A Bayesian Periodogram Finds Evidence for Three Planets in 47 Ursae Majoris

A Bayesian analysis of 47 Ursae Majoris (47 UMa) radial velocity data confirms and refines the properties of two previously reported planets with periods of 1079 and 2325 days and finds evidence for an additional long period planet with a period of approximately 10000 days. The three planet model is found to be 10^5 times more probable than the next most probable model which is a two planet model. The nonlinear model fitting is accomplished with a new hybrid Markov chain Monte Carlo (HMCMC) algorithm which incorporates parallel tempering, simulated annealing and genetic crossover operations. Each of these features facilitate the detection of a global minimum in chi-squared. By combining all three, the HMCMC greatly increases the probability of realizing this goal. When applied to the Kepler problem it acts as a powerful multi-planet Kepler periodogram. The measured periods are 1078 \pm 2, 2391{+100}{-87}, and 14002{+4018}{-5095}d, and the corresponding eccentricities are 0.032 \pm 0.014, 0.098{+.047}{-.096}, and 0.16{+.09}{-.16}. The results favor low eccentricity orbits for all three. Assuming the three signals (each one consistent with a Keplerian orbit) are caused by planets, the corresponding limits on planetary mass (M sin i) and semi-major axis are (2.53{+.07}{-.06}MJ, 2.10\pm0.02au), (0.54\pm0.07MJ, 3.6\pm0.1au), and (1.6{+0.3}{-0.5}MJ, 11.6{+2.1}{-2.9}au), respectively. We have also characterized a noise induced eccentricity bias and designed a correction filter that can be used as an alternate prior for eccentricity, to enhance the detection of planetary orbits of low or moderate eccentricity

Evaluating Security and Quality of Service Considerations in Critical Infrastructure Communication Networks

This thesis demonstrates the benefits of utility communication based on Internet technology, some dangers in using Internet technology in establishing a utility intranet connecting protection and control systems, and compares three different approaches to making reservations for routing traffic in the utility intranet based on different levels of background traffic. A model of expected background traffic on a national utility intranet is presented. The Utility Communication Architecture 2.0 and the International Electrotechnical Commission (IEC) 61850 began laying the groundwork in 2002 in establishing an infrastructure allowing power substations, program logic controllers, remote terminal units, intelligent electronic devices, and other devices to effectively and efficiently communicate over a utility intranet that is based on Internet standards using commercial of the shelf (COTS) components. This intranet will almost certainly be based on Internet standards due to their widespread use, low cost, and easy migration path over time. Even though it’s based on Internet technology the utility intranet will allow utilities to connect to one another without exposing them to threats from the Internet. This will provide utilities with the needed insight into other areas of the power grid enabling them to better manage its operation. The Electrical Power Communication Synchronization Simulator (EPOCHS) is used in this thesis to run simulations that models network traffic over a power infrastructure in order to show the effects of using different protocols, bandwidth reservations, and varying levels of background traffic will have on the quality of service of intranet traffic, with the end result of improving the insight the different regions of the utility intranet will have with each other. EPOCHS provides the required simulation environment needed to integrate a network simulator with an electromechanical power simulator to run the simulations. This research discusses the benefits of utility communication, the likely pitfalls in the use of Internet technology for protection and control systems, and technologies that can help mitigate those pitfalls. A total of 48 different simulation configurations are performed based on background traffic, reservation type, IP transport protocols, and routing scheme used to determine which configuration is best suited for use on a utility intranet

Pseudomorphic growth of InAs on misoriented GaAs for extending quantum cascade laser wavelength

The authors have studied the impact of epilayer strain on the deposition of InAs/GaAs on (100) and (111)B with 2 degrees offset toward 2-1-1 surfaces. Consequences of a 7% lattice mismatch between these orientations in the form of three-dimensional growth are less apparent for (111)B with 2 degrees offset toward 2-1-1 surfaces compared to (100). By exploring a range of molecular beam epitaxy process parameters for InAs/GaAs growth and utilizing scanning electron microscopy, atomic force microscopy, and Raman spectroscopy to evaluate the quality of these strained layers, the authors develop empirical models that describe the influence of the process conditions in regards to surface roughness with \u3e92% accuracy. The smoothest InAs/GaAs samples demonstrated average surface roughness of 0.08 nm for 10 um-squre areas, albeit at very low deposition rates. The authors have found the most important process conditions to be substrate temperature and deposition rate, leading us to believe that controlling diffusion length may be the key to reducing defects in severely strained structures. InGaAs/AlGaAs quantum cascade laser structures were also produced on (111)B with 2 degrees offset toward 2-1-1 to take advantage of the piezoelectric effect, and the modified laser transitions due to these effects were observed

Authentic assessment of reflection in an ePortfolio: How to make reflection more real for students

In a doctoral study that focused on the enhancement of reflection through an ePortfolio-based learning environment, students’ indicated that they felt reflection was not real when it was used for assessment. This led to an examination of assessment practices linked to reflection and ways to make it authentic. The literature revealed that reflection is often a component of authentic assessment rather than being a focus of it. The practices associated with the assessment of reflection are examined in order to formulate 4 guiding principles. These principles aim to make the process of reflection more ‘real’ to students in higher education settings, particularly when using an ePortfolio platfor

Operational rules to manage power consumption for content display

The display is often responsible for a large proportion of the overall power consumed by a device. The total power consumption of a display depends on a number of factors such as the number of pixels that need to be switched on, the color and brightness of the pixels, and the rate at which the on-screen content is updated. Displays that draw high amounts of power can deplete the available power resources of a device relatively quickly, thus shortening the amount of time a user can operate the device without needing to charge or replace the device battery. This disclosure describes techniques to specify and enforce a system of rules that dictate the operation of display pixels while rendering the content to be displayed. The rules describe upper or lower bounds for various pixel-related parameters such as switched on state, color, brightness, refresh rate, etc

Authentic assessment of reflection in an ePortfolio: how to make reflection more real for students

In a doctoral study that focused on the enhancement of reflection through an ePortfolio-based learning environment, students' indicated that they felt reflection was not real when it was used for assessment. This led to an examination of assessment practices linked to reflection and ways to make it authentic. The literature revealed that reflection is often a component of authentic assessment rather than being a focus of it. The practices associated with the assessment of reflection are examined in order to formulate 4 guiding principles. These principles aim to make the process of reflection more 'real' to students in higher education settings, particularly when using an ePortfolio platform