• Robust optimization of NURBs metamodels for engineering design

      Steuben, John C.; Turner, Cameron J.
      Engineering design is generally characterized as an activity where a designer compares alternative solutions to an engineering challenge in order to meet some required level of performance. Almost invariably this involves the selection of values for design variables such that the design meets performance requirements. Unfortunately, in many modern engineered products and systems the number of these design variables exceeds what an engineer may comfortably contemplate using traditional tools. Optimization tools which allow engineers to quantify and maximize performance in high-dimensional design spaces will become increasingly indispensable to the engineer if they can perform two tasks. These tools obviously must be able to search the design space for design variable values that maximize performance. Simultaneously, they must locate and quantify designs that provide robustness, or insensitivity in performance with respect to uncertainty or variation in design parameters. The considerations of modern manufacturing and control systems force this second requirement, as no machine component can be produced without variation, nor can any system be controlled with arbitrary accuracy. When optimizing a design, a common difficulty is encountered. Many, if not most, engineering challenges are represented by system models of great complexity. Adequate analysis and optimization of the model is subsequently impossible due to time and computation limitations. As a result, surrogate models termed "metamodels" are used in place of the actual system model. These metamodels are far more computationally efficient and allow the optimization of otherwise intractable problems. Non-Uniform Rational B-Splines (NURBs) have emerged as a powerful metamodeling technique capable of addressing the twin challenges posed above. Previous research has resulted in the development of algorithms capable of fitting NURBs metamodels to design spaces of many input variables and performance indicies, and performing various discreet optimizations upon these metamodels. In the present research we expand upon this basis by illustrating the development of robust optimization algorithms that leverages the unique properties of NURBs metamodels. This optimization is conducted in a general fashion by considering both optimality and various robustness metrics as global or local model properties, and illustrates the tradeoffs between them using a novel graphical approach.
    • Microstructure-mechanical property relationships for Ni-Ti-Pt high temperature shape memory alloys

      Hudish, Grant; Kaufman, Michael J.; Diercks, David R.; Garg, A.; Noebe, R. D.
      Within the past decade, NASA has been developing high temperature shape memory alloys (HTSMAs) for use as simple, robust, and lightweight solid-state actuators. Shape memory alloys (SMAs) as actuators are considered nonconventional and advanced actuation devices and are capable of providing a power to weight ratio greater than that of DC motors, pneumatic systems, and comparable to that of hydraulic systems, in a much more compact and simplified geometry. Alloys of Ni and Ti in equal amounts are the commercially prevalent SMAs, but are limited to uses near room temperature. Increasing the transformation temperature of traditional SMAs would allow for their use in various industries including aerospace, automotive, and down hole energy exploration, to name a few. Alloying additions of Pd, Pt, Au, Hf and Zr all increase the transformation temperatures of Ni-Ti alloys and at least potentially allow for their use in higher temperature applications. Pt is currently one of the most promising ternary additions for stable and predictable SMAs for use at high temperatures, but little is understood about the effects of Pt on the microstructure and mechanical properties of Ni-Ti alloys. The current research explores the link between alloy microstructures and the mechanical properties of several Ni-Ti-Pt alloys and the subsequent effects these relationships have on the overall performance of Ni-Ti-Pt HTSMAs as solid state actuators.
    • Transformation of the U.S.-ROK alliance: balancing American strategic flexibility and South Korean modernization, The

      Davis, Elizabeth Van Wie; Cerella, Anthony F.
      Even though the bilateral security alliance between South Korea and the United States is a product of Cold War it remains strategically significant for Korean and Northeast Asian stability. The alliance is currently changing as both the United States and South Korea are modifying their military strategies and structures. The United States is currently transforming its defense structure centering on the idea of strategic flexibility. Strategic flexibility involves reexamining and reallocating global force structures to best combat a host of non-traditional threats. American transformation is changing the mission and scope of United States Forces Korea (USFK); considered the linchpin of the U.S.-ROK (Republic of Korea) alliance. Concurrently South Korea is assuming more responsibility for its defense and is instituting a detailed defense modernization plan known as the Defense Reform Plan 2020 (DRP). The simultaneous implementation of both plans will influence regional stability and test the long-term viability of the U.S.-ROK alliance. Simultaneous transformation will alter the alliance however, neither transformation plan calls for the elimination of the alliance. Joint synchronization of American and South Korean transformation plans; continued coordination and communication are the best policies to maintain the alliance. In sum this long-standing Cold War alliance remains valuable for the United States and Northeast Asia as it continues to promote regional security and stability.
    • Quasiparticle spectrum of 2-D Dirac vortices in optical lattices

      Haddad, Laith H.; Carr, Lincoln D.
      Bose-Einstein condensates (BEC's) in a honeycomb optical lattice are described by a nonlinear Dirac equaton (NLDE) in the long wavelength, mean field limit [1]. The bipartite structure of the lattice appears as pseudospin in the multi-component BEC with states above and below the Dirac point playing the roles of particles and antiparticles. Although much work has been done on NLDE's, the bulk of the literature deals with models with Poincare invariant nonlinearites. In contrast our equations break Poincare symmetry providing an opportunity to study phenomenological models in cosmology and particle physics where this symmetry is not manifest. We present the associated linear stability equations and apply them to the case of weak contact interactions to obtain the quasiparticle energies, states, and stabilities of vortex solutions of the mean field equations. We discuss future applications of our results to problems at the interface between condensed matter and particle physics. [1] L. H. Haddad and L. D. Carr, "The Nonlinear Dirac Equation in Bose-Einstein Condensates: Foundation and Symmetries," Physica D: Nonlinear Phenomena, v. 238, p. 1413 (2009) . http://arxiv.org/pdf/0803.3039v1.
    • Quantum many-body tunneling of Bose-Einstein condensates

      Glick, Joseph; Carr, Lincoln D.
      Consider the tunneling of a many-body wavefunction through a potential barrier. Specifically we examine quantum many-body tunneling of ultracold bosons in one dimensional optical lattice potentials. Such systems are described by the Bose-Hubbard model, and serve as an ideal testbed for the observation of quantum phenomena on macroscopic length scales. Bright solitons, self-sustaining nonlinear waves, are confined by a thin potential barrier. By decreasing the size of the barrier or by tuning the nonlinearity, we find that the bound states can be transformed into quasi-bound ones as the soliton tunnels collectively out of confinement. The lowly entangled 1D many-body problem can be numerically solved via time-evolving block decimation: a time-adaptive density matrix renormalization group routine. As a sanity check the results can be compared to mean-field theory predictions obtained from numerical analysis of the Nonlinear Schrodinger equation. The goal behind this effort is to explore the previously intractable physics in regimes where the mean-field theory fails, and to provide a stringent test on the validity of quantum mechanics for complex entangled systems.
    • Using circuit-level power measurements in household energy management systems

      Marchiori, Alan; Han, Qi
      The first requirement for any intelligent household energy management system is to be able to accurately measure energy usage in the home. Measuring energy usage is not difficult; however we must decide what to measure. Whole-home energy measurement is cheap and easy to setup because only one sensor is placed where the home connects to the power grid. The collected data can provide useful information for large appliances. However, the only way to monitor the energy usage of smaller devices is to install an energy meter on every device of interest. This creates a very detailed picture of household energy consumption, but requires a lot of additional hardware--one meter per device in the home. Here we explore an alternative, more practical, approach to monitor household energy usage including small devices. Our approach uses circuit-level power measurements and a new method to separate aggregate data into device-level estimates. Our initial evaluation resulted in an average error less than 5.35% for three devices with good response to changing device state. We therefore believe that this approach, coupled with a device-level control system, would create an ideal architecture for the next generation of household energy management systems.
    • Technique for large-scale EBSD mapping of polycrystalline silicon

      Guthrey, Harvey; Moutinho, Helio; Al-Jassim, Mowafak; Gorman, Brian P.
      The use of the electron backscattered diffraction (EBSD) technique to create maps of polycrystalline materials is generally limited to areas less than a square millimeter. In order to map larger areas, steps must be taken to address issues such as specimen preparation of large surface areas and orientation of these large specimens so they can be mounted appropriately in the microscope. Issues related to scanning areas larger than the SEM field of view and incorporating the results of these individual scans in to a final map are also still challenges. In this work we present the procedure and results for EBSD mapping of a polycrystalline silicon wafer with an area of 156 X 156 mm2. Techniques for field stitching, choosing pixel densities, and potential hardware modifications for EBSD mapping of large samples will be discussed.
    • New route to sulfonic acid functional polymers

      Rebeck, Nathaniel T.; Knauss, Daniel M.
      A new route to sulfonic acid functional polymershas been developed, where a protected sulfonic acid moiety is used to carryout a controlled and directed sulfonation of poly(aryl ethers). These polymers have a variety of applications, however, the main focus of this research is to produce ion-conducting membranes and study this ion conduction at a fundamental level. By employing a protected sulfonic acid functionality, the acid will be generated in a controlled manner after polymerization to produce functional polymers without interfering with the polymerization. Using this process the properties of the polymer membrane can be adjusted by varying the position of the acid and the backbone linkages of the polymer. Studying these changes can give some insight into ion conduction in these materials. In order to produce these new materials, a novel monomer was developed utilizing a sulfonamide moiety. This moiety has been used extensively as a protecting group for sulfonic acids and amines. It has also been shown to activate aryl halides for nucleophilic aromatic substitution but has never been used for polymerization. In utilizing this group to produce the desired materials, this research has shown the sulfonamide is a new activating group for nucleophilic aromatic substitution polymerization. This monomer produces high molecular weight stable polymers.
    • Mineralogy and its contribution to anisotropy and kerogen stiffness variations with maturity in the Bakken shales

      Prasad, Manika; Mba, Kene
      The understanding of the controls on anisotropy and stiffness of the soft components (kerogens and clays) of organic-rich shales is important in developing methods for indirect and in-situ detection of maturity. Mineralogy of eleven Bakken shale samples with varying thermal maturities was studied to determine the contribution of mineralogy to anisotropy and kerogen stiffness variations between the shales. It was found that anisotropy increased with increasing clay content and that kerogen stiffness increased with maturity. Increasing clay content allows for increased micro-cracking during hydrocarbon expulsion, and so increased anisotropy. This clay-related anisotropy is independent of depth. Rock physics models aimed at the indirect prediction of maturity in organic-rich shales need to account for clay-related anisotropy and kerogen stiffness changes for better accuracy in impedance modeling.
    • Microbial diversity associated with single cell protein produced from a brewery wastewater pilot plant

      Lee, Jackson Z.; Spear, John R.
      Background: Brewery wastewater typically contains large untapped amounts of useful dissolved carbon measured as Biological Oxygen Demand (BOD) that can be utilized for protein production for fish feed in the form of Single Cell Protein (SCP). Protein is produced from the growth of bacteria as it consumes carbon and is harvested and dried into a fishmeal replacement. Here we present results of a 1-year biodiversity monitoring study of a brewery wastewater treatment pilot plant tuned to produce a dried bacterial Single Cell Protein (SCP) fishfeed replacement product. The plant consistently produced 55-60% (w/w) crude protein SCP at about 15 kg/day. The key to this consistency was the addition of micronutrients to the wastewater during aerobic growth, but the exact microbial response to this addition was not well understood. Materials and Methods: An initial survey of the brewery wastewater operations was conducted over the year 2008 using Sanger sequencing of the 16S SSU rRNA gene with the 8F/1492R primer. Samples were taken from throughout the brewery treatment works and pilot plant to establish a time course. Next, A 454 FLX pyrosequencing run was also completed using normalized DNA from the same samples as above with the bacterial 27F/338R primers and sample barcoding. Pyrotags were processed and clustered into Operational Taxonomic Units (OTUs) by the MOTHUR bioinformatics package. Results: Ribosomal Database Project classifications of Sanger data showed that while the order level diversity was relatively simple, the consortia varied considerably both in time and in location. Pyrotag data (55,000 sequences) was characterized by a high degree of singleton OTUs. No single sequence comprised more than 2% of all sequences and no two samples (in either time or space) contained more than 10% OTU similarity. Phylum-level pyrotag diversity of the pilot production tank revealed dominance by Bacteroidetes followed by Firmicutes and beta/gamma-Proteobacteria. Fast UniFrac results show that SCP product and pilot plant environments sometimes clustered together, and that some temporal clustering also occurs. More significantly, Fast UniFrac results show that each segment of the treatment works was highly selective. In order to understand where variations in Fast UniFrac data exist, a taxonomic rank abundance plot was made which details distributions of sequences within various phylum. Results show that major contributors to community structure lie in Firmicutes and Beta-proteobacteria, but the majority of dominant organisms come from Bacteroidetes, particularly from genus Prevotella, a group of carbohydrate metabolizing anaerobes commonly associated with tooth decay. Conclusion: These results indicated that the bulk of diversity in the pilot plant were low count species and that high turnover led to considerable shifts in diversity within several major phyla, particularly from phylum Bacteroidetes, though overall protein concentration of the system remained consistent for the production of SCP. These results indicate that minute changes in reactor conditions commonly seen in day-to-day operations at any treatment plant can cause wide fluctuations in reactor diversity without impacting process stability.
    • Coalbed methane produced water organic matter characterization: contribution, origin, and potential impact on membrane treatment technologies

      Dahm, Katharine G.; Van Straaten, Colette M.; Drewes, Jorg E.
      Coalbed methane (CBM) is an unconventional gas source with large worldwide reserves. CBM wells are screened along coal seams, where water is produced to release pressure and allow methane to desorb from the coal surface (Orem, 2007). This practice has environmental impacts from disposal of co-produced, highly saline water. Industry treats co-produced water as a waste product. Water is commonly re-injected back into deeper aquifers for disposal. Lack of aquifer storage capacity directly limits gas production unless a solution for water treatment can be found. Regions in the US where CBM occurs in extractable quantities also are regions commonly experiencing water shortages. Utilizing produced water for irrigation, stream flow enhancement and drinking water augmentation is hindered by limited knowledge of water quality and variability. CBM produced water has total dissolved solid concentrations ranging from 1,500 to more than 30,000 mg/L (Benko and Drewes, 2008). In addition to dissolved inorganic constituents, naturally-occurring organic compounds are also present. High pressure membranes have the potential to desalinate produced water to standards required for beneficial use. Little, however, is known about the characteristics of the naturally occurring organic matter and impacts on membrane fouling. Characteristics of organic matter present in produced water derive from sources within the system. Produced water samples, brackish groundwater, and deep-sea ocean water were evaluated to determine dominant chemical signatures. The carbon content in coal suggests dominant characteristics of organic matter in CBM produced water are derived from coal-water interactions. Coal samples were utilized in microcosm experiments to determine interaction chemistry of organic matter leaching off coal surfaces. Complexation of metals and organic matter dictate the size, active concentration, and dominate chemical identity of dissolved organic matter. Complexation with ions, particularly heavy metals, determines the range of organic matter leaching off the coal surface as well as the in-situ organic and inorganic constituent distribution. Experimentation to determine the range of organic matter characteristics, type, size and concentration from different sources support evidence from microcosm experiments that a majority of naturally occurring organic matter originates from coal water interactions. Coal type organic matter characteristics and effects of metal complexation help to predict the potential impacts of coal derived organic matter on membrane fouling. Benko, K. and J. Drewes. 2008. Produced water in the western United States: Geographical distribution, occurrence, and composition. Environmental Engineering Science 22:239-246. Orem, W.H., C. A. Tatu H.E. Lerch, C.A. Rice, T.T. Bartos, A.L. Bates, S. Tewalt and M.D. Corum. 2007. Organic compounds in produced waters from coalbed natural gas wells in the Powder River Basin, Wyoming, USA. Applied Geochemistry 22:2240-2256.
    • Phosphonic acid based copolymer fuel cell membrane

      Schlichting, Gregory J.; Horan, James L.; Dillon, Anne C.; Herring, Andrew M.
      Advances in fuel cell membranes are needed for commercialization to be realized. These advances need to be made in many areas including mechanical durability, chemical resistance and increased power density. However, advances in the first two areas need to be accompanied by an increase in power density, in which the underlying problem is the rate of ionic transport. There are two main ways to increase transport; increase the hydration within the membrane to increase proton transfer via the vehicle mechanism or to increase the acidity of the polymer by using super-acids or increasing the number of acidic groups present. Since there are many benefits to being able to run under hot, dry conditions, the second approach is more acceptable for designing a new copolymer system. In this work, zirconium divinyl phosphonate (VZP) has been copolymerized with vinyl phosphonic acid (VPA) to not only increase the number of acidic sites compared to many other polymer systems, but to also incorporate a super acid to help increase conductive pathways. 20%VZP co-VPA was synthesized via free radical polymerization to form a clear, flexible membrane with high proton conductivity. The film has been characterized using XRD, SAXS, FTIR, CPMAS NMR, TGA, DSC, PFGSE NMR and EIS. Characterization revealed an amorphous copolymer. Further tailoring and optimization of this system could yield a commercially viable fuel cell membrane.
    • TestbedProfiler v2: an improved validation tool for wireless sensor network testbed deployment

      Han, Qi; Marchiori, Alan; Thomas, Josh
      A key aspect of deploying a wireless sensor network (WSN) is understanding the degree of connectivity between the individual nodes that comprise the network. Towards that end, we present the second incarnation of TestbedProfiler, an application suite designed to aid the installation and improvement of WSN testbeds by revealing the characteristics of their underlying connections. Such knowledge allows node placement to be optimized to best fit the needs of a specific application. Originally developed with the capacity to evaluate network connectivity and performance based on transmission power level and packet size, the new TestbedProfiler can also measure the impact of specific radio channels and affords a much greater degree of control over its operation. Additionally, automated analysis of the resulting data now includes expected transmission count (ETX) and easily generated graphs that allow the connectivity of the network as a whole or of a single node to be visualized at a glance. The TestbedProfiler suite will be made freely available to other researchers and will hopefully lead to improved testbed deployments and better real-life WSN applications.
    • Predictive bio-computational wear modeling for joint replacements

      Armstrong, Jeffrey R.; Petrella, Anthony J.
      Polyethylene wear has long been a topic of concern for the longevity of joint replacement systems as bearing failure is the leading cause for the need of revision surgery. Experimental simulations are costly and time consuming; therefore, a more efficient solution for predicting wear is computer simulation. Predictive computational modeling of the adhesive/abrasive wear mechanism has been in use for over a decade, but the accuracy of such models is still under debate [1-7]. Recent studies have shown that cross-path motion, as seen in joint replacements, results in elevated wear and shortens the life of the polyethylene bearing surface [8-10]. Modern computer simulations have attempted to address the effects of cross-path motion and range from simple to complex formulations [9, 11-13]. Current models are limited by their complexity, computational efficiency, joint-specificity, or motion-cycle path dependence. In this study, an adaptive finite element (FE) model was used to implement a modified form of Archard's Wear law [1] that accounts for the effects of cross-path motion and polymer chain realignment. The proposed model was validated to three separate experimental wear systems, each with three loading scenarios. As seen in Equation 1, the proposed Modified Archard's law sums the effects of unidirectional and cross-path motion and also accounts for polymer chain realignment, referred to as 'memory'. This Modified Archard's law is simple and generally applicable to any wear system: [Eqn 1.] where 'k0' and 'k*' are experimentally derived wear coefficients for uni-directional and cross-path sliding, respectively. The variable 'p' refers to contact pressure and the variable s is the magnitude of incremental sliding distance. The variable 'm' incorporates memory and sliding trajectory effects; its full definition can be found in [14]. Validation of the proposed wear model was completed through comparisons to published experimental data for three wear systems. The first system was a pin-on-disk wear experiment by Dressler et al. [15]. They concluded that wear was elevated by changes in direction but that the elevated wear diminished with sliding in a consistent direction up to 5 millimeters. Application of previous models to this experimental system resulted in incorrect wear predictions. Application of the proposed Modified Archard's law was able to predict the experimental wear volume results exactly. Further validation was confirmed when the Modified Archard's law was applied to FE models of a cervical disk replacement and a total knee replacement, as seen in Figure 1. The cervical disk model was made in accordance with the experimental setup by Bushelow et al. [16]. The total knee replacement model was made in accordance to the setup by McEwen et al. [10]. Experimental wear depth and volume results were compared to predictions from both the classical and Modified forms of Archard's Wear law for each of the two experiments three distinct loading scenarios. Wear coefficients were scaled to a standard loading scenario for each system. In each of the two predicted scenarios of both experiments, the Modified Archard's Wear law showed a better fit to the experimental data than the classical Archard's Wear formulation. Bibliography: [1] Archard 1953; [2] Maxian et al. 1995; [3] Kang et al 2009; [4] Knight et al 2007; [5] Pal et al 2008; [6] Ghiglieri et al 2008; [7] Goreham-Voss 2009; [8] Bragdon et al 1996; [9] Turrel et al 2003; [10] McEwen et al 2005; [11] Wang 2001; [12] Hamilton et al 2005; [13] Knight et al 2006; [14] Petrella et al 2009; [15] Dressler et al 2009; [16] Bushelow et al 2009.
    • Statistical shape model for probabilistic studies of the lumbar spine, A

      Huls, Kelli S.; Petrella, Anthony J.
      Introduction: Computational modeling of the spine has become a promising option for evaluating the performance of new spinal implants and procedures before they are used in patients. Most models in the literature only represent a single subject and neglect normal variation that exists between specimens. However, using a probabilistic simulation (select input variables from a normal distribution and determine how they affect outputs) of virtual patients, whose geometries are representative of actual patients, may lead to viable options for pre-clinical evaluation of devices and procedures. One of the major challenges to overcome when applying probabilistic modeling techniques to biologic systems is to capture normal shape variation between subjects. Methods: Vertebral body geometries from 8 normal CT scans were used to develop a statistical shape model (SSM) of the lumbar spine. The SSM model is comprised of eigenvalues and eigenvectors calculated with a principle component analysis. Eigenvectors, also called modes, represent how shape varies in the geometry and eigenvalues represent how important each mode is to the overall shape of the geometry. Any specimen can be represented by P= P_mean+Sum_(j=1,m)[b_j*c_j] where bj are scalar coefficients and cj are the eigenvectors. Virtual specimens can be created by randomly sampling the normal curve for each b coefficient. A finite element model, shown in figure 1, was developed containing eight ligaments (non-linear springs), an intervertebral disc (hyperelastic annulus, fluid cavity for nucleus), and linear elastic cartilage (2mm thick). A compression load of 800 N and 7.5 Nm of axial rotation was applied to the model and it was solved using Abaqus. The model was validated using experimental range of motion data. For the purpose of probabilistic analysis, tens to hundreds of model runs are desired. To facilitate the generation of these models, a procedure was developed to incorporate geometry from the SSM, automatically place ligaments and generate cartilage. Results: The first mode shape was a scaling mode, the second was associated with shape and angulation of the facet joints and the third produced variations in transverse processes. Higher modes were not visually obvious. Models created from virtual geometries demonstrated noticeable shape variation but they mated quantitatively similar to models generated from CT scans (naturals). Qualitatively, differences between virtual specimens and natural specimens were not statistically different for either area or average pressure. For manual and automatic cartilage, contact area was observed in the same general location and contact pressure was similar, 2.43 MPa compared to 2.22 MPa. Discussion: Shape variation in the lumbar spine was characterized using a statistical shape model. Models created with virtual specimens demonstrated facet contact similar to models generated with natural specimens. Cartilage generation that was automated for a probabilistic study resulted in quality meshes that fit flush into the facet geometry. With the success of models developed using virtual specimens, the same methods can be applied to the entire lumbar spine. Next steps for creating a probabilistic model are to automate the alignment of vertebral bones and implementation of probabilistic computations using a Monte Carlo method.
    • Model for the envelopes of spin waves in magnetic film feedback rings, A

      Anderson, Justin; Carr, Lincoln D.; Wu, Mingzhong
      Experimental observation of spin wave envelopes(SWE) in magnetic thin films necessarily occurs in non-conservative systems. The generation of time-stable results is realized by approximating conservation through active feedback, or otherwise driving the system into equilibrium with its major linear loss mechanisms. A rich variety of SWE nonlinear dynamics have successfully been observed in "conservative" systems of this form, including chaos, soliton formation, and more recently, a chaotic modulation of solitary wave train envelopes. The dynamics of these "conservative" systems have often been modeled by a 1D Ginzburg-Landau Equation (GLE) of the general form, -d_t Phi=(Dd_xx+N|Phi|^2)Phi, where D and N are real parameters corresponding to the system's inherit dispersion and nonlinearity, respectively, and Phi is the SWE wavefunction. Extension to multiple dimensions is the trivial introduction of a Lapacian operator in place of the spatial derivative. The GLE is a fully conservative equation which has succeeded in modeling SWE solitons in these dissipative systems. However, the cubic GLE does not yield chaos and the severity of the nonlinear term, which is a function of the wavefunction normalization, exhibits time dependence in any dissipative system due to loss and gain. A driven damped model is proposed to overcome the shortcomings of the traditional GLE and is studied numerically in the context of the chaotic modulation of solitary waves. The model is a cubic, quintic complex GLE (CGLE) with constant gain, -d_t Phi=(Dd_xx+(N+iG) |Phi|^2-iL-(Q+iS)|Phi|^4)Phi, where all constants, D, N, G, L, Q, S, are real. This modification of the GLE introduces higher order nonlinearity and a gain/loss mechanism at linear, cubic, and quintic orders. A preliminary investigation of the CGLE is reported and a qualitative agreement of simulations with experimental observation is demonstrated. A saturation of cubic nonlinearity, of the four-wave process, is suggested as the driving force behind the chaotic modulation of magnetic SWE solitary waves, and predictions of experimentally achievable chaotic domains are presented. This work is supported by the U.S. National Science Foundation.
    • Hydrogen peroxide dynamics in an agricultural headwater stream: evidence for significant biological production

      Dixon, Taylor C.; Voelker, Bettina M.
      Hydrogen peroxide (H2O2) is known to play key roles in aquatic systems, including metal redox cycling and degradation of organic matter into bioavailable forms. Detailed knowledge of the cycling of H2O2 in natural waters thus fosters the understanding of important aquatic biogeochemical processes. Although biological production of H2O2 has been observed in culture studies, the significance of this process to the H2O2 budget in freshwater systems remains unknown. In this study, isotopically-labeled H2O2 (H218O2) was added to novel in-stream mesocosm systems exposed to light and dark periods. By measuring total H2O2 and H218O2 in tandem, we inferred absolute rates of H2O2 production and decay, which were occurring simultaneously. The results indicate rates of H2O2 production up to several-fold the photo-production rates observed in filtered water samples, and suggest biological production as the dominant control on the H2O2 budget in the agricultural headwater stream studied. The potential implications of this work include enhanced understanding of freshwater metal and organic matter bioavailability, and natural attenuation of aquatic contaminants.
    • ADMIRE: Autonomous Dam Monitoring with Integrated Real-time Evaluation

      Stone, Kerri; Camp, Tracy
      Dams have a large impact on public safety in the United States. Dam failures are far reaching and may result in loss of property, loss of life, and loss of water storage. Despite this fact, dam inspections occur infrequently and are performed unevenly across the structure. As such, current dam monitoring practice is often incapable of detecting internal erosion - a primary failure mode in dams. The inability to detect internal erosion results in increased risk of catastrophic failure. This research focuses on the development of a wireless sensor network (WSN) application to autonomously and continuously monitor embankment dams for signs of internal erosion. To date, a WSN has not been used to assess dam integrity. The use of a WSN to autonomously and continuously monitor dams will improve the ability to detect structural issues before failure occurs. This research develops ADMIRE - Autonomous Dam Monitoring with Integrated Real-time Evaluation, which will continually assess dam integrity through minimally invasive geophysical sensing techniques integrated into a WSN. ADMIRE will implement a machine learning algorithm to calculate the probability of internal erosion based on geophysical sensor measurements. Upon calculating a high probability of internal erosion, the WSN will employ a distributed algorithm to localize the occurrence of internal erosion. ADMIRE will allow for autonomous and continuous monitoring of embankment dams. ADMIRE will contribute significant technological advancements to dam inspection practice.
    • Development of a directionally independent roller measurement value

      Facas, Norman; Mooney, Michael A.
      Continuous Compaction Control (CCC) and Intelligent Compaction (IC) rollers promise large potential improvements for earthwork construction. CCC rollers provide a spatial measure of soil properties (e.g., stiffness) over the earthwork surface. CCC rollers can be used for quality control/quality assurance (QC/QA) to enable compaction based feedback control and to create as-built documentation. CCC rollers offer great promise for QC/QA by enabling 100% evaluation of an earthwork area during every roller pass, in contrast to current quantitative QC/QA which evaluates less than 1% of the earthwork after a few roller passes. Experimental data has shown that vibratory roller compactors often exhibit rotational kinematics in addition to translation during operation. This rotation is not considered in the current generation of roller measurement values. A new roller/soil model that allows for rotational kinematics was developed. Using the model, the influence of sensor position on roller measurement values is examined. The influence of drum rotation is shown to be significant. Building upon these findings, a new technique is developed for computing roller measurement values while negating the influence of rotation. This new technique is shown to be directionally independent. The new measurement technique is compared verse the current measurement technique for common CCC roller tasks.
    • Predicted response of microstructure, distortion, and residual stress in carburized steels cooled via oil and high intensity quenching

      Speer, J. G.; Baker, Daniel
      Heat treatment simulations provide a new capability to understand and predict complicated responses, where thermal, mechanical, and microstructural effects are coupled. Simulations using DANTE® compared the response of carburized and non-carburized 4120, 4320, and 8620 to oil and high intensity quenching. High intensity quenching involves high heat transfer rates and has the potential to reduce alloy content and carburization level compared to hot oil quenching. The simulations utilized a simple rod shape in order to minimize part geometry effects. The development of the microstructure, residual stress, and distortion are compared to understand the differences between high intensity quenching and oil quenching. The simulations predicted compressive residual hoop stresses at the surface for all high intensity quench conditions. In contrast, oil quenching produced compressive residual hoop stresses at the surface in the carburized condition and tensile residual hoop stresses in the non-carburized condition.