Euromech Colloquium 509: Vehicle Aerodynamics. External Aerodynamics of Railway Vehicles, Trucks, Buses and Cars - Proceedings

During the 509th Colloquium of the Euromech society, held from March 24th & 25th at TU Berlin, fifty leading researchers from all over europe discussed various topics affecting both road vehicle as well as railway vehicle aerodynamics, especially drag reduction (with road vehicles), cross wind stability (with trains) and wake analysis (with both). With the increasing service speed of modern high-speed railway traffic, aerodynamic aspects are gaining importance. The aerodynamic research topics comprise both pure performance improvements, such as the continuous lowering of aerodynamic drag for energy efficiency, as well as safety relevant topics, such as cross-wind stability. The latter topic was most recently brought to attention when a swiss narrow-gauge train overturned during the severe storm Kyrill in january 2007. The shape of the train head usually has largest influence on cross wind stability. Slipstream effects of passing trains cause aerodynamic loads on objects and passengers waiting at platforms. The strength of the slipstream is determined by both the boundary layer development along the length of the train and the wake developing behind the tail of the train. Since high-speed trains can be considered to be as smooth as technically possible, attention is drawn to the wake region. The wake of the train again is also one important factor for the total drag of a train. Due to the fact that trains are bidirectional, optimisation of the leading car of a train with respect to drag and cross wind performance while simultaneously minimising the wake of the train for drag and slipstream performance is a great challenge. Modern optimisation tools are used to aid this multi-parameter multi-constraint design optimisation in conjunction with both CFD and wind tunnel investigations. Since many of the aerodynamic effects in the railway sector are of similar importance to road vehicles, the aim of the colloquium is to bridge the application of shape optimisation principles between rail- and road vehicles. Particular topics to be addressed in the colloquium are: Drag, Energy consumption and emissions: Due to increase in energy cost, drag reduction has gained focus in the past years and attention will grow in the future. Pressure induced drag is of common importance for both rail- and road vehicles. The optimisation of head- and tail shape for road vehicles as well as for bi-directional vehicles (trains) is in the focus. Interference drag between adjacent components shall also be treated. Slipstream Effects: Are a safety issue for high-train operation (Prams sucked into track due to train-induced draught flows) when trains passing platforms at high speeds. For Road vehicles, the ride stability of overtaking cars is influenced by the wake of the leading trucks and busses. Common interest is the minimisation of wake effects for both rail and road vehicles. Cross-Wind Safety, Ride stability under strong winds: Both are safety issues for rail- and road vehicles. Aerodynamic forces shall be minimised (roll moment for trains and also yaw moment for road vehicles). Strategies for Vehicle shape optimisation (head, tail and roof shape) in order to minimise aerodynamic moments. Possibilities of Flow control. Optimisation strategies: Parametrisation, analyses (CFD), Optimisation tools and methods, Application to Drag, Cross-Wind, Ride stability and Snow issue

OntoCheck: verifying ontology naming conventions and metadata completeness in Protégé 4

BACKGROUND: Although policy providers have outlined minimal metadata guidelines and naming conventions, ontologies of today still display inter- and intra-ontology heterogeneities in class labelling schemes and metadata completeness. This fact is at least partially due to missing or inappropriate tools. Software support can ease this situation and contribute to overall ontology consistency and quality by helping to enforce such conventions. OBJECTIVE: We provide a plugin for the Protégé Ontology editor to allow for easy checks on compliance towards ontology naming conventions and metadata completeness, as well as curation in case of found violations. IMPLEMENTATION: In a requirement analysis, derived from a prior standardization approach carried out within the OBO Foundry, we investigate the needed capabilities for software tools to check, curate and maintain class naming conventions. A Protégé tab plugin was implemented accordingly using the Protégé 4.1 libraries. The plugin was tested on six different ontologies. Based on these test results, the plugin could be refined, also by the integration of new functionalities. RESULTS: The new Protégé plugin, OntoCheck, allows for ontology tests to be carried out on OWL ontologies. In particular the OntoCheck plugin helps to clean up an ontology with regard to lexical heterogeneity, i.e. enforcing naming conventions and metadata completeness, meeting most of the requirements outlined for such a tool. Found test violations can be corrected to foster consistency in entity naming and meta-annotation within an artefact. Once specified, check constraints like name patterns can be stored and exchanged for later re-use. Here we describe a first version of the software, illustrate its capabilities and use within running ontology development efforts and briefly outline improvements resulting from its application. Further, we discuss OntoChecks capabilities in the context of related tools and highlight potential future expansions. CONCLUSIONS: The OntoCheck plugin facilitates labelling error detection and curation, contributing to lexical quality assurance in OWL ontologies. Ultimately, we hope this Protégé extension will ease ontology alignments as well as lexical post-processing of annotated data and hence can increase overall secondary data usage by humans and computers

Simulating the interaction of electrostatically charged particles in the inflow area of cabin air filters using a fully coupled system

Precise simulations of particulate flow through fibrous filters are essential in order to predict and enhance filtration performances. To run the computation in reasonable time, a continuum approach is commonly used to emulate the air flow. The software GeoDict [1] allows for the simulation of the complete process, ranging from calculating a flow field, tracking particles inside that field to finding collisions with porous filter media. However, this approach completely neglects particle-particle interactions although particles often carry electrostatic charges [2]. Comparing the results of GeoDict to a fully coupled system shows the influence of this simplification. The software ESPResSo [3, 4] uses such a four-way coupling combining a molecular-dynamics-like approach for partricle simulation with an integrated Lattice-Boltzmann fluid dynamics solver. Already for a simple scenario, which represents the filter media as a mesh consisting of cylindrical fibers, significant influences of the full coupling on the particle trajectories and even the collection efficiency can be observed. We decribe the modeling and setup for both approaches and present numerical results for simplified yet meaningful test cases

UAV Formation Optimization for Communication-assisted InSAR Sensing

Interferometric synthetic aperture radar (InSAR) is an increasingly important remote sensing technique that enables three-dimensional (3D) sensing applications such as the generation of accurate digital elevation models (DEMs). In this paper, we investigate the joint formation and communication resource allocation optimization for a system comprising two unmanned aerial vehicles (UAVs) to perform InSAR sensing and to transfer the acquired data to the ground. To this end, we adopt as sensing performance metrics the interferometric coherence, i.e., the local correlation between the two co-registered UAV radar images, and the height of ambiguity (HoA), which together are a measure for the accuracy with which the InSAR system can estimate the height of ground objects. In addition, an analytical expression for the coverage of the considered InSAR sensing system is derived. Our objective is to maximize the InSAR coverage while satisfying all relevant InSAR-specific sensing and communication performance metrics. To tackle the non-convexity of the formulated optimization problem, we employ alternating optimization (AO) techniques combined with successive convex approximation (SCA). Our simulation results reveal that the resulting resource allocation algorithm outperforms two benchmark schemes in terms of InSAR coverage while satisfying all sensing and real-time communication requirements. Furthermore, we highlight the importance of efficient communication resource allocation in facilitating real-time sensing and unveil the trade-off between InSAR height estimation accuracy and coverage

Production of biodiesel from animal fat using supercritical ethanol

Biodiesel is currently produced from a catalytic transesterification reaction of various types of edible and non-edible oil with methanol. The use of waste animal tallow instead of edible oils opens a route to recycle this waste. This material has the advantage of lower costs but the problem of high content of free fatty acids, becoming necessary a pre-esterification reaction that increases the cost of the catalytic process. The production of biodiesel using supercritical alcohols is appropriate for materials with high acidity and water content, therefore the use of this process with animal fat is a promising alternative. Ethanol has been used because it can be produced from biomass via fermentation resulting in a complete renewable biodiesel, instead of methanol that derives from fossil feedstocks. Two different processes have been studied: first, the direct transesterification of animal fat using supercritical ethanol and second a two-step process where the first step is a hydrolysis of the animal fat and the second step is the esterification of the resulting fatty acids. The temperature, the molar ratio ethanol:fat and the time have been modified in the different reactions to study the effect in the final conversion and the degradation of the unsaturated fatty acid esters, main inconvenient of these high temperature and pressure processes

Harmonic Analysis of Boolean Networks: Determinative Power and Perturbations

Consider a large Boolean network with a feed forward structure. Given a probability distribution on the inputs, can one find, possibly small, collections of input nodes that determine the states of most other nodes in the network? To answer this question, a notion that quantifies the determinative power of an input over the states of the nodes in the network is needed. We argue that the mutual information (MI) between a given subset of the inputs X = {X_1, ..., X_n} of some node i and its associated function f_i(X) quantifies the determinative power of this set of inputs over node i. We compare the determinative power of a set of inputs to the sensitivity to perturbations to these inputs, and find that, maybe surprisingly, an input that has large sensitivity to perturbations does not necessarily have large determinative power. However, for unate functions, which play an important role in genetic regulatory networks, we find a direct relation between MI and sensitivity to perturbations. As an application of our results, we analyze the large-scale regulatory network of Escherichia coli. We identify the most determinative nodes and show that a small subset of those reduces the overall uncertainty of the network state significantly. Furthermore, the network is found to be tolerant to perturbations of its inputs

How to Survive Dynamic Pricing Competition in E-commerce

ABSTRACT Pricing on e-commerce platforms is highly challenging. Sellers typically i) rival against dozens of competitors, ii) decide on prices for thousands of products, and iii) face steadily changing market situations. With respect to pricing, the challenge is to circumvent the curse of dimensionality to dynamically price products for a given market situation in a timely manner. In this project, we create a stochastic pricing model by analyzing recorded market data. This pricing model can be applied ad-hoc in less than a millisecond per item, allowing us to react immediately to new market situations. Our pricing approach is currently being applied in practice by a large German book seller on Amazon and outperforms the previous rule-based strategy by over 20% with respect to cash-in per book. CCS Concepts •Applied computing → Online shopping; E-commerce infrastructure; Decision analysis; Keywords Dynamic Pricing; Oligopoly Competition; Online Markets; Demand Estimation CHALLENGE Modern market platforms such as Amazon Marketplace or eBay are highly dynamic as sellers can observe the current market situation at any time and adjust their prices instantly. For sellers that handle large inventories, this dynamic is hard to manage as an optimal pricing decision requires handling a multitude of dimensions for each competitor (e.g., price, quality, shipping time, shipping costs, rating). Moreover, financial aspects such as discounting as well as inventory holding costs have to be taken into account. In this project, we partner with adanbo GmbH. adanbo is among the top 10 sellers for used books on Amazon in Germany with an inventory of over 80,000 distinct books (ISBN), each with multiple items (1-20). Our seller can decide -to some extent -on the replenishment of used books (by choosing purchase prices). However, supply is limited and it is not possible to directly reorder specific books. Hence, the challenge is to extract as much profit as pos- Copyright is held by the author(s). sible from a given number of books (inventory level) in a reasonable amount of time. The pricing strategy of our project partner is characterized by a rule-based system that has been developed over the past years by carefully adjusting rules to lessons learned from selling books on Amazon. As our project partner has more than 10 years of experience in the market, we consider his strategy to be effective and accurate. However, market dynamics are increasingly sophisticated making rule-based strategies increasingly hard to handle and maintain. Our goal is to develop a pricing strategy that maximizes expected discounted long-term profits while taking into account the constraints mentioned above. We seek to compute data-driven pricing strategies that are applicable even for large inventories. DATA-DRIVEN PRICING MODEL The project is devoted to revenue managemen

Two-dimensional Fermi liquids sustain surprising roton-like plasmons beyond the particle-hole band

International audienceUsing inelastic neutron scattering, we have investigated the elementary excitations of an isotropic two-dimensional Fermi liquid, 3He adsorbed on graphite. We provide in this article a detailed account of the principles and methods which allowed measuring for the first time inelastic spectra on a liquid monolayer of 3He, a strong neutron absorber. We also summarise the results presented at this Conference, and review our recent experimental and theoretical work on this this interacting many-body system. At low wave-vectors, near the edge of the particle-hole band, a mode identified as the zero-sound excitation by comparison to our theoretical calculations, is found as predicted at energies much lower than in bulk 3He. The mode enters the particle-hole band, where it undergoes Landau damping. Surprisingly, however, intensity is observed in the neutron spectra at wave-vectors larger than twice the Fermi wavevector. This new branch is interpreted as the high wave-vector continuation of the zero-sound mode, in agreement with the theory. The results open new perspectives in the understanding of the dynamics of correlated fermions