2,503 research outputs found

    The positive net radiative greenhouse gas forcing of increasing methane emissions from a thawing boreal forest-wetland landscape

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    At the southern margin of permafrost in North America, climate change causes widespread permafrost thaw. In boreal lowlands, thawing forested permafrost peat plateaus (‘forest’) lead to expansion of permafrost‐free wetlands (‘wetland’). Expanding wetland area with saturated and warmer organic soils is expected to increase landscape methane (CH4) emissions. Here, we quantify the thaw‐induced increase in CH4 emissions for a boreal forest‐wetland landscape in the southern Taiga Plains, Canada, and evaluate its impact on net radiative forcing relative to potential long‐term net carbon dioxide (CO2) exchange. Using nested wetland and landscape eddy covariance net CH4 flux measurements in combination with flux footprint modeling, we find that landscape CH4 emissions increase with increasing wetland‐to‐forest ratio. Landscape CH4 emissions are most sensitive to this ratio during peak emission periods, when wetland soils are up to 10 °C warmer than forest soils. The cumulative growing season (May–October) wetland CH4 emission of ~13 g CH4 m−2 is the dominating contribution to the landscape CH4 emission of ~7 g CH4 m−2. In contrast, forest contributions to landscape CH4 emissions appear to be negligible. The rapid wetland expansion of 0.26 ± 0.05% yr−1 in this region causes an estimated growing season increase of 0.034 ± 0.007 g CH4 m−2 yr−1 in landscape CH4 emissions. A long‐term net CO2 uptake of >200 g CO2 m−2 yr−1 is required to offset the positive radiative forcing of increasing CH4 emissions until the end of the 21st century as indicated by an atmospheric CH4 and CO2 concentration model. However, long‐term apparent carbon accumulation rates in similar boreal forest‐wetland landscapes and eddy covariance landscape net CO2 flux measurements suggest a long‐term net CO2 uptake between 49 and 157 g CO2 m−2 yr−1. Thus, thaw‐induced CH4 emission increases likely exert a positive net radiative greenhouse gas forcing through the 21st century

    Who Dies? International Trade, Market Structure, and Industrial Restructuring

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    This paper examines the role of changing factor endowments in the growth and decline of industries and regions. The implications of an endowment-based Heckscher-Ohlin trade model for plant entry and exit are tested on 20 years of data for the entire US manufacturing sector. The trade model provides predictions for which industries will see growth through the positive net entry of plants. A multi-region version of the same model has predictions for which regions will see high turnover and net entry of plants. In a country such as the U.S. that is augmenting both its physical and human capital, the least capital-intensive, least skill-intensive industries are correctly predicted to have the lowest rate of net entry. In addition, increases in regional capital and skill intensity are associated with higher probabilities of shutdown, especially for plants in industries with low initial capital and skill intensities.

    Optimal Coastal Land Use and Management in Krabi, Thailand: Compromise Programming Approach

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    This paper identifies the optimal options of Krabi’s coastal land use to facilitate the final planning decision. Through compromise programming approach, the optimization models with respect to the weights assigned to two objectives of maximizing the net private and environmental benefits are formulated to derive the options. Various externality management scenarios based on different applications of policy tools are assessed. All scenarios suggest the optimal options in favour of mangrove conservation when both objectives are considered equally important. This is not the case when the private benefit objective is assigned a higher weight at a certain level for each scenario, which results in the pro development of shrimp farming. The policy framework based on a combination of carrying capacity and green taxation regime would ensure that even if the pro development option were chosen, the positive net environmental gain and the integrity of coastal receiving waters would be obtained.coastal land management, weighted compromise programming, decision making, Krabi province

    Positive-Net-Damping Stability Criterion in Grid-Connected VSC Systems

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    Resonance instabilities in power systems can be assessed with the positive-net-damping stability criterion. This criterion is a review of the complex torque coefficients method but it does not provide the frequency of the closed-loop oscillatory modes. This paper presents an alternative approach of the positive-net-damping stability criterion to analyze electrical resonance instability. In this approach, resonance instabilities are identified in feedback systems derived from impedance-based equivalent circuits. The proposed approach is used to characterize the frequency of closed-loop oscillatory modes and identify the physical and control parameters of the system that increase or reduce the damping of these modes. The extension of the proposed approach to study the stability of Single-Input Single-Output and Multiple-Input Multiple-Output feedback systems is analyzed and the approach is also compared with other stability methods in the literature. An example of an offshore wind power plant illustrates the theoretical study and compares the proposed approach with different methods to evaluate stability. Time-domain simulations in PSCAD/EMTDC are shown to validate the stability study

    The positive net profit space is a subspace of the transfer space

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    The substrate concentration in source and sink and the combined net profit of the ensemble of both are the coordinates of the transfer space. Net profit is the difference of a non-linear benefit function and a linear cost function of the substrate concentration. The net profit of the ensemble, the sum of the net profit of source and sink, results in a surface within the transfer space. This surface is partially below zero, a negative net profit, and partially above zero, a positive net profit. Superadditivity appears when the surface with transfer is above the surface without transfer. Subadditivity is the revers situation. Superadditivity and subadditivity are independent of a positive or negative net profit. A positive net profit for the single parties and superadditivity for the ensemble would be optimal. I demonstrate that in a subspace of the transfer space (area III) a positive net profit for source and sink and superadditivity for the ensemble is possible. Two reservations have to be made: First, source has to be forced or deceived to give substrate beyond b=c, an attractor within the larger transfer space. Second, increased positive net profit for source and sink in symmetric ensembles is achieved on cost of superadditivity for the ensemble. The superadditive net profit of the ensemble by transfer and the individual net profit of source and sink are a trade-off within the subspace. If the individual net profit for source and sink is maxed out simultaneously, superadditivity is absent and additional transfers result in subadditivity in symmetric ensembles. Observing both limits of maximal net profit avoids subadditivity in area III. This is similar to the transfer space with the holding lines b=c. Such a pair of checklines is absent in area II

    The Mobile Phone in the Diffusion of Knowledge for Institutional Quality in Sub-Saharan Africa

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    This study assesses the mobile phone in the diffusion of knowledge for better governance in Sub-Saharan Africa from 2000 to 2012. For this purpose we employ Generalised Method of Moments with forward orthogonal deviations. The empirical evidence is based on three complementary knowledge diffusion variables (innovation, internet penetration and educational quality) and 10 governance indicators that are bundled and unbundled. The following are the main findings. First, there is an unconditional positive effect of mobile phone penetration on good governance. Second, the net effects on political, economic, and institutional governances that are associated with the interaction of the mobile phone with knowledge diffusion variables are positive for the most part. Third, countries with low levels of governance are catching-up their counterparts with higher levels of governance. The above findings are broadly consistent with theoretical underpinnings on the relevance of mobile phones in mitigating bad governance in Africa. The evidence of some insignificant net effects and decreasing marginal impacts may be an indication that the mobile phone could also be employed to decrease government quality. Overall, this study has established net positive effects for the most part. Five rationales could elicit the positive net effects on good governance from the interaction between mobile phones and knowledge diffusion, among others, the knowledge variables enhance: reach, access, adoption, cost-effectiveness, and interaction. In a nut shell, the positive net effects are apparent because the knowledge diffusion variables complement mobile phones in reducing information asymmetry and monopoly that create conducive conditions for bad governance. The contribution of the findings to existing theories and justifications of the underlying positive net effects are discussed

    Coulomb interaction on pion production in Au+Au collisions at relativistic energies

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    Coulomb effects on charged pion transverse momentum spectra produced in Au+Au collisions at RHIC-BES energies are investigated. From these spectra the {\pi}-/{\pi}+ ratios as a function of transverse momentum are obtained and used to extract the Coulomb kick (a momentum change due to Coulomb interaction) and initial pion ratio for three different collision energies and various centrality classes. The Coulomb kick shows a decrease with the increase of beam energy and a clear centrality dependence, with larger values for the most central collisions. The results are connected with the kinetic freeze-out dynamics and discussed

    Foreign Direct Investment, Information Technology and Economic Growth Dynamics in Sub-Saharan Africa

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    The research assesses how information and communication technology (ICT) modulates the effect of foreign direct investment (FDI) on economic growth dynamics in 25 countries in Sub-Saharan Africa for the period 1980-2014. The employed economic growth dynamics areGross Domestic Product (GDP) growth, real GDP and GDP per capita while ICT is measured by mobile phone penetration and internet penetration. The empirical evidence is based on the Generalised Method of Moments. The study finds that both internet penetration and mobile phone penetration overwhelmingly modulate FDI to induce overall positive net effects on all three economic growth dynamics. Moreover, the positive net effects are consistently more apparent in internet-centric regressions compared to “mobile phone”-oriented specifications. In the light of negative interactive effects, net effects are decomposed to provide thresholds at which ICT policy variables should be complemented with other policy initiatives in order to engender favorable outcomes on economic growth dynamics. Practical and theoretical implications are discussed
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