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Perceptual integration of kinematic components in the recognition of emotional facial expressions
(2018)
According to a long-standing hypothesis in motor control, complex body motion is organized in terms of movement primitives, reducing massively the dimensionality of the underlying control problems. For body movements, this low dimensional organization has been convincingly demonstrated by the learning of low-dimensional representations from kinematic and EMG data. In contrast, the effective dimensionality of dynamic facial expressions is unknown, and dominant analysis approaches have been based on heuristically defined facial ‘‘action units,’’ which reflect contributions of individual face muscles. We determined the effective dimensionality of dynamic facial expressions by learning of a low dimensional model from 11 facial expressions. We found an amazingly low dimensionality with only two movement primitives being sufficient to simulate these dynamic expressions with high accuracy. This low dimensionality is confirmed statistically, by Bayesian model comparison of models with different numbers of primitives, and by a psychophysical experiment that demonstrates that expressions, simulated with only two primitives, are indistinguishable from natural ones.
In addition, we find statistically optimal integration of the emotion information specified by these primitives in visual perception. Taken together, our results indicate that facial expressions might be controlled by a very small number of independent control units, permitting very low dimensional parametrization of the associated facial expression.
A case study with four German fashion retail brands was conducted in order to measure the performance of their Omnichannel services. In detail, their Click & Collect service was analyzed. Click & Collect is one of the first introduced Omnichannel services in fashion retailing. Omnichannel services integrate different sales and communication channels providing a seamless customer journey experience. Offline, online, and mobile app customer experiences should provide a seamless customer experience. Omnichannel performance of the four retailers Decathlon, Hunkemöller, Massimo Dutti and Galeria Kaufhof was measured via mystery shopping. A seamless customer journey experience is not yet a standard in German fashion retailing. The four companies differ in many process details. The biggest market potential and the recommendation for further research emerges in deficits of the offline store Omnichannel customer experience. Here, all four case companies have room to improve. Best overall results regarding the integration of offline, online and mobile shops were found with Hunkemöller, followed by Decathlon, Massimo Dutti, and Galeria Kaufhof.
Database management systems (DBMS) are critical performance components in large scale applications under modern update intensive workloads. Additional access paths accelerate look-up performance in DBMS for frequently queried attributes, but the required maintenance slows down update performance. The ubiquitous B+ tree is a commonly used key-indexed access path that is able to support many required functionalities with logarithmic access time to requested records. Modern processing and storage technologies and their characteristics require reconsideration of matured indexing approaches for today's workloads. Partitioned B-trees (PBT) leverage characteristics of modern hardware technologies and complex memory hierarchies as well as high update rates and changes in workloads by maintaining partitions within one single B+-Tree. This paper includes an experimental evaluation of PBTs optimized write pattern and performance improvements. With PBT transactional throughput under TPC-C increases 30%; PBT results in beneficial sequential write patterns even in presence of updates and maintenance operations.
Characteristics of modern computing and storage technologies fundamentally differ from traditional hardware. There is a need to optimally leverage their performance, endurance and energy consumption characteristics. Therefore, existing architectures and algorithms in modern high performance database management systems have to be redesigned and advanced. Multi Version Concurrency Control (MVCC) approaches in data-base management systems maintain multiple physically independent tuple versions. Snapshot isolation approaches enable high parallelism and concurrency in workloads with almost serializable consistency level. Modern hardware technologies benefit from multi-version approaches. Indexing multi-version data on modern hardware is still an open research area. In this paper, we provide a survey of popular multi-version indexing approaches and an extended scope of high performance single-version approaches. An optimal multi-version index structure brings look-up efficiency of tuple versions, which are visible to transactions, and effort on index maintenance in balance for different workloads on modern hardware technologies.
Dieses Buch beschreibt detailliert die Voraussetzungen und den Prozessablauf von Business Cases. Diese stellen in der Praxis das wichtigste Instrument dar, um unternehmerische Entscheidungen auf ihre Vorteilhaftigkeit zu analysieren. Um einen adäquaten Business Case zu erstellen, reicht allerdings die reine Beherrschung der relevanten Methoden der Investitionsrechnung nicht aus. Andreas Taschner gibt hilfreiche Anleitungen und Tipps zur Methodenwahl und Ergebnisdarstellung und erläutert weitergehende Fragen, wie die Berücksichtigung von Unsicherheit oder die Einbeziehung nicht-monetärer Faktoren. Die Orientierung am idealtypischen Prozess hilft beim Erarbeiten eigener Business Cases und liefert einen Leitfaden für die ersten selbstständigen Arbeiten. Anwendungsbezogene Fragen und Antworten vertiefen die Thematik. „Business Cases“ wendet sich an Unternehmenspraktiker in den Bereichen Investition, Controlling, Planung und Unternehmensführung. Studierende der Wirtschaftswissenschaften an Fachhochschulen und Universitäten, insbesondere mit den Schwerpunkten Controlling und Unternehmensführung, profitieren von der kompakten Wissensvermittlung.
Die Erfindung betrifft eine Vorrichtung (100) und ein Verfahren zum elektrischen Verbinden und Trennen zweier elektrischer Potentiale (1, 2). Des Weiteren betrifft die Erfindung eine Verwendung der Vorrichtung (100). Dabei umfasst die Vorrichtung (100): – ein erstes Modul, welches einen ersten und einen zweiten Transistor (10a, 10b) umfasst, wobei der erste Transistor (10a) antiseriell zu dem zweiten Transistor (10b) geschaltet ist; und – ein zweites Modul, welches einen dritten und einen vierten Transistor (10c, 10d) umfasst, wobei der dritte Transistor (10c) antiseriell zu dem vierten Transistor (10d) geschaltet ist; wobei das erste Modul und das zweite Modul parallel geschaltet sind.
Using measurement and simulation for understanding distributed development processes in the Cloud
(2017)
Organizations increasingly develop software in a distributed manner. The Cloud provides an environment to create and maintain software-based products and services. Currently, it is widely unknown which software processes are suited for Cloud-based development and what their effects in specific contexts are. This paper presents a process simulation to study distributed development in the Cloud. We contribute a simulation model, which helps analyzing different project parameters and their impact on projects carried out in the Cloud. The simulator helps reproducing activities, developers, issues and events in the project, and it generates statistics, e.g., on throughput, total time, and lead and cycle time. The aim of this simulation model is thus to analyze the tradeoffs regarding throughput, total time, project size, and team size. Furthermore, the modified simulation model aims to help project managers select the most suitable planning alternative. Based on observed projects in Finland and Spain, we simulated a distributed project using artificial and real data. Particularly, we studied the variables project size, team size, throughput, and total project duration. A comparison of the real project data with the results obtained from the simulation shows the simulation producing results close to the real data, and we could successfully replicate a distributed software project. By improving the understanding of distributed development processes, our simulation model thus supports project managers in their decision-making.
The business landscape is changing radically because of software. Companies in all industry sectors are continously finding new flexibilities in this programmable world. They are able to deliver new functionalities even after the product is already in the customer's hands. But success is far from guaranteed if they cannot validate their assumptions about what their customers actually need. A competitor with better knowledge of customer needs can disrupt the market in an instant.
This book introduces continuous experimentation, an approach to continuously and systematically test assumptions about the company's product or service strategy and verify customers' needs through experiments. By observing how customers actually use the product or early versions of it, companies can make better development decisions and avoid potentially expensive and wasteful activities. The book explains the cycle of continuous experimentation, demonstrates its use through industry cases, provides advice on how to conduct experiments with recipes, tools, and models, and lists some common pitfalls to avoid. Use it to get started with continuous experimentation and make better product and service development decisions that are in-line with your customers' needs.
Due to rapidly changing technologies and business contexts, many products and services are developed under high uncertainties. It is often impossible to predict customer behaviors and outcomes upfront. Therefore, product and service developers must continuously find out what customers want, requiring a more experimental mode of management and appropriate support for continuously conducting experiments. We have analytically derived an initial model for continuous experimentation from prior work and matched it against empirical case study findings from two startup companies. We examined the preconditions for setting up an experimentation system for continuous customer experiments. The resulting RIGHT model for Continuous Experimentation (Rapid Iterative value creation Gained through High-frequency Testing) illustrates the building blocks required for such a system and the necessary infrastructure. The major findings are that a suitable experimentation system requires the ability to design, manage, and conduct experiments, create so-called minimum viable products or features, link experiment results with a product roadmap, and manage a flexible business strategy. The main challenges are proper, rapid design of experiments, advanced instrumentation of software to collect, analyse, and store relevant data, and integration of experiment results in the product development cycle, software development process, and business strategy. This summary refers to the article The RIGHT Model for Continuous Experimentation, published in the Journal of Systems and Software [Fa17].
First International Workshop on Hybrid dEveLopmENt Approaches in Software Systems Development
(2017)
A software process is the game plan to organize project teams and run projects. Yet, it still is a challenge to select the appropriate development approach for the respective context. A multitude of development approaches compete for the users’ favor, but there is no silver bullet serving all possible setups. Moreover, recent research as well as experience from practice shows companies utilizing different development approaches to assemble the bestfitting approach for the respective company: a more traditional process provides the basic framework to serve the organization, while project teams embody this framework with more agile (and/or lean) practices to keep their flexibility. The first HELENA workshop aims to bring together the community to discuss recent findings and to steer future work.
The ability to develop and deploy high-quality software at a high speed gets increasing relevance for the comptetitiveness of car manufacturers. Agile practices have shown benefits such as faster time to market in several application domains. Therefore, it seems to be promising to carefully adopt agile practices also in the automotive domain. This article presents findings from an interview-based qualitative survey. It aims at understanding perceived forces that support agile adoption. Particularly, it focuses on embedded software development for electronic control units in the automotive domain.
Software and system development faces numerous challenges of rapidly changing markets. To address such challenges, companies and projects design and adopt specific development approaches by combining well-structured comprehensive methods and flexible agile practices. Yet, the number of methods and practices is large, and available studies argue that the actual process composition is carried out in a fairly ad-hoc manner. The present paper reports on a survey on hybrid software development approaches. We study which approaches are used in practice, how different approaches are combined, and what contextual factors influence the use and combination of hybrid software development approaches. Our results from 69 study participants show a variety of development approaches used and combined in practice. We show that most combinations follow a pattern in which a traditional process model serves as framework in which several fine-grained (agile) practices are plugged in. We further show that hybrid software development approaches are independent from the company size and external triggers. We conclude that such approaches are the results of a natural process evolution, which is mainly driven by experience, learning, and pragmatism.
The digital transformation of the automotive industry has a significant impact on how development processes need to be organized in future. Dynamic market and technological environments require capabilities to react on changes and to learn fast. Agile methods are a promising approach to address these needs but they are not tailored to the specific characteristics of the automotive domain like product line development. Although, there have been efforts to apply agile methods in the automotive domain for many years, significant and widespread adoptions have not yet taken place. The goal of this literature review is to gain an overview and a better understanding of agile methods for embedded software development in the automotive domain, especially with respect to product line development. A mapping study was conducted to analyze the relation between agile software development, embedded software development in the automotive domain and software product line development. Three research questions were defined and 68 papers were evaluated. The study shows that agile and product line development approaches tailored for the automotive domain are not yet fully explored in the literature. Especially, literature on the combination of agile and product line development is rare. Most of the examined combinations are customizations of generic approaches or approaches stemming from other domains. Although, only few approaches for combining agile and software product line development in the automotive domain were found, these findings were valuable for identifying research gaps and provide insights into how existing approaches can be combined, extended and tailored to suit the characteristics of the automotive domain.
Seit über 50 Jahren dominiert die neoklassische Kapitalmarkttheorie unser Verständnis für die Abläufe an Finanzmärkten. Sie hat eine Vielzahl von Theorien und Konzepten (z.B. Portfoliotheorie, Capital Asset Pricing Model oder Value-at-Risk) hervorgebracht und basiert auf der Annahme eines streng rationalen Homo Oeconomicus.
Das vorliegende Buch möchte Praktikern die Türe öffnen zu einer neu entstehenden, verhaltenswissenschaftlichen Sicht auf die Finanzmärkte, in der ein realitätsnäherer Homo Oeconomicus Humanus an den Märkten agiert. Er setzt bei der Entscheidungsfindung begrenzt rationale Heuristiken ein und lässt sich von emotionalen Einflüssen lenken.
Die Autoren schlagen zunächst den Bogen von der neoklassischen Sicht der Finanzmärkte zur Behavioral Finance. Anschließend werden spekulative Blasen, von der Tulpenmanie bis zur Subprime Hypothekenblase, als Anzeichen für begrenzte Rationalität an Finanzmärkten ausführlich vorgestellt. Danach stehen die Heuristiken bei Anlageentscheidungen an Wertpapiermärkten im Vordergrund. Die dadurch ausgelösten Verzerrungen werden ntsprechend ihrer Risiko-/Renditeschädlichkeit im Rahmen des RRS-Index® eingeordnet. Abschließend werden Beispiele für die Anwendung der Behavioral-Finance-Erkenntnisse im Wealth Management und Corporate Governance diskutiert und es wird ein Blick auf aktuelle Entwicklungen der Neuro-Finance und Emotional Finance geworfen.
In dieser Auflage neu hinzugekommen ist Financial Nudging, eine besonders vielversprechende Anwendung von Behavioral Finance-Erkenntnissen.
Afrika ist aufgrund überdurchschnittlicher Wirtschaftswachstumsraten und als die weltweit letzten unbearbeiteten Märkte seit einigen Jahren ein populäres Thema der Wirtschaft. Deutsche Unternehmen sind allerdings mit ihrem Engagement auf den afrikanischen Märkten sehr zurückhaltend. So schwankt der Anteil der deutschen Exporte nach Afrika an den deutschen Gesamtexporten seit zehn Jahren um die zwei Prozent; betrachtet man nur Subsahara‐Afrika, so waren es sogar nur 0,5 % in 2014 (Allafi und Koch 2015, S. 3). Bezüglich der Direktinvestitionen (nur Beteiligungskapital, ohne Direktinvestitionskredite) spielt Afrika eine noch geringere Rolle mit nur 1,5 % aller deutschen Investitionen in 2014, wobei hiervon so gut wie alle nach Nordafrika und Südafrika geflossen sind (Deutsche Bundesbank 2015, S. 12 f.). Neben den Standardgründen wie beispielsweise politischen Risiken, schlechter Infrastruktur, schwacher institutioneller Rahmenbedingungen und Governance‐Problemen (vgl. zum Beispiel World Bank 2016a), ist ein gängiges Markteintrittsproblem die fehlende Verfügbarkeit von lokalen Partnern in den Bereichen Vertrieb, Logistik und teilweise auch Produktion (vgl. zum Beispiel Carlowitz und Röndigs 2016). Aktuell ist ein Markteintritt in Afrika ohne lokalen Partner aufgrund der völlig anderen und schwierigen Rahmenbedingungen fast unmöglich.
Incubators in multinational corporations : development of a corporate incubator operator model
(2017)
This paper analyzes the components of a corporate incubator operator model in multinational companies. Thereby, three relevant phases were identified: pre incubation, incubation, and exit. Each phase contains different criteria that represent critical success factors for a corporate incubator, which are based on theoretical findings and lessons learned from practice. During the pre-incubation phase companies should define their need for a corporate incubator, the origin of ideas and the selection criteria for incubator tenants. The actual phase of incubation refers to the incubator program, which should be flexible with respect to each tenant. Furthermore, resource allocation plays an important role during the incubator program. Exit options after a successful incubation differ according to internal ideas and external start-ups, as well as the objective of the incubator. The research is based on a comprehensive screening of existing incubator literature and a qualitative content analysis of statements from eight experts of international corporate incubators.
Gallium nitride high electron mobility transistors (GaN-HEMTs) have low capacitances and can achieve low switching losses in applications where hard turn-on is required. Low switching losses imply a fast switching; consequently, fast voltage and current transients occur. However, these transients can be limited by package and layout parasitics even for highly optimized systems. Furthermore, a fast switching requires a fast charging of the input capacitance, hence a high gate current.
In this paper, the switching speed limitations of GaN-HEMTs due to the common source inductance and the gate driver supply voltage are discussed. The turn-on behavior of a GaN-HEMT is simulated and the impact of the parasitics and the gate driver supply voltage on the switching losses is described in detail. Furthermore, measurements are performed with an optimized layout for a drain-source voltage of 500 V and a drain-source current up to 60 A.
A device including a first and second monitoring unit, the first monitoring unit detecting a first voltage potential and the second monitoring unit detecting a second voltage potential, the monitoring units comparing the first voltage potential and the second voltage potential to the value of the supply voltage and activate a control unit as a function of the comparisons, the control unit determining a switching point in time of a second power transistor, and an arrangement being present which generates current when the second power transistor is being switched on, the current changing the first voltage potential, and the control unit activates a first power transistor when the first voltage potential has the same value as the supply voltage, so that the first power transistor is de-energized.
Modern power semiconductor devices have low capacitances and can therefore achieve very fast switching transients under hard-switching conditions. However, these transients are often limited by parasitic elements, especially by the source inductance and the parasitic capacitances of the power semiconductor. These limitations cannot be compensated by conventional gate drivers. To overcome this, a novel gate driver approach for power semiconductors was developed. It uses a transformer which accelerates the switching by transferring energy from the source path to the gate path.
Experimental results of the novel gate driver approach show a turn-on energy reduction of 78% (from 80 μJ down to 17 μJ) with a drain-source voltage of 500V and a drain current of 60 A. Furthermore, the efficiency improvement is demonstrated for a hard-switching boost converter. For a switching frequency of 750 kHz with an input voltage of 230V and an output voltage of 400V, it was possible to extend the output power range by 35%(from 2.3kW to 3.1 kW), due to the reduction of the turn-on losses, therefore lowering the junction temperature of the GaN-HEMT.
Um sich im Kommunikationswettbewerb zu profilieren und Streuverluste zu minimieren, bedienen sich Unternehmen vermehrt den sogenannten "nicht klassischen" Kommunikationsinstrumenten. Sponsoring stellt dabei einen erfolgsversprechenden Ansatz dar, da Sponsoring in einem attraktiven, emotional- aufgeladenen und nicht -kommerziellen Umfeld stattfindet. Aufgrund der zunehmenden Reizüberflutung der Konsumenten erscheint die Erreichung gesteckter Sponsoringziele durch bloße Sichtbarkeit jedoch nicht mehr zufriedenstellend realisierbar. Der vorliegende Beitrag behandelt das Thema Aktuelle Trends im Sponsoring im Sport. Die Analyse der aktuellen Entwicklungen zeigt, dass sich die Wirkungsvoraussetzungen des Sponsoring im Zeitverlauf verändert haben. Es bedarf neuer und innovativer Aktivierungsmaßmahmen, um die Reizüberflutung der Konsumenten zu überwinden und die Potentiale des Sponsorings zu nutzen. Die Darstellung praktischer Beispiele aus dem Sportmarketing zeigt, dass die handelnden Akteure die neuen Herausforderungen des Sponsorings erkannt haben. Es werden die aktuellen Entwicklungen hinsichtlich Digitalisierung, Internationalisierung, Professionalisierung und unkonventionaller Aktivierung aufgezeigt.
Within the scope of the present cumulative doctoral thesis six scientific papers were published which illustrates that modern reaction model-free (=isoconversional) kinetic analysis (ICKA) methods represents a universal and effective tool for the controlled processing of thermosetting materials. In order to demonstrate the universal applicability of ICKA methods, the thermal cure of different thermosetting materials having a very broad range of chemical composition (melamine-formaldehyde resins, epoxy resins, polyester-epoxy resins, and acrylate/epoxy resins) were analyzed and mathematically modelled. Some of the materials were based on renewable resources (an epoxy resin was made from hempseed oil; linseed oil was modified into an acrylate/epoxy resin). With the aid of ICKA methods not only single-step but also complex multi-step reactions were modelled precisely. The analyzed thermosetting materials were combined with wood, wood-based products, paper, and plant fibers which are processed to various final products. Some of the thermosetting materials were applied as coating (in form of impregnated décor papers or powder and wet coatings respectively) on wood substrates and the epoxy resin from hempseed oil was mixed with plant fibers and processed into bio-based composites for lightweight applications. From the final products mechanical, thermal, and surface properties were determined. The activation energy as function of cure conversion derived from ICKA methods was utilized to predict accurately the thermal curing over the course of time for arbitrary cure conditions. Furthermore the cure models were used to establish correlations between the cross-linking during processing into products and the properties of the final products. Therewith it was possible to derive the process time and temperature that guarantee optimal cross-linking as well as optimal product properties
The presented wide-Vin step-down converter introduces a parallel-resonant converter (PRC), comprising an integrated 5-bit capacitor array and a 300 nH resonant coil, placed in parallel to a conventional buck converter. Unlike conventional resonant concepts, the implemented soft-switching control eliminates input voltage dependent losses over a wide operating range. This ensures high efficiency across a wide range of Vin= 12-48V, 100-500mA load and 5V output at up to 15MHz switching frequency. The peak efficiency of the converter is 76.3 %. Thanks to the low output current ripple, the output capacitor can be as small as 50 nF, while the inductor tolerates a larger ESR, resulting in small component size. The proposed PRC architecture is also suitable for future power electronics applications using fast-switching GaN devices.
Instead of waiting for and constantly adapting to details of political interventions, utilities need to focus on their environment from a holistic perspective. The unique position of the company - be it a local utility, a bigger player, or an international utility specializing in specitic segments - has to be the basis of goals and strategies. But without consistent translation of these goals and strategies into processes, structures, and company culture, a strategy remains pure theory. Companies need to engage in a continuing learning process. This means being willing to pass on strategies, to slow down or speed up, to work from a different angle etc.
Saving energy and road safety became important in the last decades, hence several driving assistant systems were developed that help to improve the driving behaviour. However, these driving systems cover the area of either energy-efficiency or safety. Furthermore, they do not consider the reaction of the driver to a shown recommendation and the driver stress level. In this paper, the decision process of showing a recommendation to the driver in an energy-efficient and safety relevant driving system is presented. The decision process considers the driver's reaction to a shown recommendation and the driver stress in order to increase the user acceptance and the road safety. The results of the evaluation showed that the driving system was able to show recommendations when needed, while suppressing recommendations when the driver ignored a recommendation repeatedly or when the driver was in stress.
More and more power electronics applications utilize GaN transistors as they enable higher switching frequencies in comparison to conventional Si devices. Faster switching shrinks down the size of passives and enables compact solutions in applications like renewable energy, electrical cars and home appliances. GaN transistors benefit from ~10× smaller gate charge QG and gate drive voltages in the range of typically 5V vs. ~15V for Si.
Modern power transistors are able to switch at very high transition speed, which can cause EMC violations and overshoot. This is addressed by a gate driver with variable gate current, which is able to control the transition speed. The key idea is that the gate driver can influence the di/dt and dv/dt transition separately and optimize whichever transition promises the highest improvement while keeping switching losses low. To account for changes in the load current, supply voltage, etc., a control loop is required in the driver to ensure optimized switching. In this paper, an efficient control scheme for an automotive gate driver with variable output current capability is presented. The effectiveness of the control loop is demonstrated for a MOSFET bridge consisting of OptiMOS-T2™devices with a total gate charge of 39nC. This bridge setup shows dv/dt transitions between 50 to 1000ns, depending on driving current. The driver is able to switch between gate current levels of 1 to 500mA in 10/15ns (rising/falling transition). With the implemented control loop the driver is measured to significantly reduce the ringing and thereby reduce device stress and electromagnetic emissions while keeping switching losses 52% lower than with a constant current driver.
A concept for a slope shaping gate driver IC is proposed, used to establish control over the slew rates of current and voltage during the turn-on and turn off switching transients.
It combines the high speed and linearity of a fully-integrated closed-loop analog gate driver, which is able to perform real-time regulation, with the advantages of digital control, like flexibility and parameter independency, operating in a predictive cycle-bycycle regulation. In this work, the analog gate drive integrated circuit is partitioned into functional blocks and modeled in the small-signal domain, which also includes the non-linearity of parameters. An analytical stability analysis has been performed in order to ensure full functionality of the system controlling a modern generation IGBT and a superjunction MOSFET. Major parameters of influence, such as gate resistor and summing node capacitance, are investigated to achieve stable control. The large-signal behavior, investigated by simulations of a transistor level design, verifies the correct operation of the circuit. Hence, the gate driver can be designed for robust operation.
In a digitally controlled slope shaping system, reliable detection of both voltage and current slope is required to enable a closed-loop control for various power switches independent of system parameters. In most state-of-the-art works, this is realized by monitoring the absolute voltage and current values. Better accuracy at lower DC power loss is achieved by sensing techniques for a reliable passive detection, which is achieved through avoiding DC paths from the high voltage network into the sensing network. Using a high-speed analog-to-digital converter, the whole waveform of the transient derivative can be stored digitally and prepared for a predictive cycle-by-cycle regulation, without requiring high-precision digital differentiation algorithms. To gain an accurate representation of the voltage and current derivative waveforms, system parasitics are investigated and classified in three sections: (1) component parasitics, which are identified by s-parameter measurements and extraction of equivalent circuit models, (2) PCB design issues related to the sensing circuit, and (3) interconnections between adjacent boards.
The contribution of this paper is an optimized sensing network on the basis of the experimental study supporting fast transition slopes up to 100 V/ns and 1 A/ns and beyond, making the sensing technique attractive for slope shaping of fast switching devices like modern generation IGBTs, CoolMOSTM and SiC mosfets. Measurements of the optimized dv/dt and di/dt setups are demonstrated for a hard switched IGBT power stage.
Introducing continuous experimentation in large software-intensive product and service organisations
(2017)
Software development in highly dynamic environments imposes high risks to development organizations. One such risk is that the developed software may be of only little or no value to customers, wasting the invested development efforts.Continuous experiment ation, as an experiment-driven development approach, may reduce such development risks by iteratively testing product and service assumptions that are critical to the success of the software. Although several experiment-driven development approaches are available, there is little guidance available on how to introduce continuous experimentation into an organization. This article presents a multiple-case study that aims at better understanding the process of introducing continuous experimentation into an organization with an already established development process. The results from the study show that companies are open to adopting such an approach and learning throughout the introduction process. Several benefits were obtained, such as reduced development efforts, deeper customer insights, and better support for development decisions. Challenges included complex stakeholder structures, difficulties in defining success criteria, and building experimen- tation skills. Our findings indicate that organizational factors may limit the benefits of experimentation. Moreover, introducing continuous experimentation requires fundamental changes in how companies operate, and a systematic introduction process can increase the chances of a successful start.
Empirical software engineering experts on the use of students and professionals in experiments
(2018)
Using students as participants remains a valid simplification of reality needed in laboratory contexts. It is an effective way to advance software engineering theories and technologies but, like any other aspect of study settings, should be carefully considered during the design, execution, interpretation, and reporting of an experiment. The key is to understand which developer population portion is being represented by the participants in an experiment. Thus, a proposal for describing experimental participants is put forward.
Medical applications are becoming increasingly important in the current development of health care and therefore a crucial part of the medical industry. The work focuses on the analysis of requirements and the challenges arisen from designing mobile medical applications in relation to the user interface. The paper describes the current status in the development of mobile medical apps and illustrates the development of e-health market. The author will explain the requirements and will illustrate the hurdles and problems. He refers to the German market which is similar to the European and compares that with the market in the USA.
To assess the quality of a person’s sleep, it is essential to examine the sleep behaviour by identifying the several sleep stages, their durations and sleep cycles. The established and gold standard procedure for sleep stage scoring is overnight polysomnography (PSG) with the Rechtschaffen and Kales (R-K) method. Unfortunately, the conduct of PSG is time-consuming and unfamiliar for the subjects and might have an impact of the recorded data. To avoid the disadvantages with PSG, it is important to make further investigations in low-cost home diagnostic systems. For this intention it is necessary to find suitable bio vital parameters for classifying sleep stages without any physical impairments at the same time. Due to the promising results in several publications we want to analyse existing methods for sleep stage classification based on the parameters body movement,
heartbeat and respiration. Our aim was to find different behaviour patterns in the several sleep stages. Therefore, the average values of 15 whole-night PSG recordings -obtained from the ‘DREAMS
Subjects Database’- where analysed in the light of heartbeat, body movement and respiration with 10 different methods.
Sleep quality and in general, behavior in bed can be detected using a sleep state analysis. These results can help a subject to regulate sleep and recognize different sleeping disorders. In this work, a sensor grid for pressure and movement detection supporting sleep phase analysis is proposed. In comparison to the leading standard measuring system, which is Polysomnography (PSG), the system proposed in this project is a non invasive sleep monitoring device. For continuous analysis or home use, the PSG or wearable actigraphy devices tends to be uncomfortable. Besides this fact, they are also very expensive. The system represented in this work classifies respiration and body movement with only one type of sensor and also in a non invasive way. The sensor used is a pressure sensor. This sensor is low cost and can be used for commercial proposes. The system was tested by carrying out an experiment that recorded the sleep process of a subject. These recordings showed the potential for classification of breathing rate and body movements. Although previous researches show the use of pressure sensors in recognizing posture and breathing, they have been mostly used by positioning the sensors between the mattress and bedsheet. This project however, shows an innovative way to position the sensors under the mattress.
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.
Zukünftige Montagearbeitsplätze müssen veränderten Herausforderungen, wie z. B. der zunehmenden Anzahl von Mensch Roboter-Kollaborationen, gerecht werden. Die Virtual Reality (VR)-Technik bietet im Rahmen der Arbeitsplatzgestaltung neue Möglichkeiten, diesen veränderten Planungsherausforderungen gerecht zu werden. Die Ausarbeitung stellt eine Methode zur Bewertung des sinnvollen Einsatzes der VR-Technik für einen spezifischen Arbeitsplatz vor. Außerdem wird aufgezeigt, wie die VR-Technik in den Prozess der Arbeitsplatzgestaltung integriert werden kann.
46 Prozent der Arbeitsplätze in der Automobilindustrie sind bis 2030 durch Automatisierung und Digitalisierung bedroht – die Tätigkeiten werden dann nicht mehr von Menschen, sondern von intelligenten Robotern und Systemen erledigt. Das ist das zentrale Ergebnis unserer Studie „Digitale Transformation – Der Einfluss der Digitalisierung auf die Workforce in der Automobilindustrie“, die wir gemeinsam mit dem Herman Hollerith Lehr- und Forschungszentrum an der Hochschule Reutlingen erstellt haben.
LDMOS transistors in integrated power technologies are often subject to thermo-mechanical stress, which degrades the on-chip metallization and eventually leads to a short. This paper investigates small sense lines embedded in the LDMOS metallization. It will be shown that their resistance depends strongly on the stress cycle number. Thus, they can be used as aging sensors and predict impending failures. Different test structures have been investigated to identify promising layout configurations. Such sensors are key components for resilient systems that adaptively reduce stress to allow aggressive LDMOS scaling without increasing the risk of failure.
A gate driver approach is presented for the reduction of turn-on losses in hard switching applications. A significant turn-on loss reduction of up to 55% has been observed for SiCMOSFETs. The gate driver approach uses a transformer which couples energy from the power path back into the gate path during switching events, providing increased gate driver current and thereby faster switching speed.
The gate driver approach was tested on a boost converter running at a switching frequency up to 300 kHz. With an input voltage of 300V and an output voltage of 600V, it was possible to reduce the converter losses by 8% at full load. Moreover, the output power range could be extended by 23% (from 2.75kW to 3.4 kW) due to the reduction of the turn-on losses.
Die weiterhin hohen Schulden in einigen Staaten der Europäischen Wirtschafts- und Währungsunion lassen nach wie vor staatliche Insolvenzen befürchten. Um die entstandenen Probleme zu bewältigen, aber auch damit eine solche Situation erst gar nicht eintritt, hält der Autor eine staatliche Insovenzordnung – mit Bail-out durch die anderen Mitgliedstaaten nur in Notfällen – für erforderlich. Er schlägt einen staatlichen Abwicklungsmechanismus für überschuldete Euro-Länder vor, der auf einem Konzept des Sachverständigenrates für Wirtschaft von 2016 beruht.
In order to decouple economic growth from global material consumption it is necessary to implement material efficiency strategies at the level of single enterprises and their supply chains, and to implement circular economy aspects. Manufacturing firms face multiple implementation challenges like cost limitations, competition, innovation and stakeholder pressure, and supplier and customer relationships, among others. Taking as an example a case of a medium-sized manufacturing company, opportunities to realise material efficiency improvements within the company borders - on the supply chain and by using circular economy measures - are assessed. Deterministic calculations and simulations, performed for the supply chain of this company, show that measures to increase material efficiency in the supply chain are important. However, they need to be complemented by efforts to return waste and used products to the economic cycle, which requires rethinking the traditional linear economic system.
IT platforms as the foundation of digitized processes and products are vital in a digital economy. However, many companies’ platforms are liabilities, not strategic assets because of their complexity. Consequently, companies initiate IT complexity reduction programs. But these technology-centric programs at best provide temporary relief. Soon after, companies’ platforms become just as complex as before. Based on four case studies, we identify three non-technical drivers of platform complexity: (1) Lacking awareness of consequences business decisions have on platform complexity, (2) Lacking motivation to avoid platform complexity, (3) Lacking authority to protect platforms from complexity. We propose measures to address these drivers that can help achieve more sustainable impact on platform complexity: (1) Removing information asymmetries between those creating complexity and those dealing with complexity, (2) Redefining incentives to include long-term effects on platform complexity, (3) Redressing power imbalances between those who create complexity and those who have to manage it.
Electric freight vehicles have the potential to mitigate local urban road freight transport emissions, but their numbers are still insignificant. Logistics companies often consider electric vehicles as too costly compared to vehicles powered by combustion engines. Research within the body of the current literature suggests that increasing the driven mileage can enhance the competitiveness of electric freight vehicles. In this paper we develop a numeric simulation approach to analyze the cost-optimal balance between a high utilization of medium-duty electric vehicles – which often have low operational costs – and the common requirement that their batteries will need expensive replacements. Our work relies on empirical findings of the real-world energy consumption from a large German field test with medium-duty electric vehicles. Our results suggest that increasing the range to the technical maximum by intermediate (quick) charging and multi-shift usage is not the most cost-efficient strategy in every case. A low daily mileage is more cost-efficient at high energy prices or consumptions, relative to diesel prices or consumptions, or if the battery is not safeguarded by a long warranty. In practical applications our model may help companies to choose the most suitable electric vehicle for the application purpose or the optimal trip length from a given set of options. For policymakers, our analysis provides insights on the relevant parameters that may either reduce the cost gap at lower daily mileages, or increase the utilization of medium-duty electric vehicles, in order to abate the negative impact of urban road freight transport on the environment.
Though bioprinting is a forward-looking approach in bone tissue engineering, the development of bioinks which are on the one hand processable with the chosen printing technique, and on the other hand possess the relevant mechanical as well as osteoconductive features remains a challenge. In the present study, polymer solutions based on methacrylated gelatin and methacrylated hyaluronic acid modified with hydroxyapatite (HAp) particles (5 wt%) were prepared. Encapsulation of primary human adipose derived stem cells in the HAp-containing gels and culture for 28 d resulted in a storage moduli significantly increased to 126% ± 9.6% compared to the value on day 1 by the sole influence of the HAp. Additional use of osteogenic media components resulted in an increase of storage module up to 199% ± 27.8%. Similarly, the loss moduli was increased to 370% ± 122.1% under the influence of osteogenic media components and HAp. Those changes in rheological material characteristics indicate a distinct change in elastic and viscous hydrogel properties, and are attributed to extensive matrix production in the hydrogels by the encapsulated cells, what could also be proven by staining of bone matrix components like collagen I, fibronectin, alkaline phosphatase and osteopontin. When using the cell-laden polymer solutions as bioinks to build up relevant geometries, the ink showed excellent printability and the printed grid structure's integrity remained intact over a culture time of 28 d. Again, an intense matrix formation as well as upregulation of osteogenic markers by the encapsulated cells could be shown. In conclusion, we demonstrated that our HAp-containing bioinks and hydrogels on basis of methacrylated gelatin and hyaluronic acid are on the one hand highly suitable for the build up of relevant three-dimensional geometries with microextrusion bioprinting, and on the other hand exhibit a significant positive effect on bone matrix development and remodeling in the hydrogels, as indicated by rheological measurements and staining of bone components. This makes the developed composite hydrogels an excellent material for bone bioprinting approaches.
Understanding the factors that influence the accuracy of visual SLAM algorithms is very important for the future development of these algorithms. So far very few studies have done this. In this paper, a simulation model is presented and used to investigate the effect of the number of scene points tracked, the effect of the baseline length in triangulation and the influence of image point location uncertainty. It is shown that the latter is very critical, while the other all play important roles. Experiments with a well known semi-dense visual SLAM approach are also presented, when used in a monocular visual odometry mode. The experiments show that not including sensor bias and scale factor uncertainty is very detrimental to the accuracy of the simulation results.
In this work we investigate the behavior of MIS- and Schottky-gate AlGaN/GaN HEMTs under high-power pulsestress. A special setup capable of applying pulses of constant power is used to evaluate the electro-thermal response in different operating points. For both types of devices, the time to failure was found to decrease with increasing drain-source voltage. Overall, the Schottky-gate device displays a higher pulse robustness. The pulse withstand time of the MIS-gate device is limited by the occurrence of a thermal instability at approximately 240°C while the Schottky-gate device displays a rapid increase of the gate leakage current prior to failure. The mechanism responsible for this gate current is further investigated by static and transient temperature measurements and yielded activation energies of 0.6 eV and 0.84 eV.