Effects of an aft facing step on the surface of a laminar flow glider wing

A motor glider was used to perform a flight test study on the effects of aft facing steps in a laminar boundary layer. This study focuses on two dimensional aft facing steps oriented spanwise to the flow. The size and location of the aft facing steps were varied in order to determine the critical size that will force premature transition. Transition over a step was found to be primarily a function of Reynolds number based on step height. Both of the step height Reynolds numbers for premature and full transition were determined. A hot film anemometry system was used to detect transition

Comparison of theoretical and flight-measured local flow aerodynamics for a low-aspect-ratio fin

Flight test and theoretical aerodynamic data were obtained for a flight test fixture mounted on the underside of an F-104G aircraft. The theoretical data were generated using two codes: a two-dimensional transonic code called code H, and a three-dimensional subsonic and supersonic code called wing-body. Pressure distributions generated by the codes for the flight test fixture, as well as compared with the flight-measured data. The two-dimensional code pressure distributions compared well except at the minimum pressure point and the trailing edge. Shock locations compared well except at high transonic speeds. However, the two-dimensional code did not adequately predict the displacement thickness of the flight test fixture. The three-dimensional code pressure distributions compared well except at the trailing edge of the flight test fixture

A water tunnel flow visualization study of the vortex flow structures on the F/A-18 aircraft

The vortex flow structures occurring on the F/A-18 aircraft at high angles of attack were studied. A water tunnel was used to gather flow visualization data on the forebody vortex and the wing leading edge extension vortex. The longitudinal location of breakdown of the leading edge vortex was found to be consistently dependent on the angle of attack. Other parameters such as Reynolds number, model scale, and model fidelity had little influence on the overall behavior of the flow structures studied. The lateral location of the forebody vortex system was greatly influenced by changes in the angle of sideslip. Strong interactions can occur between the leading edge extension vortex and the forebody vortex. Close attention was paid to vortex induced flows on various airframe components of the F/A-18. Reynolds number and angle of attack greatly affected the swirling intensity, and therefore the strength of the studied vortices. Water tunnel results on the F/A-18 correlated well with those obtained in similar studies at both full and sub scale levels. The water tunnel can provide, under certain conditions, good simulations of realistic flows in full scale configurations

Aerodynamic analysis of hypersonic waverider aircraft

The purpose of this study is to validate two existing codes used by the Systems Analysis Branch at NASA ARC, and to modify the codes so they can be used to generate and analyze waverider aircraft at on-design and off-design conditions. To generate waverider configurations and perform the on-design analysis, the appropriately named Waverider code is used. The Waverider code is based on the Taylor-Maccoll equations. Validation is accomplished via a comparison with previously published results. The Waverider code is modified to incorporate a fairing to close off the base area of the waverider configuration. This creates a more realistic waverider. The Hypersonic Aircraft Vehicle Optimization Code (HAVOC) is used to perform the off-design analysis of waverider configurations generated by the Waverider code. Various approximate analysis methods are used by HAVOC to predict the aerodynamic characteristics, which are validated via a comparison with experimental results from a hypersonic test model

A study of transonic aerodynamic analysis methods for use with a hypersonic aircraft synthesis code

A means of performing routine transonic lift, drag, and moment analyses on hypersonic all-body and wing-body configurations were studied. The analysis method is to be used in conjunction with the Hypersonic Vehicle Optimization Code (HAVOC). A review of existing techniques is presented, after which three methods, chosen to represent a spectrum of capabilities, are tested and the results are compared with experimental data. The three methods consist of a wave drag code, a full potential code, and a Navier-Stokes code. The wave drag code, representing the empirical approach, has very fast CPU times, but very limited and sporadic results. The full potential code provides results which compare favorably to the wind tunnel data, but with a dramatic increase in computational time. Even more extreme is the Navier-Stokes code, which provides the most favorable and complete results, but with a very large turnaround time. The full potential code, TRANAIR, is used for additional analyses, because of the superior results it can provide over empirical and semi-empirical methods, and because of its automated grid generation. TRANAIR analyses include an all body hypersonic cruise configuration and an oblique flying wing supersonic transport

A computer module used to calculate the horizontal control surface size of a conceptual aircraft design

The creation of a computer module used to calculate the size of the horizontal control surfaces of a conceptual aircraft design is discussed. The control surface size is determined by first calculating the size needed to rotate the aircraft during takeoff, and, second, by determining if the calculated size is large enough to maintain stability of the aircraft throughout any specified mission. The tail size needed to rotate during takeoff is calculated from a summation of forces about the main landing gear of the aircraft. The stability of the aircraft is determined from a summation of forces about the center of gravity during different phases of the aircraft's flight. Included in the horizontal control surface analysis are: downwash effects on an aft tail, upwash effects on a forward canard, and effects due to flight in close proximity to the ground. Comparisons of production aircraft with numerical models show good accuracy for control surface sizing. A modified canard design verified the accuracy of the module for canard configurations. Added to this stability and control module is a subroutine that determines one of the three design variables, for a stable vectored thrust aircraft. These include forward thrust nozzle position, aft thrust nozzle angle, and forward thrust split

Turkey: Another $1 Trillion Emerging Economy?

The strategic location of Turkey makes it a very important country in terms of geopolitics as well as economics. Turkey is located at the crossroads of Europe, Asia, the Caucasus, and the Middle East. It is where East meets West without clashing with each other but merging with each other. Even though, industry, trade, and finance are all dominated by the expansive and crowded Istanbul, other cities and towns in Anatolia –the Anatolian Tigers- are industrializing rapidly and now participating in the global economy. Today, Turkey has the largest economy in the greater Middle East. Depending of the source, Turkey already entered or is about to enter the club of $1 trillion economies. According to CIA World Factbook estimates for 2009, Turkey is a newly industrialized country (NIC) and the 17th largest economy in the world with a GDP-PPP of$903.9 billion in 2008. On the other hand, the World Bank ranks the Turkish economy as the 15th largest economy in the world with a GDP-PPP of $1.028 trillion in 2008. The dynamic Turkish private sector and its new generation young entrepreneurs are replacing the public sector in every segment of the economy. The role of the state and the central government in the economy has been declining since the early 1980s. Especially, the international trade area has been a success story in the process of integrating Turkey to the global economy. Between 2000-2007 total trade volume rose by 19.2$81 billion to $277 billion. Today, more than 94% of Turkish exports are manufactured goods with auto and auto related products leading the exports. One thing that really differentiates Turkey from the rest of the Middle East is that even though Turkey’s population is 99.9% Muslim, it is a secular representative parliamentary democracy. Establishing a viable democracy and democratic life has been a long battle in the Ottoman Empire as well as in the Republican Turkey. Against all odds and after 15 economic crises and 3 military coups in 85 years, the Turkish experience teaches us that democracy, free-markets, and open society are all very possible in a predominantly Muslim country. So far, Turkey has been the only country in the greater Middle East which successfully fused modernity, democracy, industrialization, and Islam into a viable system

What drives consumers to patronise a hedonic social network? an empirical test of consumers' experiences, and their impact on continuance intention

My doctoral research focuses on the analysis of the various factors that potentially contribute to loyalty towards hedonic social networks. Among all the social networks, our study focuses on Facebook. After reviewing the relevant literature, we built a model including factors in three different categories: user experience (flow, interactivity and presence), social influence (subjective norms) and users' personality (OSL and attitude). With all the forgoing factors, we built a model containing the relationships between the constructs proposed, and its role in the construction of loyalty. The model has been validated and empirically analysed with a field research. For that purpose, we took a 371 valid records sample. The model was analysed using structural equation modelling (SEM). The empirical study yielded a positive relationship between the following constructs: interactivity with social and spatial presence, flow, attitude and loyalty; spatial presence with flow and social presence; social presence with loyalty; flow with attitude; subjective norms with loyalty; and attitude with loyalty.Esta tesis doctoral se enfoca en identificar y analizar los factores que puedan contribuir a la formación de lealtad hacia el uso de las redes sociales hedónicas. Entre todas las redes sociales, nuestro estudio se ha enfocado en Facebook. Después de revisar la literatura relevante, construimos un modelo que incluía factores relacionados de tres categorías distintas: la experiencia de uso (flujo, presencia e interactividad), la influencia social (normas subjetivas) y la personalidad del usuario (actitud y OSL). Con todo ello hemos construido un modelo que recoge las relaciones entre los constructos propuestos, y su papel dentro de la construcción de la lealtad. El modelo ha sido validado y contrastado empíricamente con una investigación de campo. Para ello se ha tomado una muestra de 371 registros. El modelo fue analizado utilizando una metodología de modelado de ecuaciones estructurales (SEM). El estudio empírico arrojó una influencia positiva entre los siguientes constructos: interactividad con presencia social y espacial, con flujo, actitud y lealtad; presencia espacial con flujo y presencia espacial; presencia social con lealtad; flujo con actitud; normas subjetivas con lealtad; y actitud con lealtad.Aquesta tesi doctoral s'enfoca en identificar i analitzar els factors que puguin contribuir a la formació de lleialtat cap a l'ús de les xarxes socials hedòniques. Entre totes les xarxes socials hedòniques, el nostre estudi s'ha enfocat a Facebook. Després de revisar la literatura rellevant, vam construir un model que incloïa factors relacionats de tres categories diferents: l'experiència d'ús (flux, interactivitat i presència), la influència social (normes subjectives) i la personalitat de l'usuari (actitud y OSL). Amb tot això hem construït un model que recull les relacions entre els constructes proposats, i el seu paper dins de la construcció de la lleialtat. El model ha estat validat i contrastat empíricament amb una investigació de camp. Per això s'ha obtingut una mostra de 371 registres. El model va ser analitzat utilitzant una metodologia de modelatge d'equacions estructurals (SEM). Aquest contrast va permetre mostrar una influència positiva entre els següents constructes: interactivitat amb presència social i espacial, amb flux, actitud i lleialtat; presència espacial amb flux i presència espacial; presència social amb lleialtat; flux amb actitud; normes subjectives amb lleialtat; i actitud amb lleialtat.Societat de la informació i el coneixemen

The Lower Reaches of Long Creek, Kentucky: A Karst Anomaly in Allen County

A field study of the lower reaches of the Long Creek drainage area in southeastern Allen County, Kentucky, established the karst character of that area. The area heretofore had been described as a non-karst area. Four swallow holes, which individually or collectively totally pirate Long Creek, were identified. Two major resurgences of the pirated flow were located and described. A detailed study of a portion of the Long Creek drainage area revealed thirty-four springs, all of which were pirated at least once, and no flow from these springs reached Long Creek by surficial routes. The field survey also revealed dolines and a major cavern, Carpenter’s Cave. The geologic formation responsible for the karst features within the Long Creek drainage area is the Louisville limestone of Silurian age. These strata are characteristically karstic wherever exposed. The impermeability of the Chattanooga shale which overlies the Louisville limestone was established by the analysis of spring piracy and resurgence. The phreatic character of the Carpenter’s Cave and other karst features led to the conclusion that these karst features were developed prior to the deposition of the impermeable Chattanooga shale during Devonian time

Principles of Macroeconomics (Online)

This course is an introduction to the formal study of macroeconomics. Macroeconomics involves the study of the economy as a whole. Topics that are covered include national income determination, the general price level, interest rates, unemployment, and fiscal and monetary policies