825 research outputs found

    The Determinants of Labor Market Institutions: A Panel Data Study

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    This paper analyzes the argument that labor market institutions can be thought of devices for social insurance. It investigates the hypotheses that a country’s exposure to external risk and ethnic fractionalization are correlated with labor market institutions. Extreme bounds analysis with the panel data of 40 years indicates that there is no robust evidence of positive correlation between external risk and the structure of labor market institutions, while ethnic fractionalization is robust negatively correlated with the institutions.labor market institutions; external risk; ethnic fractionalization; extreme bounds analysis

    Why do Some Studies Show that Generous Unemployment Benefits Increase Unemployment Rates? A Meta-Analysis of Cross-Country Studies

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    This paper investigates the hypothesis that generous unemployment benefits give rise to high levels of unemployment by systematically reviewing 34 cross- country studies. In contrast to conventional literature surveys, I perform a meta-analysis which applies regression techniques to a set of results taken from the existing literature. The main finding is that the choice of the primary data and estimation method matter for the final outcome. The control variables in the primary studies also affect the results.meta-analysis; cross-country study; unemployment; benefits replacement rate; benefit duration

    The Impact of Education and R&D Investment on Regional Economic Growth

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    The purpose of this paper is to examine the impact of education and R&D investment on regional economic growth in South Korea. We develop a simultaneous model of production, human capital accumulation, migration, population and physical capital investment of two regions: the Seoul Metropolitan Area and the rest of Korea. We decompose the regional growth path into a quality path and a quantity path to identify how regional economies grow and run simulations to evaluate alternative policies in terms of effectiveness and adaptability. The impact of education and R&D investment on regional growth in the rest of Korea is only 22.3% of that in the Seoul Metropolitan Area due to lower elasticity values of young in-migrants with respect to the investment in the rest of Korea. An enhanced efficiency of regional human capital accumulation is effective and adaptable to alleviate regional economic disparity

    Asymptotic Symmetries of Colored Gravity in Three Dimensions

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    Three-dimensional colored gravity refers to nonabelian isospin extension of Einstein gravity. We investigate the asymptotic symmetry algebra of the SU(N)SU(N)-colored gravity in (2+1)-dimensional anti-de Sitter spacetime. Formulated by the Chern-Simons theory with SU(N,N)×SU(N,N)SU(N,N)\times SU(N,N) gauge group, the theory contains graviton, SU(N)SU(N) Chern-Simons gauge fields and massless spin-two multiplets in the SU(N)SU(N) adjoint representation, thus extending diffeomorphism to colored, nonabelian counterpart. We identify the asymptotic symmetry as Poisson algebra of generators associated with the residual global symmetries of the nonabelian diffeomorphism set by appropriately chosen boundary conditions. The resulting asymptotic symmetry algebra is a nonlinear extension of Virasoro algeba and su(N)^\widehat{\mathfrak{su}(N)} Kac-Moody algebra, supplemented by additional generators corresponding to the massless spin-two adjoint matter fields.Comment: 22 pages, published version in JHE

    Improving the biological control of Persicaria perfoliata (Polygonaceae) using Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae)

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    Persicaria perfoliata (L.) H. Gross (Polygonaceae; Mile-a-minute weed) is a rapid-growing invasive vine introduced from eastern Asia to northeastern United States in the 1930s. This vine has been invaded in disturbed areas and reforestation sites in 15 states in the U.S. and forms dense, monocultural patches that may inhibit natural forest regeneration. To control this weed, a host-specific biocontrol agent, Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) has been released in the P. perfoliata invaded states in the U.S. during the past 15 years. Currently, R. latipes is released by hand to the invaded area where the presence of the weed is readily detected. However, the hand-release method is not applicable to weed patches located in hard-to-access areas. Moreover, successful management of a target invasive species using biocontrol and/or other methods may not lead to recovery of native species. Understanding the plant composition of invaded sites prior to management may prevent invasion of other exotic weeds currently present in lower abundance. This study was conducted to improve weed management of P. perfoliata using UAS for spatially-targeted release of R. latipes on P. perfoliata patches in hard-to-access areas and to evaluate the plant species composition of invaded sites to determine likely species assemblies and successional trajectories after removal of P. perfoliata. First, we developed a spatially-targeted biocontrol strategy by using an unmanned aircraft system (UAS) for the detection of P. perfoliata and release of R. latipes. A rotary wing UAS was flown at 15 different altitudes to determine the detectability of P. perfoliata patches and, the presence of P. perfoliata was confirmed by a ground survey. In addition, we developed a new insect-release system that would be environmentally-friendly and easy to handle in the field. The release system that housed R. latipes for aerial release was 3-D printed with biodegradable polyvinyl alcohol (PVA), and tests were conducted to determine the ability of R. latipes to escape the pod and assess their post-release mortality and feeding ability of R. latipes. Persicaria perfoliata patches were readily detectable on the aerial images taken at ≤ 15-m flight altitudes. More than 98% of R. latipes (n = 118) successfully escaped from the release system within 24 hours after aerial deployment. There were no significant (P \u3e 0.05) effects of PVA exposure on the mortality and feeding ability of R. latipes. Second, we conducted a plant community survey on P. perfoliata dominated sites. We compared the species composition of P. perfoliata-dominated (dominated) patches and adjacent patches where P. perfoliata was not dominant (not-dominated) within an environmentally homogeneous site infested with P. perfoliata. This study was conducted in two invaded sites (JS and RV) in southwestern Pennsylvania. The relative importance of all vascular plant species (combined cover and frequency values), richness, diversity, and evenness were determined for each plot type. Significant differences in species composition in the two plot types were determined using nonmetric multidimensional scaling and a multi-response permutation procedure. Indicator species within the plot types were also calculated. There were a total of 36 and 26 plant species from the JS and RV sites, respectively. The dominated plots had lower species diversity and richness than the nondominated plots. The species compositions between the two plot types differed significantly, though site differences were stronger. In addition, an exotic invader, Microstegium vimineum, and native weed, Ambrosia artemisiifolia, were the most important species in the nondominant plots in JS and RV sites, respectively. Those results of this study suggest that the comprehensive management including utilization of UAS as a site-specific deployment system of R. latipes and understanding potentially coexisting native and exotic plant species within the P. perfoliata invaded sites will help successful control of the target weed and restoration of invaded sites

    Design & Control of an Omni-Directional Quad-Rotor

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    Unmanned Aerial Vehicle (UAV) is an unmanned air vehicle which can be operated by human or fly autonomously on the basis of flight plans. UAVs are usually utilized for military purposes that are too tedious, dirty, risky, or hazardous for normal manned air vehicles; however, they are also utilized for civil purposes like aerial photography or air surveillance. There are two types of UAVs. One is the fixed-wing UAV, i.e. an airliner, the other is the rotor-wing UAV, i.e. a helicopter. Rotor-wing UAVs have the weather gauge of fixed-wing UAVs. Because they can perform Vertical Take-Off and Landing (VTOL); it is able to hover at particular point. The advantages of the rotor-wing is as follows. First, it is mechanically simple; its main components are n motors and n propellers. Second, they do not require complex mechanical parts to control their flight; it can fly and maneuver only by changing the speed of the motors. One of the successful design example is a four rotor UAV, also known as quadrotor. In this work, design and control of an omni-directional quadrotor model is developed and simulated by using tilt-rotor mechanism. And also, a mathematical model of the quadrotor’s dynamics is derived using Newton’s law and Euler’s law. In addition, linearized models are obtained, and therefore a linear controller, the Linear Quadratic Regulator (LQR), is derived. After that, non-linear controller for the quadrotor is provided. Finally, the behavior of the quadrotor under the proposed control strategies is observed in simulation by using the MATLAB, Simulink and Simmechanics