Abstract
Long term electricity markets models tend to use simplified representations of both the demand and the generation units, to reduce the amount of input data and decision variables used, and also to decrease their execution times. On the one hand, hourly demand curves are usually simplified into a reduced set of non-chronological demand levels, each one representing hours with similar demand values. On the other hand, individual generation units are condensed into technologies grouping their costs curves by similarity in different appropriated technological cost mappings. This paper proposes several novel Mixed Integer Programming models to solve these two curve-fitting problems when the approximating function is a Piece-Wise Linear Function. By means of two real cases study it shows that the approximation approach has real applicability since it does not significantly compromise the traditional system representation. © 2011 IEEE.

Abstract
The increasing penetration of interruptible sources of energy is making security of supply a key aspect of present and future networks management, and reserves markets are gaining significant relevance. Demand representation used in traditional long term market models normally consists in a set of non chronological demand levels corresponding to hours with similar demand values. However, reserve issues are closely related with short term constraints (such as ramps), and this lack of chronological coupling does not allow for an appropriate representation of these technical constraints. This paper presents a joint energy and reserve conjectural equilibrium model that provides signal prices for both commodities and computes productions accordingly by satisfying system demand and reserve requirements. Generation is represented at a technological level, and water contributes to energy and reserve requirements with daily constraints. To reduce the feasible region, clustering is used to simplify hourly demand series into only a few daily patterns. In addition, keeping the link between hours and demand levels allows the model to combine short term technical constraints with traditional long term strategic planning constraints. © 2011 IEEE.

Abstract
Many studies addressing the effect of wind power integration strategies on the system adequacy assessment have been made, only concerning the generation point of view and usually disregarding the effect of the transmission network. On the other hand, studies considering the transmission network usually have ignored the effect of wind power integration strategies, focusing only on capturing the time dependent nature of this type of renewable energy source. Therefore, this work presents a chronological Monte Carlo simulation approach that assesses the system adequacy of composite systems (generation and transmission) considering non-dispatchable and dispatchable renewable energy production (wind and hydro, respectively). Case studies involving the IEEE-RTS 79 and modified versions of this system are presented and discussed as didactic examples.

Abstract
The paper describes some of the initial results of the CIGRE Working Group C4.605 "Modeling and aggregation of loads in flexible power networks". One of the tasks of the working group is to provide recommendations on developing equivalent static and dynamic models for clusters of diverse loads/generators, i.e., models of distribution network cells and microgrids and recommendations on procedures for data/response gathering and processing. This paper focuses on critical review of existing literature on aggregated models of wind-based generation, active distribution network cells and microgrids for power system studies. © 2011 IEEE.

Abstract
Despite the large number of studies on the phenomenon of imposex, the mechanism underlying the abnormal growth of male sexual characters onto females in numerous gastropod species is yet to be fully elucidated. Although several hypotheses have been raised over the years, a convincing body of evidence indicates that tributyltin-induced imposex involves the abnormal modulation of the retinoid X receptor (RXR). Here, we investigate the RXR gene transcription at different timings and tissues upon exposure to environmentally relevant concentrations of tributyltin (TOT) (100 ng Sn/L TBT) in both genders of the imposex susceptible gastropod Nucella lapillus. RXR gene transcription was determined at two time-points (i.e., before and after imposex initiation) by quantitative Real Time PCR in potential target tissues: the central nervous system (CNS), penis/penis forming area (PFA), gonads and digestive gland. TBT-exposure altered transcription of RXR gene in a tissue and sex specific manner. In the CNS, a significant down-regulation was observed in females both before and after imposex initiation (P <= 0.01 and P <= 0.05, respectively). A similar trend was observed in male CNS at the first time-point, although differences between control and the TBT-exposed group were just above significance (P=0.059). The penis/PFA showed no differences in transcription of RXR gene between control and TBT exposed female snails before imposex induction, or before and after imposex initiation for males. However, male penis showed higher transcription of RXR gene in comparison to the PFA of females. After imposex has been induced, a significant (P <= 0.001) increase in transcription of RXR gene was observed in penis of females with vas deference sequence index (VDS) levels of 3-4 in comparison with the PFA of both control and imposex females with VDS 1-2. At advanced stages of imposex, females displayed RXR transcription patterns in penis identical to those of males, which points to a functional role of RXR in the penis of both genders. In the other tissues, gonads and digestive gland. RXR gene transcription was not affected by TBT, at any of the analysed time-points. These patterns of RXR gene transcription upon TOT exposure highlight the pivotal involvement of the CNS in the mechanism of imposex induction. We integrate the results in a conceptual model, and discuss the central role of RXR and the retinoic acid signalling pathways in imposex and male genitalia formation in gastropods.

Abstract
In this paper, Emission Controlled Security Constrained Unit Commitment (ECSCUC) model is proposed in power system. This model consists of a closed-loop modified Unit Commitment (UC) and Security-constrained Optimal Power Flow (SCOPF). An emission controlled formulation is developed to improve the economic-environment conditions of operation of power system. The objective of this ECSCUC model is to obtain the maximum social welfarebased system operating cost while maintaining the system security also considering the environmental impacts. This paper proposed a multi-stage multi-objective mixed-integer nonlinear programming (MINLP) to minimize system operation cost. In this paper, multi-reservoir cascaded hydro plant with time delay and thermal plants are considered for maintaining the demand. The presented formulation treats emission controlled security constrained unit commitment of hydrothermal power system which attempts to optimize both cost and emission simultaneously. The numerical examples exhibit the effectiveness of the proposed model in recent competitive electricity markets.