Finite element model for beef chilling using CFD-generated heat transfer coefficients

A combined model of the beef chilling process is presented, in which computational fluid dynamics (CFD) was used to estimate the local heat and mass transfer coefficients, assuming uniform surface temperatures, and a set of 2-D finite element grids was used to solve the heat transfer equation in the product, which has an elongated shape. Another set of 1-D grids was used to solve the water transport equation near the surface of the meat. The surface transfer coefficients were calculated for various combinations of air orientations and speeds, and summarised in a set of regression equations. The model was verified by existing and new data on heat load, temperatures, weight loss and surface water activity.     

Comparative study of modeling and identification of the pneumatic artificial muscle (PAM) manipulator using recurrent neural networks

The paper deals with the PAM manipulator modeling and identification based on autoregressive recurrent neural networks. For the first time, the most powerful types of neural-network-based nonlinear autoregressive models, namely, NNARMAX, NNOE and NNARX models, will be applied comparatively to the PAM manipulator identification. Furthermore, the evaluation of different nonlinear neural network auto-regressive models of the PAM manipulator with different number of neurons in hidden layer is completely discussed. On this basis, the merits of each identified model of the highly nonlinear PAM manipulator have been analyzed and compared. The results show that the nonlinear NNARX model yields better performance and higher accuracy than the other nonlinear NNARMAX and NNOE model schemes. These results can be applied to model and identify not only the PAM manipulator but also to control other nonlinear and time-varying industrial systems.     

Support Mechanisms of Rammed Aggregate Piers. I: Experimental Results

This paper is the first of a two-part series investigating the mechanical behavior of rammed aggregate pier (RAP) groups supporting isolated rigid footings. The first paper presents the experimental test results from instrumented load tests performed on two different 2.3?m square reinforced concrete footings supported by four 0.76?m diameter RAPs of two different pier lengths—2.8 and 5.1?m. Comparisons are made to load tests performed on three isolated RAPs of the same diameter and lengths. Instrumentation consisted of total stress cells, inclinometers, and tell-tale reference plates. Soil conditions at the test site were evaluated using various in situ testing techniques and consist of relatively uniform soft alluvial clay overlain by a 1-m-thick desiccated layer. Interpretations of the test results focused on load-deformation behaviors of the isolated piers and pier groups, group efficiencies in terms of settlement and bearing capacity, stress concentrations as a function of applied load at the top of the piers, and stress transfer with depth.     

Preparation, characterization and in vitro antimicrobial activity of ampicillin-loaded polyethylcyanoacrylate nanoparticles

In this paper, the experimental conditions for preparing ampicillin-loaded polyethylcyanoacrylate (PECA) nanoparticles are described. The effects of drug concentration and surfactant type in the polymerization medium on the particle size distribution and loading capacity were studied. The results of these studies show that only the type of surfactant has an impact on the nanoparticle dimensions. The release rate of ampicillin from PECA nanoparticles at pH 7.4 (extracellular value pH) performed either with and without esterases, show that the drug release is considerably increased in the presence of these exzymes. The results of drug release study at pH 1.1 (simulated gastric juice) are very interesting. This study has evidenced that the 70% of ampicillin is released quickly, while the remaining fraction is firmly incorporated in nanoparticles. The released ampicillin is quickly degraded in acid medium while the entrapped fraction is protected from acid degradation and afterwards, when nanoparticles reach the small intestine, can be readily released in the presence of esterases. This result could be exploited for the oral administration of the ampicillin-PECA system. Finally, studies of antimicrobial activity of prepared systems evidenced that ampicillin-loaded PECA nanoparticles exhibit an activity equal or higher than the free drug.     

A novel acrylic copolymer for a poly(alkenoate) glass-ionomer cement

The interest in the clinical use of polyalkenoate cements stems mainly from their behavior as bioactive adhesive materials with therapeutic action. Glass-ionomer cements set by an acid-base reaction between a degradable glass and a poly(alkenoic acid) and the therapeutic action is related to the release of fluoride ions which are present in the hardened cement that show a sustained release over years, responsible for caries inhibition in teeth. Conventional glass-ionomers, however, suffer from some disadvantages such as short working time, initial moisture sensitivity and prone to desiccation after setting and are generally brittle. In the present study, a poly(alkenoic acid) copolymer was synthesized based on acrylic acid and 2-hydroxyethylmethacrylate (HEMA) using azobisisobutyronitrile as the initiator and characterized. The acid–base reaction was carried out by reacting aqueous solutions of the new copolymer (40 and 60%) with a commercial aluminofluorosilicate glasses as used in conventional glass-ionomer cements. The results showed that the copolymer of HEMA and acrylic acid was a viable poly(alkenoic) acid for formation of glass-ionomer cements.     

Improvement in transient piezoelectric responses of NDE transceivers using selective damping and tuning networks

NDE ultrasonic applications for quality control purposes, based on piezoelectric devices working as pulsed ultrasonic probes, usually include some tuning circuit either across the pulser output connectors or close to the piezoelectric probe electrodes. Classic criteria to determine tuning parameters in ultrasonic transducers do not perform very well in transient regime under the typical electrical conditions and peculiar output impedances of the required high-voltage pulsers. In most practical situations, the tuning values are manually adjusted in specific circuits for each NDE case, testing each channel of a multiprobe inspection system to find the best sensitivity. In this paper, the positive influences of certain selective damping and tuning networks on the time and frequency behaviors of NDE piezoelectric transceivers are analyzed in detail. Different waveforms and spectra of received ultrasonic signals are comparatively evaluated for different real tuning conditions, after passing through two ultrasonic processes linked in cascade: a transmitter of industrial type and a broad-band ultrasonic receiver. Piezoelectric transducer impedances, transduction transfer functions, and HV output spikes from a piezoelectrically loaded NDE pulser, are computed, to identify separately the influence of each stage. In order to improve amplitude and axial resolution in the received transient responses, relative contributions from emission and reception tuning networks are individually evaluated for a particular NDE two-stage piezoelectric channel. Also shown are the final experimental results relative to the ultrasonic test pulse and detected in a through-transmission NDE configuration, gradually improved by using distinct tuning levels.     

Surface induced reactivity for titanium by ion implantation

Calcium and phosphorus storage in a thin layer of titanium surface was achieved by ion implantation. We study the reactivity of this surface in response to a hydrothermal treatment. The incipient implanted species are observed to convert to Ca²⁺ and PO₄ ^3-, the precursors for generating calcium phosphate polymorphs. Hydroxyapatite is formed from these precursors by an interface-liquid mediated mineralization preceded by the hydrolysis of oxygen compounds of Ca and P from the solid phase. The morphology and organization of apatite mineral is controlled by the fluid dynamics reflecting the surface remodeling to adapt to the available local environment. Exposed to calcium and phosphate ion containing solution, the hydrothermally treated surface templates hydroxyapatite deposition. Ca and P implanted Ti surface was shown to be chemically and morphologically actively involved in the interfacial reactions. ©2000 Kluwer Academic Publishers     

A linear response Monte Carlo algorithm for inversion layers and magnetotransport

Certain simulation problems require the solution of the Boltzmann equation for small driving forces. Due to the bad signal to noise ratio of the standard Monte Carlo algorithm in the linear regime these simulations are extremely CPU intensive. A linear response Monte Carlo algorithm is proposed which is orders of magnitude faster than the standard approach. It is used to extract transport parameters from magnetotransport measurements and to match semiempirical inversion layer models to experimental data.