Feasibility model of an advanced crossed-field amplifier for space communication systems

Feasibility model of cross field amplifier for use in amplitude or frequency modulation transmitter

Source of the optical red-slope in iron-rich meteorites

The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteorite science. S-type asteroids exhibit a positively red-sloped spectrum that is interpreted to indicate the presence of elemental iron on the surfaces. The characteristic red-sloped spectrum of iron-rich meteorites is produced by only the specular component of the reflectance. Complex metallic surfaces can be modeled as linear mixtures of specular and nonspecular components. It is the geometry of the metal on a surface and its interaction with surrounding material, rather than the absolute amount of metal, that determine the redness of resulting spectra. In order to distinguish between ordinary chondrite and differentiated parent bodies it is important to understand how regolith processes affect the nature and form of metal on asteroid surfaces

The effect of cave illumination on bats

Artificial light at night has large impacts on nocturnal wildlife such as bats, yet its effect varies with wavelength of light, context, and across species involved. Here, we studied in two experiments how wild bats of cave-roosting species (Rhinolophus mehelyi, R. euryale, Myotis capaccinii and Miniopterus schreibersii) respond to LED lights of different colours. In dual choice experiments, we measured the acoustic activity of bats in response to neutral-white, red or amber LED at a cave entrance and in a flight room – mimicking a cave interior. In the flight room, M. capaccinii and M. schreibersii preferred red to white light, but showed no preference for red over amber, or amber over white light. In the cave entrance experiment, all light colours reduced the activity of all emerging species, yet red LED had the least negative effect. Rhinolophus species reacted most strongly, matching their refusal to fly at all under any light treatment in the flight room. We conclude that the placement and light colour of LED light should be considered carefully in lighting concepts for caves both in the interior and at the entrance. In a cave interior, red LED light could be chosen – if needed at all – for careful temporary illumination of areas, yet areas important for bats should be avoided based on the precautionary principle. At cave entrances, the high sensitivity of most bat species, particularly of Rhinolophus spp., towards light sources almost irrespective of colour, calls for utmost caution when illuminating cave entrances

Eastern Airlines: The Rise and Fall of The Wings of Man

This paper examines the rise and fall of Eastern Airlines from 1928 to 1991. lt outlines the carrier\u27s development under a succession of leaders and discusses the major events of each leader\u27s reign. From a small contract mail carrier known as Pitcairn Aviation, Eastern grew to become one of the largest airlines in the free world. But after 26 years of growth and prosperity under the leadership of Eddie Rickenbacker, the airline began to stumble in the early 1960s. Frank Lorenzo took the reins in 1986 and began selling the carrier\u27s assets while attempting to destroy the unions. After a massive employee strike in 1989 and a bout with bankruptcy, Eastern stopped flying in January 1991

Effects of crop acreage control features of AAA on feed production in 11 Midwest states

This bulletin is the product of studies in the appraisal of governmental agricultural programs in progress at Iowa State College. The statistics upon which most of the conclusions relative to the effect of the AAA upon the production of feedstuffs are based are the estimates of feed production in the 3-year period, 1938-40, without crop acreage control. The manner in which the various estimates have been derived is explained in some detail in a series of fairly elaborate footnotes appended to tables 5 to 15, inclusive. The basic assumptions underlying these estimates are given in these footnotes. Available, relevant, empirical data are considered, and the appraisal and criticism of other research workers are taken into account.2 The quantification of these assumptions into estimates of feed production without crop acreage control are in the last analysis those of the authors, and, as all estimates, are subject to error. They are, it is believed, the best approximation that it is possible to make with the evidence now available of what the feed production would have been in the various parts of the Midwest had there been no AAA

Three-Dimensionally Confined Optical Modes in Quantum Well Microtube Ring Resonators

We report on microtube ring resonators with quantum wells embedded as an optically active material. Optical modes are observed over a broad energy range. Their properties strongly depend on the exact geometry of the microtube along its axis. In particular we observe (i) preferential emission of light on the inside edge of the microtube and (ii) confinement of light also in direction of the tube axis by an axially varying geometry which is explained in an expanded waveguide model.Comment: 5 pages, 4 figure

RECOGNITION AND ESTIMATION OF HUMAN LOCOMOTION WITH HIDDEN MARKOV MODELS

INTRODUCTION: The Collaborative Research Centre “Humanoid Robots” situated at the University of Karlsruhe is aimed to construct a learning and cooperating service robot. To cope with its tasks it is necessary that the robot is able to identify diverse objects as well as different persons. Looking at stochastic models for pattern recognition Hidden Markov Models (HMMs) are described to be most suitable to classify time arranged data (Bilmes 2002). The objective of this study is to screen if the HMMs supply satisfying rates of recognition of human trajectory and angle data. METHOD: Kinematic data of eight men and three women was captured at different walking and running speed (1.2 m/s, 3 m/s, 4 m/s, 5 m/s) on a treadmill. Data acquisition was realised with an infrared camera system with a frequency of 250Hz. For each walking/running speed there were 120 gait cycles of every test person available. The construction and training of the stochastic model was based on the gait data. Due to the fixed sequence of gait phases a HMM with a simple linear topology was chosen. Each state of the HMM represented a phase of the gait cycle. The different states were equipped with Gaussian distributions and transition probabilities to model the run of the angles observed. The HMM modelling human gait best was selected and trained with data of 17 double gait cycles for each data sequence of every test person. RESULTS: The trained HMMs showed recognition rates from 63% to 100% for the observed data sequences for five male test persons. Highest rates could be obtained with Centre of Mass and head angles. For some test person recognition rates decreased with data of gait cycles that were captured towards the end of one run. DISCUSSION: The high recognition rates based on kinematic data of Centre of Mass were expected due to the different mean values of the test persons according to their body height. The decrease of recognition rates that could be observed at some of the test person on late data of one run seems to be caused by acclimatisation to treadmill running. The achieved recognition rates exceed rates typical for speech recognition (Rabiner 1989). A combination of different angle data seems to promise increasing recognition rates. CONCLUSION: The study showed that HMMs seem to be suitable to identify humans based on their kinematic gait data satisfyingly stable. According to dislocation of the Gaussian distributions it could be possible to suggest on systematic changes on patterns over changes in walking-/running speed. REFERENCES: Bilmes, J. (2002). What HMMs Can Do. UWEE Technical Report, No UWEETR-2002-2003, University of Washington, Dept. of EE. Rabiner, L. R. (1989). A Tutorial on Hidden Markov Models and Selected Applications in Speech Recognition. Proceedings of the IEEE, 77 (2), 257-286 Acknowledgement V. Wank, Institute of Sport Science, University of Tübingen German Research Foundation – CRC 588 Humanoid Robot