A generic learning multi-agent-system approach for spatio-temporal-, thermal- and energy-aware scheduling

This paper proposes an agent based approach to the scheduling of jobs in data centers under thermal constraints. The model encompasses both temporal and spatial aspects of the temperature evolution using a unified model, taking into account the dynamics of heat production and dissipation. Agents coordinate to eventually move jobs to the best suitable place and to adapt dynamically the frequency settings of the nodes to the best combination. Several objectives of the agents are compared under different circumstances by an extensive set of experiments

Examining the impact of Turkey’s emerging Muslim Democrats on processes of party system institutionalization.

This doctoral thesis examines the impact of moderate Islamist parties on party system institutionalization in Turkey. Its focus is on the political emergence of ‘Muslim-Democrat’ parties. This term was coined by the scholar Vali Nasr and refers to a new sub-type of party actor in the spectrum of political Islam that employs Islamic religiousity in its electoral appeal but operates within the normative framework of liberal democracy. The central question driving this thesis is to uncover how Turkey’s Muslim-Democrat parties have had a positive effect in advancing the institutionalization of Turkey’s party system. This thesis attempts to contribute to the broader debate regarding the compatibility of Islamist parties and democratic politics in demonstrating that the former, when adopting a moderate format akin to the ‘Muslim-Democrat’ ideal type, can have a positive effect in advancing processes of party system institutionalization. This effect would then be critically discussed within the context of its impact on broader democratic consolidation. The AKP, Turkey’s incumbent party, is chosen as the case study of a Muslim Democrat party. The theoretical basis for the empirical element of this thesis is informed by the research framework for party system institutionalization that was formulated by Mainwaring and Scully in the context of Latin American ‘third-wave’ democracies. They posit four specific factors to examine the institutional strengths of democratic party systems. This framework is used to examine the development of the Turkish party system and the impact of the Islamist parties, especially Muslim-Democrat parties, on these processes. The bulk of this thesis uses statistical analyses of aggregate electoral as well as attitudinal survey data as well as examining the political discourse of the election manifestoes of Turkey’s Islamist and Muslim-Democrat parties using content analysis as well as discourse analysis. The findings of this analysis conclude that Muslim-Democrat parties like the AKP have indeed contributed towards party system institutionalization in Turkey both in terms of stabilizing inter-party competition and social rootedness as well as increasing the legitimacy of democratic civilian politics. In that sense, their effect on party system institutionalization has had a beneficial effect on Turkey’s democratic consolidation

Inhibition of the photoinduced structural phase transition in the excitonic insulator Ta2_2NiSe5_5

Femtosecond time-resolved mid-infrared reflectivity is used to investigate the electron and phonon dynamics occurring at the direct band gap of the excitonic insulator Ta$_2$NiSe$_5$ below the critical temperature of its structural phase transition. We find that the phonon dynamics show a strong coupling to the excitation of free carriers at the \Gamma\ point of the Brillouin zone. The optical response saturates at a critical excitation fluence $F_C = 0.30~\pm~0.08$~mJ/cm$^2$ due to optical absorption saturation. This limits the optical excitation density in Ta$_2$NiSe$_5$ so that the system cannot be pumped sufficiently strongly to undergo the structural change to the high-temperature phase. We thereby demonstrate that Ta$_2$NiSe$_5$ exhibits a blocking mechanism when pumped in the near-infrared regime, preventing a nonthermal structural phase transition

Ultrafast Electronic Band Gap Control in an Excitonic Insulator

We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta$_2$NiSe$_5$ investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of $F_{C} = 0.2$ mJ cm$^{-2}$, the band gap $narrows$ transiently, while it is $enhanced$ above $F_{C}$. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta$_2$NiSe$_5$, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta$_2$NiSe$_5$ with light on the femtosecond time scale

Spatio-temporal coherent control of thermal excitations in solids

X-ray reflectivity (XRR) measurements of femtosecond laser-induced transient gratings are applied to demonstrate the spatio-temporal coherent control of thermally induced surface deformations on ultrafast timescales. Using gracing incidence X-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-\AA{} resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in X-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period $\Lambda$ can be canceled by a second, time-delayed TG excitation shifted by $\Lambda/2$. The ultimate speed limits of such an ultrafast X-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments

Instantaneous band gap collapse in photoexcited monoclinic VO2_2 due to photocarrier doping

Using femtosecond time-resolved photoelectron spectroscopy we demonstrate that photoexcitation transforms monoclinic VO$_2$ quasi-instantaneously into a metal. Thereby, we exclude an 80 femtosecond structural bottleneck for the photoinduced electronic phase transition of VO$_2$. First-principles many-body perturbation theory calculations reveal a high sensitivity of the VO$_2$ bandgap to variations of the dynamically screened Coulomb interaction, supporting a fully electronically driven isostructral insulator-to-metal transition. We thus conclude that the ultrafast band structure renormalization is caused by photoexcitation of carriers from localized V 3d valence states, strongly changing the screening \emph{before} significant hot-carrier relaxation or ionic motion has occurred