The effect of jet flow pulsing and blowing ratio on a jet in cross flow has been investigated. Preliminary jet flow studies were performed without cross flow and an extensive study of jet with cross flow was done for a total of nine test cases. The effect of velocities ratios of 0.85 and 3.4, as well as pulsing the jet flow at 20Hz, was investigated in the near and far field of the jet. A comparison between the jet in cross flow and an inclined cylinder in cross flow was also performed. Hot film measurements were taken within a grid of the flow field in the jet symmetry plane and out of the symmetry plane. Instantaneous velocities were generated at each location and mean velocity, RMS values, Reynolds stresses and mean vorticity were calculated and compared for each case. The higher velocity ratio case (VR=3.4) caused the jet flow to lift up from the wall penetrating into the cross flow compared to the lower velocity ratio case (VR=0.85) where the jet fluid remained attached to the wall and no lift off was observed. The higher velocity ratio case resulted in increased mean velocities, RMS values, Reynolds stresses and mean vorticity throughout the flow field compared to the low velocity ratio case. Secondary turbulent structures were discovered in the wake region of the inclined cylinder. Similar structures were absent in the downstream flow region during the jet in cross flow experiments. There was no significant effect on the jet trajectory as a result of jet pulsing. For both velocity ratio cases the jet trajectory remained similar to the steady cases. Jet pulsing increased the instantaneous velocity RMS levels and Reynolds stresses in the near field of the jet, but did not seem to affect the RMS levels and Reynolds stresses beyond x/d=4. Jet pulsing had a significant effect on the distribution of spectral energy. Distinct energy peaks are generated at the pulsing frequency and its harmonics. The distinct spectral peaks were largest close to the jet exit and within the jet flow, but were detectable throughout the entire flow field. / Graduation date: 2003

Graduation date: 2001

The goal of this thesis was to develop a process of producing small monodisperse alginate gel beads. The phenomenon of controlled jet break-up of alginate solution jet with assisted vibration was used to form uniform sodium alginate droplets which were subsequently crosslinked with divalent calcium ion to form gel beads. Producing uniform alginate beads below 500 microns has been a problem which previous researchers have faced. Also, there is no commercially viable system available which can produce microbeads of uniform size. This study was an attempt to solve some of these problems. Vibration was applied to the alginate solution jet in both axial and transverse direction to cause jet break-up. Also, different modes of transmitting the vibration to the jet, like vibrating the full assembly or vibrating a diaphragm, were investigated. This resulted in construction of different types of bead generator apparatus. The droplet formation involves the formation of a jet through an orifice and superposition of vibration in order to control the break-up the jet. Both of these fluid flow phenomena depend on the properties of the liquid used to form the droplets. Specifically, the viscoelastic properties of the liquid play a major role in determining the break-up dynamics of the jet. The rheology of the Keltone LV (alginate) solutions (1-2% w/v) was studied using a rotational Bohlin CS-50 Rheometer and a Clark High Shear Capillary Viscometer. The best results were obtained by using the axial vibrating diaphragm droplet generator. Good monodispersed beads (160-1000 microns) were produced by using two different size orifices 100 micron and 200 microns. The vibration frequency range used was 200-6000 Hz and the flowrate range was 2-7 ml/min. The alginate droplets were crosslinked in 0.1 M calcium chloride and the shrinkage of the alginate droplets due to gelation was studied over a period of 7 days. Based on our study a design for producing sub-100 micron size beads has been proposed which uses a piezoceramic crystal for producing high frequency vibrations. / Graduation date: 1997

Molecular dynamics is a technique in which the trajectories of a group of particles are calculated as a function of time by integrating the equations of motion. In this thesis we study the use of molecular dynamics for atoms in a crystal. A model is introduced which describes interactions of a physical system with an external heat reservoir in molecular dynamics simulations. This is accomplished by the addition of a "virtual variable" to the Hamiltonian which is used to scale time. Aspects of this model are discussed and examples are presented for a simple system. Similarly, a constant pressure model is introduced in which additional virtual volume variables are added to the Hamiltonian. The volume and shape of the molecular dynamics cell are now free to vary. Simple examples are discussed. Aspects of the computer programs and the algorithms are explained. Particular attention is focused on the methods used to integrate the equations of motion and to calculate the coulomb interactions. Examples of simulations using a zirconium oxide crystal are presented. We study the effects of heat bath and pressure bath simulations, both separately and in combination. Various features of the behavior are investigated with the primary focus on phase changes, numerical errors, and parameters describing the heat and pressure baths. / Graduation date: 1996

Living cells are dependent upon protein synthesis for virtually all cellular functions. The cellular machine responsible for protein synthesis, called the ribosome, is formed through the association of two unequally sized subunits, each composed of RNA and proteins. Proper assembly of each subunit is essential to ribosome function and therefore essential to the cellular life cycle. Previous studies focused on dissecting the assembly of the small ribosomal subunit (30S subunit) from E. coli have shown that 21 proteins sequentially assemble on the 16S rRNA at multiple nucleation sites. For the first time, we are able to monitor changes in the secondary and tertiary structure of the 16S rRNA upon the addition of single proteins during assembly by using time-dependent chemical probing. Results from these studies suggest that protein S17 induces multiple structural changes in 16S rRNA by first binding to helix 11 and then helix 7. S20 also induces changes in the rRNA by interacting with helix 9, 11, 44 and 13 in that order. These structural formations and rearrangements then prepare the binding sites for additional proteins (S12 and S16, respectively). This study demonstrates that time-dependent chemical probing is able to monitor the assembly of the 30S subunit at a level of detail never before seen. These studies also suggest that many motifs in the 16S rRNA structure are formed as a result of the proteins binding, lending evidence to the hypothesis that the function of ribosomal proteins is to shape and/or hold the RNA structure in place.

Quantifying the behavior of complex systems arguably presents the common ¡°hard¡±problem across the physical, biological, social, economic sciences. Individual-based or agent-based models have proved useful in a variety of different real world systems: from the physical, biological, medical domains through to social and even financial domains. There are many different models in each of these fields, each with their own particular assumptions, strengths and weaknesses for particular application areas. However, there is a lack of minimal model analysis in which both numerical and analytic results can be obtained, and hence allowing different application domains to be analyzed on a common footing. This thesis focuses on a few simple, yet highly non-trivial, minimal models of a population of interacting objects (so-called agents) featuring internal dynamical grouping. In addition to analyzing these models, I apply them to a number of distinct real world systems. Both the numerical and analytical results suggest that these simple models could be key factors in explaining the overall collective behavior and emergent properties in a wide range of real world complex systems. In particular, I study variants of a particular model (called the EZ model) in order to explain the attrition time in modern conflicts, and the evolution of contagion phenomena in such a dynamically evolving population. I also study and explain the empirical data obtained for online guilds and offline gangs, leading to a team-based model which captures the common quantitative features of the data. I then move on to develop a resource competition model (i.e. the so-called El Farol model) and apply it to the carbon emissions market, mapping the different market factors into model parameters which enable me to explore the potential market behaviors under a variety of scenarios.

The purpose for writing this thesis is to prove the automatic carrier landing system (ACLS) a valuable Operational Risk Management (ORM) tool for recovering F/A-18A-D aircraft aboard the modern aircraft carrier. ORM is itself a subset of human factors and worthy of exploration in the aviation systems field. In proving the value of the ACLS, the author presents the following objectives: 1) describe the major components of the F/A-18A-D and modern aircraft carrier ACLS, 2) describe the current Mode I approach procedures, and the Precision Approach Landing Systems (PALS) certification process, 3) promote an increase in automatic landings during night time and low ceiling/visibility environments through an analysis of ACLS strengths and weaknesses, and 4) advocate the continued use of fully automatic carrier landings amidst addressing deeply rooted fleet squadron paradigms and the advent of future technologies. The information gathered for this thesis came primarily from the author’s own direct flight and test experiences as well as documentation of standardized Navy flight and test publications. Detailed background information on the ACLS and future landing programs along with data from the Naval Safety Center and the VX-23 Carrier Suitability department were used as evidence to support the findings. The author concludes that the Mode I ACLS capability is extremely vital to the safe and expeditious recovery of the F/A-18A-D Hornet aircraft onboard the modern aircraft carrier that the Mode I automatic carrier landing system as currently structured and utilized is a highly effective risk management tool for naval aviation. The routine testing and certification of the precision approach equipment, all-weather capability, redundant cockpit data and voice safety network, plus enhanced aircraft carrier mobility through the use of Mode I approaches are all strengths of the ACLS system. To enhance the effectiveness of the ACLS for future carrier operations, the author recommends: 1) creating RAG and fleet squadron command climates that promote and support the use of Mode I approaches, 2) increasing ACLS training for aircrew and maintainers, and 3) establishing a new CV-1 approach that can capitalize on JPALS functionality in order to improve upon automatic landings.

A self-contained, portable, inertial and positional measurement system was developed and tested for an HGU-55 model fighter pilot helmet. The system, designated the Portable Helmet Instrumentation System (PHIS), demonstrated the recording of accelerations and rotational rates experienced by the human head in a flight environment. A compact, self-contained, “knee-board” sized computer recorded these accelerations and rotational rates during flight. The present research presents the results of a limited evaluation of this helmet-mounted instrumentation system flown in an Extra 300 fully aerobatic aircraft. The accuracy of the helmet-mounted, inertial head tracker system was compared to the aircraft-mounted referenced system. The ability of the Portable Helmet Instrumentation System to record position, orientation and inertial information in ground and flight conditions was evaluated. The capability of the Portable Helmet Instrumentation System to provide position, orientation and inertial information with sufficient fidelity was evaluated. The concepts demonstrated in this system are: 1) calibration of the inertial sensing element without external equipment 2) the use of differential inertial sensing equipment to remove the accelerations and rotational rates of a moving vehicle from the pilot’s head-tracking measurements 3) the determination of three-dimensional position and orientation from three corresponding points using a range sensor. The range sensor did not operate as planned. The helmet only managed to remain within the range sensor’s field of view for 37% of flight time. Vertical accelerations showed the greatest correlation when comparing helmet measurements to aircraft measurements. The PHIS operated well during level flight.

Naval aviation is on the brink of taking advantage of a 12 year old capability. Naval commercial derivative aircraft have had the ability to navigate in instrument meteorological conditions using global positioning technology for nearly as long as civil commercial-for-hire aircraft. However, tactical naval aircraft, like the E-2C Hawkeye, are now only beginning to obtain and install the necessary technology to meet federal aviation regulations for satellite based area navigation. Worldwide airspace controlling agencies have mandated the use of navigation equipment that meets highly specific performance standards prior to entry in required navigation performance airspace. Aircraft not compliant with these standards are denied flight clearance or experience clearance delays. The Department of Defense has issued policy guidance that allows military aviation organizations to self-certify satellite based navigation technologies to meet required navigation performance standards. In many ways, military navigation technologies far exceed the performance requirements for civil and international airspace use. These technologies, however, are highly specific in their mission orientation and must demonstrate their compatibility with civil aviation standards. This study focused on the source and the specifics of navigation performance requirements. Domestic and international regulations and policies were reviewed as they pertain to civil aviation, and then applied to military aviation. Critical technical standards documents were reviewed to determine the best strategy for complying with civil and international regulations. Lessons learned from previous E-2C navigation system evaluations were also reviewed and incorporated within this compliance strategy. Compliance and self-certification responsibilities belong to aircraft specific program managers within the Navy’s acquisition organization. Sophisticated navigation systems incorporating satellite positioning technology require a tailored approach toward compliance demonstration. Military receivers with precise positioning capability satisfy many of the required availability, accuracy and containment standards. To satisfy civil requirements, correctly keyed, military navigation systems may be evaluated according to standards typically applied to the most highly augmented standard civil systems. This thesis contains a comprehensive list of compliance items selected for their applicability to the E-2C Hawkeye mission.

The scientific objective of this study is to design an aircraft flight experiment that will provide airborne imaging data, augmenting satellite data, to advance the fundamental understanding of polar mesospheric clouds (PMCs). By capturing simultaneous top and bottom views of the PMCs, these airborne images will both provide insight into the time evolution of PMCs, and into the micro-features of these clouds, from which gravity waves and other details of the clouds vertical structures may be obtained. These data may help us better understand the driving mechanisms of these clouds and ultimately those elements of global climatic change, which are believed to cause their expanding presence. The proposed imager will use a similar charged-coupled device and interface as that of the Aeronomy of Ice in the Mesosphere’s (AIM’s) Cloud Imager and Particle Size (CIPS) imager and will observe the clouds in both the visible spectra and in a near-ultraviolet spectrum closer to the sensitivity of the CIPS imager. The sensor is to be integrated aboard UTSIs Piper Navajo. Algorithms for satellite intercept trajectories and airborne imager positioning are developed for flight campaigns, scheduled for the 2007 Boreal Summer along a series of airstrips in both Northern Quebec and Alaska.