13,798 research outputs found
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Changes in NDVI and human population in protected areas on the Tibetan Plateau
Understanding the Tibetan Plateau’s role in environmental change has gained increasing scientific
attention in light of warming and changes in landmanagement. We examine changes in greenness over
the Tibetan Plateau using the Normalized Difference Vegetation Index (NDVI) from the Global Inventory
Monitoring and Modeling Study (GIMMS3g) to identify significant changes over the entire plateau, six
ecoregions, and protected areas based on a multiyear time series of July imagery from 1982 to 2015. We
also test whether there have been changes in human populations in protected areas. There has been
relatively little change in mean NDVI over the Tibetan Plateau or ecoregions, however, there were
significant changes at the pixel level. There are sixty-nine protected areas on the Tibetan Plateau; sixtytwo
protected areas had no significant change in mean NDVI and seven protected areas experienced
a significant increase in NDVI. There has been an increase in population within protected areas from
2000 to 2015; however, mean populations significantly increased in two protected areas and significantly
decreased in four protected areas. Results suggest a slow greening of the Tibetan Plateau,
ecoregions, and protected areas, with a more rapid greening in northern Tibet at the pixel level. Most
protected areas are experiencing minor changes in NDVI independent of human population
Bounded Model Checking of State-Space Digital Systems: The Impact of Finite Word-Length Effects on the Implementation of Fixed-Point Digital Controllers Based on State-Space Modeling
The extensive use of digital controllers demands a growing effort to prevent
design errors that appear due to finite-word length (FWL) effects. However,
there is still a gap, regarding verification tools and methodologies to check
implementation aspects of control systems. Thus, the present paper describes an
approach, which employs bounded model checking (BMC) techniques, to verify
fixed-point digital controllers represented by state-space equations. The
experimental results demonstrate the sensitivity of such systems to FWL effects
and the effectiveness of the proposed approach to detect them. To the best of
my knowledge, this is the first contribution tackling formal verification
through BMC of fixed-point state-space digital controllers.Comment: International Symposium on the Foundations of Software Engineering
201
Plasma-Like Negative Capacitance in Nano-Colloids
A negative capacitance has been observed in a nano-colloid between 0.1 and
10^-5 Hz. The response is linear over a broad range of conditions. The
low-omega dispersions of both the resistance and capacitance are consistent
with the free-carrier plasma model, while the transient behavior demonstrates
an unusual energy storage mechanism. A collective excitation, therefore, is
suggested.Comment: 3 pages, 3 figure
Experimentally obtaining the Likeness of Two Unknown Quantum States on an NMR Quantum Information Processor
Recently quantum states discrimination has been frequently studied. In this
paper we study them from the other way round, the likeness of two quantum
states. The fidelity is used to describe the likeness of two quantum states.
Then we presented a scheme to obtain the fidelity of two unknown qubits
directly from the integral area of the spectra of the assistant qubit(spin) on
an NMR Quantum Information Processor. Finally we demonstrated the scheme on a
three-qubit quantum information processor. The experimental data are consistent
with the theoretical expectation with an average error of 0.05, which confirms
the scheme.Comment: 3 pages, 4 figure
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Calibration Procedures for a Computational Model of Ductile Fracture
A recent extension of the Gurson constitutive model of damage and failure of ductile structural alloys accounts for localization and crack formation under shearing as well as tension. When properly calibrated against a basic set of experiments, this model has the potential to predict the emergence and propagation of cracks over a wide range of stress states. This paper addresses procedures for calibrating the damage parameters of the extended constitutive model. The procedures are demonstrated for DH36 steel using data from three tests: (i) tension of a round bar, (ii) mode I cracking in a compact tension specimen, and (iii) shear localization and mode II cracking in a shear-off specimen. The computational model is then used to study the emergence of the cup-cone fracture mode in the neck of a round tensile bar. Ductility of a notched round bar provides additional validation.Engineering and Applied Science
Barriers to Building Information Modeling (BIM) implementation in China's prefabricated construction: An interpretive structural modeling (ISM) approach
It is widely recognized that Building Information Modeling (BIM) can facilitate the delivery of prefabricated construction. Nevertheless, the actual practice of BIM faces several barriers. A range of existing studies and literature have discussed these barriers extensively, but two research questions remain unanswered. First, what are the unique barriers facing the use of BIM in China's prefabricated construction? Second, how do these barriers interrelate with one another? This research aims to address these two questions. Conducting a two-round literature review and a questionnaire survey ascertained twelve barriers acutely affecting the Chinese experience of applying BIM to prefabricated construction. In addition, Interpretive Structural Modeling (ISM) was used to identify interrelationships among these barriers. The exercise found that, compared with the cost-related issues suggested by previous studies that focused on general BIM implementation barriers, the lack of research about BIM in China and the absence of standards and domestic-oriented tools are likely the biggest hindrances to the practical application of BIM in China's prefabricated construction. This study contributes to the knowledge body by revealing major barriers to BIM implementation in China's prefabricated construction and crafting a corresponding three-level strategy to facilitate the possible implementation. The findings of this study can thus act as a practical reference for future research attempting to provide technological and managerial solutions to improve BIM implementation in China's prefabricated construction
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