Radically solvable graphs

A 2-dimensional framework is a straight line realisation of a graph in the Euclidean plane. It is radically solvable if the set of vertex coordinates is contained in a radical extension of the field of rationals extended by the squared edge lengths. We show that the radical solvability of a generic framework depends only on its underlying graph and characterise which planar graphs give rise to radically solvable generic frameworks. We conjecture that our characterisation extends to all graphs

Dropped? Latino Education and Arizona's Economic Future

Describes persistent barriers to educational opportunities and the achievement gap Latinos face; implications for incomes, health insurance coverage, and the economy; and strategies for improving the educational system and Latino educational attainment

Thermal barrier coating system having improved adhesion

The adherence between a ceramic thermal barrier coating and a metal bond coating is improved by ion sputtering a ceramic film on the bond cost. A ceramic thermal barrier coating is then plasma-sprayed onto this primer film. This improves the integrity and strength of the interface between the plasma-sprayed ceramic layer and metallic bond coat which insures stronger adherence between the metal and the ceramic

INTERNAL CONSISTENCY IN MODELS OF OPTIMAL RESOURCE USE UNDER UNCERTAINTY

For several decades, economists have been concerned with the problem of optimal resource use under uncertainty. In many studies, researchers assume that prices evolve according to an exogenous stochastic process and solve the corresponding dynamic optimization problem to yield an optimal decision rule for exploitation of the resource. This study is motivated by our attempt to understand the relationship between efficiency in resource markets and optimal harvest decisions in which price is an exogenous state variable. The literature on optimal commodity storage finds that in a rational expectations equilibrium commodity prices are stationary and serially correlated. Yet recent papers on optimal timber harvesting that assume exogenous stationary prices generate harvest rules inconsistent with the price processes on which they are based. In this study, we investigate the appropriate form of the stochastic process governing prices of renewable resources. We develop a model in which timber is supplied by profit-maximizing managers with rational expectations and aggregate timber demand is subject to independent exogenous shocks. In contrast to earlier studies, prices are endogenously determined. Managers know the structure of the timber market and form expectations of future market equilibria in making optimal harvesting decisions. We show under general conditions that efficient timber prices are stationary and serially correlated. Stationarity and serial correlation are shown to arise from two sources: the occurrence of stock-outs (i.e., depletion of the inventory) and stock-dependent growth of the resource. Further, we show that prices retain these properties even in the absence of stock-outs. Simulations are used to further illustrate the analytical results. Our findings have implications for a large number of economic analyses of optimal resource use. First, our results reveal why extraction rules for renewable resources based on exogenous price specifications are internally inconsistent, even when the specification conforms to the stochastic behavior of prices generated by an efficient market. These prices arise in a particular structural environment, and if large numbers of resource managers adopt the harvesting rule, the underlying structural environment would change, and the price process would deviate from that used to derive the harvesting rule. Second, we show that there can be no gains from exploiting the stochasticity of resource prices in a rational expectations world, a finding that challenges the prescriptive policies for resource use found in many studies, including those on option values. Third, our results show that time-series analyses designed to test for the efficiency of renewable resource markets cannot distinguish prices generated in an efficient market from those generated in an inefficient market. Finally, we extend the literature on optimal storage. Previous models of commodity storage models are shown to be a special case of our model involving age-independent depreciation of the inventory.Resource /Energy Economics and Policy,

Advanced transmission studies

The NASA Lewis Research Center and the U.S. Army Aviation Systems Command share an interest in advancing the technology for helicopter propulsion systems. In particular, this paper presents highlights from that portion of the program in drive train technology and the related mechanical components. The major goals of the program are to increase the life, reliability, and maintainability; reduce the weight, noise, and vibration; and maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advanced configurations and new analytical tools. Finally, the plan for future transmission research is presented

The Prairie Post Quarterly Newsletter of the High Plains Regional Climate Center- July 2016

Inside this issue: Message from the interim director........................................1 Staff spotlight...........................1 Research update......................2 Product highlight....................3 Partnership spotlight.............3 AWDN information.................4 Update on regional climate conditions..................................4 Outreach/engagement.........5 Recent and upcoming travel and activities.............................

Effects of Environmental Zoning on Household Sorting: Empirical Evidence and Ecological Implications

In this paper we present a preliminary analysis of whether and how spatial variation in environmental attributes affects the residential sorting of households with heterogeneous preferences. An important implication of such sorting arises if variation in preferences over environmental attributes is correlated with household activities affecting the local ecosystem, such as the replacement of native vegetation with lawns, and the removal of course woody habitat from a lake. In this case the sorting process may engender differential evolution of local ecosystems (lakes) with the same initial ecological state. The model examined in the paper has the potential to statistically examine this issue, and therefore holds promise for understanding the behavioral implications of land use policies designed to protect local ecosystems. By facilitating the grouping of different types of households onto different lakes, for instance, lakeshore zoning policies may engender differentiation in the ecological evolution of lakes beyond what would be expected from the zoning policies themselves.Environmental Economics and Policy, Land Economics/Use,

The Prairie Post Quarterly Newsletter of the High Plains Regional Climate Center- January 2017

Inside this issue: Message from the interim director........................................1 30th anniversary......................1 Stakeholder engagement activities......................................2 Product highlights..................3 AWDN information.................4 Update on regional climate conditions..................................4 Services update........................5 Recent and upcoming travel and activities.............................