1,384 research outputs found
Unit commitment in oligopolistic markets by nonlinear mixed variable programming
No full textIn the paper we consider the unit commitment problem in oligopolistic markets. The formulation of the problem involves both integer and continuous variables and nonlinear functions as well, thus yielding a nonlinear mixed variable programming problem. Our formulation takes into account all technical constraints for the generating units, such as ramp rate and minimum up and down time constraints, considers the uncertainty related to the selling prices and allows modeling their dependence on the total output of a producer. The objective function is the expected value of the revenue over the different scenarios minus a term which takes into account the risk related to the decision. To solve the problem we adopt a recently proposed method for mixed integer nonlinear programming problems and use a derivative free algorithm to solve the continuous subproblems. We report results for two operators: one managing a single unit and the other managing three units. Numerical results give evidence to the features of the modeling and show viability of the adopted algorithm. © 2010 Springer Science+Business Media, LLC
Combined cycle unit commitment in a changing electricity market scenario
No full textFor Generation Companies (GENCOs) one of the most relevant issue is the commitment of the units, the scheduling of them over a daily (or longer) time frame, with the aim of obtaining the best profit. It strongly depends on the plant operational generation costs, which depend in turn on the choices taken at the design stage; it follows that design technical choices should also aim at determining the best generation cost structure of generating units with respect to the market opportunities. In the paper the unit commitment (UC) problem has been considered, with highlights on changes in the market scenario. The paper analyzes the relevance of some design choices (structure, size, regulation type) on the economics of the operation of gas-steam combined cycle generating units. To solve the UC problem, a recently proposed method for mixed integer nonlinear programming problems, with the use of a derivative free algorithm to solve the continuous subproblems, has been considered. The results for two GENCOs are reported: one managing a single unit and the other managing three units. Numerical examples show the sensitivity of the UC solutions to the market conditions and to the design choices on the regulation type in the evolving scenario of the Italian Electricity Market
Transformations, adaptations and resilience... behind the crisis of late antiquity. Some reflections from the Abruzzo region
No full textIl lavoro discute alcuni fenomeni di trasformazione e adattamento degli agglomerati secondari abruzzesi tra tardantichità e altomedioevo con un approccio analitic
Analysing the glaze of a medieval ceramic fragment from the Durres Amphitheater in Albania
No full textThe paper analyses the glaze of a ceramic sherd found in the southern sector of the Durres amphitheatre. Specifically, the sherd was found in a layer datable to the late 12th to early 13th century, which can be interpreted as a dismissal layer of a pottery kiln in use between the early and second half of the 12th century. The glaze was analysed using SEM-EDS and Total XRF techniques. The green-ocean glaze with a blue-sky decoration of the fragment has As-Co and Pb-Sn-Si compounds as pigments and phosphorous as a modifying agent and a flux. The glaze composition is SiO2 47.6 wt.%, TiO2 0.22 wt.%, Al2O3 4.08 wt.%, FeOtotal 0.22 wt.%, MnO 0.08 wt.%, MgO 0.23 wt.%, CaO 2.51 wt.%, Na2O 1.55 wt.%, K2O 5.16 wt.%, P2O5 3.01 wt.%, SnO2 4.13 wt.%, As2O5 4.13 wt.%, PbO 25.4 wt%. Fe is expressed as FeOtotal. The trace elements composition (ppm) is Co 3684, Ni 1023, Cu 819, Zn 3070, Bi 3172, and Sr 205. We introduced a robust glaze classification scheme based on chemistry. This scheme categories the glaze as alkaline-lead SnO2-opacified. We examined uncommon compounds formed in various textural contexts to establish the production origin and technique peculiarity. The glaze glasses form three different compositional domains: one represents the parental high-temperature initial glass composition, and two are related to immiscible segregations forming at lower temperatures. Five phases of the apatite supergroup were identified, along with other phases distributed throughout the glaze. The compounds present, such as Pb and Sn silicates, leucite, and k-feldspar and their balances, constrain the firing temperature to 720 celcius and 900 celcius, respectively
Accelerating strangelets via Penrose process in non-BPS fuzz-balls
No full textWe discuss how the Penrose process, taking place in singular rotating Kerr black holes as well as in their smooth, horizonless fuzz-ball counterparts in string theory, may provide an efficient mechanism for the acceleration of Ultra High Energy Cosmic Rays, including strangelets, a form of Strange Quark Matter that is under active experimental investigation with Mini-EUSO. We focus on non-BPS solutions of the JMaRT kind that present an ergo-region. We study geodetic motion and the (non-collisional) Penrose process in this context. In particular we compute its efficiency that turns out not to be bounded unlike for Kerr BH's and briefly comment on possible implications for near-future observations. (C) 2020 The Authors. Published by Elsevier B.V
Trasformazioni nell’anfiteatro di Durrës in età medievale: spazi abitativi e produttivi
No full textOrganizzazione e definizione di un quartiere urbano a Durrës: alcuni dati dalle indagini nel settore meridionale dell’anfiteatro
No full textThe paper aims to define the organisation and planimetric-spatial and ‘urbanistic’ characteristics of the post-medieval quarter built
in the southern sector of the Roman amphitheatre in Durres (Albania). In particular, the different renovations, parcelling out and
various uses of the rooms investigated during the recent excavation campaigns (2018-2021) is emphasized and put into perspective
with the results of the previous excavations (2004-2011). The subject of the reoccupation of amphitheatre buildings starting in Late
Antiquity is well known. The aim of this work is to show how, still in the post-medieval residential buildings were conditioned by
the partly preserved structures of the amphitheatre. The operations of rearrangement, clean up and removal of the collapses and
rubble after the 1270 earthquake, which were completed almost a century later (from the last quarter to the end of the 14th century),
conditioned the structuring of the post-medieval neighbourhoo
Economical considerations about combined cycle power plant control in deregulated markets
No full textElectrical energy markets around the world present various structures, which are evolving to pursue perfect competition. Then, it is essential to choose the best generating cost structure of power plants with respect to present and future market opportunities. In this view, the paper analyzes the economical impact of some technical choices for gas–steam combined cycle power plants. Attention is paid to the effects on the generating cost structure of the various types of combined cycle regulation and of the environmental parameters and constraints. The results for two different plants are reported as examples. Eventually, conclusions are drawn on how such technical features may influence the positioning in the market and the bidding opportunities of the power plant
- …
