3,209,254 research outputs found

    Effectiveness of China's National Forest Protection Program and nature reserves

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    There is profound interest in knowing the degree to which China's institutions are capable of protecting its natural forests and biodiversity in the face of economic and political change. China's 2 most important forest-protection policies are its National Forest Protection Program (NFPP) and its national-level nature reserves (NNRs). The NFPP was implemented in 2000 in response to deforestation-caused flooding. We undertook the first national, quantitative assessment of the NFPP and NNRs to examine whether the NFPP achieved its deforestation-reduction target and whether the NNRs deter deforestation altogether. We used MODIS data to estimate forest cover and loss across mainland China (2000-2010). We also assembled the first-ever polygon dataset for China's forested NNRs (n = 237, 74,030 km(2) in 2000) and used both conventional and covariate-matching approaches to compare deforestation rates inside and outside NNRs (2000-2010). In 2000, 1.765 million km(2) or 18.7% of mainland China was forested (12.3% with canopy cover of >= 70%)) or woodland (6.4% with canopy cover = 40%). By 2010, 480,203 km(2) of forest and woodland had been lost, an annual deforestation rate of 2.7%. Forest-only loss was 127,473 km(2) (1.05% annually). In the NFPP provinces, the forest-only loss rate was 0.62%, which was 3.3 times lower than in the non-NFPP provinces. Moreover, the Landsat data suggest that these loss rates are overestimates due to large MODIS pixel size. Thus, China appears to have achieved, and even exceeded, its target of reducing deforestation to 1.1% annually in the NFPP provinces. About two-thirds of China's NNRs were effective in protecting forest cover (prevented loss 4073 km(2) unmatched approach; 3148 km(2) matched approach), and within-NNR deforestation rates were higher in provinces with higher overall deforestation. Our results indicate that China's existing institutions can protect domestic forest cover

    First look analyses of five cycles of ERTS-1 imagery over County of Los Angeles: Assessment of data utility for urban development and regional planning

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    Significant results have been obtained from the analyses of ERTS-1 imagery from five cycles over Test Site SR 124 by classical photointerpretation and by an interactive hybrid multispectral information extraction system (GEMS). The synopticity, periodicity and multispectrality of ERTS coverage, available for the first time to LA County planners, have opened up both a new dimensionality in data and offer new capability in preparation of planning inputs. Photointerpretation of ERTS images has produced over 25 overlays at 1:1,000,000 scale depicting regional relations and urban structure in terms of several hundred linear and areal features. To mention only one such result, a possible new fault lineament has been discovered on the northern slope of the Santa Monica mountains in the scene 1144-18015, composited of MSS bands 4, 5, 6,. GEMS analysis of the ERTS products has provided new or improved information in the following planning data categories: urban vegetation; land cover segregation; man-made and natural impact monitoring; urban design; and suitability. ERTS data analysis has allowed planners to establish trends that directly impact planning policies. This new source of information will not only assist current methods to be more efficient, but permits entirely new planning methodologies to be employed

    EFFECT OF ACCELERATED AGING ON MECHANICAL PROPERTIES AND STRUCTURE OF NANO-SCALE COMPOSITE SYSTEMS

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    Nano-scale composites are being investigated by academic, industrial, and national laboratories for potential applications such as wear resistant coatings and high strength foils. These structures are of interest due to their as-fabricated mechanical properties, such as high strength for nanolaminates. However, there have only been limited studies of the long-term mechanical stability. A greater understanding of how these systems might respond to sustained use is needed before these systems transition from research laboratories into widespread application. It is the objective of this thesis to clarify the link between accelerated aging using elevated temperatures over time and mechanical properties of two distinct types of nano-scale composite systems: metallic nanolaminates and polyimide matrix nanocomposites. Metallic nanolaminates are composites with alternating laminar metallic films whose individual layer thicknesses range from 2 nm to 100 nm. As the individual layer thicknesses decrease, the hardness of the nanolaminate system exceeds predictions from both conventional composite theories as well as the traditional Hall-Petch relation. This study examined how these nanolaminates responded to accelerated aging (elevated temperatures in three different atmospheres) by characterizing the mechanical response. Two different systems were studied, Cu/Nb, a FCC/BCC system studied by other groups, and Ti/W, a HCP/BCC system that has not been previously studied. Nanolaminate systems produced for this study had a total thickness of 1000 nm with individual layer thicknesses of 20 nm or 100 nm. After deposition, the film systems were heated to 400¡C for 30 minutes under lab air, high purity argon, or a 98%Ar/2%O2 blend. Accelerated aging of the Cu/Nb layers caused significant softening in the 20nm layer thickness samples (5.5 to 1.3 GPa for 20 nm Cu/Nb aged in Ar). Contrastingly, softening was not observed in 100 nm layer thickness samples (4.3 to 4.8 GPa for 100 nm Cu/Nb aged in Ar). This same trend was also followed by the other Cu/Nb samples and all the Ti/W systems regardless of aging atmosphere. Comparison with other studies show that residual stress may influence the severity of the film aging. It was concluded that for both systems oxidation is not the main concern for softening induced by accelerated aging. The second type of nano-scaled composite system examined was polyimide matrix nanocomposites. NASA is exploring these systems for high-temperature aerospace applications, such as the matrix material for jet engine casings. This work looks at the mechanical aging of polyimide PMR-15, which is currently in use, and RTM-370, a possible replacement to PMR-15. In addition, this study looks at how the aging behavior is affected by the inclusion of three distinct nanoparticle filler materials: carbon nanofiber, synthetic clay, and organically modified natural clay. The elastic modulus of the polyimide nanocomposites were measured before and after accelerated aging. It was seen that the PMR-15 samples were susceptible to surface oxidation and stiffening due to the molding procedure (5.7 to 6.7 GPa for the edge region of neat PMR-15). Similar results were not found for the RTM-370 samples, as stiffness remained consistent regardless of indentation location. Nanoparticle addition to the polyimides yielded varying results. It is hypothesized that this disparity is due to the difference in particle surface area between nanoparticle fillers. Although the incorporation of nanoparticles was done in order to boost oxidation resistance in these systems, this was not observed in this study

    Little Hoover Commission

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    China Confronts the Challenge of Globalization: Implications for Domestic Cohesion and International Cooperation

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    Examines how the globalization process will affect Chinese leaders' interest in participating in international efforts to respond to global challenges, and the Chinese leadership's capacity to address domestic and international challenges

    Performance of Nanoscale Metallic Multilayer Systems Under Mechanical and Thermal Loading

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    Reports of nanoscale metallic multilayers (NMM) performance show a relatively high strength and radiation damage resistance when compared their monolithic components. Hardness of NMMs has been shown to increase with increasing interfacial density (i.e. decreasing layer thickness). This interface density-dependent behavior within NMMs has been shown to deviate from Hall-Petch strengthening, leading to higher measured strengths during normal loading than those predicted by a rule of mixtures. To fully understand why this occurs, other researchers have looked at the influence of the crystal structures of the component layers, orientations, and compositions on deformation processes. Additionally, a limited number of studies have focused on the structural stability and possible performance variation between as-deposited systems and those exposed to mechanical and thermal loading

    Congress Needs to Find a Productive Role in Restoring Confidence to Our Financial System

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    As our very resilient economy begins the long road to recovery, we will need to evaluate the lessons learned from the financial market turmoil.Senate, banking, Senate Banking Committee, GSE, discal discipline, financial system, federal, congress, confidence

    The Southeast Economy: As Goes the Nation?

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    So what of the Southeast economy? Are we doing better than, the same as, or worse than the U.S. economy as a whole?Southeast economy, southeast, economy, employment, sales, revenue
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