2,817 research outputs found

    Contour measurement system

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    A measurement system for measuring the departures from a straight line of discrete track sections of a track along a coal face in a mine employing a vehicle having a pair of spaced wheel assemblies which align with the track is presented. A reference arm pivotally connects between the wheel assemblies, and there is indicating means for measuring the angle of pivot between the arm and each of the wheel assemblies. The length of the device is less than the length of a track section, and thus when one of the wheel assemblies is on one track section and one is on an adjoining track section, the sum of the indicated angles will be indicative of the angle between track sections. Thus, from the length of a track section and angle, the departure of each track section from the line may be calculated

    Migration and return migration: A new look at the Eastern Kentucky migration stream

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    Most studies of the economics of migration have implicitly assumed that migratory streams are homogeneous. However, migratory streams from one region to another consist of two distinct streams: a stream of first-time migrants and a stream of return migrants moving back to their area of origin. In fact, a substantial proportion of all U.S. migration is return migration, 14 percent from 1955 to 1960 [15,p. 3]. Moreover, in states with histories of substantial out-migration, an even greater proportion of in-migrants are returnees, 35 .4 percent between 1955 and 1960. Yet, economists have largely ignored return migration in their attempts to explain changes in the labor force. Studies of return migration may have several important implications. If first-time migrants and return migrants have different characteristics, then studies which distinguish the two streams may provide more reliable insights into the determinants of migration. Comparison of the characteristics of return migrants with migrants who remain may provide guidance for the design of programs to facilitate successful migration. Knowledge of the causes and characteristics of return migration may provide additional understanding of the effects of migration on the communities of origin and destination

    The determinants of wage increases in new manufacturing plants in rural areas

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    The research reported here was designed to explain variation in wage changes of new industrial plant employees. Following the theoretical perspectives of Gotsch, wage changes were hypothesized to result from a combination of employee household, community, and plant characteristics. The greatest difficulty in this study was choosing appropriate operational measures for independent variables that were highly correlated with these theoretical factors.Southern journal of agricultural economics, July 1981, p. 84-88Includes bibliographical reference

    Location determinants of manufacturing industry in rural areas

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    The spatial distribution of economic activity has been the subject of much theoretical study during the last 150 years. The two-state study which provides primary evidence for this article is, to the authors' knowledge, the first attempt to analyze statistically the determinants of industrial location in rural communities with an explicit objective of more enlightened public action at the local, state, and federal levels

    Entry in the ADHD drugs market: Welfare impact of generics and me-toos

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    Recent decades have seen a growth in treatments for attention deficit hyperactivity disorder (ADHD) including many branded and generic drugs. In the early 2000's, new drug entry dramatically altered market shares. We estimate a demand system for ADHD drugs and assess the welfare impact of new drugs. We find that entry induced large welfare gains by reducing prices of substitute drugs, and by providing alternative delivery mechanisms for existing molecules. Our results suggest that the success of follow-on patented drugs may come from unanticipated innovations like delivery mechanisms, a factor ignored by proposals to retard new follow-on drug approvals

    Narrow-Band Hybrid Pulsed Laser/EMAT System for Non-Contact Ultrasonic Inspection Using Angled Shear Waves

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    Conventional ultrasonic testing (UT) using angled shear waves to locate and size potentially critical cracks and flaws in power generation and refinery equipment has become a widely utilized industrial tool. Because this technique uses piezoelectric transducers it requires intimate surface contact and fluid couplants. Therefore, conventional UT has the important drawback that it is difficult to use on surfaces at elevated temperature and, as a result, may require costly plant shut downs to implement. The development of non-contact techniques for angled shear wave UT would represent a significant improvement in the ability to test hot vessels and pipes
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