928 resultados para essence of operation


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Demand response programs and models have been developed and implemented for an improved performance of electricity markets, taking full advantage of smart grids. Studying and addressing the consumers’ flexibility and network operation scenarios makes possible to design improved demand response models and programs. The methodology proposed in the present paper aims to address the definition of demand response programs that consider the demand shifting between periods, regarding the occurrence of multi-period demand response events. The optimization model focuses on minimizing the network and resources operation costs for a Virtual Power Player. Quantum Particle Swarm Optimization has been used in order to obtain the solutions for the optimization model that is applied to a large set of operation scenarios. The implemented case study illustrates the use of the proposed methodology to support the decisions of the Virtual Power Player in what concerns the duration of each demand response event.

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Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

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The 15th International Conference on Runtime Verification (RV'15). 22-25 September. Vienna, Austria.

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The high penetration of distributed energy resources (DER) in distribution networks and the competitive environment of electricity markets impose the use of new approaches in several domains. The network cost allocation, traditionally used in transmission networks, should be adapted and used in the distribution networks considering the specifications of the connected resources. The main goal is to develop a fairer methodology trying to distribute the distribution network use costs to all players which are using the network in each period. In this paper, a model considering different type of costs (fixed, losses, and congestion costs) is proposed comprising the use of a large set of DER, namely distributed generation (DG), demand response (DR) of direct load control type, energy storage systems (ESS), and electric vehicles with capability of discharging energy to the network, which is known as vehicle-to-grid (V2G). The proposed model includes three distinct phases of operation. The first phase of the model consists in an economic dispatch based on an AC optimal power flow (AC-OPF); in the second phase Kirschen's and Bialek's tracing algorithms are used and compared to evaluate the impact of each resource in the network. Finally, the MW-mile method is used in the third phase of the proposed model. A distribution network of 33 buses with large penetration of DER is used to illustrate the application of the proposed model.

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Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

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Dissertation presented to Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa for obtaining the master degree in Membrane Engineering

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Dissertação para obtenção do Grau de Doutor em Engenharia Civil

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

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Epistemology in philosophy of mind is a difficult endeavor. Those who believe that our phenomenal life is different from other domains suggest that self-knowledge about phenomenal properties is certain and therefore privileged. Usually, this so called privileged access is explained by the idea that we have direct access to our phenomenal life. This means, in contrast to perceptual knowledge, self-knowledge is non-inferential. It is widely believed that, this kind of directness involves two different senses: an epistemic sense and a metaphysical sense. Proponents of this view often claim that this is due to the fact that we are acquainted with our current experiences. The acquaintance thesis, therefore, is the backbone in justifying privileged access. Unfortunately the whole approach has a profound flaw. For the thesis to work, acquaintance has to be a genuine explanation. Since it is usually assumed that any knowledge relation between judgments and the corresponding objects are merely causal and contingent (e.g. in perception), the proponent of the privileged access view needs to show that acquaintance can do the job. In this thesis, however, I claim that the latter cannot be done. Based on considerations introduced by Levine, I conclude that this approach involves either the introduction of ontologically independent properties or a rather obscure knowledge relation. A proper explanation, however, cannot employ either of the two options. The acquaintance thesis is, therefore, bound to fail. Since the privileged access intuition seems to be vital to epistemology within the philosophy of mind, I will explore alternative justifications. After discussing a number of options, I will focus on the so called revelation thesis. This approach states that by simply having an experience with phenomenal properties, one is in the position to know the essence of those phenomenal properties. I will argue that, after finding a solution for the controversial essence claim, this thesis is a successful replacement explanation which maintains all the virtues of the acquaintance account without necessarily introducing ontologically independent properties or an obscure knowledge relation. The overall solution consists in qualifying the essence claim in the relevant sense, leaving us with an appropriate ontology for phenomenal properties. On the one hand, this avoids employing mysterious independent properties, since this ontological view is physicalist in nature. On the other hand, this approach has the right kind of structure to explain privileged self-knowledge of our phenomenal life. My final conclusion consists in the claim that the privileged access intuition is in fact veridical. It cannot, however, be justified by the popular acquaintance approach, but rather, is explainable by the controversial revelation thesis.

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Splenectomy is the best available treatment for severe forms of hereditary spherocytosis, idiopathic thrombocytopenic purpura, and other hematologic conditions when these prove refractory to conservative management. It has been employed for many decades with low mortality and favorable remission rates. The use of laparoscopic splenectomy in recent years has been rapidly and even enthusiastically adopted in this field. However, the exact role of laparoscopic versus open surgery for hematologic diseases is still debated. In this study of 58 adult patients, laparoscopic procedures were compared with conventional splenectomies for similar indications. METHODS: All patients were operated on within an 8-year period. Subjects underwent similar procedures under the supervision of the same surgical school and were compared regarding age, gender, body mass index, and diagnosis. Laparoscopically managed cases (Group I, n = 30) were prospectively followed according to a written protocol, whereas the same investigation was retrospectively done with regard to traditional laparotomy (Group II, n = 28). Methods included general and demographic findings, duration and technical steps of operation, blood loss, weight of spleen, need for conversion (in minimally invasive subjects), intraoperative and postoperative complications, time until realimentation, postoperative hospitalization, mortality, and late follow-up including recurrence rate. RESULTS: Idiopathic thrombocytopenic purpura was the surgical indication in over 50% of the patients in both groups, but familial spherocytosis, thalassemia, myelodysplasia, and lymphomas were also represented in this series. Laparoscopic procedures took more time to perform (P = 0.004), and postoperative hospitalization was 2 days shorter, but this difference was not statistically significant. Postoperative hematocrit and volume of blood transfusions was equivalent, although the laparoscopic cases had a somewhat lower preoperative hematocrit (NS) and displayed better recovery for this measurement (P = 0.03). More patients in Group I were able to accept oral food on the first day than subjects undergoing conventional operations (P < 0.05). Relatively few conversions were necessary during the minimally invasive surgeries (13.3%), and postoperative early and late complications as well as recurrences occurred in similar proportions. Also, the mean weight of the spleen was not statistically different between the groups, although there was a marked numerical tendency toward larger masses in conventional procedures. No spleen in Group I exceeded 2.0 kg, whereas in Group II values up to 4.0 kg occurred, and the mean weight was 50% higher in the latter group. CONCLUSIONS: 1) Minimally invasive splenectomy was essentially comparable to open surgery with regard to safety, efficacy, and late results; 2) Advantages concerning shorter postoperative hospitalization could not be shown, despite earlier food intake and a non-significant tendency toward earlier discharge; 3) This new modality should be considered an option in cases of hematologic conditions whenever the spleen is not hugely enlarged.

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The purpose of this project is to analyse and evaluate if the rural tourism cottage Quinta dos I’s will be profitable within the first five years of operation. It starts with a brief description of the business, followed by an industry analysis of the rural tourism market in Portugal and an intensive competitor analysis to evaluate Quinta dos I’s’ competitive advantages. The project then defines a marketing plan to generate awareness and establish the cottage in the market. Finally, a financial analysis is performed to examine the outcome of Quinta dos I’s’ recommended strategic activities. The results of this project show that the cottage is profitable after the first year of operation and expects to grow annually.

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This paper presents a new approach of pre-defined profiles, based in different voltage and current values, to control the charging and discharging processes of batteries in order to assess their performance. This new approach was implemented in a prototype that was specially developed for such purpose. This prototype is a smart power electronics platform that allows to perform batteries analysis and to control the charging and discharging processes through a web application using pre-defined profiles. This platform was developed aiming to test different batteries technologies. Considering the relevance of the energy storage area based in batteries, especially for the batteries applied to electric mobility systems, this platform allows to perform controlled tests to the batteries, in order to analyze the batteries performance under different scenarios of operation. Besides the results obtained with the batteries, this work also intends to produce results that can contribute to an involvement in the strengthening of the Internet-of-Things.

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This paper presents a comprehensive comparison of a current-source converter and a voltage-source converter for three-phase electric vehicle (EV) fast battery chargers. Taking into account that the current-source converter (CSC) is a natural buck-type converter, the output voltage can assume a wide range of values, which varies between zero and the maximum instantaneous value of the power grid phase-to-phase voltage. On the other hand, taking into account that the voltage-source converter (VSC) is a natural boost-type converter, the output voltage is always greater than the maximum instantaneous value of the power grid phase-to-phase voltage, and consequently, it is necessary to use a dc-dc buck-type converter for applications as EV fast battery chargers. Along the paper is described in detail the principle of operation of both the CSC and the VSC for EV fast chargers, as well as the main equations of the power theory and current control strategies. The comparison between both converters is mainly established in terms of the total harmonic distortion of the grid current and the estimated efficiency for a range of operation between 10 kW and 50 kW.

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This paper presents a novel architecture of a bidirectional bridgeless interleaved converter for battery chargers of electric vehicles (EVs). The proposed converter is composed by two power stages: an ac-dc converter that is used to interface the power grid and the dc-link, and a dc-dc converter that is used to interface the dc-link and the batteries. The ac-dc converter is an interleaved bridgeless bidirectional boost-type converter and the dc-dc converter is a bidirectional buck-boost-type converter. The proposed converter works with sinusoidal grid current and with high power factor for all operating power levels, and in both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operation modes. In the paper is described in detail the proposed converter for EV battery chargers: the circuit topology, the principle of operation, the power control theory, and the current control strategy. Several simulation results for both G2V and V2G operation modes are presented.

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This paper presents a novel concept of unidirectional bridgeless combined boost-buck converter for electric vehicles (EVs) battery chargers. The proposed converter is composed by two power stages: an ac-dc front-end converter used to interface the power grid and the dc-link, and a dc-dc back-end converter used to interface the dc-link and the batteries. The ac-dc converter is a bridgeless boost-type converter and the dc-dc converter is an interleaved buck-type converter. The proposed converter operates with sinusoidal grid current and unitary power factor for all operating power levels. Along the paper is described in detail the proposed converter for EV battery chargers: the circuit topology, the different stages describing the principle of operation, the power control theory, and the current control strategy, for both converters. Along the paper are presented several simulation results for a maximum power of 3.5 kW.