On the Use of Symbolic Analyzers in Circuit Synthesis

In this paper several examples of circuits obtained with an automatic synthesis algorithm will be shown. The algorithm, described in a companion paper [1] and outlined here for clarity, has been implemented in the Mathematica language. We applied the new algorithm to classical problems of inmittance synthesis, obtaining well known topologies and also non-reported structures. When the algorithm is applied to challenging new problems, novel and practically useful inmittances are synthesized.     

Improvement of resolution in equivalent currents reconstruction using Papoulis-Gerchberg algorithm and replicas of the spectrum

A new algorithm to increase the resolution in the reconstruction of equivalent currents from spherical near-field measurements is proposed. The algorithm obtains the non-visible part of the plane- wave spectrum used for the reconstruction. This is achieved by means of a band-limited extrapolation method, the Papoulis-Gerchberg algorithm, and the replication of the known part of the spectrum. The gain in resolution is from llambda in the method without the algorithm proposed, to 0.4-0.51 with this new algorithm. Results with real measurements are shown.     

Crystallization of a Polyamide 6/Montmorillonite Nanocomposite at Rapid Cooling

The crystallization behavior of a polyamide 6/organo‐modified montmorillonite (PA 6/OMMT) nanocomposite has been investigated by scanning chip calorimetry and wide‐angle X‐ray scattering, with emphasis placed on the evaluation of the effect of supercooling/cooling rate on the crystal/mesophase polymorphism of the PA 6 matrix. Presence of OMMT has negligible effect on the kinetics of formation of α‐crystals of PA 6 at low cooling rate while there is observed enhanced nucleation of γ‐mesophase on fast cooling. Furthermore, addition of OMMT leads to a distinct increase of the cooling rate required to completely vitrify the amorphous state. The performed experiments demonstrate that the nucleating effect of OMMT in PA 6/OMMT nanocomposites is of particular importance at cooling conditions relevant in polymer processing.

     

Method for assessing human resources management practices and organisational learning factors in a company under lean manufacturing implementation

The implementation of lean production systems is deemed essential for companies that wish to obtain high levels of competitiveness. There are several examples in the literature discussing the adoption of lean roadmaps; however, since such maps emphasise technical factors of lean change, the organisational learning (OL) process and human resources management (HRM) practices tend to be neglected. This article presents a method for assessing the impact of HRM practices and OL factors in a company under lean implementation. The method incorporates concepts of HRM and OL into lean implementation roadmaps, enabling a maturity analysis regarding dimensions of OL at different contextualisation levels, and allowing the proposition of improvements in HRM practices. The proposed method is illustrated in a case study from the automotive parts manufacturing sector.     

Statistical parameters of the indicating surface of natural reflectance for biaxial transparent media

Abstract

The optical properties are an important characteristic of a mineral. These properties can be studied with a photometer microscope using the indicating surface of natural reflectance (ISRN). Transparent uniaxial media have been studied. Biaxial transparent media, in the same way as uniaxial media, can be analysed by knowing the statistical parameters of the ISRN. To analyse these media, we need the expressions that relate these parameters to the refractive index of the incident medium and to the principal indices of the medium under observation.     

Precise determination of the zero-gravity surface figure of a mirror without gravity-sag modeling

The zero-gravity surface figure of optics used in spaceborne astronomical instruments must be known to high accuracy, but earthbound metrology is typically corrupted by gravity sag. Generally, inference of the zero-gravity surface figure from a measurement made under normal gravity requires finite-element analysis (FEA), and for accurate results the mount forces must be well characterized. We describe how to infer the zero-gravity surface figure very precisely using the alternative classical technique of averaging pairs of measurements made with the direction of gravity reversed. We show that mount forces as well as gravity must be reversed between the two measurements and discuss how the St. Venant principle determines when a reversed mount force may be considered to be applied at the same place in the two orientations. Our approach requires no finite-element modeling and no detailed knowledge of mount forces other than the fact that they reverse and are applied at the same point in each orientation. If mount schemes are suitably chosen, zero-gravity optical surfaces may be inferred much more simply and more accurately than with FEA.     

Comparison of experimental pressure drop data for two phase flows to prediction methods using a general model

In this paper, existing and new two phase pressure drop data are used to run an extensive comparison to predictive methods. The database used is for seven refrigerants (R22, R134a, R404A, R407C, R410A, R417A, and R507A) over a wide range of operating conditions. The procedure used for the comparison is a model of general validity since it is independent of the data reduction procedure. Four quoted methods and a new one by Moreno Quibén and Thome are used. The statistical analysis showed that the methods by Grönnerud and by Moreno Quibén and Thome are equally the best. Segregating the data by flow regimes and taking into account for the prediction of the data trends, the method by Moreno Quibén and Thome is able to give reliable predictions in all the range of vapour qualities, especially in the regions of the intermittent flow and dry-out.     

A comparison of HVAC systems for artwork conservation

The growing interest in Italy for its cultural heritage and the necessity for better conservation usually require that museums be provided with appropriate HVAC systems.

Control of indoor relative humidity must ensure that the vapour transfer between the materials and the ambient is such as to avoid mechanical, chemical and biological damage. Thus, it is necessary to balance the main thermal loads, that one due to the occupants in exhibition areas, subject to rapid change and directly proportional to the degree of overcrowding, and thermal load related to outdoor air.

A case study concerning a simulated modern museum is presented in this paper. Using the dynamic simulation code DOE 2.1 E and hourly climatic data (TRY), the operating costs of different all-air systems (also with dehumidification by adsorption) have been evaluated for exhibition areas and stock spaces, as well as system performance in controlling thermal-hygrometric ambient parameters.     

Air-coupled ultrasound: a novel technique for monitoring the curing of thermosetting matrices

A custom-made, air-coupled ultrasonic device was applied to cure monitoring of thick samples (7-10 mm) of unsaturated polyester resin at room temperature. A key point was the optimization of the experimental setup in order to propagate compression waves during the overall curing reaction by suitable placement of the noncontact transducers, placed on the same side of the test material, in the so-called pitch-catch configuration. The progress of polymerization was monitored through the variation of the time of flight of the propagating longitudinal waves. The exothermic character of the polymerization was taken into account by correcting the measured value of time of flight with that one in air, obtained by sampling the air velocity during the experiment. The air-coupled ultrasonic results were compared with those obtained from conventional contact ultrasonic measurements. The good agreement between the air-coupled ultrasonic results and those obtained by the rheological analysis demonstrated the reliability of air-coupled ultrasound in monitoring the changes of viscoelastic properties at gelation and vitrification. The position of the transducers on the same side of the sample makes this technique suitable for on-line cure monitoring during several composite manufacturing technologies.     

Clinical and biochemical alterations in rats treated with high doses of vitamin A

In the present work the effect of intramuscular administration of 30.000, 50.000 and 100.000 IU of vitamin A palmitate daily for seven days, respectively, on the liver enzyme activity in 45 white male Wistar rats, aged 12 weeks and weighing 180-200 g, have been studied. The group control was integrated by 15 healthy rats with similar characteristics (strain, gender, age and weight) to treated animals. Food and water consumption and body weights were recorded at the end of the experimental period. Rats were observed for clinical signs of toxicity. At the end of the study, rats were sacrificed under ether anesthesia. Liver samples were taken for the determination of enzyme activity. Administration of excess of vitamin A produced a significant (p < 0.05) increase in the content of liver vitamin A, determined diverse and variable clinical signs (such as, anorexia, loss of body weight, alopecia, conjunctivitis, external and internal hemorrhages, skin abnormalities and death) and increased (p < 0.05) the activity of the following enzymes: alanine aminotransferase, aspartate aminotransferase, acid maltase (acid alpha-1,4-glucosidase), acid proteases, lactate dehydrogenase and alkaline phosphatase while glucose-6-phosphatase, glycogen phosphorylase, alpha-amylase, cholinesterase and arginase decreased (p < 0.05) as compared with untreated controls. These changes depend on the doses given of vitamin A. In conclusion, our results provide evidence that short-term administration of high doses of vitamin A determined diverse and variable clinical signs and produces a marked alteration of activity of liver enzymes.