9,989 research outputs found

    PERFORMANCE EVALUATION OF THE U.S. HOG SLAUGHTER INDUSTRY

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    Conventional wisdom holds that a small and decreasing number of hog slaughter firms are using their "market power" to take advantage of U.S. hog producers. Existing studies have simply calculated industry concentration ratios and assumed/asserted that the performance of such a concentrated industry must be different from the performance of a perfectly competitive industry. These researchers have rejected without testing the hypothesis that: the observed performance of the U.S. hog slaughter industry is not different from the performance that would be generated by a perfectly competitive industry. This paper derives the theoretical relationships between hog and pork prices, and hence the farm-wholesale price spread, that would exist in a perfectly competitive slaughter hog market. These performance norms are then confronted with observed weekly price/quantity relationships over the 1991-2001 period to compare observed market performance with the ideal performance norms derived from the economic theory of a perfectly competitive market. Based on the market performance measures derived from economic theory of a perfectly competitive market, the hypothesis that the U.S. hog slaughter hog market is a perfectly competitive market cannot be rejected. There simply is not any evidence to support allegations of abuse of market power by meat packers.Agribusiness, Industrial Organization, Livestock Production/Industries,

    A review of gender and sustainable land management: Implications for research and development

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    A Two-Process Model for Control of Legato Articulation Across a Wide Range of Tempos During Piano Performance

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    Prior reports indicated a non-linear increase in key overlap times (KOTs) as tempo slows for scales/arpeggios performed at internote intervals (INIs) of I00-1000 ms. Simulations illustrate that this function can be explained by a two-process model. An oscillating neural network based on dynamics of the vector-integration-to-endpoint model for central generation of voluntary actions, allows performers to compute an estimate of the time remaining before the oscillator's next cycle onset. At fixed successive threshold values of this estimate they first launch keystroke n+l and then lift keystroke n. As tempo slows, time required to pass between threshold crossings elongates, and KOT increases. If only this process prevailed, performers would produce longer than observed KOTs at the slowest tempo. The full data set is explicable if subjects lift keystroke n whenever they cross the second threshold or receive sensory feedback from stroke n+l, whichever comes earlier.Fulbright grant; Office of Naval Research (N00014-92-J-1309, N0014-95-1-0409

    Disunity in society, fractures at home: family relating in the context of divisive socio-political issues

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    Section A A systematic literature review conducted to identify and explore research that has investigated adult intrafamilial relationships and divisive political issues since 2016. Ten papers are included in the review. The studies are critiqued using a mixed-methods risk of bias tool. Findings are collated using narrative synthesis. The synthesis focuses on relational responses—to divisive political issues—the potential reasons for these responses, and their consequences. Review findings are discussed in relation to previous theoretical and empirical literature. Finally, clinical and research implications are presented. Section B A grounded theory study to develop an understanding of adult intrafamilial invalidation in the context of social and political change. Brexit and COVID-19 serve as the contextual lens through which the phenomenon was observed. Data from 11 participants and 45 screening questionnaire respondents were analysed as part of the study. A model of family “Rejection of You” experiences is presented outlining foundational and contextual factors that frame the experience, the experience itself, and relational, behavioural, cognitive, and emotional consequences. Findings are discussed in relation to previous theory and previous empirical research. Clinical implications are considered and possible directions for future research are set out

    Prospects for computational steering of evolutionary computation

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    Currently, evolutionary computation (EC) typically takes place in batch mode: algorithms are run autonomously, with the user providing little or no intervention or guidance. Although it is rarely possible to specify in advance, on the basis of EC theory, the optimal evolutionary algorithm for a particular problem, it seems likely that experienced EC practitioners possess considerable tacit knowledge of how evolutionary algorithms work. In situations such as this, computational steering (ongoing, informed user intervention in the execution of an otherwise autonomous computational process) has been profitably exploited to improve performance and generate insights into computational processes. In this short paper, prospects for the computational steering of evolutionary computation are assessed, and a prototype example of computational steering applied to a coevolutionary algorithm is presented

    Development in a biologically inspired spinal neural network for movement control

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    In two phases, we develop neural network models of spinal circuitry which self-organises into networks with opponent channels for the control of an antagonistic muscle pair. The self-organisation is enabled by spontaneous activity present in the spinal cord. We show that after the process of self-organisation, the networks have developed the possibility to independently control the length and tension of the innerated muscles. This allows the specification of joint angle independent from the specification of joint stiffness. The first network comprises only motorneurons and inhibitory interneurons through which the two channels interact. The inhibitory interneurons prevent saturation of the motorneuron pools, which is a necessary condition for independent control. In the second network, however, the neurons in the motorneuron pools obey the size-principle, which is a threat to the desired invariance of joint angle for varying joint stiffness, because of the different amplification of inputs in the case these inputs are not equal. To restore the desired invariance the second network ha.s been expanded with Renshaw cells. The manner in which they are included in the circuitry corrects the problem caused by the addition of the size-principle. The results obtained from the two models compare favourably with the FLETE-model for spinal circuitry (Bullock & Grossberg, 1991; Bullock et al., HJ93; Bullock & Contreras-Vidal, 1993) which has been successful in explaining several phenomena related to motor control.Fulbright Scholarship; Office of Naval Research (N00014-92-J-1309, N00014-95-1-0409
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