Dynamical Systems Theory

The quest to ensure perfect dynamical properties and the control of different systems is currently the goal of numerous research all over the world. The aim of this book is to provide the reader with a selection of methods in the field of mathematical modeling, simulation, and control of different dynamical systems. The chapters in this book focus on recent developments and current perspectives in this important and interesting area of mechanical engineering. We hope that readers will be attracted by the topics covered in the content, which are aimed at increasing their academic knowledge with competences related to selected new mathematical theoretical approaches and original numerical tools related to a few problems in dynamical systems theory

Inertial MEMS: readout, test and application

This thesis moves towards the investigation of Micro Electro-Mechanical Systems (MEMS) intertial sensors from different perspectives and points of view: readout, test and application. Chapter 1 deals with the state-of-the-art for the interfaces usually employed for 3- axes micromachined gyroscopes. Several architecture based on multiplexing schemes in order to extremely simplify the analog front-end which can be based on a single charge amplifier are analysed and compared. A novel solution that experiments an innovative readout technique based on a special analog-Code Division Multiplexing Access (CDMA) is presented; this architecture can reach a considerable reduction of the Analog Front-End (AFE) with reference to other multiplexing schemes. Many family codes have been considered in order to find the best trade-off between performance and complexity. System-level simulations prove the effectiveness of this technique in processing all the required signals. A case study is also analysed: a comparison with the SD740 micro-machined integrated inertial module with tri-axial gyroscope by SensorDynamics AG is provided. MEMS accelerometers are widely used in the automotive and aeronautics fields and are becoming extremely popular in a wide range of consumer electronics products. The cost of testing is a major one within the manufacturing process, because MEMS accelerometer characterization requires a series of tests that include physical stimuli. The calibration and the functional testing are the most challenging and a wide selection of Automatic Test Equipments (ATEs) is available on the market for this purpose; those equipments provide a full characterization of the Device Under Test (DUT), from low-g to high-g levels, even over temperature. Chapter 2 presents a novel solution that experiments an innovative procedure to perform a characterization at medium-g levels. The presented approach can be applied to low-cost ATEs obtaining challenging results. The procedure is deeply investigated and an experimental setup is described. A case study is also analysed: some already trimmed Three Degrees of Freedom (3DoF)-Inertial Measurement Unit (IMU) modules (three-axes accelerometer integrated with a mixed signal ASIC), from SensorDynamics AG are tested with the experimental setup and analysed, for the first time, at medium-g levels. Standard preprocessing techniques for removing the ground response from vehicle- mounted Ground Penetrating Radar (GPR) data may fail when used on rough terrain. In Chapter 3, a Laser Imaging Detection and Ranging (LIDAR) system and a Global Positioning System (GPS)/IMU is integrated into a prototype system with the GPR and provided high-resolution measurements of the ground surface. Two modifications to preprocessing were proposed for mitigating the ground bounce based on the available LIDAR data. An experiment is carried out on a set of GPR/LIDAR data collected with the integrated prototype vehicle over lanes with artificially rough terrain, consisting of targets buried under or near mounds, ruts and potholes. A stabilization technique for multi-element vehicle-mounted GPR is also presented

COMET-AR User's Manual: COmputational MEchanics Testbed with Adaptive Refinement

The COMET-AR User's Manual provides a reference manual for the Computational Structural Mechanics Testbed with Adaptive Refinement (COMET-AR), a software system developed jointly by Lockheed Palo Alto Research Laboratory and NASA Langley Research Center under contract NAS1-18444. The COMET-AR system is an extended version of an earlier finite element based structural analysis system called COMET, also developed by Lockheed and NASA. The primary extensions are the adaptive mesh refinement capabilities and a new "object-like" database interface that makes COMET-AR easier to extend further. This User's Manual provides a detailed description of the user interface to COMET-AR from the viewpoint of a structural analyst

Mechanical activation and cation site disorder of spinel-based ceramics

This research focuses on the processing and the effects that has on the cation disorder of magnesium-aluminate spinel based (MgAl2O4) ceramics. The first goal of this project was to determine the effects of high-energy milling, i.e., mechanical activation, on cation disorder (inversion) within the spinel structure. First, 1:1 molar ratios of MgO:Al2O3 ceramics were processed using two green processing methods, ball milling (XD) and SPEX milling (mechanical activation, MA) followed by a subsequent annealing treatment in air to form a single spinel phase in each powder sample. Neutron diffraction analysis was employed to determine the cation site occupancy and revealed that overall mechanical activation resulted in a lower degree of cation site inversion compared to the non-activated materials, about 0.12 was the largest value returned for the MA materials and 0.13 was the lowest value out of the XD samples. The second portion of this project was to investigate the synthesis, densification behavior, and crystallographic site occupancy for a high-entropy spinel (HES) (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)Al2O4. This was compared to several other compositions including a MgAl2O4, NiAl2O4 and (Mg0.5Ni0.5)Al2O4 (MAS, NAS, NMAS) specimens produced using the same methods. Each composition reacted to form a single phase, but analysis of x-ray diffraction (XRD) patterns revealed that the HES specimen had a degree of inversion of 0.4. The NAS and NMAS samples were also highly inverted whereas the MAS material had minimal cation disorder. --Abstract, page iv

Feasibility studies of promising stability and gravity /including zero-G/ experiments for manned orbiting missions Final report, 17 Dec. 1964 - 17 Dec. 1965

Feasibility of stability and gravity experiments for manned orbiting mission

Surface modification and scan imaging of upconverting nanoparticles

The surface modification of upconverting nanoparticles was a main focus of this thesis and a wide variety of different functionalities were introduced on the nanoparticle surface in the process. The growth of a silica shell with a preferably simultaneous silanization proved to be a convenient way to create both a hydrophilic surface crucial for bioanalytical applications and an accessible functionality for subsequent modification. The utilization of silanol, amine, carboxyl, or phosphonate groups yielded UCNPs with strongly differing stabilities in dispersion and surface charges. A strong aggregation was observed for both an amine modification and the non-modified silanol groups of a pure silica shell with a tendency enhancement for a reduced shell thickness. Furthermore, surface phosphonate groups led to the formation of aggregates with high uniformity in both size and shape. In contrast, an optimized modification process to introduce carboxylic acids on the surface yielded monodisperse UCNPs with a diameter of 13 nm that are efficiently stabilized in aqueous dispersion. The presence of these predominantly single nanoparticles in high abundance was confirmed both by dynamic light scattering and transmission electron microscopy studies. This high monodispersity was also realizable by a ligand exchange utilizing the polymer polyacrylic acid. The method applied relied on a prior exchange of the hydrophobic oleic acid with BF4- ions allowing a subsequent modification with the polymer with simplified process conditions and reduced expenditure of time. Furthermore, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) was studied as a potential beneficial coupling reaction since it merged the advantages of the "Click chemistry" and "bioorthogonal reactions" concept. The associated alkyne and azide groups were bound to the nanoparticle surface by silanization of silica-coated UCNPs and the nanoparticles differed drastically in their dispersion stability. While an azide-functionalized surface exerted a certain degree of stabilization, alkyne functionalities led to a strong nanoparticle aggregation and precipitation in a very short time. However, both functional groups allowed an efficient and highly specific binding of their respective counterpart shown by an exemplary Click reaction with a fluorophore and also the important role of the copper(I) catalyst was demonstrated. The attachment of more complex molecules including biochemical functionalities or additionally stabilizing moieties revealed a good feasibility of a modification by the copper-catalyzed azide-alkyne cycloaddition. A simultaneous modification of the UCNPs with azide and carboxyl groups led to an enhanced nanoparticle stability compared to a pure azide functionalization. Studies about the creation of a biomimetic nanoparticle surface comprised the encapsulation of UCNPs by virus capsid leading to the formation of virus-like particles (VLPs). After the process feasibility was confirmed to both dissemble and reassemble the capsid of a brome mosaic virus (BMV), small nanoparticles with an optimized surface were utilized to act as an artificial nucleation grain for self-assembly. These modified UCNPs met the three requirements for encapsulation: a hydrophilic surface to be dispersible in aqueous systems, an absolute diameter below 16 nm to fit in the capsid cavity of the BMV, and a negative surface charge to initiate the self-assembly of the capsomers similar to the viral RNA. In addition to the options described, citric acid was investigated as a potential surface ligand. While silanol and phosphonate groups were inappropriate to induce any kind of self-assembly, a form of unspecific interaction of the viral proteins with carboxylic acids was found both for covalent and non-covalent methods. An exception was citric acid, since it was prone to an irreversible removal from the UCNP surface during the VLP preparation process. However, for all nanoparticles with a modified surface no clear evidence of encapsulation was found as confirmed by both TEM imaging and immunogold staining. The second research focus of this thesis was the development of a new imaging method of UCNPs. At first, different imaging parameters of the scan mode of a Hidex Plate Chameleon Multilabel Detection Platform with a 980 nm excitation source were studied and optimized for UCNPs of the type NaYF4: Yb3+, Er3+ or NaY4:Yb3+, Tm3+. A collecting time from 250 to 500 ms was sufficient to obtain an upconversion emission signal distinguishable from the background and to minimize laser-induced damages to the sample due to heating effects. Furthermore, both the overall emission of the UCNPs and the emission in a narrow wavelength domain were suitable as the detection signal for the image acquisition. The respective filter or filter combination additionally influenced the signal-to-noise ratio and thus the detection sensitivity. While the green emission of erbium-doped UCNPs was favorable in this regard, limitations of the detector sensitivity in the near infrared range hampered the utilization of the strong near infrared emission of thulium-doped UCNPs for scans with sensitive detection. The lateral resolution of the resulting scan images was reduced to 200 µm providing both a good resolution of luminescent structures and a good discrimination of signal and background. Since a lower scan point distance resulted in longer scan times without additional structural information, a lateral resolution of 200 µm was defined as the lower limit of the lateral resolution of the scan modus. Finally, a limit of detection of 1 ng was determined for both erbium- and thulium-doped UCNPs with high accuracy regardless of the emission utilized as the detection signal. The applicability of this optimized process to real samples was demonstrated for both electrophoresis gels and lateral flow assays. The imaging of these gels and assays showed a high accuracy and reproducibility and allowed a good discrimination of the UCNP signal from the background and an illustration of differences in the UCNP concentrations or sample materials. Furthermore, the downconversion emission of fluorescein doped in the silica shell of the UCNPs allowed a comparison between the imaging methods based either on up- and downconversion. In addition to a high conformity of the images regarding the position and intensity of the gel bands the absence of any signal from the fluorophore in the upconversion scan images of the gels confirmed a high discriminability of both signal types. This enables a bimodal readout. Moreover, the evaluation of the lateral flow assays yielded a limit of detection of the exemplary analyte "Schistosoma circulating anodic antigen (CAA)" of 44 or 64 pg/mL for the wet and dry condition of the array, respectively. For these measurements the the overall emission of the erbium-doped UCNPs was utilized as the detection signal. Consequently, a high sensitivity of this new imaging method was evident compared to other instrument options. Finally, the scan mode of the Chameleon reader was also utilized for studies about a potential enhancement of the upconversion emission by surface plasmon resonance of a gold surface. Both NaYF4: Yb3+, Er3+ or NaY4:Yb3+, Tm3+ were applied on a gold or silica surface of a commercial wafer with gold electrodes whose complete surfce was modified before with the same functionality to ensure the same chemical properties. The comparison of the emission intensities of UCNP on the different surface materials indicated a strong dependency of the enhancement effect on the emission wavelength. While the intensity of the green or near infrared emission of erbium- or thulium-doped UCNPs was increased by the gold surface, the overall emission of both UCNP types was reduced indicating a simultaneous quenching of the upconversion emission at other wavelengths

12th International Conference on Vibrations in Rotating Machinery

Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction

Helicopter Handling Qualities

Helicopters are used by the military and civilian communities for a variety of tasks and must be capable of operating in poor weather conditions and at night. Accompanying extended helicopter operations is a significant increase in pilot workload and a need for better handling qualities. An overview of the status and problems in the development and specification of helicopter handling-qualities criteria is presented. Topics for future research efforts by government and industry are highlighted

The 1982 NASA/ASEE Summer Faculty Fellowship Program

A NASA/ASEE Summer Faculty Fellowship Research Program was conducted to further the professional knowledge of qualified engineering and science faculty members, to stimulate an exchange of ideas between participants and NASA, to enrich and refresh the research and teaching activities of participants' institutions, and to contribute to the research objectives of the NASA Centers

Parameter estimation techniques and application in aircraft flight testing

Technical papers presented at the symposium by selected representatives from industry, universities, and various Air Force, Navy, and NASA installations are given. The topics covered include the newest developments in identification techniques, the most recent flight-test experience, and the projected potential for the near future