182 research outputs found
Unsupervised spectral learning of WCFG as low-rank matrix completion
We derive a spectral method for unsupervised
learning ofWeighted Context Free Grammars.
We frame WCFG induction as finding a Hankel
matrix that has low rank and is linearly
constrained to represent a function computed
by inside-outside recursions. The proposed algorithm picks the grammar that agrees with a sample and is the simplest with respect to the nuclear norm of the Hankel matrix.Peer ReviewedPreprin
Sustainable Biomaterials: Current Trends, Challenges and Applications
Biomaterials and sustainable resources are two complementary terms supporting the
development of new sustainable emerging processes. In this context, many interdisciplinary
approaches including biomass waste valorization and proper usage of green technologies, etc.,
were brought forward to tackle future challenges pertaining to declining fossil resources, energy
conservation, and related environmental issues. The implementation of these approaches impels its
potential effect on the economy of particular countries and also reduces unnecessary overburden on
the environment. This contribution aims to provide an overview of some of the most recent trends,
challenges, and applications in the field of biomaterials derived from sustainable resource
NH4F Modified Al-SBA-15 Materials for Esterification of Valeric Acid to Alkyl Valerates
Al-SBA-15 materials were functionalized by ball milling with several niobium loadings (0.25–1 wt.%) and/or with several F- loadings, using NH4F as a precursor. The catalysts synthesized in this study were characterised by X-ray diffraction (XRD), N2 porosimetry, and diffuse reflection infrared spectroscopy (DRIFT) among others. The prepared materials shown, form moderate to high catalytic activities in the microwave-assisted transformation of valeric acid to ethyl valerate via esterification. The incorporation of fluoride anions either into Al-SBA-15 or on Nb1%/Al-SBA-15 led to a linear increase in valeric acid conversion with the F− content. Thus, F− modified mesoporous aluminosilicates efficiently catalyze the transformation of valeric acid into alkyl valerate esters as renewable fuels
Challenges in assessing exposure and vulnerability to natural hazards in large cities: the case study of Arequipa near the Misti volcano, south Peru
Assessing risk of potential natural catastrophes in cities remains challenging, in particular as we need to elaborate quantitative criteria for exposure and vulnerability. Statistical and probabilistic methods have been applied to Arequipa, one of the most vulnerable Latin America cities. The second largest city of Peru is highly exposed to natural hazards: earthquakes, eruptions from the historically active El Misti volcano, rain-triggered flash floods and mass flows together with landslides from the Río Chili canyon walls. First, we propose a long-term probabilistic multi-hazard assessment for the Misti composite cone located 17 km from Arequipa. Second, we examine criteria for delineating areas prone to mass flow hazards and characterizing multiple sources of vulnerability forthe city. Third, a statistical methodology to better estimate damage probability for buildings is proposed
NGCPV: a new generation of concentrator photovoltaic cells, modules and systems
Starting on June 2011, NGCPV is the first project funded jointly between the European Commission (EC) and the New Energy and Industrial Technology Development Organization (NEDO) of Japan to research on new generation concentration photovoltaics (CPV). The Project, through a collaborative research between seven European and nine Japanese leading research centers in the field of CPV, aims at lowering the cost of the CPVproduced photovoltaic kWh down to 5 ?cents. The main objective of the project is to improve the present concentrator cell, module and system efficiency, as well as developing advanced characterization tools for CPV components and systems. As particular targets, the project aims at achieving a cell efficiency of at least 45% and a CPV module with an efficiency greater than 35%. This paper describes the R&D activities that are being carried out within the NGCPV project and summarizes some of the most relevant results that have already been attained, for instance: the manufacturing of a 44.4% world record efficiency triple junction solar cell (by Sharp Corp.) and the installation of a 50 kWp experimental CPV plant in Spain, which will be used to obtain accurate forecasts of the energy produced at system level
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