1,720,975 research outputs found
Performance assessment of a 15 kW Micro-CHCP plant through the 0D/1D thermo-fluid dynamic characterization of a double water circuit waste heat recovery system
No full textThe exploitation of renewable energy sources and the use of primary energy saving techniques have been
recognized as key solutions to face climate changes. The consequent energy policies are pushing the
transition from a centralized power generation system to a distributed polygeneration system able to
meet simultaneous heating, cooling and electricity demand. However, small scale polygeneration plants
do not ensure any primary energy and cost saving without a proper sizing and operation of the plant.
Furthermore, a flexible configuration of the waste heat recovery system (WHRS) adopted for polygeneration
purposes can be equally important. Therefore, starting from the experimental data concerning
a 15 kW micro-CHP plant previously designed and prototyped, the paper addresses the
performance assessment of a CHCP plant configuration based on the same basic engine-electric generator
system through the 1D thermo-fluid dynamic characterization of an alternative double water circuit
WHRS. This configuration, delivering thermal power at different temperature level, could be useful to
meet thermal and cooling demand from different user or when seasonal energy demand occurs. This
paper also provides an effective approach for the design of WHRS which are capable to ensure a
reasonable matching between the temperature level required by the user and that provided by the plant.
In this way, being the energy saving dependent on the thermal power recovered and actually exploited,
and so on the temperature level which characterizes the user's heat demand, primary energy savings are
more easily achievable even when small scale polygeneration applications are considered. Results shows
the possibility of supplying an absorption chiller and obtaining a coolling capacity of about 10.5 kW from
the resulting CHCP plant configuration
Development of a 1 kW Micro-Polygeneration System Fueled by Natural Gas for Single-Family Users
No full textThe use of primary energy saving techniques and renewable energy systems has become mandatory to tackle the effects of global temperature rise. As a result, a transition is taking place from centralized energy generation to distributed energy generation. Starting from the experience concerning a 15 kW micro-CHP plant previously designed at DII, this paper addresses the development of a 1 kW micro-CHP system fueled by natural gas for single-family users. Specifically, the paper presents a wide experimental investigation aimed at optimizing performance and emissions of a small scale two-stroke spark ignition gasoline engine properly modified to be fueled with natural gas to make the engine more suitable for cogeneration purposes. The described activity was carried out at the DII of the University of Naples Federico II. Rigorous laboratory tests were conducted with the engine in order to characterize both gasoline and CNG operation in terms of brake mechanical power, overall efficiency and exhaust gas emissions in different operating regimes. Furthermore, several physical quantities associated with the engine operation were measured through several sensors in order to optimize performance and emissions achieved when the engine is fueled with CNG. In particular, dynamic pressure variations inside the cylinder were measured and analyzed to evaluate the effect of the adopted fuel on the optimum ignition-timing angle and cyclic dispersion
SpaceHuman: A soft robotic prosthetic for space exploration
Full text linkThe project focuses on the human centered design approach for aiding crewed space operations in microgravity. The key element is enhancing the floating experience, while enabling humans to adapt in microgravity environments. The metaphor of the undersea world inspired the design of a body extension that can complement the interiors of Zero-G habitats. The analysis of the unique seahorse's tail structure became the insight into the overall biomimetic design. In fact, a seahorse tail enables movement, gripping and protection to the seahorse while floating. SpaceHuman is an additive prosthetic that can move around the body to grasp objects and handles in microgravity, protecting the wearer from injuries that might occur while floating in a confined habitat, while providing an adaptable and kinematically stable base. SpaceHuman has been designed through different computational design methods, to simulate its behavior in microgravity, and has been worn and tested on a Zero-G flight
Crank Mechanism Friction Modeling for Control-Oriented Applications
No full textPurpose of the study is to improve the base calibration process of engine Electronic Control Unit (ECU) through the use of 0D-1D CFD engine models coupled to a physics-based model of the engine frictions. Once reliably calibrated, the overall engine model can be used to reduce the experimental effort of the base calibration process. In this paper a specific methodology based on the vector optimization approach is also proposed in order to reliably calibrate the numerical friction model. This methodology was applied to an engine crank mechanism model adopting specific friction sub models, generated using a multibody approach. The vector optimization problem was solved using experimental engine friction data measured in 13 operating conditions: the comparison between numerical results and experimental data highlights how the proposed modelling approach can be effectively adopted to simulate the friction losses, since the average error is about 5%. Therefore, coupling reliably calibrated friction models to 0D-1D CFD engine models could be useful to improve the estimation of the main engine quantities to be used in the base calibration process
Energetic Performance Assessment of Different CHP-CHCP Configurations of a 15 kW Micro-CHP Plant through 1D Thermo-Fluid Dynamic Simulation
No full textThe exploitation of renewable energy sources and the widespread adoption of primary energy saving techniques have been recognized as key solutions to face climate changes. These solutions are pushing the transition from a centralized power generation system to a distributed polygeneration system which is suitable to meet simultaneous heating, cooling and electricity demand. However, small scale polygeneration plants do not ensure effective primary energy and cost savings without a proper sizing and operation of the plant. Furthermore, a customized configuration of the waste heat recovery system adopted for cogeneration purposes can be equally important. Therefore, starting from the experimental data concerning a 15 kW micro-CHP plant previously designed and prototyped, the paper addresses the energetic characterization of different CHP-CHCP configurations of the same plant through 1D thermo-fluid dynamic simulation. In particular, as the achievable primary energy saving depends on the thermal power recovered and actually exploited, and so on the temperature level which characterizes the user's thermal demand, three different configurations of the waste heat recovery system were analyzed and the plant energetic performance estimated. Each configuration, delivering thermal power at different temperature level, could be useful to meet thermal and cooling demand from different user. This paper also provides useful results for the design of CHP systems which are capable to ensure a reasonable matching between the temperature level required by the user and that provided by the plant. In this way, primary energy savings are more easily achievable even when a micro-CHP application is considered
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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