Trident Scholar Abstracts 2004

Project LISA (Laser Interferometer Space Antenna) is a cooperative venture between the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) to put a laser interferometer into orbit around the sun for the sole purpose of measuring and studying gravitational waves.  The project has been under development for over a decade and is scheduled to launch in 2011.  LISA’s study of gravitational waves may help distinguish between several viable theories of gravity.  The pioneer of modern gravitational theory is Albert Einstein, whose general theory of Relativity (GR) describes gravitational interactions in terms of the geometry of a four-dimensional spacetime.  GR predicts the manner in which massive objects influence the curvature of spacetime and the way in which the curvature of spacetime influences the motion of massive objects.  A direct prediction of this theory is the formation of gravitational waves.  Gravitational waves can best be described as fluctuations, or ripples, in spacetime produced by accelerated masses.  Following Einstein’s publication of GR, several alternative theories of gravity have emerged. In general, these alternative theories can be approximated by GR.  However, they incorporate additional cosmological considerations and, as a result, predict different forms of gravitational waves. Specifically, these theories and GR disagree on whether gravitational waves are transverse or longitudinal, as well as the way a wave exerts stress on an encountered object.  Each gravitational wave will interact with the LISA experiment in its own way.  The projected sensitivity of LISA has been calculated for waves of the type predicted by GR; however, the sensitivity of the experiment has not been examined for alternative gravitational waves.  The primary purpose of this research will be to determine LISA’s sensitivity to alternative gravitational waves.

The goal of this project is to successfully design, build, and test a package for a microelectromechanical variable emissivity radiator to launch on the Naval Academy satellite, MIDSTAR I.  Microelectromechanical Systems (MEMS) are microchips with moving parts. Utilizing integrated circuit fabrication technology, these micro-scale devices offer the advantages of reduced mass, greater efficiency and bulk fabrication.

While much of MEMS research is focused on device design, there is a vital step required to link the laboratory with the real world that receives much less attention. MEMS packaging is equally important as the device it will support. Unlike integrated circuits, MEMS require protection from external elements but must also interact with the environment. This requirement makes packaging complex and difficult to standardize.

A research team at the Johns Hopkins Applied Physics Laboratory (JHU/APL) is currently designing and fabricating a MEMS-based thermal control device for satellites. The device has two layers: a thermally emissive outer layer and a layer in contact with the satellite. When a voltage is applied, the top layer contacts the bottom layer, allowing heat to radiate from the satellite.

Through research and laboratory testing, this research  will designing and fabricating the package for this device. Doing so will require extensive characterization of the first generation device alone, as well as testing of the device and package for expected levels of vibration, radiation, and temperature. This will ensure the device and package can survive space launch and orbit for the life of a satellite. The package is specifically being designed to allow testing on the next Naval Academy satellite, MIDSTAR I.  In addition to protecting the device, the package must also provide connections to the satellite’s onboard computer and power supply, and include sensors to verify operation.

This research work will provide valuable feedback to the APL research team, as the development of the package should reveal device design changes that will increase overall system performance. The research completed in this project will also become part of the foundation for future work in space packaging for MEMS, and aid future defense applications as the military continues to look toward space for the answers to modern communications and intelligence problems.

In this project, we will investigate the identification of new target structures necessary for the development of new treatment options in bacterial infections. One of those potential new target structures, the molecular chaperone linked protein ClpB, has demonstrated the ability to break apart protein aggregates resulting from heat shock or other stresses, and to disassemble protein complexes. ClpB is one member within the Clp family of chaperone proteins found in all prokaryotic and eukaryotic cells. There is also growing evidence that Clp proteins play an important role in the survival and virulence of pathogens during host infection. To date, there has been limited research into the function and regulation of ClpB in Staphylococcus aureus. The working hypothesis of this project is that the function of the ClpB protein in S. aureus resembles the documented function of ClpB in E. coli, and more generally that ClpB is a part of a broad response mechanism to disruptions in bacterial homeostasis. Therefore, this hypothesis will be tested by investigating the function and expression levels of ClpB in the adaptive responses of the bacteria to selective environmental stresses. Specifically, the clpB gene from S. aureus will be cloned and used to complement a growth defect in a deficient E. coli mutant to elucidate further the level of conservation of function in the Clp family of proteins in bacteria. In addition, the regulatory pathways controlling clp gene expression will be studied by monitoring expression levels induced by various stresses. The ClpB coding region of the S. aureus genome will be cloned and amplified using a polymerase chain reaction. The plasmid containing the ClpB deoxyribonucleic acid (DNA) will be inserted into the clpB mutant strain of E. coli. This mutant displays increased sensitivity to the ionic detergent sodium dodecyl sulfate (SDS). Protein expression will be monitored and growth curves will be performed in SDS. Stress conditions will be selected to determine the virulent and persistent characteristics of ClpB. Analysis of clpB ribonucleic acid (RNA) levels will reveal conditions other than temperature stress that induce expression. Identification of specific conditions that induce clpB expression is the first step in determining its possible role in the pathogenicity of S. aureus.

There is much untapped potential in the use of fiber optic technology. Its advantages, including greater bandwidth and higher data rates, are currently used most effectively in large-scale network backbones. While used to connect continents and cities, optical fiber still has yet to be widely integrated into small-scale applications, such as local area networks. The aim of this research project is to build a working eight-node optical fiber ring network that functions as a precursor to such a local area network. The network uses four wavelength division multiplexed (WDM) frequency channels and eight bidirectional add-drop multiplexers to route mixed types of data signals (digital and analog) between the individual nodes.

In WDM communications, information is transmitted on multiple optical frequencies. In this project, the specific frequencies are routed to different nodes in a bidirectional manner, minimizing the number of nodes a message must through in order to reach its destination. Eight add-drop multiplexers (ADM), one for each node, perform the routing function. The ADMs used in this network allow information on multiple wavelengths to propagate through them in both directions. Each ADM adds (drops) two wavelengths to (from) the ring network. The bidirectional capability is achieved using thin film filter technology, in which filtered wavelengths are reflected in a direction opposite that of the transmitted wavelengths.

The project is comprised of integrating each ADM into the network, addressing performance issues such as crosstalk between frequencies, bit error rates, signal to noise ratio, and reliability using different data formats. The practicality of the small-scale network is also examined, considering issues such as security and fault-tolerance.

Successful completion of the project will further harness the benefits of optical fiber. Ships, campuses, office buildings, even whole neighborhoods could be connected with the high bandwidth associated with fiber optic networks. If it can be shown that local area networks can operate at high data rates in a single fiber ring, while maintaining scalability and modularity, the possibility of installing smaller scale optical fiber networks would be significantly enhanced.

The last two years have seen an extraordinary growth of interest in photovoltaic (PV) cells made from organic conducting polymers. Such attention stems primarily from the prospect of using organic materials in manufacturing ultra thin, flexible devices. Polymeric photovoltaic cells also present a tantalizing possibility for producing coatings that function as sunlight-harvesting paints on roofs or even for developing fabrics to produce electricity from sunlight. The technical objectives for this project are the design, synthesis, and characterization of high conductivity, high optical transparency conducting polymers that incorporate light-harvesting and electron-transporting components.

Initially, methanol-EDOT will be synthesized via a seven-step process starting with thiodiglycolic acid. After synthesizing the EDOT monomer, it will be functionalized with a light-harvesting group. The EDOT derivative will then be spin-coated onto plastic and polymerized. Once the polymer systems are completed, their conductance and optical transparency will be studied. The novel conducting polymeric material with optimal conductance and optical transparency will be incorporated into a photovoltaic device.

This project constructs and estimates a model of product differentiation in the retail gas industry. Product differentiation can be horizontal, firms’ spatial location, or vertical, firms’ product quality choice. The theoretical literature finds that firms minimally differentiate to gain market share or maximally differentiate to reduce price competition, depending upon the assumptions. It also finds that firms maximally differentiate product quality; the high quality firm charges a higher price than the low quality firm because it incurs a higher cost of providing quality.

This research contributes to the product differentiation literature by empirically analyzing 230 retail gas stations in the Minneapolis-St. Paul market. Spatial differentiation is measured by locating the stations on a map, then determining which stations are neighbors, finally driving and time distances between a station and its neighbors are determined. Quality differentiation is measured using binary variables of extra amenities the station offers, such as pay at the pump, a car wash, a food mart or a service station.

After the initial estimation of the model, it will be tested for the existence of spatial autocorrelation and corrected for this problem. Spatial autocorrelation occurs when the disturbance terms in the data are related to the firms’ location and not randomly distributed. The corrected model will then more accurately estimate how the gasoline stations are making location, quality and price decisions in order to be profit maximizing. Finally, the actual market conditions will be compared to the socially optimal conditions for consumers. Socially optimal conditions will be estimated with simulation techniques.

The focus of this project is to study the material properties of electrospray deposited polymers for use as proton conducting membranes in fuel cells. The ultimate goal of the project is to provide critical insight into the behavior of the proton conductors so as to provide feedback for improving the next generation of fuel cells. The primary polymer in question will be an electrospray deposited Nafion, which has long stood as a benchmark material in proton conducting fuel cells. The properties that will be tested include conductivity as a function of water content, temperature, pressure and material swelling. If time permits, studies of mechanical properties will also be conducted. The results from this research will be shared with Hunter College, where Nuclear Magnetic Resonance (NMR) data will be taken on the materials, and Virginia Commonwealth University, where the polymers are chemically engineered.

This project is in keeping with the Office of Naval Research’s Grand Challenges for the 21^st Century, specifically, the development of new, safe, effective, and non-petroleum based sources of power and power generation. Hydrogen powered fuel cells are an area of focus for potential use as an energy storage mechanism in the future. At the heart of the fuel cell is a membrane electrode assembly (MEA) composed of two catalyst contacts sandwiching a proton exchange membrane. Electrospraying is a deposition process in which the material is passed through a charged syringe and accelerated towards a grounded drum, thus producing the layered MEA. The goal of this method of fabrication is to be able to quickly and inexpensively mass produce the MEA.

The goal of this project is to determine the maximum dynamic lift coefficient of high aspect ratio control surfaces to reduce uncertainty in design. The effective design of rudders, diving planes and other control surfaces with high aspect ratios, i.e. a larger depth in proportion to chord length, is hindered by uncertainty in the dynamic coefficient of lift of the body as it passes through a transient fluid flow affected by a free surface. High aspect ratio control surfaces are more efficient (higher lift-to-drag ratios) than traditional designs and generate greater lift at smaller angles to the incoming flow, however their increasing length produces significantly greater bending moments in the shaft. This has led to a number of in-service failures. As high aspect ratios become more commonplace on surface vessels and submarines, more precise knowledge of loading conditions is required to avoid more failures.

The dynamic lift coefficient is a dimensionless number applied to geometrically similar bodies that allows scaling lift and drag forces acting on bodies of different sizes, operating at different speeds, and in different fluid mediums. As the dynamic coefficient of lift is a dimensionless quantity, testing of large bodies such as ships hulls or wing sections can be successfully analyzed through the use of scale models.

Data collection will take place in the Naval Academy Hydromechanics Laboratory 380-ft towing tank. Two ¼-scale rudders will be tested on a donated 15-foot model. Strain gages will be attached to the rudder shaft to determine the strain distribution and overall deformation. A finite element model of the rudder will be used to correlate the measured strains to water pressures and the resulting average dynamic lift coefficient. These will be compared to computational fluid dynamics predictions of pressure plots for the same loading. Testing will include still water constant velocity, turning and response in waves.

The maximum value of dynamic lift coefficient will allow the designers of high aspect ratio control surfaces to better understand the nature of the loads on these bodies, allowing for more weight efficient and cost-effective designs.

The objective of this project is to study the optical properties of single mode waveguide systems that exhibit an absorption that increases with intensity of the light that is incident upon them. In this way these devices limit the transmission of optical energy and are referred to as “optical limiters”. Such systems are of great value to both the military and the telecommunications industry because of their ability to protect sensitive equipment from exposure to high intensity light. This work is being done in conjunction with researchers at the Naval Research Laboratory (NRL) where many of the materials under investigation are being developed.

Experiments will be performed using very small glass capillaries that are filled with materials that exhibit a nonlinear absorption, that is these materials absorb a greater amount of incoming light as the intensity of that light increases. These systems act as waveguides where light is confined to the small “core” region where the nonlinear material resides. Furthermore, only one intensity profile (or “mode”) is allowed if the index of refraction of the core is very close to that of the surrounding glass. In this case, the waveguide is called “single mode”. This situation will be realized by controlling the temperature of the waveguide since the index of refraction of the core materials that will be used in this study depend strongly on temperature. Lasers that emit pulses of light in visible and near infrared wavelengths will be coupled into the waveguides and input and output intensities will be measured.

After characterizing optical limiting in a single waveguide filled with a nonlinear material, a subsequent study will be pursued to analyze the optical properties of two such waveguides that are placed very close to one another. It is known that when light is coupled into one waveguide, a portion of its electric field will extend into the neighboring waveguide. This provides a pathway for energy to be coupled from one waveguide to the other. Optical limiting in a system of two coupled, nonlinear waveguides will be characterized.

Ever since engineers first realized that drag slowed ships down, they have been trying to predict and minimize its effects. The ability to accurately predict the drag forces on a ship before it even reaches the water would lead to more efficient designs. The goal of this project is to identify the appropriate roughness scaling parameters for simple three-dimensional roughness, and to determine the maximum roughness height where current boundary layer models are valid. In order to study and ultimately predict the effects of surface roughness on fluid flow and drag, flat plates with smooth and rough surface conditions will be tested. The first phase of testing involves towing the plates in a tow tank to determine the overall drag on the plate. These tests will be done in the 380-foot long tow tank located in the Naval Academy's Hydrodynamics Laboratory. A smooth plate will be used as a control surface. Three mesh surfaces along with three sandpaper surfaces will act as the rough surfaces to be tested. Mesh and sandpaper was chosen as the rough surfaces because they are three dimensional, which is characteristic of naturally occurring surfaces. Detailed velocity measurements will be obtained with the plates in a re-circulating water channel located in the Hydrodynamics Laboratory to determine the effect of the roughness on the turbulence near the surface, by measuring mean and turbulent velocities in the boundary layer. These detailed velocity measurements will be obtained with a laser Doppler velocimeter (LDV). Surface roughness will be quantified using a laser profilometer, a device that measures the topography of a surface. A model will then be created which correlates the quantified surface roughness with the associated drag caused by the sandpaper and mesh surfaces. In the future, the results from this project will aid in the development of a general model of overall frictional drag from physical measures of the surface alone. 

This project involves the evaluation of methods for robotic detection of underwater mines using swarms of cooperating unmanned underwater vehicles (UUVs). Underwater mines have always been a tough problem for Navy ships, as they are cheap, can be easily fielded and are capable of causing millions of dollars of damage. Hence, the Navy has become interested in the use of underwater robots to tackle the problem of detecting mines. The proposed technique is to seek mines using a large number of relatively cheap underwater robots working cooperatively to search and analyze the environment for mines. This type of system is referred to as a swarm, since the robots move around in coordination to perform a task collectively.

The objective of this research will be to evaluate existing swarm control methods for application to the problem of underwater mine countermeasures. Methods to be investigated include behavior-based, formation-based and statistical control techniques. Each candidate controller will be tested in a simplified, simulated environment to determine its suitability for this application. The best controller from each class will be further tested in a more accurate dynamic simulation of the environment. Analysis of the data collected will determine the best controller available, based on criteria such as time taken to search, number of obstacles avoided and number of targets found. If time permits, an attempt to evaluate the feasibility of a hybrid (combination) controller will be conducted.