Aqueous Heck Arylation of Acrolein Derivatives: The Role of Cyclodextrin as Additive

Heck arylation of acrolein dialkyl acetal with (hetero)-aryl halides in water catalyzed by solid palladium catalysts and in presence of cyclodextrins is reported. Depending on the nature of the base, either cinnamaldehyde or 3-aryl propionic ester is obtained. It was shown that the presence of cyclodextrins in the reaction media increased the reaction rate as well as the stability of the palladium species.     

Robustness analyses of numerical simulation of fusion welding NeT-TG1 application: “Single weld-bead-on-plate”

This study contributes to the NeT-TG1 European Network formed in 2002. The aim of this study is to predict, by numerical simulation, the residual stresses generated in a test plate by the fusion welding process. The experiment consisted in the deposit of a weld bead along the longitudinal centre-line of an austenitic 316L plate using an automatic Tungsten Inert Gas (TIG) welding process with 316L filler material. During and after thermal cycle, a large quantity of measurement data is obtained that serve to develop a comparison with the results of different numerical models. The comparative thermal and mechanical analysis allows assessment for the general ability of the numerical models to describe the structural behaviour. The importance of the heat-input rate and material characteristics is also investigated. The residual stresses were predicted by the finite element method using the program Code_Aster of EDF and SYSWELD of ESI-GROUP. Finally the numerical results are validated by comparison with experimentally measured data.     

Beyond the end-consumer: how would improvements in residential energy efficiency affect the power sector in Saudi Arabia?

Energy efficiency in buildings has garnered significant attention in Saudi Arabia. This paper outlines the potential effects of higher residential efficiency on electricity load profiles in the Kingdom. It further presents the associated benefits that could have been realized by the local utilities in 2011. To perform the analysis, we designed an integrated methodology in which an engineering-based residential electricity demand model is used within an economic equilibrium framework. The modeling approach allows us to capture the physical interactions arising from higher efficiency and the structural changes that could occur in the economy beyond the end-consumers. Raising the average air-conditioner energy efficiency ratio (EER) to 11 British thermal unit (BTU)/(Wh) from its 2011 average would have saved 225,000 barrels/day of crude oil in electricity generation. Alternatively, increasing the share of insulated homes from 27 to 64 % would have allowed the power sector to lower its use of the fuel by 158,000 barrels/day. Combining both measures in a single simulation yields incremental yet not additive reductions. All alternative scenarios reduce costs to the utilities and improve the average thermal efficiency for the electricity generated. The studied efficiency options shift the load curve downward during the peak load segment when the least efficient turbines would be used. We additionally show how efficiency improvements in end-uses can affect the decisions of other sectors in the economy.     

Nested saturation based control of an actuated knee joint orthosis

Wearable robots have opened a new horizon for assistance and rehabilitation of dependent/elderly persons. The present study deals with the control of an actuated lower limb orthosis at the knee joint level. The dynamics of the shank–foot–orthosis system are expressed through a nonlinear second order model taking into account viscous, inertial and gravitational properties. Shank–foot–orthosis system parameters are identified experimentally. Since the underlying dynamic model is nonlinear, a robust control strategy is needed to guarantee an accurate and precise movement generation. The proposed control strategy ensures, at the same time, the stability of the closed-loop system. A bounded control torque is applied to guarantee the asymptotic stability of the shank–foot–orthosis. The generated control respects the physical constraints imposed by the system. The effectiveness of the proposed control strategy is shown in real-time in terms of stability, position tracking performances and robustness with respect to identification errors and external disturbances.     

Bicriteria sequencing for just-in-time mixed-model assembly lines

Under a Just-In-Time (JIT) pull system the sequencing of products requires the satisfaction of two main goals: (1) keeping a constant rate of usage of parts, and (2) smoothing the workload at work stations to avoid line stoppages. By using a practical observation related to JIT delivery systems we propose a two-step approach, where in the first step we consider only goal (1) by applying a benchmark heuristic. In the second step we focus on goal (2), by investigating the effectiveness of a spacing-constraint based approach, commonly used in the automotive industry, in comparison with a more general time-based one. We designed and conducted a simulation experiment based on the practical situation of final assembly lines and we found that the benchmark heuristic represents an appropriate choice for step one (based on a new performance measure that represents a lower bound on variation in parts utilization). For the second step, related to workload smoothing, the spacing-constraint based method presents better achievement than the time-based one.