Optical,Morphological, and Structural Properties of Tablets Obtained from Porous Silicon

Silicon - Porous silicon (PS) is a material with a great interest due to its optical (photoluminescent) and chemical (reactive surface) properties, for this reason, it is important to find new ways...     

A multi-objective approach for multi-material topology and shape optimization

An automated multi-material approach that integrates multi-objective Topology Optimization (TO) and multi-objective shape optimization is presented. A new ant colony optimization algorithm is presented and applied to solving the TO problem, estimating a trade-off set of initial topologies or distributions of material. The solutions found usually present irregular boundaries, which are not desirable in applications. Thus, shape parameterization of the internal boundaries of the design region, and subsequent shape optimization, is performed to improve the quality of the estimated Pareto-optimal solutions. The selection of solutions for shape optimization is done by using the PROMETHEE II decision-making method. The parameterization process involves identifying the boundaries of different materials and describing these boundaries by non-uniform rational B-spline curves. The proposed approach is applied to the optimization of a C-core magnetic actuator, with two objectives: the maximization of the attractive force on the armature and the minimization of the volume of permanent magnet material.     

A review: Energy recovery in batch processes

The implementation of batch processing has increased due to its intrinsic flexibility and adaptability. These are essential characteristics when it comes to producing high-value added materials such as agrochemicals, pharmaceuticals, specialty chemicals…the demand for which has grown in recent decades.Although industrial processes are highly diverse, a common feature to all is that they utilize fossil fuels as the energy source. The reliance on fossil fuels as a primary source of energy generates a negative impact on the environment. The implantation of renewable energies and efficient usage of energy has thus become crucial. Improving energy use could be achieved through advancements in plant machinery and the use of methodologies such as ‘process integration’.Process integration can be described as system oriented methods that could be used during the design and retrofit of industrial processes in order to obtain an optimal utilization of resources. The methods have traditionally focused on an efficient energy use, although recently process integration techniques cover other areas such as efficient use of raw materials, emission reduction and process operations. Energy integration tries to reach the optimization of heat, power, fuel and utilities.The consideration of energy integration complicates the process design and the generation of batch process design alternatives, so what is now required is the proposal and development of different approaches and methods oriented towards recovering energy in this kind of industrial process. Improving energy end-use efficiency will make it possible to reduce dependence on energy imports and bring about innovation and competitiveness.The aim of this work is report the main contributions that have been carried out in order to attain energy integration in batch processes, as well as different examples of applications that have shown the possibilities offered by the developed tools.     

Comparison of different models employed to describe the z-scan curves for thick nonlinear optical media

A model that considers a photoinduced lens with a focal length dependent on a real power of the incident beam radius is compared with other reported models employed to describe the z-scan curves for thick media. It is demonstrated that this model is equivalent to that used to describe z-scan curves for thin nonlocal nonlinear media; then an extension is made for thick nonlocal nonlinear media. A comparison is made with other models to obtain z-scan curves for thick media. It is demonstrated that, under the same conditions, remarkable differences can be found in the simulated z-scan curves.     

Normal State Resistivity of Underdoped YBa2Cu3Ox Thin Films and La2-xSrxCuO4 Ultra-Thin Films under Epitaxial Strain

The normal state resistivity of high temperature superconductors can be probed in the region below T _c by suppressing the superconducting state in high magnetic fields. Here we present the normal state properties of YBa ₂ Cu ₃ O _x thin films in the underdoped regime and the normal state resistance of La _2-x Sr _x CuO ₄ thin films under epitaxial strain, measured below T _c by applying pulsed fields up to 60 T. We interpret these data in terms of the recently proposed 1D quantum transport model with the 1D paths corresponding to the charge stripes.     

Lipase-catalyzed synthesis of pungent capsaicin analogues

Pungency in peppers (Capsicum spp.) is a sensation produced by a group of molecules known as capsaicinoids. Capsaicin has been reported as the capsaicinoid with the strongest pungency. Based on the molecular structure of capsaicin the enzymatic synthesis and pungent properties of structural analogues was investigated. These analogues were based on modification of the length of the acyl chain (from C4 to C16) and the chemical substituents of the aromatic ring (–OH and –OCH₃). The syntheses were carried out in 2-methyl-2-butanol with lipase B of Candida antarctica, with conversions ranging from 83% to 97.5%. The initial reaction rates were not significantly influenced by the nature of acyl-donor but rather by the substituents in the aromatic ring of the evaluated amines. The relative pungency of 10 capsaicin analogues was sensorially evaluated, using a sensory method for relative pungency. All the compounds were tested at a dose equivalent to 20 times the threshold capsaicin concentration. Two analogues were found pungent; the vanillylamides of caprylic (C-8) and capric (C-10) acids, showing a relative pungency of 66% and 36%, respectively, while the vanillylamides of caproic (C-6) and lauric (C-12) acids had a very low relative pungency (2.1% and 1.2%, respectively). From these results structural features related to pungency are discussed.     

Seismic Soil-Pile-Structure Interaction Experiments and Analyses

A dynamic beam on a nonlinear Winkler foundation (or “dynamic p-y”) analysis method for analyzing seismic soil-pile-structure interaction was evaluated against the results of a series of dynamic centrifuge model tests. The centrifuge tests included two different single-pile-supported structures subjected to nine different earthquake events with peak accelerations ranging from 0.02 to 0.7g. The soil profile consisted of soft clay overlying dense sand. Site response and dynamic p-y analyses are described. Input parameters were selected based on existing engineering practices. Reasonably good agreement was obtained between calculated and recorded responses for both structural models in all earthquake events. Sensitivity of the results to dynamic p-y model parameters and site response calculations are evaluated. These results provide experimental support for the use of dynamic p-y analysis methods in seismic soil-pile-structure interaction problems.     

Dynamic Experiments and Analyses of a Pile-Group-Supported Structure

Experimental data on the seismic response of a pile-group-supported structure was obtained through dynamic centrifuge model tests, and then used to evaluate a dynamic beam on a nonlinear Winkler foundation (BNWF) analysis method. The centrifuge tests included a structure supported on a group of nine piles founded in soft clay overlying dense sand. This structure was subjected to nine earthquake events with peak accelerations ranging from 0.02 to 0.7g. The centrifuge tests and dynamic analysis methods are described. Good agreement was obtained between calculated and recorded structural responses, including superstructure acceleration and displacement, pile cap acceleration and displacement, pile bending moment and axial load, and pile cap rotation. Representative examples of recorded and calculated behavior for the structure and soil profile are presented. Sensitivity of the dynamic BNWF analyses to the numerical model parameters and site response calculations are evaluated. These results provide experimental support for the use of dynamic BNWF analysis methods in seismic soil-pile-structure interaction problems involving pile-group systems.     

Urea treatment of whole‐crop triticale at four growth stages: effects on chemical composition and on in vitro digestibility of cell wall

The objective of this study was to evaluate the preservative and upgrading potential of urea added to whole‐crop triticale. Triticale, harvested at different growth stages according to Feekes' scale (10.51, 10.54, 11.1 and 11.2), was ensiled with four levels of urea (0, 30, 60 and 90 g kg^?1 dry matter (DM)) and stored in plastic bags for 60 days. Data were analysed as a factorial design with growth stage and urea level as the main factors. Urea was extensively hydrolysed (more than 90% of added urea). Urea breakdown was not affected by urea level (P > 0.05) but decreased significantly with growth stage (P < 0.001). Microbial activity measured by pH, volatile fatty acid production and total non‐structural carbohydrate concentration was significantly reduced by the urea level. Urea treatment significantly (P < 0.001) increased water‐soluble and ammonium nitrogen; more than 85% of the added nitrogen was retained. Application of urea at a rate of 60 and 90 g kg^?1 DM significantly (P < 0.05) reduced the neutral detergent fibre (NDF) content and increased (P < 0.05) the NDF and acid detergent fibre in vitro digestibility. Whole‐crop triticale harvested at later growth stages (approximately 60% DM) can be effectively preserved and upgraded by ensiling with 60–90 g urea kg^?1 DM. Copyright © 2006 Society of Chemical Industry