Study of Microcalorimeters for Astrophysics Applications

In the framework of the Italian Space Agency R&D project, which is focused on the development of microcalorimeters for applications on astrophysics, we are studying different methods for TES microcalorimeter production and developing simulations of various absorber performances. In this paper are presented preliminary results obtained with two different geometries: front back and planar on SiN membrane.      

Geomechanical design of a room and rib pillar granite mine

The geomechanical and stability design of an underground granite mine located in Canal San Bovo （Trento district, Northeastern Italy） was described. The exploitation of the granite, which is used in the ceramic industry, was carried out by the rooms and rib pillars method. The rooms are 12 m wide while the pillars are 11 m wide and they cross the main discontinuity set of the rock mass in the perpendicular direction. To verify the stability condition of an underground mine, it is necessary to carry out the calcula- tions that are able to check both the local and global stability of the rock mass. In the studied example, this approach has been applied with the development of analytical and numerical parametric analyses and it has permitted to get the best orientation and to design the size of rooms and pillars.     

Industry-oriented software-based system for quality evaluation of vehicle audio environments

A new set of integrated software tools are proposed for the evaluation of vehicle audio quality for industrial purposes, taking advantage of the auralization approach that allows to simulate the binaural listening experience outside the cockpit. Two main cooperating tools are implemented. The first fulfills the function of acquiring relevant data for system modeling and for canceling the undesired effects of the acquisition chain. The second offers a user-friendly interface for real-time simulation of different car audio systems and the consequent evaluation of both objective and subjective performances. In the latter case, the listening procedure is directly experienced at the PC workplace, leading to a significant simplification of the audio-quality assessing task for comparing the selected systems. Moreover, such kind of subjective evaluation allowed to validate the proposed approach through a complete set of experiments (developed by means of a dedicated software environment) based on appropriate ITU recommendations.     

Characterisation of alkylphenols in pistachio (Pistacia vera L.) kernels

Pistachio kernels were extracted with n-hexane and the oil obtained was saponified with methanolic KOH. The extracted unsaponifiable matter was fractionated on Thin Layer Chromatography (TLC) plates. The band with R_f = 0.47, analysed by Gas Chromatography–Mass Spectrometry (GC–MS), showed the presence of long-chain alkylphenols: this is the first time that alkylphenols are reported in pistachio kernels. To elucidate the structures, Nuclear Magnetic Resonance (NMR) and GC–MS analyses (on the trimethylsilyl derivatives) were used. Sixteen different 3-alkylphenols (cardanols) with a saturated, monounsaturated and diunsaturated chain were detected. A reaction with dimethyl disulphide was successfully used to determine the double bond position in the monounsaturated compounds. Three phenols were new natural compounds. The most abundant cardanols were 3-(8-pentadecenyl)-phenol, 3-(10-pentadecenyl)-phenol, 3-pentadecyl-phenol and 3-(10-eptadecenyl)-phenol. Total amount of cardanols in the oils (mean of five samples) was roughly evaluated as 440 ± 95 mg kg⁻¹.     

Polymerisation occurrence in the anodic oxidation of phosphite on a boron-doped diamond electrode

The electrogeneration of polymeric phosphorus compounds during the anodic oxidation of aqueous solutions of phosphites on a boron-doped diamond electrode has been studied. Although the main oxidation product is orthophosphate, the results indicate the simultaneous generation of short-chain and cyclic compounds containing two and three phosphorus atoms whose evolution has been followed by ion chromatography.The effect on the reaction yield of several operative parameters such as current density, pH, temperature and initial phosphite concentration has been investigated.Consistently with the data presented, a new process for the generation of polymeric phosphates is obtained.     

Synthesis of diamond nanocrystals on polyimide film

Sulfur-assisted hot-filament chemical vapor deposition (HFCVD) was recently employed to grow diamond nano-crystals on polyimide film [F. Piazza, G. Morell, Diamond and Related Materials, 16 (2007) 1950], unambiguously showing that the substrate temperature was below 360 °C, the polyimide glass transition temperature. This accomplishment has opened the door to employ diamond in a wide range of applications where it needs to be integrated with temperature sensitive materials. The result reported earlier relies on visible Raman spectroscopy analysis. We hereby report new additional evidences confirming the result from transmission electron microscopy (TEM), high-resolution TEM, energy dispersive X-ray analysis, electron energy loss spectroscopy and selected area electron diffraction.     

Eigenmodes computation on quadrilateral meshes

We approximate a fluid-structure interaction eigenvalue problem by means of finite elements on quadrilateral meshes. The problem under consideration looks simple and has been the object of a wide investigation: actually, no standard numerical scheme achieves acceptable results in presence of field singularities. We consider a three-field mixed method introduced by Bathe et al. and based on rectangular meshes (see [3, 12]). Recent results show that particular care has to be taken into account when dealing with finite element approximation on general quadrilateral meshes. We present numerical experiments on several sequences of meshes which definitely show how the “local” approach has to be discarded, while the “global” approach gives reasonable results. Received: 30 January 2001 / Accepted: 30 May 2001     

Degradation of TiAlNiAu as ohmic contact metal for GaN HEMTs

Ti/Al/Ni/Au stack is widely used to form ohmic contact on GaN based semiconductor material. Long term thermal storage tests conducted to assess AlGaN/GaN HEMT technology have shown a dramatic degradation of this metal when stored more than 100 h at temperatures above 340 °C. The first evidence of degradation is the increase of resistance and the surface morphology evolution leading passivation film to crack. AES and EDS analyses have demonstrated that Ga out-diffusion and Au inter-diffusion are the root causes of this degradation. Cross sections outlined voids occurrence.