1,112 research outputs found
An Analytic Model for left invertible Weighted Translation Semigroups
M. Embry and A. Lambert initiated the study of a semigroup of operators
indexed by a non-negative real number and termed it as weighted
translation semigroup. The operators are defined on by
using a weight function. The operator can be thought of as a continuous
analogue of a weighted shift operator. In this paper, we show that every left
invertible operator can be modeled as a multiplication by on a
reproducing kernel Hilbert space of vector-valued analytic functions
on a certain disc centered at the origin and the reproducing kernel associated
with is a diagonal operator. As it turns out that every hyperexpansive
weighted translation semigroup is left invertile, the model applies to these
semigroups. We also describe the spectral picture for the left invertible
weighted translation semigroup. In the process, we point out the similarities
and differences between a weighted shift operator and an operator Comment: 14 page
Navigation and flight director guidance for the NASA/FAA helicopter MLS curved approach flight test program
The navigation and flight director guidance systems implemented in the NASA/FAA helicopter microwave landing system (MLS) curved approach flight test program is described. Flight test were conducted at the U.S. Navy's Crows Landing facility, using the NASA Ames UH-lH helicopter equipped with the V/STOLAND avionics system. The purpose of these tests was to investigate the feasibility of flying complex, curved and descending approaches to a landing using MLS flight director guidance. A description of the navigation aids used, the avionics system, cockpit instrumentation and on-board navigation equipment used for the flight test is provided. Three generic reference flight paths were developed and flown during the test. They were as follows: U-Turn, S-turn and Straight-In flight profiles. These profiles and their geometries are described in detail. A 3-cue flight director was implemented on the helicopter. A description of the formulation and implementation of the flight director laws is also presented. Performance data and analysis is presented for one pilot conducting the flight director approaches
Investigation of image enhancement techniques for the development of a self-contained airborne radar navigation system
This study was devoted to an investigation of the feasibility of applying advanced image processing techniques to enhance radar image characteristics that are pertinent to the pilot's navigation and guidance task. Millimeter (95 GHz) wave radar images for the overwater (i.e., offshore oil rigs) and overland (Heliport) scenario were used as a data base. The purpose of the study was to determine the applicability of image enhancement and scene analysis algorithms to detect and improve target characteristics (i.e., manmade objects such as buildings, parking lots, cars, roads, helicopters, towers, landing pads, etc.) that would be helpful to the pilot in determining his own position/orientation with respect to the outside world and assist him in the navigation task. Results of this study show that significant improvements in the raw radar image may be obtained using two dimensional image processing algorithms. In the overwater case, it is possible to remove the ocean clutter by thresholding the image data, and furthermore to extract the target boundary as well as the tower and catwalk locations using noise cleaning (e.g., median filter) and edge detection (e.g., Sobel operator) algorithms
Sensitivity analysis of helicopter IMC decelerating steep approach and landing performance to navigation system parameters
Results of a study to investigate, by means of a computer simulation, the performance sensitivity of helicopter IMC DSAL operations as a function of navigation system parameters are presented. A mathematical model representing generically a navigation system is formulated. The scenario simulated consists of a straight in helicopter approach to landing along a 6 deg glideslope. The deceleration magnitude chosen is 03g. The navigation model parameters are varied and the statistics of the total system errors (TSE) computed. These statistics are used to determine the critical navigation system parameters that affect the performance of the closed-loop navigation, guidance and control system of a UH-1H helicopter
VTOL shipboard letdown guidance system analysis
Alternative letdown guidance strategies are examined for landing of a VTOL aircraft onboard a small aviation ship under adverse environmental conditions. Off line computer simulation of shipboard landing task is utilized for assessing the relative merits of the proposed guidance schemes. The touchdown performance of a nominal constant rate of descent (CROD) letdown strategy serves as a benchmark for ranking the performance of the alternative letdown schemes. Analysis of ship motion time histories indicates the existence of an alternating sequence of quiescent and rough motions called lulls and swells. A real time algorithms lull/swell classification based upon ship motion pattern features is developed. The classification algorithm is used to command a go/no go signal to indicate the initiation and termination of an acceptable landing window. Simulation results show that such a go/no go pattern based letdown guidance strategy improves touchdown performance
Political incumbency effects in India: a regional analysis
The significance of a study of political incumbency and the factors influencing it stems from the fact that it directly affects the behaviour of the incumbent political party and its accountability to the electorate. We use data on Parliamentary Elections in India from 1980 to 2014 to tease out evidence of incumbency advantage. We employ Regression Discontinuity Design (RDD) to estimate the incumbency effect. Our results indicate the absence of any incumbency effect when considering all elections in India together. This finding is at odds with the research reported so far. To explain our contrary result, we drilled down deeper to obtain a more granular view of the incumbency effect in India. We do this across various regions of India. The results show that north Indian states generally show strong evidence of incumbency disadvantage while south Indian states show strong evidence of incumbency advantage. We also show that incumbency advantage has increased over time
Research on new techniques for the analysis of manual control systems Progress report, 15 Dec. 1968 - 15 Jun. 1969
Decision processes of human manual controllers, neuromuscular system, and stochastic processe
A Survey on Classification of Photo Aesthetics Based on Emotion
Recognition of human facial expression and calculating exact emotion by computer vision is an interesting and challenging problem. Emotion in natural scenery images plays vital role in the way humans perceive an image. Based on the various emotions like happiness, sadness, fear, anger of any human being the images that are examined by that person can propose that if the person is in happy mood then he/she would C the same images in different ways but still can be possible to build a universal classification for various emotions. The paper proposes the various techniques of recognizing emotion on the basis of how humans perceive an image, also aims to classify the aesthetics of the photographic images and determine wallpaper (Scene or non-scene images) according to human emotions
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