The highly flexible HALE (High Altitude Long Endurance) aircraft analysis methodology is of interest because early studies indicated that HALE aircraft might have different vibration and aeroelastic characteristics from those of conventional aircraft. Recently the computer code Nonlinear Aeroelastic Trim And Stability of HALE Aircraft (NATASHA) was developed and used to the flight dynamics and aeroelastic analysis of flying wing HALE aircraft. Further analysis improvements were required to extend its capability to the ground vibration test (GVT) environment and to both GVT and aeroelastic behavior of HALE aircraft with other configurations. First, the geometrically exact fully intrinsic beam theory was extended to treat other aircraft configurations modeled as an assembly of beam elements. It includes auxiliary elevator input in the horizontal tail and fuselage aerodynamics. Second, the methodology was extended to treat the GVT environment to provide modal characteristics for model validation. A newly developed bungee formulation is coupled to the intrinsic beam formulation for the GVT modeling. After the coupling procedures, the whole formulation cannot be fully intrinsic because the geometric constraint by bungee cords makes the system statically indeterminant. Third, because many HALE aircraft are propeller driven, the methodology was extended to include an engine/nacelle/propeller system using a two-degree-of-freedom model. This step was undertaken to predict a dynamic instability called ``whirl flutter," which can be exhibited in such HALE aircrafts. For simplicity, two fundamental assumptions are made: constant approximation on the propeller aerodynamics and the use of equivalent three-bladed counterpart for two-bladed propeller system to obviate the need for Floquet theory. The validity of these assumptions is verified by investigating the periodic effect of side forces and hub moments and the periodic inertia effect. Finally, parametric studies show how the current methodology can be utilized as a unified preliminary analysis tool for the vibration and aeroelastic analysis of highly flexible HALE aircraft.

No description available.

During aeroelastic simulation, forces and displacements must be interpolated between the non-matching fluid and structural meshes, while the volume fluid mesh must deform as the surface moves. Fluidstructure interpolation is necessary because numerical models for fluids and structures use different solvers, and at the interface these meshes do not match. The problem of mesh motion arises from the fact that the discretised fluid volume must conform to the motion of the surface, which means motion of the surface must be diffused into the volume.

Smart materials and structures systems are increasingly being developed to handle more complex problems. One of the main research schemes is the augmentation of the control authority of the smart actuators used in such systems. The augmentation can be obtained by constructing hybrid and multi- smart materials actuator systems and/or by the optimization of the location and orientation of those actuators. In the first part of this study, the alteration of the natural frequency of composite structures using Nitinol-based Shape Memory Alloy (SMA) wires will be presented using the analyses of strain energy perturbations on a plate. These governing strain equations were solved analytically and numerically to show the effect of point forces acting in a distributive manner and the subsequent effect it has on the plate's stiffness and hence it's natural frequency. In the second part of the thesis, a more complex loading condition is considered to investigate piezoceramic actuator control authority in relation to wing flutter control. The advancement in the application of active material induced-strain actuation such as piezoelectric materials in suppression of structural vibrations drew wide interest in its use for wing flutter control. Higher flutter speed and hence wider operating envelope was achieved by delaying the coalescence of the eigenvalues for plunge and twist modes. . This delay is obtained by adding more strain energy to the system as a result of the activation of the piezoelectric actuators. Most of the studies done were by controlling the plunge/bending motion, where the piezoelectric actuators are bonded longitudinally to produce bending moments. In this study, the control of the pitch/twisting motion was investigated and it showed better control of flutter by using simultaneous multi-actuations compared to single piezo actuations. It was shown that within the scope of the angular orientations of the piezoelectric patches investigated in this study, piezoelectric patches oriented about +150 from the beam's longitudinal ax is resulted in the most optimal piezo-configuration. This was corroborated by both the numerical flutter speed and actuator moment evaluations. In addition, the orientation of the piezoelectric patches was shown to significantly affect the pitch angle of the beam relative to each other. The damping ratio was also investigated and this showed greater instability for piezoelectric patches oriented at negative angles, thus further supporting the finding of the aforementioned optimal orientation of +150. These findings confirmed the dominance of the base (closest to the fixed portion of the beam) piezo when actuated with other piezos.

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 2002. / Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 61). Also available online.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2006. / Description based on contents viewed Jan. 26, 2007; title from title screen. Includes bibliographical references (p. 112-126).

Good performance is important for an application to run smoothly for the end user, but good tools and documentation are just as important for a developer in order tobe able to create good applications in the shortest amount of time.  This paper is comparing the cross-platform frameworks Flutter and Xamarin to find the respective strengths of the frameworks and which one is the better option and in what aspect, the newer Flutter or the well established Xamarin. We did this by studying related works to the topic as well as building applications in each framework with methods to test the performance of the applications, all the while trying out the tools and documentation of each framework. Our initial hypothes is was that Xamarin as a mature framework would perform better on average and it would also have more well developed tools. However we instead found Xamarin severely lacking compared to the newer Flutter framework and were at best equal or just slightly better. Flutter outperformed Xamarin in CPU performance, at times 3 times better than Xamarin, Flutter’s application size being almost half of the Xamarin application and the Flutter application load times were also faster. The tools were for most parts equal but the results of the documentations were split, with Xamarin having better component documentation with code examples for the components and Flutter having inconsistencies in documentation structure. However the Xamarin documentation was severely lacking in updated documentation and confusing instructions at places. The only things Xamarin performed better on were the number of lines in the codeas well as being marginally better performing at the RAM capacity test. The conclusion would be that Flutter is a well performing framework that continues to develop while Xamarin feels stagnant and most of its development seems to have slowed down over the last two years

The aim of the work is to create an application for a smart watch, which will allow you to measure races and trainings, or create localization data for this activity. The application is implemented for mobile devices with the Android and iOS operating systems. The Wear OS operating system is supported for smart watches. The thesis describes the theory of programming for mobile operating systems and programming for the operating system Wear OS. The practical part describes the design, implementation and testing. For the implementation of the mobile application as well as for the smart watch application I decided to choose Flutter framework and programming language Dart. The resulting application allow users to measure races and workouts.

The development of apps in a cross-platform framework is something that has been appearing more over the latest years. But the knowledge of knowing which of the two popular frameworks, React Native, and Flutter are most efficient when it comes to resource management and general comparisons are less known. This is what this thesis investigates. To find out the comparisons between React Native and Flutter we created two similar apps and document the process of creating an app with the selected frameworks. To get data on the differences when developing an app with these frameworks, we made a survey to get more experienced developers' input. We then did performance tests of the apps to be able to compare the results of the respective framework. The applications we built had several similar functionalities that we used to measure the performance. We also touched on the subject of comparison between a cross-platform framework and a native framework. To do this we performed a literature review on related work to conclude the approaches. From our result, we could conclude that the performance of the Flutter app had a slight advantage over the React Native app. But the difference was not that remarkable, and the overall development was fairly similar. There were some differences to the approaches of development when it came to less experienced developers compared to more experienced developers which we learn from our survey. More experienced developers tended to use external debugging tools, while less experienced used built-in tools such as console commands. Finally, we want to conclude that both Flutter and React Native has their pros and cons. Both frameworks have a big community which is growing everyday, but we believe that Flutter might overtake the popularity from React Native due to its slight performance superiority.From our literature review we can conclude that both approaches has their advantages and it depends a lot on the concept of the app. When developing a more complex app, the native approach is superior. When developing smaller apps with shorter life periods, cross-platform will faster get the app on the market.

A mobile application has to be able to keep up with heavy demands to compete with all the new applications that are developed each day. Good performance and nice visuals are base requirements for the development of mobile applications. There are many options for tools when developing and one of these choices is a native application, which is said to have better performance and suitability to the mobile environment. Another choice is a tool which requires only one code base for multiple platforms and is therefore easier to maintain. Flutter is an open-source User Interface (UI) toolkit created by Google that can create cross-platform applications with one code base while said to maintain the aspects of looking native. This paper explores how Flutter compares to native applications, which are currently seen as superior in mobile behaviour and performance. An experiment was conducted to test how Flutter as a cross-compiler compared to two native applications made of kotlin and Android studio and swift and XCode, in terms of CPU performance. A survey was created to see if there was a difference in the perception of users with regards to appearance and animations. A literature study was conducted to strengthen the results from the experiment and survey and to give a background to the subject. Flutter is a new tool and it continues to grow incredibly fast. Conclusions are drawn that a Flutter application can compete with a native application when it comes to CPU performance, but is not as developed in the animation area. Flutter does not require complex code for creating a simple application and uses significantly less lines of code in development compared to native. The final conclusion is that Flutter is best to use when building smaller to medium-sized applications, but has a potential to grow to overcome its current drawbacks in the animation department. Further examination of the areas examined in this paper is needed in order to ensure and strengthen the results.