1,106 research outputs found
AMPA experimental communications systems
The program was conducted to demonstrate the satellite communication advantages of Adaptive Phased Array Technology. A laboratory based experiment was designed and implemented to demonstrate a low earth orbit satellite communications system. Using a 32 element, L-band phased array augmented with 4 sets of weights (2 for reception and 2 for transmission) a high speed digital processing system and operating against multiple user terminals and interferers, the AMPA system demonstrated: communications with austere user terminals, frequency reuse, communications in the face of interference, and geolocation. The program and experiment objectives are described, the system hardware and software/firmware are defined, and the test performed and the resultant test data are presented
Agar gel electrophoresis of amylases
Agar gel electrophoresis of amylase
Metaphoric coherence: Distinguishing verbal metaphor from `anomaly\u27
Theories and computational models of metaphor comprehension generally circumvent the question of metaphor versus âanomalyâ in favor of a treatment of metaphor versus literal language. Making the distinction between metaphoric and âanomalousâ expressions is subject to wide variation in judgment, yet humans agree that some potentially metaphoric expressions are much more comprehensible than others. In the context of a program which interprets simple isolated sentences that are potential instances of crossâmodal and other verbal metaphor, I consider some possible coherence criteria which must be satisfied for an expression to be âconceivableâ metaphorically. Metaphoric constraints on object nominals are represented as abstracted or extended along with the invariant structural components of the verb meaning in a metaphor. This approach distinguishes what is preserved in metaphoric extension from that which is âviolatedâ, thus referring to both âsimilarityâ and âdissimilarityâ views of metaphor. The role and potential limits of represented abstracted properties and constraints is discussed as they relate to the recognition of incoherent semantic combinations and the rejection or adjustment of metaphoric interpretations
Adaptive multibeam phased array design for a Spacelab experiment
The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio
End-to-End Differentiable Molecular Mechanics Force Field Construction
Molecular mechanics (MM) potentials have long been a workhorse of
computational chemistry. Leveraging accuracy and speed, these functional forms
find use in a wide variety of applications from rapid virtual screening to
detailed free energy calculations. Traditionally, MM potentials have relied on
human-curated, inflexible, and poorly extensible discrete chemical perception
rules (atom types) for applying parameters to molecules or biopolymers, making
them difficult to optimize to fit quantum chemical or physical property data.
Here, we propose an alternative approach that uses graph nets to perceive
chemical environments, producing continuous atom embeddings from which valence
and nonbonded parameters can be predicted using a feed-forward neural network.
Since all stages are built using smooth functions, the entire process of
chemical perception and parameter assignment is differentiable end-to-end with
respect to model parameters, allowing new force fields to be easily
constructed, extended, and applied to arbitrary molecules. We show that this
approach has the capacity to reproduce legacy atom types and can be fit to MM
and QM energies and forces, among other targets
A Case for Open Mission Systems in DOD Aircraft Avionics
The DOD is adopting open mission systems (OMS) as the future in the military aviation environment. OMS proponents promise reduced costs and truncated schedules through increased competition in the marketplace and reduced coding efforts. To the best of our knowledge, no studies have examined the success of these open architectures in the DOD. Therefore, we investigate costs and schedule for a recent DOD avionics OMS demonstration platform in comparison to 13 historically analogous programs
Quantifying the Effects of Aircraft Engine Upgrades on Operating and Support Costs
For fixed wing aircraft within the U.S. Air Force, Operating and Support (O&S) costs encompass a large portion of total life cycle costs. O&S costs include fuel, maintenance, and engine upgrades. To the authorsâ knowledge, no study to date has attempted to empirically quantify the realized effects of new aircraft engines on sustainment costs. Utilizing the Air Force Total Ownership Cost database, they focused on new engines appearing on the C-5s, C-130s, and C-135s. Although narrow in scope, results suggest newer engines have lower fuel costs. Maintenance costs for newer engines were not consistently higher or lower than the engines they replaced, although Contractor Logistics Support was not tracked by engine in this study. We found that savings from improved fuel efficiency tended to be greater than a potential increase in maintenance costs
Evaluation of Florida Physiciansâ Knowledge and Attitudes Toward Accessing the State Prescription Drug Monitoring Program as a Prescribing Tool
Objective The purpose of this study is to assess Florida physicians\u27 attitudes and knowledge toward accessing the state\u27s prescription drug monitoring program (PDMP). Design Five thousand medical doctors and osteopathic physicians licensed in Florida were randomly selected for a voluntary and anonymous 15-question self-administered survey approved by the Institutional Review Board. Surveys were distributed through U.S. postal service mail. Likert-scale questions were used to assess prior knowledge (1 = none to 5 = excellent) and attitudes toward accessing the PDMP (1 = strongly disagree to 5 = strongly agree). Results The study yielded a response rate of 7.8%, 71.5% of whom agreed or strongly agreed that the PDMP is a useful tool. Among participants that have access and answered the PDMP usefulness question, 94.8% agree or strongly agree that it is a useful tool. There were 63 out of 64 physicians (98.4%) who conducted 25 or more searches who agreed or strongly agreed that the PDMP is a useful tool for monitoring patients\u27 controlled substance histories. There were 72.5% of participants with access that answered the âdoctor shoppingâ question who agreed that âdoctor shoppingâ will decrease. Among the 64 most frequent PDMP users, 69.4% agreed or strongly agreed that they have prescribed fewer controlled substances after accessing the PDMP. Conclusions The study revealed that a majority of participants believe that the PDMP is a useful tool for monitoring patients\u27 controlled substance histories. More continuing education programs should be provided to Florida physicians to enhance their knowledge regarding PDMPs
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