189,869 research outputs found

    Hydrodynamic squeeze-film bearings for gyroscopes

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    Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action

    An analysis of water in galactic infrared sources using the NASA Lear Airborne Observatory

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    The Michelson interferometer system on the NASA Lear Jet Airborne Observatory is described as well as the data reduction procedures. The objects observed (standard stars, M stars, a nebula, planets, and the moon) are discussed and the observing parameters are listed for each flight date. The spectra obtained from these data flights are presented, grouped by class of object

    Body-rock or lift-off in flow

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    Conditions are investigated under which a body lying at rest or rocking on a solid horizontal surface can be removed from the surface by hydrodynamic forces or instead continues rocking. The investigation is motivated by recent observations on Martian dust movement as well as other small- and large-scale applications. The nonlinear theory of fluid-body interaction here has unsteady motion of an inviscid fluid interacting with a moving thin body. Various shapes of body are addressed together with a range of initial conditions. The relevant parameter space is found to be subtle as evolution and shape play substantial roles coupled with scaled mass and gravity effects. Lift-off of the body from the surface generally cannot occur without fluid flow but it can occur either immediately or within a finite time once the fluid flow starts up: parameters for this are found and comparisons are made with Martian observations.Comment: 28 pages, 9 figure

    Affordable Housing as an Adequate Public Facility

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    Commodities and Transactions Exempt From Consumption Taxes

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    Value stream mapping is a tool that is frequently used by many different companies. It is a great tool used to achieve the work that follows the theories of lean production. The tool is used, however, only frequent on the factory floor and the method is also designed based on this type of use. An interest of applying the method on administrative parts of the company has occurred lately. Administrative parts of the company refers to the part that does all the planning such as purchasing, receiving orders, customer contact, contact with factory floor and other work that is made around the actual manufacturing. But the knowledge about applying value stream mapping on the planning part of the company is lacking because the method is relatively new. In this work, a comparison is made between the introduction of value stream analysis on production and planning. This has been done through a case study at ABB Robotics. On this case study a value stream analysis has been made on the planning part of ABB Robotics and the part of the factory floor manufacturing the control cabinets of the robots. The purpose of the performance was to create an understanding of the similarities and differences that exist in the application of value stream analysis on production and planning. The case study has been made based on the current literature available on the subject. The literature has then been reviewed critically, based on the differences and similarities shown by the performed case study. Based on an analysis of the results from the case study, several conclusions were drawn and reflected over taking into account the existing literature. Conclusions drawn from the study, questions the existing literature's critical attitude to the method. Critical review is important at this situation because it is a new method and much proof, that it is properly functioning, does not yet exist. The study mentions that value stream analysis of planning is not always relevant. The interest of the method depends on the type of business and its customers' needs. For a company where the lead time of the planning part of the company is not of great importance to the customer’s value stream mapping is not interesting to apply. The application of value stream analysis is much more complex and time-consuming according to the study and therefore it is not always worthwhile to use the method.VĂ€rdeflödesanalys Ă€r ett verktyg som anvĂ€nds i stor utstrĂ€ckning i dagslĂ€get. Det Ă€r ett bra verktyg som anvĂ€nds för att uppnĂ„ arbete som följer teorier kring lean produktion. Verktyget anvĂ€nds dĂ€remot endast frekvent pĂ„ producerande delar av en organisation och metoden Ă€r ocksĂ„ framtagen begrundat pĂ„ den typen av anvĂ€ndning. PĂ„ senare tid har ett intresse skapats för att applicera metoden Ă€ven pĂ„ administrativa delar av ett företag. Med administrativ del av företaget menas sjĂ€lva planerande delen av företaget som stĂ„r för rĂ„varuhemtagning, ordermottagning, kundkontakt, kontakt med produktion och andra steg som görs kring sjĂ€lva fabriksgolvet. AlltsĂ„ det arbete som sker pĂ„ företagets kontor. Eftersom att metoden att applicera vĂ€rdeflödesanalys pĂ„ planeringen Ă€r relativt ny Ă€r ocksĂ„ kunskaperna kring omrĂ„det bristande. I detta arbete görs en jĂ€mförelse mellan att införa vĂ€rdeflödesanalys pĂ„ produktionen respektive planeringen. Det har gjorts genom en fallstudie pĂ„ ABB Robotics. Under fallstudien har en vĂ€rdeflödesanalys utförts pĂ„ produktionen av styrskĂ„p till robotar samt kontoret pĂ„ ABB Robotics. Syftet med utförandet har varit att skapa en förstĂ„else för de skillnader som finns vid appliceringen av vĂ€rdeflödesanalys pĂ„ produktion och planering. Fallstudien har utförts med hjĂ€lp av den litteratur som finns kring Ă€mnet idag. DĂ€refter har litteraturen granskats kritiskt utifrĂ„n de skillnader som visades genom den utförda fallstudien. UtifrĂ„n analys av fallstudiens resultat har flera slutsatser dragits och reflekterats över med hĂ€nsyn tagen till befintlig litteratur. Slutsatser som dragits utifrĂ„n det ifrĂ„gasĂ€tter den befintliga litteraturens kritiska förhĂ„llning till metoden. Kritisk granskning av metoden Ă€r viktig eftersom att den Ă€r ny och bevis pĂ„ att den Ă€r vĂ€l fungerande Ă€nnu inte existerar i stor utstrĂ€ckning. Studien nĂ€mner att införandet av vĂ€rdeflödesanalys pĂ„ planering inte alltid Ă€r relevant. Intresset för metoden beror pĂ„ typ av företag och hur dess kunders behov ser ut. För ett företag dĂ€r ledtiden pĂ„ planeringen inte har nĂ„gon större betydelse för kunden Ă€r vĂ€rdeflödesanalys heller inte intressant att applicera. Appliceringen av vĂ€rdeflödesanalys Ă€r mycket mer komplex och tidskrĂ€vande enligt studien och dĂ€rför Ă€r det ocksĂ„ inte alltid lönt att anvĂ€nda metoden

    Goldilocks Supersymmetry: Simultaneous Solution to the Dark Matter and Flavor Problems of Supersymmetry

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    Neutralino dark matter is well motivated, but also suffers from two shortcomings: it requires gravity-mediated supersymmetry breaking, which generically violates flavor constraints, and its thermal relic density \Omega is typically too large. We propose a simple solution to both problems: neutralinos freezeout with \Omega ~10-100, but then decay to ~1 GeV gravitinos, which are simultaneously light enough to satisfy flavor constraints and heavy enough to be all of dark matter. This scenario is naturally realized in high-scale gauge-mediation models, ameliorates small scale structure problems, and implies that ``cosmologically excluded'' models may, in fact, be cosmologically preferred.Comment: 4 pages; v2: references added; v3: published versio

    Random and systematic measurement errors in acoustic impedance as determined by the transmission line method

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    The effect of random and systematic errors associated with the measurement of normal incidence acoustic impedance in a zero-mean-flow environment was investigated by the transmission line method. The influence of random measurement errors in the reflection coefficients and pressure minima positions was investigated by computing fractional standard deviations of the normalized impedance. Both the standard techniques of random process theory and a simplified technique were used. Over a wavelength range of 68 to 10 cm random measurement errors in the reflection coefficients and pressure minima positions could be described adequately by normal probability distributions with standard deviations of 0.001 and 0.0098 cm, respectively. An error propagation technique based on the observed concentration of the probability density functions was found to give essentially the same results but with a computation time of about 1 percent of that required for the standard technique. The results suggest that careful experimental design reduces the effect of random measurement errors to insignificant levels for moderate ranges of test specimen impedance component magnitudes. Most of the observed random scatter can be attributed to lack of control by the mounting arrangement over mechanical boundary conditions of the test sample
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