Woody Feedstock Pretreatments to Enhance Pyrolysis Bio-oil Quality and Produce Transportation Fuel

Lignocellulosic biomass as a potential renewable source of energy has a near-zero CO2 emission. Pyrolysis converts biomass to a liquid fuel and increases the energy density and transportability. The pyrolysis bio-oil shows promising properties to substitute the conventional fossil fuels. But, unprocessed biomass is low in bulk and energy density; high in moisture; heterogeneous in physical and chemical properties, highly hygroscopic and difficult to handle. That is why the biomass needs mechanical, chemical and/or thermal pretreatments to turn into a more homogeneous feedstock and minimize the post-treatment fuel upgrading. This chapter explains the effects that various pretreatments such as size reduction, drying, washing and thermal pretreatments have on the quality and quantity of bio-oil. Washing with water or acid/alkali solutions extracts the minerals that consequently reduces the ash and shortens the reactor clean-out cycle. Torrefaction is gaining attention as an effective pretreatment to modify the quality of biomass in terms of physical and chemical properties. Torrefaction produces a uniform biomass with lower moisture, acidity and oxygen contents and higher energy density and grindability than raw biomass. Pyrolysis of torrefied biomass produces bio-oil with enhanced compositional and physical properties such as a higher heating value and increased C (lower O/C ratio)

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Gas residence time distribution and related flow patterns in spouted beds

A two-region model of a spouted bed which takes into account the actual path followed by the gas in the annulus, has been developed to predict the residence time distribution of gas in the bed. The model is based on the assumptions of plug flow of gas in the spout and dispersed plug flow along the flow path in the annulus. The flow path in the annulus is described by postulating that all the gas entering the annulus from the spout at a given level travels radially and vertically along a particular flow path without radial dispersion or mixing. This picture is consistent with visual observations made using NO₂ gas as tracer. The hydrodynamic data needed as input to the model are gas velocities in spout and annulus, spout shape and spout voidage. The residence time distribution of gas together with the above-mentioned hydrodynamic features were measured experimentally for a wide range of spouting conditions. The RTD data were obtained from stimulus-response experiments using helium gas injected as a negative step into the spouting gas downstream of the gas inlet. The gas velocity in the spout was determined by pitot tube, and in the annulus by static pressure measurements. High speed cine-photography was employed to measure spout particle velocities (in half-sectional beds) and spout voidage distribution was determined from spout and annulus particle velocities by solids mass balance. The values of the axial dispersion coefficient for the annulus gas which is an adjustable parameter of the model, were estimated by comparing predicted and experimental RTD curves. The coefficients for spouted beds were found to be generally higher than those reported for packed beds, but at least an order of magnitude smaller than those for fluidized beds. The hydrodynamic data obtained were analyzed to test published theories and correlations and to improve upon these wherever possible. The Mamuro-Hattori equation was found to give good prediction of annulus longitudinal gas velocity profiles for 15.2 cm diameter beds but to under-estimate velocities for larger columns. The equation of Yokogawa et al. proved to be unsatisfactory for predictive purposes and was modified. The modified version can predict the gas velocity profile in the annulus correctly provided that one such profile for the particular solid material is known. The data from the present study showed good agreement with the equation of Grbavcic et al. for gas velocity at the top of the annulus. A simple model was formulated, based on the observed solids flow pattern in the annulus, which enables the calculation of solids flow path and retention time in the annulus from average particle velocity data. For particle velocity in the spout, the force balance model of Thorley et at. as amended by Mathur and Epstein was further improved by introducing the theoretical relationship between spout voidage and number of particles in the spout. The resulting equation was found to give good agreement with experimental values of not only spout particle velocity but also of spout voidage.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat

Axial dispersion of the continuous phase in liquid-liquid extraction spray columns and internal sampling techniques

An internal sampler, a plastic cup probe, was constructed to replace a funnel-probe for sampling the dispersed phase (methyl isobutyl ketone) in a liquid-liquid extraction spray column. The dispersed phase sample can be withdrawn from the column by the plastic cup probe without being contaminated with the continuous phase water. For runs in which the mass transfer is from the continuous phase to the dispersed phase, the plastic cup probe results agree with those obtained by the funnel-probe. On the other hand, for runs in which the direction of mass transfer is reversed, the plastic cup probe tends to give slightly lower dispersed phase concentrations than does the funnel-probe at the same sampling elevation. It is believed that both methods of measuring concentrations are correct within less than 2%. The effect of mass transfer on the axial dispersion coefficient of the continuous phase in a 1.5-in. I.D. liquid-liquid extraction spray column was studied for various superficial velocities of two phases, and for various partitionable solute (acetic acid) concentrations in the continuous phase fed to the column. Tracer solution (sodium chloride solution) was injected steadily into the continuous phase in the column. Axial concentration profiles of the tracer were measured upstream, with respect to the continuous phase, from the tracer distributor. The steady state form of the dispersion equation was used to calculate the axial dispersion coefficient of the continuous phase. The results obtained show that there is no effect of mass transfer on the axial dispersion coefficient within the range of the investigation. Drop size distribution and holdup of the dispersed phase in the column also were measured. The drop size distribution always shows two peaks. It was found that there is no effect of mass transfer on both the drop size distribution and on the dispersed phase holdups within the range of investigation.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat

Advanced Undersea Warfare Systems

Includes supplementary materialOver the next twenty years, the proliferation of threats in the undersea environment will likely challenge the platform-centric model that the United States Navy uses to maintain dominance in Undersea Warfare (USW). Meanwhile, rapidly maturing technologies offer greater capabilities to potential adversaries around the world. Such a paradigm creates an imperative for the Navy to harness emerging technologies to maintain USW dominance amid a dynamic threat environment, while balancing cost, risk, and required performance. This systems engineering analysis develops Advanced Undersea Warfare Systems (AUWS) that provide a technological and tactical advantage based on the needs of the war-fighter. Following critical analysis of the numerous possible alternatives for performing the necessary Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR) and prosecution and an objective screening process, four system architectures, and associated operational concepts, are selected for detailed analysis. From cost, risk, and performance analyses, superior AUWS concepts are shown to be flexible, scalable, and tailorable systems that balance critical need areas. This analysis highlights the need for new warfare systems that can meet future challenges to the traditional platform-centric model for USW dominance. Using the results and recommendations in this analysis will allow the Navy to deploy capabilities that effectively and efficiently meet future operational needs.http://archive.org/details/advancedundersew109456959Approved for public release; distribution is unlimited

The value of open-source clinical science in pandemic response: lessons from ISARIC

International audienc

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical science. © The Author(s) 2019. Published by Oxford University Press