Intermediate product selection and blending in the food processing industry

This study addresses a capacitated intermediate product selection and blending problem typical for two-stage production systems in the food processing industry. The problem involves the selection of a set of intermediates and end-product recipes characterising how those selected intermediates are blended into end products to minimise the total operational costs under production and storage capacity limitations. A comprehensive mixed-integer linear model is developed for the problem. The model is applied on a data set collected from a real-life case. The trade-offs between capacity limitations and operational costs are analysed, and the effects of different types of cost parameters and capacity limitations on the selection of intermediates and end-product recipes are investigated.     

Evaluation of the validity of the scalar approximation in optical wave propagation using a systems approach and an accurate digital electromagnetic model

The cause and amount of error arising from the use of the scalar approximation in monochromatic optical wave propagation are discussed using a signals and systems formulation. Based on Gauss’s Law, the longitudinal component of an electric field is computed from the transverse components by passing the latter through a two input single output linear shift-invariant system. The system is analytically characterized both in the space and frequency domains. For propagating waves, the large response for the frequencies near the limiting wave number indicates the small angle requirement for the validity of the scalar approximation. Also, a discrete simulator is developed to compute the longitudinal component from the transverse components for monochromatic propagating electric fields. The simulator output helps to evaluate the validity of the scalar approximation when the system output cannot be analytically calculated.     

A review: Fibre metal laminates,background, bonding types and applied test methods

During the past decades, increasing demand in aircraft industry for high-performance, lightweight structures have stimulated a strong trend towards the development of refined models for fibre-metal laminates (FMLs). Fibre metal laminates are hybrid composite materials built up from interlacing layers of thin metals and fibre reinforced adhesives. The most commercially available fibre metal laminates (FMLs) are ARALL (Aramid Reinforced Aluminium Laminate), based on aramid fibres, GLARE (Glass Reinforced Aluminium Laminate), based on high strength glass fibres and CARALL (Carbon Reinforced Aluminium Laminate), based on carbon fibres. Taking advantage of the hybrid nature from their two key constituents: metals (mostly aluminium) and fibre-reinforced laminate, these composites offer several advantages such as better damage tolerance to fatigue crack growth and impact damage especially for aircraft applications. Metallic layers and fibre reinforced laminate can be bonded by classical techniques, i.e. mechanically and adhesively. Adhesively bonded fibre metal laminates have been shown to be far more fatigue resistant than equivalent mechanically bonded structures.     

An upside-down normal loss function-based method for quality improvement

Traditional measures of process quality do not offer much information on how much better or worse a process is when finding optimal settings of a given problem. The upside-down normal loss function (UDNLF) is a weighted loss function that provides a more reasonable risk assessment to the losses of being off-target in product engineering research. The UDNLF can be used in process design and optimization to accurately reflect and quantify the losses associated with the process in a way which minimizes the expected loss of the upside-down normal (UDN). The function has a scale parameter which can be adjusted by the practitioners to account for the actual percentage of materials failing to work at specification limits. In this article, the ‘target is best’ case is addressed to estimate the expected loss of UDN due to variation from target in the robust process design and response surface modelling context. An approach is proposed to find the control factor settings of a system by directly minimizing the expected loss. The procedure and its merits are illustrated through an example.     

Novel ZA27/B4C/Graphite Hybrid Nanocomposite-Bearing Materials with Enhanced Wear and Corrosion Resistance

Metallurgical and Materials Transactions A - In this study, nanosized B4C and graphite-reinforced ZA27 matrix hybrid nanocomposites were produced with mechanical milling followed by hot pressing....     

The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading

Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending (R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation.     

Controlled synthesis of transition metal/conducting polymer nanocomposites

A novel displacement reaction has been observed to occur between conducting polymers (CP) and metal salts which can be used to fabricate nanostructured CP-metal composites in a one-pot manner. Vanadium pentoxide (V (2)O(5)) nanofiber is used during the synthesis as the reactive seeds to induce the nanofibril CP-metal network formation. The CP-metal nanocomposites exhibit excellent sensory properties for hydrogen peroxide (H(2)O(2)) detection, where both high sensitivity and a low detection limit can be obtained. The sensory performance of the CP-metal composite can be further enhanced by a facile microwave treatment. It is believed that the CP-metal nanofibril network can be converted to a carbon-metal network by a microwave-induced carbonization process and result in the sensory enhancement.     

Formability of Ultrafine-Grained Interstitial-Free Steels

The stretch formability of ultrafine-grained (UFG) interstitial-free steel (IF-steel) produced by equal-channel angular extrusion/pressing (ECAE/P) via various strain paths was investigated with a miniaturized Erichsen test. A coarse-grained (CG) sample demonstrated high formability with an Erichsen index (EI) of 4.5 mm. Grain refinement by ECAE decreased the formability, but increased the required punch load (F _EI) depending on the applied strain paths. The EI values were 0.35, 2.90, and 3.91 mm for 8A-, 8Bc-, and 8C-processed samples, respectively. Decrease in the biaxial stretch formability was attributed to the limited strain-hardening capacity of the UFG microstructure. Also, the grain morphology of the UFG microstructure was found to be very influential on stretch formability. Heavily elongated grain morphology in the 8A-processed microstructure resulted in the lowest formability due to the increased cracking tendency through elongated grain boundaries. However, the UFG microstructures with equiaxed grains obtained after 8C and 8Bc ECAE resulted in better formability compared to 8A. The UFG microstructure reduced the roughness (orange peel effect) of the free surface of the biaxial stretched samples by decreasing the non-uniform grain flow leading to the so-called orange peel effect. It should be noted that the strength and ductility values gained from uniaxial tensile tests are not comparable directly to the EI and F _EI values determined from the Erichsen tests. Finally, it is important to emphasize that the UFG microstructure produced by a suitable strain path leading to equiaxed grains below 1 μm could be highly deformed even under multiaxial stress conditions.     

Out of Context: NMDA Receptor Antagonism in the Avian 'Prefrontal Cortex' Impairs Context Processing in a Conditional Discrimination Task.

Processing of context information is implicated in prefrontal functions as response selection or attention. N-methyl-D-aspartate (NMDA) receptors in the mammalian prefrontal cortex (PFC) and in the nidopallium caudolaterale (NCL) of birds, the avian functional equivalent of the PFC, are involved in learning, which also requires processing of context. The authors investigated the role of NMDA receptors in the pigeon (Columba livia) NCL for context processing and response selection in a simultaneous-matching-to-sample task with 2 trial types, requiring either processing of context information, delivered by a conditional stimulus (context dependent), or only recall of a stimulus-response association (fixed response). The competitive NMDA antagonist DL-2-amino-5-phosphonovaleric acid impaired performance only in context-dependent trials. Therefore, NMDA receptors in the avian PFC participate in response selection requiring context processing rather than in response selection per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)