Low solar absorptance and emittance surfaces utilizing vacuum deposited techniques Final report, 1 Jun. 1967 - 25 Mar. 1968

Optical properties and stability of vacuum deposited silver and dielectric film coating

Developing integrated parametric planning models for budgeting and managing complex projects

The applicability of integrated parametric models for the budgeting and management of complex projects is investigated. Methods for building a very flexible, interactive prototype for a project planning system, and software resources available for this purpose, are discussed and evaluated. The prototype is required to be sensitive to changing objectives, changing target dates, changing costs relationships, and changing budget constraints. To achieve the integration of costs and project and task durations, parametric cost functions are defined by a process of trapezoidal segmentation, where the total cost for the project is the sum of the various project cost segments, and each project cost segment is the integral of a linearly segmented cost loading function over a specific interval. The cost can thus be expressed algebraically. The prototype was designed using Lotus-123 as the primary software tool. This prototype implements a methodology for interactive project scheduling that provides a model of a system that meets most of the goals for the first phase of the study and some of the goals for the second phase

Experimental measurement of the dynamic pressure distribution in a squeeze film bearing damper executing circular centered orbits

A review of previous experimental measurements of squeeze film damper (SFD) forces is given. Measurements by the authors of SFD pressure fields and force coefficients, for circular centered orbits with epsilon = 0.5, are described and compared with computer predictions. For Reynolds numbers over the range 2-6, the effect of fluid inertia on the pressure fields and forces is found to be significant

Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 1: Fully Open Ended Configuration

Measurements of pressure distributions and force coefficients were carried out in two types of squeeze film dampers, executing a circular centered orbit, an open-ended configuration, and a partially sealed one, in order to investigate the effect of fluid inertia and cavitation on pressure distributions and force coefficients. Dynamic pressure measurements were carried out for two orbit radii, epsilon 0.5 and 0.8. It was found that the partially sealed configuration was less influenced by fluid inertia than the open ended configuration

Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 2: Partially Sealed Configuration

Experimental results from a partially sealed squeeze film damper (SFD) test rig, executing a circular centered orbit are presented and discussed. A serrated piston ring is installed at the damper exit. This device involves a new sealing concept which produces high damping values while allowing for oil flow to cool the damper. In the partially sealed damper, large cavitation regions are observed in the pressure fields at orbit radii epsilon equals 0.5 and epsilon equals 0.8. The cavitated pressure distributions and the corresponding force coefficients are compared with a cavitated bearing solution. The experimental results show the significance of fluid inertia and vapor cavitation in the operation of squeeze film dampers. Squeeze film Reynolds numbers tested reach up to Re equals 50, spanning the range of contemporary applications

TIME SERIES ANALYSIS OF SATELLITE DATA: DEFORESTATION IN SOUTHERN MEXICO

Tropical deforestation is significant to a range of themes that have relevance for the study of environmental change and economic development, including global warming, land degradation, species extinction, and sustainability issues. Recognition that both the location and pattern of forest clearance are often as important as its magnitude has motivated an increasing number of econometric studies that link satellite data and government census data with the aim of modeling the spatial dimensions of deforestation processes. Initial research focused on time series analysis, while recent work has started developing models that make use of time series data on land use. In this paper, we use satellite data from three dates over an approximate 15-year period to estimate the probability of a satellite pixel being in a forested or human-disturbed state. Our study focuses on land-use change in an agricultural frontier spanning the southern Mexican states of Campeche and Quintana Roo. This region contains one of the largest and oldest expanses of tropical forests in the Americas outside of Amazonia and has been identified as a "hot spot" of forest and biotic diversity loss. Over the past 30 years, these forests have been under sustained pressure following the construction of a highway in 1972 that opened the frontier to settlement. The road was part of a larger development effort to promote agricultural colonization and has contributed to a prolonged period of land transformation that has been captured by Thematic Mapper (TM) satellite imagery. We capture these landscape dynamics by assembling a spatial database that links the pixels from three TM images spanning the years 1986-1997 and other spatial environmental and GIS-location derived data with government census socio-economic data of data. We develop a simple utility-maximizing model of the forest clearance decision. Based on previous research, the theoretical model suggests many possible determinants of forest clearance in an economic environment characterized by missing or thin markets, as typifies frontier regions in the nascent stages of economic development. We subsequently test the significance of these determinants using discrete choice analysis These modeling questions have particular relevance for informing carbon sequestration and global warming policy initiatives. Other on-going research conducted by the ecologists associated with the project focus on the species composition, abundance, structure, and re-growth of the different forests types in the region. In addition, litter and biomass studies have been completed which included carbon estimates for the different forest types, including forest re-growth on agricultural land, as function of fallow cycle dynamics. Fallow cycle dynamics are extremely important as the region is dominated by semi-subsistence agriculture with very little chemical inputs, so farmers depend on the fallow cycle to restore soil productivity. It will be these detailed data that will be used to calculate baseline carbon sequestration amounts.Resource /Energy Economics and Policy,

The control of space manipulators subject to spacecraft attitude control saturation limits

The motions of robotic manipulators mounted on spacecraft can disturb the spacecraft's positions and attitude. These disturbances can surpass the ability of the system's attitude control reaction jets to control them, for the disturbances increase as manipulator speeds increase. If the manipulator moves too quickly the resulting disturbances can exceed the saturation levels of the reaction jets, causing excessive spacecraft motions. A method for planning space manipulator's motions is presented, so that tasks can be performed as quickly as possible without saturating the system's attitude control jets