Статті в журналах: "Continuous and aperiodic sampled measurements"

1

Guo, Meng, and Dimos V. Dimarogonas. "Nonlinear consensus via continuous, sampled, and aperiodic updates." International Journal of Control 86, no. 4 (April 2013): 567–78. http://dx.doi.org/10.1080/00207179.2012.747735.

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2

Sferlazza, Antonino, Sophie Tarbouriech, and Luca Zaccarian. "State observer with Round-Robin aperiodic sampled measurements with jitter." Automatica 129 (July 2021): 109573. http://dx.doi.org/10.1016/j.automatica.2021.109573.

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3

Song, Chengcheng, Haoping Wang, and Yang Tian. "Event-triggered piecewise-continuous observer design based on system output data received from network." Transactions of the Institute of Measurement and Control 40, no. 15 (January 24, 2018): 4166–74. http://dx.doi.org/10.1177/0142331217744616.

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This paper proposes an event-triggered piecewise-continuous observer (E-PCO) that can estimate continuous-time undelayed system state using event-triggered (aperiodic) sampled and delayed system output that is received from network. The key point of this estimation method is the design of three reconstructions and an event-triggered reduced-order discrete-time Luenberger observer (E-RODL-O). First, Reconstruction I compensates for the effects of event-triggered sampling. Based on Reconstruction I, the E-RODL-O is designed for obtaining a periodic sampled delayed system state. Then, Reconstruction II makes up for the influences of time delays, which brings the periodic sampled undelayed system state. Based on this, Reconstruction III finally calculates the continuous-time undelayed system state. Through some parameters selections, the stability of E-PCO system is guaranteed. The theoretical design is applied to a networked visual servoing mobile cart system for verifying its validity.

4

Abdalmoaty, Mohamed, and Alexander Medvedev. "Continuous Time-Delay Estimation From Sampled Measurements." IFAC-PapersOnLine 56, no. 2 (2023): 6982–87. http://dx.doi.org/10.1016/j.ifacol.2023.10.534.

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5

Gong, Hang, Fangke Wu, Runzhi Liu, Xin Jin, Wei Zhou, and Xing Chu. "Event-Based Sampled-Data Average Consensus." Mathematical Problems in Engineering 2020 (July 18, 2020): 1–13. http://dx.doi.org/10.1155/2020/1586289.

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This study addresses one of the most essential distributed control problems in multiagent systems, called the average consensus issue, using a new event-triggered sampling control perspective. Although the continuous-time sampling for average consensus has provided good results currently, a systematic investigation into the continuous-time agent dynamics with sampled-data control inputs under an event-triggered mechanism is critically lacking. The problem considered in this paper can be formulated into an average consensus problem of hybrid systems. The method considers three types of control schemes, among which periodic sampling is integrant. The first scheme is a classical sampling controller reinvestigated through a lemma. The second scheme realizes aperiodic control update as well as periodic communication, while the third scheme achieves both aspects aperiodically. Corresponding sufficient conditions of the aforementioned three schemes are derived such that the asymptotic stability of systems is ensured by using algebraic graph theory, matrix analysis, and Lyapunov theory. The constraints for the allowed sampling period, event parameter, and maximum eigenvalue of graph Laplacian are explicitly derived. Moreover, the potential Zeno behavior of agents due to the sampling control theory is avoided. Thus, a digitally implementable technique is provided. Finally, some numerical examples are provided to verify the effectiveness of the proposed theoretical analysis.

6

Liu, Zhi-Wei, Zhi-Hong Guan, Xuemin Shen, and Gang Feng. "Consensus of Multi-Agent Networks With Aperiodic Sampled Communication Via Impulsive Algorithms Using Position-Only Measurements." IEEE Transactions on Automatic Control 57, no. 10 (October 2012): 2639–43. http://dx.doi.org/10.1109/tac.2012.2214451.

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7

Shi, P. "H filtering for linear continuous-time systems with sampled measurements." IMA Journal of Mathematical Control and Information 15, no. 4 (December 1, 1998): 349–62. http://dx.doi.org/10.1093/imamci/15.4.349.

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8

Shi, Peng, Youyi Wang, and Lihua Xie. "Robust Filtering for Interconnected Uncertain Systems Under Sampled Measurements." Journal of Dynamic Systems, Measurement, and Control 119, no. 2 (June 1, 1997): 337–40. http://dx.doi.org/10.1115/1.2801261.

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This paper presents the results of robust filtering for a class of interconnected uncertain systems under sampled measurements. We address the problem of designing filters, using sampled measurements, which would guarantee a prescribed H∞ performance in the continuous-time context, irrespective of the parameter uncertainty and unknown initial states. Both the cases of finite and infinite horizon filtering are investigated in terms of N pairs of Riccati equations with finite discrete jumps.

9

Dinh, Thach Ngoc, Vincent Andrieu, Madiha Nadri, and Ulysse Serres. "Continuous-Discrete Time Observer Design for Lipschitz Systems With Sampled Measurements." IEEE Transactions on Automatic Control 60, no. 3 (March 2015): 787–92. http://dx.doi.org/10.1109/tac.2014.2329211.

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10

Shi, Peng. "Control of continuous-time systems with discrete jumps." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 41, no. 1 (July 1999): 58–82. http://dx.doi.org/10.1017/s0334270000011036.

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AbstractIn this paper, the design of output feedback controllers for linear systems under sampled measurements is investigated. The performance we use is the worst-case gain from disturbances to the controlled output, which comprises both a continuous-time and a discretetime signal to be controlled. Control problems in both the finite and infinite horizonare addressed. Necessary and sufficient conditions for the existence of a suitable sampled-data output feedback controller are given in terms of two Riccati differential equations with finite discrete jumps. A numerical example is given to show the potential of the proposed technique.

11

Lien, Chang-Hua, Yi-You Hou, Ker-Weu Yu, and Hao-Chin Chang. "Aperiodic sampled-data robust H ∞ control of uncertain continuous switched time-delay systems with novel synchronous switching signal selection." International Journal of Systems Science 51, no. 11 (June 26, 2020): 2005–24. http://dx.doi.org/10.1080/00207721.2020.1783022.

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12

Ahmed-Ali, Tarek, Vincent Van Assche, Jean-François Massieu, and Philippe Dorleans. "Continuous-Discrete Observer for State Affine Systems With Sampled and Delayed Measurements." IEEE Transactions on Automatic Control 58, no. 4 (April 2013): 1085–91. http://dx.doi.org/10.1109/tac.2012.2225555.

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13

Zhang, Daoyuan, Yanjun Shen, and Xiaohua Xia. "Continuous observer design for nonlinear systems with sampled and delayed output measurements." IFAC Proceedings Volumes 47, no. 3 (2014): 269–74. http://dx.doi.org/10.3182/20140824-6-za-1003.00819.

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14

Zhao, Guanglei, and Changchun Hua. "Continuous–discrete-time adaptive observers for nonlinear systems with sampled output measurements." International Journal of Systems Science 48, no. 12 (May 12, 2017): 2599–609. http://dx.doi.org/10.1080/00207721.2017.1324924.

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15

Kopecký, Miloš, Jiří Kub, Jan Fábry, and Zbyněk Šourek. "Aperiodic atomic ordering in PMN recovered from the anomalous x-ray scattering." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1758. http://dx.doi.org/10.1107/s2053273314082412.

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Various imaging techniques with atomic resolutions have been developed to study 3D arrangement of atoms in sub-nanometer and nanometer scale. The method presented is based on the measurement of the anomalous portion of x-ray scattering in large volume of the reciprocal space. It can be shown that, by analogy to x-ray holography with atomic resolution, the anomalous diffuse scattering provides information on both the amplitude and the phase of the scattered wave. The sample was PbMg1/3Nb2/3O3 (PMN), which belongs to relaxor ferroelectrics. Although the short and intermediate range chemical ordering is responsible for its relaxor behaviour, the real arrangement of cations remains unclear so far. The intensities of x-ray scattering in a large 3D volume of the reciprocal space were measured using an intense x-ray radiation generated by the synchrotron facility. Anomalous x-ray scattering has been obtained as a difference of intensity maps collected at two energies. The energy E1 just below the Nb K absorption edge was chosen in order to get a strong anomalous component in the scattering from Nb atoms. The data acquired at the energy E2 far from the absorption edge were used as the reference. The measured 3D pattern of anomalous scattering, including both discrete diffraction peaks and continuous x-ray diffuse scattering, allows us to reconstruct numerically an average environment around Nb atoms. The reconstructed real-space images clearly show a systematic local ordering of Mg2+ and Nb5+ cations. This ordering is more significant close to the central reference Nb atom but it is still apparent at the distance of about 3 nm giving thus an idea on the average size of ordered regions. More distant sites are occupied randomly with probabilities of occurrence of Mg2+ and Nb5+ cations given by their relative fraction in the sample. It is possible to determine conditioned probabilities of site occupancies by the given type of atom provided that the central site is occupied by Nb and to get information on the structure model of the ordered regions in the crystal.

16

Haszpra, László, and Ernő Prácser. "Uncertainty of hourly-average concentration values derived from non-continuous measurements." Atmospheric Measurement Techniques 14, no. 5 (May 18, 2021): 3561–71. http://dx.doi.org/10.5194/amt-14-3561-2021.

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Abstract. Continental greenhouse gas monitoring networks extensively use tall towers for higher spatial representativeness. In most cases, several intakes are built along the tower to give information also on the vertical concentration profile of the components considered. Typically, a single gas analyzer is used, and the intake points are sequentially connected to the instrument. It involves that the continuous concentration signal is only sampled for discrete short periods at each intake point, which does not allow for a perfect reconstruction of the original concentration variation. It increases the uncertainty of the calculated hourly averages usually used by the atmospheric transport and budget models. The purpose of the study is to give the data users an impression of the potential magnitude of this kind of uncertainty, as well as how it depends on the number of intakes sampled, on the length of the sampling period at each intake, on the season, and on the time of the day. It presents how much improvement can be achieved using linear or spline interpolation between the measurement periods instead of the simple arithmetic averaging of the available measurements. Although the results presented here may be site-specific, the study calls attention to the potentially rather heterogeneous spatial and temporal distribution of the uncertainty of the hourly-average concentration values derived from tall-tower measurements applying sequential sampling.

17

Zhang, Huichai, Michael V. Basin, and Mikhail Skliar. "Itô–Volterra Optimal State Estimation With Continuous, Multirate, Randomly Sampled, and Delayed Measurements." IEEE Transactions on Automatic Control 52, no. 3 (March 2007): 401–16. http://dx.doi.org/10.1109/tac.2007.892383.

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18

Zisser, Howard C., Timothy S. Bailey, Sherwyn Schwartz, Robert E. Ratner, and Jonathan Wise. "Accuracy of the SEVEN® Continuous Glucose Monitoring System: Comparison with Frequently Sampled Venous Glucose Measurements." Journal of Diabetes Science and Technology 3, no. 5 (September 2009): 1146–54. http://dx.doi.org/10.1177/193229680900300519.

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Background: The purpose of this study was to compare the accuracy of measurements obtained from the DexCom™ SEVEN® system with Yellow Springs Instrument (YSI) laboratory measurements of venous blood glucose. Methods: Seventy-two subjects with insulin-requiring diabetes, aged 18–71, were enrolled in a multicenter, prospective single-arm study. All participants wore the SEVEN continuous glucose monitoring (CGM) system for one, 7-day wear period. Calibration with capillary finger stick measurements was performed 2 hours after sensor insertion and once every 12 hours thereafter. A subset of subjects (28) wore two systems simultaneously to assess precision. All subjects participated in one, 10-hour in-clinic session on day 1, 4, or 7 of the study to compare CGM measurements against a laboratory method (YSI analyzer) using venous measurements taken once every 20 minutes. Carbohydrate consumption and insulin dosing were adjusted in order to obtain a broad range of glucose values. Results: Comparison of CGM measurements with the laboratory reference method ( n = 2318) gave mean and median absolute relative differences (ARDs) of 16.7 and 13.2%, respectively. The percentage was 70.4% in the clinically accurate Clarke error grid A zone and 27.5% in the benign error B zone. Performance of the SEVEN system was consistent over time with mean and median ARD lowest on day 7 as compared to YSI (13.3 and 10.2%, respectively). Average sensor time lag was 5 minutes. Conclusions: Measurements of the DexCom SEVEN system were found to be consistent and accurate compared with venous measurements made using a laboratory reference method over 7 days of wear.

19

Mohammed, Abdeldafia M., Haoping Wang, and Yang Tian. "State observer for linear system with unknown input disturbance and sampled and delayed output with measurement noise." Transactions of the Institute of Measurement and Control 41, no. 3 (May 23, 2018): 749–59. http://dx.doi.org/10.1177/0142331218770710.

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This paper addresses the sampled and unknown time-varying delayed output problem of the continuous-time linear system with unknown input disturbance and measurement noise. Based on the piecewise continuous hybrid system and extended functional observer, a robust hybrid extended observer is proposed to estimate the non-delayed continuous state from the sampled and delayed measurements when the time delay is unknown time-varying. The advantages of the designed observer are the quite simple structure, robustness to dealing with measurement noise, and ability to estimate the system state with accuracy under the influence of unknown input disturbance. Furthermore, the proposed observer is able to estimate the non-delayed continuous state and unknown input disturbance, in particular for the issue of fault estimation and perturbation disturbance simultaneously. The stability of the robust hybrid extended observer is illustrated and analyzed. Moreover, to show the effectiveness of the proposed observer, a comparison with the delayed Luenberger observer is performed via a numerical example. Finally, the simulation results are demonstrated.

20

Mohammed, Abdeldafia, Haoping Wang, and Yang Tian. "New Piecewise Estimator Observer for Continuous Time Linear Systems with Sampled and Delayed Measurements." Arabian Journal for Science and Engineering 44, no. 8 (January 2, 2019): 7249–60. http://dx.doi.org/10.1007/s13369-018-03697-3.

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21

Shen, Yanjun, Daoyuan Zhang, and Xiaohua Xia. "Continuous output feedback stabilization for nonlinear systems based on sampled and delayed output measurements." International Journal of Robust and Nonlinear Control 26, no. 14 (December 8, 2015): 3075–87. http://dx.doi.org/10.1002/rnc.3491.

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22

Kamenshchikov, Mikhail. "Design of unbiased reduced order filter for stochastic systems with sampled measurements." Journal of Physics: Conference Series 2701, no. 1 (February 1, 2024): 012030. http://dx.doi.org/10.1088/1742-6596/2701/1/012030.

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Abstract The problem of synthesizing reduced order filter, that forms an unbiased estimate of linear functional from an unknown phase vector of a continuous time stochastic system with sampled measurements and additive noises, is considered in this work. The H 2 norm of the weighted transfer function from input noises to estimation error is used as a performance criterion. The method for reduced order filter design is based on the expression of the explicit dependence of performance criterion on unknown parameters in the canonical basis and the application of the non-convex optimization technique. Numerical simulations are performed to illustrate the proposed approach.

23

Cruickshank, Matthew, and Graham Doig. "Application of Kriging to Motorsport Aerodynamic Analysis." Applied Mechanics and Materials 553 (May 2014): 217–22. http://dx.doi.org/10.4028/www.scientific.net/amm.553.217.

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Aerodynamic analysis in motorsport is conducted using three methods, computational, scaled experimental and full-scale operational. However, the varying fidelity, different sampling resolutions and unavoidable errors of each technique make valid comparisons between datasets from each method difficult and time consuming. Kriging is a geostatistical method to estimate values within a data field by examining and applying the trends of the dataset. This research examines how such techniques can be used to aid comparison between aerodynamic measurements of a race car. It examines how kriging can be used to transform discrete measurements, of varying fidelity and sampling resolution, into semi-continuous measurements, thus allowing computational results to be compared across a wider range of conditions than initially tested. This work explores how kriging can allow the trends from highly sampled data, such as track running, to be applied to less sampled data, such as CFD to improve computational and overall aerodynamic analysis.

24

Zhang, Changzhu, Qijun Chen та Jianbin Qiu. "Robust ℋ∞ filtering for vehicle sideslip angle estimation with sampled-data measurements". Transactions of the Institute of Measurement and Control 39, № 7 (15 лютого 2016): 1059–70. http://dx.doi.org/10.1177/0142331215627001.

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In this paper, the problem of vehicle sideslip angle estimation is studied based on a single-track model, and an approach to robust ℋ∞ filter design with sampled-data measurements is proposed. Considering the changes of the vehicle mass, the moment of inertia about the yaw axis and the nonlinear relationships between the road surface and tyres, the vehicle lateral dynamics are characterized by a system with parameter uncertainties, which belong to a given convex polytope. By utilizing an input delay approach, the filtering error system is transformed into a continuous-time system with time delay in the state. By introducing a Lyapunov–Krasovskii functional and a free weighting matrix technique, LMI-based conditions have been formulated for the stability analysis of the filtering error system and the existence of admissible filters, which ensure the filtering error system is asymptotically stable with a prescribed ℋ∞ disturbance attenuation level. Finally, some simulation results are provided to illustrate the effectiveness of the proposed method.

25

Cuffney, Thomas F., and J. Bruce Wallace. "Particulate Organic Matter Export from Three Headwater Streams: Discrete versus Continuous Measurements." Canadian Journal of Fisheries and Aquatic Sciences 45, no. 11 (November 1, 1988): 2010–16. http://dx.doi.org/10.1139/f88-234.

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Particulate organic matter (POM) export from three small headwater streams of the southern Appalachian Mountains was estimated using continuous and discrete (grab) measurement methods for 2 yr. Total annual POM export estimated from continuous measurements was always greater (28–68 kg ash-free dry mass (AFDM)) than estimates (8–44 kg AFDM) made from discrete measurements (i.e. POM concentration × total discharge). Continuous export samples were collected using a weir and gaging flume connected to a Coshocton proportional sampler designed to deliver 0.6% of discharge into a series of three settling barrels. The settling barrels removed a consistent proportion of POM (85–87%). The proportion of stream flow sampled by the Coshocton samplers was constant for each of the samplers (range 0.53–0.6%). The constant extraction efficiencies and proportional sampling of discharge allowed for the calculation of total export independent of discharge measurements (i.e. total export = amount in barrels ÷ extraction efficiency ÷ Coshocton percentage). The inability of the discrete method to adequately sample storm and bedload transport accounts for the underestimates of total annual export. This underestimation has important implications for studies which use discrete measurements to estimate POM export.

26

Bastrikov, V., H. C. Steen-Larsen, V. Masson-Delmotte, K. Gribanov, O. Cattani, J. Jouzel, and V. Zakharov. "Continuous measurements of atmospheric water vapour isotopes in Western Siberia (Kourovka)." Atmospheric Measurement Techniques Discussions 7, no. 1 (January 21, 2014): 475–507. http://dx.doi.org/10.5194/amtd-7-475-2014.

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Abstract. The isotopic composition of atmospheric water vapour at the land surface has been continuously monitored at the Kourovka astronomical observatory in Western Siberia (57.037° N, 59.547° E, 300 m a.s.l.) since April 2012. These measurements provide the first record of δD, δ18O and d-excess in this region. Air was sampled at 8 m height within a forest clearing. Measurements were made with a Wavelength-Scanned Cavity Ring Down Spectroscopy analyzer. A specific protocol was developed for calibration and drift corrections with a particular enhancement to ensure reliable measurements at low humidity during winter. The isotopic measurements conducted till August 2013 exhibit a clear seasonal cycle with maximum δD and δ18O values in summer and minimum values in winter. In addition, considerable synoptic timescale variability of isotopic composition was observed with typical variations of 50–100‰ for δD, 10–15‰ for δ18O and 2–8‰ for d-excess. The strong correlations between δD and local meteorological parameters (logarithm-of-humidity and temperature) are explored, with a lack of dependency in summer that points to the importance of continental recycling and local evapotranspiration. The overall correlation between δD and temperature is associated with a slope of 3‰ °C−1. Large d-excess diurnal variability was observed during summer with up to 30‰ depletion during the night and the minima manifested shortly after sunrise. The accuracy of the isotopic measurements was quantified as 1.4–11.2‰ for δD and 0.23–1.84‰ for δ18O depending on the humidity.

27

Bernier, Pierre Y. "Extrapolating Snow Measurements on the Marmot Creek Experimental Basin." Hydrology Research 17, no. 2 (April 1, 1986): 83–92. http://dx.doi.org/10.2166/nh.1986.0006.

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From 1969 to 1980, each March, snow depth and water equivalent were sampled around 249 pins of a grid covering the forested portion of Marmot Creek basin. Continuous record from four snow pillows and monthly data from six snow courses were used to extrapolate the spatially intensive grid data to other winter months. Snow courses were better estimators of grid data than snow pillows. Readings from about 80 % of the pins were correlated to the data from one or the other snow pillows with r2 above 0.70. The ability of a snow course to track the year-to-year variations in the March data of individual pins of the grid was not related to similarities in elevation or aspects between the course and the pins.

28

Tong, Shan, and Pengcheng Shi. "Sampled-Data Filtering Framework for Cardiac Motion Recovery: Optimal Estimation of Continuous Dynamics From Discrete Measurements." IEEE Transactions on Biomedical Engineering 54, no. 10 (October 2007): 1750–61. http://dx.doi.org/10.1109/tbme.2007.895106.

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29

Nawal, Mayur, Bharath Shekar, and Priyank Jaiswal. "Integration of sparse and continuous data sets using machine learning for core mineralogy interpretation." Leading Edge 42, no. 6 (June 2023): 421–32. http://dx.doi.org/10.1190/tle42060421.1.

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In earth science, integrating noninvasive continuous data streams with discrete invasive measurements remains an open challenge. We address such a problem — that of predicting whole-core mineralogy using discrete measurements with the help of machine learning. Our targets are sparsely sampled mineralogy from X-ray diffraction, and features are continually sampled elemental oxides from X-ray fluorescence. Both data sets are acquired on a core cut from a Mississippian-age mixed siliciclastic-carbonate formation in the U.S. midcontinent. The novelty lies in predicting multiple classes of output targets from input features in a small multidimensional data setting. Our workflow has three salient aspects. First, it shows how single-output models are more effective in relating selective target-feature subsets than using a multi-output model for simultaneously relating the entire target-feature set. Specifically, we adopt a competitive ensemble strategy comprising three classes of regression algorithms — elastic net (linear regression), XGBoost (tree-based), and feedforward neural networks (nonlinear regression). Second, it shows that feature selection and engineering, when done using statistical relationships within the data set and domain knowledge, can significantly improve target predictability. Third, it incorporates k-fold cross-validation and grid-search-based parameter tuning to predict targets within 4%–6% accuracy using 40% training data. Results open doors to generating a wealth of information in energy, environmental, and climate sciences where remotely sensed data are inexpensive and abundant but physical sampling may be limited due to analytic, logistic, or economic issues.

30

Browne, Damien C., and Lindsay Kleeman. "A sonar ring with continuous matched filtering and dynamically switched templates." Robotica 30, no. 6 (October 24, 2011): 891–912. http://dx.doi.org/10.1017/s0263574711001093.

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SUMMARYMatched filtering optimally estimates the arrival time for a sonar sensor by correlating received signals with templates. This paper presents a sonar ring with continuous matched filtering on 48 receiver channels sampled at 500kHz. The design dynamically switches the matched filter templates to account for pulse shape variations with range. To achieve real-time, low-latency and optimal performance, processing is implemented on an field-programmable gate array (FPGA) transmitting sonar pulses (2 periods of a 45kHz sine wave) at repetition rate of 30-Hz to 5.7-m range. The paper describes the removal of secondary peaks of the correlation output of matched filtering and template selection. Results include sonar maps, accuracy measurements and localization of weak targets.

31

Bastrikov, V., H. C. Steen-Larsen, V. Masson-Delmotte, K. Gribanov, O. Cattani, J. Jouzel, and V. Zakharov. "Continuous measurements of atmospheric water vapour isotopes in western Siberia (Kourovka)." Atmospheric Measurement Techniques 7, no. 6 (June 18, 2014): 1763–76. http://dx.doi.org/10.5194/amt-7-1763-2014.

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Abstract. The isotopic composition of atmospheric water vapour at the land surface has been continuously monitored at the Kourovka astronomical observatory in western Siberia (57.037° N, 59.547° E; 300 m a.s.l.) since April 2012. These measurements provide the first record of δD, δ18O and d-excess in this region. Air was sampled at 8 m height within a forest clearing. Measurements were made with a wavelength-scanned cavity ring-down spectroscopy analyzer (Picarro L2130-i). Specific improvements of the measurement system and calibration protocol have been made to ensure reliable measurements at low humidity during winter. The isotopic measurements conducted till August 2013 exhibit a clear seasonal cycle with maximum δD and δ18O values in summer and minimum values in winter. In addition, considerable synoptic timescale variability of isotopic composition was observed with typical variations of 50–100‰ for δD, 10–15‰ for δ18O and 2–8‰ for d-excess. The strong correlations between δD and local meteorological parameters (logarithm of humidity and temperature) are explored, with a lack of dependency in summer that points to the importance of continental recycling and local evapotranspiration. The overall correlation between δD and temperature is associated with a slope of 3‰ °C−1. Large d-excess diurnal variability was observed during summer with up to 30‰ decrease during the night and the minima manifested shortly after sunrise. Two dominant diurnal cycle patterns for d-excess differing by the magnitude of the d-excess decrease (21‰ and 7‰) and associated patterns for meteorological observations have been determined. The total uncertainty of the isotopic measurements was quantified as 1.4–11.2‰ for δD, 0.23–1.84‰ for δ18O and 2.3–18.5‰ for d-excess depending on the humidity.

32

Chen, H., J. Winderlich, C. Gerbig, K. Katrynski, A. Jordan, and M. Heimann. "Validation of routine continuous airborne CO2 observations near the Bialystok Tall Tower." Atmospheric Measurement Techniques 5, no. 4 (April 27, 2012): 873–89. http://dx.doi.org/10.5194/amt-5-873-2012.

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Abstract. Since 2002 in situ airborne measurements of atmospheric CO2 mixing ratios have been performed regularly aboard a rental aircraft near Bialystok (53°08´ N, 23°09´ E), a city in northeastern Poland. Since August 2008, the in situ CO2 measurements have been made by a modified commercially available and fully automated non-dispersive infrared (NDIR) analyzer system. The response of the analyzer has been characterized and the CO2 mixing ratio stability of the associated calibration system has been fully tested, which results in an optimal calibration strategy and allows for an accuracy of the CO2 measurements within 0.2 ppm. Besides the in situ measurements, air samples have been collected in glass flasks and analyzed in the laboratory for CO2 and other trace gases. To validate the in situ CO2 measurements against reliable discrete flask measurements, we developed weighting functions that mimic the temporal averaging of the flask sampling process. Comparisons between in situ and flask CO2 measurements demonstrate that these weighting functions can compensate for atmospheric variability, and provide an effective method for validating airborne in situ CO2 measurements. In addition, we show the nine-year records of flask CO2 measurements. The new system, automated since August 2008, has eliminated the need for manual in-flight calibrations, and thus enables an additional vertical profile, 20 km away, to be sampled at no additional cost in terms of flight hours. This sampling strategy provides an opportunity to investigate both temporal and spatial variability on a regular basis.

33

Taylor, N. F., D. R. Collins, C. W. Spencer, D. H. Lowenthal, B. Zielinska, V. Samburova, and N. Kumar. "Measurement of ambient aerosol hydration state at Great Smoky Mountains National Park in the Southeastern United States." Atmospheric Chemistry and Physics Discussions 11, no. 8 (August 4, 2011): 21877–933. http://dx.doi.org/10.5194/acpd-11-21877-2011.

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Abstract. We present results from two field deployments of a unique tandem differential mobility analyzer (TDMA) configuration with two primary capabilities: identifying alternative stable or meta-stable ambient aerosol hydration states associated with hysteresis in aerosol hydration behavior and determining the actual Ambient hydration State (AS-TDMA). This data set is the first to fully classify the ambient hydration state of aerosols despite recognition that hydration state significantly impacts the roles of aerosols in climate, visibility and heterogeneous chemistry. The AS-TDMA was installed at a site in eastern Tennessee on the border of Great Smoky Mountains National Park for projects during the summer of 2006 and winter of 2007–2008. During the summer, 12 % of the aerosols sampled in continuous AS-TDMA measurements were found to posses two possible hydration states under ambient conditions. In every case, the more hydrated of the possible states was occupied. The remaining 88 % did not posses multiple possible states. In continuous measurements during the winter, 49 % of the aerosols sampled possessed two possible ambient hydration states; the remainder possessed only one. Of those aerosols with multiple possible ambient hydration states, 65 % occupied the more hydrated state; 35 % occupied the less hydrated state. This seasonal contrast is supported by differences in the fine particulate (PM2.5) composition and ambient RH as measured during the two study periods. In addition to seasonal summaries, this work includes case studies depicting the variation of hydration state with changing atmospheric conditions.

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Taylor, N. F., D. R. Collins, C. W. Spencer, D. H. Lowenthal, B. Zielinska, V. Samburova, and N. Kumar. "Measurement of ambient aerosol hydration state at Great Smoky Mountains National Park in the southeastern United States." Atmospheric Chemistry and Physics 11, no. 23 (December 7, 2011): 12085–107. http://dx.doi.org/10.5194/acp-11-12085-2011.

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Abstract. We present results from two field deployments of a unique tandem differential mobility analyzer (TDMA) configuration with two primary capabilities: identifying alternative stable or meta-stable ambient aerosol hydration states associated with hysteresis in aerosol hydration behavior and determining the actual Ambient hydration State (AS-TDMA). This data set is the first to fully classify the ambient hydration state of aerosols despite recognition that hydration state significantly impacts the roles of aerosols in climate, visibility and heterogeneous chemistry. The AS-TDMA was installed at a site in eastern Tennessee on the border of Great Smoky Mountains National Park for projects during the summer of 2006 and winter of 2007–2008. During the summer, 12% of the aerosols sampled in continuous AS-TDMA measurements were found to posses two possible hydration states under ambient conditions. In every case, the more hydrated of the possible states was occupied. The remaining 88% did not posses multiple possible states. In continuous measurements during the winter, 49% of the aerosols sampled possessed two possible ambient hydration states; the remainder possessed only one. Of those aerosols with multiple possible ambient hydration states, 65% occupied the more hydrated state; 35% occupied the less hydrated state. This seasonal contrast is supported by differences in the fine particulate (PM2.5) composition and ambient RH as measured during the two study periods. In addition to seasonal summaries, this work includes case studies depicting the variation of hydration state with changing atmospheric conditions.

35

Liaquat, Muwahida, and Mohammad Bilal Malik. "Sampled data output regulation of n-link robotic manipulator using a realizable reconstruction filter." Robotica 34, no. 4 (August 13, 2014): 900–912. http://dx.doi.org/10.1017/s0263574714001933.

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SUMMARYThis paper proposes a solution to the sampled-data regulation problem for feedback linearizable n-link robotic manipulators. The prime focus is on the development and stability analysis of the proposed control scheme in the presence of model uncertainties and external disturbances. A major constraint is the availability of sampled measurements of output signal. This leads to designing an impulsive observer for feedback linearization. The discrete-time control input is mapped into its continuous-time counterpart using a realizable reconstruction filter (RRF). The underlying control scheme relies on the sampled-data regulator theory based on the discrete-time equivalence of the plant and RRF modeled as impulsive system. This method leads to controller/observer design in discrete time. The working of the entire scheme is dependent on the stability of impulsive observer; hence a Lyapunov-based stability analysis is also included to ensure the stability of a closed-loop system. The working of the proposed scheme along with a comparison with conventional solution is presented, when applied to the control of a 3-degree-of-freedom PUMA 560 robot.

36

Shlomi, Shahar, Avi Ostfeld, Hillel Rubin, and Christine Shoemaker. "Optimal groundwater contamination monitoring using pumping wells." Water Science and Technology 62, no. 3 (August 1, 2010): 556–69. http://dx.doi.org/10.2166/wst.2010.318.

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This study presents a new method for selecting monitoring wells for optimal evaluation of groundwater quality. The basic approach of this work is motivated by difficulties in interpolating groundwater quality from information collected for only few sampled wells. The well selection relies on other existing data relevant to contaminant distribution in the sampling domain, e.g. predictions of models which rely on past measurements. The objective of this study is to develop a method of selecting the optimal wells, from which measurements could best serve some external model, e.g. a kriging system for characterizing the entire plume distribution, a flow-and-transport model for predicting a future distribution, or an inverse model for locating contaminant sources or estimating aquifer parameters. The decision variable at each sampling round determines the specific wells to be sampled. The study objective is accomplished through a spatially-continuous utility density function (UDF) which describes the utility of sampling at every point. The entire methodology which utilizes the UDF in conjunction with a sampling algorithm is entitled the UDF method. By applying calculations in steady and unsteady state sampling domains the effectiveness of the UDF method is demonstrated.

37

Marschall, Irmtraud, Nathalie Kölbl, Harald Harmuth, and Guangmin Xia. "Investigation of Continuous Casting Slag Films Sampled on Site and Comparison with Laboratory Results." Journal for Manufacturing Science & Production 13, no. 1-2 (April 17, 2013): 103–14. http://dx.doi.org/10.1515/jmsp-2012-0021.

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AbstractSlag film samples together with their associated mold fluxes were collected after service during tail out at the voestalpine Stahl GmbH continuous casting machine. The slag films were obtained after casting steel grades different in Al or Ti content and mineralogically investigated. Three distinctive layers could be determined within the slag films. A so called glassy layer, a crystalline layer and a layer, which has been liquid during casting and solidified afterwars, could be observed. Cuspidine (Ca4Si2O7F2) is the prevailing crystal phase in the crystalline layer. Casting alloyed steel grades the structure of the crystalline layer will be modified. With increasing Al2O3 content of the slag, due to interactions with the steel, nepheline ((Na,K)AlSiO4) was formed besides cuspidine. Here the distinctive needle like shaped cuspidine is remarkable. With casting steel grades with even more elevated Al content, the slag composition shows a strong decrease of silica and an increase of alumina. Therefore no longer cuspidine but fluorite (CaF2) and a so far unknown phase rich in alumina are the main crystal phases. When casting steel grades with increased Ti content, perovskite (CaTiO3) will be formed additionally to cuspidine in the crystalline layer.In addition quench tests of the original mold powders as well as DTA and viscosity measurements of the original mold powder and the slag films were performed. The methods revealed the impact of the Al2O3 and TiO2 pick-up on the crystallization temperature, the phase composition and the viscosity.

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Al – Tahir, Ali Abdul Razzaq. "Sensorless online measurements: application to variable speed drive systems." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 37, no. 1 (January 2, 2018): 29–53. http://dx.doi.org/10.1108/compel-10-2016-0453.

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Purpose Sensorless online measurements, application of variable speed drives has been given a great attention, especially over the past few years. In most of the previous literates dealing with permanent magnet synchronous motor (PMSM) drives, the combination of inter-sampled behavior with high gain design approach has not been discussed yet. This paper aims to discuss this feature in-depth. Design/methodology/approach The study contains a different approach for an observer running with surface-mounted permanent magnet synchronous machine drives to implement sensorless control. Design of sampled data observer methodology for one kind of AC machine having non-linear model and backed by an elegant formal stability convergence analysis using the tools of Lyapunov stability techniques was highly recommended in scientific contributions, and it is yet needed to be solved. Findings In this study, a solution to observation problem is covered and developed by combining ideas from the high-gain design approach and inter-sample predictor based on stator voltage measurements. The output state currents are accessible only at the sampling instant to solve the problem of states observation at continuous-time mode. This allows to reducing the usage of online appliances, improving reliability of control design and saving costs. Practical implications The proposed observer is capable of guaranteeing an acceptable closed loop dynamic response over a wide range of operation region and industrial process for random initial conditions. Originality/value The output state predictor has been interred in constructing the innovation correct term to prove the robustness of the proposed observer against attenuated sampling interval. To validate the theoretical results introduced by the main fundamental theorem and prove the observer stability convergence, the proposed observer is demonstrated through a sample study application to variable speed permanent magnet synchronous machine drive.

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Chen, H., J. Winderlich, C. Gerbig, K. Katrynski, A. Jordan, and M. Heimann. "Validation of routine continuous airborne CO2 observations near the Bialystok Tall Tower." Atmospheric Measurement Techniques Discussions 4, no. 6 (November 23, 2011): 6987–7034. http://dx.doi.org/10.5194/amtd-4-6987-2011.

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Abstract. Since 2002 in situ airborne measurements of atmospheric CO2 mixing ratios have been performed regularly aboard a rental aircraft near Bialystok (53°08' N, 23°09' E), a city in northeastern Poland. Since August 2008, the in situ CO2 measurements have been made by a modified commercially available and fully automated non-dispersive infrared (NDIR) analyzer system. The response of the analyzer has been characterized and the CO2 mixing ratio stability of the associated calibration system has been fully tested, which results in an optimal calibration strategy and allows for an accuracy of the CO2 measurements within 0.2 ppm. Besides the in situ measurements, air samples have been collected in glass flasks and analyzed in the laboratory for mixing ratios of CO2, CO, CH4, N2O, H2, SF6 and for isotopic ratios of δ13C and δ18O in CO2. To validate the in situ CO2 measurements against reliable discrete flask measurements, we developed weighting functions that mimic the temporal averaging of the flask sampling process. Comparisons between in situ and flask CO2 measurements demonstrate that these weighting functions can compensate for atmospheric variability, and provide an effective method for validating airborne in situ CO2 measurements. In addition, we show the nine-year records of flask CO2 measurements, from which the CO2 increase rates are computed for the 300 m level (1.59 ± 0.21 ppm yr−1) and for the 2500 m level (1.77 ± 0.08 ppm yr−1). The new system, automated since August 2008, has eliminated the need for manual in-flight calibrations, and thus enables an additional vertical profile, 20 km away, to be sampled at no additional cost in terms of flight hours. This sampling strategy provides an opportunity to investigate both temporal and spatial variability on a regular basis.

40

Hernández-González, Omar, Felipe Ramírez-Rasgado, Mondher Farza, María-Eusebia Guerrero-Sánchez, Carlos-Manuel Astorga-Zaragoza, Mohammed M’Saad, and Guillermo Valencia-Palomo. "Observer for Nonlinear Systems with Time-Varying Delays: Application to a Two-Degrees-of-Freedom Helicopter." Aerospace 11, no. 3 (March 6, 2024): 206. http://dx.doi.org/10.3390/aerospace11030206.

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This paper deals with the problem of the estimation of non-uniformly nonlinear systems with time-varying delays in the state and input. In addition, the problem of the sampled output measurement is also been addressed. Thus, an observer design for a class of uncertain, non-uniformly nonlinear systems in the presence of time-varying delay is proposed. A continuous–discrete observer based on a high-gain approach is designed to achieve undelayed estimation. Thus, sufficient conditions to ensure the convergence of the observer are obtained. The analysis is based on a Lyapunov–Krasovskii functional, which shows that the bounded observation error depends on the sizes of the known upper delay and the upper sampling rate. The performance of the proposed algorithm is evaluated by considering a control-based observer for a two-degrees-of-freedom helicopter system with a known time-varying delay and sampled output measurements.

41

Shen, Yanjun, Daoyuan Zhang, and Xiaohua Xia. "Continuous observer design for a class of multi-output nonlinear systems with multi-rate sampled and delayed output measurements." Automatica 75 (January 2017): 127–32. http://dx.doi.org/10.1016/j.automatica.2016.09.028.

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42

Tulli, Francesca, José M. Moreno-Rojas, Concetta Maria Messina, Angela Trocino, Gerolamo Xiccato, José M. Muñoz-Redondo, Andrea Santulli, and Emilio Tibaldi. "The Use of Stable Isotope Ratio Analysis to Trace European Sea Bass (D. labrax) Originating from Different Farming Systems." Animals 10, no. 11 (November 5, 2020): 2042. http://dx.doi.org/10.3390/ani10112042.

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This study aimed to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems and geographic origins. Dicentrarchus labrax of commercial size from three different rearing systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) were collected at the trading period (autumn–winter). For each farming type, different locations spread over Italy were monitored. Once the fish were harvested, the muscle and feed were sampled. For both muscle and feed, δ13C and δ15N were measured by continuous flow elemental analyzer isotope ratio mass spectrometry (CF-EA-IRMS) with the goal of discriminating samples based on the rearing system. Additional δ2H and δ18O measurements of fish samples were performed by continuous flow total combustion elemental analyzer isotope ratio mass spectrometry (CF-TC/EA-IRMS) to track the geographical origin. The measurements of δ13C and δ15N made it possible to discriminate cultured sea bass from different farming systems (extensive vs. intensive) reared at different geographical sites in Italy. Additional information was obtained from δ18O and δ2H, which enabled the geographical areas of origin of the sea bass farmed extensively and intensively (in cages) to be distinguished.

43

Spanjers, H., and G. Olsson. "On-Line Diagnosis of Do-Probe Condition in the Activated Sludge Process." Water Science and Technology 26, no. 9-11 (November 1, 1992): 2413–16. http://dx.doi.org/10.2166/wst.1992.0750.

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The dissolved oxygen (DO) probe is repeatedly subjected to a step change of the oxygen concentration with a time interval of 15-30 s. For this purpose an existing measuring technique was used in which the activated sludge was sampled continuously from the aeration tank. At each step the time constant of the probe response is estimated which provides a continuous diagnosis of the probe condition. Therefore the DO concentration measurements along the response are fitted to a first order response model of the probe. It was shown that the probe response time constant is a useful indicator for fouling of the probe membrane.

44

Kim, S. Y., R. Talbot, H. Mao, D. R. Blake, G. Huey, and A. J. Weinheimer. "Chemical transformations of Hg° during Arctic mercury depletion events sampled from the NASA DC-8." Atmospheric Chemistry and Physics Discussions 10, no. 4 (April 16, 2010): 10077–112. http://dx.doi.org/10.5194/acpd-10-10077-2010.

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Abstract. Atmospheric Mercury Depletion Events (MDEs) in Arctic springtime were investigated utilizing a box model based on airborne measurements from the NASA DC-8 during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. Measurements showed that MDEs occurred near the surface and always over the Arctic Ocean accompanied by concurrent ozone (O3) depletion, enhancement in Br2 mixing ratios, and decreases in ethyne and light weight alkanes. Backward trajectories indicated that most air masses inside the MDEs originated at low altitude over the ocean presumably generating a halogen-rich environment. We developed a box model which considered only gas phase reactions of mercury, halogen species, and O3 chemistry. We conducted a series of sensitivity simulations to determine the factors that are of most importance to MDE formation. The box model results suggested that continuous enhancement of Br2 mixing ratios, a high intensity of solar radiation, or a relatively high NOx regime expedited Hg° depletion. These environments generated high concentrations of Br radical, and thus the model results indicated that the Br radical was very important for Hg° depletion. Utilizing different rate constants for reaction of Hg° + Br produced times to reach Hg° depletion ranging from 22 to 32 h.

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Stith, J. L., C. H. Twohy, P. J. DeMott, D. Baumgardner, T. Campos, R. S. Gao, and J. Anderson. "Scavenging of biomass burning refractory black carbon and ice nuclei in a Western Pacific extratropical storm." Atmospheric Chemistry and Physics Discussions 11, no. 1 (January 7, 2011): 567–95. http://dx.doi.org/10.5194/acpd-11-567-2011.

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Abstract. In situ airborne sampling of refractory black carbon (rBC) particles and Ice Nuclei (IN) was conducted in and near an extratropical cyclonic storm in the Western Pacific Ocean during the Pacific Dust Experiment, PACDEX, in the spring of 2007. Airmass origins were from Eastern Asia. Cloud hydrometeors were evaporated by a counterflow virtual impactor and the residue was sampled by a single particle soot photometer (SP2) instrument and a continuous flow diffusion chamber ice nucleus detector. Clouds associated primarily with the warm sector of the storm were sampled at various locations and altitudes. In storm midlevels at temperatures where heterogeneous freezing is expected to be significant (here −24 to −29 °C), IN measurements from ice particle residues generally agreed well with simultaneous measurements of total ice concentrations provided that the measurements were made at ambient temperatures similar to those in the CFDC chamber, suggesting heterogeneous freezing as the dominant ice formation process in the mid levels of these warm sector clouds. Lower in the storm, at warmer temperatures (−22 to −6.4 °C), ice particle concentrations were similar to IN concentrations at CFDC chamber temperatures representative of colder temperatures. This is consistent with ice particles forming at storm mid-levels by heterogeneous freezing on IN, followed by sedimentation to lower altitudes. Homogeneous freezing did not appear to contribute significantly to midlevel ice concentrations and rime-splintering was also unlikely due to the absence of significant supercooled liquid water in the warm sector clouds. IN number concentrations were typically about a~factor of five to ten lower than simultaneous measurements of rBC concentrations in cloud.

46

Popa, M. E., A. T. Vermeulen, W. C. M. van den Bulk, P. A. C. Jongejan, A. M. Batenburg, W. Zahorowski, and T. Röckmann. "H2 vertical profiles in the continental boundary layer: measurements at the Cabauw tall tower in The Netherlands." Atmospheric Chemistry and Physics 11, no. 13 (July 6, 2011): 6425–43. http://dx.doi.org/10.5194/acp-11-6425-2011.

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Abstract. In-situ, quasi-continuous measurements of atmospheric hydrogen (H2) have been performed since October 2007 at the Cabauw tall tower station in the Netherlands. Mole fractions of H2, CO and several greenhouse gases are determined simultaneously in air sampled successively at four heights, between 20 and 200 m above ground level. 222Rn measurements are performed in air sampled at 20 and 200 m. This H2 dataset represents the first in-situ, quasi-continuous long-term measurement series of vertical profiles of H2 in the lower continental boundary layer. Seasonal cycles are present at all heights in both H2 and CO, and their amplitude varies with the sampling height. The seasonality is evident in both the "baseline" values and in the short term (diurnal to synoptic time scales) variability, the latter being significantly larger during winter. The observed H2 short term signals and vertical gradients are in many cases well correlated to other species, especially to CO. On the other hand, H2 has at times a unique behaviour, due to its particular distribution of sources and sinks. Our estimation for the regional H2 soil uptake flux, using the radon tracer method, is (−1.89 ± 0.26) × 10−5 g/(m2 h), significantly smaller than other recent results from Europe. H2/CO ratios of the traffic emissions computed from our data, with an average of 0.54 ± 0.07 mol:mol, are larger and more variable than estimated in some of the previous studies in Europe. This difference can be explained by a different driving regime, due to the frequent traffic jams in the influence area of Cabauw. The H2/CO ratios of the large scale pollution events have an average of 0.36 ± 0.05 mol:mol; these ratios were observed to slightly increase with sampling height, possibly due to a stronger influence of soil uptake at the lower sampling heights.

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Coles, Gerald A., Susan J. Minors, Jeffrey K. Horton, Richard Fifield, and Malcolm Davies. "Can the Risk of Peritonitis be Predicted for New Continuous Ambulatory Peritoneal Dialysis (CAPD) Patients?" Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 9, no. 1 (January 1989): 69–72. http://dx.doi.org/10.1177/089686088900900114.

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Serum and overnight dialysate samples were obtained from 36 adult uraemic patients at the end of their continuous ambulatory peritoneal dialysis (CAPD) training. The samples were analysed for albumin, IgG, C3, and antistaphylococcal peptidoglycan antibody. None of the dialysate measurements correlated with the risk of peritonitis during up to one year's CAPD treatment. Nineteen of the 36 patients were retested 6 to 20 months after starting CAPD. There were significant rises in serum C3 ( p < 0.02) and albumin ( p < 0.001) and a significant fall in dialysate IgG ( p < 0.02). Eight further patients were sampled at the end of training and three weeks later. They had a significant fall in dialysate IgG ( p < 0.05). During CAPD training peritoneal permeability appears to be transiently increased. Analysis of overnight dialysate samples during training does not allow prediction of those at risk of subsequent peritonitis.

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Jin, Liqin, Jakob Mann, Nikolas Angelou, and Mikael Sjöholm. "Suppression of precipitation bias in wind velocities from continuous-wave Doppler lidars." Atmospheric Measurement Techniques 16, no. 24 (December 15, 2023): 6007–23. http://dx.doi.org/10.5194/amt-16-6007-2023.

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Abstract. In moderate to heavy precipitation, raindrops may deteriorate the accuracy of Doppler lidar measurements of the line-of-sight wind velocity because their projected velocity in the beam direction differs greatly from that of air. Therefore, we propose a method for effectively suppressing the adverse effects of rain on velocity estimation by sampling the Doppler spectra faster than the time taken for a raindrop to transit through the beam. By using a special averaging procedure, we can suppress the strong rain signal by sampling the spectrum at 3 kHz. A proof-of-concept field measurement campaign was performed on a moderately rainy day with a maximum rain intensity of 4 mm h−1 using three ground-based continuous-wave Doppler lidars at the Risø campus of the Technical University of Denmark. We demonstrate that the rain bias can effectively be removed by normalizing the noise-flattened 3 kHz sampled Doppler spectra with their peak values before they are averaged down to 50 Hz prior to the determination of the speed. In comparison to the sonic anemometer measurements acquired at the same location, the wind velocity bias at 50 Hz (20 ms) temporal resolution is reduced from up to −1.58 m s−1 for the original raw lidar data to −0.18 m s−1 for the normalized lidar data after suppressing strong rain signals. This reduction in the bias occurs during the minute with the highest amount of rain when the focus distance of the lidar is 103.9 m and the corresponding probe length is 9.8 m. With the smallest probe length, 1.2 m, the rain-induced bias is only present at the period with the highest rain intensity and is also effectively eliminated with the procedure. Thus, the proposed method for reducing the impact of rain on continuous-wave Doppler lidar measurements of air velocity is promising and does not require much computational effort.

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Ensinger, Katharina, Nicholas Tagliapietra, Sebastian Ziesche, and Sebastian Trimpe. "Exact Inference for Continuous-Time Gaussian Process Dynamics." Proceedings of the AAAI Conference on Artificial Intelligence 38, no. 11 (March 24, 2024): 11883–91. http://dx.doi.org/10.1609/aaai.v38i11.29074.

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Many physical systems can be described as a continuous-time dynamical system. In practice, the true system is often unknown and has to be learned from measurement data. Since data is typically collected in discrete time, e.g. by sensors, most methods in Gaussian process (GP) dynamics model learning are trained on one-step ahead predictions. While this scheme is mathematically tempting, it can become problematic in several scenarios, e.g. if measurements are provided at irregularly-sampled time steps or physical system properties have to be conserved. Thus, we aim for a GP model of the true continuous-time dynamics. We tackle this task by leveraging higher-order numerical integrators. These integrators provide the necessary tools to discretize dynamical systems with arbitrary accuracy. However, most higher-order integrators require dynamics evaluations at intermediate time steps, making exact GP inference intractable. In previous work, this problem is often addressed by approximate inference techniques. However, exact GP inference is preferable in many scenarios, e.g. due to its mathematical guarantees. In order to enable direct inference, we propose to leverage multistep and Taylor integrators. We demonstrate how exact inference schemes can be derived for these types of integrators. Further, we derive tailored sampling schemes that allow one to draw consistent dynamics functions from the posterior. The learned model can thus be integrated with arbitrary integrators, just like a standard dynamical system. We show empirically and theoretically that our approach yields an accurate representation of the continuous-time system.

50

Jin, Liqin, Nikolas Angelou, Jakob Mann, and Gunner Chr Larsen. "Improved wind speed estimation and rain quantification with continuous-wave wind lidar." Journal of Physics: Conference Series 2265, no. 2 (May 1, 2022): 022093. http://dx.doi.org/10.1088/1742-6596/2265/2/022093.

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Abstract The presence of raindrops has an adverse impact on the line-of-sight wind speed measurement of Doppler lidars. Here, we propose a method to improve the accuracy of wind speed estimation through a filtering process on rapidly sampled (3000 Hz) lidar data. For this purpose, we conducted a field study at the Risø campus of the Technical University of Denmark using a ground-based, continuous-wave Doppler lidar. Data was acquired during a three-hour period with rain. We propose that we can differentiate between the rain and aerosol back-scattering signals by assessing the maximum of the noise-normalized Doppler spectra. To reduce the influence of rain of the velocity signal, we filter away the Doppler spectra where the maximum is larger than a given threshold. The comparison between the raw and the filtered lidar data with sonic anemometer measurements acquired at the same location, shows that we can effectively remove rain signals and improve the measurement accuracy of a Doppler lidar. However, this method is not applicable when the back-scattering of aerosols and rain are characterized by the same statistics.

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