Modeling and Prediction of Nonlinear Environmental System Using Bayesian Methods

in Computers & Electronics in Agriculture (2013), 92

An environmental dynamic system is usually modeled as a nonlinear system described by a set of nonlinear ODEs. A central challenge in computational modeling of environmental systems is the determination ... [more ▼]

An environmental dynamic system is usually modeled as a nonlinear system described by a set of nonlinear ODEs. A central challenge in computational modeling of environmental systems is the determination of the model parameters. In these cases, estimating these variables or parameters from other easily obtained measurements can be extremely useful. This work addresses the problem of monitoring and modeling a leaf area index and soil moisture model (LSM) using state estimation. The performances of various conventional and state-of-the-art state estimation techniques are compared when they are utilized to achieve this objective. These techniques include the extended Kalman filter (EKF), the particle filter (PF), and the more recently developed technique variational filter (VF). Specifically, two comparative studies are performed. In the first comparative study, the state variables (the leaf-area index LAI , the volumetric water content of the soil layer 1, HUR1 and the volumetric water content of the soil layer 2, HUR2) are estimated from noisy measurements of these variables, and the various estimation techniques are compared by computing the estimation root mean square error (RMSE) with respect to the noise-free data. In the second comparative study, the state variables as well as the model parameters are simultaneously estimated. In this case, in addition to comparing the performances of the various state estimation techniques, the effect of number of estimated model parameters on the accuracy and convergence of these techniques are also assessed. The results of both comparative studies show that the PF provides a higher accuracy than the EKF, which is due to the limited ability of the EKF to handle highly nonlinear processes. The results also show that the VF provides a significant improvement over the PF because, unlike the PF which depends on the choice of sampling distribution used to estimate the posterior distribution, the VF yields an optimum choice of the sampling distribution, which also accounts for the observed data. The results of the second comparative study show that, for all techniques, estimating more model parameters affects the estimation accuracy as well as the convergence of the estimated states and parameters. However, the VF can still provide both convergence as well as accuracy related advantages over other estimation methods. [less ▲]

Prediction of residual stresses by FE simulations on bimetallic work rolls during cooling

in Computer Methods in Materials Science (2013), 13(1), 84-91

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic ... [more ▼]

Bimetallic rolls used in the roughing stands of the Hot Strip Mill require mixed properties as a high wear resistance for the shell material and an enhanced toughness for the core material. The bimetallic roll studied in this paper is obtained from a vertical spin casting process followed by cooling and subsequent heat treatments. Failure of the compound roll sometimes occurs during the cooling stage of the casting route or later during the thermal treatments. It requires to deeply investigate the thermo mechanical metallurgical interactions generated during cooling and heat treatment in order to find the origin of cracks. For this purpose, a thermo metallurgic mechanical finite element model is used. However these numerical simulations require a high amount of mechanical, thermal and metallurgical parameters. In order to determinate these parameters, a study of available data for estimation of mechanical parameters was performed. Thermo physical parameters were obtained by DTA and DSC methods. Metallurgical characterization by inverse numerical method based on available CCT diagrams was performed to determine the TTT diagrams. First cooling numerical simulations are presented, allowing a rough estimate of residual stresses values and the identification of key parameters for predicting accurate residual stresses by sensitivity analysis. [less ▲]

3D-Characterization of the veneer-zirconia interface using FIB nano-tomography.

in Dental materials : official publication of the Academy of Dental Materials (2013), 29(2), 157-65

OBJECTIVES: The phenomena occurring during zirconia frameworks veneering process are not yet fully understood. In particular the study of zirconia behavior at the interface with the veneer remains a ... [more ▼]

OBJECTIVES: The phenomena occurring during zirconia frameworks veneering process are not yet fully understood. In particular the study of zirconia behavior at the interface with the veneer remains a challenge. However this interface has been reported to act on residual stress in the veneering ceramic, which plays a significant role in clinical failures such as chipping. The objective of this study was thus to investigate the veneer-zirconia interface using a recent 3D-analysis tool and to confront these observations to residual stress measurements in the veneering ceramic. METHODS: Two cross-sectioned bilayered disc samples (veneer on zirconia), exhibiting different residual stress profiles in the veneering ceramic, were investigated using 2D and 3D imaging (respectively Scanning Electron Microscopy (SEM) and Focused Ion Beam nanotomography (FIB-nt), associated with chemical analysis by Energy Dispersive X-ray Spectroscopy (EDS). RESULTS: The observations did not reveal any structural change in the bulk of zirconia layer of both samples. However the presence of structural alterations and sub-surface microcracks were highlighted in the first micrometer of zirconia surface, exclusively for the sample exhibiting interior tensile stress in the veneering ceramic. No interdiffusion phenomena were observed. SIGNIFICANCE: FIB nanotomography was proven to be a powerful technique to study the veneer-zirconia interface. The determination of the origin and the nature of zirconia alterations need to be further studied. The results of the present study support the hypothesis that zirconia surface property changes could be involved in the development of tensile stress in the veneering ceramic, increasing the risk of chipping. [less ▲]

Sedimentology and magnetic susceptibility of Mississippian (Tournaisian) carbonate sections in Belgium

in Bulletin of Geosciences (2013), 88(1), 69-82

Magnetic susceptibility (MS) and biostratigraphy have been used to correlate better the reference sections of Belgian Tournaisian, the Rivage road and railway sections and the Gendron-Celles railway ... [more ▼]

Magnetic susceptibility (MS) and biostratigraphy have been used to correlate better the reference sections of Belgian Tournaisian, the Rivage road and railway sections and the Gendron-Celles railway section. These 200 m thick time-equivalent sections are about sixty kilometres apart and belong to two different sedimentation areas: a shallow ramp setting for Rivage (Condroz Sedimentation Area, Hance et al., 2001) and a subsiding area for Gendron (Dinant Sedimentation Area). The sedimentological model shows that both sections are characterized by a bioclastic dominated sedimentation (crinoids-peloids-algae assemblages), interrupted by more argillaceous facies related to rapid sea-level rises (crinoids-brachiopods-bryozoans assemblages). Accommodation was significantly higher in the DSA and allowed the development of Waulsortian buildups during the Ivorian. Variations of magnetic susceptibility (MS) seem to be related to fluctuations in detrital input and carbonate productivity. MS evolution with palaeogeography can be integrated in the Da Silva et al. (2009a) model for the Devonian ramp system: external ramp settings have low carbonate productivity, low water agitation and high MS, whereas more proximal environments are characterized by higher carbonate productivity, higher water agitation and lower MS. Carbonate buildups show the lowest MS and highest productivity. MS curves are in agreement with the 3rd-order sequential interpretation. Lowstand system tracts (LST) show the highest MS values while transgressive system tracts (TST) are characterized by decreasing values and highstand system tracts/ falling stage system tracts (HST/FSST) by the lowest values. [less ▲]

Numerical Exploration of Oscillation Modes in Rapidly Rotating Stars

in Goupil, M.; Belkacem, K.; Neiner, C. (Eds.) et al Studying Stellar Rotation and Convection (2013)

In this chapter, we show that two-dimensional oscillation codes help us to improve our knowledge of the effects of rapid rotation on acoustic (p) and gravity (g) modes. We first discuss how to solve the ... [more ▼]

In this chapter, we show that two-dimensional oscillation codes help us to improve our knowledge of the effects of rapid rotation on acoustic (p) and gravity (g) modes. We first discuss how to solve the full problem of stellar oscillations in rapidly rotating stars by including the effects of the Coriolis force as well as those of the centrifugal distortion. We illustrate the development and the validation of a 2-D code using the Two-dimensional Oscillation Program (TOP) as an example. We then describe what strategies are being developed to explore the p- and g-mode spectra, how effective these methods are, and what intrinsic difficulties they face. In the last part of this chapter, we present results obtained with these techniques. [less ▲]

Determination of Moisture Diffusivity During Drying of Mortar Cement: Experimental and Modeling Study

in International Journal of Energy Engineering (2013), 3(1), 1-6

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed ... [more ▼]

The aim of this study is the experimental characterization of the behaviour of a mortar during convective drying. We focalise on mortar that has a rate water-cement of 0.5. The drying tests are developed in a micro-convective dryer that can use samples weighing from 0 to 8g. The advantage of these experiments is to reproduce the natural conditions that can be found during the treatment of the mortar-atmosphere problems. The response of the drying curve or the drying kinetic depends on the applied drying conditions. So, the temperature of the air varies from 60°C to 130°C, the velocity of the air is changed from 2 m.s-1 to 5 m. s-1and the relative humidity is kept less than 1.7%. The comparison between the experimental results and the proposed analytical solutions of the equation of diffusion represented by Fick’s law, applied for a finite shape, allows determination of the values of the diffusion coefficient. It has a value of 1.71×10-10 m2.s-1 at 60°C, 13.69×10-10 m2.s-1 at 90°C and 16.27×10-10 m2.s-1 at 130°C. Calculation of the activation energy and the D0 constant are also possible. [less ▲]

Quelques considérations sur la préservation de l'authenticité des quartiers résidentiels modernes du nord de Bucarest

in Crisan, Rodica, Franco, Giovanna; Musso, Stefano F. (Eds.) Conservation / Regeneration - The modernist neighborhood (2013)

Raw or heated cow milk consumption: Review of risks and benefits

in Food Control (2013), 31(1), 251-262

In the context of the prevailing trend toward more natural products, there seems to be an increasing preference for raw milk consumption as raw milk is associated with several perceived health benefits ... [more ▼]

In the context of the prevailing trend toward more natural products, there seems to be an increasing preference for raw milk consumption as raw milk is associated with several perceived health benefits that are believed to be destroyed upon heating. However, many human pathogens can be isolated from raw cow milk. The prevalence of foodborne pathogens in raw cow milk varies, but their presence has been demonstrated in many surveys and foodborne infections have been repeatedly reported for Campylobacter, Salmonella spp. and human pathogenic verocytotoxin-producing Escherichia coli. In industrialized countries, milk-borne and milk product-borne outbreaks represent 2-6% of the bacterial foodborne outbreaks.The aim of this review is to present scientifically sound data regarding the risks and benefits related to the consumption of raw and heated cow milk. Both microbiological aspects (e.g., the prevalence of milk-borne pathogens, pathogen growth inhibition by antimicrobial systems and by lactic acid producing bacteria, probiotic bacteria, etc.) and nutritional or health aspects (nutritional value, immunity, allergies, lactose intolerance, diabetes, milk digestibility, etc.) are considered.As such, it is demonstrated that consumption of raw milk poses a realistic health threat due to a possible contamination with human pathogens. It is therefore strongly recommended that milk should be heated before consumption. With the exception of an altered organoleptic profile, heating (in particularly ultra high temperature and similar treatments) will not substantially change the nutritional value of raw milk or other benefits associated with raw milk consumption. © 2012 Elsevier Ltd. [less ▲]

A multi-scale cardiovascular system model can account for the load-dependence of the end-systolic pressure-volume relationship.

in BioMedical Engineering OnLine (2013), 12(1), 8

ABSTRACT: BACKGROUND: The end-systolic pressure-volume relationship is often considered as a load-independent property of the heart and, for this reason, is widely used as an index of ventricular ... [more ▼]

ABSTRACT: BACKGROUND: The end-systolic pressure-volume relationship is often considered as a load-independent property of the heart and, for this reason, is widely used as an index of ventricular contractility. However, many criticisms have been expressed against this index and the underlying time-varying elastance theory: first, it does not consider the phenomena underlying contraction and second, the end-systolic pressure volume relationship has been experimentally shown to be load-dependent. METHODS: In place of the time-varying elastance theory, a microscopic model of sarcomere contraction is used to infer the pressure generated by the contraction of the left ventricle, considered as a spherical assembling of sarcomere units. The left ventricle model is inserted into a closed-loop model of the cardiovascular system. Finally, parameters of the modified cardiovascular system model are identified to reproduce the hemodynamics of a normal dog. RESULTS: Experiments that have proven the limitations of the time-varying elastance theory are reproduced with our model: (1) preload reductions, (2) afterload increases, (3) the same experiments with increased ventricular contractility, (4) isovolumic contractions and (5) flow-clamps. All experiments simulated with the model generate different end-systolic pressure-volume relationships, showing that this relationship is actually load-dependent. Furthermore, we show that the results of our simulations are in good agreement with experiments. CONCLUSIONS: We implemented a multi-scale model of the cardiovascular system, in which ventricular contraction is described by a detailed sarcomere model. Using this model, we successfully reproduced a number of experiments that have shown the failing points of the time-varying elastance theory. In particular, the developed multi-scale model of the cardiovascular system can capture the load-dependence of the end-systolic pressure-volume relationship. [less ▲]

The influence of a grain boundary on the thermal transport properties of bulk, melt-processed Y-Ba-Cu-O

in Superconductor Science and Technology (2013), 26

We report the dependence of thermal conductivity, thermoelectric power and electrical resistivity on temperature for a bulk, large grain melt-processed Y-Ba-Cu-O (YBCO) high temperature superconductor ... [more ▼]

We report the dependence of thermal conductivity, thermoelectric power and electrical resistivity on temperature for a bulk, large grain melt-processed Y-Ba-Cu-O (YBCO) high temperature superconductor (HTS) containing two grains separated by a well-defined grain boundary. Transport measurements at temperatures between 10 and 300 K were carried out both within one single grain (intra-granular properties) and across the grain boundary (inter-granular properties). The influence of an applied external magnetic field of up to 8 T on the measured sample properties was also investigated. The presence of the grain boundary is found to affect strongly the electrical resistivity of the melt-processed bulk sample, but has almost no effect on its thermoelectric power and thermal conductivity, within experimental error. The results of this study provide direct evidence that the heat flow in multi-granular melt-processed YBCO bulk samples should be virtually unaffected by the presence of grain boundaries in the material. © 2013 IOP Publishing Ltd. [less ▲]