Contrary to common belief, market correlations between assets are constant

Models routinely used in practice are probably misleading, creating artificial results, write Zeno Adams, Thorsten Glück and Roland Füs

Phases of QCD, Thermal Quasiparticles and Dilepton Radiation from a Fireball

We calculate dilepton production rates from a fireball adapted to the kinematical conditions realized in ultrarelativistic heavy ion collisions over a broad range of beam energies. The freeze-out state of the fireball is fixed by hadronic observables. We use this information combined with the initial geometry of the collision region to follow the space-time evolution of the fireball. Assuming entropy conservation, its bulk thermodynamic properties can then be uniquely obtained once the equation of state (EoS) is specified. The high-temperature (QGP) phase is modelled by a non-perturbative quasiparticle model that incorporates a phenomenological confinement description, adapted to lattice QCD results. For the hadronic phase, we interpolate the EoS into the region where a resonance gas approach seems applicable, keeping track of a possible overpopulation of the pion phase space. In this way, the fireball evolution is specified without reference to dilepton data, thus eliminating it as an adjustable parameter in the rate calculations. Dilepton emission in the QGP phase is then calculated within the quasiparticle model. In the hadronic phase, both temperature and finite baryon density effects on the photon spectral function are incorporated. Existing dilepton data from CERES at 158 and 40 AGeV Pb-Au collisions are well described, and a prediction for the PHENIX setup at RHIC for sqrt(s) = 200 AGeV is given.Comment: 31 pages, 15 figures, final versio

Isolated Suborders and their Application to Counting Closure Operators

In this paper we investigate the interplay between isolated suborders and closures. Isolated suborders are a special kind of suborders and can be used to diminish the number of elements of an ordered set by means of a quotient construction. The decisive point is that there are simple formulae establishing relationships between the number of closures in the original ordered set and the quotient thereof induced by isolated suborders. We show how these connections can be used to derive a recursive algorithm for counting closures, provided the ordered set under consideration contains suitable isolated suborders

On the Computation of Isolated Sublattices

In this short notice we give some ideas how to compute isolated sublattices which can be used to derive a recursive algorithm for the computation of the number of closure operators on a finite lattice. We give an asymptoticaly optimal algorithm for deciding the existence and - in the case of existence - the computation of useful nontrivial isolated summit sublattices. The general case (i.e., an optimal algorithm for the computation of general nontrivial useful isolated sublattices) remains unsolved, however, we try to give some ideas and hints for future research

Isolated Sublattices and Their Application to Counting Closure Operators

This paper investigates the interplay between isolated sublattices and closure operators. Isolated sublattices are a special kind of sublattices which can serve to diminish the number of elements of a lattice by means of a quotient. At the same time, there are simple formulae for the relationship between the number of closure operators in the original lattice and the quotient lattice induced by isolated sublattices. This connection can be used to derive an algorithm for counting closure operators, provided the lattice contains suitable isolated sublattices

Automated Control and Simulation of Dynamic Robot Teams in the Domain of CFK Production

We introduce a work flow for deriving a simulation of a lay-up process starting from a CAD file. From the CAD file, relevant informations about the plies are extracted. Together with informations about a production cell, containg the mould and robots equippes with specific grippers, an input for a PDDL solver is generated. The result of the PDDL planner is used to simulate the process in Blender

A Toolchain for Automated Control and Simulation of Robot Teams in Carbon-Fiber-Reinforced Polymers Production

This paper introduces, as a proof of concept, a tool chain for automated control and simulation of a robot team in the domain of production of carbon-fiber-reinforced polymers. The starting point is a CAD construction of a simple aviation component from which single cut pieces of carbon fiber, together withtheir properties, are extracted. Using this information and the layout of a given robot cell, various possibilities of assignments of cut pieces to grippers and robots or robot teams are determined. Subsequently, two approaches using an PDDL solver are introduced, with the goal of finding a scheduling for the lay-up process. Finally, the resulting process is simulated using a physics and rendering engine. The main purpose of this paper is to show the feasibility of such an approach; we do not concentrate on the optimization of single process steps and other details. Due to the modular structure of our approach, extensions and optimizations of the single blocks are easy to integrate. At the moment, digitization and automated control are little explored areas in the domain of production technology using pick and place processes in the aerospace industry. We think that our work will lead to further research in this direction

Components and acyclicity of graphs. An exercise in combining precision with concision

Central to algorithmic graph theory are the concepts of acyclicity and strongly connected components of a graph, and the related search algorithms. This article is about combining mathematical precision and concision in the presentation of these concepts. Concise formulations are given for, for example, the reflexive-transitive reduction of an acyclic graph, reachability properties of acyclic graphs and their relation to the fundamental concept of “definiteness”, and the decomposition of paths in a graph via the identification of its strongly connected components and a pathwise homomorphic acyclic subgraph. The relevant properties are established by precise algebraic calculation. The combination of concision and precision is achieved by the use of point-free relation algebra capturing the algebraic properties of paths in graphs, as opposed to the use of pointwise reasoning about paths between nodes in graphs

Distraction Potential of Vehicle-Based On-Road Projection

With regard to autonomous driving, on-road projections cannot only be used for communication with the driver but also with other road users. Our study aims to investigate the distraction potential for other road users when on-road projections (e.g., for driver assistance) are used to communicate with the driver of the projecting vehicle. We perform this investigation in a blind study with 38 test persons who are overtaken six times on a constant motorway section by the projection vehicle. The distraction potential is examined with an eye-tracking system, which detects the direction of the subjects’ gaze. In addition, the subjects’ physiological perception of the headlight projection is recorded with a questionnaire afterward. Several test subjects looked at the projection for less than one second, which is well below the critical threshold for the distraction of 1.6 s. In the interviews, on the other hand, only one of the 38 test persons stated that a projection on the road was recognized. For the examined scenario, it is therefore deduced that on-road projections with the selected symbol shape and brightness do not lead to critical distraction

Requirements for Automotive LiDAR Systems

Light detection and ranging (LiDAR) are fundamental sensors that help driving tasks for autonomous driving at various levels. Commercially available systems come in different specialized design schemes and involve plenty of specifications. In the literature, there are insufficient representations of the technical requirements for LiDAR systems in the automotive context, such as range, detection quality, resolving power, field of view, and eye safety. For this reason, the requirements above require to be derived based on ADAS functions. The requirements for various key LiDAR metrics, including detection range, field of view, angular resolution, and laser safety, are analyzed in this paper. LiDAR systems are available with various radiation patterns that significantly impact on detection range. Therefore, the detection range under various radiation patterns is firstly investigated in this paper. Based on ADAS functions, the required detection range and field of view for LiDAR systems are examined, taking into account various travel speeds to avoid collision and the coverage of the entire lane width. Furthermore, the angular resolution limits are obtained utilizing the KITTI dataset and exemplary 3D detection algorithms. Finally, the maximum detection ranges for the different radiation patterns are compared under the consideration of derived requirements and laser safety