3,699 research outputs found
"The global telecommunications infrastructure: European Community (Union) telecommunications developments"
[From the Introduction]. Information, electronics, and telecommunication technologies promise to create communications networks of greatly expanded capacity capable of moving messages across interconnected wired and wireless systems almost anywhere in the world. Such global systems will profoundly affect the economic and social life of all countries. For those countries and economic sectors with a history of significant involvement in electronics, computers, multimedia, and telecommunications, early and timely deployment of state-of-the-art infrastructure may be a matter of prime importance. Many individual countries have made or are making changes intended to accelerate movement toward an information society, in large part because they recognize that a strategic competitive edge in the world economy will likely depend increasingly upon the availability, use, and exploitation of information. A major participant in the information race is the European Union (EU), formerly the European Community. The Commission of the European Union (Commission) has launched a strong push to adopt a common strategy for the creation of a European information society driven by a European information infrastructure. This strategy is aimed at bridging individual initiatives being pursued by EU Member States. [1. Member States now in the Union include the following: Belgium, Denmark, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal, Spain, and the United Kingdom, Austria, Finland and Sweden joined the Union on January 1, 1995.1
Clinical ophthalmic ultrasound improvements
The use of digital synthetic aperture techniques to obtain high resolution ultrasound images of eye and orbit was proposed. The parameters of the switched array configuration to reduce data collection time to a few milliseconds to avoid eye motion problems in the eye itself were established. An assessment of the effects of eye motion on the performance of the system was obtained. The principles of synthetic techniques are discussed. Likely applications are considered
Statistical Analysis of Thermal Analysis Margin
NASA Goddard Space Flight Center requires that each project demonstrate a minimum of 5 C margin between temperature predictions and hot and cold flight operational limits. The bounding temperature predictions include worst-case environment and thermal optical properties. The purpose of this work is to: assess how current missions are performing against their pre-launch bounding temperature predictions and suggest any possible changes to the thermal analysis margin rule
Riccati parameter modes from Newtonian free damping motion by supersymmetry
We determine the class of damped modes \tilde{y} which are related to the
common free damping modes y by supersymmetry. They are obtained by employing
the factorization of Newton's differential equation of motion for the free
damped oscillator by means of the general solution of the corresponding Riccati
equation together with Witten's method of constructing the supersymmetric
partner operator. This procedure leads to one-parameter families of (transient)
modes for each of the three types of free damping, corresponding to a
particular type of %time-dependent angular frequency. %time-dependent,
antirestoring acceleration (adding up to the usual Hooke restoring
acceleration) of the form a(t)=\frac{2\gamma ^2}{(\gamma t+1)^{2}}\tilde{y},
where \gamma is the family parameter that has been chosen as the inverse of the
Riccati integration constant. In supersymmetric terms, they represent all those
one Riccati parameter damping modes having the same Newtonian free damping
partner modeComment: 6 pages, twocolumn, 6 figures, only first 3 publishe
Mission Life Thermal Analysis and Environment Correlation for the Lunar Reconnaissance Orbiter
Standard thermal analysis practices include stacking worst-case conditions including environmental heat loads, thermo-optical properties and orbital beta angles. This results in the design being driven by a few bounding thermal cases, although those cases may only represent a very small portion of the actual mission life. The NASA Goddard Space Flight Center Thermal Branch developed a procedure to predict the flight temperatures over the entire mission life, assuming a known beta angle progression, variation in the thermal environment, and a degradation rate in the coatings. This was applied to the Global Precipitation Measurement core spacecraft. In order to assess the validity of this process, this work applies the similar process to the Lunar Reconnaissance Orbiter. A flight-correlated thermal model was exercised to give predictions of the thermal performance over the mission life. These results were then compared against flight data from the first two years of the spacecraft s use. This is used to validate the process and to suggest possible improvements for future analyses
The GNSS-R Eddy Experiment II: L-band and Optical Speculometry for Directional Sea-Roughness Retrieval from Low Altitude Aircraft
We report on the retrieval of directional sea-roughness (the full directional
mean square slope, including MSS, direction and isotropy) through inversion of
Global Navigation Satellite System Reflections (GNSS-R) and SOlar REflectance
Speculometry (SORES)data collected during an experimental flight at 1000 m. The
emphasis is on the utilization of the entire Delay-Doppler Map (for GNSS-R) or
Tilt Azimuth Map (for SORES) in order to infer these directional parameters.
Obtained estimations are analyzed and compared to Jason-1 measurements and the
ECMWF numerical weather model.Comment: Proceedings from the 2003 Workshop on Oceanography with GNSS
Reflections, Barcelona, Spain, 200
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Computer Security Checklist for Non-Security Technology Professionals
Networked computers and electronic data storage make computer security a fundamental component of a company’s survival. Security incidents can cause reputation damage, loss customers, or even liability. Companies that are unable or unwilling to hire certified security professionals often rely on non-security IT professionals for assistance. This paper provides a checklist the non-security professional can use to assist the company in the critical areas of conducting risk analysis, performing vulnerability assessments, educating employees and developing computer security policies and procedure
Forced Oscillation Wind Tunnel Testing for FASER Flight Research Aircraft
As unmanned air vehicles (UAVs) continue to expand their flight envelopes into areas of high angular rate and high angle of attack, modeling the complex unsteady aerodynamics for simulation in these regimes has become more difficult using traditional methods. The goal of this experiment was to improve the current six degree-of-freedom aerodynamic model of a small UAV by replacing the analytically derived damping derivatives with experimentally derived values. The UAV is named the Free-flying Aircraft for Sub-scale Experimental Research, FASER, and was tested in the NASA Langley Research Center 12- Foot Low-Speed Tunnel. The forced oscillation wind tunnel test technique was used to measure damping in the roll and yaw axes. By imparting a variety of sinusoidal motions, the effects of non-dimensional angular rate and reduced frequency were examined over a large range of angle of attack and side-slip combinations. Tests were performed at angles of attack from -5 to 40 degrees, sideslip angles of -30 to 30 degrees, oscillation amplitudes from 5 to 30 degrees, and reduced frequencies from 0.010 to 0.133. Additionally, the effect of aileron or elevator deflection on the damping coefficients was examined. Comparisons are made of two different data reduction methods used to obtain the damping derivatives. The results show that the damping derivatives are mainly a function of angle of attack and have dependence on the non-dimensional rate and reduced frequency only in the stall/post-stall regim
Cross-Kerr nonlinearity between continuous-mode coherent states and single photons
Weak cross-Kerr nonlinearities between single photons and coherent states are
the basis for many applications in quantum information processing. These
nonlinearities have so far mainly been discussed in terms of highly idealized
single-mode models. We develop a general theory of the interaction between
continuous-mode photonic pulses and apply it to the case of a single photon
interacting with a coherent state. We quantitatively study the validity of the
usual single-mode approximation using the concepts of fidelity and conditional
phase. We show that high fidelities, non-zero conditional phases and high
photon numbers are compatible, under conditions where the pulses fully pass
through each other and where unwanted transverse-mode effects are suppressed.Comment: 8 pages, 2 figures, more general results in section V
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