1,721,072 research outputs found
Advancing Water Vapor Based High-Temperature Heat Pumps: Extending Temperature Ranges and Industrial Applications
No full textThe additional multi-compression stage utilizing split flow has been introduced to enhance the supply temperature of the existing high-temperature heat pump (HTHP) system to 250°C. Under specific temperature boundary conditions, the HTHP without split flow maintains a constant COP regardless of the mass flow rate. However, as the split ratio increases, the COP decreases due to the increased compressor power consumption exceeding the heat capacity enhancement from the additional stages.
Assuming optimized operating strategies, the advanced HTHP with additional stages demonstrates high potential to extend the application range and simultaneously meet multiple industrial process heat demand by increasing the supply temperature
Opportunities for high-temperature heat pumps as grid flexibility providers
Full text linkstatus: Published onlin
Transient analysis and control of a Brayton heat pump during start-up
Full text linkThis paper aims to investigate the transient response of the DLR's CoBra prototype, an innovative Brayton-cycle heat pump intended to provide heat above 250 °C and currently under commissioning at the DLR facility in Cottbus, Germany. First, a comprehensive transient thermodynamic model of the system is developed, accounting for heat exchangers and piping thermal inertia. Furthermore, a control logic is presented that ensures safe operation throughout off-design conditions and start-up manoeuvres. In particular, several control parameters are considered to avoid potential operational issues, such as critical temperature gradients, compressor surge, and critical mechanical vibration phenomena due to resonance. The performed simulations aim to reduce start-up time and energy consumed during start-up. Results show that with the help of the described controller, the system can reach design operation via a transient trajectory safely and quickly. Therefore, the capability of the CoBra prototype to flexibly supply high-temperature heat is demonstrated
Interoperability specifications and an automatic validation tool as a key factor for the support of a repository ecosystem
Full text linkPresentation at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014General Track Papers and PanelsWe present a) a set of common interoperability requirements specifications and b) an automatic validation tool that can validate individual repositories for conformance with the aforementioned requirements. The automatic validation tool, runs as a service, and it is designed to support the validation and aggregation of millions of items. The validator service, offers advanced functionality such as metadata-level and digital item-level validation, standards based results reporting and content aggregation capabilities. These interoperability specifications and the validation tool are implemented for the support of a large scale digital culture programme, which is under implementation, with millions of items expected to be validated. The combination of the specifications and the validation tool can form the backbone of a repository ecosystem.Houssos, Nikos (EKT/NHRF, Greece)Stathopoulos, Panagiotis (EKT/NHRF, Greece)Stathopoulou, Ioanna-Ourania (EKT/NHRF, Greece)Banos, Vangelis (EKT/NHRF, Greece)Georgiadis, Harris (EKT/NHRF, Greece)Sachini, Evi (EKT/NHRF, Greece
Galen's Contribution to Head and Neck Surgery
No full textAuthor(s) Pre or Post Print OnlyThe historical relevance of Galen has always been very high and his works have exerted a profound influence on medical thought for more than 1,300 years. This could be the main reason why his surgical expertise is often neglected. This brief study focuses on the contribution of this distinguished physician to head and neck surgery and it shows that Galen's surgical experience is well documented in his work
Film Cooling Modeling in a Turbine Working under the Unsteady Exhaust Flow of Pulsed Detonation Combustion
Full text linkPressure gain combustors (PGCs) have demonstrated significant advantages over conventional combustors in gas turbine engines by increasing the thermal efficiency and reducing the pollution emission level. PGCs use shock waves to transfer energy which contributes to the increase in outlet total pressure. One of the major obstacles in the actual implementation of PGCs in the gas turbine cycle is the exploitation of the highly unsteady flow of the combustor outlet with the downstream turbine. Because of the higher outlet temperature from the PGCs, the turbine blade cooling becomes essential. Due to the highly fluctuating unsteady flow of PGCs, 3D CFD simulation of turbines becomes very expensive. In this work, an alternative approach of using a 1D unsteady Euler model for the turbine is proposed. One of the novel aspects of this paper is to implement the turbine blade cooling in the unsteady 1D Euler model. The main parameters required for the turbine blade cooling are the cooling air mass flow rate, temperature, and pressure. Due to the introduction of coolant flow, the blades are no longer adiabatic and the mass flow rate across the turbine is not constant. Comparing the 1D Euler results against zero-dimensional calculation and 3D CFD approach showed a very good match for both steady and unsteady simulations confirming the applicability of the 1D method
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
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