Design, manufacture and spin test of high contact ratio helicopter transmission utilizing Self-Aligning Bearingless Planetary (SABP)

A 450 hp high ratio Self-Aligning Bearingless Planetary (SABP) for a helicopter application was designed, manufactured, and spin tested under NASA contract NAS3-24539. The objective of the program was to conduct research and development work on a high contact ratio helical gear SABP to reduce weight and noise and to improve efficiency. The results accomplished include the design, manufacturing, and no-load spin testing of two prototype helicopter transmissions, rated at 450 hp with an input speed of 35,000 rpm and an output speed of 350 rpm. The weight power density ratio of these gear units is 0.33 lb hp. The measured airborne noise at 35,000 rpm input speed and light load is 94 dB at 5 ft. The high speed, high contact ratio SABP transmission appears to be significantly lighter and quieter than comtemporary helicopter transmissions. The concept of the SABP is applicable not only to high ratio helicopter type transmissions but also to other rotorcraft and aircraft propulsion systems

STRATEGIC AND VIRTUAL NETWORKS – A POSSIBLE INTEGRATION

One of the best known features of the Italian entrepreneurial system is undoubtedly the industrial district, a network of small and medium size enterprises; the object of this survey is to study the integration between the strategic network, identified by the relationship between the companies in a district, and the virtual Internet network.Industrial Districts; Net Economy; Shoes Maker Industry

Negative electronic compressibility and nanoscale inhomogeneity in ionic-liquid gated two-dimensional superconductors

When the electron density of highly crystalline thin films is tuned by chemical doping or ionic liq- uid gating, interesting effects appear including unconventional superconductivity, sizeable spin-orbit coupling, competition with charge-density waves, and a debated low-temperature metallic state that seems to avoid the superconducting or insulating fate of standard two-dimensional electron systems. Some experiments also find a marked tendency to a negative electronic compressibility. We suggest that this indicates an inclination for electronic phase separation resulting in a nanoscopic inhomo- geneity. Although the mild modulation of the inhomogeneous landscape is compatible with a high electron mobility in the metallic state, this intrinsically inhomogeneous character is highlighted by the peculiar behaviour of the metal-to-superconductor transition. Modelling the system with super- conducting puddles embedded in a metallic matrix, we fit the peculiar resistance vs. temperature curves of systems like TiSe2, MoS2, and ZrNCl. In this framework also the low-temperature debated metallic state finds a natural explanation in terms of the pristine metallic background embedding non-percolating superconducting clusters. An intrinsically inhomogeneous character naturally raises the question of the formation mechanism(s). We propose a mechanism based on the interplay be- tween electrons and the charges of the gating ionic liquid.Comment: substantially modified presentation: 12 pages 7 figure

Analisi numerico sperimentale dello squeal di un freno motociclistico.

Lo squeal è un tipico esempio di rumorosità causata da vibrazioni indotte da forze di attrito, che portano all’instabilità del sistema frenante. In questi ultimi sessant’anni sono stati condotti diversi studi, sperimentali, teorici e numerici per cercare di comprendere la natura dello squeal. Tutto questo interesse deriva dal fatto che la rumorosità dei freni è fonte di grande insoddisfazione per i clienti. Riuscire quindi ad unire ottime prestazioni frenanti all’eliminazione del rumore è considerato un importante obbiettivo da raggiungere per essere competitivi sul mercato. La sfida per gli ingegneri è quella di cercare metodi per eliminare la rumorosità in fase di progetto del freno. In questo lavoro vengono presentati i risultati di una campagna di test sperimentali svolti su un motoveicolo opportunamente strumentato per la registrazione dello squeal. Sono state condotte poi delle prove sperimentali in laboratorio, utilizzando un banco prova appositamente modificato. L’ultima parte della tesi presenta i risultati delle analisi modali effettuate sul sistema, focalizzando l’attenzione sull’analisi agli autovalori complessi, che può essere usata come strumento per simulazioni parametriche nella fase di progettazione del freno, al fine di evitare fenomeni di squeal

Seismic Response Analysis of Continuous Multispan Bridges with Partial Isolation

Partially isolated bridges are a particular class of bridges in which isolation bearings are placed only between the piers top and the deck whereas seismic stoppers restrain the transverse motion of the deck at the abutments. This paper proposes an analytical formulation for the seismic analysis of these bridges, modelled as beams with intermediate viscoelastic restraints whose properties describe the pier-isolator behaviour. Different techniques are developed for solving the seismic problem. The first technique employs the complex mode superposition method and provides an exact benchmark solution to the problem at hand. The two other simplified techniques are based on an approximation of the displacement field and are useful for preliminary assessment and design purposes. A realistic bridge is considered as case study and its seismic response under a set of ground motion records is analyzed. First, the complex mode superposition method is applied to study the characteristic features of the dynamic and seismic response of the system. A parametric analysis is carried out to evaluate the influence of support stiffness and damping on the seismic performance. Then, a comparison is made between the exact solution and the approximate solutions in order to evaluate the accuracy and suitability of the simplified analysis techniques for evaluating the seismic response of partially isolated bridges

Creation of a system for the coding of medical devices

Medical devices have different nomenclatures for their classification. Some of the most significant nomenclatures are the Universal Medical Device Nomenclature System (UMDNS) and the Global Medical Device Nomenclature (GMDN) by the Emergency Care Research Institute (ECRI). In Italy the main are CIVAB and “Classificazione Nazionale Dispositivi Medici” (National Classification for Medical Devices - CND). The aim of this study is to create a system to automatically decode several device models from CIVAB to UMDNS code. All medical devices are coded with a table which is based on their definitions presented in these nomenclatures. The coding is lastly applied to a list of models of medical devices, developed by different companies

Urban freight transport in Bologna: Planning commercial vehicle loading/unloading zones

AbstractMany European and overseas studies have brought into focus issues related to urban freight transport in order to find possible solutions (city logistics). Urban areas, instead of being living, commercial and resting places may have their functions jeopardized either due to the intense and short range road good's transport and by the lack of infrastructure. Commercial vehicles are detrimental for the urban environment, polluting with gasses and noise. The “just in time” policy of no warehousing enhances this kind of transportation. This paper describes some technical solutions for the management of stop and access areas for goods transport vehicles in order to allow the on-time delivery as well as to mitigate the traffic induced issues towards citizens.In particular, we focus attention on various issues concerning the areas where goods are loaded and unloaded, proposing a method that allows their size, their number and their location to be optimised