23,231 research outputs found
Computer aided manual tracking
A scheme was developed to assist the human operator by augmenting an optic sight manual tracking loop with target rate estimates from a computer control algorithm which can either be a Kalman Filter or an alpha, beta, gamma filter. The idea is for the computer to provide rate tracking while the human operator is responsible for nullifying the tracking error. A simple schematic is shown to illustrate the implementation of this concept. A hybrid real-time man-in-loop simulation was used to compare the tracking performance of the same flight trajectory with or without this form of computer-aided track. Preliminary results show the advantage of computer-aided track against high speed aircraft at close range. However, good tracking before target state estimator maturity becomes more critical for aided track than without. Results are presented for a constant velocity flight trajectory
In the eye of the storm: T cell behavior in the inflammatory microenvironment.
Coordinated unfolding of innate and adaptive immunity is key to the development of protective immune responses. This functional integration occurs within the inflamed tissue, a microenvironment enriched with factors released by innate and subsequently adaptive immune cells and the injured tissue itself. T lymphocytes are key players in the ensuing adaptive immunity and their proper function is instrumental to a successful outcome of immune protection. The site of inflammation is a "harsh" environment in which T cells are exposed to numerous factors that might influence their behavior. Low pH and oxygen concentration, high lactate and organic acid content as well as free fatty acids and reactive oxygen species are found in the inflammatory microenvironment. All these components affect T cells as well as other immune cells during the immune response and impact on the development of chronic inflammation. We here overview the effects of a number of factors present in the inflammatory microenvironment on T cell function and migration and discuss the potential relevance of these components as targets for therapeutic intervention in autoimmune and chronic inflammatory diseases
Development of improved adhesives for use at cryogenic temperatures to minus423 deg F Final summary report, 11 Jul. 1963 - 31 Aug. 1965
Improved polyurethane and epoxy resins for use as adhesives at cryogenic temperature
Evaluating load balancing policies for performance and energy-efficiency
Nowadays, more and more increasingly hard computations are performed in
challenging fields like weather forecasting, oil and gas exploration, and
cryptanalysis. Many of such computations can be implemented using a computer
cluster with a large number of servers. Incoming computation requests are then,
via a so-called load balancing policy, distributed over the servers to ensure
optimal performance. Additionally, being able to switch-off some servers during
low period of workload, gives potential to reduced energy consumption.
Therefore, load balancing forms, albeit indirectly, a trade-off between
performance and energy consumption. In this paper, we introduce a syntax for
load-balancing policies to dynamically select a server for each request based
on relevant criteria, including the number of jobs queued in servers, power
states of servers, and transition delays between power states of servers. To
evaluate many policies, we implement two load balancers in: (i) iDSL, a
language and tool-chain for evaluating service-oriented systems, and (ii) a
simulation framework in AnyLogic. Both implementations are successfully
validated by comparison of the results.Comment: In Proceedings QAPL'16, arXiv:1610.0769
Frequency Dependent Viscosity Near the Critical Point: The Scale to Two Loop Order
The recent accurate measurements of Berg, Moldover and Zimmerli of the
viscoelastic effect near the critical point of xenon has shown that the scale
factor involved in the frequency scaling is about twice the scale factor
obtained theoretically. We show that this discrepancy is a consequence of using
first order perturbation theory. Including two loop contribution goes a long
way towards removing the discrepancy.Comment: No of pages:7,Submitted to PR-E(Rapid Communication),No of EPS
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An analytical packet/flow-level modelling approach for wireless LANs with Quality-of-Service support
We present an analytical packet/flow-level modelling approach for the performance analysis of IEEE 802.11e WLAN, where we explicitly take into account QoS differentiation mechanisms based on minimum contention window size values and Arbitration InterFrame Space (AIFS) values, as included in the Enhanced Distributed Channel Access (EDCA) protocol of the 802.11e standard. We first enhance the packet-level approach previously used for best-effort WLANs to include traffic classes with different QoS requirements. The packet-level model approach yields service weights that discriminate among traffic classes. From these observations, the packet/flow-level model for 802.11e is the \textit{generalized} discriminatory processor-sharing (GDPS) queueing model where the state-dependent system capacity is distributed among active traffic classes according to state-dependent priority weights. Extensive simulations show that the discriminatory processor-sharing model closely represents the flow behavior of 802.11e
Entropy-based analysis of the number partitioning problem
In this paper we apply the multicanonical method of statistical physics on
the number-partitioning problem (NPP). This problem is a basic NP-hard problem
from computer science, and can be formulated as a spin-glass problem. We
compute the spectral degeneracy, which gives us information about the number of
solutions for a given cost and cardinality . We also study an extension
of this problem for partitions. We show that a fundamental difference on
the spectral degeneracy of the generalized () NPP exists, which could
explain why it is so difficult to find good solutions for this case. The
information obtained with the multicanonical method can be very useful on the
construction of new algorithms.Comment: 6 pages, 4 figure
Information retrieval system
Generalized information storage and retrieval system capable of generating and maintaining a file, gathering statistics, sorting output, and generating final reports for output is reviewed. File generation and file maintenance programs written for the system are general purpose routines
Non equilibrium statistical physics with fictitious time
Problems in non equilibrium statistical physics are characterized by the
absence of a fluctuation dissipation theorem. The usual analytic route for
treating these vast class of problems is to use response fields in addition to
the real fields that are pertinent to a given problem. This line of argument
was introduced by Martin, Siggia and Rose. We show that instead of using the
response field, one can, following the stochastic quantization of Parisi and
Wu, introduce a fictitious time. In this extra dimension a fluctuation
dissipation theorem is built in and provides a different outlook to problems in
non equilibrium statistical physics.Comment: 4 page
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