Mathematical modelling and methodology for cost optimization of variable renewable electricity integration

The global production of electricity contributes significantly to the release of carbon dioxide emissions. Therefore, a transformation of the electricity system is of vital importance in order to restrict global warming. This thesis concerns modelling and methodology of an electricity system which contains a large share of variable renewable electricity generation, such as wind and solar power.The models developed in this thesis concern optimization of long-term investments in the electricity system. They aim at minimizing investment and production costs under electricity production constraints, using different spatial resolutions and technical detail, while meeting the electricity demand. Furthermore, they are able to capture some of the variation management strategies necessary for electricity systems that include a large share of variable renewable electricity. These models are very large in nature due to the high temporal resolution needed to capture the wind variations, and thus different decomposition methods are applied to reduce solution times. We develop two different decomposition methods: 1) Lagrangian relaxation combined with variable splitting solved using a subgradient algorithm, and 2) a heuristic decomposition approach using a consensus algorithm. In both cases, the decomposition is done with respect to the temporal resolution by dividing the year into 2-week periods. The decomposition methods are tested and evaluated for cases involving regions with different energy mixes and conditions for wind power. Numerical results show faster computation times compared to the non-decomposed models and capacity investment options similar to the optimal solutions given by the latter models

Optimization of low-cost integration of wind and solar power in multi-node electricity systems: Mathematical modelling and dual solution approaches

The global production of electricity contributes significantly to the release of CO2 emissions. Therefore, a transformation of the electricity system is of vital importance in order to restrict global warming. This thesis concerns modelling and methodology of electricity systems which contain a large share of variable renewable electricity generation (i.e. wind and solar power).The two models developed in this thesis concern optimization of long-term investments in the electricity system. They aim at minimizing investment and production costs under electricity production constraints, using different spatial resolutions and technical detail, while meeting the electricity demand. These models are very large in nature due to the 1) high temporal resolution needed to capture the wind and solar variations while maintaining chronology in time, and 2) need to cover a large geographical scope in order to represent strategies to manage these variations (e.g.\ electricity trade). Thus, different decomposition methods are applied to reduce computation times. We develop three different decomposition methods: Lagrangian relaxation combined with variable splitting solved using either i) a subgradient algorithm or ii) an ADMM algorithm, and iii) a heuristic decomposition using a consensus algorithm. In all three cases, the decomposition is done with respect to the temporal resolution by dividing the year into 2-week periods. The decomposition methods are tested and evaluated for cases involving regions with different energy mixes and conditions for wind and solar power. Numerical results show faster computation times compared to the non-decomposed models and capacity investment options similar to the optimal solutions given by the latter models. However, the reduction in computation time may not be sufficient to motivate the increase in complexity and uncertainty of the decomposed models

Dynaflow ™ 48, a microfluidic chip solution for increasing throughput and data quality in patch-clamp-based drug screening

Ion channels are transm embrane proteins, found in virtually all cell types throughout the human body. Ion channels underlie neural communication, memory, behavior, every movement and heartbeat, and are as such prone to cause disease if malfunctioning. Therefore ion channels are very important targets in drug discovery. The gold standard technique for obtaining information on ion channel function with high information content and temporal resolution is patch-clamp. The technique measures the minute currents originating from the movement of ions across the cellular membrane, and enables determination of the potency and efficacy of a drug. However, patch-clamp suffers from serious throughput restrictions due to its laborious nature. To address the throughput problems we have developed a microfluidic chip containing 48 microchannels for an extremely rapid, sequential delivery of a large number of completely controlled solution environments to a lifted, patch-clamped cell. In this way, throughput is increased drastically compared to classical patch-clamp perfusion set-ups, with uncompromised data quality. The 48-microchannel chip has been used for the characterization of drugs affecting ligand-gated ion channels including agonists, antagonists and positive modulators with positive effects on both throughput and data quality.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 dofinansowane zostało ze środków MNiSW w ramach działalności upowszechniającej naukę

Evaluating stages of development in second language French: A machine-learning approach

This paper describes a system to define and evaluate development stages in second language French. The identification of such stages can be formulated as determining the frequency of some lexical and grammatical features in the learners’ production and how they vary over time. The problems in this procedure are threefold: identify the relevant features, decide on cutoff points for the stages, and evaluate the degree of success of the model. The system addresses these three problems. It consists of a morphosyntactic analyzer called Direkt Profil and a machine-learning module connected to it. We first describe the usefulness and rationale behind its development. We then present the corpus we used to develop the analyzer. Finally, we present new and substantially improved results on training machine-learning classifiers compared to previous experiments (Granfeldt et al., 2006). We also introduce a method to select attributes in order to identify the most relevant grammatical features

Cliticisation in the acquisition of French as L1 and L2

The intense debate on continuity in child grammars has largely focused on the existence of Functional Categories (FCs) in early grammars despite differences in language use with adults (e.g., omissions, word order errors, lack of case marking). Simplified, the major theoretical explanations for these properties range from Maturational accounts (Radford 1990 and later) claiming an initial absence of FCs, to Weak Continuity views (Clahsen, Eisenbeiss and Penke 1996) claiming one (or more) initially underspecified FCs that are subsequently specified by exposure to input, and further to Strong Continuity views (Poeppel and Wexler 1993) where an adult set of FCs is initially assumed and child language is claimed to be subject solely to performance constraints. A similar debate has raged in SLA (see Herschensohn this volume, for discussion) where an initial absence of FCs has been advocated by many scholars (Vainikka and Young-Scholten 1996, among others). The opposite view, i.e. initial presence of FCs, has been defended by scholars such as Schwartz and Sprouse (1996), who claim that, initially, structural representations of the L2 are based solely on the L1, and by scholars claiming direct UG-access to the FCs (White 1996, Prevost and White 2000b). Most of these studies concern adult SLA. One way to investigate FCs is to study the acquisition of clitics. There is a strong connection between FCs and clitics; clitic pronouns in French have an especially tight relation to the finite verb, which they precede in most cases. Since French is a verb raising language, it follows that the clitic must also move to an FC at spell-out. A common argument, based on this logic, is that a structure of the type je l'entends (I it hear - ‘I hear it’) is diagnostic of the existence of (some) FC in the grammar of a particular learner. These facts have lead researchers investigating FCs in L1 and L2 to analyse the development of clitic pronouns (Hamann et al. 1996 on L1 monolingual French, White 1996 on child L2 French, Herschensohn, this volume, on adult L2 French), and Meisel (1994 on bilingual L1 French) who uses the emergence of subject clitics and finite verbs for determining when AGR is acquired. If scholars agree on the relation “if clitics then FCs“, the inverse relation is much more problematic. Certain data (see below) suggest that, in adult L2 acquisition of French, there may be object pronouns but not clitics. But a lack of clitics does not necessarily imply a lack of FCs. The question mirrors in a certain way the issue of Missing Inflection: if systematic and functional inflection is present, then we can conclude that FCs are accessible, but the lack of inflection does not necessarily imply the absence of FCs (Lardière 1998, Prevost and White 2000b). Now, the syntax of clitics, and more generally cliticisation (pronouns and articles), is in itself a long-standing issue in theoretical linguistics and especially in Romance linguistics. A recently developed theory of pronouns provides new perspectives from which to approach acquisition data. In their detailed analysis, Cardinaletti and Starke (1999) reveal a typology that seems to have been rapidly accepted (see peer comments in van Riemsdijk 1999), where pronouns are classified as either strong, weak or clitics. The distributional and interpretative properties of clitics, weak pronouns and strong pronouns depend on the amount of (functional) internal structure they project. Cliticisation in this view can be seen as a change in structural representation during the derivation, from more to less (i.e., from XP to X0). Since both UG-access and FCs are prerequisites for cliticisation, the study of cliticisation can contribute to a better general understanding of L1 and L2 acquisition. Indeed, the strong consensus on direct access to UG and to early instantiations of FCs in L1 acquisition is not as clear in adult L2 acquisition (see White 2000 for an overview). Furthermore, previous work on clitics in L1 and adult L2 acquisition suggests that there may be differences in the way these are acquired. There is, therefore, a need for further L1 and adult L2 comparative research addressing cliticisation and controlling for general access to FCs. In this paper, we will address the issue of differences between L1 and adult L2 acquisition with respect to cliticisation. Adopting the framework of Cardinaletti and Starke (1999), we will investigate how and to what extent subject and object pronouns and articles become clitics in developing grammars. The data come from bilingual first language acquisition (2L1) and adult second language acquisition (L2). The children are Swedish-French bilinguals and the adults native speakers of Swedish. The fact that Swedish, the “other” language here, is present in both cases allows us to separate transfer from age effects

Evaluating Stages of Development in Second Language French: A Machine-Learning Approach

Proceedings of the 16th Nordic Conference of Computational Linguistics NODALIDA-2007. Editors: Joakim Nivre, Heiki-Jaan Kaalep, Kadri Muischnek and Mare Koit. University of Tartu, Tartu, 2007. ISBN 978-9985-4-0513-0 (online) ISBN 978-9985-4-0514-7 (CD-ROM) pp. 73-80

Direkt profil: A system for evaluating texts of second language learners of French based on developmental sequences

Direkt Profil is an automatic analyzer oftexts written in French as a second lan-guage. Its objective is to produce an eval-uation of the developmental stage of stu-dents under the form of a grammaticallearner profile. Direkt Profil carries outa sentence analysis based on developmen-tal sequences, i.e. local morphosyntacticphenomena linked to a development in theacquisition of French.The paper presents the corpus that we useto develop the system and briefly, the de-velopmental sequences. Then, it describesthe annotation that we have defined, theparser, and the user interface. We con-clude by the results obtained so far: on thetest corpus the systems obtains a recall of83% and a precision of 83%