INNOVATION AND OPTIMIZATION OF THE INVESTMENT CASTING OF PRECIOUS ALLOYS

Various techniques and technologies have been developed and fine-tuned in recent years which have made it possible to improve the investment casting process and extend its field of applicability such as, for example, the application of rapid prototyping, rapid manufacturing, casting simulation and "non-traditional" materials. In the past decades, companies working in the precious metals sector could keep in their collection the same products for a long period, eventually applying minor modifications. Nowadays innovation is considered one of the key point for the success of the production, coupled to an increased attention towards quality and reliability of the product. The present paper deals with an analysis of some of the innovations introduced into the investment casting of precious metals in the recent years, in terms of process analysis, new materials involved for the fabrication and metal alloys

Control of Q-factor in nanobeam cavities on substrate

In this paper, we demonstrate how to efficiently control the quality factor of silicon nitride nanobeam cavities, grown on a silica substrate and embedded in an upper cladding, by engineering the nanobeam cross-section and the shape of the periodic holes. We propose optimized configurations that are able to overcome the decreasing of the Q-factor when the nanobeam is embedded in an asymmetric medium. More precisely, we show that the maximum achievable quality factor can be designed and tuned in asymmetric configurations where the upper cladding is particularly different from the substrate one. These optimized configurations exhibit high-Q factor and small mode volume over a wide range of the upper cladding refractive index paving the way for the realization of innovative optical sensors and for the compensation of fabrication tolerances in embedded optical nanobeam cavities.Postprin

Characterization of the catalytic flexible loop in the dihydroorotase domain of the human multi-enzymatic protein CAD

The dihydroorotase (DHOase) domain of the multifunctional protein carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, and dihydroorotase (CAD) catalyzes the third step in the de novo biosynthesis of pyrimidine nucleotides in animals. The crystal structure of the DHOase domain of human CAD (huDHOase) revealed that, despite evolutionary divergence, its active site components are highly conserved with those in bacterial DHOases, encoded as monofunctional enzymes. An important element for catalysis, conserved from Escherichia coli to humans, is a flexible loop that closes as a lid over the active site. Here, we combined mutagenic, structural, biochemical, and molecular dynamics analyses to characterize the function of the flexible loop in the activity of CAD's DHOase domain. A huDHOase chimera bearing the E. coli DHOase flexible loop was inactive, suggesting the presence of distinctive elements in the flexible loop of huDHOase that cannot be replaced by the bacterial sequence. We pinpointed Phe-1563, a residue absolutely conserved at the tip of the flexible loop in CAD's DHOase domain, as a critical element for the conformational equilibrium between the two catalytic states of the protein. Substitutions of Phe-1563 with Ala, Leu, or Thr prevented the closure of the flexible loop and inactivated the protein, whereas substitution with Tyr enhanced the interactions of the loop in the closed position and reduced fluctuations and the reaction rate. Our results confirm the importance of the flexible loop in CAD's DHOase domain and explain the key role of Phe-1563 in configuring the active site and in promoting substrate strain and catalysi

Plasmonic Bandgaps in 1D Arrays of Slits on Metal Layers Excited by Out-of-Plane Sources

We analyze the effective opening of finite bands of inhibited transmission in realistic systems excited by actual out-of-plane sources. We first observe how the excitation of surface plasmon polaritons in one-dimensional arrays of metal slits depends on the angle of incidence of the source field. Then, the well-known grating-coupling equation is revised in order to find an asymmetric structure with equivalent parameters which, under perfectly normal excitation, is able to exhibit surface plasmon polariton modes at the same wavelengths of the original structure which undergoes a nonorthogonal incidence of the light. In this way we demonstrate through finite-element simulations that a realistic system, probed by a source beam in a finite light-cone, can be effectively decomposed in several equivalent systems with different physical and geometrical parameters, with results in the enlargement of the theoretically expected punctual minimum of transmission

MIG and TIG Joining of AA1070 Aluminium Sheets with Different Surface Preparations

In this work, AA1070 aluminium alloy sheets are joined using TIG and MIG welding after three different edge preparations. Shearing, water jet and plasma-cut processes were used to cut sheets, subsequently welded using ER5356 and ER4043 filler metals for TIG and MIG, respectively. Mechanical properties of the obtained sheets were assessed through tensile tests obtaining a relation between sheet preparation and welding tightness. Micro-hardness measures were performed to evaluate the effects of both welding and cutting processes on the micro-hardness of the alloy, highlighting that TIG welding gives rise to inhomogeneous micro-hardness behaviour. After tensile tests, surface fractures were observed employing scanning electron microscopy to highlight the relation between tensile properties and edge preparations. Fractures show severe oxidation in the water jet cut specimens, ductile fractures and gas porosities

Aluminium alloy addition effects on the behaviour of soft magnetic materials at low frequencies

The present paper focused on the effects of aluminium alloy addition on the behaviour of soft magnetic materials at low frequencies. The microstructure investigation reveals that for materials with high aluminium contents, the pores are oriented near or surrounding the aluminium particles. The microstructure investigation reveals that for materials with high aluminium contents, the pores are oriented near or surrounding the aluminium particles, as well as after heat treatment shows coarse-grained structure with a minimum number of inclusions within the grains and at the grain boundaries. Results show that the magnetic properties are dependent on the structural state of the investigated material. Magnetic properties increased with decreasing density due to the enhanced densification by means of applied pressing pressure and promote porosity reduction during heat treatment

An assessment of financial sector rescue programmes

We analyse the wide array of rescue programmes adopted in several countries, following Lehman Brothers’ default in September 2008, in order to support banks and other financial institutions. We first provide an overview of the programmes, comparing their characteristics, magnitudes and participation rates across countries. We then consider the effects of the programmes on banks’ risk and valuation, looking at the behaviour of CDS premia and stock prices. We then proceed to analyse the issuance of government guaranteed bonds by banks, examining their impact on banks’ funding and highlighting undesired effects and distortions. Finally, we briefly review the recent evolution of bank lending to the private sector. We draw policy implications, in particular as regards the way of mitigating the distortions implied by such programmes and the need for an exit strategy.bank asset guarantees, capital injection, banks, financial sector, financial crisis, bank consolidation, bank mergers and acquisitions, event studies, government guaranteed bonds, credit crunch, exit strategy

Removal of chlorinated pesticide contamination by soil washing with sole water

Chlorinated pesticide soil contamination still affects large territories due to past extensive use, poor solubility in water and scarce biodegradability of these agro-chemicals. In particular, this is noticeable for dichloro-diphenyl-trichloroethanes and their derivatives, globally referred as DDX contaminants. Presently, containment or immobilisation is a dominant approach to limit contamination, and remediation has been tried mainly at laboratory scale with contradictory results. Soil washing has been reported as a possible remediation treatment, although environmental effects of employed synthetic co-solvents or surfactants remain unclear. A soil washing treatment with sole water has been set up at laboratory scale, obtaining promising results on a contaminated soil with DDX level of 5050 mg/kg

Rapid Characterization Method for SMC Materials for a Preliminary Selection

In electrical machines, laminated steels are commonly adopted as soft magnetic materials, while for permanent magnets, sintered ferrites and NdFeB are the most common solutions. On the other hand, the growing demand for volume reduction with the increment of efficiency leads to the necessity of exploring other magnetic materials able to face the challenge better than the traditional ones. Bonded magnets have been used to replace sintered magnets, obtaining a better use of space and particular magnetic properties. Instead, for the magnetic circuit, Soft Magnetic Composites (SMC) allow realizing very complex magnetic design (3D path for flux) with iron loss reduction at medium-high frequencies, especially for the eddy currents loss contribution. On the other hand, SMC materials have such drawbacks as low mechanical properties and high hysteresis losses. For this reason, in this work, different studies considering several variables have been carried out. SMCs were produced through a moulding process; inorganic and organic layers to cover ferromagnetic particles were used, adopting different coating processes. Particu-lar tests have been performed for a quicker and more indicative overview of the materials ob-tained. The single sheet tester (SST) is easier than traditional toroidal methods; on the other hand, the multiplicity of variables affects the SMC materials and their process. For this reason, coercivity and conductibility tests permit rapid measurement and provide a direct classification of the produced SMCs, providing the main information needed to select suitable materials. Re-sults highlighted that choosing the more appropriate SMC material is possible after using these simple preliminary tests. After these tests, it was possible to argue that with 0.2 wt% of phenolic resin as the organic layer (and compaction pressure of 800 MPa), it is possible to produce a good SMC. On the other hand, the SMC with 0.2 wt% of epoxy resin (and compaction pressure of 800 MPa) gives a minor coercivity value. Additionally, despite the SMC with the inorganic layer, 0.2 wt% of nano-ferrites showing the best coercivity values (specifically for vacuum treatment at 600 °C), their resistivity was unsatisfactory

Auditoria de imagen para la empresa de Purificadores de agua: Pure Water Systems de El Salvador

La presente monografía realiza el análisis y proceso a detalle de una Auditoría de Imagen interna y externa dirigida hacia la empresa de purificadores de Agua: PURE WATER SYSTEMS de El Salvador. Dentro de la Auditoría se analiza y conoce si la marca de esta empresa ha logrado ser posicionada con sus públicos objetivos. El proceso para llevar a cabo este estudio se basa en el uso de las variables imagen y percepción. Se toma en cuenta que “PURE WATER SYSTEMS” de El Salvador jamás ha realizado un proceso de Auditoria interna o externa, por lo tanto éste es el primer estudio a profundidad que se le realiza. Dentro del análisis se indaga en como sus diferentes públicos ven a la empresa, pero al mismo tiempo se ahonda en que aspectos se pueden mejorar para tener un mayor número de clientes activos e identificados con la marca. En el primer capítulo se describe el problema que se encontró en las primeras entrevistas a profundidad con los públicos a trabajar. De igual forma se establece el objetivo general y objetivos específicos del presente escrito, así como las preguntas para realizar la investigación, sus variables y una justificación del abordaje de la misma. El segundo capítulo se conforma por el marco histórico de la mano del marco teórico que ahonda en los temas de interés para llevar a cabo este estudio. Elementos esenciales como la estructura organizativa de la empresa, equipos con los que cuenta y los servicios que brinda a sus diferentes públicos. En el tercer capítulo se muestra el marco organizacional y comunicacional, el tipo de investigación realizado y el muestreo en el que se basó para realizar el proceso de Auditoría de Imagen interna y externa. Para finalizar en el cuarto capítulo se desarrolla la estrategia comunicacional que se propone a la empresa de purificadores de Agua, dicha propuesta destaca algunos de los elementos diferenciadores con los que “PURE WATER SYSTEMS” actualmente cuenta y proporciona ideas de innovación que a futuro se pueden implementarMonografía presentada para optar al título de Licenciado en Ciencias de la Comunicació