1,721,252 research outputs found
Electrochemical hydrogen detection in DONES loop materials
No full textThe radiation-induced degradation of materials in fusion systems is planned to be investigated in IFMIF-DONES (International Fusion Materials Irradiation Facility - DEMO Oriented NEutron Source), where fast neutrons are produced by a reaction of deuteron-beams with a liquid lithium target. A by-product as critical impurity is hydrogen, which might affect the reliable and safe operation of the IFMIF-DONES loops. Therefore, an important issue is the measurement and control of the hydrogen impurity concentrations in liquid lithium. Initially, a practically applicable direct measurement of hydrogen concentrations in lithium facilities did not exist. However, one promising approach to manage this issue is based on the electrochemistry of the DONES materials The developed Electro-Chemical Hydrogen Sensor for Liquid Lithium (ECHSLL) allows the measurement of the electromotive Force (EMF) between a reference materials system and the loop lithium melt, and thus the monitoring of the hydrogen impurity concentrations. This article will show backgrounds of non-metallic impurities in liquid metal materials and the specific material stabilities within DONES. Liquid lithium is a very reactive material. Therefore critical issuesareviable materials compatibilities, the interactions with hydrogen and the transport behaviour of H-ions in electrolytes at the applied temperatures. Further issues are also the syntheses of the electrochemical materials, as hydrogen conducting electrolytes, reference electrode systems and the different procedures (heat treatments and conditioning steps). The tests showed the functionality of the developed H-sensor. Beyond that, the used material combinations exhibited reliable behaviour in melts under harsh conditions. Hence, the most critical aspect (stability of the sensor materials in the Li-melt) has been resolved by using niobium sensor heads. The observed experimental EMF potentials are in good accordance compared with calculated models, also in long-time experiments
Detection of hydrogen as impurity in liquid lithium: An electrochemical hydrogen-sensor for IFMIF-DONES
Full text linkIFMIF-DONES, the International Fusion Materials Irradiation Facility - DEMO Oriented NEutron Source, is the planned facility in Granada/Spain for fusion materials investigations using neutron irradiation in the scale of DEMO-oriented energies. This irradiation is generated by the interaction of deuteron beams with a liquid lithium flow-target system, containing huge amounts of this very reactive alkaline-metal. An important and critical issue during the operation of IFMIF-DONES is the enrichment of dissolved impurity components in the Li-melt and in the liquid melt concerning reactivity, corrosivity and radiation hazards. In the case of hydrogen, there is the danger of H-introduced embrittlement of the loop structure components as well as effects and hazards of the radioactive tritium. The application of liquid lithium in the scope IFMIF-DONES unconditionally hence requires a suitable impurity control. Regarding this subject, an electrochemical sensor for a continuous hydrogen monitoring is being developed in the frame of an international EUROFusion-WPENS task. This sensor was designed as single-rod-measuring-cell with niobium as the relevant membrane-material and a hydrogen conducting electrolyte. Potentials (Electro-Motive Force EMF) are being measured between the Li melt and a reference electrode by voltmeters with high impedances and can easily converted into H concentrations. Long-term tests (campaign-units of several hundred hours) in stagnant Li-melts with different sharply controlled hydrogen concentrations showed, that the sensor fulfills the requirements of chemical and mechanical stability and functionality also under harsher conditions (temperatures up to 500 °C). The obtained results and operational experiences will be discussed, e.g., concerning application windows, reproducibility and calibration needs. Additionally, recommendations will be outlined for upgraded systems and future qualification needs
New developments of hydrogen impurity online-monitoring in liquid lithium of IFMIF-DONES
Full text linkOn the way to future nuclear fusion power plants, the International Fusion Materials Irradiation Facility (IFMIF) – DEMO Oriented Neutron Source (DONES), is an important key element between ITER and DEMO to study before the influence of DEMO-neutron irradiation on foreseen fusion materials. The core of DONES, currently under construction near Granada, Spain, is based on a circuit containing liquid lithium at elevated temperatures acting as a functional material for the (d,n)-Li reaction in a materials test cell. In addition to this actual function of DONES, there are important aspects of maintenance in which hydrogen isotopes are generated under operating conditions and dissolved in this aggressive and very reactive alkali metal. This implies strong unfavourable effects on the applied structural materials, e.g. hydrogen embrittlement and others. To counteract these unfavourable effects, endangering the safe operation, an Impurity Control System (ICS) is an integral part of the DONES instrumentation. As part of the tasks of the European Neutron Source (ENS) to develop redundant systems for monitoring impurities, a special sub-task was defined for the development of an electrochemical H-sensor for concentrations in liquid lithium, ECHSLL. It is determined by detecting the electrical potentials of the lithium melts compared to a standard Li-based chemical reference system. This allows an inherent material property to be directly correlated (i.e. through appropriate electrochemical instrumentation) with chemical concentration values. This article presents important advancements in the applied ECHSLL technique, such as improving laboratory measurements from stagnant conditions to dynamic and realistic flow conditions of the liquid lithium material, as well as appropriate approaches to overcome the challenges in distinguishing the hydrogen isotopes by ECHSLL system (protium and deuterium among given laboratory conditions)
Development of an electrochemical sensor for hydrogen detection in liquid lithium for IFMIF-DONES
No full textHydrogen impurities in liquid lithium have a drastic disadvantageous impact on the used structural materials. Such a problem might occur also in the planned materials testing facility IFMIF-DONES, where hydrogen isotopes are produced by a reaction of a deuteron-beam with a target of liquid lithium. Therefore, the operation of such a Li-system requires the measurement of hydrogen (seen as impurity in the Li-melt) and the control of hydrogen removal. It is one of the excellences of the tool Electrochemistry to measure dissolved species over wide ranges of concentrations in real-time conditions. This presentation will present the physical background of determining non-metallic impurities in molten metals by measuring electrochemical potentials, outlining the development of such an H-sensor system and the transformation by Nernst correlation into concentration values. Additionally, liquid lithium is a very reactive melt, thus material compatibility is an essential topic for the developments of a durable sensor. Based on these issues a sensor design for measuring hydrogen in liquid lithium was realized under consideration of all physical, chemical and metallurgical aspects, including the successful manufacturing of the sensor as a first prototype and a further first production series. The outlook will also deal with the possibility of measurements of different hydrogen isotopes
Log<sub>2</sub> fold-changes for fecal mRNA gene expression in calves with scours (n = 17 Holstein, n = 21 Jersey) or systemic enteritis (n = 6 Holstein, n = 7 Jersey) at any point from enrollment until the day 10 differential gene expression (DGE) sample as compared to consistently healthy calves of the same breed(s) (n = 20 Holstein, n = 13 Jersey).
No full textLog2 fold-changes for fecal mRNA gene expression in calves with scours (n = 17 Holstein, n = 21 Jersey) or systemic enteritis (n = 6 Holstein, n = 7 Jersey) at any point from enrollment until the day 10 differential gene expression (DGE) sample as compared to consistently healthy calves of the same breed(s) (n = 20 Holstein, n = 13 Jersey).</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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