Weakly regular Einstein-Euler spacetimes with Gowdy symmetry. The global areal foliation

We consider weakly regular Gowdy-symmetric spacetimes on T3 satisfying the Einstein-Euler equations of general relativity, and we solve the initial value problem when the initial data set has bounded variation, only, so that the corresponding spacetime may contain impulsive gravitational waves as well as shock waves. By analyzing, both, future expanding and future contracting spacetimes, we establish the existence of a global foliation by spacelike hypersurfaces so that the time function coincides with the area of the surfaces of symmetry and asymptotically approaches infinity in the expanding case and zero in the contracting case. More precisely, the latter property in the contracting case holds provided the mass density does not exceed a certain threshold, which is a natural assumption since certain exceptional data with sufficiently large mass density are known to give rise to a Cauchy horizon, on which the area function attains a positive value. An earlier result by LeFloch and Rendall assumed a different class of weak regularity and did not determine the range of the area function in the contracting case. Our method of proof is based on a version of the random choice scheme adapted to the Einstein equations for the symmetry and regularity class under consideration. We also analyze the Einstein constraint equations under weak regularity.Comment: 36 page

The equations of elastostatics in a Riemannian manifold

To begin with, we identify the equations of elastostatics in a Riemannian manifold, which generalize those of classical elasticity in the three-dimensional Euclidean space. Our approach relies on the principle of least energy, which asserts that the deformation of the elastic body arising in response to given loads minimizes over a specific set of admissible deformations the total energy of the elastic body, defined as the difference between the strain energy and the potential of the loads. Assuming that the strain energy is a function of the metric tensor field induced by the deformation, we first derive the principle of virtual work and the associated nonlinear boundary value problem of nonlinear elasticity from the expression of the total energy of the elastic body. We then show that this boundary value problem possesses a solution if the loads are sufficiently small (in a sense we specify).Comment: 43 page

Supplementary Feeding of Grazing Dairy Cows

The objective of this paper was to consider the effect of supplementary feeding of grazing dairy cows on dry matter intake (DMI), milk production and milk composition. Accurate estimations of total DMI and pasture DMI are important to the management of dairy grazing systems. The intakes of dry matter (DM) and net energy-NEL are lower on the pasture-only diet compared with cows supplementary fed with concentrate. Many pasture factors affect DMI, including pregrazing pasture mass and pasture allowance. Milk production of high producing grazing dairy cows in early lactation increases linearly as the amount of concentrate increases to 10 kg DM/day with a milk response of 1 kg milk/kg concentrate. In late lactation, increases are with a lower milk response per kilogram of supplemented concentrate. With the amount of concentrate supplementation, milk fat and protein yield increase while milk fat percentage decreases. Supplementation with rumen undegradable protein (RUP) is important for meeting requirements of grazing dairy cows, because the pasture has high ruminal crude protein (CP) degradability. Corn silage supplementation to grazing cows may increase milk production if pasture offered is restricted, but if pasture is offered ad libitum milk production does not change or can decrease. Supplementation of ruminally inert fat could have positive effect on milk production with concentrate supplemented at a lower rate

Data Gained from Smart Services in SMEs–Pilot Study

Nowadays, manufacturing companies increasingly invest in servitization by adopting ‘smart services’ enabled by connected product-service systems enabling data exchange between the customer and the service provider. Managing the transition toward smart services is not easy, especially among SMEs as many businesses struggle with lack of money, insufficient digital technologies, unskilled employees or gathering and using the proper data. The research presented in this paper is divided into two parts. The quantitative part focuses on researching possible correlations between business performance and the use of company IT systems among sixty Czech electrotechnical SMEs. The other part consists of a qualitative multi-case study and was conducted among seven Czech electrotechnical SMEs which have already started with smart service development. The findings indicate that companies gather and use the data in very different ways. They provide information to their customers, but also use information for themselves. The study is unique in highlighting the problems of smart services in small and medium manufacturers. Moreover, it investigates the gathering and the data usage gained from smart services in SMEs.Nowadays, manufacturing companies increasingly invest in servitization by adopting ‘smart services’ enabled by connected product-service systems enabling data exchange between the customer and the service provider. Managing the transition toward smart services is not easy, especially among SMEs as many businesses struggle with lack of money, insufficient digital technologies, unskilled employees or gathering and using the proper data. The research presented in this paper is divided into two parts. The quantitative part focuses on researching possible correlations between business performance and the use of company IT systems among sixty Czech electrotechnical SMEs. The other part consists of a qualitative multi-case study and was conducted among seven Czech electrotechnical SMEs which have already started with smart service development. The findings indicate that companies gather and use the data in very different ways. They provide information to their customers, but also use information for themselves. The study is unique in highlighting the problems of smart services in small and medium manufacturers. Moreover, it investigates the gathering and the data usage gained from smart services in SMEs

An ontology supported risk assessment approach for the intelligent configuration of supply networks

As progress towards globalisation continues, organisations seek ever better ways with which to configure and reconfigure their global production networks so as to better understand and be able to deal with risk. Such networks are complex arrangements of different organisations from potentially diverse and divergent domains and geographical locations. Moreover, greater focus is being put upon global production network systems and how these can be better coordinated, controlled and assessed for risk, so that they are flexible and competitive advantage can be gained from them within the market place. This paper puts forward a reference ontology to support risk assessment for product-service systems applied to the domain of global production networks. The aim behind this is to help accelerate the development of information systems by way of developing a common foundation to improve interoperability and the seamless exchange of information between systems and organisations. A formal common logic based approach has been used to develop the reference ontology, utilising end user information and knowledge from three separate industrial domains. Results are presented which illustrate the ability of the approach, together with areas for further work

Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo

Meeting Abstracts: Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo Clearwater Beach, FL, USA. 9-11 June 201

Modèles de fluides et de corps élastiques sur des espaces courbes

In this thesis, we consider some problems related to Einstein-Euler equations of general relativity and to models of nonlinear elasticity in a curved space. In the first part we study the evolution of a perfect fluid in a Gowdy symmetric spacetime satisfying Einstein-Euler equations. We solve the corresponding initial value problem for a given initial data set of bounded variation. Analyzing both future expanding and future contracting spacetimes, we establish the existence of a global foliation by spacelike hypersurfaces when the time coordinate is chosen to coincide with the area of symmetry orbits. The proof relies on a version of the Glimm scheme adapted to the symmetry and the regularity class under consideration. In the future contracting case, we give geometric conditions on the initial data that ensure that the area function asymptotically approaches zero. The second part is dedicated to the study of equations of nonlinear elasticity within the framework of Riemannian manifolds. They generalize, in a natural way, the equations of classical elasticity set in a three-dimensional Euclidean space. Our approach is based on the principle of least action, stating that the deformation of the elastic body arising in response to given external forces minimizes the total energy of the elastic body. From there, we first derive the principle of virtual work and then the corresponding boundary value problem. Finally, we show that the latter admits a solution provided the external forces are sufficiently small.Dans cette thèse, nous abordons quelques problèmes liés aux équations d'Einstein-Euler de la relativité générale et aux modèles d'élasticité non linéaire sur des espaces courbes. Dans la première partie, nous étudions l'évolution d'un fluide parfait dans un espace-temps courbe à symétrie de Gowdy, satisfaisant aux équations d'Einstein-Euler. Nous cherchons à résoudre le problème de Cauchy correspondant pour une donnée initiale à variation bornée. Analysant à la fois les espace-temps en expansion et les espace-temps en contraction, nous démontrons l'existence d'un feuilletage global lorsque la coordonnée de temps coïncide avec l'aire des orbites de symétrie. La démonstration repose sur le schéma de Glimm adapté à la symétrie et la classe de régularité considérées. Dans le cas des espace-temps en contraction, nous donnons les conditions géométriques sur la donnée initiale assurant que la fonction d'aire tend asymptotiquement vers zéro. La deuxième partie est consacrée à l'étude des équations de l'élasticité non-linéaire dans le cadre des variétés riemanniennes. Ces dernières généralisent de manière naturelle les équations de l'élasticité classique posées dans l'espace euclidien de dimension 3. Notre approche est basée sur le principe de moindre action qui affirme que la déformation du corps élastique sous l'action des forces extérieures minimise l'énergie totale du corps élastique. À partir de là, nous déduisons le principe des travaux virtuels, puis le problème aux limites correspondant. Enfin, nous démontrons que ce dernier admet une solution pourvu que les forces soient suffisamment petitesPARIS-BIUSJ-Mathématiques rech (751052111) / SudocSudocFranceF

The equations of elastostatics in a Riemannian manifold

Abstract To begin with, we identify the equations of elastostatics in a Riemannian manifold, which generalize those of classical elasticity in the three-dimensional Euclidean space. Our approach relies on the principle of least energy, which asserts that the deformation of the elastic body arising in response to given loads minimizes over a specific set of admissible deformations the total energy of the elastic body, defined as the difference between the strain energy and the potential of the loads. Assuming that the strain energy is a function of the metric tensor field induced by the deformation, we first derive the principle of virtual work and the associated nonlinear boundary value problem of nonlinear elasticity from the expression of the total energy of the elastic body. We then show that this boundary value problem possesses a solution if the loads are sufficiently small (in a sense we specify). Résumé Dans un premier temps, nous identifions leséquations de l'élastostatique dans une variété riemannienne, qui généralisent celles de la théorie classique de l'élasticité dans l'espace euclidien tridimensionnel. Notre approche repose sur le principe de moindre action, qui affirme que la déformation du corpsélastique sous l'action des forces externes minimise sur l'ensemble des déformations admissibles l'énergie totale du corpsélastique, définie comme la différence entre l'énergie de déformation et le potentiel des forces externes. Sous l'hypothèse que l'énérgie de déformation est une fonction du champ de tenseurs métriques induit par la déformation, on déduit dans un premier temps le principe des travaux virtuels et le problème aux limites associéà partir de l'expression de l'énergie totale du corpsélastique. On démontre ensuite que ce problème aux limites admet une solution si les forces externes sont suffisamment petites (en un sens que nous précisons)

Effect of feeding frequency on diurnal variation in plasma and urinary purine derivatives in steers

The diurnal changes in plasma concentration and urinary excretion of purine derivatives (PD) were examined in 4 steers given feed in 1 or 2 meals daily in 2, 18-day periods. In period 1, 2 steers were fed once daily (at 08.00 h) and the other 2 twice daily (at 08.00 and 16.00 h). In period 2, the treatments were switched. In the last 4 days of each period, plasma samples were taken from 08.00 to 24.00 h at 2 to 3-h intervals, and daily urine was collected in several 4 to 8-h periods. With once daily feeding, allantoin concentration in plasma varied from 0.90 to 1.07 of the daily mean and with twice daily feeding, from 0.97 to 1.05 of mean. The coefficient of variation (CV) for total variation was 0.14. In urine, the concentration and hourly excretion of PD varied with sampling times (P 0.05) but the ratio of PD to creatinine was relatively constant even for once-daily feeding (CV, 0.02 for measurements at different times). The CV for total variation in the ratio was 0.19. The results suggest that diurnal variation in plasma allantoin concentration and in the ratio of allantoin (or total PD) to creatinine are relatively small even for once daily feeding. It thus seems that these measurements in spot samples may be suitable for use as a simple index of microbial protein supply if they are correlated with the daily PD excretion. The results also indicate that measurements in samples of plasma and urine taken between 15.00 and 20.00 h tended to give a better representation of the daily mean