A two-telescope receiver design for deep space optical communications

A two-telescope system for a deep space optical communication receiver is proposed. To substantially improve the overall receiver efficiency, the design reserves the large telescope for signal-detection purposes only. A small diffraction-limited telescope is introduced to accomplish the task of navigational tracking

A preliminary weather model for optical communications through the atmosphere

A preliminary weather model is presented for optical propagation through the atmosphere. It can be used to compute the attenuation loss due to the atmosphere for desired link availability statistics. The quantitative results that can be obtained from this model provide good estimates for the atmospheric link budget necessary for the design of an optical communication system. The result is extended to provide for the computation of joint attenuation probability for n sites with uncorrelated weather patterns

Atmospheric propagation effects relevant to optical communications

A number of atmospheric phenomena affect the propagation of light. The effects of clear air turbulence are reviewed as well as atmospheric turbidity on optical communications. Among the phenomena considered are astronomical and random refraction, scintillation, beam broadening, spatial coherence, angle of arrival, aperture averaging, absorption and scattering, and the effect of opaque clouds. An extensive reference list is also provided for further study. Useful information on the atmospheric propagation of light in relation to optical deep space communications to an earth based receiving station is available, however, further data must be generated before such a link can be designed with committed performance

NON-PARAMETRIC ENVIRONMENTAL ADJUSTED PRODUCTIVITY (EAP) MEASURES: NEBRASKA AGRICULTURE SECTOR

Traditional Total factor productivity [TFP] misrepresents the true change in agricultural productivity because environmental bads jointly produced with desirable outputs are unaccounted. Nonparametric measures incorporating environmental bads support the hypothesis that prior [after] to 1980's the traditional TFP overstate [understate] production growths, reflecting peak use of chemicals.Environmental Economics and Policy, Productivity Analysis,

THE ROLE OF NON-PARAMETRIC APPROACH IN ADJUSTING PRODUCTIVITY MEASURES FOR ENVIRONMENTAL IMPACTS

This paper addresses the role of non-parametric analysis in adjusting agricultural productivity measures for environmental impacts. The modified Tornquist-Theil index computed using shadow prices derived from the programming procedures is compared and contrasted with a non-parametric hyperbolic graph productivity index for the case of Nebraska agriculture.Nonparametric, Shadow price, Productivity, Environmental Economics and Policy, Productivity Analysis,

Returns to Scale of Production Function: Pooled, Within and Between Quantile Regression Approach

Production function, Pooled, Between and Within Quantile Regression, Panel data, Production Economics, Research Methods/ Statistical Methods,

Do Farm Programs Explain Mean and Variance of Technical Efficiency? Stochastic Frontier Analysis

Past literature has examined the importance of farm programs on the volatility and returns on general and agriculture economic growth. The objective of this study was to assess the impact of farm program payments on technical efficiency. The study used aggregate state level panel data from the U.S agricultural sector. Results indicate production increasing with increasing units of inputs. Results from this study indicate that farm program payments play an important role in technical efficiency. For example, farm program payments indicate a negative and positive effect on mean and variance of technical efficiency in the long-run and short-run, respectivelyProduction Economics, Productivity Analysis, Risk and Uncertainty,

Aggregation Issues in the Estimation of Linear Programming Productivity Measures

This paper demonstrates the sensitivity of the linear programming approach in the estimation of productivity measures in the primal framework using Malmquist productivity index and Malmquist total factor productivity index models. Specifically, the sensitivity of productivity measure to the number of constraints (level of dis-aggregation) and imposition of returns to scale constraints of linear programing is evaluated. Further, the shadow or dual values are recovered from the linear program and compared to the market prices used in the ideal Fisher index approach to illustrate sensitivity. Empirical application to U.S. state-level time series data from 1960-2004 reveal productivity change decreases with increases in the number of constraints. Further, the input and output shadow or dual values are skewed, leading to the difference in the productivity measures due to aggregation.Aggregation, Share-weights, single and multiple output and input, Malmquist productivity index, Malmquist total factor productivity index, Agribusiness, Production Economics,

An Assessment of the Efficiency of Agribusiness Trucking Companies: A Data Envelopment Analysis Approach

The purpose of this study is to investigate the issue of efficiency in the U.S. motor carrier industry using DEA and SFA. While both methods used the same variables, the resulting efficiency scores were significantly different. This leads to the question of which method is a better measure of efficiency.Public Economics,

The Role of Non-parametric Approach in Adjusting Productivity Measures for Environmental Impacts

This paper addresses the role of non-parametric analysis in adjusting agricultural productivity measures for environmental impacts. The modified Tornquist-Theil index computed using shadow prices derived from the programming procedures is compared and contrasted with a nonparametric hyperbolic Malmquist index for the case of Nebraska agriculture