1,720,997 research outputs found
Hierarchizing Energy Saving Strategies in Wine Industry by Advanced Modelling of Chilling Units Operation
No full textWineries are energy intensive industries and in order to make the production process more sustainable, solutions for an efficient use of energy should be implemented. Large surveys conducted in the wineries sector have highlighted the importance of performing accurate energy audits and have identified in the installation of efficient cooling/refrigeration systems the most promising solutions in a variety of cases. Unfortunately, the savings achieved by such energy efficient solutions is often calculated by highly simplified approaches, which do not take into consideration the actual operating conditions of the equipment (highly variable on a seasonal and daily basis). In this paper a systematic and novel procedure is presented, aimed at developing reliable cooling load profiles for refrigeration and air-conditioning and identifying to what extent more efficient chilling units could countribute to reduce the electricity consumption. With this purpose, the use of Seasonal Energy Efficiency Ratios is critically analyzed, proving the need for seasonal indicators customized on the actual operating conditions of the chillers. The proposed method is applied to a winery producing still red and white and sparkling wines, for which only aggregated energy consumption data are available
An integrated approach based on Life Cycle Assessment and Thermoeconomics: Application to a water-cooled chiller for an air conditioning plant
No full textA large number of methods for energy systems analysis were developed in the last decades, aimed at acquiring an in-depth understanding of plant performances and enabling analysts to identify optimal design and operating conditions. In this work an integrated approach based on Life Cycle Assessment and Thermoeconomics is proposed as a method for assessing the exergo-environmental profile of energy systems. The procedure combines the capabilities of these two techniques, to account simultaneously for aspects related to thermodynamics of energy conversion processes and to the overall impacts along the plant life cycle related to other phases, i.e. from raw material extraction to the disposal of facilities. The capabilities of the method are illustrated by applying it to a water-cooled vapor compression chiller. After developing an accurate analysis of plant design and bill of materials of the chiller, the exergo-environmental profile was obtained. Then, the method was used as a decision support tool by considering a number of scenarios concerning possible design alternatives, context conditions and levels of maintenance. Results showed that the exergo-environmental performance of the chiller is highly sensitive to the electricity generation mix, which influences the trade-offs between the energo-environmental impacts related with plant operation and constructio
Performance of FQDB, a Fair MAC protocol for Dual Bus Networks
No full textThe authors present the delay-throughput performance of a new MAC protocol, the fair queue dual bus (FQDB), which relieves dual bus networks from the unfairness problems exhibited by the basic version of the distributed queue dual bus (DQDB) standard. The protocol considered is absolutely fair in bandwidth sharing and does not imply any change in the DQDB transmission system. It retains all the positive features of DQDB including simplicity, robustness, flexibility, 100% bandwidth utilization, and little slot access delay at light load. Comparisons to DQDB with the bandwidth balancing mechanism show that the FQDB delay-throughput performance was always superior while its implementation complexity was comparabl
Adaptive access control of multiple traffic classes in ATM networks
No full textAn admission control and bandwidth allocation strategy is applied to several traffic classes entering an ATM (asynchronous transfer mode) network through a statistical multiplexer. At the call level, incoming virtual calls are either accepted or refused on the basis of a class-selective control rule designed to maintain a certain grade of service. Each class is assigned a buffer partition and a virtual capacity share, which affect the parameters of the acceptance controller. Buffer space is assigned statically with an offline procedure; on the other hand, bandwidth shares are periodically recomputed online at the cell level, by means of the (parametric) constrained minimization of a cost function, which takes cell loss probability and refused traffic into account. These quantities are computed by observing the number of refused, accepted, and active (i.e., possibly generating bursts) calls within the previous decision interval, and are assumed to be slowly varying with respect to the cell dynamics. In turn, the results of the optimization are used to adaptively adjust the parameters of the access controller
FairQDB: A New Simple and Optimal Access Scheme for Dual Bus Networks
No full textThe authors present a new access control scheme for dual bus networks which is absolutely fair in bandwidth sharing and can replace the DQDB access protocol without changes in the transmission system apart from the protocol machine. The mechanism retains all the positive features of DQDB including simplicity, robustness, flexibility, 100% bandwidth utilization and zero access delay at very low load. In addition, it can be set to provide a bandwidth sharing pattern that is different from a uniform one, as may be the case if bridges or other large users are present, and priorities can be easily superimpose
FQDB: a fair multisegment MAC protocol for dual bus networks
No full textThe fair queue dual bus (FQDB) medium-access control (MAC) protocol for dual bus networks, which is intrinsically fair in bandwidth sharing and retains all the positive features of distributed-queue dual-bus (DQDB) systems including simplicity, robustness, flexibility, 100% bandwidth utilization, and zero access delay at very low load, is presented. Features which make this protocol appealing with respect to others DQDB alternatives are represented by the fact that FQDB is compatible with the DQDB standard with respect to the physical arrangement and attachment to the bus, the XOR write tap, the access control field (ACF) length, and the three priority levels. Nevertheless, its properties are attractive also for protocols operating at 1 Gb/s and up. Fairness is formally proved, and it is shown that a bandwidth sharing pattern different from the uniform one can easily be enforced, as may be the case if bridges or other large users are presented. Queueing disciplines, priorities, and implementation issues are discussed, and comparisons obtained by simulation are give
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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