6,398 research outputs found
IRVE-II Post-Flight Trajectory Reconstruction
NASA s Inflatable Re-entry Vehicle Experiment (IRVE) II successfully demonstrated an inflatable aerodynamic decelerator after being launched aboard a sounding rocket from Wallops Flight Facility (WFF). Preliminary day of flight data compared well with pre-flight Monte Carlo analysis, and a more complete trajectory reconstruction performed with an Extended Kalman Filter (EKF) approach followed. The reconstructed trajectory and comparisons to an attitude solution provided by NASA Sounding Rocket Operations Contract (NSROC) personnel at WFF are presented. Additional comparisons are made between the reconstructed trajectory and pre and post-flight Monte Carlo trajectory predictions. Alternative observations of the trajectory are summarized which leverage flight accelerometer measurements, the pre-flight aerodynamic database, and on-board flight video. Finally, analysis of the payload separation and aeroshell deployment events are presented. The flight trajectory is reconstructed to fidelity sufficient to assess overall project objectives related to flight dynamics and overall, IRVE-II flight dynamics are in line with expectation
Scalable solid-state quantum processor using subradiant two-atom states
We propose a realization of a scalable, high-performance quantum processor
whose qubits are represented by the ground and subradiant states of effective
dimers formed by pairs of two-level systems coupled by resonant dipole-dipole
interaction. The dimers are implanted in low-temperature solid host material at
controllable nanoscale separations. The two-qubit entanglement either relies on
the coherent excitation exchange between the dimers or is mediated by external
laser fields.Comment: 4 pages, 3 figure
Impact of Vehicle Flexibility on IRVE-II Flight Dynamics
The Inflatable Re-entry Vehicle Experiment II (IRVE-II) successfully launched from Wallops Flight Facility (WFF) on August 17, 2009. The primary objectives of this flight test were to demonstrate inflation and re-entry survivability, assess the thermal and drag performance of the reentry vehicle, and to collect flight data for refining pre-flight design and analysis tools. Post-flight analysis including trajectory reconstruction outlined in O Keefe3 demonstrated that the IRVE-II Research Vehicle (RV) met mission objectives but also identified a few anomalies of interest to flight dynamics engineers. Most notable of these anomalies was high normal acceleration during the re-entry pressure pulse. Deflection of the inflatable aeroshell during the pressure pulse was evident in flight video and identified as the likely cause of the anomaly. This paper provides a summary of further post-flight analysis with particular attention to the impact of aeroshell flexibility on flight dynamics and the reconciliation of flight performance with pre-flight models. Independent methods for estimating the magnitude of the deflection of the aeroshell experienced on IRVE-II are discussed. The use of the results to refine models for pre-flight prediction of vehicle performance is then described
Entanglement Swapping Chains for General Pure States
We consider entanglement swapping schemes with general (rather than
maximally) entangled bipartite states of arbitary dimension shared pairwise
between three or more parties in a chain. The intermediate parties perform
generalised Bell measurements with the result that the two end parties end up
sharing a entangled state which can be converted into maximally entangled
states. We obtain an expression for the average amount of maximal entanglement
concentrated in such a scheme and show that in a certain reasonably broad class
of cases this scheme is provably optimal and that, in these cases, the amount
of entanglement concentrated between the two ends is equal to that which could
be concentrated from the weakest link in the chain.Comment: 18 pages, 5 figure
Reinventing the Utility for DERs: A Proposal for a DSO-Centric Retail Electricity Market
The increasing penetration of intermittent renewables, storage devices, and
flexible loads is introducing operational challenges in distribution grids. The
proper coordination and scheduling of these resources using a distributed
approach is warranted, and can only be achieved through local retail markets
employing transactive energy schemes. To this end, we propose a
distribution-level retail market operated by a Distribution System Operator
(DSO), which schedules DERs and determines the real-time distribution-level
Locational Marginal Price (d-LPM). The retail market is built using a
distributed Proximal Atomic Coordination (PAC) algorithm, which solves the
optimal power flow model while accounting for network physics, rendering
locationally and temporally varying d-LMPs. A numerical study of the market
structure is carried out via simulations of the IEEE-123 node network using
data from ISO-NE and Eversource in Massachusetts, US. The market performance is
compared to existing retail practices, including demand response (DR) with
no-export rules and net metering. The DSO-centric market increases DER
utilization, permits continual market participation for DR, lowers electricity
rates for customers, and eliminates the subsidies inherent to net metering
programs. The resulting lower revenue stream for the DSO highlights the
evolving business model of the modern utility, moving from commoditized markets
towards performance-based ratemaking
Flip Graphs of Degree-Bounded (Pseudo-)Triangulations
We study flip graphs of triangulations whose maximum vertex degree is bounded
by a constant . In particular, we consider triangulations of sets of
points in convex position in the plane and prove that their flip graph is
connected if and only if ; the diameter of the flip graph is .
We also show that, for general point sets, flip graphs of pointed
pseudo-triangulations can be disconnected for , and flip graphs of
triangulations can be disconnected for any . Additionally, we consider a
relaxed version of the original problem. We allow the violation of the degree
bound by a small constant. Any two triangulations with maximum degree at
most of a convex point set are connected in the flip graph by a path of
length , where every intermediate triangulation has maximum degree
at most .Comment: 13 pages, 12 figures, acknowledgments update
Affinity flow fractionation of cells via transient interactions with asymmetric molecular patterns
Flow fractionation of cells using physical fields to achieve lateral displacement finds wide applications, but its extension to surface molecule-specific separation requires labeling. Here we demonstrate affinity flow fractionation (AFF) where weak, short-range interactions with asymmetric molecular patterns laterally displace cells in a continuous, label-free process. We show that AFF can directly draw neutrophils out of a continuously flowing stream of blood with an unprecedented 400,000-fold depletion of red blood cells, with the sorted cells being highly viable, unactivated, and functionally intact. The lack of background erythrocytes enabled the use of AFF for direct enumeration of neutrophils by a downstream detector, which could distinguish the activation state of neutrophils in blood. The compatibility of AFF with capillary microfluidics and its ability to directly separate cells with high purity and minimal sample preparation will facilitate the design of simple and portable devices for point-of-care diagnostics and quick, cost-effective laboratory analysis
Flight Performance of the Inflatable Reentry Vehicle Experiment II
The Inflatable Reentry Vehicle Experiment II launched August 17, 2009, from NASA Wallops Flight Facility. The three mission objectives were to demonstrate inflation and re-entry survivability, assess the thermal and drag performance of the reentry vehicle, and to collect flight data for comparison with analysis and design techniques used in vehicle development. The flight was a complete success, with the re-entry vehicle separating cleanly from the launcher, inflating as planned, and demonstrating stable flight through reentry and descent while on-board systems telemetered video and flight performance data to the ground
SN 2013ab : A normal type IIP supernova in NGC 5669
We present densely-sampled ultraviolet/optical photometric and low-resolution
optical spectroscopic observations of the type IIP supernova 2013ab in the
nearby (24 Mpc) galaxy NGC 5669, from 2 to 190d after explosion.
Continuous photometric observations, with the cadence of typically a day to one
week, were acquired with the 1-2m class telescopes in the LCOGT network, ARIES
telescopes in India and various other telescopes around the globe. The light
curve and spectra suggest that the SN is a normal type IIP event with a plateau
duration of days with mid plateau absolute visual magnitude of
-16.7, although with a steeper decline during the plateau (0.92 mag 100 d in band) relative to other archetypal SNe of similar brightness.
The velocity profile of SN 2013ab shows striking resemblance with those of SNe
1999em and 2012aw. Following the Rabinak & Waxman (2011) prescription, the
initial temperature evolution of the SN emission allows us to estimate the
progenitor radius to be 800 R, indicating that the SN
originated from a red supergiant star. The distance to the SN host galaxy is
estimated to be 24.3 Mpc from expanding photosphere method (EPM). From our
observations, we estimate that 0.064 M of Ni was synthesized
in the explosion. General relativistic, radiation hydrodynamical modeling of
the SN infers an explosion energy of erg, a progenitor
mass (at the time of explosion) of M and an initial radius
of R.Comment: 22 pages, 18 figures, 5 tables. Accepted for publication in MNRA
Assessing the irradiance levels of phototherapy devices in Jos, north central, Nigeria
Background: Neonatal jaundice (NNJ) remains a major cause of neonatal morbidity and mortality in Nigeria with significant contribution to the global figures. Effective phototherapy can reduce the complications associated with NNJ. The effectiveness of a phototherapy device (PD) depends mainly on the emitted irradiance of the device. We, therefore, assessed the irradiance of the PDs in Jos, North Central Nigeria in order to determine the effectiveness of the devices and to highlight the need for routine assessment of irradiance levels of PDs in low-middle income settings.Methods: This was a cross- sectional study involving 14 hospitals with a total of 38 functional PDs comprising of 25 (65.8%) locally fabricated, eight (21.0%) light- emitting diode (LED) and five (13.2%) conventional patented devices. The irradiance was measured using the BiliBlanket® light meter II.Results: The irradiance of the PDs ranged from 2 to 102μW/cm2/nm with a median value of 10.6 (IQR 6-18μW/cm2/nm). Sixteen devices (42.1%) had a suboptimal irradiance (<10μW/cm2/nm); while only five (13.2%) provided irradiance at the intensive level (≥30μW/cm2/nm). The mean distance between the babies and phototherapy lights was 35.1±12.7cm (range 15-70cm).Conclusions: A significant proportion of the PDs in Jos delivered suboptimal irradiance which could reduce the effectiveness of the phototherapy. The irradiance of PDs needs to be assessed regularly and measures should be instituted to improve the irradiance to the optimum level in order to reduce the burden of kernicterus
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