Stability for Receding-horizon Stochastic Model Predictive Control

A stochastic model predictive control (SMPC) approach is presented for discrete-time linear systems with arbitrary time-invariant probabilistic uncertainties and additive Gaussian process noise. Closed-loop stability of the SMPC approach is established by appropriate selection of the cost function. Polynomial chaos is used for uncertainty propagation through system dynamics. The performance of the SMPC approach is demonstrated using the Van de Vusse reactions.Comment: American Control Conference (ACC) 201

Readdressing the Fertilizer Problem

The production literature has shown that inputs such as fertilizer can be defined as risk-increasing. However, farmers also consistently overapply nitrogen. A model of optimal input use under uncertainty is used to address this paradox. Using experimental data, a stochastic production relationship between yield and soil nitrate is estimated. Numerical results show that input uncertainty may cause farmers to overapply nitrogen. Survey data suggest that farmers are risk averse, but prefer small chances of high yields compared to small chances of crop failures when expected yields are equivalent. Furthermore, yield risk and yield variability are not equivalent.corn, nitrogen fertilizer, risk-increasing, yield risk, Crop Production/Industries,

Trends in the incidence of rain height and the effects on global satellite telecommunications

Satellite communications using millimetre waves, in Ka band and above, experience significant fading by rain. Strong attenuation is experienced between the ground station and a level known as the rain height, in ITU-R recommendations assumed to be 360 m above the zero-degree isotherm (ZDI). This paper examines NOAA NCEP/NCAR Reanalysis 1 data to identify changes in the ZDI height over the last 30 years. Near the equator and the poles the ZDI height has been approximately stable over this period. However, in mid-latitudes, different regions show trends of increasing or decreasing ZDI height. Over the economically important regions of North America, China and Western Europe, the ZDI height has shown an increasing trend with peak rates in the range of 8 to 10 metres per year. Given a twenty-year life-time of a satellite system, this could lead to a 10 to 20% increase in fade intensity from a similar rain event. The effect will be compounded by increasing trends in the incidence of heavy rain recently identified in UK data. These trends will need to be considered when designing new systems

Wind tunnel test results of a new leading edge flap design for highly swept wings, a vortex flap

A leading edge flap design for highly swept wings, called a vortex flap, was tested on an arrow wing model in a low speed wind tunnel. A vortex flap differs from a conventional plain flap in that it has a leading edge tab which is counterdeflected from the main portion of the flap. This results in intentional separation at the flap leading edge, causing a vortex to form and lie on the flap. By trapping this vortex, the vortex flap can result in significantly improved wing flow characteristics relative to conventional flaps at moderate to high angles of attack, as demonstrated by the flow visualization results of this tests

Planetary geometry handbook: Mars positional data, 1990 - 2020, volume 3

Graphical data necessary for the analysis of planetary exploration missions to Mars are presented. Positional and geometric information spanning the time period from 1990 through 2020 is provided. The data and usage are explained

The Impact of State Fiscal Policy on States\u27 Resilience Entering the Great Recession

The U.S. economy entered the Great Recession in December 2007 and exited in June 2009. This national statistic obscures a wealth of state-level data shedding light on the policies and conditions that helped some states withstand that recessionary shock for a time. In this study, we used that state-level data in a parametric regression model, known as survival analysis, to estimate the effects that a state’s fiscal policy had on the timing of its entry into the Great Recession. Consistent with earlier, more general, studies focusing on economic growth, we found that taxes have the potential to hasten the start of a state’s recession, while expenditures could defer that event. However, not all types of taxes and expenditures were equivalent in terms of their effect on recessionary timing. Most notably, our results showed that corporate income taxes had a different timing effect than sales, property, and individual income taxes. In addition, although total expenditures tended to delay the Great Recession’s onset, relatively few individual expenditure types had a statistically-significant impact on recessionary timing. Overall, our results suggest that, while taxes likely increase a state’s recessionary risk and expenditures likely decrease it, that narrative is an oversimplification of the complex role played by fiscal policy in determining a state\u27s ability to resist a negative economic shock like the Great Recession

Vascular Depression: An Early Warning Sign of Frailty

Objectives: Frailty is a common geriatric disorder associated with ADL impairment, hospitalization, and death. Phenomenological evidence suggests that late-life depression (Katz, 2004), particularly vascular depression, may be a risk factor for frailty. This study tests that hypothesis. Methods: We identified a sample of stroke-free women over the age of 80 from the Health and Retirement Survey. The sample included 984 respondents in 2000 (incidence sample). Of these, 459 were non-frail at baseline and still alive in 2004 (prevalence sample). Frail respondents experienced at least three of the following: wasting, exhaustion, weakness, slowness, and falls. Vascular depression was represented using two dummy variables. The first repre-sented respondents with either high CVB (at least two cerebrovascular risk factors) or probable depression (score ≥ 3 on the 8-item CES-D), and the second represented respondents with both high CVB and probable depression. Results: At baseline, the prevalence of frailty was 31.5%. Over 4 years the incidence of frailty was 31.8%. After controlling for age, education, ADL and IADL disability, arthritis, pulmonary disorders, cancer, and self-rated health, respondents with either high CVB or probable depression were more likely to be frail at baseline, and those with both were at even higher risk. Of those who were not frail at the 2000 wave, respondents who reported both high CVB and probable depression were more likely to become frail by 2004. Discussion: These findings suggest that vascular depression is a prodrome for frailty

Quantified Uncertainty in Thermodynamic Modeling for Materials Design

Phase fractions, compositions and energies of the stable phases as a function of macroscopic composition, temperature, and pressure (X-T-P) are the principle correlations needed for the design of new materials and improvement of existing materials. They are the outcomes of thermodynamic modeling based on the CALculation of PHAse Diagrams (CALPHAD) approach. The accuracy of CALPHAD predictions vary widely in X-T-P space due to experimental error, model inadequacy and unequal data coverage. In response, researchers have developed frameworks to quantify the uncertainty of thermodynamic property model parameters and propagate it to phase diagram predictions. In previous studies, uncertainty was represented as intervals on phase boundaries (with respect to composition) or invariant reactions (with respect to temperature) and was unable to represent the uncertainty in eutectoid reactions or in the stability of phase regions. In this work, we propose a suite of tools that leverages samples from the multivariate model parameter distribution to represent uncertainty in forms that surpass previous limitations and are well suited to materials design. These representations include the distribution of phase diagrams and their features, as well as the dependence of phase stability and the distributions of phase fraction, composition activity and Gibbs energy on X-T-P location - irrespective of the total number of components. Most critically, the new methodology allows the material designer to interrogate a certain composition and temperature domain and get in return the probability of different phases to be stable, which can positively impact materials design