665 research outputs found
Remote sensing at the Broussard Mounds site: a prehistoric multi-mound site located in the Lower Mississippi River Valley
In order to test the effectiveness of various types of remote sensing for applications in archaeology, remote sensing data in the form of color infrared aerial photography, Airborne Terrestrial Applications Sensor (ATLAS) imagery, 35mm (black and white) and (color) infrared photography, and ground penetrating radar (GPR) were used at the Broussard Mounds site. Additionally, light detection and ranging (LIDAR) digital elevation imagery was downloaded, processed, and interpreted. Anomalies identified through the use of remote sensing were relocated geospatially and archaeological testing procedures were used to verify the presence of subsurface archaeological remains and to document the prehistoric cultural components at the site. Materials recovered from prehistoric cultural features at Mound B were attributed to the Smithfield Phase of the early Marksville Period. The excavations near Mound A identified a remnant of a late nineteenth or early twentieth century brick structure. The types of remote sensing used at the Broussard Mounds site were found to have mixed results for locating archaeological features. The color infrared aerial photography and ATLAS data were not efficient because of the effects of seasonal vegetation, but the ATLAS imagery showed promise for identifying historic structures using the short wave infrared and thermal bands of the sensor. 35mm photography required greater control in order to be more effective, but also showed potential for locating historic archaeological features. GPR data indicated numerous anomalies with possible associations with archaeological features. However, excavations only verified archaeological features at three of the locations. Several other GPR anomalies were tested, but could not be confirmed archaeologically
Extending the memory times of trapped-ion qubits with error correction and global entangling operations
The technical demands to perform quantum error correction are considerable.
The task requires the preparation of a many-body entangled state, together with
the ability to make parity measurements over subsets of the physical qubits of
the system to detect errors. Here we propose two trapped-ion experiments to
realise error-correcting codes of variable size to protect a single encoded
qubit from dephasing errors. Novel to our schemes is the use of a global
entangling phase gate, which could be implemented in both Penning traps and
Paul traps. We make use of this entangling operation to significantly reduce
the experimental complexity of state preparation and syndrome measurements. We
also show, in our second scheme, that storage times can be increased further by
repeatedly teleporting the logical information between two codes supported by
the same ion Coulomb crystal to learn information about the locations of
errors. We estimate that a logical qubit encoded in such a crystal will
maintain high coherence for times more than an order of magnitude longer than
each physical qubit would.Comment: 18 pages, 8 figures. The authors list has changed since the first
version of this draf
Trapped-ion quantum error-correcting protocols using only global operations
Quantum error-correcting codes are many-body entangled states that are
prepared and measured using complex sequences of entangling operations. Each
element of such an entangling sequence introduces noise to delicate quantum
information during the encoding or reading out of the code. It is important
therefore to find efficient entangling protocols to avoid the loss of
information. Here we propose an experiment that uses only global entangling
operations to encode an arbitrary logical qubit to either the five-qubit
repetition code or the five-qubit code, with a six-ion Coulomb crystal
architecture in a Penning trap. We show that the use of global operations
enables us to prepare and read out these codes using only six and ten global
entangling pulses, respectively. The proposed experiment also allows the
acquisition of syndrome information during readout. We provide a noise analysis
for the presented protocols, estimating that we can achieve a six-fold
improvement in coherence time with noise as high as on each
entangling operation.Comment: 7 pages, 4 figures, published version, comments are welcom
Exploration of Data Science Toolbox and Predictive Models to Detect and Prevent Medicare Fraud, Waste, and Abuse
The Federal Department of Health and Human Services spends approximately 30 to $110 billion is some form of fraud, waste, or abuse (FWA). Despite the Federal Government’s ongoing auditing efforts, fraud, waste, and abuse is rampant and requires modern machine learning approaches to generalize and detect such patterns. New and novel machine learning algorithms offer hope to help detect fraud, waste, and abuse. The existence of publicly accessible datasets complied by The Centers for Medicare & Medicaid Services (CMS) contain vast quantities of structured data. This data, coupled with industry standardized billing codes provides many opportunities for the application of machine learning for fraud, waste, and abuse detection. This research aims to develop a new model utilizing machine learning to generalize the patterns of fraud, waste, and abuse in Medicare. This task is accomplished by linking provider and payment data with the list of excluded individuals and entities to train an Isolation Forest algorithm on previously fraudulent behavior. Results indicate anomalous instances occurring in 0.2% of all analyzed claims, demonstrating machine learning models’ predictive ability to detect FWA
An Investigation of Flames, Deflagrations, and Detonations in High-Speed Flows
A comprehensive understanding of the fundamental physics underlying combustion and detonations in turbulent and high-speed flows is crucial to the design of robust ramjet, scramjet, and detonation engines. This work uses high-fidelity, multidimensional numerical simulations to investigate flame stability and deflagration-to-detonation transition (DDT) mechanisms in supersonic reactive flows. The study consists of four major sections.
The first section discusses the acceleration of a flame in a channel with obstacles and its transition from a laminar, expanding flame to a turbulent deflagration and eventual detonation. As the flame accelerates, a highly dynamic, shock-heated region forms ahead of the flame. Shock collisions and reflections focus energy in localized volumes of unburned gas at timescales that are small relative to the acoustic timescale of the unburned gas. The rapid deposition of energy causes the unburned gas to detonate through an energy-focusing mechanism that has elements of both direct initiation and detonation in a gradient of reactivity.
The second section describes how the blockage of a channel with regularly spaced obstacles, analogous to the igniter in a detonation engine, affects flame acceleration and turbulence in the region ahead of the accelerating flame. The rate of flame acceleration, time and distance to DDT, and detonation mechanism are compared for channels with high, medium, and low blockage ratios. Stochasticity and uncertainty in the numerical solutions are discussed.
In the third section, the stability of premixed flames at high supersonic speeds in a constant-area combustor is investigated. After autoignition of the fuel-oxidizer mixture in the boundary layer at the combustor walls, the flame front eventually becomes unstable due to a Rayleigh-Taylor (RT) instability at the interface between burned and unburned gas. The turbulent flame front transitions to a detonation through the energy-focusing mechanism when a shock passes through the flame and amplifies its energy release.
The final section discusses the effect of inflow Mach number in the supersonic combustor on ignition, flame stability, and transition to detonation of a premixed flame. Timescales for growth of the RT instability and detonation initiation increase rapidly with flow speed, but, qualitatively, flame evolution is independent of Mach number
Heteroleptic samarium(III) halide complexes probed by fluorescence-detected L3-edge X-ray absorption spectroscopy
Addition of various oxidants to the near-linear Sm(II) complex [Sm(N††)2] (1), where N††is the bulky bis(triisopropylsilyl)amide ligand {N(SiiPr3)2}, afforded a family of heteroleptic three-coordinate Sm(III) halide complexes, [Sm(N††)2(X)] (X = F, 2-F; Cl, 2-Cl; Br, 2-Br; I, 2-I). In addition, the trinuclear cluster [{Sm(N††)}3(μ2-I)3(μ3-I)2] (3), which formally contains one Sm(II) and two Sm(III) centres, was isolated during the synthesis of 2-I. Complexes 2-X are remarkably stable towards ligand redistribution, which is often a facile process for heteroleptic complexes of smaller monodentate ligands in lanthanide chemistry, including the related bis(trimethylsilyl)amide {N(SiMe3)2} (N′′). Complexes 2-X and 3 have been characterised by single crystal X-ray diffraction, elemental analysis, multinuclear NMR, FTIR and electronic spectroscopy. The Lα1 fluorescence-detected X-ray absorption spectrum recorded at the Sm L3-edge for 2-X exhibited a resolved pre-edge peak defined as an envelope quadrupole-allowed 2p → 4f transition. The X-ray absorption spectral features were successfully reproduced using time-dependent density functional theoretical (TD-DFT) calculations that synergistically supports the experimental observations as well as the theoretical model upon which the electronic structure and bonding in lanthanide complexes is derived
Farm-Scale Crop Yield Prediction from Multi-Temporal Data Using Deep Hybrid Neural Networks
publishedVersio
Quantitative three-dimensional local order analysis of nanomaterials through electron diffraction
Structure-property relationships in ordered materials have long been a core principle in materials design. However, the introduction of disorder into materials provides structural flexibility and thus access to material properties that are not attainable in conventional, ordered materials. To understand disorder-property relationships, the disorder – i.e., the local ordering principles – must be quantified. Local order can be probed experimentally by diffuse scattering. The analysis is notoriously difficult, especially if only powder samples are available. Here, we combine the advantages of three-dimensional electron diffraction – a method that allows single crystal diffraction measurements on sub-micron sized crystals – and three-dimensional difference pair distribution function analysis (3D-ΔPDF) to address this problem. In this work, we compare the 3D-ΔPDF from electron diffraction data with those obtained from neutron and x-ray experiments of yttria-stabilized zirconia (Zr0.82Y0.18O1.91) and demonstrate the reliability of the proposed approach
Constraining the star formation rate in the Solar neighbourhood with star clusters
This paper investigates the star formation rate (SFR) in the Solar
neighbourhood. First, we build the local age distribution function (ADF) with
an updated sample of 442 star clusters located at less than 1\,kpc from the
Sun. Next, we define the SFR, compute the individual mass evolution of a
population of artificial clusters covering the broad range of parameters
observed in actual clusters, and assume 100\,\ms\ as the low-mass limit for
effective cluster observation. This leads to a simulated ADF, which is compared
to the low-noise Solar neighbourhood ADF. The best match corresponds to a
non-constant SFR presenting two conspicuous excesses for ages \,Myr and
between 220-600\,Myr (the local starburst). The average formation rate is
\bar{SFR}\approx(2500\pm500)\,\mmy, corresponding to the average surface
formation rate \bar{\ssfr}\approx(790\pm160)\,\mmk. These values are
consistent with the formation rate inferred from embedded clusters (ECs), but
much lower (\la16%) than that implied by field stars. Both the local
starburst and the recent star formation period require
to be described. The simulations show that
of the clusters created in the Solar neighbourhood do not survive
the first 10\,Myr, which is consistent with the rate of EC dissolution.Comment: Accepted by MNRA
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