Are carrier-to-noise algorithms equivalent in all situations?

This paper describes methods to estimate the carrier to noise ratio in GNSS application

A model for enhanced coal bed methane recovery aimed at carbon dioxide storage: The role of sorption, swelling and composition of injected gas

Numerical simulations on the performance of CO2 storage and enhanced coal bed methane (ECBM) recovery in coal beds are presented. For the calculations, aone-dimensional mathematical model is used consisting of mass balances describing gas flow and sorption, and a geomechanical relationship to account for porosity and permeability changes during injection. Important insights are obtained regarding the gas flow dynamics during displacement and the effects of sorption and swelling on the ECBM operation. In particular, initial faster CH4 recovery is obtained when N2 is added to the injected mixture, whereas pure CO2 allows for a more effective displacement in terms of total CH4 recovery. Moreover, it is shown that coal swelling dramatically affects the gas injectivity, as the closing of the fractures associated with it strongly reduces coal's permeability. As a matter of fact, injection of flue gas might represent a useful option to limit this proble

Replicon-dependent bacterial genome evolution: the case of Sinorhizobium meliloti

Many bacterial species, such as the alphaproteobacterium Sinorhizobium meliloti, are characterized by open pangenomes and contain multipartite genomes consisting of a chromosome and other large-sized replicons, such as chromids, megaplasmids, and plasmids. The evolutionary forces in both functional and structural aspects that shape the pangenome of species with multipartite genomes are still poorly understood. Therefore, we sequenced the genomes of 10 new S. meliloti strains, analyzed with four publicly available additional genomic sequences. Results indicated that the three main replicons present in these strains (a chromosome, a chromid, and a megaplasmid) partly show replicon-specific behaviors related to strain differentiation. In particular, the p SymB chromid was shown to be a hot spot for positively selected genes, and, unexpectedly, genes resident in the pSymB chromid were also found to be more widespread in distant taxa than those located in the other replicons. Moreover, through the exploitation of a DNA proximity network, a series of conserved "DNA backbones" were found to shape the evolution of the genome structure, with the rest of the genome experiencing rearrangements. The presented data allow depicting a scenario where the pSymB chromid has a distinctive role in intraspecies differentiation and in evolution through positive selection, whereas the pSymA megaplasmid mostly contributes to structural fluidity and to the emergence of new functions, indicating a specific evolutionary role for each replicon in the pangenome evolution. © 2013 The Author(s)

Are carrier-to-noise algorithms equivalent in all situations?

This paper describes methods to estimate the carrier to noise ratio in GNSS applications

Prediction of competitive adsorption on coal by a lattice DFTmodel

Adsorption is one of the main mechanisms involved in the ECBM process, a technology where CO2(or flue gas, i.e. a CO2/N2mixture) is injected into a deep coal bed, with the aim of storing CO2by simultaneously recovering CH4. A detailed understanding of the microscopic adsorption process is therefore needed, as the latter controls the displacement process. A lattice DFT model, previously extended to mixtures, has been applied to predict the competitive adsorption behavior of CO2, CH4and N2and of their mixtures in slit-shaped pores of 1.2 and 8nm width. In particular, the effect of temperature, bulk composition and density on the resulting lattice pore profiles and on the lattice excess adsorption isotherms has been investigated. Important insights could be obtained; when approaching near critical conditions in the mesopores, a characteristic peak in the excess adsorption isotherm of CO2appears. The same effect could be observed neither for the other gases nor in the micropores. Moreover, in the case of mixtures, a depletion of the less adsorbed species close to the adsorbent surface is observed, which eventually results in negative lattice excess adsorption at high bulk densitie

Pure and binary adsorption of CO2, H2, and N2 on activated carbon

A new developing field of application for pressure swing adsorption (PSA) processes is the capture of CO2 to mitigate climate change, especially the separation of CO2 and H2 in a pre-combustion context. In this process scheme the conditions of the feed to the separation step, namely a pressure of 3.5 to 4.5MPa and a CO2 fraction of around 40% are favorable for an adsorption based separation process and make PSA a promising technology. Among the commercial adsorbent materials, activated carbon is most suitable for this application. To evaluate the potential, to benchmark new materials, and for process development a sound basis of the activated carbon thermodynamic data is required, namely equilibrium adsorption isotherms of the relevant pure components and mixtures, Henry's constants and isosteric heats. In this work pure adsorption equilibria of CO2, H2 and N2 on commercial activated carbon (AP3-60 from Chemviron, Germany) are measured using a Rubotherm Magnetic Suspension Balance (MSB) (Bochum, Germany) in a wide temperature and pressure range. The data is used to fit the temperature dependent parameters of Langmuir and Sips (Langmuir-Freundlich) isotherms and to determine the Henry's constants as well as isosteric heats. Based on this evaluation different methods to evaluate the data are compared and discussed. With the pure isotherm parameters of the Sips isotherm binary adsorption is predicted using an empirical binary Sips equation and ideal adsorbed solution theory (IAST). The results are compared to binary measurements in the same MSB applying a gravimetric-chromatographic metho

Fixed bed adsorption of CO2/H2 mixtures on activated carbon: experiments and modeling

We present breakthrough experiments in a fixed bed adsorber packed with commercial activated carbon involving feed mixtures of carbon dioxide and hydrogen of different compositions. The experiments are carried out at four different temperatures (25°C, 45°C, 65°C and 100°C) and seven different pressures (1bar, 5bar, 10bar, 15bar, 20bar, 25bar and 35bar). The interpretation of the experimental data is done by describing the adsorption process with a detailed one-dimensional model consisting of mass and heat balances and several constitutive equations, such as an adsorption isotherm and an equation of state. The dynamic model parameters, i.e. mass and heat transfer, are fitted to one single experiment (reference experiment) and the model is then further validated by predicting the remaining experiments. Furthermore, the choice of the isotherm model is discussed. The assessment of the model accuracy is carried out by comparing simulation results and experimental data, and by discussing key features and critical aspects of the model. This study is valuable per se and a necessary step toward the design, development and optimization of a pressure swing adsorption process for the separation of CO2 and H2 for example in the context of a pre-combustion CO2 capture process, such as the integrated gasification combined cycle technolog

HOMOGENEOUS HYDROGEN DEFLAGRATIONS IN SMALL SCALE ENCLOSURE. EXPERIMENTAL RESULTS

University of Pisa performed experimental tests in a 1 m3 facility, which shape and dimensions resemble a gas cabinet, for the HySEA project, founded by the Fuel Cells and Hydrogen 2 Joint Undertaking with the aim to conduct pre-normative research on vented deflagrations in real-life enclosures and containers used for hydrogen energy applications, in order to generate experimental data of high quality. The test facility, named Small Scale Enclosure (SSE), had a vent area of 0,42 m2 which location could be varied, namely on the top or in front of the facility, while different types of vent were investigated. Three different ignition location were investigated as well, and the range of Hydrogen concentration ranged between 10 and 18% vol. This paper is aimed to summarize the main characteristics of the experimental campaign as well as to present its results