La eficiencia como reto de las empresas de inserción

In recent years the Spanish Work Integration Social Enterprises have achieved both legal recognition as a dramatic growth, and also a major stakeholder’s implication and the resources employed in these businesses within the economy, in particular the Social Economy. In this area and even though descriptive and normative level; the studies about social integration companies have increased; however, there is little research focused on the management of such entities. In this paper we have analyzed the factors involved in the efficient management of integration enterprises from a dual perspective, managers and promoters entities, and Administration. In the first case we have identified some factors that probably improve the efficiency in business management, in the second case, we have defined some characteristics that favor cost-benefit ratio of such entities for the administration, and consequently for the Society. The methods used in this research are analytic-synthetic, hypothetic-deductive, and cost-benefit analysis, complementary to each other.En los últimos años las Empresas de Inserción en España han conseguido tanto su reconocimiento legal como un crecimiento espectacular, y son mayores los stakeholders implicados y los recursos empleados en este tipo de empresas dentro de la Economía; en concreto, la Economía Social. En esta área y aunque a nivel descriptivo e incluso normativo han proliferado los estudios sobre las empresas de inserción; no obstante, son aún muy escasas las investigaciones sobre la gestión empresarial de este tipo de entidades. En el presente trabajo hemos analizado los diversos factores implicados en la gestión eficiente de las Empresas de Inserción, desde una doble perspectiva, la de los gestores y entidades promotoras, y la de la Administración. En el primer caso hemos identificado algunos factores que probablemente mejoran la eficiencia en la gestión de las empresas; en el segundo caso, hemos delimitado algunas características que favorecen la relación coste-beneficio de este tipo de entidades para la Administración, y consecuentemente para la Sociedad. Los métodos utilizados en esta investigación son analítico-sintético, el hipotético-deductivo, y el análisis coste-beneficio; complementarios entre sí

Short Course T2: Gas Bearings and Magnetic Bearings for Oil-Free Rotating Machinery

Short CourseGas bearings (GBs) are an efficient alternative for load support of high speed microturbomachinery (< 400 kW, +1000°F, +3M DN). These bearings are compliant surface hydrodynamic bearings using ambient air as the working fluid media. Oil-free systems have lesser part count, footprint and weight and are environmentally friendly and (nearly) maintenance free, thus saving costs and resources. Current commercial applications include air cycle machines, cryogenic turbo expanders and micro gas turbines. Other upcoming applications include auxiliary power units, automotive turbochargers and aircraft gas turbine engines for regional jets. The short course provides practicing engineers with a comprehensive review of existing gas bearing technologies including their principle of operation, analysis and experimental verification, comparison amongst other gas bearing types, as well as the integration of gas bearings, foil bearings in particular, into actual rotor-bearing systems (hot and cold). The course also includes an introduction to magnetic bearings and their applications in oil-free microturbomachinery

Leonardo's Civil Bridges

Within both aesthetic and history fields, civil engineering occupies a privileged place among arts whose manifestations are based on drawing. In this work, Leonardo’s creativity concerned with civil bridges proyects, have been studied. Leonardo designed ten bridges: eight of them intended for military porposes and only two were purely planned for civil functionaly - “Ponte sul corno d’oro”, infolio 66, manuscript L; and “Ponte a due piani”, represented in the Manuscript B at the Institute of France, infolio 23. There can be no doubt about Leonardo’s intentions when he started on designing these two bridges: his genious for creativy focused on providing both singulary and functionaly to the structures: they should be admired and utilized at the same time, a monument for civil society to be used.The work presented here attemps to make an scientist-historical trip along these Leonardo’s bridges, highlighting their technical, geometrical and aesthetic characteristics, as well as emphasizing Leonardo’s human, scientist and artistic nature

High-k gadolinium scandate on Si obtained by high pressure sputtering from metal targets and in-situ plasma oxidation

This article studies the physical and electrical behavior of Gd2-xScxO3 layers grown by high pressure sputtering from metallic Gd and Sc targets. The aim is to obtain a high permittivity dielectric for microelectronic applications. The films were obtained by the deposition of a metallic nanolaminate of Gd and Sc alternating layers, which is afterwards in-situ oxidized by plasma. The oxide films obtained were close to stoichiometry, amorphous and with minimal interfacial regrowth. By fabricating metal-insulator-semiconductor capacitors we found that a moderate temperature annealing is needed to enhance permittivity, which reaches a high value of 32 while keeping moderate leakage. Finally, the feasibility of interface scavenging in this material with Ti gate electrodes is also demonstrated.Comment: 36 pages, 13 figure

IJTC2007-44047 Effect of Side Feed Pressurization on the Dynamic Performance of Gas Foil Bearings

ABSTRACT Oil-free micro turbomachinery implementing gas foil bearings (GFBs) has improved mechanical efficiency and reliability. Adequate thermal management for operation in high temperature environments is an issue of importance in applications such as in gas turbines and turbochargers. GFBs often need a cooling gas flow, axially fed through one end of the bearing, to transport the heat conducted from a hot turbine, for example. Side gas pressurization, however, has a paramount effect on reducing amplitudes of motion, synchronous and subsynchronous. Presently, shaft motion measurements in a test rotor supported on GFBs show this remarkable effect. A computational gas film model implementing the evolution of gas circumferential flow velocity as a function of the imposed side pressure is advanced. Predicted direct stiffnesses and damping coefficients for the test GFB increase as the magnitude of feed pressure raises, while the difference in cross-coupled stiffnesses, directly related to rotor-bearing system stability, decreases. Predictions of threshold speed of instability and whirl frequency ratio are in close agreement with the measurements. INTRODUCTION Implementing gas foil bearings (GFBs) in micro turbomachinery reduces system complexity and maintenance costs, and increases efficiency and operating life. GFBs with engineered solid lubricants (coatings) are being developed for application in high temperature environments [4] conduct a series of shaft speed coast down tests on a rotor supported on GFBs and find that sufficiently large imbalances induce subsynchronous whirl rotor motions of large amplitude also associated to low natural frequency rigid body modes. Measurements also reveal the paramount effect of side pressurization, primarily intended for cooling a GFB, on ameliorating amplitudes of synchronous response and even eliminating subsynchronous motions. This paper presents more test data related to the rotordynamic performance of GFBs operating with external side gas pressurization and details progress in the evolution of a predictive computational model

La eficiencia como reto de las empresas de inserción

En los últimos años las Empresas de Inserción en España han conseguido tanto su reconocimiento legal como un crecimiento espectacular, y son mayores los stakeholders implicados y los recursos empleados en este tipo de empresas dentro de la Economía; en concreto, la Economía Social. En esta área y aunque a nivel descriptivo e incluso normativo han proliferado los estudios sobre las empresas de inserción; no obstante, son aún muy escasas las investigaciones sobre la gestión empresarial de este tipo de entidades. En el presente trabajo hemos analizado los diversos factores implicados en la gestión eficiente de las Empresas de Inserción, desde una doble perspectiva, la de los gestores y entidades promotoras, y la de la Administración. En el primer caso hemos identificado algunos factores que probablemente mejoran la eficiencia en la gestión de las empresas; en el segundo caso, hemos delimitado algunas características que favorecen la relación coste-beneficio de este tipo de entidades para la Administración, y consecuentemente para la Sociedad. Los métodos utilizados en esta investigación son analítico-sintético, el hipotético-deductivo, y el análisis coste-beneficio; complementarios entre sí

GT2004-53621 ROTORDYNAMIC PERFORMANCE OF FLEXURE PIVOT HYDROSTATIC GAS BEARINGS FOR OIL-FREE TURBOMACHINERY

ABSTRACT Micro-turbomachinery demands gas bearings to ensure compactness, lightweight and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. Presently, tests conducted on a small rotor supported on flexure pivot -hydrostatic pad gas bearings (FPTPBs) demonstrate stable rotordynamic responses up to 100,000 rpm (limit of the drive motor). Test rotor responses show the feed pressure raises the system critical speed (increase in bearing direct stiffness) while the viscous damping ratio decreases. Predictions correlate favorably with experimentally identified (synchronous) direct stiffness bearing force coefficients. Identified experimental gas bearing synchronous damping coefficients are 50% or less of the predicted magnitudes, though remaining relatively constant as the rotor speed increases. Tests without feed pressure show the rotor becomes unstable at ~ 81 krpm with a whirl frequency ratio of 20%. FPTPBs are mechanically complex and more expensive than cylindrical plain bearings. However, their enhanced stability characteristics and predictable rotordynamic performance makes them desirable for the envisioned oil-free applications in high speed micro turbomachinery. KEYWORDS Gas bearings, rotordynamics, oil-free turbomachinery. NOMENCLATUR

Squeeze Film Dampers: An Experimental Appraisal of Their Dynamic Performance

LectureLecture 15: Squeeze Film Dampers (SFDs) are effective means to ameliorate rotor vibration amplitudes and to suppress instabilities in rotor-bearing systems. A SFD is not an off-the-shelf mechanical element but tailored to a particular rotor-bearing system as its design must satisfy a desired damping ratio; if too low, the damper is ineffective, whereas if damping is too large, it locks the system aggravating the system response. In many cases, SFDs are also employed to control the placement of (rigid body) critical speeds displacing the machine operation into a speed range with effective structural isolation. Industry demands well-engineered SFDs with a low footprint to reduce cost, maintenance, weight, and space while pushing for higher operating shaft speeds to increase power output. Compact aero jet engines implement ultra-short length SFDs (L/D ? 0.2) to satisfy stringent weight and space demands with low parts count. A manufacturer, as part of a business plan to develop and commercialize energy efficient aircraft gas turbine engines, supported a multiple–year project to test novel SFD design spaces. In spite of the myriad of analyses and experimental result reported in the literature, there has not been to date a concerted effort to investigate the dynamic forced performance of a SFD through its many configurations: open ends vis-à-vis sealed ends conditions, and supply conditions with a fluid plenum or deep groove vis-à-vis feed holes directly impinging into the film land. This lecture presents experimental results obtained with a dedicated rig to evaluate short length SFDs operating under large dynamic loads (2.2 kN ? 500 lbf) that produced circular and elliptical whirl orbits of varying amplitude, centered and off-centered. The lecture first reviews how SFDs work, placing emphasis on certain effects largely overlooked by practitioners who often regard the SFD as a simple non-rotating journal bearing. These effects are namely fluid inertia amplification in the supply or discharge grooves, pervasive air ingestion at high whirl frequencies, and effective end sealing means to enhance damping. The bulk of the lecture presents for various SFD configurations comparisons of experimentally identified damping (C) and inertia or added mass (M) coefficients versus amplitude of motion (orbit size) and static eccentricity position, both ranging from small to large; as large as the film clearance! The experiments, conducted over six plus years of continued work give an answer to the following fundamental practitioners’ questions: (a) Dampers don’t have a stiffness (static centering capability), how come? (b) Why is there fluid inertia or added mass in a damper? Isn’t a damper a purely viscous element? (c) How much do the damping and added mass change when the film length is halved? What about increasing the clearance to twice its original magnitude? (d) How much more damping is available if the damper has end seals? (e) Is a damper with feed holes as effective as one containing a groove that ensures lubricant pools to fill the film? What if a hole plugs, is a damper still effective? (f) Do the amplitude and shape of whirl motion affect the damper force coefficients? (g) What happens if the damper operates largely off-centered; does its performance become nonlinear? (h) What do prevailing theoretical predictions correlate with the experimental record