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Mariam T.,University of Wollongong | Mariam T.,Heilbronn University of Applied Sciences | Nghiem L.D.,University of Wollongong
Desalination | Year: 2010

In this study, treatment of landfill leachate using a novel electrocoagulation - nanofiltration (EC-NF) hybrid system was investigated. Leachate sample was collected from Whytes Gully landfill in Wollongong, Australia. The performance of electrocoagulation (EC) using aluminium electrodes as a pretreatment step for the nanofiltration process was compared against a conventional chemical coagulation (CC) process. Results reported here indicate that electrocoagulation is superior over the conventional coagulation process with respect to total organic carbon (TOC) and turbidity removal. At the optimum reaction time, TOC and turbidity removals by the electrocoagulation process were 67% and 80%, respectively. In comparison, at the optimum dosage of Al2(SO4)3 obtained by a standard jar testing procedure, TOC and turbidity removals by the chemical coagulation process were only 10% and 65%, respectively. It is noteworthy that the amount of aluminium released by the electrocoagulation process to the solution was significantly higher than the optimum dosage of the chemical coagulation process. Therefore, better performance of the electrocoagulation process can possibly be explained by the higher coagulation concentration and the formation of polymeric aluminium which is known to be more effective for small organic compounds which are prevalent in landfill leachate. A remarkable difference between electrocoagulation and chemical coagulation pretreatment was also observed with respect to fouling mitigation in a subsequent nanofiltration process. For the two different nanofiltration membranes (NF 270 and SR2) used in this study, severe membrane fouling was evident when filtering raw landfill leachate or chemical coagulation pretreated landfill leachate. In contrast, fouling was not observed with an electrocoagulation pretreated feed solution. However, the use of electrocoagulation pretreatment did not result in any improvement in treated effluent quality by the hybrid system. Over all, there was no discernible variation between the EC - NF and CC - NF hybrid systems in their TOC and turbidity removals, which were approximately 92% and 99%, respectively. The reported results demonstrate that an EC - NF hybrid system can be a promising candidate for landfill leachate treatment, particularly for small and decentralised landfills where simplicity and robustness are required. Crown Copyright © 2009.


Maier C.,University of Heidelberg | Maier C.,Heilbronn University of Applied Sciences | Dickhaus H.,University of Heidelberg
Computing in Cardiology | Year: 2013

In the context of the CinC-challenge 2013 we present a method for fetal QRS detection in abdominal ECG recordings. Maternal ECG attenuation is based on PQSRT template subtraction and subsequent elimination of the first three principal components. Fetal QRS detection follows a matched filtering approach with an impulse-train filter and a second filter with complementary impulse response. The interspacing of the impulses corresponds to putative fetal RR intervals and is systematically varied, where the relation of both filter outputs permits assessment of the signal-to-noise ratio. In epochs of 1s duration, we use this information to dynamically combine information from an arbitrary number of abdominal channels into a virtual channel, and estimate the local RR interval and initial fetal QRS positions. In a final step these candidate positions are refined using a dynamic programming approach with constraints on SNR, signal amplitude and continuity of RR intervals. In the test set of 100 4-channel recordings (60s, 1 kHz), we observed good detection accuracy up to moderate SNRs, with an overall RMS-error of 9.35 ms versus reference RR-intervals from scalp recordings. © 2013 CCAL.


Muller A.,University of Duisburg - Essen | Hufnagel T.,Heilbronn University of Applied Sciences
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011

While redundantly actuated PKM (RA-PKM) possess desirable kinematic and dynamic properties, their control is impeded by the occurrence of antagonistic control forces. Such forces are observed in non-linear model-based as well as in decentralized control schemes. In this paper it is outlined that such antagonistic forces are inherent to the decentralized control of RA-PKM, and also that calibration errors and finite encoder resolutions cause antagonistic control forces and excited vibrations, hence energy loss and instabilities. The effect of measurement errors and the stability of individual PD and computed torque control is analyzed. They are shown to yield asymptotically stable setpoint control. A central result of this paper is a projection method for the elimination of contradicting control commands. This method is valid independently of the actual control scheme. Experimental results are presented for a 2RRR/RR implementation. The results confirm that the proposed scheme reduces antagonistic control forces up to measurement errors and model uncertainties. © 2011 IEEE.


Mller A.,University of Duisburg - Essen | Hufnagel T.,Heilbronn University of Applied Sciences
Robotics and Autonomous Systems | Year: 2012

Model-based control of parallel kinematics machines (PKM) relies on computationally efficient formulations in terms of a set of independent joint coordinates. Since PKM models are commonly expressed in terms of actuator or end-effector coordinates the models are not valid at input- or output-singularities, respectively. Moreover input-singularities limit the motion range of PKM. Actuation redundancy is a means to increase the singularity-free range of motion. However, due to the redundancy only a subset of the actuator coordinates constitute independent coordinates. This subset corresponds to the actuator coordinates of the non-redundant PKM, which does generally not constitute proper minimal coordinates for the entire workspace. Hence a redundantly actuated PKM (RA-PKM) controlled by a model-based controller in terms of minimal coordinates would exhibit the same limitations as the non-redundant PKM. One approach to tackle this problem is to switch between different minimal coordinates, i.e., different motion equations are used within the controller. In this contribution a computed torque and augmented PD control scheme in redundant coordinates is proposed, as an alternative to coordinate switching, and applied to the control of redundantly actuated PKM. That is, no minimal coordinates are selected. This novel formulation is numerically robust and does not suffer from input- or output-singularities. Even more the formulation is always valid except at configuration space singularities. For the redundancy resolution within the inverse dynamics the pseudoinverse of a rank deficient matrix is required, for which an explicit formulation is presented. For both controllers exponential trajectory tracking is shown. Experimental results are reported for a planar 2 DOF RA-PKM. © 2011 Elsevier B.V. All rights reserved.


Maier G.,University of Passau | Pisinger G.,Heilbronn University of Applied Sciences
Computational Geometry: Theory and Applications | Year: 2013

Optimal approximation of closed polygons differs from the case of open polygons in the sense that the location of a starting point must be determined in a suitable way. We present an algorithm which first computes a proper extremal arc as starting point and then approximates the input polygon with a minimum number of circular arcs and line segments. The resulting curve is called Cyclic Minimum Arc Path (CMAP). Our algorithm guarantees the CMAP staying inside a user-specified tolerance. In contrast to the existing approaches, we do not restrict the breakpoints of the arc spline to a predefined set of points but choose them automatically. This has considerable effects on the resulting number of segments. We can handle every type of tolerance zone representing the user-specified tolerance as long it is formed by piecewise restricted analytic curves. In case of polygonal tolerance zones the proposed algorithm takes O( n3) time for an original polygonal chain with n vertices. For generating a solution which has at most one additional segment we present an O( n2) algorithm. © 2012 Elsevier B.V.


Wiesner M.,Heilbronn University of Applied Sciences | Pfeifer D.,Heilbronn University of Applied Sciences
IHI'10 - Proceedings of the 1st ACM International Health Informatics Symposium | Year: 2010

In the future many people in industrialized countries will manage their personal health data electronically in centralized, reliable and trusted repositories - so-called personal health record systems (PHR). At this stage PHR systems still fail to satisfy the individual medical information needs of their users. Personalized recommendations could solve this problem. A first approach of integrating recommender system (RS) methodology into personal health records - termed health recommender system (HRS) - is presented. By exploitation of existing semantic networks like Wikipedia a health graph data structure is obtained. The data kept within such a graph represent health related concepts and are used to compute semantic distances among pairs of such concepts. A ranking procedure based on the health graph is outlined which enables a match between entries of a PHR system and health information artifacts. This way a PHR user will obtain individualized health information he might be interested in. © 2010 ACM.


Wittenberg C.,Heilbronn University of Applied Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Industrial automated production is a conservative domain. New information technologies find the way into this domain slowly or not at all. But in 2013 the fourth industrial revolution was announced: The so-called Industry 4. 0 implicates techniques like cloud-computing and self-organizing machines. The degree of technological complexity increases. Beside the technological innovation the use context and the tasks for the users will also be changed. In the design phase the engineers have to handle the increased complexity. In the operating phase the operators and also the service and maintenance technicians have to keep the production systems running. This paper discusses the results of the research about the effects of Industry 4. 0 on the different user groups and highlight selected user requirements. © Springer International Publishing Switzerland 2015.


Wiesner M.,Heilbronn University of Applied Sciences | Pfeifer D.,Heilbronn University of Applied Sciences
International Journal of Environmental Research and Public Health | Year: 2014

During the last decades huge amounts of data have been collected in clinical databases representing patients' health states (e.g., as laboratory results, treatment plans, medical reports). Hence, digital information available for patient-oriented decision making has increased drastically but is often scattered across different sites. As as solution, personal health record systems (PHRS) are meant to centralize an individual's health data and to allow access for the owner as well as for authorized health professionals. Yet, expert-oriented language, complex interrelations of medical facts and information overload in general pose major obstacles for patients to understand their own record and to draw adequate conclusions. In this context, recommender systems may supply patients with additional laymen-friendly information helping to better comprehend their health status as represented by their record. However, such systems must be adapted to cope with the specific requirements in the health domain in order to deliver highly relevant information for patients. They are referred to as health recommender systems (HRS). In this article we give an introduction to health recommender systems and explain why they are a useful enhancement to PHR solutions. Basic concepts and scenarios are discussed and a first implementation is presented. In addition, we outline an evaluation approach for such a system, which is supported by medical experts. The construction of a test collection for case-related recommendations is described. Finally, challenges and open issues are discussed. © 2014 by the authors; licensee MDPI, Basel, Switzerland.


Marsden N.,Heilbronn University of Applied Sciences
Conference on Human Factors in Computing Systems - Proceedings | Year: 2014

The work-in-progress outlined in this paper focuses on the role input fields in webforms play in the performance of gender. Based on the premise that doing gender in HCI should be studied both on the macro- and the micro-HCI level, and highlighting the perceived necessity of knowing someone's gender to interact with them, my research explores the micro aspect of input fields for titles: I have completed a search for user interface design patterns available to design input fields for titles and have sampled current practices of designing input fields in German websites. A second survey is ongoing. Afterwards I will develop alternative user interaction patterns for making choices regarding the selection of a title. The aim of these alternatives will be to trigger critical reflection on the danger of reifying the societal status quo via an input field.


Harke M.,Heilbronn University of Applied Sciences
Proceedings - 2014 International Conference on Electrical Machines, ICEM 2014 | Year: 2014

This paper deals with the analytical description of an interior permanent magnet synchronous motor running in six-step conduction mode. It assumes a non-sinusoidal back emf, but inductances vary sinusoidally with the rotor position. The proposed model renounces Park's transformation and delivers a set of equations which allow the numerical simulation of phase currents and torque in the abc reference frame. This model reveals the influence of the phase advance angle on the characteristics of current flow. By means of the simulation model two control strategies are shown - maximum torque per amp control and flux weakening. © 2014 IEEE.

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