Adaptive scene dependent filters for segmentation and online learning of visual objects

Steil JJ, Götting M, Wersing H, Körner E, Ritter H. Adaptive scene dependent filters for segmentation and online learning of visual objects. Neurocomputing. 2007;70(7-9):1235-1246

Active Learning for Image Recognition Using a Visualization-Based User Interface

Limberg C, Krieger K, Wersing H, Ritter H. Active Learning for Image Recognition Using a Visualization-Based User Interface. In: Tetko IV, Kůrková V, Karpov P, Theis F, eds. Artificial Neural Networks and Machine Learning – ICANN 2019: Deep Learning. Lecture Notes in Computer Science. Vol 11728. Cham: Springer; 2019: 495-506

DEVELOPING A FLEXIBLE THERMAL PROTECTION SYSTEM FOR MARS ENTRY: SYSTEMS ENGINEERING, MECHANICAL DESIGN AND MANUFACTURING PROCESSES

A flexible thermal protection system (FTPS) is needed to enable the use of deployable and inflatable hypersonic decelerators. These decelerators could increase entry vehicle drag area beyond that of a conventional rigid heatshield, enabling Mars missions with greater landed masses and higher-elevation landing sites than can be currently achieved. An FTPS is essential to protect the hypersonic decelerator and payload from atmospheric entry aerothermal loads; conventional rigid heatshields are constrained by the available space within the launcher fairing. An ESA technology development is ongoing to raise the European FTPS technology readiness level from 2 to 3 and to define an FTPS that may be integrated with a Mars-entry inflatable hypersonic decelerator. This paper presents the FTPS requirements, material selection, mechanical characterisation and manufacturing technique development

DEVELOPING A FLEXIBLE THERMAL PROTECTION SYSTEM FOR MARS ENTRY: THERMAL DESIGN AND TESTING

Flexible Thermal Protection Systems (FTPS) are a key technology needed to enable novel inflatable and deployable aerodynamic decelerators. A development campaign is underway to raise the European FTPS technology readiness level from 2 to 3, advancing design and test capability. An FTPS suitable for a reference Mars landing mission is being designed. The FTPS has three functional layers: outer layers of Nextel 440 BF-20 fabric; insulation layers of SIGRATHERM GFA5 graphite felt and Pyrogel XTE aerogel; and a silicone-coated Kevlar fabric gas barrier. The density, specific heat capacity and thermal diffusivity of candidate materials was measured. Results were then used in thermal simulations to define a baseline layup. The layup thermal conductance was assessed in thermocouple-instrumented layup tests. Layups including joints were also tested and found not to have significantly different conductance. Layup test thermal simulations showed good agreement with the experimental data. Future work will include arc-jet tests and thermal model optimisation

Initial Public Offerings and the Firm Location

The firm geographic location matters in IPOs because investors have a strong preference for newly issued local stocks and provide abnormal demand in local offerings. Using equity holdings data for more than 53,000 households, we show the probability to participate to the stock market and the proportion of the equity wealth is abnormally increasing with the volume of the IPOs inside the investor region. Upon nearly the universe of the 167,515 going public and private domestic manufacturing firms, we provide consistent evidence that the isolated private firms have higher probability to go public, larger IPO underpricing cross-sectional average and volatility, and less pronounced long-run under-performance. Similar but opposite evidence holds for the local concentration of the investor wealth. These effects are economically relevant and robust to local delistings, IPO market timing, agglomeration economies, firm location endogeneity, self-selection bias, and information asymmetries, among others. Findings suggest IPO waves have a strong geographic component, highlight that underwriters significantly under-estimate the local demand component thus leaving unexpected money on the table, and support state-contingent but constant investor propensity for risk

Challenges for the Heatshield Development of Sample Return Missions - An Overview on European Sample Return Studies and Requirements

This presentation was part of the session : Sample Return ChallengesSixth International Planetary Probe WorkshopThe atmospheric entry of the Earth return capsule of sample return mission is one of the most critical phases of sample return missions. The Earth return from extraterrestrial bodies (e.g. Mars, comets or asteroids) involves a hyperbolic entry with entry velocities of typically above 12 km/s, resulting in peak heat fluxes in the order of 10 MW/m(2) and heat loads up to 200 MJ/m(2). While during a classical re-entry from Earth-orbit the heat flux is basically limited to convective fluxes, additionally radiative fluxes become increasingly important at entry velocities above 12 km/s. In addition, since the Earth return capsule is subject to a "double" delta-V (to the object and back to Earth), the return capsule and its heatshield have to conform to a very stringent mass budget. Further, surface recession due to ablation and abrasion effects needs to remain limited in order to guarantee the aerodynamic stability. This requires the availability of a highly efficient light-weight ablator material. In a dedicated study a screening of existing European ablators was performed to assess their suitability. Unfortunately, it turned out that none of the materials, which were developed in front of very different requirements, is suitable to sustain the very high heat fluxes while coping with the mass requirement. Dedicated development is therefore initiated to tailor materials towards the stringent requirements. Another important aspect is the availability of plasma facilities for the qualification of the materials. Such high enthalpy facility needs to be able to reproduce the extreme heat fluxes at representative dynamic pressure levels and simulating the high radiation level. Additionally it would be beneficial to assess the dynamic stability of the entry capsule using free flight ballistic tests. The paper will provide an overview on the main challenges involved in the development of the heatshield for the Earth re-entry capsule of sample return missions, resulting from different ESA studies to Mars and asteroids. This will include system aspects, the choice of the TPS material and its qualification, flight path stability and reliability. Preliminary technology roadmaps will also be presented

HIGH TEMPERATURE THERMAL CONDUCTIVITY MEASUREMENT APPARATUS

Reliable dimensioning of highly efficient thermal protection for entry or re-entry applications depends on an accurate knowledge of the thermal conductivity of the considered materials. The fibre and foam insulations, as well as ablator char, used in such thermal protection systems are porous materials, where the thermal conductivity varies with both, applied temperature and ambient pressure. Precise thermal conductivity measurements in the lower temperature range and for isotropic insulations are state-of-the art. The transfer of well-established lower temperature measurement princi-ples to very high temperatures and to non-isotropic insulations is a challenge. The German aerospace center (DLR) owns a facility of adequate size which enables thermal conductivity measurements at high temperatures up to 1600°C and for controllable ambient pressures between 1 mbar and ambient pressure. This facility has been used in previous projects, however, the quality of steady state thermal conductivity measurements was not satisfactorily in particular for reduced pressure levels. This is caused by uncontrolled lateral heat exchanges at the test specimen surface. Control of these lateral heat exchanges is therefore the key for improvement of measurement accuracy. With this in mind, a test setup for measurements under varying temperatures up to 1600°C and for pressures between 1 mbar and ambient pressure has been developed as part of ESA’s Innovation Triangle Initiative. This test setup is not only applicable to today’s most advanced insulations, i.e. to nanoporous insulations and to anisotropic insulation sys-tems like internal multiscreen insulation (IMI), but also to the direct measurement of ablator char thermal conductivity. At first, the measurement of thermal conductivity and the therefore developed test setup HitCon are described. Next, the results from a measurement campaign, conducted to verify the functionality of the design, are shown, followed by sen-sitivity analysis for further improvement of the test setup

Feature binding and relaxation labeling with the competitive layer model

Abstract. We discuss the relation of the Competitive Layer Model (CLM) to Relaxation Labeling (RL) with regard to feature binding and labeling problems. The CLM uses cooperative and competitive interactions to partition a set of input features into groups by energy minimization. As we show, the stable attractors of the CLM provide consistent and unambiguous labelings in the sense of RL and we give an efficient stochastic simulation procedure for their identification. In addition to binding the CLM exhibits contextual activity modulation to represent stimulus salience. We incorporate deterministic annealing for avoidance of local minima and show how figure-ground segmentation and grouping can be combined for the CLM application of contour grouping on a real image.

Backtracking Deterministic Annealing For Constraint Satisfaction Problems

We present a new deterministic annealing approach to the solution of quadratic constraint satisfaction problems with complex interlocking constraints, such as exemplified in polyomino tiling puzzles. We first analyze the dynamical properties of the solution strategies implemented by deterministic annealing (DA) in the analog neural representation of Potts-MeanField (PMF) and penalty-function-based competitive layer model (CLM) neural networks, revealing a similar mechanism. The key idea of our extension of these plain DA approaches is motivated by classical backtracking algorithms. We show that their ability for iterative local pruning of the search space can be implemented within the framework of DA by introducing local temperature parameters which are "reheated" when locally unresolved conflicts occur. To achieve the pruning of the search space, reheating is accompanied by a modification of the constraint-implementing weight matrix to reduce the chance of reentering the same local co..

Towards A Web Based Simulation Environment

Existing Simulation and Animation (S&A) software tools are typically platform dependent and do not particularly lend themselves to cooperative work within either the Internet or an Intranet. This paper describes: . Basic approaches toward achieving Web compliance for S&A software; and . Specific components for potential use in an open, platform independent simulation environment for the Internet or for corporate Intranets