1,833 research outputs found

    Explaining post-apartheid South African human rights foreign policy: unsettled identity and conflicting interests

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    The end of apartheid in 1994 brought with it many expectations – both domestically and internationally – about the kind of state the new South Africa would be and the foreign policies it would pursue, with many expecting South Africa to pursue a human rights-based foreign policy. However, South Africa has pursued a much more paradoxical foreign policy, with significant gaps between its stated commitment to human rights principles and its action in support of those principles. This article seeks to explain these gaps. Delving into the literature on norms-based and interest-based explanations of state behavior, it argues that both approaches help to explain South Africa’s foreign policy actions. However, it is the unsettled nature of its identities and interests after 1994, as its leaders (in particular Thabo Mbeki) sought to reconcile a commitment to democracy and human rights with equally strong (if not greater) commitments to Afrocentrism and anti-imperialism, which provides the most interesting avenues for exploration

    Approach Considerations in Aircraft with High-Lift Propeller Systems

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    NASA's research into distributed electric propulsion (DEP) includes the design and development of the X-57 Maxwell aircraft. This aircraft has two distinct types of DEP: wingtip propellers and high-lift propellers. This paper focuses on the unique opportunities and challenges that the high-lift propellers--i.e., the small diameter propellers distributed upstream of the wing leading edge to augment lift at low speeds--bring to the aircraft performance in approach conditions. Recent changes to the regulations related to certifying small aircraft (14 CFR x23) and these new regulations' implications on the certification of aircraft with high-lift propellers are discussed. Recommendations about control systems for high-lift propeller systems are made, and performance estimates for the X-57 aircraft with high-lift propellers operating are presented

    Decomposition-Based Decision Making for Aerospace Vehicle Design

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    Most practical engineering systems design problems have multiple and conflicting objectives. Furthermore, the satisfactory attainment level for each objective ( requirement ) is likely uncertain early in the design process. Systems with long design cycle times will exhibit more of this uncertainty throughout the design process. This is further complicated if the system is expected to perform for a relatively long period of time, as now it will need to grow as new requirements are identified and new technologies are introduced. These points identify a need for a systems design technique that enables decision making amongst multiple objectives in the presence of uncertainty. Traditional design techniques deal with a single objective or a small number of objectives that are often aggregates of the overarching goals sought through the generation of a new system. Other requirements, although uncertain, are viewed as static constraints to this single or multiple objective optimization problem. With either of these formulations, enabling tradeoffs between the requirements, objectives, or combinations thereof is a slow, serial process that becomes increasingly complex as more criteria are added. This research proposal outlines a technique that attempts to address these and other idiosyncrasies associated with modern aerospace systems design. The proposed formulation first recasts systems design into a multiple criteria decision making problem. The now multiple objectives are decomposed to discover the critical characteristics of the objective space. Tradeoffs between the objectives are considered amongst these critical characteristics by comparison to a probabilistic ideal tradeoff solution. The proposed formulation represents a radical departure from traditional methods. A pitfall of this technique is in the validation of the solution: in a multi-objective sense, how can a decision maker justify a choice between non-dominated alternatives? A series of examples help the reader to observe how this technique can be applied to aerospace systems design and compare the results of this so-called Decomposition-Based Decision Making to more traditional design approaches

    Budget impact of adding ivabradine to standard of care in patients with chronic systolic heart failure in the United States

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    BACKGROUND: Heart failure (HF) costs 21billionannuallyindirecthealthcarecosts,80OBJECTIVE:ToestimatethebudgetimpactofivabradinefromaU.S.commercialpayerperspective.METHODS:Abudgetimpactmodelestimatedthepermemberpermonth(PMPM)impactofintroducingivabradinetoexistingformulariesbycomparingareferencescenario(SoC)andanewdrugscenario(ivabradine+SoC)inhypothetical1millionmembercommercialandMedicareAdvantageplans.Inbothscenarios,U.S.claimsdatawereusedforthereferencecumulativeannualratesofhospitalizations(HF,nonHFcardiovascular[CV],andnonCV),andhospitalizationrateswereadjustedusingSHIFTdata.ThemodelcontrolledformortalityriskusingSHIFTandU.S.lifetabledata,andhospitalizationcostswereobtainedfromU.S.claimsdata:HFrelated=21 billion annually in direct health care costs, 80% of which is directly attributable to hospitalizations. The SHIFT clinical study demonstrated that ivabradine plus standard of care (SoC) reduced HF-related and all-cause hospitalizations compared with SoC alone. OBJECTIVE: To estimate the budget impact of ivabradine from a U.S. commercial payer perspective. METHODS: A budget impact model estimated the per-member-per month (PMPM) impact of introducing ivabradine to existing formularies by comparing a reference scenario (SoC) and a new drug scenario (ivabradine + SoC) in hypothetical 1 million-member commercial and Medicare Advantage plans. In both scenarios, U.S. claims data were used for the reference cumulative annual rates of hospitalizations (HF, non-HF cardiovascular [CV], and non-CV), and hospitalization rates were adjusted using SHIFT data. The model controlled for mortality risk using SHIFT and U.S. life table data, and hospitalization costs were obtained from U.S. claims data: HF-related = 37,507; non-HF CV = 28,951;andnonCV=28,951; and non-CV = 17,904. The annualized wholesale acquisition cost of ivabradine was 4,500,withbaselineuseforthisnewdrugat2RESULTS:BasedontheapprovedU.S.indication,approximately2,000commerciallyinsuredpatientsfroma1millionmembercommercialplanwereeligibletoreceiveivabradine.IvabradineresultedinaPMPMcostsavingsof4,500, with baseline use for this new drug at 2%, increasing 2% per year. RESULTS: Based on the approved U.S. indication, approximately 2,000 commercially insured patients from a 1 million-member commercial plan were eligible to receive ivabradine. Ivabradine resulted in a PMPM cost savings of 0.01 and 0.04inyears1and3ofthecoremodel,respectively.Afterincludingtheacquisitionpriceforivabradine,themodelshowedadecreaseintotalcostsinthecommercial(0.04 in years 1 and 3 of the core model, respectively. After including the acquisition price for ivabradine, the model showed a decrease in total costs in the commercial (991,256 and 474,499,respectively)andMedicarepopulations(474,499, respectively) and Medicare populations (13,849,262 and 4,280,291,respectively)inyear1.Thisdecreasewasdrivenbyivabradinesreductioninhospitalizationrates.Forthecoremodel,theestimatedpharmacyonlyPMPMinyear1was4,280,291, respectively) in year 1. This decrease was driven by ivabradine’s reduction in hospitalization rates. For the core model, the estimated pharmacy-only PMPM in year 1 was 0.01 for the commercial population and $0.24 for the Medicare Advantage population. CONCLUSIONS: Adding ivabradine to SoC led to lower average annual treatment costs. The negative PMPM budget impact indicates that ivabradine is an affordable option for U.S. payers

    A Method for Designing Conforming Folding Propellers

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    As the aviation vehicle design environment expands due to the in flux of new technologies, new methods of conceptual design and modeling are required in order to meet the customer's needs. In the case of distributed electric propulsion (DEP), the use of high-lift propellers upstream of the wing leading edge augments lift at low speeds enabling smaller wings with sufficient takeoff and landing performance. During cruise, however, these devices would normally contribute significant drag if left in a fixed or windmilling arrangement. Therefore, a design that stows the propeller blades is desirable. In this paper, we present a method for designing folding-blade configurations that conform to the nacelle surface when stowed. These folded designs maintain performance nearly identical to their straight, non-folding blade counterparts

    Antimatter and Matter Production in Heavy Ion Collisions at CERN (The NEWMASS Experiment NA52)

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    Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. Together with previous data taking at a rigidity of -20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3 without centrality requirements. We measured nuclei and antinuclei (p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei are mainly produced via the coalescence mechanism. However the centrality dependence of the antibaryon to baryon ratios show that antibaryons are diminished due to annihilation and breakup reactions in the hadron dense environment. The volume of the particle source extracted from coalescence models agrees with results from pion interferometry for an expanding source. The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide with each other and with the thermal freeze-out of hadrons.Comment: 12 pages, 8 figures, to appear in the proceedings of the conference on 'Fundamental Issues in Elementary Matter' Bad Honnef, Germany, Sept. 25-29, 200

    Drag Reduction Through Distributed Electric Propulsion

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    One promising application of recent advances in electric aircraft propulsion technologies is a blown wing realized through the placement of a number of electric motors driving individual tractor propellers spaced along each wing. This configuration increases the maximum lift coefficient by providing substantially increased dynamic pressure across the wing at low speeds. This allows for a wing sized near the ideal area for maximum range at cruise conditions, imparting the cruise drag and ride quality benefits of this smaller wing size without decreasing takeoff and landing performance. A reference four-seat general aviation aircraft was chosen as an exemplary application case. Idealized momentum theory relations were derived to investigate tradeoffs in various design variables. Navier-Stokes aeropropulsive simulations were performed with various wing and propeller configurations at takeoff and landing conditions to provide insight into the effect of different wing and propeller designs on the realizable effective maximum lift coefficient. Similar analyses were performed at the cruise condition to ensure that drag targets are attainable. Results indicate that this configuration shows great promise to drastically improve the efficiency of small aircraft

    Design of an Electric Propulsion System for SCEPTOR

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    The rise of electric propulsion systems has pushed aircraft designers towards new and potentially transformative concepts. As part of this effort, NASA is leading the SCEPTOR program which aims at designing a fully electric distributed propulsion general aviation aircraft. This article highlights critical aspects of the design of SCEPTOR's propulsion system conceived at Joby Aviation in partnership with NASA, including motor electromagnetic design and optimization as well as cooling system integration. The motor is designed with a finite element based multi-objective optimization approach. This provides insight into important design tradeoffs such as mass versus efficiency, and enables a detailed quantitative comparison between different motor topologies. Secondly, a complete design and Computational Fluid Dynamics analysis of the air breathing cooling system is presented. The cooling system is fully integrated into the nacelle, contains little to no moving parts and only incurs a small drag penalty. Several concepts are considered and compared over a range of operating conditions. The study presents trade-offs between various parameters such as cooling efficiency, drag, mechanical simplicity and robustness
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