96,890 research outputs found
Effects of lags on human operator transfer functions with head-coupled systems
No full textThe effects of operator learning and target velocity on head tracking performance with and without lags has been studied. Five lags (0, 40, 80, 120, 160 ms) between head movement and target image movement, and three target velocities (2, 3.5, 5° · s-1 r.m.s.) were investigated with eight male subjects and band-limited random target motions. Head tracking transfer functions, tracking error spectra, mean radial tracking error, and subjective difficulty ratings were obtained. Head tracking performance was significantly degraded by lags greater than, or equal to, 40 ms (in addition to a system lag of 40 ms). Both the input-correlated tracking error and the uncorrelated tracking error increased with increasing lag. No significant improvement in head tracking performance was found through practice with an 80-ms lag. As the lag increased, operators increased their gains at frequencies above about 0.5 Hz and reduced their phase lags at low frequencies (about 0.1 Hz) but failed to fully compensate for the increased display lag. The increased human operator gain was associated with increased operator phase lag at higher frequencies (above 0.5 Hz). To improve head tracking performance in the presence of lags, a lag compensation technique is needed to prevent undesirable changes in tracking strategy.</p
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Environmental impact of technology policy: R&D Subsidies versus R&D cooperation.
No full textIn this paper we study a neglected aspect ofteclmology policy, namely the adverse impact it might have on the envirol1Il1ent through increased production when R&D expenditure leads to cost reduction. Although teclmology policy measures that encourage finns to reduce their production costs would usually reduce energy inputs and therefore generate less pollution per unit of output production, we explore here the case where with reorganisation of production output gene rally increases. So even if per unit of production pollution is less, total pollution generated by the increased production induced by the innovative efforts of films increases. In this context it is therefore necessary to address the issue of tying-in teclmology and environmental policy, which is the issue we raise in this paper. We show that, irrespective of whether teclmology policy takes the fonn of R&D subsidies or R&D cooperation, R&D would gene rally lead to increased pollution and thus have a negative impact on the environment. Policies that might be optimal in the absence of concem for the enviroJUllent ceas e to be so. We claim that not only is a comparison between policy instruments more delicate but the optimal R&D subsidy might be negative. FinalIy, we propose and evaluate a speeific poliey in the form of a targeted subsidy tied-in to abatement activities and show that it is welfare improving.Technology policy; Process innovation; Pollution; R&D cooperation; R&D subsides;
Exploring the Relationship Between R&D and Productivity: A Country-Level Study
No full textResearch and development (R&D) has been considered a source of growth in productivity starting from Schultz (1953). Since then, significant research has studied this relationship at the firm, industry and country level. However, at the country level, most of the empirical studies assessing the R&D-productivity relationship often fail to consider the possible simultaneity of these variables. Do more productive countries invest more on R&D or does the higher level of R&D investment that leads to higher levels of productivity? Do both relationships occur at the same time? Using a 65-country panel for the time period of 1960- 2000, this study provides evidence that the relationship is mainly based on investment in R&D and not the reverse. In addition, we found that per capita R&D expenditure is strongly exogenous to productivity. These results suggest that, on average, those countries making the most effort in the R&D sector will be more productive in the future. Finally, we present evidence those points out a strong relationship between R&D and productivity in terms of both magnitude and significance.
Interference between stationary and vibrating cylinder wakes
No full textAuthor name used in this publication: Y. ZhouAuthor name used in this publication: R. M. C. So2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe
International Schumpeterian Competition and Optimal R&D subsidies
No full textThis paper studies the welfare effects of international competition in the market for innovations, and analyzes how competition affects the costs and the benefits of cooperative and non-cooperative R&D subsidies. I set up a two-country quality-ladder growth model where the leader, the home country, has R&D firms innovating in all sectors of the economy, and the follower, the foreign country, shows innovating firms only in a subset of industries. The measure of the set of sectors where R&D workers from both countries compete for innovation determines the scale of international Schumpeterian competition. Both governments engage in a strategic R&D subsidy game and respond optimally to changes in competition. For a given level of subsidies, increases in foreign competition raise the quality of goods available (growth effect) and lowers domestic profits (business-stealing effect); the overall effect of competition on domestic welfare depends on the relative strength of these two counteracting forces. When governments play a strategic subsidy game, increases in foreign competition trigger a defensive innovation policy mechanism that raises the optimal domestic R&D subsidy. Cooperation in subsidies leads both countries to set higher subsidies. Finally, while cooperation is beneficial for the global economy, there exists a threshold level of competition below which the home country experiences welfare losses under cooperation.international competition, endogenous technical change, growth theory, strategic R&D subsidies, international policy cooperation
International Competition and U.S. R&D Subsidies: A Quantitative Welfare Analysis
No full textThe geographical distribution of R&D investment changes dramatically in the 1970s and 1980s. In the early 1970s U.S. firms are the uncontested world leaders in R&D investment in most manufacturing sectors. Later, led by Japan and Europe, foreign firms start challenging American R&D leadership in many sectors of the economy. In this period of increasing competition we also observe a substantial increase in the U.S. R&D subsidy. In a version of the multi-country quality ladder growth model I study the effects of foreign R&D competition on domestic welfare and on the optimal R&D subsidy. I build a new empirical index of international R&D rivalry that can be used to perform quantitative analysis in this type of frameworks. In a calibrated version of the model I focus on the period 1979-1991 and perform the following quantitative exercises: first, I evaluate the quantitative effects of the observed increase in foreign R&D competition on U.S. welfare. I find that the positive growth effect and the negative business-stealing effect of foreign competition on U.S. welfare substantially balance each other, and the overall welfare effect of competition is negligible - less then 1 percent of per-capita consumption. Moreover, using estimates of the effective U.S. R&D subsidy rate, I compute the distance from optimality of the observed subsidy at each level of competition. I find that international competition increases the optimal subsidy and that, surprisingly, the U.S. subsidy observed in the data is fairly close to the optimal subsidy.international competition, R&D-driven growth theory, strategic R&D policy, international trade and growth
Connected subgroups of SO(2,n) acting irreducibly on R^{2,n}
No full textWe classify all connected subgroups of SO(2, n) that act irreducibly on R^{2, n
Multistability in a prion replication interconnected cell reaction network
No full text2 pages, 1 tables, 2 figuresAggregation of misfolded proteins has been implicated in a number of neurodegenerative disorders including prion disease. In spite of intensive research, the detailed mechanisms of protein misfolding leading to protein aggregation remain unsolved. Here, we explore the capacity for bistability of several classes of mechanisms proposed in the literature and compatible with protein aggregation kinetic data sets (it has been shown that bistability explains thresholds phenomena observed in protein aggregation in vitro and in vivo). Using a novel method for bistability detection we find a plausible scenario for which the so called subsequent monomer addition model leads to bistabilityFirst author acknowledge the financial support from Red de Proteínas, Priones y Enfermedades Neurodegenerativas (PRyEND) http://www.pryend.org/ IOM Acknowledges funding from the Spanish MINECO (and the European Regional Development Fund) project SYNBIOFACTORY (grant number DPI2014-55276-C5-2-R)Peer reviewe
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