eCommons Collection:
http://hdl.handle.net/1813/39
Fri, 24 Apr 2015 16:51:13 GMT2015-04-24T16:51:13ZRepresentation Of Uncertainty And Corridor Dp For Hydropower Optimization
http://hdl.handle.net/1813/39482
Title: Representation Of Uncertainty And Corridor Dp For Hydropower Optimization
Authors: Lamontagne, Jonathan
Abstract: This thesis focuses on optimization techniques for multi-reservoir hydropower systems operation, with a particular concern with the representation and impact of uncertainty. The thesis reports on three research investigations: 1) examination of the impact of uncertainty representations, 2) efficient solution methods for multi-reservoir stochastic dynamic programming (SDP) models, and 3) diagnostic analyses for hydropower system operation. The first investigation explores the value of sophistication in the representation of forecast and inflow uncertainty in stochastic hydropower optimization models using a sampling SDP (SSDP) model framework. SSDP models with different uncertainty representation ranging in sophistication from simple deterministic to complex dynamic stochastic models are employed when optimize a single reservoir systems [similar to Faber and Stedinger, 2001]. The effect of uncertainty representation on simulated system performance is examined with varying storage and powerhouse capacity, and with random or mean energy prices. In many cases very simple uncertainty models perform as well as more complex ones, but not always. The second investigation develops a new and efficient algorithm for solving multi-reservoir SDP models: Corridor SDP. Rather than employing a uniform grid across the entire state space, Corridor SDP efficiently concentrates points in where the system is likely to visit, as determined by historical operations or simulation. Radial basis functions (RBFs) are used for interpolation. A greedy algorithm places points where they are needed to achieve a good approximation. In a four-reservoir test case, Corridor DP achieves the same accuracy as spline-DP and linear-DP with approximately 1/10 and 1/1100 the number of discrete points, respectively. When local curvature is more pronounced (due to minimum-flow constraints), Corridor DP achieves the same accuracy as spline-DP and linear-DP with approximately 1/30 and 1/215 the number of points, respectively. The third investigation explores three diagnostic approaches for analyzing hydropower system operation. First, several simple diagnostic statistics describe reservoir volume and powerhouse capacity in units of time, allowing scale-invariant comparisons and classification of different reservoir systems and their operation. Second, a regression analysis using optimal storage/release sequences identifies the most useful hydrologic state variables . Finally spectral density estimation identifies critical time scales for operation for several single-reservoir systems considering mean and random energy prices. Deregulation of energy markets has made optimization of hydropower operations an active concern. Another development is publication of Extended Streamflow Forecasts (ESP) by the National Weather Service (NWS) and others to describe flow forecasts and their precision; the multivariate Sampling SDP models employed here are appropriately structured to incorporate such information in operational hydropower decisions. This research contributes to our ability to structure and build effective hydropower optimization models.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394822015-01-26T00:00:00ZFiniteness Properties And Piecewise Projective Homeomorphisms
http://hdl.handle.net/1813/39477
Title: Finiteness Properties And Piecewise Projective Homeomorphisms
Authors: Lodha, Yash
Abstract: In 1929 the mathematician and physicist John von Neumann isolated an analytic property of groups from the Banach-Tarski paradox. This property is now known as amenability. He observed that groups which contain the free group of rank 2, or F2 , are nonamenable and asked whether all nonamenable groups contain F2 . This was disproved by Ol'shankii [27] and independently by Adyan [2][3] in 1979. The first finitely presented counterexample was constructed in 2003 by Olshanskii and Sapir [28]. In [26] Monod introduced a new family of counterexamples. However, Monod's examples are not finitely presentable (or even finitely generated). In this thesis we will isolate a finitely presentable nonamenable subgroup of Monod's group H(R). (This is joint work with Justin Moore [24].) The group is generated by a(t) = t + 1 together with: b(t) = t t 1[-]t 3 [-] 1 t t + 1 if t [LESS-THAN OR EQUAL TO] 0 if 0 [LESS-THAN OR EQUAL TO] t [LESS-THAN OR EQUAL TO] if 1 2 1 2 [LESS-THAN OR EQUAL TO]t[LESS-THAN OR EQUAL TO]1 c(t) = 2t 1+t t if 0 [LESS-THAN OR EQUAL TO] t [LESS-THAN OR EQUAL TO] 1 otherwise if 1 [LESS-THAN OR EQUAL TO] t An isomorphism between the group a, b and Thompson's group F was discovered by Thurston in the late 1970's by considering the reals as continued fractions. We extend Thurston's work to a, b, c , and use this as a combinatorial framework to show the following: Theorem. The group a, b, c is finitely presented with 3 generators and 9 relations. We also obtain a natural infinite presentation, a normal form, and an algorithm for converting a given word to a word in normal form using the relations. Further, we show the following: Theorem. The group a, b, c acts on a connected cell complex X by cell permuting homeomorphisms such that the following holds. 1. X is contractible. 2. The quotient X/ a, b, c has finitely many cells in each dimension. 3. The stabilizers of each cell are of type F[INFINITY] . It follows that a, b, c is of type F[INFINITY] . This provides the first example of a group that is of type F[INFINITY] , nonamenable and does not contain F2 . Monod's technique for proving nonamenability of his groups relies on the nonamenability of the associated orbit equivalence relations. In forthcoming work we characterize all piecewise projective groups of homeomorphisms that are isomorphic to F and study the associated orbit equivalence relations. This thesis also contains the following unrelated construction which gives a new illustration of a phenomenon first exhibited by Brady [6]. Theorem. Let [GAMMA] be the complete bipartite graph with 22 vertices in each set of the partition. There is a subcomplex X of the product [GAMMA] x [GAMMA] x [GAMMA] and a map [chi] : X [RIGHTWARDS ARROW] S1 such that [pi]1 (X) is hyperbolic and the kernel H = Ker([chi]* : [pi]1 (X) [RIGHTWARDS ARROW] Z) is finitely presented but not of type F P3 . In particular, H is not hyperbolic.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394772015-01-26T00:00:00ZAn Empirical Performance Evaluation Of Different Portfolio Allocation Strategies
http://hdl.handle.net/1813/39476
Title: An Empirical Performance Evaluation Of Different Portfolio Allocation Strategies
Authors: Hu, Xiao
Abstract: Incorporating Value Averaging portfolio construction method with S&P 500 firms' Aggregate Implied Cost of Capital is an investment strategy that involves undertaking risks during market recessions and recovering strongly in post-recession periods. This strategy outperforms a pure Value Averaging strategy, Dollar Cost Averaging, and Strategic Asset Allocation under different asset class weights under the performance metrics of Internal Rate of Return, Sharpe Ratio, and Maximum Drawdown Ratio. When applying different risk-free borrowing caps, Value Averaging incorporated with Aggregate Implied Cost of Capital results in lower risks. However, it will not yield better returns unless maximum risk-free borrowing caps are relaxed. The strategy also requires a longer portfolio horizon to ensure higher Internal Rate or Return.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394762015-01-26T00:00:00ZEmissions Impacts Of Dynamic Pricing
http://hdl.handle.net/1813/39475
Title: Emissions Impacts Of Dynamic Pricing
Authors: Valentine, Olivia
Abstract: Dynamic pricing is a trendy term that can be found in a variety of industries. In the utilities industry, the implementation of dynamic pricing structure is an economic stimulus to encourage demand reduction of electricity usage in peak hours, when the power system is strained and the cost of electric power is very high. This study investigated the rate structure of day-ahead hourly pricing programs in New York State, and evaluated the demand and emissions impacts of dynamic pricing programs in the summer of 2008. Different scenarios of dynamic pricing programs are modeled to evaluate the demand and emissions change for NOx and SO2 emissions in peak hours, as well as in off-peak hours. Three methods are proposed to evaluate NOx emission reduction in New York State. Hourly emissions changes from power production in the NPCC power system model are scaled to emissions in the National Emissions Inventory (NEI), in order to simulate potential emissions changes in historical days caused by dynamic pricing. The NEI and the simulated emissions are used as point source emissions input into Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system. The processed emissions change from SMOKE is visualized using Visualization Environment for Rich Data Interpretation (VERDI). Results show that dynamic pricing programs can result in considerable emissions reduction in peak hours, while inducing a slight increase in off-peak hours. The i emissions reduction will have non-negligible environmental and social impacts for the New York State, especially for the metropolitan areas like New York City. iiMon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394752015-01-26T00:00:00ZOptimizing Response Time For Distributed Applications In Public Clouds
http://hdl.handle.net/1813/39473
Title: Optimizing Response Time For Distributed Applications In Public Clouds
Authors: Zou, Tao
Abstract: An increasing number of distributed data-driven applications are moving into public clouds. By sharing resources and operating at large scale, public clouds promise higher utilization and lower costs than private clusters. Also, flexible resource allocation and billing methods offered by public clouds enable tenants to control response time or time-to-solution of their applications. To achieve high utilization, however, cloud providers inevitably place virtual machine instances non-contiguously, i.e., instances of a given application may end up in physically distant machines in the cloud. This allocation strategy leads to significant heterogeneity in average network latency between instances. Also, virtualization and the shared use of network resources between tenants results in network latency jitter. We observe that network latency heterogeneity and jitter in the cloud can greatly increase the time required for communication in these distributed data-driven applications, which leads to significantly worse response time. To improve response time under latency jitter, we propose a general parallel framework which exposes a high-level, data-centric programming model. We design a jitter-tolerant runtime that exploits this programming model to absorb latency spikes transparently by (1) carefully scheduling computation and (2) replicating data and computation. To improve response time with heterogeneous mean latency, we present ClouDiA, a general deployment advisor that selects application node deployments minimizing either (1) the largest latency between application nodes, or (2) the longest critical path among all application nodes. We also describe how to effectively control response time for interactive data analytics in public clouds. We introduce Smart, the first elastic cloud resource manager for in-memory interactive data analytics. Smart enables control of the speed of queries by letting users specify the number of compute units per GB of data processed, and quickly reacts to speed changes by adjusting the amount of resources allocated to the user. We then describe SmartShare, an extension of Smart that can serve multiple data scientists simultaneously to obtain additional cost savings without sacrificing query performance guarantees. Taking advantage of the workload characteristics of interactive data analysis, such as think time and overlap between datasets, we are able to further improve resource utilization and reduce cost.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394732015-01-26T00:00:00ZThe Response Of The Equatorial Tropospheric Ozone To The Madden–Julian Oscillation In Tes Satellite Observations And Cam-Chem Model Simulation
http://hdl.handle.net/1813/39474
Title: The Response Of The Equatorial Tropospheric Ozone To The Madden–Julian Oscillation In Tes Satellite Observations And Cam-Chem Model Simulation
Authors: Sun, Wenxiu
Abstract: The Madden-Julian Oscillation (MJO) is the dominant form of the atmospheric intra-seasonal oscillation, manifested by slow eastward movement (about 5 m/s) of tropical deep convection. This study investigates the MJO s impact on equatorial tropospheric ozone (10N-10S) in satellite observations and chemical transport model (CTM) simulations. For the satellite observations, we analyze the Tropospheric Emission Spectrometer (TES) level-2 ozone profile data for the period of Jan 2004 to Jun 2009. For the CTM simulations, we run the Community Atmosphere Model with chemistry (CAM-chem) driven by the GOES-5 analyzed meteorological fields for the same data period as the TES measurements. Our analysis indicates that the behavior of the Total Tropospheric Column (TTC) ozone at the intraseasonal time scale is different from that of the total column ozone, with the signal in the equatorial region comparable with that in the subtropics. The model simulated and satellite measured ozone anomalies agree in their general pattern and amplitude when examined in the vertical cross section (the average spatial correlation coefficient among the 8 phases is 0.63), with an eastward propagation signature at a similar phase speed as the convective anomalies (5 m/s). The model ozone anomalies on the intraseasonal time scale are about five times larger when lightning emissions of NOx are included in the simulation than when they are not. Nevertheless, large-scale advection is the primary driving force for the ozone anomalies associated with the MJO. The variability related to the MJO for ozone reaches up to 47% of the total variability (ranging from daily to interannual), indicating the MJO should be accounted for in simulating ozone perturbations in the tropics.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394742015-01-26T00:00:00ZUnderstanding And Overcoming Limitation Mechanisms In Nb3Sn Superconducting Rf Cavities
http://hdl.handle.net/1813/39470
Title: Understanding And Overcoming Limitation Mechanisms In Nb3Sn Superconducting Rf Cavities
Authors: Posen, Samuel
Abstract: Nb3 Sn has the potential to significantly improve cryogenic efficiency and maximum fields in superconducting RF cavities, structures that impart energy to charged particle beams in large accelerators. Previous experiments demonstrated excellent cryogenic efficiency at small accelerating fields, producing cavities with surface resistance R s on the order to 10 nΩ, but it consistently increased strongly as the peak surface magnetic field exceeded the first critical field [MICRO SIGN]0 Hc1 [ALMOST EQUAL TO] 30 mT. This dissertation describes results from a new research program to investigate whether this behavior is fundamental and to determine what mechanisms ultimately limit RF superconductivity in this material. A chamber was designed and built for coating niobium substrates with a thin layer of Nb3 Sn via high temperature vapor deposition. After commissioning with samples, many coatings of single cell 1.3 GHz cavities were carried out. Several RF tests showed that small R s could be maintained up to fields significantly higher than Hc1 , showing that it is not a fundamental limitation. The field limitation encountered in these experiments was primarily quench, likely due to surface defects, based on results that include temperature mapping and high power pulsed measurements. Measurements of the temperature dependence of R s and microscopic investigations of the surface indicate that low tin content regions cause R s degradation, especially after material removal. A theoretical investigation showed that thick films have only slightly lower maximum fields than alternating layers of thin film superconductor and insulator on a bulk superconductor, and only for a small parameter range. The highest fields reached by a Nb3 Sn cavity in these experiments corresponds to an accelerating gradient of 17 MV/m, with a quality factor of 8 x 109 at 4.2 K. Cavities with this performance would significantly reduce costs in many applications, including large high duty factor linear accelerators and small-scale industrial accelerators. Additional development aided by increased understanding is expected to push performance even further.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394702015-01-26T00:00:00ZSynthesis Of Mgb2 Superconductor With Cu Doping
http://hdl.handle.net/1813/39472
Title: Synthesis Of Mgb2 Superconductor With Cu Doping
Authors: Tian, ShihaoMon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394722015-01-26T00:00:00ZEffects Of Iron Limitation And Carbon Source On Extracellular Excretions And Intracellular Carbon Metabolism In Pseudomonas Putida
http://hdl.handle.net/1813/39471
Title: Effects Of Iron Limitation And Carbon Source On Extracellular Excretions And Intracellular Carbon Metabolism In Pseudomonas Putida
Authors: Sasnow, Samantha
Abstract: Iron (Fe) is an important micronutrient in soils, essential for bacterial growth and carbon metabolism, serving as an enzymatic cofactor for many central carbon metabolic reactions. It has limited bioavailability due to being embedded in Fe oxide and hydroxide minerals. Bacteria secrete high-affinity metal-binding molecules, or siderophores, along with low-affinity organic acids to cope with Fe limitation and facilitate mineral dissolution. In the research presented, I investigated the role of available carbon sources (glucose, succinate, acetate, and citrate) on the secretion of these molecules from the ubiquitous soil bacteria Pseudomonas putida and their effectiveness in dissolving Fe from common soil minerals. Fe limited cells secreted the siderophore pyoverdine in addition to secreting higher levels of small organic acids. Dissolution experiments were carried out with bacterial secretions, substrates, and detected organic acids to determine the amount of Fe released with each organic compound. Overall, bacterial secretions were more effective in dissolving Fe than the individual substrates and organic acids. Additionally, to elucidate the changes in metabolic flux with respect to Fe, kinetic and steadystate isotopic labeling experiments were performed with [U-13C] and [1,2-13C] glucose under Felimited and replete conditions. Steady-state experiments were also performed with [2,3-13C] succinate under Fe-replete conditions to compare changes in metabolic flux between carbon sources. Overall, most fluxes decreased under Fe-limited conditions with glucose as the sole carbon source, but the flux to the amino acid precursor phosphoenolpyruvate increased. The succinate flux model showed a decrease in flux through the citric acid cycle under Fe-replete conditions, with a corresponding decrease in the amount of CO2 produced compared to Fereplete glucose. These findings indicate that the secretion of organic molecules is substrate and Fe dependent, as are the carbon fluxes through the pathways of the central carbon metabolism.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394712015-01-26T00:00:00ZNonlinear Parametric Excitation Of An Evolutionary Dynamical System
http://hdl.handle.net/1813/39468
Title: Nonlinear Parametric Excitation Of An Evolutionary Dynamical System
Authors: Ruelas, Rocio
Abstract: Evolutionary Dynamics is a field that combines Dynamical Systems with Game Theory. Game Theory studies the costs and benefits of competing strategies. This competition between strategies is called a "game" and is usually represented by a payoff matrix. The entries of the payoff matrix represent the loss or gain received when one type of strategy plays against another. Through the use of differential equations known as the replicator equations, we can use the information in the payoff matrix to model the change in relative population (or frequency) for all of the strategies. Once we have written the evolutionary equations we can study the dynamics using the methods and theorems developed in the field of Dynamical Systems. The Rock-Paper-Scissor model is used to describe systems where there are three strategies and where each strategy has an advantage over one strategy, but a disadvantage over the other strategy. The model is named after the classic game in which Rock beats Scissors, Scissors beats Paper, and Paper beats Rock. Using the replicator equations, we can model the changes that occur in the relative populations of the strategies. Strategies whose payoffs are relatively better will have increasing population frequencies while those with lower payoffs will have decreasing population frequencies. In this work, we consider a variation of the standard RPS game where the payoffs vary periodically in time. In particular, we consider a model with the following payoff matrix. R R 0 P 1 + A3 cos [omega]t S [-]1 + A5 cos [omega]t P [-]1 + A1 cos [omega]t 0 1 + A6 cos [omega]t S 1 + A2 cos [omega]t [-]1 + A4 cos [omega]t 0 (1) We began our investigation by considering a simple case of our model where we set A1 = [-]A2 = A and A3 = A4 = A5 = A6 = 0 thus reducing the number of parameters down to two. For these parameters we found that, generally, the solutions to the associated replicator equations were quasiperiodic. For some values of A and [omega], solutions that started near the interior equilibrium point would initially move away from the equilibrium point before eventually returning. Using a linear perturbation method, we were able to determine the parameter regions for which this behavior occurred. These parameter regions resemble the tongues of instability characteristic of Mathieu's equation. We were also able to determine the effects of nonlinear terms by deriving and analyzing equations for the slow flow of the replicator equations. We compared those results to numerically generated Poincar´ maps and found that they agreed for small e perturbations. Next we considered a subset of parameters in our proposed payoff matrix (1) where the interior equilibrium point persists. This results in the following conditions, A1 = A6 + A5 [-] A2 (2) A3 = A6 + A5 [-] A4 (3) We used subharmonic resonance to locate the regions in parameters space where the interior equilibrium point exhibited linear resonance. We were sur- prised to discover that for a subset of parameters these regions of linear resonance disappeared according to numerical approximations. We then proved analytically that they did in fact disappear. Finally, we extended our analytical proof so that it applied to a family of two-dimensional dynamical systems with time-varying periodic terms.Mon, 26 Jan 2015 00:00:00 GMThttp://hdl.handle.net/1813/394682015-01-26T00:00:00Z