Fatigue failure load indicator

An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test is described. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time the specimen is subjected to a compression load, means are provided for applying a positive voltage to the rest of the peak detector to reset it. During the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are provided for disconnecting the load cell from the peak detector when there is a failure in the specimen

High power phase locked laser oscillators

The feasibility of mechanizing an adaptive array of independent laser oscillators for generation of a high power coherent output was experimentally investigated. Tests were structured to evaluate component/system requirements for delivery of energy to a low-earth orbit satellite. Initial experiments addressed the control issues of phase locking unstable resonators at low power levels. A successful phase lock demonstration formed the basis for the design and fabrication of the high power, water-cooled, control mirror subsequently installed in the NASA LeRC high power laser. Tests were performed to characterize the operational limits of the laser system and included quantitative assessment of the frequency stability, noise sources, and optical properties of the beam

BEYOND THE MODEL SPECIFICATION PROBLEM: MODEL AND PARAMETER AVERAGING USING BAYESIAN TECHNIQUES

The model specification problem is perhaps the Achilles heel of applied econometrics. Rather than test down to a single model as is usually done, we estimate 72 different demand systems and use Bayesian averaging procedures over all 72 systems to generate meta estimates of the parameters (e.g., elasticities) of interest.Research Methods/ Statistical Methods,

TWO-STAGE UTILITY MAXIMIZATION AND IMPORT DEMAND SYSTEMS REVISITED: LIMITATIONS AND AN ALTERNATIVE

Two-stage utility maximization theory has been widely used in the literature to estimate import demand for agricultural commodities that are often inputs. This article examines the overlooked conceptual and empirical limitations of applying two-stage utility maximization theory to model the demand for imported commodities that are inputs. A discussion is presented about how the underutilized theory of two-stage profit maximization overcomes these limitations. Also discussed are the conditions under which errors illustration of the two-stage profit maximization procedure is provided.Demand and Price Analysis, International Relations/Trade,

AN ANALYSIS OF EXPORT MARKET STRATEGIES AND BARRIERS PERCEPTIONS BY U.S. AGRICULTURAL HVP EXPORTERS

This study identifies barriers perceived by agricultural exporters and examines how these perceptions influence use of export market strategies. Ordered logit models are used to estimate effects of perceived barriers and firm characteristics on export market strategies. The results from these models show that perceptions about import restrictions influence use of diversification of exports across products, competition influences use of competitive export pricing, and overseas product regulations affect product adaptation for export markets.International Relations/Trade,