University of Stuttgart

About: University of Stuttgart is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Laser & Finite element method. The organization has 27715 authors who have published 56370 publications receiving 1363382 citations. The organization is also known as: Universität Stuttgart.

Initial corrosion observed on the atomic scale

Abstract: Corrosion destroys more than three per cent of the world's GDP. Recently, the electrochemical decomposition of metal alloys has been more productively harnessed to produce porous materials with diverse technological potential. High-resolution insight into structure formation during electrocorrosion is a prerequisite for an atomistic understanding and control of such electrochemical surface processes. Here we report atomic-scale observations of the initial stages of corrosion of a Cu3Au111 single crystal alloy within a sulphuric acid solution. We monitor, by in situ X-ray diffraction with picometre-scale resolution, the structure and chemical composition of the electrolyte/alloy interface as the material decomposes. We reveal the microscopic structural changes associated with a general passivation phenomenon of which the origin has been hitherto unclear. We observe the formation of a gold-enriched single-crystal layer that is two to three monolayers thick, and has an unexpected inverted (CBA-) stacking sequence. At higher potentials, we find that this protective passivation layer dewets and pure gold islands are formed; such structures form the templates for the growth of nanoporous metals. Our experiments are carried out on a model single-crystal system. However, the insights should equally apply within a crystalline grain of an associated polycrystalline electrode fabricated from many other alloys exhibiting a large difference in the standard potential of their constituents, such as stainless steel (see ref. 5 for example) or alloys used for marine applications, such as CuZn or CuAl.

The feature and service interaction problem in telecommunications systems: a survey

Abstract: Today's telecommunication systems are enhanced by a large and steadily growing number of supplementary services, each of which consists of a set of service features. A situation where a combination of these services behaves differently than expected from the single services' behaviors, is called service interaction. This interaction problem is considered as a major obstacle to the introduction of new services into telecommunications networks. We present a survey of the work carried out in this field during the last decade (1988-98). After a brief review of classification criteria that exist for feature interactions so far, we use a perspective called the emergence level view. This perspective pays respect to the fact that the sources for interactions can be of many different kinds, e.g., requirement conflicts or resource contentions. It is used to rationalize the impossibility of coping with the problem with one single approach. We also present a framework of four different criteria in order to classify the approaches dealing with the problem. The general kind of approach taken, a refinement of the well known detection, resolution, and prevention categories, serves as the main classification criterion. It is complemented by the method used, the stage during the feature lifecycle where an approach applies, and the system (network) context. The major results of the different approaches are then presented briefly using this classification framework. We finally draw some conclusions on the applicability of this framework and on possible directions of further research in this field.

Automated program repair

Abstract: Automated program repair can relieve programmers from the burden of manually fixing the ever-increasing number of programming mistakes.

Cold hybrid ion-atom systems

Abstract: Hybrid systems of laser-cooled trapped ions and ultracold atoms combined in a single experimental setup have recently emerged as a new platform for fundamental research in quantum physics. This paper reviews the theoretical and experimental progress in research on cold hybrid ion-atom systems which aim to combine the best features of the two well-established fields. A broad overview is provided of the theoretical description of ion-atom mixtures and their applications, and a report is given on advances in experiments with ions trapped in Paul or dipole traps overlapped with a cloud of cold atoms, and with ions directly produced in a Bose-Einstein condensate. This review begins with microscopic models describing the electronic structure, interactions, and collisional physics of ion-atom systems at low and ultralow temperatures, including radiative and nonradiative charge-transfer processes and their control with magnetically tunable Feshbach resonances. Then the relevant experimental techniques and the intrinsic properties of hybrid systems are described. In particular, the impact is discussed of the micromotion of ions in Paul traps on ion-atom hybrid systems. Next, a review of recent proposals is given for using ions immersed in ultracold gases for studying cold collisions, chemistry, many-body physics, quantum simulation, and quantum computation and their experimental realizations. The last part focuses on the formation of molecular ions via spontaneous radiative association, photoassociation, magnetoassociation, and sympathetic cooling. Applications and prospects are discussed of cold molecular ions for cold controlled chemistry and precision spectroscopy.