2,447 research outputs found
Optimum design of composite laminates with thermal effects
An analytical approach to determine an optimum laminate for a variety of thermal and mechanical loading combinations is presented. The analysis is performed for a linear elastic material under static mechanical and uniform thermal loadings. The problem is restricted to a unit width and length laminate with angle orientations resulting in an orthotropic, symmetric, and balanced configuration. An objective function defining total strain energy, is formulated and an optimum laminate design determined subject to constraints on stiffness, average coefficient of thermal expansion, and strength. The objective function is formulated in terms of the orientation angles, number of plies, and material properties. The method presented has, in varying degrees, shown that the design of a laminate can be accomplished using strain energy minimization as the primary criteria. The results of various combinations of applied constraints in the optimized design process are presented and discussed
Local flow management/profile descent algorithm. Fuel-efficient, time-controlled profiles for the NASA TSRV airplane
The Local Flow Management/Profile Descent (LFM/PD) algorithm designed for the NASA Transport System Research Vehicle program is described. The algorithm provides fuel-efficient altitude and airspeed profiles consistent with ATC restrictions in a time-based metering environment over a fixed ground track. The model design constraints include accommodation of both published profile descent procedures and unpublished profile descents, incorporation of fuel efficiency as a flight profile criterion, operation within the performance capabilities of the Boeing 737-100 airplane with JT8D-7 engines, and conformity to standard air traffic navigation and control procedures. Holding and path stretching capabilities are included for long delay situations
An investigation of TNAV equipped aircraft in a simulated en route metering environment
This document presents the results of an effort to estimate how often a TNAV (Time Navigation) equipped aircraft could be given a TNAV clearance in the En Route Metering (ERM) system as a function of the percentage of arriving traffic which is TNAV equipped. A fast-time simulation of Denver Stapleton international arrival traffic in the Denver Air Route Traffic Control Center route structure, including en route metering operations, was used to develop data on estimated conflicts, clearance communications and fuel usage for traffic mixes of 25, 50, 75 and 100% TNAV equipped. This study supports an overall effort by NASA to assess the benefits and required technology for using TNAV-equipped aircraft in the ERM environment
Properties of implanted and CVD incorporated nitrogen-vacancy centers: preferential charge state and preferential orientation
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing
Full stress tensor measurement using colour centres in diamond
Stress and strain are important factors in determining the mechanical,
electronic, and optical properties of materials, relating to each other by the
material's elasticity or stiffness. Both are represented by second rank field
tensors with, in general, six independent components. Measurements of these
quantities are usually achieved by measuring a property that depends on the
translational symmetry and periodicity of the crystal lattice, such as optical
phonon energies using Raman spectroscopy, the electronic band gap using
cathodoluminescence, photoelasticity via the optical birefringence, or Electron
Back Scattering Diffraction (EBSD). A reciprocal relationship therefore exists
between the maximum sensitivity of the measurements and the spatial resolution.
Furthermore, of these techniques, only EBSD and off-axis Raman spectroscopy
allow measurement of all six components of the stress tensor, but neither is
able to provide full 3D maps. Here we demonstrate a method for measuring the
full stress tensor in diamond, using the spectral and optical polarization
properties of the photoluminescence from individual nitrogen vacancy (NV)
colour centres. We demonstrate a sensitivity of order 10 MPa, limited by local
fluctuations in the stress in the sample, and corresponding to a strain of
about 10^-5, comparable with the best sensitivity provided by other techniques.
By using the colour centres as built-in local sensors, the technique overcomes
the reciprocal relationship between spatial resolution and sensitivity and
offers the potential for measuring strains as small as 10^-9 at spatial
resolution of order 10 nm. Furthermore it provides a straightforward route to
volumetric stress mapping. Aside from its value in understanding strain
distributions in diamond, this new approach to stress and strain measurement
could be adapted for use in micro or nanoscale sensors.Comment: 12 pages, 5 figures - supplementary informations included in appendi
Landsat Data Continuity Mission - Launch Fever
The year 2013 will be an exciting period for those that study the Earth land surface from space, particularly those that observe and characterize land cover, land use, and the change of cover and use over time. Two new satellite observatories will be launched next year that will enhance capabilities for observing the global land surface. The United States plans to launch the Landsat Data Continuity Mission (LDCM) in January. That event will be followed later in the year by the European Space Agency (ESA) launch of the first Sentinel 2 satellite. Considered together, the two satellites will increase the frequency of opportunities for viewing the land surface at a scale where human impact and influence can be differentiated from natural change. Data from the two satellites will provide images for similar spectral bands and for comparable spatial resolutions with rigorous attention to calibration that will facilitate cross comparisons. This presentation will provide an overview of the LDCM satellite system and report its readiness for the January launch
Identity, community and care in online accounts of hereditary colorectal cancer syndrome
Sociological literature has explored how shifts in the point at which individuals may be designated as diseased impact upon experiences of ill health. Research has shown that experiences of being genetically “at risk” are shaped by and shape familial relations, coping strategies, and new forms of biosociality. Less is known about how living with genetic risk is negotiated in the everyday and over time, and the wider forms of identity, communities and care this involves. This article explores these arrangements drawing on online bloggers’ accounts of Familial Adenomatous Polyposis (FAP). We show how accounts of genetic risk co-exist with more palpable experiences of FAP in everyday life, notably the consequences of prophylactic surgeries. We consider how the act of blogging represents but also constitutes everyday experiences of hereditary cancer syndrome as simultaneously ordinary and exceptional, and reflect on the implications of our analysis for understanding experiences of genetic cancer risk
Production of oriented nitrogen-vacancy color centers in synthetic diamond
The negatively charged nitrogen-vacancy (NV-) center in diamond is an
attractive candidate for applications that range from magnetometry to quantum
information processing. Here we show that only a fraction of the nitrogen
(typically < 0.5 %) incorporated during homoepitaxial diamond growth by
Chemical Vapor Deposition (CVD) is in the form of undecorated NV- centers.
Furthermore, studies on CVD diamond grown on (110) oriented substrates show a
near 100% preferential orientation of NV- centers along only the [111] and
[-1-11] directions, rather than the four possible orientations. The results
indicate that NV centers grow in as units, as the diamond is deposited, rather
than by migration and association of their components. The NV unit of the NVH-
is similarly preferentially oriented, but it is not possible to determine
whether this defect was formed by H capture at a preferentially aligned NV
center or as a complete unit. Reducing the number of NV orientations from 4
orientations to 2 orientations should lead to increased optically-detected
magnetic resonance contrast and thus improved magnetic sensitivity in
ensemble-based magnetometry.Comment: 13 Pages (inlcuding suplementary information), 4 figure
Direct evaluation of pure graph state entanglement
We address the question of quantifying entanglement in pure graph states.
Evaluation of multipartite entanglement measures is extremely hard for most
pure quantum states. In this paper we demonstrate how solving one problem in
graph theory, namely the identification of maximum independent set, allows us
to evaluate three multipartite entanglement measures for pure graph states. We
construct the minimal linear decomposition into product states for a large
group of pure graph states, allowing us to evaluate the Schmidt measure.
Furthermore we show that computation of distance-like measures such as relative
entropy of entanglement and geometric measure becomes tractable for these
states by explicit construction of closest separable and closest product states
respectively. We show how these separable states can be described using
stabiliser formalism as well as PEPs-like construction. Finally we discuss the
way in which introducing noise to the system can optimally destroy
entanglement.Comment: 23 pages, 9 figure
- …