Nonthermal steady states after an interaction quench in the Falicov-Kimball model

We present the exact solution of the Falicov-Kimball model after a sudden change of its interaction parameter using non-equilibrium dynamical mean-field theory. For different interaction quenches between the homogeneous metallic and insulating phases the system relaxes to a non-thermal steady state on time scales on the order of hbar/bandwidth, showing collapse and revival with an approximate period of h/interaction if the interaction is large. We discuss the reasons for this behavior and provide a statistical description of the final steady state by means of generalized Gibbs ensembles.Comment: 4 pages, 2 figures; published versio

Nonlinear response of quantum cascade structures

The gain spectrum of a terahertz quantum cascade laser is analysed by a non equilibrium Green's functions approach. Higher harmonics of the response function were retrievable, providing a way to approach nonlinear phenomena in quantum cascade lasers theoretically. Gain is simulated under operation conditions and results are presented both for linear response and strong laser fields. An iterative way of reconstructing the field strength inside the laser cavity at lasing conditions is described using a measured value of the level of the losses of the studied system. Comparison with recent experimental data from time-domain-spectroscopy indicates that the experimental situation is beyond linear response.Comment: 4 pages, 3 figures included in text, to appear in Applied Physics Letter

A 150-million-year-old crab larva and its implications for the early rise of brachyuran crabs

True crabs (Brachyura) are the most successful group of decapod crustaceans. This success is most likely coupled to their life history, including two specialised larval forms, zoea and megalopa. The group is comparably young, starting to diversify only about 100 million years ago (mya),with a dramatic increase in species richness beginning approximately 50 mya. Early evolution of crabs is still very incompletely known. Here, we report a fossil crab larva, 150 mya, documented with up-to-date imaging techniques. It is only the second find of any fossil crab larva, but the first complete one, the first megalopa, and the oldest one (other fossil ca. 110 mya). Despite its age, the new fossil possesses a very modern morphology, being indistinguishable from many extant crab larvae. Hence, modern morphologies must have been present significantly earlier than formerly anticipated. We briefly discuss the impact of this find on our understanding of early crab evolution

A wave function based ab initio non-equilibrium Green's function approach to charge transport

We present a novel ab initio non-equilibrium approach to calculate the current across a molecular junction. The method rests on a wave function based description of the central region of the junction combined with a tight binding approximation for the electrodes in the frame of the Keldysh Green's function formalism. In addition we present an extension so as to include effects of the two-particle propagator. Our procedure is demonstrated for a dithiolbenzene molecule between silver electrodes. The full current-voltage characteristic is calculated. Specific conclusions for the contribution of correlation and two-particle effects are derived. The latter are found to contribute about 5% to the current. The order of magnitude of the current coincides with experiments.Comment: 21 pages, 3 figure

Underground vehicle wagon project for mining enterprise

Rakenduskõrgharidusõppe lõputöö Tehnotroonika õppekavalTöö hõlmab nelja transportfurgooni projekteerimist ning ehitamist Volkswageni baasmudelile Crafter. Projekteerimisel lähtuti hankedokumentatsioonis esitatud nõuetest ning saadi lisainformatsiooni erinevatest kirjandusallikatest. Töö eesmärgiks on projekteerida ja ehitada maa-aluseid keskkonnatingimusi rahuldav transportfurgoon inimeste veoks allmaa kaeveõõntes. Antud töös on välja toodud põhjendused materjalide valikul, lähtumine Eesti Vabariigi seadustest ja normidest, soojustehnilised arvutused, joonised töö korratavuseks, juhised enamuse elementide ja sõlmede valmistamiseks. Antud töö väljundiks on korrosioonikindel furgoon, mis on pestav, hanketingimustele vastav, vastupidav raskele töökeskkonnale ega ületaks koos reisijate massiga sõiduvahendi lubatud kandevõimet. Olulised punktid käesoleva töö puhul on furgooni soojustus, vastavus kehtestatud nõuetele, furgooni kasutamise ohutus, tugevuslikud aspektid ja kogukaal. Lõputöö sisaldab montaažijooniseid, instruktaaži sõlmede valmistamiseks kui ka tehnilisi jooniseid, kus on välja toodud detailide mõõdud ning sõlmed, et väljund oleks korratav.The paper includes a project for four underground vehicle wagons which are built on Volkswagen’s model Crafter. Designing was based on the tender documents and additional information was found from literature. The purpose of the work is to design a vehicle wagon which would be suitable for underground mining networks and which shall be able to accommodate 24 people. The project points out arguments on selecting different coatings for metal surfaces, law appliances on building a vehicle wagon, thermal analysis, strength analysis and instructions on how to design and install different components of the wagon. The outcome of this project is a corrosion resistant wagon which is washable, meets the requirements of tender documents, is capable to accommodate 24 people and does not exceed 5 ton weight limit. The work contains exploded views and instructions on how to assembly different parts of the wagon

Der demographische Wandel und kommunale Investitionen

Die Investitionstätigkeit der Kommunen in Deutschland hängt im Wesentlichen von der örtlichen Finanzkraft ab und weist daher eine erhebliche räumliche Streuung auf. Doch gewisse regionale Unterschiede bei den Investitionen sind durchaus angemessen, wenn man die zukünftigen Nutzungs-intensitäten der überwiegend langfristig angelegten Infrastrukturausstattung berücksichtigt. Da vor allem dort mehr investiert wird, wo die Nutzungsintensität in den kommenden Jahren wächst, fallen die regionalen Unterschiede bei den kommunalen Investitionsausgaben nicht so stark ins Gewicht. Die Gefahr, dass Kommunen mit geringer Ertragskraft in einen Teufelskreis geraten, in dem ausbleibende Investitionen primär einen Verlust an Standortattraktivität verursachen, scheint - wenn überhaupt - nur in Einzelfällen gegeben. Hingegen ist vielerorts eine Trägheit bei der Anpassung der Investitionen an eine neue demographische Situation zu beobachten. So investieren einige finanzstarke, schrumpfende Kommunen im Hinblick auf die abnehmenden Nutzungsintensitäten relativ viel in ihre Infrastruktur, währenddessen zahlreiche wachsende Orte ihre Kapazitäten unzureichend erweitern. Investitionszuschüsse sollten weniger an die gegenwärtige Bevölkerung, sondern vielmehr an die erwartete zukünftige Bevölkerungsentwicklung gekoppelt werden. Damit könnte die Effizienz der kommunalen Investitionen deutlich erhöht werden

Zur Zukunft der kommunalen Wohnungspolitik in Deutschland und Europa. Tagungsband: Referate und Diskussionen im Rahmen des 3. Halleschen Kolloquiums zur Kommunalen Wirtschaft am 5. und 6. November 2009

Am 5. und 6. November 2009 veranstaltete das IWH ein Kolloquium zu einem Themenschwerpunkt aus dem Bereich der Kommunalwirtschaft. Das zentrale Anliegen der Konferenz bestand darin, die künftige Rolle der kommunalen Wohnungswirtschaft zu diskutieren und im Vergleich zu alternativen wohnungspolitischen Instrumenten zu bewerten. Das Kolloquium befasste sich mit den Aufgaben und Aktivitäten, die den Kommunen auf dem Wohnungsmarkt zukommen bzw. unter modernen wirtschaftlichen und gesellschaftlichen Bedingungen zukommen sollten. Die Tagungsbeiträge sind in diesem Band veröffentlicht

Leveraging Model Inherent Variable Importance for Stable Online Feature Selection

Feature selection can be a crucial factor in obtaining robust and accurate predictions. Online feature selection models, however, operate under considerable restrictions; they need to efficiently extract salient input features based on a bounded set of observations, while enabling robust and accurate predictions. In this work, we introduce FIRES, a novel framework for online feature selection. The proposed feature weighting mechanism leverages the importance information inherent in the parameters of a predictive model. By treating model parameters as random variables, we can penalize features with high uncertainty and thus generate more stable feature sets. Our framework is generic in that it leaves the choice of the underlying model to the user. Strikingly, experiments suggest that the model complexity has only a minor effect on the discriminative power and stability of the selected feature sets. In fact, using a simple linear model, FIRES obtains feature sets that compete with state-of-the-art methods, while dramatically reducing computation time. In addition, experiments show that the proposed framework is clearly superior in terms of feature selection stability.Comment: To be published in the Proceedings of the 26th ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD 2020