individuals.
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Frigo, Elisandro Pires, Silvio Cesar Sampaio, Paulo Lorenço Freitas, Lúcia Helena Nóbrega, Reginaldo Ferreira Santos, and Larissa Schmatz Mallmann. "DESEMPENHO DO SISTEMA DE GOTEJAMENTO E DE FILTROS UTILIZANDO ÁGUA RESIDUÁRIA DA SUINOCULTURA." IRRIGA 11, no. 3 (September 14, 2006): 305–18. http://dx.doi.org/10.15809/irriga.2006v11n3p305-318.
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DESEMPENHO DO SISTEMA DE GOTEJAMENTO E DE FILTROS UTILIZANDO ÁGUA RESIDUÁRIA DA SUINOCULTURA Elisandro Pires Frigo; Silvio Cesar Sampaio; Paulo Lourenço Freitas; Lúcia Helena Nóbrega; Reginaldo Ferreira Santos; Larissa Schmatz MallmannDepartamento Recursos Hídricos e Meio Ambiente, Universidade Estadual do Oeste do Paraná, Cascavel, PR 1 RESUMO Este trabalho avaliou a uniformidade do sistema de distribuição de água de poço artesiano e de efluentes e o desempenho do sistema de filtros. O experimento foi conduzido em estufa no Núcleo Experimental de Engenharia Agrícola, pertencente à Universidade Estadual do Oeste do Paraná. O solo da área experimental é classificado como Latossolo Vermelho distroférrico típico de textura muito argilosa. A água residuária utilizada foi proveniente da suinocultura (ARS), sendo a mesma diluída em água a 0, 25, 50 e 75%. O sistema de irrigação utilizado foi por gotejamento. O delineamento experimental foi constituído de quatro tratamentos com cinco repetições, inteiramente casualizado. Para determinar o coeficiente de uniformidade do sistema, foi utilizado o modelo proposto por Christiansen (CUC). Os filtros foram avaliados em função das pressões de serviços (200, 150, 100 e 50 kPa) e das vazões. Os resultados permitiram concluir que a condutividade elétrica diminuiu 50% para os tratamentos T2 (ARS diluída a 25%) e T4 (ARS diluída a 75%) e 35,50% para o tratamento T3 (ARS diluída a 50%), após a passagem pelos filtros. O pH encontrado no experimento está de acordo com os parâmetros recomendados para aplicação de águas residuárias. Houve redução na concentração de sólidos totais para os tratamentos T2, T3 e T4, com valores médios de 35,20; 24,41 e 27,43%, respectivamente. O CUC para os tratamentos diminuiu em função da maior quantidade de sólidos e sais dissolvidos no efluente. A vazão do efluente em função das pressões de serviço diminuiu proporcionalmente com o aumento da concentração de ARS. UNITERMOS: coeficiente de uniformidade, filtragem, irrigação localizada. FRIGO, E. P.; SAMPAIO, S. C.; FREITAS, P. L.; NÓBREGA, L. H.; SANTOS, R. F.; MALLMANN, L. S. PERFORMANCE OF DRIP IRRIGATION AND FILTERS USING WASTEWATER FROM SUINOCULTURE 2 ABSTRACT This paper aimed to evaluate the uniformity coefficient of the distribution of a drip system of water and effluents and the efficiency of filter system. The experiment was conducted at greenhouse ofAgriculturalEngineeringExperimentalCenter,WestParanáStateUniversity. The soil of the experimental area is classified as typical Red Distrofferic Latosoil of very clay texture. The effluent was originating from suinoculture, diluted in 0, 25, 50 and 75% of water. The random experimental design was constituted by four treatments with five repetitions. In order to determinate the uniformity coefficient of the system, the model proposed by Christiansen (CUC) was used. The filters were evaluated in function of pressures (200, 150, 100 and 50 kPa) and several discharges. The results allowed concluding that the Electrical Conductivity decreased 50% for the treatments T2 (ARS diluted in 25%) and T4 (ARS diluted in 75%) and 35% for the treatment T3 (ARS diluted in 50%), after the passage by filters. The pH found was in accordance with the parameters recommended for the application of wastewaters. There was reduction in the concentration of Total Solids for the treatments T2, T3 and T4, with mean values of 35,20; 24,41 and 27,43%, respectively. The uniformity coefficient of Christiansen (CUC) for the treatments decreased in dependence of the higher amount of solids and dissolved salts in the effluent. The effluent discharge as a function of pressures decreased proportionally to effluent concentration decrease. KEYWORDS: uniformity coefficient, filtering, drip irrigation.
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Pinzón Ardila, Omar. "Modelado de un Recuperador Dinámico de Tensión para el Mejoramiento de la Calidad de la Onda de Tensión." BISTUA REVISTA DE LA FACULTAD DE CIENCIAS BASICAS 14, no. 1 (May 4, 2016): 62. http://dx.doi.org/10.24054/01204211.v1.n1.2016.1938.
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Knapp, Julia L. A., Colin Neal, Alessandro Schlumpf, Margaret Neal, and James W. Kirchner. "New water fractions and transit time distributions at Plynlimon, Wales, estimated from stable water isotopes in precipitation and streamflow." Hydrology and Earth System Sciences 23, no. 10 (October 28, 2019): 4367–88. http://dx.doi.org/10.5194/hess-23-4367-2019.
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Abstract. Long-term, high-frequency time series of passive tracers in precipitation and streamflow are essential for quantifying catchment transport and storage processes, but few such data sets are publicly available. Here we describe, present, and make available to the public two extensive data sets of stable water isotopes in streamflow and precipitation at the Plynlimon experimental catchments in central Wales. Stable isotope data are available at 7-hourly intervals for 17 months, and at weekly intervals for 4.25 years. Precipitation isotope values were highly variable in both data sets, and the high temporal resolution of the 7-hourly streamwater samples revealed rich isotopic dynamics that were not captured by the weekly sampling. We used ensemble hydrograph separation to calculate new water fractions and transit time distributions from both data sets. Transit time distributions estimated by ensemble hydrograph separation were broadly consistent with those estimated by spectral fitting methods, suggesting that they can reliably quantify the contributions of recent precipitation to streamflow. We found that on average, roughly 3 % of streamwater was made up of precipitation that fell within the previous 7 h, and 13 %–15 % of streamwater was made up of precipitation that fell within the previous week. The contributions of recent precipitation to streamflow were highest during large events, as illustrated by comparing new water fractions for different discharges and precipitation rates. This dependence of new water fractions on water fluxes was also reflected in their seasonal variations, with lower new water fractions and more damped catchment transit time distributions in spring and summer compared to fall and winter. We also compared new water fractions obtained from stable water isotopes against those obtained from concentrations of chloride, a solute frequently used as a passive tracer of catchment transport processes. After filtering the chloride data for dry deposition effects, we found broadly similar new water fractions using chloride and stable water isotopes, indicating that these different tracers may yield similar inferences about catchment storage and transport, if potentially confounding factors are eliminated. These stable isotope time series comprise some of the longest and most detailed publicly available catchment isotope data sets. They complement extensive solute data sets that are already publicly available for Plynlimon, enabling a wide range of future analyses of catchment behavior.
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Knepp, Travis N., James J. Szykman, Russell Long, Rachelle M. Duvall, Jonathan Krug, Melinda Beaver, Kevin Cavender, et al. "Assessment of mixed-layer height estimation from single-wavelength ceilometer profiles." Atmospheric Measurement Techniques 10, no. 10 (October 25, 2017): 3963–83. http://dx.doi.org/10.5194/amt-10-3963-2017.
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Abstract. Differing boundary/mixed-layer height measurement methods were assessed in moderately polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by impacts of local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for light detection and ranging (lidar)-based MLH intercomparisons and ceilometer-network operation, and that sonde-derived boundary layer heights are higher (10–15 % at midday) than lidar-derived mixed-layer heights. We show that averaging the retrieved MLH to 1 h resolution (an appropriate timescale for a priori data model initialization) significantly improved the correlation between differing instruments and differing algorithms.
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Xu, Qiyi, and Linshuai Ge. "Dynamic event-triggered H∞ filtering for discrete-time singular networked control system subject to cyberattacks." Transactions of the Institute of Measurement and Control, August 5, 2022, 014233122211079. http://dx.doi.org/10.1177/01423312221107989.
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This paper investigates the event-triggered filtering problem for the discrete-time singular networked control systems (DSNCS) with random cyberattacks. To more effectively utilize the limited network resource, a new dynamic event-triggered mechanism is proposed, which can effectively reduce network information transmission and save bandwidth on the premise of ensuring system performance. By considering the effect of the event-triggered mechanism and two types of cyberattacks, the filtering error system model has been constructed. Two independent random variables obeying the Bernoulli distribution are introduced to describe the two types of cyberattacks. Sufficient conditions that can guarantee the admissibility of the filtering error system have been developed with Lyapunov stability theory and LMIs techniques. Moreover, the co-design method is present in terms of LMIs to derive the parameters of dynamic event-triggered mechanism and the designed [Formula: see text] filter synchronously. Finally, an illustrative example is employed to verify the usefulness of the proposed method.
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Neumann, Sebastian Philipp, Alexander Buchner, Lukas Bulla, Martin Bohmann, and Rupert Ursin. "Continuous entanglement distribution over a transnational 248 km fiber link." Nature Communications 13, no. 1 (October 17, 2022). http://dx.doi.org/10.1038/s41467-022-33919-0.
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AbstractReliable long-distance distribution of entanglement is a key technique for many quantum applications, most notably quantum key distribution. Here, we present a continuously working, trusted-node free international link between Austria and Slovakia, directly distributing polarization-entangled photon pairs via 248 km of deployed telecommunication fiber. Despite 79 dB loss, we observe stable detected pair rates of 9 s−1 over 110 h. We mitigate multi-pair detections with strict temporal filtering, enabled by nonlocal compensation of chromatic dispersion and superconducting nanowire detectors. Fully automatized active polarization stabilization keeps the entangled state’s visibility at 86% for altogether 82 h. In a quantum cryptography context, this corresponds to an asymptotic secure key rate of 1.4 bits/s and 258 kbit of total key, considering finite-key effects. Our work paves the way for low-maintenance, ultra-stable quantum communication over long distances, independent of weather conditions and time of day, thus constituting an important step towards the quantum internet.
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Park, Jun H., N. Sri Namachchivaya, and Hoong Chieh Yeong. "Particle Filters in a Multiscale Environment: Homogenized Hybrid Particle Filter." Journal of Applied Mechanics 78, no. 6 (August 22, 2011). http://dx.doi.org/10.1115/1.4003167.
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State estimation of random dynamical systems with noisy observations has been an important problem in many areas of science and engineering. Efficient new algorithms to estimate the present and future state of a dynamic signal based upon corrupted, distorted, and possibly partial observations of the signal are required. Since the true state is usually hidden and evolves according to its own dynamics, the objective of this work is to get an optimal estimation of the true state via noisy observations. The theory of filtering provides a recursive procedure for estimating an evolving signal or state from a noisy observation process. We consider a particle filter approach for nonlinear filtering in multiscale dynamical systems. Particle filters represent the posterior conditional distribution of the state variables by a system of particles, which evolves and adapts recursively as new information becomes available. Particle filters suffer from computational inefficiency when applied to high dimensional problems. In practice, large numbers of particles may be required to provide adequate approximations in higher dimensional poblems. In several high dimensional applications, after a sequence of updates, the particle system will often collapse to a single point. With the help of rigorous dimensional reduction methods, particle filters could regain their versatility. Based on our theoretical developments (Park, J. H., Sri Namachchivaya, N., and Sowers, R. B., 2008, “A Problem in Stochastic Averaging of Nonlinear Filters,” Stochastics Dyn., 8(3), pp. 543–560; Park, J. H., Sowers, R. B., and Sri Namachchivaya, N., 2010, “Dimensional Reduction in Nonlinear Filtering,” Nonlinearity, 23(2), pp. 305–324), we devise an efficient particle filter algorithm, which is applicable to high dimensional multiscale nonlinear filtering problems. In this paper, we present the homogenized hybrid particle filtering method that combines homogenization of random dynamical systems, reduced order nonlinear filtering, and particle methods.
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Wang, Yixin, Bing Wei, and Kaihang Fan. "Analysis of Transmission Characteristics of EBG Structures by Subgridding Unconditionally Stable FETD Method." Applied Computational Electromagnetics Society Journal (ACES), February 10, 2023. http://dx.doi.org/10.13052/2022.aces.j.370901.
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Subgridding unconditionally-stable finite-element time-domain method based on spatial modes filtering (SSMF-FETD) is combined with the Floquet theorem and used to analyze the transmission characteristics of 2-D dielectric pillar-array electromagnetic bandgap (EBG) structures with cross-section shapes of square and H. The computational stress is effectively reduced by exploiting the periodicity of the EBG structure and subgridding technique. Through the spatial modes filtering (SMF) method, the subgridding FETD (S-FETD) method is developed into the SSMF-FETD with larger time steps and higher computational efficiency. The effect of geometric and electromagnetic parameters on transmission characteristics of EBG structures are analyzed and compared in detail, the conclusions are as follows: the optimal filling ratio of the dielectric square-pillar EBG structure is 0.5, the composite H-pillar EBG structure has multiple bandgaps and can effectively save metal materials while satisfying the design requirements. The effect of electromagnetic parameters can be uniformly analyzed from the perspective of the average relative permittivity; with its increase, the central frequency of the bandgap becomes lower. It should be noted that the bandgap distribution and variation of composite H-pillar EBG structure are related to how its dielectric parameters change and combine. The results can serve as a reference for similar structures design.
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Yazdkhasti, Setareh, Danial Sabzevari, and Jurek Z. Sasiadek. "Adaptive H-infinity extended Kalman filtering for a navigation system in presence of high uncertainties." Transactions of the Institute of Measurement and Control, December 9, 2022, 014233122211360. http://dx.doi.org/10.1177/01423312221136022.
Full textAbstract:
The optimal performance of the Kalman filters is highly dependent on the measurement and process noise characteristics, making the whole system unable to achieve the desired estimation in the presence of non-Gaussian mean noise distribution and high initial uncertainties. Recently, the H-infinity filter, as a robust algorithm, has been broadly used, as it is not being dependent on the pre-knowledge of the noise nature; however, making a balance between high robustness and estimation accuracy is a challenging issue. Hence, to overcome this problem, a new adaptive H-infinity extended Kalman filter (AHEKF) was designed in this paper, which benefits from both high robustness and precision. The suggested algorithm contains two adaptive sections to achieve high accuracy as well as controlling the effects of time-varying noise characteristics, high initial uncertainties, and abnormal data that can degrade the accuracy of state estimation in an integrated navigation system. The presented algorithm was used to integrate data from two independent sensors data. The simulation results for an inertial navigation system (INS)/global positioning system (GPS) sensor fusion are presented and compared with the standard H-infinity filter, extended Kalman filter (EKF), and unscented Kalman filter (UKF) to show the effectiveness of the proposed algorithm. Evaluations demonstrate that the AHEKF achieves over 50% higher accuracy and robustness, and over 2.5 times faster convergence of estimation errors than the standard H-infinity filter.