Discrete Measurements Research Articles

Carbon emission and export from the Ket River, western Siberia

Abstract. Despite recent progress in the understanding of the carbon (C) cycle of Siberian permafrost-affected rivers, spatial and seasonal dynamics of C export and emission from medium-sized rivers (50 000–300 000 km2 watershed area) remain poorly known. Here we studied one of the largest tributaries of the Ob River, the Ket River (watershed = 94 000 km2), which drains through pristine taiga forest of the boreal zone in the West Siberian Lowland (WSL). We combined continuous and discrete measurements of carbon dioxide (CO2) concentration using submersible CO2 sensor and floating chamber flux (FCO2), with methane (CH4), dissolved organic and inorganic C (DOC and DIC, respectively), particulate organic C and total bacterial concentrations over an 800 km transect of the Ket River main stem and its 26 tributaries during spring flood (May 2019) and 12 tributaries during summer baseflow (end of August–beginning of September 2019). The partial pressure of CO2 (pCO2) was lower and less variable in the main stem (2000 to 2500 µatm) compared to that in the tributaries (2000 to 5000 µatm). In the tributaries, the pCO2 was 40 % higher during baseflow compared to spring flood, whereas in the main stem, it did not vary significantly across the seasons. The methane concentration in the main stem and tributaries was a factor of 300 to 1900 (flood period) and 100 to 150 times lower than that of CO2 and ranged from 0.05 to 2.0 µmol L−1. The FCO2 ranged from 0.4 to 2.4 g C m−2 d−1 in the main channel and from 0.5 to 5.0 g C m−2 d−1 in the tributaries, being highest during August in the tributaries and weakly dependent on the season in the main channel. During summer baseflow, the DOC aromaticity, bacterial number, and needleleaf forest coverage of the watershed positively affected CO2 concentrations and fluxes. We hypothesize that relatively low spatial and seasonal variability in FCO2 of the Ket River is due to a flat homogeneous landscape (bogs and taiga forest) that results in long water residence times and stable input of allochthonous dissolved organic matter (DOM), which dominate the FCO2. The open water period (May to October) C emission from the fluvial network (main stem and tributaries) of the Ket River was estimated to 127 ± 11 Gg C yr−1, which is lower than the downstream dissolved and particulate C export during the same period. The estimated fluvial C emissions are highly conservative and contain uncertainties linked to ignoring hotspots and hot moments of emissions, notably in the floodplain zone. This stresses the need to improve the temporal resolution of FCO2 and water coverage across seasons and emphasizes the important role of WSL rivers in the release of CO2 into the atmosphere.

Modeling finite-strain plasticity using physics-informed neural network and assessment of the network performance

Physics-informed neural networks (PINN) can solve partial differential equations (PDEs) by encoding the mathematical information explicitly into the loss functions. In the context of plasticity, discussions of PINN have only focused on small-strain formulations. We present a framework of finite-strain elasto-plasticity for PINN, considering rate-independent isotropic hardening in this work. Details of the model architecture are discussed, including inputs and outputs of the neural network and the construction of the loss function that incorporates equilibrium equations, boundary conditions and constitutive relations. In addition, the overall architecture can learn the constitutive relations from discrete measurements on a stress–strain curve, hence eliminating the need for modeling hardening law in the formulation. We demonstrate the performance of PINN through a numerical example that includes a multi-step loading and unloading history. Moreover, we assess the performance of PINN in terms of its accuracy and robustness under mesh refinement and as a function of the network architecture design. Displacement, Cauchy stress and accumulated plastic strain fields are compared to the finite element results for the same problem for the purposes of this assessment, which is intended to provide insight and guidance for the future designs of PINN for plasticity and related problems in solid mechanics.

Assessment of Greenhouse Gas Emissions into the Atmosphere from the Northern Peatlands Using the Wetland-DNDC Simulation Model: A Case Study of the Great Vasyugan Mire, Western Siberia

The peatlands of Western Siberia occupy an area of about 1 million km2 and act as important regulator of carbon exchange between the earth and the atmosphere. Extrapolation of the results of discrete field measurements of CO2 fluxes in bog ecosystems to such a territory is a difficult task, and one of the ways to overcome it is to use a simulation model such as DNDC. However, using this model with a specific territory requires ground verification to confirm its effectiveness. Here, we tested the DNDC model on the largest pristine bog ecosystem of the world, the Great Vasyugan Mire (GVM). The GVM of western Siberia is virtually undisturbed by anthropogenic activity and is the largest bog of Northern Eurasia (53,000 km2). Based on various ground-based observations, the performance of the Wetland-DNDC model was demonstrated (Thale coefficient 0.085 and R2 = 0.675 for CO2). Model input parameters specific to the GVM were constrained and model sensitivity to a wide range of input parameters was analyzed. The estimated annual terrestrial carbon fluxes in 2019 from the GVM test site are mainly controlled by plant respiration (61%) and forest floor degradation (38%). The net CO2 emission flux was 8600 kg C ha−1 year−1, which is in line with estimates from other independent studies.

Beurling dimension and a class of Moran measures

In this paper, we will study the Beurling dimension of spectra for Moran measures defined by infinite convolution of discrete measures μb,D,{nj}=δb−n1D∗δb−(n1+n2)D∗δb−(n1+n2+n3)D∗⋯. We obtain the upper and lower bounds of the dimension. More precisely, the upper bound is the Hausdorff dimension of the compact support of μb,D,{nj} and the lower bound is 0. The bounds are attained in special cases and some examples are given to explain our theory.

Measurement of Restrained and Unrestrained Shrinkage of Reinforced Concrete Using Distributed Fibre Optic Sensors

Shrinkage is an important component of the behaviour of reinforced concrete (RC) structures, however, the number of variables that affect shrinkage make it a complex time-dependent phenomenon. Additionally, as new concrete materials with lower embodied carbon gain popularity, there is a need for an in-depth understanding into their shrinkage behaviour before they can be widely adopted by industry. Currently, the shrinkage behaviour of concrete is studied using discrete measurements on small-scale unrestrained prisms. Distributed fibre optic sensing (DFOS) potentially provides a method of measuring both restrained (with reinforcement) and unrestrained (without reinforcement) shrinkage in both small-scale specimens and structural elements. In the current study, methods of measuring distributed unrestrained shrinkage strains were developed and evaluated, and the restrained shrinkage strains in different types of structural members were studied. Unrestrained shrinkage strains were measured using fibres optic cables embedded in small concrete prisms, while restrained shrinkage strains were measured with fibres bonded to the longitudinal reinforcement. Unrestrained shrinkage strains were found to be highly variable (as large as 3800 microstrain range) depending on location, but further research needs to be undertaken to account for end effects, early-stage shrinkage, and bond between the fibre optic cable and the concrete. Restrained shrinkage strains from structural members revealed non-uniform shrinkage strain distributions along member length due to functional grading as well as high supplementary cementitious material concretes, suggesting that shrinkage models will need to account for this variability.

Application of infrared thermal imaging technique in in-situ temperature field measurement of hydrate-bearing sediment under thermal stimulation

Natural gas hydrate is a green energy with great development prospects. The exploitation of natural gas hydrate has been attracting much attention. The temperature field distribution of hydrate-bearing sediment is a crucial indication on the heat or mass transfer characteristics and thermal properties of hydrate-bearing sediment during hydrate exploitation. However, to date, the acquisition means of temperatures of hydrate-bearing sediment have been limited to the discrete temperature measurement by using the contact-type temperature sensors inserted into hydrate sediment. The continuous evolution of temperature field of hydrate-bearing sediment can be hardly achieved. Thus, in this study, a new method applying the non-contact and non-destructive infrared thermal imager was developed and applied in the in-situ measurement of the continuous evolution of temperature field of hydrate-bearing sediment. The results confirm the feasibility of application of the infrared thermal imaging technique in the hydrate-related research. The complete continuous temperature fields of hydrate-bearing sediment and non-hydrate-bearing sediment under thermal stimulation were imaged and compared. The results indicate that the temperature field distribution of hydrate sediment is predominately controlled by the effective thermal conductivity of hydrate-bearing sediment. In addition, the effects of the type of hydrate-bearing sediment, heating power and particle size of sediment were investigated.

Prenatal Perception of WIC Breastfeeding Recommendations Predicts Breastfeeding Exclusivity and Duration in the Infants’ First Year

Pregnant participants who perceived that the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) recommends breastfeeding only were more likely to have better early breastfeeding outcomes. Our objective was to examine the association between prenatal perception of WIC's breastfeeding recommendations and breastfeeding duration through the first year of infant life. This observational study used a national longitudinal sample of 1594 pregnant participants in the WIC Infant and Toddler Feeding Practices Study-2 in 2013. Four measures of breastfeeding duration were used: 1) a discrete measure of exclusive breastfeeding through 5 mo; 2) a continuous measure of exclusive breastfeeding (in days up to 7 mo); 3) a discrete measure of any breastfeeding through 11 mo; and 4) a continuous measure of any breastfeeding (in days up to 13 mo). The primary explanatory variable was the participant's prenatal perception of whether WIC recommended breastfeeding only. The univariate analyses of time to breastfeeding cessation were performed using Kaplan-Meier curves. The Cox regression model was adopted to estimate the likelihood of breastfeeding outcomes over time. All analyses accounted for complex survey design effects. Compared with their peers who perceived WIC to recommend formula only or both breastfeeding and formula equally, participants who perceived WIC as recommending breastfeeding only were less likely to stop exclusive breastfeeding through 5 mo (HR = 0.83; 95% CI: 0.69, 0.99) or to stop any breastfeeding through 11 mo (HR = 0.80; 95% CI: 0.69, 0.92), without controlling for prenatal infant feeding intentions. Similar patterns were observed in the 2 continuous measures, as they were also less likely to stop exclusive breastfeeding by 7 mo (HR = 0.78; 95% CI: 0.69, 0.90) or to stop any breastfeeding by 13 mo (HR = 0.82; 95% CI: 0.71, 0.95). Prenatal perception of WIC's breastfeeding recommendation can be a useful predictor of breastfeeding duration in WIC participants.

Statistical solutions of the two-dimensional incompressible Euler equations in spaces of unbounded vorticity

We study statistical solutions of the incompressible Euler equations in two dimensions with vorticity in Lp, 1≤p≤∞, and in the class of vortex-sheets with a distinguished sign. Our notion of statistical solution is based on the framework due to Bronzi, Mondaini and Rosa in [4]. Existence in this setting is shown by approximation with discrete measures, concentrated on deterministic solutions of the Euler equations. Additionally, we provide arguments to show that the statistical solutions of the Euler equations may be obtained in the inviscid limit of statistical solutions of the incompressible Navier-Stokes equations. Uniqueness of trajectory statistical solutions is shown in the Yudovich class.

The Lp Minkowski problem for q-torsional rigidity

Abstract In this paper, we introduce the L p {L_{p}} q-torsional measure for p ∈ ℝ {p\in\mathbb{R}} and q > 1 {q>1} by the L p {L_{p}} variational formula for the q-torsional rigidity of convex bodies without smoothness conditions. Moreover, we achieve the existence of solutions to the L p {L_{p}} Minkowski problem with respect to the q-torsional rigidity for discrete measures and general measures when 0 < p < 1 {0<p<1} and q > 1 {q>1} .

An innovative modulating functions method for pseudo-state estimation of fractional order systems

In this paper, the objective is to estimate the pseudo-state of fractional order systems defined by the Caputo fractional derivative from discrete noisy output measurement. For this purpose, an innovative modulating functions method is proposed, which can provide non-asymptotic estimation within finite-time and is robust against corrupting noises. First, the proposed method is directly applied to the Brunovsky’s observable canonical form of the considered system. Then, the initial value of the pseudo-state is exactly expressed by an algebraic integral formula, based on which the pseudo-state is estimated. Second, the properties and construction of the required modulating functions are studied. Furthermore, error analysis is provided in discrete noise cases, which is useful for improving the estimation accuracy. In order to show the advantages of the proposed method, two numerical examples are given, where both rational order and irrational order dynamical systems are considered. After selecting the design parameters using the provided noise error bound, the pseudo-states of considered systems are estimated. The fractional order Luenberger-like observer and the fractional order H∞-like observer are also applied. Better than the applied fractional order observers, the proposed method can guarantee the convergence speed and robustness at the same time.

A complementary note for the analytical method to estimate individual attention fluctuation using steady-state evoked potentials

Intra-individual variability of steady-state evoked potentials (ssEPs) is correlated with attention fluctuations and reveals the participant’s ability to sustain attention. We previously presented an analytical method to measure the variation of discrete Fourier measurements at the frequency of interest extracted from ssEP data and to model the Fourier estimates on the two-dimensional complex plane with an ellipse. In this paper, we will introduce the ratio of the major to minor axes of the ellipse, which we call the Length-to-Width Ratio (LWR), as an index of individual ability to control attention and show how to calculate the confidence interval of the LWR to be able to compare the LWR between conditions within a participant as well as between participants within or between studies. The method will enable us to find out the most sensitive electroencephalography electrode to attention fluctuation, to explore the neural correlates of attention, to differentiate cases with inconsistent control of attention from normal participants, and to objectively monitor the effects of therapeutic interventions on attention.

Generalized Savitzky–Golay filter for smoothing triangular meshes

In this paper, the well-known Savitzky–Golay filter is generalized for three-dimensional triangular meshes. Savitzky–Golay filter is designed for smoothing noisy measurement signals, initially, a locally polynomial model is fitted to approximate the discrete measurement values. We will show, that the original idea can be naturally adapted for smoothing functions defined on an irregular two-dimensional triangular mesh. Primarily surfaces represented by three-dimensional triangular meshes are in the focus of this paper, which are by definition locally homeomorphic to the two-dimensional topological disk. As the generalized filter is meaningful on the plane, we will define local embeddings that send vertices and their neighborhoods to the disk. The points of the two-dimensional disk and the three-dimensional surface can be paired to each other using these embeddings, thereafter low-degree multidimensional polynomials can be fitted to the point pairs obtaining a similar continuous model, just like in the one-dimensional case. Finally, we show an application of our method for mesh smoothing, and a comparison to other mesh smoothing methods, e.g. the Laplacian smoothing and the Taubin smoothing.

Gamma Radiation Dose Measurement Using an Energy-Selective Method with the Help of a Drone

Several dose distribution maps were obtained using a gamma radiation detector mounted to a drone. Based on the results and experience of the experiments, the shortcomings of the system and the possibilities for further development were identified. The primary goal of the development was to create a more compact, easy-to-carry, and easy-to-install system with increased sensitivity, which was achieved by several different methods and their combinations. During the discrete measurement procedure, the aim was to decrease the detection threshold, +0.005 to +0.007 μS/h measured above the background radiation. The increase in sensitivity was based on the characteristic energy spectrum of radiative materials. We took advantage of the fact that the radiating samples do not evenly increase the amount of gamma radiation over the entire energy spectrum. During the processing of the measurement data, we performed a comparison with the background radiation in the vicinity of the energy peaks characteristic of the sample and its decay products. This provides a better signal-to-noise ratio, thus enabling a more sensitive detection procedure. An important feature of our method is that in the traditional intensity curve displayed as a function of flight time only noise is visible, therefore one cannot directly conclude the presence of the sample. However, our method is clearly able to identify the location of the searched source at a height of 8 m with a continuous flight speed of 2 m/s using a 500 μS/h activity sample (as measured at a distance of 0.1 m from the sample). The increase in sensitivity allows either a higher scanning height (approximately +1 to 2 m) or, in the case of the same aircraft at the same altitude, a larger area from one take-off. Of course, the scan height or scan speed can increase significantly if the activity of the source being sought is high. In our experiments, we used a natural uranium mineral (Autunite) with activity far below that of artificially produced isotopes. In the series of our experiments, we also covered the detection of several sources, which modeled the possibility of mapping scattered active sources. The main advantages of the system developed and presented by us over the survey procedures used in practice is that a large area can be mobilized easily, without the risk of a human operator in the field, and the survey of a large area can be carried out at a low cost. The purpose of the system is to detect the presence of the source and to localize it to such an extent that the localization can then be easily refined by manual or other ground procedures. As we do not aim for positioning accuracy by centimeter, standard GPS localization is sufficient for the measurements. During the measurements, the geographical coordinates are interpreted in the GWS'84 system. The coordinates of the latitude and longitude circles are also shown in this system in the figures presented.

Validation of pitchAITM markerless motion capture using marker-based 3D motion capture

ABSTRACT This study sought to compare and validate baseball pitching mechanics, including joint angles and spatiotemporal parameters, from a single camera markerless motion capture solution with a 3D optical marker-based system. Ten healthy pitchers threw 2–3 maximum effort fastballs while concurrently using marker-based optical capture and pitchAITM (markerless) motion capture. Time-series measures were compared using R-squared (r2), and root mean square error (RMSE). Discrete kinematic measures at foot plant, maximal shoulder external rotation, and ball release, plus four spatiotemporal parameters were evaluated using descriptive statistics, Bland-Altman analyses, Pearson’s correlation coefficients, p-values, r2, and RMSE. For time-series angles, r2 ranged from 0.69 (glove arm shoulder external rotation) to 0.98 (trunk and pelvis rotation), and RMSE ranged from 4.37° (trunk lateral tilt) to 20.78° (glove arm shoulder external rotation). Bias for individual joint angle and spatiotemporal parameters ranged from −11.31 (glove arm shoulder horizontal abduction; MER) to 12.01 (ball visible). RMSE was 3.62 m/s for arm speed, 5.75% height for stride length and 21.75 ms for the ball visible metric. pitchAITM can be recommended as a markerless alternative to marker-based motion capture for quantifying pitching kinematics. A database of pitchAITM ranges should be established for comparison between systems.

Score rectification for online assessments in robot-assisted arm rehabilitation

AbstractRelative comparison of clinical scores to measure the effectiveness of neuro-rehabilitation therapy is possible through a series of discrete measurements during the rehabilitation period within specifically designed task environments. Robots allow quantitative, continuous measurement of data. Resulting robotic scores are also only comparable within similar context, e.g. type of task. We propose a method to decouple these scores from their respective context through functional orthogonalization and compensation of the compounding factors based on a data-driven sensitivity analysis of the user performance. The method was validated for the established accuracy score with variable arm weight support, provoked muscle fatigue and different task directions on 6 participants of our arm exoskeleton group on the ANYexo robot. In the best case, the standard deviation of the assessed score in changing context could be reduced by a factor of 3.2. Therewith, we paved the way to context-independent, quantitative online assessments, recorded autonomously with robots.

Discrete and continuous measures of consequentiality

ABSTRACT A respondent finds a survey consequential if they believe their answer could influence the policy being addressed in the survey and if they believe that they will have to pay for the policy if implemented. Given these criteria, the literature has followed two paths to analyse consequentiality. The first uses a discrete method that separates respondents into consequential and inconsequential groups. The second interprets beliefs about consequentiality as continuous. We compare these approaches to identify their strengths and weaknesses. Using the discrete approach, we classify respondents into groups based on whether their responses satisfy various consequentiality criteria. We find that respondents in the inconsequential group have a willingness to pay that is insignificantly different from zero. For those in the consequential group, willingness to pay is positive and depends on the scope of the project. Treating consequentiality as continuous and using the hybrid choice model, we find that individuals who believe their responses will influence policy, policy consequentiality, and those who are concerned about the amenity are more likely to be in favour of the policy. Lastly, income is positively related to payment consequentiality.

Characterizing Flow Instabilities During Transient Events in the Turbine Rim Seal Cavity

Abstract Gas turbine engine design requires considerations not only for long-term steady operation but also for critical transient events. Aircraft engines undergo significant stress during takeoff and landing, while power generation turbines must be flexible for hot restarts as renewable energy sources come online and offline. During these transient cycles, engines sustain wear and degradation that can lead to a reduction in the lifespan of their components and more frequent, costly maintenance. Cooling flows are often used to mitigate these effects, but can lead to complex and problematic flow interactions. This study uses high-frequency response pressure probes and heat flux gauges in the rim seal cavity of a one-stage research turbine to characterize the properties of large-scale flow structures during transient operation. A continuous-duration turbine testing facility provides the ability to assess the importance of these transients by first reaching steady-state operation before imposing transient behaviors. Although previous studies have conducted similar measurements for steady purge flows and wheel speeds, varying these parameters to simulate transient effects revealed several unique phenomena not identifiable with discrete steady measurements. The measurement approach connects the varied transient parameter to the behavior of the flow structures to enable a better understanding of the type of instability observed and the root cause of its formation. In particular, a relationship between instability cell formation and rim sealing effectiveness was identified using experimental data and was supported through computational simulations.

Thermodynamics of quantum measurement and Maxwell's demon's arrow of time

We discuss the thermodynamic aspects of a single qubit based device, powered by weak quantum measurements, and feedback controlled by a quantum Maxwell's demon. We discuss both discrete and time-continuous operation of the measurement based device at finite temperature of the reservoir. In the discrete example where a demon acquires information via discrete weak measurements, we find that the thermodynamic variables including the heat exchanged, extractable work, and the entropy produced are completely determined by an information theoretic measure of the demon's perceived arrow of time. We also discuss a realistic time-continuous operation of the device where the feedback is applied after a sequence of weak measurements. In the time-continuous limit, we derive the exact finite-time statistics of work, heat and entropy changes along individual quantum trajectories of the quantum measurement process, and relate them to the demon's arrow of time.

Riesz Energy Problems with External Fields and Related Theory

In this paper, we investigate Riesz energy problems on unbounded conductors in $$\mathbb {R}^d$$ in the presence of general external fields Q, not necessarily satisfying the growth condition $$Q(x)\rightarrow +\infty $$ as $$|x|\rightarrow +\infty $$ assumed in several previous studies. We provide sufficient conditions on Q for the existence of an equilibrium measure and the compactness of its support. Particular attention is paid to the case of the hyperplanar conductor $$\mathbb {R}^{d}$$ , embedded in $$\mathbb {R}^{d+1}$$ , when the external field is created by the potential of a signed measure $$\nu $$ supported outside of $$\mathbb {R}^{d}$$ . Simple cases where $$\nu $$ is a discrete measure are analyzed in detail. New theoretic results for Riesz potentials, in particular an extension of a classical theorem by de La Vallée Poussin, are established. These results are of independent interest.

What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications.

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective.