Positive feedback stabilization of centrifugal compressor surge

Stable operation of axial and centrifugal compressors is limited towards low mass flows due to the occurrence of surge. The stable operating region can be enlarged by active control. In this study, we use a control valve which is fully closed in the desired operating point and only opens to stabilize the system around this point. As a result, only nonnegative control values are allowed, which complicates the controller design considerably. A novel positive feedback controller is proposed which is based on the pole placement technique. This controller has been successfully applied to a laboratory-scale gas turbine installation. Initial experiments show that the surge point mass flow can be reduced by at least 7%. Using this efficient control strategy, stable operation in the desired operating point is maintained with small average control valve mass flow.     

Almost output synchronization for heterogeneous time‐varying networks for a class of non‐introspective,nonlinear agents without exchange of controller states

We consider almost output synchronization for directed heterogeneous time‐varying networks where agents are non‐introspective (i.e., agents have no access to their own states or outputs) in the presence of external disturbances. The nonlinear agents have a triangular structure and are globally Lipschitz continuous. The network can be time‐varying with network switches occurring at arbitrary moments. A purely decentralized time‐invariant protocol based on a low‐gain and high‐gain method is designed for each agent to achieve almost output synchronization while reducing the impact of disturbances on the output synchronization error. Copyright © 2016 John Wiley & Sons, Ltd.     

The Online Market Observatory: A Domain Model Approach

The "Semantic Market Monitoring" (SEMAMO) project is intended to provide a flexible empirical instrument for the permanent collection of data -- notably, prices -- about products and services on offeneric online market observatory, SEMAMO capitalizes on a uniform data processing scheme covering all stages from automatic data capture using configurable mediators, through integration of Web-extracted data from multiple sources and their long-term storage in a persistent econometric database, up to statistical analyses feeding into flexible reporting functions. Based on a self-contained specification framework describing formally, by means of explicit models capturing market semantics, the online markets to be tracked, SEMAMO economizes the derivation of individual market monitoring applications. During run-time, a SEMAMO instance then seeks to adaptively optimize data quality and observation e±ciency based on both, previously gathered market evidence and customer-defined reporting requirements. The framework is evaluated experimentally in a practical application to online tourism.     

Simulation of Flat Belt Running

This paper deals with the lateral running behaviour of flat belts which can be found in industrial production processes (such as steel, paper or plastics) as continuous running process bands as well as transport bands for conveying purposes. Without any guidance measures, flat belts supported and driven by cylindrical pulleys run in an unstable condition, therefore angled pulley systems are employed for flat belt guidance. This paper deals with a mechanical simulation model for the guiding effect of a three‐pulley configuration with the focus on the geometrical‐mechanical relations. The belt's lateral movement as well as its bending stress during the guiding process is calculated. The aim of this investigation is to select pulley positions and shift directions that have adequate steering features despite low belt strain. To avoid instable lateral running conditions when applying an automatic controlled guidance system, proper positions for the belt edge detector are discussed. This paper is a cooperation between Vienna University of Technology, Upper Austria University of Applied Sciences and industrial partners who employ angled pulleys for flat belt guidance. The presented simulation method has been successfully applied for the optimisation of the configuration of the pulleys for a flat steel process belt in the new development of a drying system.     

Front glass thickness requirements for high resolution polarized stereoscopic displays: A simulation platform

The tendency of the display market is towards displays with higher resolutions. Therefore, patterned retarder‐based stereoscopic displays require smaller front glass thickness to maintain good vertical viewing angle and limited crosstalk. To properly design these stereoscopic displays and quantify these requirements, we developed a simulation platform to predict radiance, polarization profile, and crosstalk over viewing angles and over wavelengths. Tunable parameters such as the distance between the pixels and the patterned retarder, and the optical properties of the patterned retarder are included. The simulation platform has been validated by comparing outcomes of simulations with measurements. We predict crosstalk accounting for both the human eye field of view and the diameter of the pupil. We found that to obtain a vertical viewing angle of at least ± 30° and crosstalk of at most 0.11 for a display with a pixel pitch beyond 0.27 mm, the display should include black absorbers, and the thickness of the front glass should be at most 0.5 mm. For higher resolution displays (pixel pitch no more than 0.21 mm), a front glass thickness at most 0.15 mm is required to produce a vertical viewing angle beyond ± 14° and a minimum viewing distance of 0.3 m.     

On the rapid orbital attitude control of manned and cargo spacecraft <Emphasis Type="Italic">Soyuz MS</Emphasis> and <Emphasis Type="Italic">Progress MS</Emphasis>

An algorithm for the rapid construction of the orbital coordinate system (OCS) used in the control system of the manned and cargo spacecraft Soyuz MS and Progress MS is considered. The algorithm is used to speed up the current determination of the state vector value using the satellite navigation equipment immediately after the spacecraft is placed into the Earth’s artificial satellite orbit and the launch vehicle is separated. The proposed algorithm is based on an a priori knowledge of the launch vehicle’s attitude parameters at the time of separation and on the angular velocity (AV) measurements available on board after the start of the strapdown inertial navigation system (SINS). The efficiency of the rapid orbital attitude control algorithm is confirmed by the results of the mathematical modeling and flight development tests.     

Artful surfaces: an ethnographic study exploring the use of space in design studios

A largely overlooked aspect of creative design practices is how physical space in design studios plays a role in supporting designers' everyday work. In particular, studio surfaces such as designers' desks, office walls, notice boards, clipboards and drawing boards are full of informative, inspirational and creative artefacts such as, sketches, drawings, posters, story-boards and Post-it notes. Studio surfaces are not just the carriers of information but importantly they are sites of methodic design practices, i.e. they indicate, to an extent, how design is being carried out. This article describes the results of an ethnographic study on the use of workplace surfaces in design studios, from two academic design departments. Using the field study results, the article introduces an idea of ‘artful surfaces’. Artful surfaces emphasise how artfully designers integrate these surfaces into their everyday work and how the organisation of these surfaces comes about helping designers in accomplishing their creative and innovative design practices. Using examples from the field study, the article shows that artful surfaces have both functional and inspirational characteristics. From the field study, three types of artful surfaces are identified: personal; shared; and project-specific. The article suggests that a greater insight into how these artful surfaces are created and used could lead to better design of novel display technologies to support designers' everyday work.     

Solvability conditions and design for synchronization of discrete‐time multiagent systems

This paper provides solvability conditions for state synchronization with homogeneous discrete‐time multiagent systems with a directed and weighted communication network under partial‐ or full‐state coupling. Our solvability conditions reveal that the synchronization problem is solvable for all possible, a priori given, set of graphs associated with a communication network only under the condition that the agents are at most weakly unstable (ie, agents have all eigenvalues in the closed unit disc). However, if an upper bound on the eigenvalues inside the unit disc of the row stochastic matrices associated with any graph in a given set of graphs is known, then one can achieve synchronization for a class of unstable agents. We provide protocol design for at most weakly unstable agents based on a direct eigenstructure assignment method and a standard H₂ discrete‐time algebraic Riccati equation. We also provide protocol design for strictly unstable agents (ie, agents have at least one eigenvalue outside the unit disc) based on the standard H₂ discrete‐time algebraic Riccati equation.     

The SAPR/3 Business Framework

This paper gives a synopsis of the SAP R/3 Business Framework. The architecture is based on an object-orientated approach using business objects and Business Components. Using this architecture together with a distribution model, distributed applications (distributed business processes) can be mapped and implemented. The spectrum of distributed applications extends from the simple integration of two components using a few interfaces to the integration of many components distributed across the globe.