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Earthquake engineering
(2017)

Vortrag

KLIMOPASS
(2017)

Vortrag

InBetween
(2017)

Einfluss der Oberfläche
(2017)

Efficient privacy-preserving configurationless service discovery supporting multi-link networks
(2017)

Data is the pollution problem of the information age, and protecting privacy is the environmental challenge — this quotation from Bruce Schneier laconically illustrates the importance of protecting privacy. Protecting privacy — as well as protecting our planet — is fundamental for humankind. Privacy is a basic human right, stated in the 12th article of the United Nations’ Universal Declaration of Human Rights. The necessity to protect human rights is unquestionable. Nothing ever threatened privacy on a scale comparable to today’s interconnected computers. Ranging from small sensors over smart phones and notebooks to large compute clusters, they collect, generate and evaluate vast amounts of data. Often, this data is distributed via the network, not only rendering it accessible to addressees, but also — if not properly secured — to malevolent parties. Like a toxic gas, this data billows through networks and suffocates privacy. This thesis takes on the challenge of protecting privacy in the area of configurationless service discovery. Configurationless service discovery is a basis for user-friendly applications. It brings great benefits, allowing the configurationless network setup for various kinds of applications; e.g. for communicating, sharing documents and collaborating, or using infrastructure devices like printers. However, while today’s various protocols provide some means of privacy protection, typical configurationless service discovery solutions do not even consider privacy. As configurationless service discovery solutions are ubiquitous and run on almost every smart device, their privacy problems affect almost everyone. The quotation aligns very well with configurationless service discovery. Typically, configurationless service discovery solutions realize configurationlessness by using cleartext multicast messages literally polluting the local network and suffocating privacy. Messages containing private cleartext data are sent to everyone, even if they are only relevant for a few users. The typical means for mitigating the network pollution problem caused by multicast per se, regardless of the privacy aspects, is confining multicast messages to a single network link or to the access network of a WiFi access point; institutions often even completely deactivate multicast. While this mitigates the privacy problem, it also strongly scales configurationless service discovery down, either confining it or rendering it completely unusable. In this thesis, we provide an efficient configurationless service discovery framework that protects the users’ privacy. It further reduces the network pollution by reducing the number of necessary multicast messages and offers a mode of operation that is completely independent of multicast. Introducing a multicast independent mode of operation, we also address the problem of the limited range in which services are discoverable. Our framework comprises components for device pairing, privacy-preserving service discovery, and multi-link scaling. These components are independent and — while usable in a completely separated way — are meant to be used as an integrated framework as they work seamlessly together. Based on our device pairing and privacy-preserving service discovery components, we published IETF Internet drafts specifying a privacy extension for DNS service discovery over multicast DNS, a wildly used protocol stack for configurationless service discovery. As our drafts have already been adopted by the dnssd working group, they are likely to become standards.

The goal of this paper pretends to show how a bed system with an embedded system with sensor is able to analyze a person’s movement, breathing and recognizing the positions that the subject is lying on the bed during the night without any additional physical contact. The measurements are performed with sensors placed between the mattress and the frame. An Intel Edison board was used as an endpoint that served as a communication node from the mesh network to external service. Two nodes and Intel Edison are attached to the bottom of the bed frame and they are connected to the sensors.

The exposure to the light has a great influence on human beings in their everyday life. Various lighting sources produce light that reaches the human eye and influences a rhythmic release of melatonin hormone, that is a sleep promoting factor.
Since the development of new technologies provides more control over illuminance, this work uses an IoT based lighting system to set up dim and bright scenarios. A small study has been performed on the influence of illuminance on sleep latency. The system consists of different light bulbs, sensors and a central bridge which are interconnected like a mesh network. Also, a mobile app has been developed, that allows to adjust the lighting in various rooms. With the help of a ferro-electret sensor, like applied in sleep monitoring systems, a subject’s sleep was monitored. The sensor is placed below the mattress and it collects data, which is stored and processed in a cloud or in other alternative locations.
The research was conducted on healthy young subjects after being previously exposed to the preconfigured illuminance for at least three hours before bedtime. The results indicate correlation between sleep onset latency and exposure to different illuminance before bedtime. In a dimmed environment, the subject fell asleep in average 28% faster compared to the brighter environment.

In several organizations, business workgroups autonomously implement information technology (IT) outside the purview of the IT department. Shadow IT, evolving as a type of workaround from nontransparent and unapproved end-user computing (EUC), is a term used to refer to this phenomenon, which challenges norms relative to IT controllability. This report describes shadow IT based on case studies of three companies and investigates its management. In 62% of cases, companies decided to reengineer detected instances or reallocate related subtasks to their IT department. Considerations of risks and transaction cost economics with regard to specificity, uncertainty, and scope explain these actions and the resulting coordination of IT responsibilities between the business workgroups and IT departments. This turns shadow IT into controlled business-managed IT activities and enhances EUC management. The results contribute to the governance of IT task responsibilities and provide a way to formalize the role of workarounds in business workgroups.

In this paper, multivariate polynomials in the Bernstein basis over a simplex (simplicial Bernstein representation) are considered. Two matrix methods for the computation of the polynomial coefficients with respect to the Bernstein basis, the so-called Bernstein coefficients, are presented. Also matrix methods for the calculation of the Bernstein coefficients over subsimplices generated by subdivision of the standard simplex are proposed and compared with the use of the de Casteljau algorithm. The evaluation of a multivariate polynomial in the power and in the Bernstein basis is considered as well. All the methods solely use matrix operations such as multiplication, transposition, and reshaping; some of them rely also on the bidiagonal factorization of the lower triangular Pascal matrix or the factorization of this matrix by a Toeplitz matrix. The latter one enables the use of the Fast Fourier Transform hereby reducing the amount of arithmetic operations.

Tests for speeding up the determination of the Bernstein enclosure of the range of a multivariate polynomial and a rational function over a box and a simplex are presented. In the polynomial case, this enclosure is the interval spanned by the minimum and the maximum of the Bernstein coefficients which are the coefficients of the polynomial with respect to the tensorial or simplicial Bernstein basis. The methods exploit monotonicity properties of the Bernstein coefficients of monomials as well as a recently developed matrix method for the computation of the Bernstein coefficients of a polynomial over a box.

Schreibberater an den Universitäten und Hochschulen und Verfasser von Ratgeberliteratur zum wissenschaftlichen Schreiben haben vermutlich zum überwiegenden Teil einen geistes- und kulturwissenschaftlichen Hintergrund. Die Fachkulturen, in denen sie das Handwerk des Zitierens erlernt haben, sind jedoch grundverschieden von jenen der nicht-textbasierten Wissenschaften: der Ingenieurfächer, der (nicht rein theoretischen) Naturwissenschaften, der Medizin und auch der empirischen Wirtschafts- und Sozialwissenschaften und der empirischen Psychologie. Die Unterschiede sind besonders augenfällig bei der Frage nach der Belegpflicht einer übernommenen Information, also bei der jeweiligen Entscheidung darüber, ob eine Quelle angegeben werden muss oder nicht.

To evaluate the quality of sleep, it is important to determine how much time was spent in each sleep stage during the night. The gold standard in this domain is an overnight polysomnography (PSG). But the recording of the necessary electrophysiological signals is extensive and complex and the environment of the sleep laboratory, which is unfamiliar to the patient, might lead to distorted results. In this paper, a sleep stage detection algorithm is proposed that uses only the heart rate signal, derived from electrocardiogram (ECG), as a discriminator. This would make it possible for sleep analysis to be performed at home, saving a lot of effort and money. From the heart rate, using the fast Fourier transformation (FFT), three parameters were calculated in order to distinguish between the different sleep stages. ECG data along with a hypnogram scored by professionals was used from Physionet database, making it easy to compare the results. With an agreement rate of 41.3%, this approach is a good foundation for future research.

Rethinking Compliance
(2017)

In the past Compliance Management has often failed, the Volkswagen emissions scandal just being one prominent example. Not everything has to be reinvented, and not everything that companies have done in the past regarding Compliance is wrong. But it is about time to think Compliance in new ways. What does “Compliance Management 2.0” really depend on? The following article aims at laying out the cornerstones for enduring effective Compliance which amongst others comprises sincerity and credibility and a moral foundation. Furthermore, the commitment and role model behavior of top managers and the training of line managers are crucial for the effectiveness of any Compliance Management System (CMS). Ultimately, for Compliance to function efficiently the efforts must be adequate for the respective company and realistic regarding the achievable goals.

Moderne politische Steuerungskonzeptionen zeichnen sich dadurch aus, dass sie zum einen die Mängel traditioneller planungszentrierter Konzepte vermeiden und zum anderen der gewachsenen Vielfalt an Kooperationsmöglichkeiten unterschiedlicher Akteurssysteme gerecht werden. Speziell für das Handlungsfeld der kommunalen Energiewende führt dies zu einer Governance-Konzeption, bei der Kommunen als systemische Steuerungsakteure fungieren. Hierbei moderieren und gestalten sie zusammen mit den relevanten Akteuren die verschiedenen Herausforderungen im Rahmen kommunaler Energiewendekonzepte.

This letter proposes two contributions to improve the performance of transmission with generalized multistream spatial modulation (SM). In particular, a modified suboptimal detection algorithm based on the Gaussian approximation method is proposed. The proposed modifications reduce the complexity of the Gaussian approximation method and improve the performance for high signal-to-noise ratios. Furthermore, this letter introduces signal constellations based on Hurwitz integers, i.e., a 4-D lattice. Simulation results demonstrate that these signal constellations are beneficial for generalized SM with two active antennas.

This work proposes a lossless data compression algorithm for short data blocks. The proposed compression scheme combines a modified move-to-front algorithm with Huffman coding. This algorithm is applicable in storage systems where the data compression is performed on block level with short block sizes, in particular, in non-volatile memories. For block sizes in the range of 1(Formula presented.)kB, it provides a compression gain comparable to the Lempel–Ziv–Welch algorithm. Moreover, encoder and decoder architectures are proposed that have low memory requirements and provide fast data encoding and decoding.

Ulrich Finsterwalder
(2017)

Sensorlose Positionsregelung eines hydraulischen Proportional-Wegeventils mittels Signalinjektion
(2017)

Es wird eine Methode zur sensorlosen Positionsbestimmung bei elektromagnetisch betätigten Aktoren vorgestellt. Dabei werden basierend auf einer Signalinjektion die positionsabhängigen Parameter bei der injizierten Frequenz bestimmt und daraus über ein geeignetes Modell die Position des Magnetankers ermittelt. Die Eignung des Verfahrens zur sensorlosen Positionsregelung wird an einem bidirektionalen Proportionalventil anhand praktischer Versuche demonstriert.

A real matrix is called totally nonnegative if all of its minors are nonnegative. In this paper, the minors are determined from which the maximum allowable entry perturbation of a totally nonnegative matrix can be found, such that the perturbed matrix remains totally nonnegative. Also, the total nonnegativity of the first and second subdirect sum of two totally nonnegative matrices is considered.

The aim of the paper is to present the simulation of the sweeping process based on a mathematical model that includes the drag force, the lift force, the sideway force, and the gravity. At the beginning, it is presented a short history of the street sweepers, some considerations about the sweeping process and the parameters of the sweeping process. Considering the developed model, in Matlab there is done some simulation for the trajectory of a spherical pebble. The obtained results are presented in graphical shape.

Several possibilities of tests under load on a chassis dynamometer are presented. Consumption measurements according standard driving cycles as the New European Drive Cycle (NEDC) and Worldwide harmonized light duty test procedure/cycle (WLTP/WLTC) make special attention to the observance of the regulations necessary. The rotational masses of inertia and the load depending on velocity have to match the required values. Load tests as well allow the determination of the maximum acceleration in the current gear and the slippage of the driven wheels.

The method of signal injection is investigated for position estimation of proportional solenoid valves. A simple observer is proposed to estimate a position-dependent parameter, i.e. the eddy current resistance, from which the position is calculated analytically. Therefore, the relationship of position and impedance in the case of sinusoidal excitation is accurately described by consideration of classical electrodynamics. The observer approach is compared with a standard identification method, and evaluated by practical experiments on an off-the-shelf proportional solenoid valve.

Sliding-mode observation with iterative parameter adaption for fast-switching solenoid valves
(2016)

Control of the armature motion of fast-switching solenoid valves is highly desired to reduce noise emission and wear of material. For feedback control, information of the current position and velocity of the armature are necessary. In mass production applications, however, position sensors are unavailable due to cost and fabrication reasons. Thus, position estimation by measuring merely electrical quantities is a key enabler for advanced control, and, hence, for efficient and robust operation of digital valves in advanced hydraulic applications. The work presented here addresses the problem of state estimation, i.e., position and velocity of the armature, by sole use of electrical measurements. The considered devices typically exhibit nonlinear and very fast dynamics, which makes observer design a challenging task. In view of the presence of parameter uncertainty and possible modeling inaccuracy, the robustness properties of sliding mode observation techniques are deployed here. The focus is on error convergence in the presence of several sources for modeling uncertainty and inaccuracy. Furthermore, the cyclic operation of switching solenoids is exploited to iteratively correct a critical parameter by taking into account the norm of the observation error of past switching cycles of the process. A thorough discussion on real-world experimental results highlights the usefulness of the proposed state observation approach.

In this paper, a gain-scheduled nonlinear control structure is proposed for a surface vessel, which takes advantage of extended linearisation techniques. Thereby, an accurate tracking of desired trajectories can be guaranteed that contributes to a safe and reliable water transport. The PI state feedback control is extended by a feedforward control based on an inverse system model. To achieve an accurate trajectory tracking, however, an observer-based disturbance compensation is necessary: external disturbances by cross currents or wind forces in lateral direction and wave-induced measurement disturbances are estimated by a nonlinear observer and used for a compensation. The efficiency and the achieved tracking performance are shown by simulation results using a validated model of the ship Korona at the HTWG Konstanz, Germany. Here, both tracking behaviour and rejection of disturbance forces in lateral direction are considered.

This work investigates data compression algorithms for applications in non-volatile flash memories. The main goal of the data compression is to minimize the amount of user data such that the redundancy of the error correction coding can be increased and the reliability of the error correction can be improved. A compression algorithm is proposed that combines a modified move-to-front algorithm with Huffman coding. The proposed data compression algorithm has low complexity, but provides a compression gain comparable to the Lempel-Ziv-Welch algorithm.

In this paper totally nonnegative (positive) matrices are considered which are matrices having all their minors nonnegative (positve); the almost totally positive matrices form a class between the totally nonnegative matrices and the totally positive ones. An efficient determinantal test based on the Cauchon algorithm for checking a given matrix for falling in one of these three classes of matrices is applied to matrices which are related to roots of polynomials and poles of rational functions, specifically the Hankel matrix associated with the Laurent series at infinity of a rational function and matrices of Hurwitz type associated with polynomials. In both cases it is concluded from properties of one or two finite sections of the infinite matrix that the infinite matrix itself has these or related properties. Then the results are applied to derive a sufficient condition for the Hurwitz stability of an interval family of polynomials. Finally, interval problems for a subclass of the rational functions, viz. R-functions, are investigated. These problems include invariance of exclusively positive poles and exclusively negative roots in the presence of variation of the coefficients of the polynomials within given intervals.

A real matrix is called totally nonnegative if all of its minors are nonnegative. In this paper the extended Perron complement of a principal submatrix in a matrix A is investigated. In extension of known results it is shown that if A is irreducible and totally nonnegative and the principal submatrix consists of some specified consecutive rows then the extended Perron complement is totally nonnegative. Also inequalities between minors of the extended Perron complement and the Schur complement are presented.

We consider classes of n-by-n sign regular matrices, i.e., of matrices with the property that all their minors of fixed order k have one specified sign or are allowed also to vanish, k = 1, ... ,n. If the sign is nonpositive for all k, such a matrix is called totally nonpositive. The application of the Cauchon algorithm to nonsingular totally nonpositive matrices is investigated and a new determinantal test for these matrices is derived. Also matrix intervals with respect to the checkerboard partial ordering are considered. This order is obtained from the usual entry-wise ordering on the set of the n-by-n matrices by reversing the inequality sign for each entry in a checkerboard fashion. For some classes of sign regular matrices it is shown that if the two bound matrices of such a matrix interval are both in the same class then all matrices lying between these two bound matrices are in the same class, too.

Energiequelle Seewasser
(2015)