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The development of secure software systems is of ever-increasing importance. While software companies often invest large amounts of resources into the upkeeping and general security properties of large-scale applications when in production, they appear to neglect utilizing threat modeling in the earlier stages of the software development lifecycle. When applied during the design phase of development, and continuously throughout development iterations, threat modeling can help to establish a "Secure by Design" approach. This approach allows issues relating to IT security to be found early during development, reducing the need for later improvement – and thus saving resources in the long term. In this paper the current state of threat modeling is investigated. This investigation drove the derivation of requirements for the development of a new threat modelling framework and tool, called OVVL. OVVL utilizes concepts of established threat modeling methodologies, as well as functionality not available in existing solutions.
The visualization of heart rhythm disturbance and atrial fibrillation therapy allow the optimization of new cardiac catheter ablations. With the simulation software CST (Computer Simulation Technology, Darmstadt) electromagnetic and thermal simulations can be carried out to analyze and optimize different heart rhythm disturbance and cardiac catheters for pulmonary vein isolation. Another form of visualization is provided by haptic, three-dimensional print models. These models can be produced using an additive manufacturing method, such as a 3D printer. The aim of the study was to produce a 3D print of the Offenburg heart rhythm model with a representation of an atrial fibrillation ablation procedure to improve the visualization of simulation of cardiac catheter ablation.
The basis of 3D printing was the Offenburg heart rhythm model and the associated simulation of cryoablation of the pulmonary vein. The thermal simulation shows the pulmonary vein isolation of the left inferior pulmonary vein with the cryoballoon catheter Arctic Front AdvanceTM from Medtronic. After running through the simulation, the thermal propagation during the procedure was shown in the form of different colors. The three-dimensional print models were constructed on the base of the described simulation in a CAD program. Four different 3D printers are available for this purpose in a rapid prototyping laboratory at the University of Applied Science Offenburg. Two different printing processes were used: 1. a binder jetting printer with polymer gypsum and 2. a multi-material printer with photopolymer. A final print model with additional representation of the esophagus and internal esophagus catheter was also prepared for printing.
With the help of the thermal simulation results and the subsequent evaluation, it was possible to make a conclusion about the propagation of the cold emanating from the catheter in the myocardium and the surrounding tissue. It could be measured that already 3 mm from the balloon surface into the myocardium the temperature drops to 25 °C. The simulation model was printed using two 3D printing methods. Both methods as well as the different printing materials offer different advantages and disadvantages. While the first model made of polymer gypsum can be produced quickly and cheaply, the second model made of photopolymer takes five times longer and was twice as expensive. On the other hand, the second model offers significantly better properties and was more durable overall. All relevant parts, especially the balloon catheter and the conduction, are realistically represented. Only the thermal propagation in the form of different colors is not shown on this model.
Three-dimensional heart rhythm models as well as virtual simulations allow a very good visualization of complex cardiac rhythm therapy and atrial fibrillation treatment methods. The printed models can be used for optimization and demonstration of cryoballoon catheter ablation in patients with atrial fibrillation.
The visualization of heart rhythm disturbance and atrial fibrillation therapy allows the optimization of new cardiac catheter ablations. With the simulation software CST (Computer Simulation Technology, Darmstadt) electromagnetic and thermal simulations can be carried out to analyze and optimize different heart rhythm disturbance and cardiac catheters for pulmonary vein isolation. Another form of visualization is provided by haptic, three-dimensional print models. These models can be produced using an additive manufacturing method, such as a 3d printer. The aim of the study was to produce a 3d print of the Offenburg heart rhythm model with a representation of an atrial fibrillation ablation procedure to improve the visualization of simulation of cardiac catheter ablation. The basis of 3d printing was the Offenburg heart rhythm model and the associated simulation of cryoablation of the pulmonary vein. The thermal simulation shows the pulmonary vein isolation of the left inferior pulmonary vein with the cryoballoon catheter Arctic Front Advance™ from Medtronic. After running through the simulation, the thermal propagation during the procedure was shown in the form of different colors. The three-dimensional print models were constructed on the base of the described simulation in a CAD program. Four different 3d printers are available for this purpose in a rapid prototyping laboratory at the University of Applied Science Offenburg. Two different printing processes were used and a final print model with additional representation of the esophagus and internal esophagus catheter was also prepared for printing. With the help of the thermal simulation results and the subsequent evaluation, it was possible to draw a conclusion about the propagation of the cold emanating from the catheter in the myocardium and the surrounding tissue. It was measured that just 3 mm from the balloon surface into the myocardium the temperature dropped to 25 °C. The simulation model was printed using two 3d printing methods. Both methods, as well as the different printing materials offer different advantages and disadvantages. All relevant parts, especially the balloon catheter and the conduction, are realistically represented. Only the thermal propagation in the form of different colors is not shown on this model. Three-dimensional heart rhythm models as well as virtual simulations allow very clear visualization of complex cardiac rhythm therapy and atrial fibrillation treatment methods. The printed models can be used for optimization and demonstration of cryoballoon catheter ablation in patients with atrial fibrillation.
The Internet of Things (IoT) application has becoming progressively in-demand, most notably for the embedded devices (ED). However, each device has its own difference in computational capabilities, memory usage, and energy resources in connecting to the Internet by using Wireless Sensor Networks (WSNs). In order for this to be achievable, the WSNs that form the bulk of the IoT implementation requires a new set of technologies and protocol that would have a defined area, in which it addresses. Thus, IPv6 Low Power Area Network (6LoWPAN) was designed by the Internet Engineering Task Force (IETF) as a standard network for ED. Nevertheless, the communication between ED and 6LoWPAN requires appropriate routing protocols for it to achieve the efficient Quality of Service (QoS). Among the protocols of 6LoWPAN network, RPL is considered to be the best protocol, however its Energy Consumption (EC) and Routing Overhead (RO) is considerably high when it is implemented in a large network. Therefore, this paper would propose the HRPL to enchance the RPL protocol in reducing the EC and RO. In this study, the researchers would present the performance of RPL and HRPL in terms of EC, Control traffic Overhead (CTO) and latency based on the simulation of the 6LoWPAN network in fixed environment using COOJA simulator. The results show HRPL protocol achieves better performance in all the tested topology in terms of EC and CTO. However, the latency of HRPL only improves in chain topology compared with RPL. We found that further research is required to study the relationship between the latency and the load of packet transmission in order to optimize the EC usage.
Radio frequency identification (RFID) antennas are popular for high frequency (HF) RFID, energy transfer and near field communication (NFC) applications. Particularly for wireless measurement systems the RFID/NFC technology is a good option to implement a wireless communication interface. In this context, the design of corresponding reader and transmitter antennas plays a major role for achieving suitable transmission quality. This work proves the feasibility of the rapid prototyping of a RFID/NFC antenna, which is used for the wireless communication and energy harvesting at the required frequency of 13.56 MHz. A novel and low-cost direct ink writing (DIW) technology utilizing highly viscous silver nanoparticle ink is used for this process. This paper describes the development and analysis of low-cost printed flexible RFID/NFC antennas on cost-effective substrates for a microelectronic vital parameter measurement system. Furthermore, we compare the measured technical parameters with existing copper-based counterparts on a FR4 substrate.
The monitoring of industrial environments ensures that highly automated processes run without interruption. However, even if the industrial machines themselves are monitored, the communication lines are currently not continuously monitored in todays installations. They are checked usually only during maintenance intervals or in case of error. In addition, the cables or connected machines usually have to be removed from the system for the duration of the test. To overcome these drawbacks, we have developed and implemented a cost-efficient and continuous signal monitoring of Ethernet-based industrial bus systems. Several methods have been developed to assess the quality of the cable. These methods can be classified to either passive or active. Active methods are not suitable if interruption of the communication is undesired. Passive methods, on the other hand, require oversampling, which calls for expensive hardware. In this paper, a novel passive method combined with undersampling targeting cost-efficient hardware is proposed.
A novel Bluetooth Low Energy advertising scan algorithm is presented for hybrid radios that are additionally capable to measure energy on Bluetooth channels, e.g. as they would need to be compliant with IEEE 802.15.4. Scanners applying this algorithm can achieve a low latency whilst consuming only a fraction of the power that existing mechanisms can achieve at a similar latency. Furthermore, the power consumption can scale with the incoming network traffic and in contrast to the existing mechanisms, scanners can operate without any frame loss given ideal network conditions. The algorithm does not require any changes to advertisers, hence, stays compatible with existing devices. Performance evaluated via simulation and experiments on real hardware shows a 37 percent lower power consumption compared to the best existing scan setting while even achieving a slightly lower latency which proves that this algorithm can be used to improve the quality of service of connection-less Bluetooth communication or reduce the connection establishment time of connection-oriented communication.
High temperature components in internal combustion engines and exhaust systems must withstand severe mechanical and thermal cyclic loads throughout their lifetime. The combination of thermal transients and mechanical load cycling results in a complex evolution of damage, leading to thermomechanical fatigue (TMF) of the material. Analytical tools are increasingly employed by designers and engineers for component durability assessment well before any hardware testing. The DTMF model for TMF life prediction, which assumes that micro-crack growth is the dominant damage mechanism, is capable of providing reliable predictions for a wide range of high-temperature components and materials in internal combustion engines. Thus far, the DTMF model has employed a local approach where surface stresses, strains, and temperatures are used to compute damage for estimating the number of cycles for a small initial defect or micro-crack to reach a critical length. In the presence of significant gradients of stresses, strains, and temperatures, the use of surface field values could lead to very conservative estimates of TMF life when compared with reported lives from hardware testing. As an approximation of gradient effects, a non-local approach of the DTMF model is applied. This approach considers through-thickness fields where the micro-crack growth law is integrated through the thickness considering these variable fields. With the help of software tools, this method is automated and applied to components with complex geometries and fields. It is shown, for the TMF life prediction of a turbocharger housing, that the gradient correction using the non-local approach leads to more realistic life predictions and can distinguish between surface cracks that may arrest or propagate through the thickness and lead to component failure.
When designing and installing Indoor Positioning Systems, several interrelated tasks have to be solved to find an optimum placement of the Access Points. For this purpose, a mathematical model for a predefined number of access points indoors is presented. Two iterative algorithms for the minimization of localization error of a mobile object are described. Both algorithms use local search technique and signal level probabilities. Previously registered signal strengths maps were used in computer simulation.
This paper presents the use of model predictive control (MPC) based approach for peak shaving application of a battery in a Photovoltaic (PV) battery system connected to a rural low voltage gird. The goals of the MPC are to shave the peaks in the PV feed-in and the grid power consumption and at the same time maximize the use of the battery. The benefit to the prosumer is from the maximum use of the self-produced electricity. The benefit to the grid is from the reduced peaks in the PV feed-in and the grid power consumption. This would allow an increase in the PV hosting and the load hosting capacity of the grid.
The paper presents the mathematical formulation of the optimal control problem
along with the cost benefit analysis. The MPC implementation scheme in the
laboratory and experiment results have also been presented. The results show
that the MPC is able to track the deviation in the weather forecast and operate
the battery by solving the optimal control problem to handle this deviation.
A Novel Approach of High Dynamic Current Control of Interior Permanent Magnet Synchronous Machines
(2019)
Harmonic-afflicted effects of permanent magnet synchronous machines with high power density are hardly faced by traditional current PI controllers, due to limited controller bandwidth. As a consequence, currents and lastly torque ripples appear. In this paper, a new deadbeat current controller architecture has been presented, which is capable to encounter the effects of these harmonics. This new control algorithm, here named “Hybrid-Deadbeat-Controller”, combines the stability and the low steady-state errors offered by common PI regulators with the high dynamic offered by the deadbeat control. Therefore, a novel control algorithm is proposed, capable of either compensating the current harmonics in order to get smoother currents or to control a varying reference value to achieve a smoother torque. The information needed to calculate the optimal reference currents is based on an online parameter estimation feeding an optimization algorithm to achieve an optimal torque output and will be investigated in future research. In order to ensure the stability of the controller over the whole area of operation even under the influence of effects changing the system’s parameter, this work as well focusses on the robustness of the “hybrid” dead beat controller.
Many sectors, like finance, medicine, manufacturing, and education, use blockchain applications to profit from the unique bundle of characteristics of this technology. Blockchain technology (BT) promises benefits in trustability, collaboration, organization, identification, credibility, and transparency. In this paper, we conduct an analysis in which we show how open science can benefit from this technology and its properties. For this, we determined the requirements of an open science ecosystem and compared them with the characteristics of BT to prove that the technology suits as an infrastructure. We also review literature and promising blockchain-based projects for open science to describe the current research situation. To this end, we examine the projects in particular for their relevance and contribution to open science and categorize them afterwards according to their primary purpose. Several of them already provide functionalities that can have a positive impact on current research workflows. So, BT offers promising possibilities for its use in science, but why is it then not used on a large-scale in that area? To answer this question, we point out various shortcomings, challenges, unanswered questions, and research potentials that we found in the literature and identified during our analysis. These topics shall serve as starting points for future research to foster the BT for open science and beyond, especially in the long-term.
Robots and automata are key elements of every vision and forecast of life in the near and distant future. However, robots and automata also have a long history, which reaches back into antiquity. Today most historians think that one of the key roles of robots and automata was to amaze or even terrify the audience: They were designed to express something mythical, magical, and not explainable. Moreover, the visions of robots and their envisioned fields of application reflect the different societies. Therefore, this short history of robotics and (especially) anthropomorphic automata aims to give an overview of several historical periods and their perspective on the topic. In a second step, this work aims to encourage readers to reflect on the recent discussion about fields of application as well as the role of robotics today and in the future.
The fast and cost-effective manufacturing of tools for thermoforming is an essential requirement to shorten the development time of products. Thus, additive processes are used increasingly in tooling for thermoforming of plastic sheets. However, a disadvantage of many additive methods is that they are highly cost-intensive, since complex systems based on laser technology and expensive metal powders are needed. Therefore, this paper examines how to work with favorable additive methods, e.g. Binder Jetting, to manufacture tools, which provide sufficient strength for thermoforming. The use of comparatively low-priced inkjet technology for the layer construction and a polymer plaster as material can be expected to result in significant cost reductions. Based on a case study using a cowling (engine bonnet) for an Unmanned Aerial Vehicle (UAV), the development of a complex tool for thermoforming is demonstrated. The object in this study is to produce a tool for a complex-shaped component in small numbers and high quality in a short time and at reasonable costs. Within the tooling process, integrated vacuum channels are implemented in additive tooling without the need for additional post-processing (for example, drilling). In addition, special technical challenges, such as the demolding of undercuts or the parting of the tool are explained. All process steps from tool design to the use of the additively manufactured tool are analyzed. Based on the manufacturing of a small series of cowlings for a UAV made of plastic sheets (ABS), it is shown, that the Binder Jetting offers sufficient mechanical and thermal strength for additive tooling. In addition, an economic evaluation of the tool manufacturing and a detailed consideration of the required manufacturing times for the different process steps are carried out. Finally, a comparison is made with conventional and alternative additive methods of tooling.
What emotional effects does gamification have on users who work or learn with repetitive tasks? In this work, we use biosignals to analyze these affective effects of gamification. After a brief discussion of related work, we describe the implementation of an assistive system augmenting work by projecting elements for guidance and gamification. We also show how this system can be extended to analyse users' emotions. In a user study, we analyse both biosignals (facial expressions and electrodermal activity), and regular performance measures (error rate and task completion time).
For the performance measures, the results confirm known effects like increased speed and slightly increased error rate. In addition, the analysis of the biosignals provides strong evidence for two major affective effects: the gamification of work and learning tasks incites highly significantly more positive emotions and increases emotionality altogether. The results add to the design of assistive systems, which are aware of the physical as well as the affective context.
Apache Hadoop is a well-known open-source framework for storing and processing huge amounts of data. This paper shows the usage of the framework within a project of the university in cooperation with a semiconductor company. The goal of this project was to supplement the existing data landscape by the facilities of storing and analyzing the data on a new Apache Hadoop based platform.
Art and Photonics
(2019)
In this paper we report on our continuous efforts to apply optics and photonics in art. This results in interdisciplinary projects which sometimes lead to concrete art installations.
We presented some of these projects at the UNESCO headquarters in Paris, at the opening ceremony of the International Year of Light and the inaugural ceremony of the International Day of Light.
Some newer projects, such as “A Maze: Ingenious Pipes” and “The Power of Your Eyes,” are also presented in this paper.
More than 200 years ago, the scientist Alexander von Humboldt noted in his travel diaries that "everything is interconnectedness", when he was fascinated by nature and the phenomena observed. The view of nature has become much more detailed through the knowledge of phenomena and natural processes, which led to a more precise view of nature shaped by Humboldt. Technological progress and the artificial intelligence of highly developed computer systems are upsetting this view and changing the established world view through a new, unprecedented interaction between man and machinery. Thus we need digital axioms and comprehensive rules and laws for such autonomous acting systems that determine human interaction between cybernetic systems and biological individuals. This digital humanism should encompass our relationship to nature, our handling of the complexity and diversity of nature and the technological influences on society in order to avoid technical colonialism through supercomputers.
The TriRhenaTech alliance universities and their partners presented their competences in the field of artificial intelligence and their cross-border cooperations with the industry at the tri-national conference 'Artificial Intelligence : from Research to Application' on March 13th, 2019 in Offenburg. The TriRhenaTech alliance is a network of universities in the Upper Rhine Trinational Metropolitan Region comprising of the German universities of applied sciences in Furtwangen, Kaiserslautern, Karlsruhe, and Offenburg, the Baden-Wuerttemberg Cooperative State University Loerrach, the French university network Alsace Tech (comprised of 14 'grandes écoles' in the fields of engineering, architecture and management) and the University of Applied Sciences and Arts Northwestern Switzerland. The alliance's common goal is to reinforce the transfer of knowledge, research, and technology, as well as the cross-border mobility of students.
We present our twenty years of experience in the live broadcasting of astronomical events, with the main focus on total lunar eclipses. Our efforts were motivated by the great impact and high number of viewers of these events. Visitors from over a hundred countries watched our live broadcasts. Our viewer record was set on July 27, 2018, with the live transmission of the total lunar eclipse from the Feldberg, the highest mountain in the Black Forest, attracting nearly half a million viewers in five hours.
An especially challenging activity was the live observing of the Mercury transit on 9 May 2016, which we presented as ‘live astronomy’ with hands-on telescope. The main goal of this event was to awake our students enthusiasm for optics and astronomy.
Furthermore, we report on our experiences with the photography of optical phenomena such as polar lights and green flash.
Medical devices accompany our everyday life and come across in situations of worse condition, in significant moments concerning the health or during routine checkups. To ensure flawless operations and error-free results it is essential to test applications and devices. High risks for patient’s health come with operating errors [33] so that the presented research project, called Professional UX, identifies signals and irritations caused by the interaction with a certain device by analyzing mimic, voice and eye tracking data during user experience tests. Besides, this paper will provide information on typical errors of interactive applications which are based on an empirical lab-based survey and the evaluated results achieved. The pictured proceeding of user experience tests and the following analysis can also be applied to other fields and serves as a support for the optimization of products and systems.
In many application domains, in particular automotives, guaranteeing a very low failure rate is crucial to meet functional and safety standards. Especially, reliable operation of memory components such as SRAM cells is of essential importance. Due to aggressive technology downscaling, process and runtime variations significantly impact manufacturing yield as well as functionality. For this reason, a thorough memory failure rate assessment is imperative for correct circuit operation and yield improvement. In this regard, Monte Carlo simulations have been used as the conventional method to estimate the variability induced failure rate of memory components. However, Monte Carlo methods become infeasible when estimating rare events such as high-sigma failure rates. To this end, Importance Sampling methods have been proposed which reduce the number of required simulations substantially. However, existing methods still suffer from inaccuracies and high computational efforts, in particular for high-sigma problems. In this paper, we fill this gap by presenting an efficient mixture Importance Sampling approach based on Bayesian optimization, which deploys a surface model of the objective function to find the most probable failure points. Its advantages include constant complexity independent of the dimensions of design space, the potential to find the global extrema, and higher trustworthiness of the estimated failure rate by accurately exploring the design space. The approach is evaluated on a 6T-SRAM cell as well as a master-slave latch based on a 28nm FDSOI process. The results show an improvement in accuracy, resulting in up to 63× better accuracy in estimating failure rates compared to the best state-of-the-art solutions on a 28nm technology node.
Besides of conventional CAD systems, new, cloud-based CAD systems have also been available for some years. These CAD systems designed according to the principle of software as a service (SaaS) differ in some important features from the conventional CAD systems. Thus, these CAD systems are operated via a browser and it is not necessary to install the software on a computer. The CAD-data is stored in the cloud and not on a local computer or central server. This new approach should also facilitate the sharing and management of data. Finally, many of these new CAD systems are available as freeware for education purposes, so the universities can save license costs. This contribution examines newly developed, cloud-based CAD systems. In the context of a case study, the application of these new CAD systems are investigated in the training of engineers in design education. Thus, the students compare a conventional and a cloud-based CAD system as part of an exercise of designing and 3D modelling of a pinion shaft. Subsequently, the students manufacture a drawing with different views of the pinion shaft. This assessment evaluates different criteria such as user-friendliness, tutorial support and installation effort.
Classification of TRIZ Inventive Principles and Sub-Principles for Process Engineering Problems
(2019)
The paper proposes a classification approach of 40 Inventive Principles with an extended set of 160 sub-principles for process engineering, based on a thorough analysis of 155 process intensification technologies, 200 patent documents, 6 industrial case studies applying TRIZ, and other sources. The authors define problem-specific sub-principles groups as a more precise and productive ideation technique, adaptable for a large diversity of problem situations, and finally, examine the anticipated variety of ideation using 160 sub-principles with the help of MATCEM-IBD fields.
Protecting software from illegal access, intentional modification or reverse engineering is an inherently difficult practical problem involving code obfuscation techniques and real-time cryptographic protection of code. In traditional systems a secure element (the "dongle") is used to protect software. However, this approach suffers from several technical and economical drawbacks such as the dongle being lost or broken.
We present a system that provides such dongles as a cloud service, and more importantly, provides the required cryptographic material to control access to software functionality in real-time.
This system is developed as part of an ongoing nationally funded research project and is now entering a first trial stage with stakeholders from different industrial sectors.
With the growing share of renewable energies in the electricity supply, transmission and distribution grids have to be adapted. A profound understanding of the structural characteristics of distribution grids is essential to define suitable strategies for grid expansion. Many countries have a large number of distribution system operators (DSOs) whose standards vary widely, which contributes to coordination problems during peak load hours. This study contributes to targeted distribution grid development by classifying DSOs according to their remuneration requirement. To examine the amendment potential, structural and grid development data from 109 distribution grids in South-Western Germany, are collected, referring to publications of the respective DSOs. The resulting data base is assessed statistically to identify clusters of DSOs according to the fit of demographic requirements and grid-construction status and thus identify development needs to enable a broader use of regenerative energy resources. Three alternative algorithms are explored to manage this task. The study finds the novel Gauss-Newton algorithm optimal to analyse the fit of grid conditions to regional requirements and successfully identifies grids with remuneration needs. It is superior to the so far used K-Means algorithm. The method developed here is transferable to other areas for grid analysis and targeted, cost-efficient development.
In this article the high-temperature behavior of a cylindrical lithium iron phosphate/graphite lithium-ion cell is investigated numerically and experimentally by means of differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), and external short circuit test (ESC). For the simulations a multi-physics multi-scale (1D+1D+1D) model is used. Assuming a two-step electro-/thermochemical SEI formation mechanism, the model is able to qualitatively reproduce experimental data at temperatures up to approx. 200 °C. Model assumptions and parameters could be evaluated via comparison to experimental results, where the three types of experiments (DSC, ARC, ESC) show complementary sensitivities towards model parameters. The results underline that elevated-temperature experiments can be used to identify parameters of the multi-physics model, which then can be used to understand and interpret high-temperature behavior. The resulting model is able to describe nominal charge/discharge operation behavior, long-term calendaric aging behavior, and short-term high-temperature behavior during extreme events, demonstrating the descriptive and predictive capabilities of physicochemical models.
The authors explain a developed concept for research-oriented education in optics and photonics. It is presented which goals are to be achieved, which strategies have been developed and how these can be implemented in a blended learning scenario. The goal of our education is the best possible qualification of the students on the basis of a strong scientific and research-oriented education, which also includes the acquisition of important interdisciplinary competences. All phases of a research process are to be mapped in the learning process and offer students an insight into current research topics in optics and photonics.
The development of secure software systems is of ever-increasing importance. While software companies often invest large amounts of resources into the upkeeping and general security properties of large-scale applications when in production, they appear to neglect utilizing threat modeling in the earlier stages of the software development lifecycle. When applied during the design phase of development, and continuously during development iterations, threat modeling can help in following a “Security by Design” approach. This approach allows issues relating to IT security to be found early during development, reducing the need for later improvement – and thus saving resources in the long term. In this thesis the current state of threat modeling is investigated. Based on this analysis, requirements for a new tool are derived. These requirements are then used to develop a new tool, called OVVL, which utilizes all main components of current threat modeling methodologies, as well as functionality not available in existing solutions. After documenting the development process and OVVL in general, this newly developed tool is used to conduct two case studies in the field of e-commerce and IoT.
Cast aluminum alloys are frequently used as materials for cylinder head applications in internal combustion gasoline engines. These components must withstand severe cyclic mechanical and thermal loads throughout their lifetime. Reliable computational methods allow for accurate estimation of stresses, strains, and temperature fields and lead to more realistic Thermomechanical Fatigue (TMF) lifetime predictions. With accurate numerical methods, the components could be optimized via computer simulations and the number of required bench tests could be reduced significantly. These types of alloys are normally optimized for peak hardness from a quenched state that maximizes the strength of the material. However due to high temperature exposure, in service or under test conditions, the material would experience an over-ageing effect that leads to a significant reduction in the strength of the material. To numerically account for ageing effects, the Shercliff & Ashby ageing model is combined with a Chaboche-type viscoplasticity model available in the finite-element program ABAQUS by defining field variables. The constitutive model with ageing effects is correlated with uniaxial cyclic isothermal tests in the T6 state, the overaged state, as well as thermomechanical tests. On the other hand, the mechanism-based TMF damage model (DTMF) is calibrated for both T6 and over-aged state. Both the constitutive and the damage model are applied to a cylinder head component simulating several cycles on an engine dynamometer test. The effects of including ageing for both models are shown.
Walking interfaces offer advantages in navigation of VE systems over other types of locomotion. However, VR helmets have the disadvantage that users cannot see their immediate surroundings. Our publication describes the prototypical implementation of a virtual environment (VE) system, capable of detecting possible obstacles using an RGB-D sensor. In order to warn users of potential collisions with real objects while they are moving throughout the VE tracking area, we designed 4 different visual warning metaphors: Placeholder, Rubber Band, Color Indicator and Arrow. A small pilot study was carried out in which the participants had to solve a simple task and avoid any arbitrarily placed physical obstacles when crossing the virtual scene. Our results show that the Placeholder metaphor (in this case: trees), compared to the other variants, seems to be best suited for the correct estimation of the position of obstacles and in terms of the ability to evade them.
A physical unclonable function (PUF) is a hardware circuit that produces a random sequence based on its manufacturing-induced intrinsic characteristics. In the past decade, silicon-based PUFs have been extensively studied as a security primitive for identification and authentication. The emerging field of printed electronics (PE) enables novel application fields in the scope of the Internet of Things (IoT) and smart sensors. In this paper, we design and evaluate a printed differential circuit PUF (DiffC-PUF). The simulation data are verified by Monte Carlo analysis. Our design is highly scalable while consisting of a low number of printed transistors. Furthermore, we investigate the best operating point by varying the PUF challenge configuration and analyzing the PUF security metrics in order to achieve high robustness. At the best operating point, the results show areliability of 98.37% and a uniqueness of 50.02%, respectively. This analysis also provides useful and comprehensive insights into the design of hybrid or fully printed PUF circuits. In addition, the proposed printed DiffC-PUF core has been fabricated with electrolyte-gated field-effect transistor technology to verify our design in hardware.
Hot working tools are subjected to complex thermal and mechanical loads during service. Locally, the stresses can exceed the material’s yield strength in highly loaded areas. During production, this causes cyclic plastic deformation and thus thermomechanical fatigue, which can significantly shorten the lifetime of hot working tools. To sustain this high loads, the hot working tools are typically made of tempered martensitic hot work tool steels. While the annealing temperatures of the tool steels usually lie in the range of 400 to 600 °C, the steels may experience even higher temperatures during hot working, resulting in softening of the material due to changes in microstructure. Therefore, the temperature-dependent cyclic mechanical properties of the frequently used hot work tool steel 1.2367 (X38CrMoV5-3) after tempering are investigated in this work. To this end, hardness measurements are performed. Furthermore, the Institute of Forming Technology and Machines (IFUM) provides test results from cyclic tests at temperatures ranging from 20 °C (room temperature) to 650 °C. To describe the observed time- and temperature-dependent softening during tempering, a kinetic model for the evolution of the mean size of secondary carbides based on Ostwald ripening is developed. In addition, both mechanism-based and phenomenological relationships for the cyclic mechanical properties of the Ramberg- Osgood model depending on carbide size and temperature are proposed. The stress-strain hysteresis loops measured at different temperatures and after different heat treatments can be well described with the proposed kinetic and mechanical model. Furthermore, the model is suitable for integration in advanced mechanism-based lifetime models. However, since the Ramberg-Osgood model is not suitable for finite element implementation, a temperature-dependent incremental cyclic plasticity model is presented as well. Thus, softening due to particle coarsening can be applied in the finite element method (FEM). Therefore, a kinetic model is coupled with a cyclic plasticity model including kinematic hardening. The plasticity model is implemented via subroutines in the finite element program ABAQUS for implicit integration (subroutine called UMAT) and explicit integration (subroutine called VUMAT). The implemented model is used for the simulation of an exemplary hot working process to assess the effects of softening due to particle coarsening. It shows that the thermal softening at high temperatures, which occur over a long time at a mechanically highly loaded area, has a great influence. If this influence is not considered in tool design, an unexpected tool failure might occur bringing the production to a standstill.
Dissertation D. Dongol
In this article we outline the model development planned within the joint projectModel-based city planningand application in climate change (MOSAIK). The MOSAIK project is funded by the German FederalMinistry of Education and Research (BMBF) within the frameworkUrban Climate Under Change ([UC]2)since 2016. The aim of MOSAIK is to develop a highly-efficient, modern, and high-resolution urban climatemodel that allows to be applied for building-resolving simulations of large cities such as Berlin (Germany).The new urban climate model will be based on the well-established large-eddy simulation code PALM, whichalready has numerous features related to this goal, such as an option for prescribing Cartesian obstacles. Inthis article we will outline those components that will be added or modified in the framework of MOSAIK.Moreover, we will discuss the everlasting issue of acquisition of suitable geographical information as inputdata and the underlying requirements from the model's perspective.
The ability to change aerodynamic parameters of airfoils during flying can potentially save energy as well as reducing the noise made by the unmanned aerial vehicles (UAV) because of sharp edges of the airfoil and its rudders. In this paper, an approach for the design of an adaptive wing using a multi-material 3D printer is shown. In multi-material 3D printing, up to six different materials can be combined in one component. Thus, the user can determine the mixture and the spatial arrangement of this “digital material” in advance in the pre-processing software. First, the theoretical benefits of adaptive wings are shown, and already existing adaptive wings and concepts are explicated within a literature review. Then the additive manufacturing process using photopolymer jetting and its capabilities to print multiple materials in one part are demonstrated. Within the scope of a case study, an adaptive wing is developed and the necessary steps for the product development and their implementation in CAD are presented. This contribution covers the requirements for different components and sections of an adaptive wing designed for additive manufacturing using multiple materials as well as the single steps of development with its different approaches until the final design of the adaptive wing. The developed wing section is simulated, and qualitative tests in a wind tunnel are carried out with the wing segment. Finally, the additively manufactured wing segment is evaluated under technical and economic aspects.
Development of Fully Printed Oxide Field-Effect Transistors using Graphene Passive Structures
(2019)
During the past decade to the present time, the topic of printed electronics has gained a lot of attention for their potential use in a number of practical applications, including biosensors, photovoltaic devices, RFIDs, flexible displays, large-area circuits, and so on. To fully realize printed electronic components and devices, effective techniques for the printing of passive structures and electrically and chemically compatible materials in the printed devices need to be developed first. The opportunity of using electrically conducting graphene inks will enable the integration of passive structures into active devices, as for example, printed electrolyte-gated transistors (EGTs). Accordingly, in this study, we present the parametric results obtained on fully printed electrolyte-gated transistors having graphene as the passive electrodes, an inorganic oxide semiconductor as the active channel, and a composite solid polymer electrolyte (CSPE) as the gate insulating material. This configuration offers high chemical and electrical stability while at the same time allowing EGT operation at low potentials, implying the distinct advantage of operation at low input voltages. The printed in-plane EGTs we developed exhibit excellent performance with device mobility up to 16 cm2 V–1 s–1, an ION/IOFF ratio of 105, and a subthreshold slope of 120 mV dec–1.
Direct Digital Manufacturing of Architectural Models using Binder Jetting and Polyjet Modeling
(2019)
Today, architectural models are an important tool for illustrating drawn-on plansor computer-generated virtual models and making them understandable. Inaddition to the conventional methods for the manufacturing of physical models, awide range of processes for Direct Digital Manufacturing (DDM) has spreadrapidly in recent years. In order to facilitate the application of these new methodsfor architects, this contribution examines which technical and economic resultsare possible using 3D printed architectural models. Within a case study, it will beshown on the basis of a multi-storey detached house, which kind of datapreparation is necessary. The DDM of architectural models will be demonstratedusing two widespread techniques and the resulting costs will be compared.
Economic growth and ecological problems motivate industries to apply eco-friendly technologies and equipment. However, environmental impact, followed by energy and material consumption still remain the main negative implications of the technological progress in process engineering. Based on extensive patent analysis, this paper assigns more than 250 identified eco-innovation problems and requirements to 14 general eco-categories with energy consumption and losses, air pollution, and acidification as top issues. It defines primary eco-engineering contradictions, in case eco-problems appear as negative side effects of the new technologies, and secondary eco-engineering contradictions, if eco-friendly solutions have new environmental drawbacks. The study conceptualizes a correlation matrix between the eco-requirements for prediction of typical eco-contradictions on example of processes involving solids handling. Finally, it summarizes major eco-innovation approaches including Process Intensification in process engineering, and chronologically reviews 66 papers on eco-innovation adapting TRIZ methodology. Based on analysis of 100 eco-patents, 58 process intensification technologies, and literature, the study identifies 20 universal TRIZ inventive principles and sub-principles that have a higher value for environmental innovation.
Process engineering industries are now facing growing economic pressure and societies' demands to improve their production technologies and equipment, making them more efficient and environmentally friendly. However unexpected additional technical and ecological drawbacks may appear as negative side effects of the new environmentally-friendly technologies. Thus, in their efforts to intensify upstream and downstream processes, industrial companies require a systematic aid to avoid compromising of ecological impact. The paper conceptualises a comprehensive approach for eco-innovation and eco- design in process engineering. The approach combines the advantages of Process Intensification as Knowledge-Based Engineering (KBE), inventive tools of Knowledge-Based Innovation (KBI), and main principles and best-practices of Eco-Design and Sustainable Manufacturing. It includes a correlation matrix for identification of eco-engineering contradictions and a process mapping technique for problem definition, database of Process Intensification methods and equipment, as well as a set of strongest inventive operators for eco-ideation.
As engineering graduates and specialists frequently lack the advanced skills and knowledge required to run eco-innovation systematically, the paper proposes a new teaching method and appropriate learning materials in the field of eco-innovation and evaluates the learning experience and outcomes. This programme is aimed at strengthening student’s skills and motivation to identify and creatively overcome secondary eco-contradictions in case if additional environmental problems appears as negative side effects of eco-friendly solutions.
Based on a literature analysis and own investigations, authors propose to introduce a manageable number of eco-innovation tools into a standard one-semester design course in process engineering with particular focus on the identification of eco-problems in existing technologies, selection of the appropriate new process intensification technologies (knowledge-based engineering), and systematic ideation and problem solving (knowledge-based innovation and invention).
The proposed educational approach equips students with the advanced knowledge, skills and competences in the field of eco-innovation. Analysis of the student’s work allows one to recommend simple-to-use tools for a fast application in process engineering, such as process mapping, database of eco-friendly process intensification technologies, and up to 20 strongest inventive operators for solving of environmental problems. For the majority of students in the survey, even the small workload has strengthened their self-confidence and skills in eco-innovation
Background: Pulmonary vein isolation (PVI) using cryoballoon catheters are a recognized method for the treatment of atrial fibrillation (AF). This method offers shorter treatment duration in contrast to the classical therapy with high-frequency (HF) ablation.
Purpose: The aim of this study was to integrate different cryoballoon catheters and a HF catheter into a heart rhythm model and to compare them by means of static and dynamic electromagnetic and thermal simulation in use under AF.
Methods: The cryoballoon catheters from Medtronic and the HF ablation catheter from Osypka were modelled virtually with the aid of manufacturer specifications and the CST (Computer Simulation Technology, Darmstadt) simulation program. The cryoballoon catheter was located in the lower left pulmonary vein of the virtual heart rhythm model for the realization of pulmonary vein isolation (PVI) by cryoenergy. The simulated temperature at the balloon surface was -50°C during the simulation.
Results: During a simulated 20 second application of a cryoballoon catheter at -50°C, a temperature of -24°C was measured at a depth of 0.5 mm in the myocardium. At a depth of 1 mm the temperature was -3°C, at 2 mm depth 18°C and at 3 mm depth 29°C. Under the 15 second application of a RF catheter with a 8 mm electrode and a power of 5 W at 420 kHz, the temperature at the tip of the electrode was 110°C. At a depth of 0.5 mm in the myocardium, the temperature was 75°C, at a depth of 1 mm 58°C, at 2 mm depth 45°C and at 3 mm depth 38°C.
Conclusions: The simulation of temperature profiles during the virtual application of several catheter models in the heart rhythm model allows the static and dynamic simulation of PVI by cryoballoon ablation and RF ablation. The three-dimensional simulation can be used to improve ablation applications by creating a model in personalized cardiac rhythm therapy from MRI or CT data of a heart and finding a favourable position for ablation of AF.
Background: The application of high-frequency ablation is used for the treatment of tachycardia arrhythmias and is a respected method. Ablation with high frequency current leads to the targeted heat destruction of myocardial tissue at specific sites and thus prevents the pathological propagation of excitation through these structures.
Purpose: The aim of this study was to simulate heat propagation during RF ablation with modeled electrodes in different sizes and materials. The simulation was performed on atrioventricular node re-entry tachycardia (AVNRT), atrioventricular re-entry tachycardia (AVRT) and atrial flutter (AFL).
Methods: Using the modeling and simulation software CST, ablation catheters with 4 mm and 8 mm tip electrodes were modeled from gold and platinum for each. The designed catheters correspond to the manufacturer"s specifications of Medtronic, Biotronik and Osypka. The catheters were integrated into the Offenburg heart rhythm model to simulate and compare the heat propagation during an ablation application, which also takes into account the blood flow in the four heart chambers. A power of 5 W - 40 W was simulated for the 4 mm electrodes and a power of 50 W - 80 W for the 8 mm electrodes.
Results: During the simulated HF ablation application, the temperature at the ablation electrode was measured at different powers. This is 40.67°C at 5 W, 44.34°C at 10 W, 51.76°C at 20 W, 59.0°C at 30 W, and 66.33°C at 40 W. The measured temperature during 40 W application is 39.5°C at 0,5 mm depth in the myocardium and 37.5°C at 2 mm depth.
In the simulation, the 8 mm platinum electrode reached an ablation temperature of 72.85°C at its tip during an applied power of 60 W. In contrast, the 8 mm platinum electrode reached a depth of 5 mm at 39.5 C° and at a depth of 2 mm at 37.5 °C. In contrast, the 8 mm gold electrode reached a temperature of 64.66°C with the same performance. This is due to the thermal properties of gold, which has a better thermal conductivity than platinum.
Conclusions: CST offers the possibility to carry out a static and dynamic simulation of a heart model and the ablation electrodes integrated in it during an HF ablation. In variation with different electrode sizes and materials, therapy methods for the treatment of AVNRT, AVRT and AFL can be optimized
Kommentar zum Artikel "Arthur Willis Goodspeed" von Otto Glasser, veröffentlicht in Science Vol. 98, Issue 2540, Seite 219 (doi.org/10.1126/science.98.2536.125).
Smart Home or Smart Building applications are a growing market. An increasing challenge is to design energy efficient Smart Home applications to achieve sustainable and green homes. Using the example of the development of an Indoor Smart Gardening system with wireless monitoring and automated watering this paper is discussing in particular the design issue of energy autonomous working sensors and actuators for home automation. Most important part of the presented Smart Gardening system is a 3D printed smart flower pot for single plants. The smart flower pot has integrated a water reservoir for automated plant irrigation and an electronic for monitoring important plant parameters and the water level of the water reservoir. Energy harvesting with solar cells enables energy autonomous working of the flower pot. A low-power wireless interface also integrated in the flowerpot and an external gateway based on a Raspberry Pi 3 enables wireless networking of multiple of those flower pots. The gateway is used for evaluating the plant parameters and as a user interface. Particularly the architecture of the energy autonomous wireless flower pot will be considered, because fully energy autonomous sensors and actuators for home automation could not be implemented without special concepts for the energy supply and the overall electronic.
Spinal cord stimulation (SCS) is the most commonly used technique of neurostimulation. It involves the stimulation of the spinal cord and is therefore used to treat chronic pain. The existing esophageal catheters are used for temperature monitoring during an electrophysiology study with ablation and transesophageal echocardiography. The aim of the study was to model the spine and new esophageal electrodes for the transesophageal electrical pacing of the spinal cord, and to integrate them in the Offenburg heart rhythm model for the static and dynamic simulation of transesophageal neurostimulation. The modeling and simulation were both performed with the electromagnetic and thermal simulation software CST (Computer Simulation Technology, Darmstadt). Two new esophageal catheters were modelled as well as a thoracic spine based on the dimensions of a human skeleton. The simulation of directed transesophageal neurostimulation is performed using the esophageal balloon catheter with an electric pacing potential of 5 V and a trapezoidal signal. A potential of 4.33 V can be measured directly at the electrode, 3.71 V in the myocardium at a depth of 2 mm, 2.68 V in the thoracic vertebra at a depth of 10 mm, 2.1 V in the thoracic vertebra at a depth of 50 mm and 2.09 V in the spinal cord at a depth of 70 mm. The relation between the voltage delivered to the electrodes and the voltage applied to the spinal cord is linear. Virtual heart rhythm and catheter models as well as the simulation of electrical pacing fields and electrical sensing fields allow the static and dynamic simulation of directed transesophageal electrical pacing of the spinal cord. The 3D simulation of the electrical sensing and pacing fields may be used to optimize transesophageal neurostimulation.
Spinal cord stimulation (SCS) is the most commonly used technique of neurostimulation. It involves the stimulation of the spinal cord and is therefore used to treat chronic pain. The existing esophageal catheters are used for temperature monitoring during an electrophysiology study with ablation and transesophageal echocardiography. The aim of the study was to model the spine and new esophageal electrodes for the transesophageal electrical pacing of the spinal cord, and to integrate them in the Offenburg heart rhythm model for the static and dynamic simulation of transesophageal neurostimulation. The modeling and simulation were both performed with the electromagnetic and thermal simulation software CST (Computer Simulation Technology, Darmstadt). Two new esophageal catheters were modelled as well as a thoracic spine based on the dimensions of a human skeleton. The simulation of directed transesophageal neurostimulation is performed using the esophageal balloon catheter with an electric pacing potential of 5 V and a trapezoidal signal. A potential of 4.33 V can be measured directly at the electrode, 3.71 V in the myocardium at a depth of 2 mm, 2.68 V in the thoracic vertebra at a depth of 10 mm, 2.1 V in the thoracic vertebra at a depth of 50 mm and 2.09 V in the spinal cord at a depth of 70 mm. The relation between the voltage delivered to the electrodes and the voltage applied to the spinal cord is linear. Virtual heart rhythm and catheter models as well as the simulation of electrical pacing fields and electrical sensing fields allow the static and dynamic simulation of directed transesophageal electrical pacing of the spinal cord. The 3D simulation of the electrical sensing and pacing fields may be used to optimize transesophageal neurostimulation.