On finite-element implementation strategies of Schapery-type constitutive theories

This paper presents two new strategies for implementing Schapery-type nonlinearly viscoelastic constitutive theories into finite element codes. The first strategy uses the original differential equations that lead to the integral formulation of Schapery-type constitutive theories and Finite Difference (FD) schemes. This strategy is quite different from all the other strategies found in the literature. The second strategy is an improvement of recursive strategies, used by many authors, based on the integral formulation of the constitutive theory. The performances of the new algorithms are compared with those of existing strategies for various load histories and nonlinearities. It is shown that the newly developed strategy based on FD schemes can exhibit quadratic convergence rate when one time step is stored and 4th order convergence rate when two time steps are stored, which is a major improvement over the recursive strategies.     

In situ pulsed-field gradient NMR determination of the size of oil bodies in vegetable seeds. Analysis of the effect of the gradient pulse length

We report a pulsed-field gradient NMR study of the size of the oil bodies in lettuce seeds. The pulsed-field gradient spin-echo method (PFGSE) was applied to measure the self-diffusion coefficient of triacylglycerol molecules (TAG) inside the oil bodies. The confined nature of TAG diffusion is used to determine the size dispersion of the oil bodies. At long diffusion time, we measure a spin-echo attenuation that is related to the form factor of the confining volumes in the reciprocal q space, where q is proportional to the product of the gradient intensity and the length of the pulse gradient. Specific care was taken in analyzing the influence of the gradient pulse length delta on the shape of the PFGSE decay in order to construct the function corresponding to the short gradient pulse approximation (SGP). The SGP model gives an analytical framework for the PFGSE signal that enables the size distribution of the oil bodies to be determined. The SGP function was unambiguously obtained by varying the gradient pulse length delta in order to linearly extrapolate at delta = 0 the SGP limit. In this work, we also consider the Gaussian phase distribution (GPD) assumption that is often used to analyze confined diffusion experiments. Although the GPD assumption is known to be inaccurate in predicting the fine structure of the PFGSE function in q space, we point out that in the present case it can be used to take into account the finite value of delta. A log-normal distribution of the radius values was assumed in simulating the PFGNMR experiments since this type of distribution is observed in vegetable seeds by transmission electronic microscopy. From a practical and experimental standpoint, the NMR measurements reported here require no specific treatment of the seeds and the size of oil bodies is determined "in situ" on seeds poured into the NMR tube.     

Efficient behavior learning in human–robot collaboration

We present a novel method for a robot to interactively learn, while executing, a joint human–robot task. We consider collaborative tasks realized by a team of a human operator and a robot helper that adapts to the human’s task execution preferences. Different human operators can have different abilities, experiences, and personal preferences so that a particular allocation of activities in the team is preferred over another. Our main goal is to have the robot learn the task and the preferences of the user to provide a more efficient and acceptable joint task execution. We cast concurrent multi-agent collaboration as a semi-Markov decision process and show how to model the team behavior and learn the expected robot behavior. We further propose an interactive learning framework and we evaluate it both in simulation and on a real robotic setup to show the system can effectively learn and adapt to human expectations.     

Farmers’ perceptions of irrigation and constraints on rice production in Benin: a stakeholder-consultation approach

ABSTRACT

This article examines rice farmers’ perceptions of irrigation and constraints on rice production in the municipality of Malanville, Benin. Farmers’ positive perceptions of irrigation include the use of irrigation for insurance against drought, crop yield improvement, higher income, food security and poverty reduction. Analysis of constraints reveals that farmers face major constraints such as lack of agricultural credit, poor access to production inputs, inadequate knowledge of water resources management, poor access to agricultural information and markets, and flooding of fields. Specific constraints in the irrigation scheme of Malanville include the high cost of irrigation and unavailability of water.     

A deep reinforcement learning framework for continuous intraday market bidding

Machine Learning - The large integration of variable energy resources is expected to shift a large part of the energy exchanges closer to real-time, where more accurate forecasts are available. In...     

The security of databases: the Access case

Nowadays, more and more companies have to use databases in which they store their essential or confidential data for the society like client lists, product specifications, stock situations, etc.. Such pieces of data are the heart of a company and have to be protected. In fact, in the context of economic intelligence, getting such information is quite interesting for competitors who want to know how rival companies work for example. Databases need software to be managed. There is a variety of software, called database management system, which is able to manage database like MySQL, Oracle Database, Microsoft Access, etc... This paper will focus on Microsoft Access 2010 64 bits which is part of the Microsoft Office 2010 suite. Microsoft Access is currently used by small and medium enterprises (SMEs) who have subcontracted the creation of their database to specialized companies. SMEs represent a huge part of the economic area and could be an interesting target because of the large range of activities it gather. This technical paper analyses the Access Security and explains how an attacker could hijack an Access database in order to steal information or to perform malicious actions on the targeted computer. It deals with macro-viruses, still present after many years, and give then the possibility to use them to insert major security weaknesses into Access databases.