Ostfalia University of Applied Sciences

Wolfenbuttel, Germany
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Priss U.,Ostfalia University of Applied Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2017

This paper views Formal Concept Analysis (FCA) from an educational perspective. Novice users of FCA who are not mathematicians might find diagrams of concept lattices counter-intuitive and challenging to read. According to educational theory, learning thresholds are concepts that are difficult to learn and easy to be misunderstood. Experts of a domain are often not aware of such learning thresholds. This paper explores learning thresholds occurring in FCA teaching material drawing on examples from a discrete structures class taught to first year computer science students. © Springer International Publishing AG 2017.

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: SST.2012.5.2-2. | Award Amount: 3.92M | Year: 2012

In a context of wide use of transport, it is necessary to increase efficiency of the different transport modes as well as their interaction. To that effect, rail transport will play an important role in the future by increasing its capacity. Thus, it would be necessary to strength the competitiveness of railway ensuring a sustainable, efficient and safe service. In that sense, it is essential to improve the interoperability and safety of national networks in order to promote a single European Rail Market. Nevertheless, there are still several barriers to overcome as a consequence of the lack of a common definition of standards at European level. Within this framework, the main objective targeted by the OPTIRAIL project aims at developing a new tool, based on Fuzzy and Computational Intelligence techniques and validated through two case studies, that will enable the better cross-border coordination for decision making of railway infrastructure maintenance across the European railway corridors. In order to be able to achieve the exposed objective, the project Consortium is comprised of a well-balanced group of 9 partners from 6 European countries with complementary skills and expertise, including all the necessary profiles to deal with the scheduled project work plan. Furthermore, non-participant railway administrators have shown their interest and commitment to the project. This interdisciplinary group of the railway managers, railway suppliers, software & embedded systems developers, and technological R&D centres are strongly committed to efficiently coordinate their resources over the 36 months duration of the project in order to be able to reach all expected project outcomes. The estimated overall budget of the project is 3.916.343,40 .

Schulze D.,Ostfalia University of Applied Sciences
Advanced Powder Technology | Year: 2011

In 2008 a round robin project on ring shear testers was initiated in order to determine a range of results for a defined bulk solid (limestone powder CRM-116), similar to a round robin project with Jenike shear testers carried out in the 1980s. All users of automatic ring shear testers RST-XS or RST-01.pc were invited to take part. Twenty-seven labs supplied results. Finally, per stress level up to 60 yield loci (21 labs) measured with the RST-XS, and up to 19 yield loci (10 labs) measured with the RST-01.pc have been received. Compared to the above mentioned tests on Jenike-type shear testers, both ring shear testers provide clearly smaller standard deviations. Thus, despite different ambient conditions, the range of results is quite narrow. With the mean values and standard deviations calculated from the ring shear tester results a kind of "reference range" is defined. This range should be matched with a certain probability with the results of future tests with the standard powder if the instructions regarding stresses and ambient conditions are followed. Thus, the results provide orientation to all users of ring shear testers RST-XS and RST-01.pc. © 2011 The Society of Powder Technology Japan.

Mercorelli P.,Ostfalia University of Applied Sciences
Kybernetika | Year: 2010

This paper investigates the geometric and structural characteristics involved in the control of general mechanisms and manipulation systems. These systems consist of multiple cooperating linkages that interact with a reference member of the mechanism (the "object") by means of contacts on any available part of their links. Grasp and manipulation of an object by the human hand is taken as a paradigmatic example for this class of manipulators. Special attention is devoted to the output specification and its controllability. An example design of a force controller using algebraic output feedback is presented at the end of this paper. In this example, a matrix representing a static output feedback is designed. The coefficients of this matrix are the weights for the sensed outputs. With the approach proposed in this paper, a robust decoupling is obtained between the output feedback and the contact forces and joint positions.

Su Y.,Lüneburg University | Su Y.,Ostfalia University of Applied Sciences | Mennerich A.,Ostfalia University of Applied Sciences | Urban B.,Lüneburg University
Water Research | Year: 2011

A wastewater-born and settleable algal-bacterial culture, cultivated in a stirred tank photobioreactor under lab conditions, was used to remove the carbon and nutrients in municipal wastewater and accumulate biomass simultaneously. The algal-bacterial culture showed good settleable property and could totally settle down over 20 min, resulting in a reduction of total suspended solids from an initial 1.84 to 0.016 g/l. The average removal efficiencies of chemical oxygen demand, total kjeldahl nitrogen and phosphate were 98.2 ± 1.3%, 88.3 ± 1.6% and 64.8 ± 1.0% within 8 days, respectively, while the average biomass productivity was 10.9 ± 1.1 g/m 2·d. Accumulation into biomass, identified as the main nitrogen and phosphorus removal mechanism, accounted for 44.9 ± 0.4% and 61.6 ± 0.5% of total inlet nitrogen and phosphorus, respectively. Microscopic analysis showed the main algae species in the bioreactor were filamentous blue-green algae. Furthermore, denaturing gradient gel electrophoresis and 16S rDNA gene sequencing revealed that the main bacteria present in the photobioreactor were consortia with sequences similar to those of Flavobacteria, Gammaproteobacteria, Bacteroidia and Betaproteobacteria. This study explores a better understanding of an algae-bacteria system and offers new information on further usage of biomass accumulated during treatment. © 2011 Elsevier Ltd.

Fabbrini A.,University of Siena | Garulli A.,University of Siena | Mercorelli P.,Ostfalia University of Applied Sciences
IEEE Transactions on Control Systems Technology | Year: 2012

Camless internal combustion engines offer improvements over traditional engines in terms of torque performance, reduction of emissions, reduction of pumping losses and fuel economy. Theoretically, electromagnetic valve actuators offer the highest potentials for improving efficiency due to their control flexibility. For real applications, however, the valve actuators developed so far suffer from high power consumption and other control problems. One key point is the design of the reference trajectory to be tracked by the closed loop controller. In this brief, a design technique aimed at minimizing power consumption is proposed. A constrained optimization problem is formulated and its solution is approximated by exploiting local flatness and physical properties of the system. The performance of the designed trajectory is validated via an industrial simulator of the valve actuator. © 2011 IEEE.

Su Y.,Lüneburg University | Su Y.,Ostfalia University of Applied Sciences | Mennerich A.,Ostfalia University of Applied Sciences | Urban B.,Lüneburg University
Bioresource Technology | Year: 2012

An algal-bacterial culture, composed of wastewater-born algae and activated sludge, was cultivated to treat domestic wastewater and accumulate biomass simultaneously. The influence of algae and sludge inoculation ratios on the treatment efficiency and the settleability of the accumulated biomass were investigated. There was no significant effect of the inoculation ratios on the chemical oxygen demand removal. Comparatively, the nutrients removal and related mechanism were varied with different inoculation ratios. The highest nitrogen and phosphorus removal efficiencies were observed with 5:1 (algae/sludge) culture (91.0. ±. 7.0% and 93.5. ±. 2.5%, respectively) within 10. days, which was 5-40% higher and 2-4. days faster than those with other inoculation ratios. The biomass settleability was improved with the assistance of sludge, and the 1:5 (algae/sludge) culture showed the best settleability. Furthermore, 16S rDNA gene analysis showed that the bacterial communities were varying with different algae and sludge inoculation ratios and some specific bacteria were enriched during operation. © 2011 Elsevier Ltd.

Mercorelli P.,Ostfalia University of Applied Sciences
Proceedings of the IEEE Conference on Decision and Control | Year: 2011

In this paper, the design and operation of a special electromagnetic motor as a variable engine valve actuator are presented. Further, this paper presents feasible approximated velocity switching estimator based on measurements of current and input voltage to achieve sensorless control. This approach avoids a more complex structure for the observer and yields an particular control strategy with an acceptable performance. In general, this approach can represent a viable strategy to build reduced-order observer to estimate not only velocity but also position of a such as type of systems through the measurement of input current and input voltage. This control strategy is presented and discussed as well. Computer simulations of the sensorless control structure are presented in which results are visible in the closed-loop control. © 2011 IEEE.

Mercorelli P.,Ostfalia University of Applied Sciences
PRECEDE 2011 - Workshop on Predictive Control of Electrical Drives and Power Electronics | Year: 2011

This paper deals with a hybrid actuator composed by a piezo and a hydraulic part and with a switching Model Predictive Control (MPC) Structure for camless engine motor applications. In a precision control problem, nonlinearities such as hysteresis, creep etc. must be taken into account. In this paper the Preisach dynamic model with the above mentioned hysteresis is considered together with a robust switching MPC utilized to manage the hysteresis nonlinearity. Simulations with real data are shown. © 2011 IEEE.

Mercorelli P.,Ostfalia University of Applied Sciences
IEEE/ASME Transactions on Mechatronics | Year: 2012

Real-control applications of any nature can be affected by saturation limits that generate windup. When saturation occurs in a device its performance deteriorates. Electromagnetic actuators for industrial applications are being utilized ever more frequently for positioning and tracking control problems. One of the most important requirements in tracking trajectories is to achieve a soft landing, which guarantees reliable functionality and a longer component life. This paper presents an application of a typical electromagnetic actuator through a hardware-in-the-loop structure in which a soft landing is required in the tracking trajectory. To avoid saturation, which prevents soft landings, a specific new control law is developed. The proposed technique is based on a cyclic adaptive current preaction combined with a sliding surface. The technique consists of building a control law so that the position of the valve at which its velocity assumes its minimum is as close as possible to the landing point. At this time point, the magnetic force compensates for the elastic force and the preaction component is switched off. An experimental setup using a hardware-in-the-loop to allow a pilot investigation, model validation, and testing before implementation is considered. Real measurements of the proposed method are shown. © 2011 IEEE.

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