Search results for " Heterogeneous"

Automated Diffraction Tomography for the Structure Elucidation of Twinned, Sub-micrometer Crystals of a Highly Porous, Catalytically Active Bismuth M…

2012

Airborne-laser-scanning-derived auxiliary information discriminating between broadleaf and conifer trees improves the accuracy of models for predicti…

2020

Managing forests for ecosystem services and biodiversity requires accurate and spatially explicit forest inventory data. A major objective of forest management inventories is to estimate the standing timber volume for certain forest areas. In order to improve the efficiency of an inventory, field based sample-plots can be statistically combined with remote sensing data. Such models usually incorporate auxiliary variables derived from canopy height models. The inclusion of forest type variables, which quantify broadleaf and conifer volume proportions, has been shown to further improve model performance. Currently, the most common way of quantifying broadleaf and conifer forest types is by ca…

Opinion Dynamics and Stubbornness via Multi-Population Mean-Field Games

2016

This paper studies opinion dynamics for a set of heterogeneous populations of individuals pursuing two conflicting goals: to seek consensus and to be coherent with their initial opinions. The multi-population game under investigation is characterized by (i) rational agents who behave strategically, (ii) heterogeneous populations, and (iii) opinions evolving in response to local interactions. The main contribution of this paper is to encompass all of these aspects under the unified framework of mean-field game theory. We show that, assuming initial Gaussian density functions and affine control policies, the Fokker---Planck---Kolmogorov equation preserves Gaussianity over time. This fact is t…

Improved (photo)catalytic propene hydration in a gas/solid system by using heteropolyacid/oxide composites: Electron paramagnetic resonance, acidity,…

2017

Binary materials composed of the oxides SiO2, TiO2 and N-doped TiO2 and the Keggin heteropolyacid (PW12) were prepared and physicochemically characterized. They were used as catalysts and photocatalysts for the hydration of propene to 2-propanol. The characterization of the samples, particularly the electron paramagnetic resonance (EPR) spectroscopy results and the acidity properties, were useful to explain the key role played by the PW12 in the composite materials in the thermal and photoassisted catalytic processes. The simultaneous pres-ence of heat and UV light improved the activity of PW12 in the thermal process, and the binary materials showed better (photo)catalytic activities than t…

Preparation of photocatalysts by physical methodologies

2021

The synthesis of photocatalytic materials is an important task for obtaining better results in terms of activity and/or selectivity in photocatalysis. This chapter reports an overview of the main methodologies using physical techniques to obtain bulky, supported powders or films and coatings to be used as heterogeneous photocatalysts. The classical chemical methodologies for the preparation of photocatalytic materials are presented in the previous chapter, so the information presented here complements the aforementioned one. Materials scientists and engineers have made significant progresses in the improvement of methods of synthesis of nanomaterial solids by developing different apparatuse…

A Simulation Analysis of the Microstructure of an Order Driven Financial Market with Multiple Securities and Portfolio Choices

2005

In this paper we propose an artificial market where multiple risky assets are exchanged. Agents are constrained by the availability of resources and trade to adjust their portfolio according to an exogenously given target portfolio. We model the trading mechanism as a continuous auction order-driven market. Agents are heterogeneous in terms of desired target portfolio allocations, but they are homogeneous in terms of trading strategies. We investigate the role played by the trading mechanism in affecting the dynamics of prices, trading volume and volatility. We show that the institutional setting of a double auction market is sufficient to generate a non-normal distribution of price changes…

Preparation and photoactivity of nanocrystalline TiO2 powders obtained by thermohydrolysis of TiOSO4

2013

Nanocrystalline TiO2 photocatalysts were synthesized in mild conditions by thermohydrolysis of TiOSO4 in water at 100 °C and post-calcination treatment at various temperatures. The TiO2 powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area determinations, scanning electron microscopy and electron paramagnetic resonance measurements. The photoactivity of the samples was tested employing the photodegradation of 4-nitrophenol in liquid–solid regimen and the photooxidation of gaseous 2-propanol. The best results were obtained with the powder calcined at 600 °C for 10 h. Surprisingly, the not calcined sample was the most active for the abatement…

Heterogeneous vs Homogeneous Palladium Catalysts for Cross-Coupling Reactions

2012

A large number of immobilized-Pd-catalysts for cross-coupling reactions have been introduced in the last decade. Are the observed catalyzed reactions truly heterogeneous or are they homogeneous due to leached palladium? This account critically addresses the leaching issue by selectively referring to some of the newly developed catalytic systems in an attempt to evaluate said systems based on uniform criteria. The report is concluded by identifying the relevant chemical and structural challenges in the field.

Multifunctional halloysite and hectorite catalysts for effective transformation of biomass to biodiesel

2023

Halloysite surface was modified with tetrabutylammonium iodide, and then the obtained nanomaterial was used as support for ZnO nanoparticles. After characterization, the nanomaterial was used as a catalyst for fatty acid methyl esters (FAMEs) production. The recyclability of the nanomaterial was also investigated, and the optimization of reaction conditions by the design of experiments approach was performed as well. In addition, the synthesized nanomaterial was tested as a catalyst for FAME production from a series of waste lipids affording biodiesel in moderate to good yields (35–95%), depending on the matrix. To fully exploit the feasibility of clay minerals as catalysts in biodiesel for…

Automated Synthesis of Application-layer Connectors from Automata-based Specifications

2019

Abstract Ubiquitous and Pervasive Computing, and the Internet of Things, promote dynamic interaction among heterogeneous systems. To achieve this vision, interoperability among heterogeneous systems represents a key enabler, and mediators are often built to solve protocol mismatches. Many approaches propose the synthesis of mediators. Unfortunately, a rigorous characterization of the concept of interoperability is still lacking, hence making hard to assess their applicability and soundness. In this paper, we provide a framework for the synthesis of mediators that allows us to: (i) characterize the conditions for the mediator existence and correctness; and (ii) establish the applicability bo…