106 research outputs found
Shear and Anchorage Behaviour of Fire Exposed Hollow Core Slabs
No full textHollow core (HC) slabs are made of precast concrete with pretensioned strands. These slabs are popular as floor structures in offices and housing. At ambient conditions, the load bearing capacity can be dominated by four different failure modes, i.e. flexure, anchorage, shear compression and shear tension. As the economic production process does not allow for the inclusion of mild reinforcement, the slabs rely on the tensile strength of concrete for the shear and anchorage capacity. When exposed to a fire, the HC slabs have to maintain their load bearing and separating function for a certain time in order to facilitate the fire fighting actions and to provide sufficient time for the users of the building to escape and for rescue teams to search the building. Current design codes consider only flexural failure, while fire tests carried out in the past showed that the other failure modes can dominate the fire behaviour as well. As a result, design codes might overestimate the actual performance of fire exposed HC slabs. However, the experiments might represent a worst case compared to the practice. At least, fatalities caused by a premature collapse of fire exposed HC slabs, have never been reported up to the author's knowledge. Because there is a lack of fundamental understanding of the shear and anchorage behaviour, an optimum design between safety and economics can yet not be achieved. The objective of the research presented in this thesis is to gain a basic understanding of the shear and anchorage behaviour of fire exposed HC slabs and to develop FE models to predict this behaviour. With the models, design measures to improve the behaviour can be evaluated. The field of application is limited to HC slabs in accordance with the European product standard prEN 1168 [1197], exposed to standard fire conditions and simply supported on rigid supports like walls. The results are on the safe side for HC slabs with restraining support conditions.Civil Engineering and Geoscience
Investigation and Development of Tailor-Made Core-Shell Hard Carbon Materials to be used as Negative Electrodes in Sodium Ion Batteries
No full textThe current strong interest in electromotive mobility and the need to transition to an energy grid with sustainable energy storage has led to a renewed interest in sodium ion batteries (SIBs). Hard carbons are promising candidates for high-capacity negative electrode materials in SIBs. Their high capacities, however, are often accompanied with high irreversible capacity losses during the initial cycles.[1]
The goal of this project is to use analytical techniques to establish a correlation between the structure and the capacities of hard carbons. This has previously been difficult, in part because the sodium storage mechanism is not stoichiometric and due to the disordered structure of hard carbons.
Large irreversible capacities associated with hard carbons are often in contradiction to the experimentally determined low surface area of the sample material.[1] A better understanding of the structure-property relationship should enable quantification and understanding of the potential of hard carbon materials for SIBs.
Our approach is to explore whether a core-shell structure can separate sodium storage and solid electrolyte interphase formation so that storage capacity and irreversible losses can be investigated separately. The synthesis of a selection of porous carbon structures serving as the core material, will be attempted. Simultaneously, sodium-conducting shell structures will be developed to allow for separation of sodium ions and electrolyte molecules. Subsequently the combination of core and shell materials will be undertaken. These anodes should enable high capacities accompanied with low irreversible capacity due to optimized solid electrolyte interphase formation
Data management technology driven and sustained by the eResearch community
No full textThe technology of iRODS (Integrated Rule-Oriented Data System) was first funded by a government grant in 1995 and subsequently developed by several academic institutions that saw data management as a growing problem. The code was open-source from the beginning but the development was done on a volunteer basis. It became clear as the scale of the problem grew that a more formal solution was required. The iRODS Consortium was founded in 2013 as a group of professional developers based at the University of North Carolina at Chapel Hill. This group is sustained by a membership model and, today, the iRODS Consortium has over 30 members spanning the world. These members are both academic and commercial, but they all have similar requirements in their institutions. Today, iRODS technology is a product of both the developers and the community. Code is contributed and regular community meetings are held to highlight the needs of all of the members. Working groups are formed to address the changing requirements of the members as the scale and complexity of data generation and maintenance changes dynamically over time. Decisions regarding the disposition of data can now be automated and based on metadata which can change depending on citation or usage. Data can be automatically gathered from sensors and instruments, sorted by metadata, processed, and the products distributed or published in completely automated workflows.The iRODS community is comprised of academic and commercial researchers but the discourse is active and the resultant product is based upon consensus. Today, worldwide, FAIR discovery and directed dissemination of eResearch information is being accomplished in sites controlling tens of petabytes of data with this open-source technology.ABOUT THE AUTHOR Dave Fellinger is a Data Management Technologist and Storage Scientist with the iRODS Consortium. He has over three decades of engineering experience including film systems, video processing devices, ASIC design and development, GaAs semiconductor manufacture, RAID and storage systems, and file systems. He attended Carnegie-Mellon University and holds patents in diverse areas of technology.</p
Development of tailormade core-shell hard carbon materials as anode materials in sodium ion batteries
No full textThe current strong interest in electromotive mobility and the need to transition to an energy grid with sustainable energy storage has led to a renewed interest in sodium ion batteries (SIBs). Hard carbons are promising candidates for high-capacity negative electrode materials in SIBs. Their high capacities, however, are often accompanied with high irreversible capacity losses, during the initial cycles.[1]
The goal of this project is to synthesize carbon materials using different zeolite templates to obtain electrode materials that feature a defined and adjustable pore structure. A better understanding of the structure-property relationship by investigating porosity-tailored anode materials, should enable quantification and understanding of the potential of hard carbon materials for SIBs.
Furthermore, a goal is to explore whether a core-shell structure can separate sodium storage and solid electrolyte interphase formation allowing the independent investigation of storage capacity and irreversible losses.
Health care access among deaf people: Table 1
No full textAccess to health care without barriers is a clearly defined right of people with disabilities as stated by the UN Convention on the Rights of People with Disabilities. The present study reviews literature from 2000 to 2015 on access to health care for deaf people and reveals significant challenges in communication with health providers and gaps in global health knowledge for deaf people including those with even higher risk of marginalization. Examples of approaches to improve access to health care, such as providing powerful and visually accessible communication through the use of sign language, the implementation of important communication technologies, and cultural awareness trainings for health professionals are discussed. Programs that raise health knowledge in Deaf communities and models of primary health care centers for deaf people are also presented. Published documents can empower deaf people to realize their right to enjoy the highest attainable standard of health
Core-Shell Materials as Advanced Anodes for Sodium Ion Batteries
No full textThe current imperative to shift towards an energy grid equipped with sustainable energy storage solutions has caused a renewed interest in sodium-ion batteries (SIBs). Hard carbons (HCs) are a promising option high-capacity anode materials in SIBs. Nevertheless, their elevated capacities frequently come at the cost of experiencing substantial non-reversible initial capacity losses.
Commonly, significant losses are associated with irreversible reactions, such as the creation of the solid electrolyte interphase (SEI), that occur during the initial sodium insertion in HC-materials. Intriguingly, high values of irreversible capacity are often found for samples with experimentally determined low specific surface area.[1] A more comprehensive understanding of the structure-property relations is essential for quantifying and grasping the potential of hard carbon materials in sodium-ion batteries (SIBs). Thus, the objective is to employ analytical methods to establish a link between the structure and the electrochemical attributes of HC materials. This has been a challenge, partly due to the non-stoichiometric nature of the sodium storage mechanism and the disordered structure of HCs.
To address the challenges mentioned above, our approach is to explore whether a core-shell structure can separate sodium storage and SEI-formation. This way, we can investigate and fine-tune storage capacity and irreversible losses, independently. The strategy involves the synthesis of various porous carbon structures to serve as the core material and their combination with sodium-conductive structures to core-shell materials. Herein, we will present different synthesis routes towards tailor-made carbon core materials. Moreover, different coatings concepts will be introduced, and the electrochemical performance of the core and core-shell materials compared. To elucidate the storage mechanism, the results of advanced analytical methods such as operando NMR and SAXS will be presented. Generally, these core-shell anodes promise to enable high capacities accompanied with low irreversible losses due to optimized SEI-formation
Oracle Corporation 1-2
No full textDuring these sessions, Tom Kyte of Oracle Corporation will cover the following topics:# The Tools Tom uses, # The Top 5 things done wrong over and over again, # Building test cases, # Oracle 10g "cool features" Speaker Bio:Tom Kyte is the Vice President, Core Technologies for Oracle Government, Education and Healthcare. Before starting at Oracle, Tom Kyte worked as a systems integrator building large-scale, heterogeneous databases and applications, mostly for military and government customers. He spends a great deal of his time working with the Oracle database and, more specifically, working with people who are working with the Oracle database. Tom Kyte is the Tom behind the AskTom web site, answering people's questions about the Oracle database and its tools (http://asktom.oracle.com/). He is also the author of the AskTom column in http://www.oracle.com/technology/oramag/oracle/current.html Oracle Magazine, and the author of Expert One-on-One Oracle (Apress, 2003), Beginning Oracle Programming (Wrox Press, 2002), and Effective Oracle by Design (Oracle Press, 2003). These are books about the general use of the Oracle database and how to develop successful Oracle applications
Developing Core-Shell Carbon Materials to Link Porosity Features to Sodium Storage Capacities
No full textPorous carbon materials play an important role for energy storage and conversion. One (re-)emerging research field is the ability of porous carbons to store sodium metal ions. Current results shows that internal pores – hence, pores which are not accessible for the electrolyte – allow to store large amounts of sodium at low potentials, yielding high energy sodium-ion battery (SIB) anodes.
The common synthesis approach to gain carbons with internal pores involves the pyrolysis of a non-graphitizing precursor, resulting in a so-called hard carbon (HC). However, HC-materials frequently show substantial non-reversible initial capacity losses. Commonly, significant losses are associated with the creation of the solid electrolyte interphase (SEI) on the carbon’s surface that occurs during the initial sodium insertion. Intriguingly, large irreversible capacities are often found for samples with experimentally determined low specific surface area.[2] A more comprehensive understanding of the structure-property relations is essential for quantifying and grasping the potential of carbon materials in SIBs. However, the typical synthesis methods do not allow to individually tune the storage properties – mainly connected to the internal properties of the carbons – and the SEI-formation – primarily related to the surface properties. Hence, the objective of the present work is to develop a synthesis route which tackles this challenge.
Herein, the main approach is to develop tailor-made core-shell carbon materials consisting of a highly porous carbon core and a quasi-non-porous carbon shell. For the core, two strategies are pursued: A) microporous carbon materials with varied porosity, however, similar chemistry, and B) microporous carbons with tuneable chemistry, but similar porosity. Approach A involves the selection of commercially available activated carbons (ACs). Strategy B is based on the modification of the chemical composition (i.e., amount and type of N-sites) of zeolitic imidazolate framework (ZIF-8) derived carbons. In both cases, the shell is realized by chemical vapour deposition (CVD). Different analytical methods, e.g., powder XRD, gas physisorption (N2, Ar, CO2), XPS, and SAXS are used to thoroughly characterize
morphological and chemical features of the core as well as of the core-shell carbons. These features are linked to the electrochemical characteristics of the materials.
After CVD-coating, all materials show a significant reduction in detectable surface area (up to a factor of up to 190x) by N2-physisorption. The coating technique is successfully applied to a range of AC-materials, enabling to link porosity features to Na-storage behavior. For the best performing AC-based material, the reversible capacity is increased from ~140 mAhg-1 to ~400 mAhg-1 while irreversible capacity is decreased from ~640 mAhg-1 to ~90 mAhg-1.
The results of the coated ZIF-derived carbon reveal that a higher nitrogen content leads to a greater capacity in the sloping region, but to a lower capacity in the plateau region of the voltage profile.
Generally, core-shell carbon anodes promise to enable high capacities accompanied with low irreversible losses
Designing Core-Shell Carbon Materials for High-Performance Sodium-Ion Battery Anode
No full textIncreasing prices of the material basis for lithium-ion batteries caused by limited production capacities or resource abundance has led to a renewed interest in sodium ion batteries (SIBs). Therein, amorphous disordered carbons such as hard carbons (HCs) are promising candidates for high-capacity negative electrode materials in SIBs. Their high capacities, however, are often accompanied with high irreversible capacity losses during the initial cycles,[1] while low initial losses are mostly accompanied with moderate capacities.[2] In our research we are aiming at morphologically improved carbons to reduce irreversible losses using a core-shell concept, leading to spacial separation of the reversible storage and unfavorable side reactions.[3]
We investigated different methods to obtain core-shell structures with improved interfaces to restrict SEI formation to the external particle surface, while leveraging the Na storage potential of porous carbon core materials. With a simple and scalable chemical vapour deposition we obtained a 190-fold decrease in surface roughness, resulting in drastically reduced first cycle losses. Interestingly, the sodiation capacity at the same time increased to 400 mAh/g revealing the interference of excessive SEI formation with the storage process within the particles
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