41 research outputs found
Estimating heavy-tail exponents through max self-similarity
No full textIn this paper, a novel approach to the problem of estimating the heavy-tail exponent α >; 0 of a distribution is proposed. It is based on the fact that block-maxima of size m scale at a rate m 1/α for independent, as well as for a number of dependent data. This scaling rate can be captured well by the max-spectrum plot of the data that leads to regression based estimators for α. Consistency and asymptotic normality of these estimators is established for independent data under mild conditions on the behavior of the tail of the distribution. The proposed estimators have an important computational advantage over existing methods; namely, they can be calculated and updated sequentially in an on-line fashion without having to store the entire data set. Practical issues on the automatic selection of tuning parameters for the estimators and corresponding confidence intervals are also addressed. Extensive numerical simulations show that the proposed method is competitive for both small and large sample sizes, robust to contaminants and continues to work under the presence of substantial amount of dependence. The proposed estimators are used to illustrate the close connection between long-range dependence and heavy tails over an Internet traffic trace.Manuscript received June 11, 2007; revised September 24, 2010; accepted September 24, 2010. Date of current version February 18, 2011. The work of S. A. Stoev and G. Michailidis was supported in part by NSF Grant DMS-0806094. The work of M. S. Taqqu was supported in part by NSF Grant DMS-0706786. (DMS-0806094 - NSF; DMS-0706786 - NSF)First author draf
Conceptual design of a DOT farm generator station
No full textThe Delft Offshore Turbine (DOT) is a DUWIND research project that focuses on reducing the cost of offshore wind energy by bringing a radical change in offshore wind turbine technology. The main concept is to centralize electricity generation by having individual wind turbines create a flow of pressurized seawater to a hydropower station. The idea behind the DOT is that the high power to weight ratio from hydraulic drive systems gives the opportunity for a reduced nacelle mass and increased reliability of components by eliminating the use of individual gear trains, generators and power electronics. Therefore, the ultimate goal of this project is not only to suggest an efficient way of exploiting offshore wind but to present a cost efficient assembly. The development of the hydraulic drive train of the individual turbines has been studied over the last 3 years. This paper builds on these results and shows the working of these systems on a wind farm level. The model is built up for a North Sea site with 5MW DOT turbines with a total installed capacity of 1GW. By investigating hydro turbines, the central hydro power station is designed and detailed in this paper.Hydraulic EngineeringCivil Engineering and Geoscience
Recovery of sesamin, sesamolin, and minor lignans from sesame oil using solid support-free liquid-liquid extraction and chromatography techniques and evaluation of their enzymatic inhibition properties
No full textIn this study, an integrated process for the recovery of sesamin and sesamolin, two high added-value lignans of sesame oil (SO) was developed, using synchronous extraction and chromatography techniques. The extraction of SO phenolic content was studied using two different extraction techniques: Annular centrifugal extraction (ACE) and centrifugal partition extraction (CPE). The derived data of each experiment were compared in terms of revealing the yields, time, and solvents consumption showing that CPE is the most effective technique, concerning the solvent consumption. The isolation of lignans was achieved using centrifugal partition chromatography (CPC) both on semi-preparative and preparative scale. The biphasic system used for this purpose consisted of the following solvents: n-Hex/EtOAc/EtOH/H2O in proportion 2:3:3:2 (v/v/v/v) and direct recovery of the two major lignans sesamin and sesamolin was achieved. In parallel the CPC analysis resulted in the isolation of four minor lignans of sesame oil, i.e., samin, sesamol, sesaminol, and episesaminol. Structure elucidation of isolated lignans was based on HRMS/MS and NMR experiments. High-performance liquid chromatography (HPLC) was employed for quantitative analysis of the obtained extracts to determine the purity of the isolated compounds as well. The results of this study demonstrated that sesamin and sesamolin were recovered in purity higher than 95%, verifying the effectiveness of the purposed separation methodology. Finally, due to the general application of sesame oil in cosmetic industry, all the pure compounds were evaluated for their tyrosinase, elastase, collagenase, and hyaluronidase inhibition activity. Copyright © 2019 Michailidis, Angelis, Aligiannis, Mitakou and Skaltsounis. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms
Occupancy-based demand response and thermal comfort optimization in microgrids with renewable energy sources and energy storage
No full textIntegration of renewable energy sources in microgrids can be achieved via demand response programs, which change the electric usage in response to changes in the availability and price of electricity over time. This paper presents a novel control algorithm for joint demand response management and thermal comfort optimization in microgrids equipped with renewable energy sources and energy storage units. The proposed work aims at covering two main gaps in current state-of-the-art demand response programs. The first gap is integrating the objective of matching energy generation and consumption with the occupant behavior and with the objective of guaranteeing thermal comfort of the occupants. The second gap is developing a scalable and robust demand response program. Large-scale nature of the optimization problem and robustness are achieved via a two-level supervisory closed-loop feedback strategy: at the lower level, each building of the microgrid employs a local closed-loop feedback controller that processes only local measurements; at the upper level, a centralized unit supervises and updates the local controllers with the aim of minimizing the aggregate energy cost and thermal discomfort of the microgrid. The effectiveness of the proposed method is validated in a microgrid composed of three buildings, a photovoltaic array, a wind turbine, and an energy storage unit. Comparisons with alternative demand response strategies reveal that the proposed strategy efficiently integrates the renewable sources; energy costs are reduced and at the same time thermal comfort of the occupants is guaranteed. Furthermore, robustness is proved via consistent improvements achieved under heterogeneous conditions (different occupancy schedules and different weather conditions).Accepted Author ManuscriptTeam Bart De Schutte
Conceptual design of a DOT farm generator station
No full textApplied SciencesSustainable Energy Technolog
Memory and Reminiscence: Traces in Fener/ An Archive of Eviction
No full textThe project, Memory and Reminiscence: Traces in Fener / An Archive of Eviction, is situated in Istanbul and adresses the eviction of Greeks from Istanbul, taking four empy lots and a crossroad and forming a hub, an archive, a vessel of experiences that absorbs and collects the memories of the neighbourhood , towards the regeneration and rejuvenation of Fener. A proposed architectural device to deal with processes of memory accumulation & memory loss where the trace becomes an abstract machine for recording meaning. The understanding of memory as a device and how this can take the form of a ‘memory palace’ as a storage place, existing or imaginary is translated to an empty canvas where each visitor can ‘store’ his own memories, creating a personal mental map and linking the past with the present.Public Building_Border ConditionsArchitectureArchitecture and The Built Environmen
The naturalistic function of the descriptive pause in Nature morte by S. Plaskovitis : a fruitful dialogue with prose tradition
No full textThis article examines the mechanisms and semantic manifestations of how fictional characters and the social/natural space are depicted in the work of the post-war Greek author Spyros Plaskovitis, who exploits description as a way to organise his works conceptually and aesthetically. The paper focuses on a study of the descriptive pauses in Nature Morte, from the Naked Tree collection (1952), which is a short story not previously thoroughly studied by criticism wherein the author manages to structure the plot and the ideological core of his story with reference to naturalistic standards. An analysis of the narrative reveals the extent to which Plaskovitis converses with previous European and Greek prose tradition but at the same time achieves modernisation and adaptation to the aesthetic/cultural needs of his time.This article examines the mechanisms and semantic manifestations of how fictional characters and the social/natural space are depicted in the work of the post-war Greek author Spyros Plaskovitis, who exploits description as a way to organise his works conceptually and aesthetically. The paper focuses on a study of the descriptive pauses in Nature Morte, from the Naked Tree collection (1952), which is a short story not previously thoroughly studied by criticism wherein the author manages to structure the plot and the ideological core of his story with reference to naturalistic standards. An analysis of the narrative reveals the extent to which Plaskovitis converses with previous European and Greek prose tradition but at the same time achieves modernisation and adaptation to the aesthetic/cultural needs of his time
The naturalistic function of the descriptive pause in Nature morte by S. Plaskovitis : a fruitful dialogue with prose tradition
No full textThis article examines the mechanisms and semantic manifestations of how fictional characters and the social/natural space are depicted in the work of the post-war Greek author Spyros Plaskovitis, who exploits description as a way to organise his works conceptually and aesthetically. The paper focuses on a study of the descriptive pauses in Nature Morte, from the Naked Tree collection (1952), which is a short story not previously thoroughly studied by criticism wherein the author manages to structure the plot and the ideological core of his story with reference to naturalistic standards. An analysis of the narrative reveals the extent to which Plaskovitis converses with previous European and Greek prose tradition but at the same time achieves modernisation and adaptation to the aesthetic/cultural needs of his time
A Scientometric Study of the Stylometric Research Field
No full textStylometry has gained great popularity in digital humanities and social sciences. Many works on stylometry have recently been reported. However, there is a research gap regarding review studies in this field from a bibliometric and evolutionary perspective. Therefore, in this paper, a bibliometric analysis of publications from the Scopus database in the stylometric research field was proposed. Then, research articles published between 1968 and 2021 were collected and analyzed using the Bibliometrix R package for bibliometric analysis via the Biblioshiny web interface. Empirical results were also presented in terms of the performance analysis and the science mapping analysis. From these results, it is concluded that there has been a strong growth in stylometry research in recent years, while the USA, Poland, and the UK are the most productive countries, and this is due to many strong research partnerships. It was also concluded that the research topics of most articles, based on author keywords, focused on two broad thematic categories: (1) the main tasks in stylometry and (2) methodological approaches (statistics and machine learning methods)
Joint energy demand and thermal comfort optimization in photovoltaic-equipped interconnected microgrids
No full textElectrical smart microgrids equipped with small-scale renewable-energy generation systems are emerging progressively as an alternative or an enhancement to the central electrical grid: due to the intermittent nature of the renewable energy sources, appropriate algorithms are required to integrate these two typologies of grids and, in particular, to perform efficiently dynamic energy demand and distributed generation management, while guaranteeing satisfactory thermal comfort for the occupants. This paper presents a novel control algorithm for joint energy demand and thermal comfort optimization in photovoltaic-equipped interconnected microgrids. Energy demand shaping is achieved via an intelligent control mechanism for heating, ventilating, and air conditioning units. The intelligent control mechanism takes into account the available solar energy, the building dynamics and the thermal comfort of the buildings’ occupants. The control design is accomplished in a simulation-based fashion using an energy simulation model, developed in EnergyPlus, of an interconnected microgrid. Rather than focusing only on how each building behaves individually, the optimization algorithm employs a central controller that allows interaction among the buildings of the microgrid. The control objective is to optimize the aggregate microgrid performance. Simulation results demonstrate that the optimization algorithm efficiently integrates the microgrid with the photovoltaic system that provides free electric energy: in particular, for each building composing the microgrid, the energy absorbed from the main grid is minimized, the energy demand is balanced with the solar energy delivered to each building, while taking into account the thermal comfort of the occupants
