Flat strips, Bowen-Margulis measures, and mixing of the geodesic flow for rank one CAT(0) spaces

Let $X$ be a proper, geodesically complete CAT(0) space under a proper, non-elementary, isometric action by a group $\Gamma$ with a rank one element. We construct a generalized Bowen-Margulis measure on the space of unit-speed parametrized geodesics of $X$ modulo the $\Gamma$-action. Although the construction of Bowen-Margulis measures for rank one nonpositively curved manifolds and for CAT(-1) spaces is well-known, the construction for CAT(0) spaces hinges on establishing a new structural result of independent interest: Almost no geodesic, under the Bowen-Margulis measure, bounds a flat strip of any positive width. We also show that almost every point in $\partial_\infty X$, under the Patterson-Sullivan measure, is isolated in the Tits metric. (For these results we assume the Bowen-Margulis measure is finite, as it is in the cocompact case). Finally, we precisely characterize mixing when $X$ has full limit set: A finite Bowen-Margulis measure is not mixing under the geodesic flow precisely when $X$ is a tree with all edge lengths in $c \mathbb Z$ for some $c > 0$. This characterization is new, even in the setting of CAT(-1) spaces. More general (technical) versions of these results are also stated in the paper.Comment: v2: 26 pages, 1 figure. Theorems stated in much more generality (in particular, the cocompactness hypothesis was removed almost everywhere), also a number of proofs dropped. This is the July 2015 version that was accepted for publication in Ergodic Theory and Dynamical Systems. v1: 39 pages, 1 figur

The Strengths Perspective: Providing Opportunities for Teen Parents and their Families to Succeed

Majority of teen pregnancy literature and practice is deficit based, focusing on the consequences of teen pregnancy; significantly less research is devoted to the teens’ strengths. This article discusses the strengths-based perspective as a viable framework for clinicians and school social workers to implement to help teen parents and their families ameliorate some of the challenges they encounter. This article emphasizes the importance of clinicians, school social workers, and the community to adopt a strengths-based perspective when working with teen parents in order to cultivate strengths and opportunities for success. This article also provides specific strategies for practitioners to implement in order to identify and build strengths among teen parents and their families. An overview of the pivotal role academic institutions have in maximizing strengths through school-based services is also presented

Feasibility of using a knowledge-based system concept for in-flight primary flight display research

A study was conducted to determine the feasibility of using knowledge-based systems architectures for inflight research of primary flight display information management issues. The feasibility relied on the ability to integrate knowledge-based systems with existing onboard aircraft systems. And, given the hardware and software platforms available, the feasibility also depended on the ability to use interpreted LISP software with the real time operation of the primary flight display. In addition to evaluating these feasibility issues, the study determined whether the software engineering advantages of knowledge-based systems found for this application in the earlier workstation study extended to the inflight research environment. To study these issues, two integrated knowledge-based systems were designed to control the primary flight display according to pre-existing specifications of an ongoing primary flight display information management research effort. These two systems were implemented to assess the feasibility and software engineering issues listed. Flight test results were successful in showing the feasibility of using knowledge-based systems inflight with actual aircraft data

SOC-DS computer code provides tool for design evaluation of homogeneous two-material nuclear shield

SOC-DS Code /Shield Optimization Code-Direc Search/, selects a nuclear shield material of optimum volume, weight, or cost to meet the requirments of a given radiation dose rate or energy transmission constraint. It is applicable to evaluating neutron and gamma ray shields for all nuclear reactors

Computer program calculates gamma ray source strengths of materials exposed to neutron fluxes

Computer program contains an input library of nuclear data for 44 elements and their isotopes to determine the induced radioactivity for gamma emitters. Minimum input requires the irradiation history of the element, a four-energy-group neutron flux, specification of an alloy composition by elements, and selection of the output

Design of a variable-focal-length optical system

Requirements to place an entire optical system with a variable focal length ranging from 20 to 200 cm within a overall length somewhat less than 100 cm placed severe restrictions on the design of a zoom lens suitable for use on a comet explorer. The requirements of a wavelength range of 0.4 to 1.0 microns produced even greater limitations on the possibilities for a design that included a catadioptric (using mirrors and glass) front and followed by a zooming refractive portion. Capabilities available commercial zoom lenses as well as patents of optical systems are reviewed. Preliminary designs of the refractive optics zoom lens and the catadioptric system are presented and evaluated. Of the two, the latter probably has the best chance of success, so long as the shortest focal lengths are not really needed

FOCUS GROUPS AS A USEFUL APPROACH TO AGRIBUSINESS RESEARCH

As the agricultural economics profession increasingly strives to find relevant and useful approaches for addressing a broad array of research questions, particularly in terms of agribusiness research, there will be a growing need to adopt a wide set of research methods and methodologies. Historical research strategies typically emphasized by agricultural economists have focused primarily on surveys, archival/secondary data and econometrics. However, these approaches are, at times, limited in their applicability and scope relative to some of the research questions that have the greatest priority for agribusiness researchers and their clientele. Some of the research methods now being more widely used by agribusiness-oriented agricultural economists are more qualitative, as is already evident with a growing acceptance of case studies within the profession. This paper discusses an additional qualitative approach that has substantial potential for agribusiness research focus groups.Agribusiness, Research Methods/ Statistical Methods,

SHOULD IMPORTS FREE-RIDE OR HELP PAY-- DECISIONS ABOUT GENERIC PROMOTION PROGRAMS FOR AGRICULTURAL COMMODITIES

Many U.S. agricultural commodity industries are currently considering if and how they might implement a mandatory national generic promotion program. As U.S. industries consider how to finance these programs, one of the key decisions they face is the choice to include or exempt imported products from promotional assessment fees. Free-riders, unwilling riders, exclusion costs, economies of scale, market share, seasonality of production, storage constraints, and the role of government are reviewed within the context of this choice. The paper concludes that perceptions of fairness and ownership of decision processes, commonly held objectives, and effective communication links are key factors affecting decisions about the structures of generic commodity promotion programs.Marketing,

STRATEGIC PLANNING FOR IMPROVED COMPETITIVENESS BY REGIONAL COMMODITY INDUSTRIES

Agribusiness,

Traditional versus rule-based programming techniques: Application to the control of optional flight information

To the software design community, the concern over the costs associated with a program's execution time and implementation is great. It is always desirable, and sometimes imperative, that the proper programming technique is chosen which minimizes all costs for a given application or type of application. A study is described that compared cost-related factors associated with traditional programming techniques to rule-based programming techniques for a specific application. The results of this study favored the traditional approach regarding execution efficiency, but favored the rule-based approach regarding programmer productivity (implementation ease). Although this study examined a specific application, the results should be widely applicable