Partial rotor-to-stator rub demonstration

A rotor radial rub typically occurs in seals or at a blade tip or shroud when there is insufficient clearance, high vibration, or the shaft equilibrium position has been displaced to effectively limit the clearance (eccentricity). There are two extreme cases of radial rubs: full annular rub, when the rotor maintains continuous contact with the seal, etc.; and a partial rub, when the contact occurs during a fraction of the precession period. They both involve similar physical phenomena such as friction and modification of stiffness. In partial rubs with consecutive impacts, a significant average value of radial force is generated. This results in shaft average displacement in the direction opposite the rub location. The rotor rig demonstrates the characteristics of a partial lateral rub of varying severity and location. These characteristics include: (1) subharmonic components as a function of rotative speed/first balance resonance ratio and radial force; (2) higher harmonic content as a function of severity; (3) increased average rotor stiffness resulting in increased first balance resonance speed; and (4) change in overall orbital pattern as a sum of the unbalance response (1x) and subharmonic response (1nx)

Interview of Robert and Susan Grissom

Hacker interviews Robert and Susan Grissom on their experiences in the mission field in Brazil. The interview was conducted in Searcy, AR

Gower as Data: Exploring the Application of Machine Learning to Gower’s Middle English Corpus

Distant reading, a digital humanities method in wide use, involves processing and analyzing a large amount of text through computer programs. In treating texts as data, these methods can highlight trends in diction, themes, and linguistic patterns that individual readers may miss or critical traditions may obscure. Though several scholars have undertaken projects using topic models and text mining on Middle English texts, the nonstandard orthography of Middle English makes this process more challenging than for our counterparts in later literature. This collaborative project uses Gower’s Confessio Amantis as a small, fixed corpus for analysis. We employ natural language processing to reexamine the Confessio’s themes, adding data analysis to the more traditional close reading strategies of Gower scholarship. We use Gower’s work as a case study both to help reduce the potential variants across textual versions and to more deeply investigate the corpus than distant reading normally allows. Here, we share our initial findings as well as our methodologies. We hope to share resources that will allow other scholars to engage in similar types of projects

Frequency Space Correlation Between REITs and Capital Market Indices

Several studies have examined real estate investment trust (REIT) co-movement with stocks or bonds using traditional time domain based methods, such as linear regression or correlation. Results of these studies have produced inconsistent statistical model parameters. The erratic behavior of the models may have resulted from the different time periods in the studies, the REITs included in a study or the market indices. Another factor contributing to the variation of the models comes from the compression of cyclical information over a study?s time period by time domain based techniques. Cross-spectral analysis provides a frequency space method of examining the coherency (i.e., frequency space correlation) between two time series across all frequencies. This article contains an examination of the coherency between REITs and stock market indices and REITs and U.S. Treasury debt indices for the period 1989-95. Results of the coherency spectra show significant co-movement between REITs and stock market indices, while debt instruments show very few frequencies with significant coherency. Furthermore, phase spectra provide evidence of contemporaneous movement between REITs and stock indices at all frequencies.

Forecasting Dynamic Investment Timing under the Cyclic Behavior in Real Estate

This paper applies the Hodrck-Prescott (HP) filter to forecast short-term residential real estate prices under cyclical movements. We separate the trend component from the cyclical component. We show that each regional residential market reacts not only to previous price movements, but also that these regional markets react to previous shocks under Auto Regressive Integrated Moving Average (ARIMA) modeling. Using the S&P Case-Shiller Home Price Index, we compare our forecast to index values from the Chicago Mercantile Exchange (CME) Housing Futures and Options. Our study identifies possible systematic errors from the different price adjustments reflecting current market situations.Real estate investment; Real estate cycle; residential housing futures contract; Real estate risk hedging

The Analysis of Real Estate Cycles, Regime Segmentation and Structural Change Using Multiple Indices (or A Multiple Index Analysis of Real Estate Cycles and Structural Change)

This article explores real estate cycles and structural change at an overall industry level, focusing on three key questions. First, are real estate cycle stages distinct and observable? Second, can the cycle stages be modeled using variables and relationships that hold for extended periods? Third, can the impact of exogenous shocks that cause structural changes in the market be monitored and modeled? The results of the research are generally positive, suggesting that indeed the variables and relationships that distinguish various real estate cycle stages can be isolated, and are sufficiently stable to help model cyclical changes. Furthermore, the research suggests it is possible to track key exogenous shocks that trigger structural changes that affect cycle models.

Ground Robotic Hand Applications for the Space Program study (GRASP)

This document reports on a NASA-STDP effort to address research interests of the NASA Kennedy Space Center (KSC) through a study entitled, Ground Robotic-Hand Applications for the Space Program (GRASP). The primary objective of the GRASP study was to identify beneficial applications of specialized end-effectors and robotic hand devices for automating any ground operations which are performed at the Kennedy Space Center. Thus, operations for expendable vehicles, the Space Shuttle and its components, and all payloads were included in the study. Typical benefits of automating operations, or augmenting human operators performing physical tasks, include: reduced costs; enhanced safety and reliability; and reduced processing turnaround time