1,720,972 research outputs found
Nonlinear dynamic aircraft simulation
Get PDFThe objective of this graduate project was to solve the non-linear differential equations which describe the motion of an aircraft. There are twelve equations in total which must be solved simultaneously, two of which are cross-coupled to each other. The problem was solved using numerical techniques. A computer program named SIXDOF was written in FORTRAN. The equations were solved simultaneously using a Runge-Kutta method. The cross-coupled equations were partially decoupled by the Author to allow use of the Runge-Kutta method. The results of the program show correct motions of the aircraft in all axes. The longitudinal motions show both the short period and phugoid modes. The lateraldirectional motions show both the dutch roll and spiral modes. The accuracy of the transient motions could not be verified against real flight test data. Comparisons of the results obtained were made against results from linearized theory. Agreement to within 15% was noted. Errors are most likely attributable to inaccurate equations for the estimation of the aerodynamic forces on the aircraft. Wind tunnel data should yield superior results.California State University, Northridge. Department of Engineering.Includes bibliographical references (leaf 32
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
An interactive flight control system simulation
Get PDFThe objective of this graduate project was to develop an interactive flight control system simulation that would allow the user to model a digital flight control system. An interactive FORTRAN computer program was written to run on a personal computer. The program was designed to be as user friendly as possible. A series of menus was developed to guide the user through the process of building a model and running a simulation. Algorithms were derived to model a digital flight control system. A z-transform Tustin transformation process was used to convert analog s-plane control system blocks into digital time discrete blocks. A nonlinear dynamic aircraft program was linked to the flight control program to provide a complete closed loop aircraft simulation. Results of this program were compared to known analytical results with virtually no differences between the two. In addition, a model was built to simulate an F-16 aircraft. A flight control system was designed to rapidly damp out the aircraft's response to a step input. The closed loop results were then compared to the open loop results. The digital flight control system successfully damped out all motions and provided aircraft stability. Whereas the open loop results had undamped motions and very weak stability.Includes bibliographical references (leaf 45)California State University, Northridge. Department of Engineering
Conceptual design of a short range cargo aircraft
Get PDFThe subject of this project is the preliminary conceptual design of a replacement aircraft for the Douglas DC-3. The aircraft was designed to be used in underdeveloped and third world countries. Therefore, the maintenance and cost of this aircraft was a prime concern in the original design. The aircraft was designed to have a payload capacity of 8500 lbs. and a range of 500 miles at maximum payload. The final configuration is a high wing twin engine turboprop aircraft with a cargo loading capability at the rear of the craft. The aircraft is powered by two Pratt and Whitney PW118 turboprop engines rated at 1892 eshp. The aircraft has a designed gross takeoff weight of 31500 lbs. and an empty weight of 17000 lbs. The results of this report could be used to decide if further design and/or production of the aircraft should be undertaken.Includes bibliographical references (page 47)California State University, Northridge. Department of Engineering
Global positioning system future national policy and management structure
Get PDFThe Global Positioning System (GPS) has become one of the most important tools for navigation in the world. Developed and maintained by the United States Armed Forces, this system can be used to obtain highly accurate position and velocity information virtually anywhere and at any time. Since its original conception in the early 1970s, there has been an inherent conflict of interest between the civilian use and military security of the system. This study focuses on the future of GPS as a civilian and military tool. Proposals to alter the management structure and to change national policy are reviewed and analyzed.California State University, Northridge. Department of Engineering.Includes bibliographical references (leaves 55-56
Aerodynamic panel program
Get PDFAn aerodynamic panel program was created for estimating stability derivatives of an aircraft. The three dimensional surfaces are represented by quadrilateral, two dimensional panels. Imposed on each of these panels is one of two basic aerodynamic flows, a vortex for representing lifting surfaces and a source for representing non-lifting surfaces. The vortex creates circulation about the panel, a basic tenet of lift, while the source models the effects of thickness on the displacement of a flow over a three dimensional surface. The effects of these flows on the uniform flow about the aircraft is estimated at each panel's control point. A set of simultaneous, linear equations are formed with the boundary condition of no flow through the surface of each panel imposed at the control point. Inviscid flow is assumed which inherently requires small angles-of-attack and yaw. The final results are stability derivatives relative to the body axes. The program is capable of generating panels automatically for ease of use or manually for accuracy.California State University, Northridge. Department of Engineering.Includes bibliographical references (leaf 37
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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