Ergodicity, Decisions, and Partial Information

In the simplest sequential decision problem for an ergodic stochastic process X, at each time n a decision u_n is made as a function of past observations X_0,...,X_{n-1}, and a loss l(u_n,X_n) is incurred. In this setting, it is known that one may choose (under a mild integrability assumption) a decision strategy whose pathwise time-average loss is asymptotically smaller than that of any other strategy. The corresponding problem in the case of partial information proves to be much more delicate, however: if the process X is not observable, but decisions must be based on the observation of a different process Y, the existence of pathwise optimal strategies is not guaranteed. The aim of this paper is to exhibit connections between pathwise optimal strategies and notions from ergodic theory. The sequential decision problem is developed in the general setting of an ergodic dynamical system (\Omega,B,P,T) with partial information Y\subseteq B. The existence of pathwise optimal strategies grounded in two basic properties: the conditional ergodic theory of the dynamical system, and the complexity of the loss function. When the loss function is not too complex, a general sufficient condition for the existence of pathwise optimal strategies is that the dynamical system is a conditional K-automorphism relative to the past observations \bigvee_n T^n Y. If the conditional ergodicity assumption is strengthened, the complexity assumption can be weakened. Several examples demonstrate the interplay between complexity and ergodicity, which does not arise in the case of full information. Our results also yield a decision-theoretic characterization of weak mixing in ergodic theory, and establish pathwise optimality of ergodic nonlinear filters.Comment: 45 page

The influence of farmers' mental models on an agroforestry extension program in the Philippines

The influence of farmers' mental models on the success of an agroforestry extension program on Leyte Island in the Philippines was investigated. Knowledge of farmers' mental models and hence the likely acceptance of technology was used to inform the design of a hypothetically expanded program. To gain an insight into the reasons behind differing acceptance of extension assistance, data were collected and analysed from formal interviews, translated conversations and visual observations. The data provided a chain of evidence and triangulation between farmers' stated intentions and their actions. Farmers had little prior knowledge of nursery technology and were highly receptive to extension assistance which enabled them to develop high self-efficacy in seedling production. However, farmers' rejection of silvicultural advice to thin and prune existing plantations was predicated by existing attitudes to forest resource management. Farmers also expressed a strong preference for a low-cost and low-input approach to establishing timber trees. Visual observations of farmers' tree establishment practices indicated the existence of gaps in their knowledge of tree growth processes. This investigation illustrates the need to elicit farmers' mental models as a parallel enquiry to extension activities. If agroforestry extension is to be constructivist and participatory, accommodation of farmers' mental models and modification of program goals may be necessary. Relatively little is known about the reasons for farmers' acceptance or rejection of silviculture in Leyte and these results indicate that further research into the way that farmers' mental models filter and guide acceptance of advice may be worthwhile

Potential of a multiparametric optical sensor for determining in situ the maturity components of red and white vitis vinifera wine grapes

A non-destructive fluorescence-based technique for evaluating Vitis vinifera L. grape maturity using a portable sensor (Multiplex ®) is presented. It provides indices of anthocyanins and chlorophyll in Cabernet Sauvignon, Merlot and Sangiovese red grapes and of flavonols and chlorophyll in Vermentino white grapes. The good exponential relationship between the anthocyanin index and the actual anthocyanin content determined by wet chemistry was used to estimate grape anthocyanins from in field sensor data during ripening. Marked differences were found in the kinetics and the amount of anthocyanins between cultivars and between seasons. A sensor-driven mapping of the anthocyanin content in the grapes, expressed as g/kg fresh weight, was performed on a 7-ha vineyard planted with Sangiovese. In the Vermentino, the flavonol index was favorably correlated to the actual content of berry skin flavonols determined by means of HPLC analysis of skin extracts. It was used to make a non-destructive estimate of the evolution in the flavonol concentration in grape berry samplings. The chlorophyll index was inversely correlated in linear manner to the total soluble solids (°Brix): it could, therefore, be used as a new index of technological maturity. The fluorescence sensor (Multiplex) possesses a high potential for representing an important innovative tool for controlling grape maturity in precision viticulture

Urban Health: Evidence, Challenges, and Directions

Urbanization is one of the most important demographic shifts worldwide during the past century and represents a substantial change from how most of the world’s population has lived for the past several thousand years. The study of urban health considers how characteristics of the urban environment may affect population health. This paper reviews the empirical research assessing urban living’s impact on population health and our rationale for considering the study of urban health as a distinct field of inquiry. The key factors affecting health in cities can be considered within three broad themes: the physical environment, the social environment, and access to health and social services. The methodologic and conceptual challenges facing the study of urban health, arising both from the limitations of the research to date and from the complexities inherent in assessing the relations among complex urban systems, disease causation, and health are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/40323/2/Galea_Urban Health - Evidence, Challenges, and Directions_2005.pd

“Dance and Abstraction” Special Issue Introduction

In his 2013 book Hating Empire Properly, historian Sunil Agnani helpfully reminds his audience that an emphasis on cultural difference—a perspective that we tend to think of as the postmodern antidote to Enlightenment-era universalizing rhetoric—can in fact be traced back to early modern European thought [...

Comparison of Methods for Updating Census Based Estimates of Number of Farms to Non-Census Years

The National Agricultural Statistics Service (NASS) conducts the census of agriculture (a complete count of US farms and ranches) every five years. Sample surveys, including the June area survey (JAS), are carried out annually to obtain estimates of many of the same agricultural quantities as the census. Due to the large number of operators surveyed and the complete coverage provided by the census, its numbers are considered more accurate than those derived from the much smaller scale sample surveys. An interesting question is whether census figures for specific survey items can be used in conjunction with survey data to improve estimation accuracy for non-census years. Because of its relative stability over time, the survey item considered most likely to benefit from such an approach is number of farms in a state. Two proposed methods for projecting census counts of number of farms to subsequent non-census years are evaluated. The first method updates the census figure to the current year using JAS data only, while the second makes additional use of official NASS state level estimates of number of farms for the previous year (if it wasn’t a census year). The two methods are identical for the first post-census year. The proposed estimators are compared with area frame based and hybrid operational estimators for the years 2003-06 in a study covering most of the lower 48 states, both at the state level and within categories defined by farm value of sales. Variances are estimated using an extended delete-a-group jackknife method

Contained rocket motor burn demonstrations in X-tunnel: Final report for the DoD/DOE Joint Demilitarization Technology Program

Three low-pressure rocket motor propellant burn tests were performed in a large, sealed test chamber located at the X-tunnel complex on the Department of Energy's Nevada Test Site in the period May--June 1997. NIKE rocket motors containing double base propellant were used in two tests (two and four motors, respectively), and the third test used two improved HAWK rocket motors containing composite propellant. The preliminary containment safety calculations, the crack and burn procedures used in each test, and the results of various measurements made during and after each test are all summarized and collected in this document