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

An experimental investigation of biodiesel steam reforming

Recently, liquid biofuels have attracted increasing attention as renewable feedstock for hydrogen production in the transport sector. Since the lack of hydrogen infrastructure and distribution poses an obstacle for the introduction of fuel cell vehicles to the market, it is reasonable to consider using liquid biofuels for on-board or on-site hydrogen generation. Biodiesel offers the advantage of being an environmentally friendly resource while also having high gravimetric and volumetric energy density. The present study constitutes an experimental investigation of biodiesel steam reforming, the main emphasis of which is placed on finding optimum operating conditions in order to avoid catalyst deactivation. Temperature was varied from 600 °C to 800 °C, pressure from 1 bar to 5 bar and the molar steam-to-carbon ratio from 3 to 5. Based on the experimental results, coke formation and sintering are identified as the main deactivation mechanisms. Initiation of catalyst deactivation primarily depends on catalyst inlet temperature and feed mass flow per open area of catalyst. By using a metallic based precious metal catalyst, applying low feed flow rates (31 g/h∙cm2) and a sufficiently high catalyst inlet temperature (>750 °C) coking can be minimized, thus avoiding catalyst deactivation. A stable product gas composition close to chemical equilibrium has been achieved over 100 h with a biodiesel conversion rate of 99%

Dezentrale Wasserstofferzeugung aus Diesel und Biodiesel

Der Energieträger Wasserstoff wird im Verkehrssektor in den kommenden Jahren zunehmend an Bedeutung gewinnen. Eine mögliche Alternative zur zentralen H2-Erzeugung aus Erdgas ist die dezentrale Bereitstellung von Wasserstoff durch Reformierung von Flüssigbrennstoffen. Im Rahmen des EU-Projektes NEMESIS2+ (www.nemesis-project.eu) wird ein Wasserstoffgenerator (50 Nm3/h) auf Basis von Diesel und Biodiesel entwickelt. Am DLR Stuttgart werden im Rahmen des Projektes grundlegende experimentelle Untersuchungen zur Dampfreformierung von Diesel und Biodiesel durchgeführt. Diese werden ergänzt durch eine modelltechnische Abbildung des Gesamtsystems mit Aspen Plus ®

High temperature thermochemical heat transformation based on SrBr2

Currently, state of the art working fluids of conventional heat pumps are limited to maximum output temperatures of 140 °C, and thus cannot fulfill the need for high temperature heat pumps in industrial applications. This is why thermochemical reaction systems have come into the focus of interest: they offer the potential of high temperature energy storage and heat transformation, e.g. by making use of the pressure dependency of a gas-solid reaction. These reactions can in general be described by the following equation: A(s) + B(g) ⇌ AB(s) + ΔRH. Variation of the pressure of the gaseous reactant B results in a temperature shift of the exothermic reaction. In this way, the exothermic reaction (energy output) can be performed at higher temperatures than the endothermic reaction (energy input). In this contribution, the thermodynamic principle of thermally driven heat transformation and its main difference with respect to conventional or sorption based heat pumps is outlined. The scope of this work is the potential of the SrBr2–H2O system as a possible candidate for thermochemical heat transformation. Constraints for a suitable reactor geometry and the possibility to combine thermal upgrade and thermal energy storage into one system are analyzed. Experimental results from a laboratory scale test reactor (~ 1,000 g) support the proof of concept of heat transformation in the region of 200 °C

Reaktorkonzept zur Untersuchung der reversen Wassergas-Shift Reaktion (rWGS) bei Hochtemperatur und erhöhtem Druck

Motivation Um die Netto-THG-Emissionen zu senken, werden derzeit verschiedenste Pfade zur Nutzung erneuerbarer Ressourcen im Energie- und Transportsektor diskutiert. Es ist davon auszugehen, dass in der Luftfahrt, zumindest kurz- und mittelfristig, flüssige Kohlenwasserstoffe nicht substituierbar sein werden. Eine Möglichkeit zur Erzeugung von erneuerbarem Flugturbinentreibstoff ist der Power-to-Liquid Prozess. Eine Verfahrensvariante dieses Prozesses stellt die CO2-Aktivierung mittels reverser Wassergas-Shift Reaktion (rWGS) mit anschließender Fischer-Tropsch Synthese (FTS) dar. Herausforderungen Da die FTS bei erhöhtem Druck (25 bar) betrieben wird, scheint es aus technischer und ökonomischer Sicht sinnvoll die Syngasstufe ebenfalls bei erhöhtem Druck zu untersuchen. Aufgrund der leichten Endothermie der rWGS liegt das optimale Betriebsfenster im Bereich von 700-900 °C. Voruntersuchungen haben gezeigt, dass die Reaktion durch Kontakt mit Edelstahl oder Hochtemperaturstahl katalysiert wird. Um die Reaktion an einem Katalysator untersuchen zu können, muss die Hochtemperaturzone (bis 900 °C) deshalb inert sein und der Reaktor muss dem erhöhten Druck (bis 25 bar) standhalten. Ergebnisse Im Rahmen des Beitrags wird ein Reaktorkonzept vorgestellt, das es ermöglicht die rWGS unter den genannten Bedingungen zu untersuchen (siehe Abbildung). Außerdem sollen erste experimentelle Ergebnisse vorgestellt werde

Experimental investigation of the reverse water-gas shift reaction at high temperature and elevated pressure

To reduce the net greenhouse gas emissions to zero (COP21), several possible routes to utilize renewable sources in the energy and transport sector are discussed and investigated lately. For the air transport sector it seems likely that it will still rely on hydrocarbons in the near future. One possible process to synthesize these hydrocarbons is the power-to-liquid process. Two main steps in this process are the CO2-activation (syngas production via reverse water-gas shift reaction) and the subsequent Fischer-Tropsch process. In context of producing liquid fuels via Fischer-Tropsch, the syngas production unit has to be operated at elevated pressure up to 25 bar in order to run the process at a constant pressure level. The syngas production is an endothermic reaction which improves with higher reaction temperatures (700 °C-900 °C) due to the state of equilibrium. However, most previous studies focus on the investigation of the reverse water-gas shift reaction (rWGS) at atmospheric pressure. The pressure dependency of side reactions, like methane and carbon formation, leads to different equilibrium concentrations and therefore the pressure influence cannot be neglected. Then again, studies conducted at elevated pressure use stainless steel tubes as reactor tubes, which catalyze the reaction due to their nickel content. Therefor these experimental results combine both catalytic pathways which cannot be separated easily. In this study a novel reactor set-up is introduced, which enables to investigate heterogeneously catalyzed reactions at high temperature and elevated pressure. This setup consists of a glass tube in which the catalyst is inserted. Therefor only gas phase and catalytic reaction at the catalyst are likely to occur. The glass tube is surrounded by an electric heating wire to heat the gas to reaction temperature. On both ends of the glass tube the temperature has to be far lower than 700 °C because otherwise the wall catalysis at the stainless steel tube would falsify the results. The electric wire is wrapped in glass wool in order to isolate the reaction chamber and to prevent the outer pressure stressed stainless steel tube from high temperature impact

Direct steam reforming of diesel and diesel–biodiesel blends for distributed hydrogen generation

Distributed hydrogen generation from liquid fuels has attracted increasing attention in the past years. Petroleum-derived fuels with already existing infrastructure benefit from high volumetric and gravimetric energy densities, making them an interesting option for cost competitive decentralized hydrogen production. In the present study, direct steam reforming of diesel and diesel blends (7 vol.% biodiesel) is investigated at various operating conditions using a proprietary precious metal catalyst. The experimental results show a detrimental effect of low catalyst inlet temperatures and high feed mass flow rates on catalyst activity. Moreover, tests with a desulfurized dieselebiodiesel blend indicate improved long term performance of the precious metal catalyst. By using deeply desulfurized diesel (1.6 ppmw sulfur), applying a high catalyst inlet temperature (>800 °C), a high steam-to-carbon ratio (S/C = 5) and a low feed mass flow per open area of catalyst (11 g/h cm2), a stable product gas composition close to chemical equilibrium was achieved over 100 h on stream. Catalyst deactivation was not observed