Isolated output for class-D dc amplifiers

Transformer-coupled output stage is used with pulse-width modulated class-D dc amplifiers. Circuit is comprised of two channels corresponding to negative and positive input signals. Amplitude of secondary-current triangular pulse is function of duration of driving pulse. Therefore, circuit converts pulse-width modulated driving signal to pulse-amplitude modulated signal

ARE STATED PREFERENCES INVARIANT TO THE PROSPECT OF REAL-MONEY CHOICE?

This paper reports on a choice experiment where respondents stated their preferences for different wetland parcels. The study used hypothetical surveys to measure respondents' preferences, but in one survey version respondents expected and received a follow-up question involving real monetary payments. The results indicate that those respondents who received hypothetical surveys that included a real-money question registered a different preference function from those respondents who received a survey that asked respondents to answer hypothetical questions only. The study finds that respondents may reverse their preferences for parcel attributes, such as public access to the parcel as related to presentation.Financial Economics,

SAR antenna calibration techniques

Calibration of SAR antennas requires a measurement of gain, elevation and azimuth pattern shape, boresight error, cross-polarization levels, and phase vs. angle and frequency. For spaceborne SAR antennas of SEASAT size operating at C-band or higher, some of these measurements can become extremely difficult using conventional far-field antenna test ranges. Near-field scanning techniques offer an alternative approach and for C-band or X-band SARs, give much improved accuracy and precision as compared to that obtainable with a far-field approach

The role of impulse parameters in force variability

One of the principle limitations of the human motor system is the ability to produce consistent motor responses. When asked to repeatedly make the same movement, performance outcomes are characterized by a considerable amount of variability. This occurs whether variability is expressed in terms of kinetics or kinematics. Variability in performance is of considerable importance because for tasks requiring accuracy it is a critical variable in determining the skill of the performer. What has long been sought is a description of the parameter or parameters that determine the degree of variability. Two general experimental protocals were used. One protocal is to use dynamic actions and record variability in kinematic parameters such as spatial or temporal error. A second strategy was to use isometric actions and record kinetic variables such as peak force produced. What might be the important force related factors affecting variability is examined and an experimental approach to examine the influence of each of these variables is provided

Rocketdyne PSAM: In-house enhancement/application

The development was initiated of the Probabilistic Design Analysis (PDA) Process for rocket engines. This will enable engineers a quantitative assessment of calculated reliability during the design process. The PDA will help choose better designs, make them more robust, and help decide on critical tests to help demonstrate key reliability issues to aid in improving the confidence of the engine capabilities. Rockedyne's involvement with the Composite Loads Spectra (CLS) and Probabilistic Structural Analysis Methodology (PSAM) contracts started this effort and are key elements in the on-going developments. Internal development efforts and hardware applications complement and extend the CLS and PSAM efforts. The completion of the CLS option work and the follow-on PSAM developments will also be integral parts of this methodology. A brief summary of these efforts is presented

Evaluating three frameworks for the value of information: adaptation to task characteristics and probabilistic structure

We identify, and provide an integration of, three frameworks for measuring the informativeness of cues in a multiple-cue judgment task. Cues can be ranked by information value according to expected information gain (Bayesian framework), cue-outcome correlation (Correlational framework), or ecological validity (Ecological framework). In three experiments, all frameworks significantly predicted information acquisition, with the Correlational (then the Bayesian) framework being most successful. Additionally, participants adapted successfully to task characteristics (cue cost, time pressure, and information limitations) – altering the gross amount of information acquired, but not responding to more subtle features of the cues’ information value that would have been beneficial. Rational analyses of our task environments indicate that participants' behavior can be considered successful from a boundedly rational standpoint

Norman Julius Zabusky OBITUARY

Norman Julius Zabusky, who laid the foundations for several critical advancements in nonlinear science and experimental mathematics, died of idiopathic pulmonary fibrosis on 5 February 2018 in Beersheba, Israel. He also made fundamental contributions to computational fluid dynamics and advocated the importance of visualization in science.Published versio

An Analysis of Kinetic Response Variability

Studies evaluating variability of force as a function of absolute force generated are synthesized. Inconsistencies in reported estimates of this relationship are viewed as a function of experimental constraints imposed. Typically, within-subject force variability increases at a negative accelerating rate with equal increments in force produced. Current pulse-step and impulse variability models are unable to accommodate this description, although the notion of efficiency is suggested as a useful construct to explain the description outlined

Probabilistic evaluation of SSME structural components

The application is described of Composite Load Spectra (CLS) and Numerical Evaluation of Stochastic Structures Under Stress (NESSUS) family of computer codes to the probabilistic structural analysis of four Space Shuttle Main Engine (SSME) space propulsion system components. These components are subjected to environments that are influenced by many random variables. The applications consider a wide breadth of uncertainties encountered in practice, while simultaneously covering a wide area of structural mechanics. This has been done consistent with the primary design requirement for each component. The probabilistic application studies are discussed using finite element models that have been typically used in the past in deterministic analysis studies