A study on task difficulty and acceleration stress

The results of two experiments which relate to task difficulty and the effects of environmental stress on tracking performance are discussed and compared to subjective evaluations. The first experiment involved five different sum of sine tracking tasks which humans tracked both in a static condition and under a 5 Gz acceleration stress condition. The second experiment involved similar environmental stress conditions but in this case the tasks were constructed from deterministic functions with specially designed velocity and acceleration profiles. Phase Plane performance analysis was conducted to study potential measures of workload or tracking difficulty

Radiation environment for rendezvous and docking with nuclear rockets

Radiation environment data for the NERVA engine are provided which may be utilized in estimating radiation exposures associated with various space maneuvers. Spatial distributions of neutron and gamma tissue kerma rates produced during full thrust operation of the engine are presented. Final rendezvous with an orbiting space station would be achieved subsequent to full thrust operation during a period of 10 or more hours duration in which impulse is delivered by the propellant used for removal of decay heat. Consequently, post operation radiation levels are of prime importance in estimating space station exposures. Maps of gamma kerma rates around the engine are provided for decay times of 4 and 24 hours after a representative firing. Typical decay curves illustrating the dependence of post operation kerma rates on decay time and operating history are included. Examples of the kerma distributions around the engine which result from integration over specific exposure periods are shown

Residual acceleration data on IML-1: Development of a data reduction and dissemination plan

The research performed consisted of three stages: (1) identification of sensitive IML-1 experiments and sensitivity ranges by order of magnitude estimates, numerical modeling, and investigator input; (2) research and development towards reduction, supplementation, and dissemination of residual acceleration data; and (3) implementation of the plan on existing acceleration databases

Internal Gravity Waves Modulate the Apparent Misalignment of Exoplanets around Hot Stars

We propose that the observed misalignment between extra-solar planets and their hot host stars can be explained by angular momentum transport within the host star. Observations have shown that this misalignment is preferentially around hot stars, which have convective cores and extended radiative envelopes. This situation is amenable to substantial angular momentum transport by internal gravity waves (IGW) generated at the convective-radiative interface. Here we present numerical simulations of this process and show that IGW can modulate the surface rotation of the star. With these two- dimensional simulations we show that IGW could explain the retrograde orbits observed in systems such as HAT-P-6 and HAT-P-7, however, extension to high obliquity objects will await future three- dimensional simulations. We note that these results also imply that individual massive stars should show temporal variations in their v sini measurements.Comment: 6 pages, 2 figures, Accepted for publication in ApJ

Analysis techniques for residual acceleration data

Various aspects of residual acceleration data are of interest to low-gravity experimenters. Maximum and mean values and various other statistics can be obtained from data as collected in the time domain. Additional information may be obtained through manipulation of the data. Fourier analysis is discussed as a means of obtaining information about dominant frequency components of a given data window. Transformation of data into different coordinate axes is useful in the analysis of experiments with different orientations and can be achieved by the use of a transformation matrix. Application of such analysis techniques to residual acceleration data provides additional information than what is provided in a time history and increases the effectiveness of post-flight analysis of low-gravity experiments

Marketing Percolation

A percolation model is presented, with computer simulations for illustrations, to show how the sales of a new product may penetrate the consumer market. We review the traditional approach in the marketing literature, which is based on differential or difference equations similar to the logistic equation (Bass 1969). This mean field approach is contrasted with the discrete percolation on a lattice, with simulations of "social percolation" (Solomon et al 2000) in two to five dimensions giving power laws instead of exponential growth, and strong fluctuations right at the percolation threshold.Comment: to appear in Physica

The moving boundary problem in the presence of a dipole magnetic field

An exact analytic solution is obtained for a uniformly expanding, neutral, infinitely conducting plasma sphere in an external dipole magnetic field. The electrodynamical aspects related to the radiation and transformation of energy were considered as well. The results obtained can be used in analyzing the recent experimental and simulation data.Comment: 17 pages, 1 figure, Submitted to J. Phys. A, Math. and Genera

Residual acceleration data on IML-1: Development of a data reduction and dissemination plan

A residual acceleration data analysis plan is developed that will allow principal investigators of low-gravity experiments to efficiently process their experimental results in conjunction with accelerometer data. The basic approach consisted of the following program of research: (1) identification of sensitive experiments and sensitivity ranges by order of magnitude estimates, numerical modelling, and investigator input; (2) research and development towards reduction, supplementation, and dissemination of residual acceleration data; and (3) implementation of the plan on existing acceleration data bases

Scraping the Social? Issues in live social research

What makes scraping methodologically interesting for social and cultural research? This paper seeks to contribute to debates about digital social research by exploring how a ‘medium-specific’ technique for online data capture may be rendered analytically productive for social research. As a device that is currently being imported into social research, scraping has the capacity to re-structure social research, and this in at least two ways. Firstly, as a technique that is not native to social research, scraping risks to introduce ‘alien’ methodological assumptions into social research (such as an pre-occupation with freshness). Secondly, to scrape is to risk importing into our inquiry categories that are prevalent in the social practices enabled by the media: scraping makes available already formatted data for social research. Scraped data, and online social data more generally, tend to come with ‘external’ analytics already built-in. This circumstance is often approached as a ‘problem’ with online data capture, but we propose it may be turned into virtue, insofar as data formats that have currency in the areas under scrutiny may serve as a source of social data themselves. Scraping, we propose, makes it possible to render traffic between the object and process of social research analytically productive. It enables a form of ‘real-time’ social research, in which the formats and life cycles of online data may lend structure to the analytic objects and findings of social research. By way of a conclusion, we demonstrate this point in an exercise of online issue profiling, and more particularly, by relying on Twitter to profile the issue of ‘austerity’. Here we distinguish between two forms of real-time research, those dedicated to monitoring live content (which terms are current?) and those concerned with analysing the liveliness of issues (which topics are happening?)

Path Integral Monte Carlo Simulation of the Low-Density Hydrogen Plasma

Restricted path integral Monte Carlo simulations are used to calculate the equilibrium properties of hydrogen in the density and temperature range of $9.83 \times 10^{-4}\rm \leq \rho \leq 0.153 \rm gcm^{-3}$ and $5000 \leq T \leq 250 000 \rm K$. We test the accuracy of the pair density matrix and analyze the dependence on the system size, on the time step of the path integral and on the type of nodal surface. We calculate the equation of state and compare with other models for hydrogen valid in this regime. Further, we characterize the state of hydrogen and describe the changes from a plasma to an atomic and molecular liquid by analyzing the pair correlation functions and estimating the number of atoms and molecules present.Comment: 12 pages, 21 figures, submitted for Phys. Rev.