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High-efficiency large-angle Pancharatnam phase deflector based on dual-twist design

March 20, 2017
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Journal Article
Author:
Kun Gao
…
Published in:
Opt. Express, Vol. 25, No. 6, 20 March 2017.
Topic:
optics
R&D area:
R&D group:

Summary

We have previously shown through simulation that an optical beam deflector based on the Pancharatnam (geometric) phase can provide high efficiency with up to 80° deflection using a dual-twist structure for polarization-state control [Appl. Opt. 54, 10035 (2015)]. In this report, we demonstrate that its optical performance is as predicted and far beyond what could be expected for a conventional diffractive optical device. We provide details about construction and characterization of a ± 40° beam-steering device with 90% diffraction efficiency based on our dual-twist design at a 633nm wavelength.
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Summary

We have previously shown through simulation that an optical beam deflector based on the Pancharatnam (geometric) phase can provide high efficiency with up to 80° deflection using a dual-twist structure for polarization-state control [Appl. Opt. 54, 10035 (2015)]. In this report, we demonstrate that its optical performance is as predicted...

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High-efficiency large-angle Pancharatnam phase deflector based on dual-twist design

Wind information requirements for NextGen applications phase 4 final report

March 6, 2017
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Project Report
Author:
Christopher Edwards
…
Published in:
MIT Lincoln Laboratory Report ATC-431
Topic:
weather
R&D area:
R&D group:

Summary

The success of many NextGen applications with time-based control elements, such as Required Time of Arrival (RTA) at a meter fix under 4D-Trajectory Based Operations (4D-TBO/Time of Arrival Control (TOAC) procedures or compliance to an Assigned Spacing Goal (ASG) between aircraft under Interval Management (IM) procedures, are subject to the quality of the atmospheric forecast utilized by participating aircraft. Erroneous information derived from provided forecast data, such as the magnitude of future headwinds relative to the headwinds actually experienced during flight, or forecast data that is insufficient to fully describe the forthcoming atmospheric conditions, can significantly degrade the performance of an attempted procedure. The work described in this report summarizes the major activities conducted in Fiscal Year 2015.
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Summary

The success of many NextGen applications with time-based control elements, such as Required Time of Arrival (RTA) at a meter fix under 4D-Trajectory Based Operations (4D-TBO/Time of Arrival Control (TOAC) procedures or compliance to an Assigned Spacing Goal (ASG) between aircraft under Interval Management (IM) procedures, are subject to the...

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Wind information requirements for NextGen applications phase 4 final report

Detecting virus exposure during the pre-symptomatic incubation period using physiological data

March 3, 2017
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Journal Article
Author:
Lauren Milechin
…
Published in:
Science Translational Medicine (submitted), 3 March 2017.
Topic:
detection systems
R&D area:
R&D group:

Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning method to better detect asymptomatic states during the incubation period using subtle, sub-clinical physiological markers. Using high-resolution physiological data from non-human primate studies of Ebola and Marburg viruses, we pre-processed the data to reduce short-term variability and normalize diurnal variations, then provided these to a supervised random forest classification algorithm. In most subjects detection is achieved well before the onset of fever; subject cross-validation lead to 52±14h mean early detection (at >0.90 area under the receiver-operating characteristic curve). Cross-cohort tests across pathogens and exposure routes also lead to successful early detection (28±16h and 43±22h, respectively). We discuss which physiological indicators are most informative for early detection and options for extending this capability to lower data resolution and wearable, non-invasive sensors.
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Summary

Early pathogen exposure detection allows better patient care and faster implementation of public health measures (patient isolation, contact tracing). Existing exposure detection most frequently relies on overt clinical symptoms, namely fever, during the infectious prodromal period. We have developed a robust machine learning method to better detect asymptomatic states during...

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Detecting virus exposure during the pre-symptomatic incubation period using physiological data

Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

February 28, 2017
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Journal Article
Author:
Alla Ostrinskaya
…
Published in:
Rapid Commun. Mass Spectrom., Vol. 33, 2017, pp. 333-43.
Topic:
detection systems
R&D area:
R&D group:

Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN by mass spectrometry (MS) have not been fully investigated. METHODS: Atmospheric-pressure chemical-ionization mass spectrometry (APCI-MS) was used to detect ions characteristic of nitrated sugar alcohols. APCI time-of-flight mass spectrometry (APCI-TOF MS) and collision-induced dissociation tandem mass spectrometry (CID MS/MS) were used for confirmation of each ion assignment. In addition, the use of the chemical ionization reagent dichloromethane was investigated to improve sensitivity and selectivity for detection of MHN, SHN and XPN. RESULTS: All the nitrated sugar alcohols studied followed similar fragmentation pathways in the APCI source. MHN, SHN and XPN were detectable as fragment ions formed by the loss of NO2, HNO2, NO3, and CH2NO2 groups, and in the presence of dichloromethane chlorinated adduct ions were observed. It was determined that in MS/MS mode, chlorinated adducts of MHN and SHN had the lowest limits of detection (LODs), while for XPN the lowest LOD was for the [XPN-NO2]- fragment ion. Partially nitrated analogs of each of the three compounds were also present in the starting materials, and ions attributable to these compounds versus those formed from in-source fragmentation of MHN, SHN, and XPN were distinguished and assigned using liquid chromatography APCI-MS and ESI-MS. CONCLUSIONS: The APCI-MS technique provides a selective and sensitive method for the detection of nitrated sugar alcohols. The methods disclosed here will benefit the area of explosives trace detection for counterterrorism and forensics.
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Summary

RATIONALE: The nitrated sugar alcohols mannitol hexanitrate (MHN), sorbitol hexanitrate (SHN) and xylitol pentanitrate (XPN) are in the same class of compounds as the powerful military-grade explosive pentaerythritol tetranitrate (PETN) and the homemade explosive erythritol tetranitrate (ETN) but, unlike for PETN and ETN, ways to detect MHN, SHN and XPN...

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Characterization of nitrated sugar alcohols by atmospheric-pressure chemical-ionization mass spectrometry

High-resolution, high-throughput, CMOS-compatible electron beam patterning

February 26, 2017
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Conference Paper
Author:
Melissa A. Smith
…
Published in:
SPIE Advanced Lithography, 26 February - 2 March 2017.
Topic:
lithography
R&D area:
R&D group:

Summary

Two scanning electron beam lithography (SEBL) patterning processes have been developed, one positive and one negative tone. The processes feature nanometer-scale resolution, chemical amplification for faster throughput, long film life under vacuum, and sufficient etch resistance to enable patterning of a variety of materials with a metal-free (CMOS/MEMS compatible) tool set. These resist processes were developed to address two limitations of conventional SEBL resist processes: (1) low areal throughput and (2) limited compatibility with the traditional microfabrication infrastructure.
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Summary

Two scanning electron beam lithography (SEBL) patterning processes have been developed, one positive and one negative tone. The processes feature nanometer-scale resolution, chemical amplification for faster throughput, long film life under vacuum, and sufficient etch resistance to enable patterning of a variety of materials with a metal-free (CMOS/MEMS compatible) tool...

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High-resolution, high-throughput, CMOS-compatible electron beam patterning

SIAM data mining "brings it" to annual meeting

February 17, 2017
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Project Report
Author:
Jeremy Kepner
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Published in:
MIT Lincoln Laboratory Report 113081
Topic:
big data
R&D area:
R&D group:

Summary

The Data Mining Activity Group is one of SIAM's most vibrant and dynamic activity groups. To better share our enthusiasm for data mining with the broader SIAM community, our activity group organized six minisymposia at the 2016 Annual Meeting. These minisymposia included 48 talks organized by 11 SIAM members.
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Summary

The Data Mining Activity Group is one of SIAM's most vibrant and dynamic activity groups. To better share our enthusiasm for data mining with the broader SIAM community, our activity group organized six minisymposia at the 2016 Annual Meeting. These minisymposia included 48 talks organized by 11 SIAM members.

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SIAM data mining "brings it" to annual meeting

Picosecond kilohertz-class cryogenically cooled multistage Yb-doped chirped pulse amplifier

February 15, 2017
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Journal Article
Author:
Francis Morrissey
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Published in:
Opt. Lett., Vol. 42, No. 4, 15 February 2017, pp. 707-710.
Topic:
optics
R&D area:
R&D group:

Summary

A multistage cryogenic chirped pulse amplifier has been developed, utilizing two different Yb-doped gain materials in subsequent amplifier stages. A Yb:GSAG regenerative amplifier followed by a Yb:YAG power amplifier is able to deliver pulses with a broader bandwidth than a system using only one of these two gain media throughout. We demonstrate 90 mJ of pulse energy (113 W of average power) uncompressed and 67 mJ (84 W of average power) compressed at 1.25 kHz pulse repetition frequency, 3.0 ps FWHM Gaussian pulse width, and near-diffraction-limited (M^2 < 1.3) beam quality.
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Summary

A multistage cryogenic chirped pulse amplifier has been developed, utilizing two different Yb-doped gain materials in subsequent amplifier stages. A Yb:GSAG regenerative amplifier followed by a Yb:YAG power amplifier is able to deliver pulses with a broader bandwidth than a system using only one of these two gain media throughout...

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Picosecond kilohertz-class cryogenically cooled multistage Yb-doped chirped pulse amplifier

Learning to tutor from expert demonstrators via apprenticeship scheduling

February 4, 2017
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Conference Paper
Author:
Matthew C. Gombolay
…
Published in:
AAAI-17 Workshop on Human-Machine Collaborative Learning, 4 February 2017.
Topic:
machine learning
R&D area:
R&D group:

Summary

We have conducted a study investigating the use of automated tutors for educating players in the context of serious gaming (i.e., game designed as a professional training tool). Historically, researchers and practitioners have developed automated tutors through a process of manually codifying domain knowledge and translating that into a human-interpretable format. This process is laborious and leaves much to be desired. Instead, we seek to apply novel machine learning techniques to, first, learn a model from domain experts' demonstrations how to solve such problems, and, second, use this model to teach novices how to think like experts. In this work, we present a study comparing the performance of an automated and a traditional, manually-constructed tutor. To our knowledge, this is the first investigation using learning from demonstration techniques to learn from experts and use that knowledge to teach novices.
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Summary

We have conducted a study investigating the use of automated tutors for educating players in the context of serious gaming (i.e., game designed as a professional training tool). Historically, researchers and practitioners have developed automated tutors through a process of manually codifying domain knowledge and translating that into a human-interpretable...

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Learning to tutor from expert demonstrators via apprenticeship scheduling

WSR-88D chaff detection and characterization using an optimized hydrometeor classification algorithm

January 23, 2017
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Conference Paper
Author:
James M. Kurdzo
…
Published in:
18th Conf. on Aviation, Range, and Aerospace Meteorology, 23-26 January 2017.
Topic:
radar
R&D area:
R&D group:

Summary

Chaff presents multiple issues for aviation, air traffic controllers, and the FAA, including false weather identification and areas where flight paths may need to be altered. Chaff is a radar countermeasure commonly released from aircraft across the United States and is comprised of individual metallic strands designed to reflect certain wavelengths. Chaff returns tend to look similar to weather echoes in the reflectivity factor and radial velocity fields, and can appear as clutter, stratiform precipitation, or deep convection to the radar operator or radar algorithms. When polarimetric fields are taken into account, however, discrimination between weather and non-weather echoes has relatively high potential for success. In this work, the operational Hydrometeor Classification Algorithm (HCA) on the WSR-88D is modified to include a chaff class that can be used as input to a Chaff Detection Algorithm (CDA). This new class is designed using human-truthed chaff datasets for the collection and quantification of variable distributions, and the collected chaff cases are leveraged in the tuning of algorithm weights through the use of a metaheuristic optimization. A final CDA uses various image processing techniques to deliver a filtered output. A discussion regarding WSR-88D observations of chaff on a broad scale is provided, with particular attention given to observations of negative differential reflectivity during different stages of chaff fallout. Numerous cases are presented for analysis and characterization, both as an HCA class and as output from the filtered CDA.
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Summary

Chaff presents multiple issues for aviation, air traffic controllers, and the FAA, including false weather identification and areas where flight paths may need to be altered. Chaff is a radar countermeasure commonly released from aircraft across the United States and is comprised of individual metallic strands designed to reflect certain...

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WSR-88D chaff detection and characterization using an optimized hydrometeor classification algorithm

Learning by doing, High Performance Computing education in the MOOC era

January 17, 2017
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Journal Article
Author:
Julia Mullen
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Published in:
J. Parallel Distrib. Comput., Vol. 105, July 2017, pp. 105-15.
Topic:
high performance computing
R&D area:
R&D group:

Summary

The High Performance Computing (HPC) community has spent decades developing tools that teach practitioners to harness the power of parallel and distributed computing. To create scalable and flexible educational experiences for practitioners in all phases of a career, we turn to Massively Open Online Courses (MOOCs). We detail the design of a unique self-paced online course that incorporates a focus on parallel solutions, personalization, and hands-on practice to familiarize student-users with their target system. Course material is presented through the lens of common HPC use cases and the strategies for parallelizing them. Using personalized paths, we teach researchers how to recognize the alignment between scientific applications and traditional HPC use cases, so they can focus on learning the parallelization strategies key to their workplace success. At the conclusion of their learning path, students should be capable of achieving performance gains on their HPC system.
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Summary

The High Performance Computing (HPC) community has spent decades developing tools that teach practitioners to harness the power of parallel and distributed computing. To create scalable and flexible educational experiences for practitioners in all phases of a career, we turn to Massively Open Online Courses (MOOCs). We detail the design...

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Learning by doing, High Performance Computing education in the MOOC era
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