2,872 research outputs found
Rotorcraft convertible engine study
The objective of the Rotorcraft Convertible Engine Study was to define future research and technology effort required for commercial development by 1988 of convertible fan/shaft gas turbine engines for unconventional rotorcraft transports. Two rotorcraft and their respective missions were defined: a Fold Tilt Rotor aircraft and an Advancing Blade Concept (ABC) rotorcraft. Sensitivity studies were conducted with these rotorcraft to determine parametrically the influence of propulsion characteristics on aircraft size, mission fuel requirements, and direct operating costs (DOC). The two rotorcraft were flown with conventional propulsion systems (separate lift/cruise engines) and with convertible propulsion systems to determine the benefits to be derived from convertible engines. Trade-off studies were conducted to determine the optimum engine cycle and staging arrangement for a convertible engine. Advanced technology options applicable to convertible engines were studied. Research and technology programs were identified which would ensure technology readiness for commercial development of convertible engines by 1988
Propulsion Study for Small Transport Aircraft Technology (STAT)
Propulsion requirements were determined for 0.5 and 0.7 Mach aircraft. Sensitivity studies were conducted on both these aircraft to determine parametrically the influence of propulsion characteristics on aircraft size and direct operating cost (DOC). Candidate technology elements and design features were identified and parametric studies conducted to select the STAT advanced engine cycle. Trade off studies were conducted to determine those advanced technologies and design features that would offer a reduction in DOC for operation of the STAT engines. These features were incorporated in the two STAT engines. A benefit assessment was conducted comparing the STAT engines to current technology engines of the same power and to 1985 derivatives of the current technology engines. Research and development programs were recommended as part of an overall technology development plan to ensure that full commercial development of the STAT engines could be initiated in 1988
Z-Spec: A MM-Wave Spectrometer For Measuring Redshifts Of Submillimeter Galaxies
We are building a background-limited, broadband millimeter-wave spectrometer (Z-Spec) for observations of CO rotational transitions from high-redshift dusty galaxies. The large instantaneous bandwidth (195 to 310 GHz) will enable redshifts of dust obscured galaxies to be unambiguously measured. Z-Spec uses a waveguide-coupled grating architecture in which the light propagation is confined within a parallel-plate waveguide. The grating is extremely compact compared to a classical free-space system. An array of silicon nitride bolometers cooled to 100 mK will provide background-limited performance. Z-Spec serves as a technology demonstration for a future space-borne far-infrared grating spectrometer
Homotopy types of stabilizers and orbits of Morse functions on surfaces
Let be a smooth compact surface, orientable or not, with boundary or
without it, either the real line or the circle , and
the group of diffeomorphisms of acting on by the rule
, where and .
Let be a Morse function and be the orbit of under this
action. We prove that for , and
except for few cases. In particular, is aspherical, provided so is .
Moreover, is an extension of a finitely generated free abelian
group with a (finite) subgroup of the group of automorphisms of the Reeb graph
of .
We also give a complete proof of the fact that the orbit is tame
Frechet submanifold of of finite codimension, and that the
projection is a principal locally trivial -fibration.Comment: 49 pages, 8 figures. This version includes the proof of the fact that
the orbits of a finite codimension of tame action of tame Lie group on tame
Frechet manifold is a tame Frechet manifold itsel
Extended family caring for children orphaned by AIDS: balancing essential work and caregiving in a high HIV prevalence nations.
While over 90 per cent of the 15 million children who have been orphaned by HIV/AIDS are cared for by family members, there is little information about whether adults can meet orphans' essential caregiving needs while working to economically survive. Using a survey we conducted in Botswana of 1033 working adults, we analyse the experience of adults who are caring for orphans. Over one-third of working adults were caring for orphans and many with few financial resources: 82% were living on household incomes below US$10 purchasing power parity adjusted per person per day. Because of their caregiving responsibilities, they were less able to supplement income with overtime, weekend, evening, or night work. At the same time caregiving responsibilities meant orphan caregivers spent fewer hours caring for their own children and other family members. Nearly half of orphan caregivers had difficulties meeting their children's needs, and nearly 75% weren't able to meet with children's teachers. Pay loss at work compounded the problems: One-quarter of orphan caregivers reported having to take unpaid leave to meet sick childcare needs and nearly half reported being absent from work for children's routine health care. This paper makes clear that if families are to provide adequate care for orphans while economically surviving there needs to be increases in social supports and improvements in working conditions
An effective approach to improve the performance of PC-based superplasticizer in alkali-activated slag
The lack of workability has hindered the industriallisation of alkali-activated slag
(AAS) - a novel, low carbon cementitious building material. In order to address this main barrier,
adding superplasticiser (SP) is essential. The main reason causing the dysfunction of current
commercial SP in AAS has been identified as competitive adsorption between the SPs and the
activators. The separate SP addition methods (adding SP and activator separately) offers the
potentials to tackle the above issue. In this paper, the effects of separate addition methods of
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lignosulfonate superplasticiser (LS) in AAS activated by NaOH were investigated. The adsorption
between the LS and the slag was examined to understand the interaction between the SP and the
slag. The workability and rheological properties of fresh NaOH-activated slag and the compressive
strength of hardened NaOH-activated slag were also investigated. The results indicated that the
separate addition methods reduced the competitive adsorption between the SPs and the NaOH
activator, leading to a higher adsorption of the SPs on the slag. Consequently, the workability and
rheological properties of NaOH-activated slag was enhanced by separate addition methods without
reducing the compressive strength of hardened NaOH-activated slag
Seismic Design of Tialings Dam An Overview of its Evolution and New Challenges
This paper first provides an overview of the evolution of tailings dam engineering over the years. It then highlights key factors affecting seismic performance of tailings dams: such as site seismicity, foundation and damfill geotechnical characteristics, dam design, construction, operation and decommissioning, seismic slope stability, and dam rehabilitation. Finally, it reviews some of the recent trends that lead to new challenges to the engineering profession. These challenges include: coping with heightened public concern about dam safety; balancing potential conflict between seismic and environmental requirements; and addressing issues introduced by globalisation of the mining industry. Institutional responses and technological tools available to meet these challenges are outlined
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