Fakultät Elektrotechnik und Wirtschaftsingenieurwesen
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Cellulose is a promising material for lithium-ion battery separator as it is sustainable, affordable, has excellent electrolyte wettability and is well applicable in lamination-based cell production. Lamination can accelerate the time-consuming stacking step in pouch cell assembly, reduce scrap rate and enhance battery performance, but relies on thermoplastic material on electrode/separator interfaces.
In this work, different surface modification layers were applied to a cellulose separator via electrospinning technique and compared with regard to their applicability for lamination-based cell production. Processes have been developed to apply A) homogeneous fibers consisting of 4 different binder polymer types and b) layers of a fluorothermoplastic polymer (THV) with different morphologies. All layers were applied at the same low areal loading of 0.4 𝑔/𝑚2.
All investigated polymer layers allowed to create mechanically stable interfaces without damaging the separator. The polymers were found to establish maximum adhesion at lamination temperatures that typically are about 10 K above their respective melting temperature. Highest adhesive forces above 15 𝑁/𝑚 were observed at lamination enabled by a low-melting fluoroelastomer (3M FPO 3850) at 120 °C. Evidence was found that many adhesion points well distributed over the surface cause higher adhesion than few large adhesion points, when applied at the same areal loading, but no clear statement can be made as to whether microfibers or microparticles lead to better adhesion. Regarding electrochemical performance, the cellulose separator was shown to be well suited for lithium-ion batteries. All 4 polymers used were found to be electrochemically stable in the applied voltage window and suitable for the use in NMC622 / graphite battery cells. Laminated cells with the developed interlayers showed improved (THV, FPO, PVDFS) or equal (PVDF-K) fast charging and discharging capability. Cells with THV coating performed best in C-rate tests, where their discharge capacity at 3 C rate was improved by 34.1% compared to non-laminated reference cells. Cells with the cellulose separator showed high capacity retention of 89.1% after 500 fast-charging cycles. The morphology of applied layers was not found to have a major influence on electrochemical performance, as long as the binder loading is kept at a moderate level and the deposited layer is porous and well distributed over the separator’s surface.
Due to their qualities to better deal with the unprecedented characteristics of today's VUCA world than conservative project management methods, agile methods have seen an immense upheavel in the industry in recent years – agile methods and the topic of agility in general seem to be inevitable in this context. However, a systematic literature search carried out for the purpose of finding a topic for this master's thesis only confirms this picture to a limited extent: While there is a vast amount of literature on agile methods in project management in general, there is a downright research gap in the more specific field of agile methods in the project management of small and medium sized enterprises (short: SMEs). This insight was taken as an opportunity to bring some light into the dark-ness and to try to fill the existing research gap by attempting to develop a framework for the implementation and utilization of agile methods in the project management of SMEs. In order to create a knowledge base, the theoretical foundation was formed at the very beginning, with a view to both agile project management and SMEs. Subsequently, five specific research questions were defined and a suitable research design was created. In a first round of interviews, twelve problem-centred interviews were conducted with inter-view participants who had experience in the context of agile methods in the project man-agement of SMEs and could report on it. The initial framework based on the resulting findings was then evaluated by five experts in a second round of interviews. After the evaluation of the expert consultation, the initial framework was then modified on the basis of the experts' responses and the final framework was developed. The final framework provides information on what is happening when an agile method is being implemented and later used in the project management of a SME. Therewith, it helps SMEs who are about to introduce an agile method themselves in that they can derive important infor-mation, reference points and recommendations for action from it. For academia, the framework gives rise to further research topics that should be addressed.
This working paper offers an introduction to global sustainability. After a definition of sustainability the status quo is described, which shows the need for transformation. Then the example of climate change illustrates how urgently needed, important, and demanding sustainable solutions are. The following section focuses on businesses as one particular group of players; it explains how they can meet sustainability requirements and which economic models go with them.
This paper assumes it is the year 2051, and we look back to how a new science, Earth Operations Management (EOM), has started and developed since the beginning of the 2020s. EOM was triggered by the idea to regard planet Earth as a business (PEaaB). Millions of business managers were enthused by this idea and have utilized their knowledge and power to achieve PEaaB´s vision: “Humans live their lives with dignity – now and for all generations to come.” The paper reminds of the reasons for PEaaB, its basic characteristics, and key issues from a business management perspective. Then it gives a brief insight into the startup phase of PEaaB and illustrates how it has contributed to climate protection until 2051. The conclusion gets back to the beginning of the 2020s and reflects on this fictional science development review.
Decentralized Synchronization for Energy Efficient Wireless Sensor Networks—A Preliminary Study
(2019)
This research report presents a preliminary study on the use of decentralized synchronization based on pulse-coupled oscillators, also known as firefly synchronization, for energy efficient wireless sensor networks. Numerical results show that synchronity can be reached mostly in a few cycles, thus, showing that the investigated method is a good candidate to synchronize sleep modes which are mainly used to reduce power consumption of network nodes.
Since the late twentieth century, the business environment has changed dramatically: globalization, rapid and even accelerating change, as well as increasing interconnected-ness have presented companies with both great opportunities and challenges. In order to achieve excellence and be successful, it is no longer enough to use conventional tools and methods. Due to their qualities to effectively deal with these changed circumstances, agile development methodologies are increasingly receiving access to the corporate world. The goal of this bachelor's thesis is to ascertain to what extent the "Theory of Inventive Problem Solving" (short: TRIZ/TIPS) can be considered an agile method. To get an overview of both TRIZ/TIPS and agile methods, a thorough literature review on both subjects of matter is conducted at the beginning. Subsequently, a catalogue of criteria for agile meth-ods is developed based on an in-depth literature review on their character. Eventually, interviews with experts are carried out in order to gather their opinion about the concord-ance of TRIZ/TIPS with each of the prior developed criteria for agile methods. By doing so, it is found out that TRIZ/TIPS definitely has agile characteristics and can thus be called partially agile–however, the opinions of the individual experts sometimes vary greatly, and the topic itself seems to be controversial.
This work focuses on providing a convolutional neural network (CNN) architecture for the classification of 3D MRI head scans. In order to offer a comprehensible recommendation for an architecture, this work has four main objectives:
1. Implementation of two CNN architectures based on transfer learning, for the classification of 3D MRI head scans
2. Optimization of both architectures to provide a fair comparison
3. Comparison of both architectures with relevant criteria for the usage of the CNNs in medical diagnosis
4. Evaluation of the effects of transfer learning on both architectures
In order to provide more transparency on convolutional neural networks (CNN) for education and research purposes this work has three main objectives:
• Create CNN models based on two different architectures, which classify magnetic resonance images of the brain into normal and abnormal
• Investigate these models by applying state of the art visualization techniques. For this purpose, a simple accessible Application Interface (API) for Keras sequential models will be developed.
• Describe the quality of the models based on the visualizations and compare their overall classification to the human classification procedure.
The purpose of this work is to evaluate the overall applicability of a rapid room planning tool including a virtual reality visualization mode for a room planning use case in the field of marketing and sales of high involvement medical devices, such as X-ray imaging systems. Four main aspects are identified and evaluated:
▪ The benchmark of VR applications in the field of high involvement marketing and sales, including B2B and B2C use cases.
▪ The potentially savable planning iterations and the associated costs within a room installation process, based on literature review of expert opinions in comparable fields.
▪ The degree of usability of the application, to which extent potential users can create and manipulate room layouts efficiently and without explicit training in advance – assessed in observed user tests with Philips Healthcare employees. Additionally, an employee survey was conducted.
▪ Customer acceptance regarding the concept of VR visualization and the possibly resulting improvement of visual imagination of device proportions in the anticipated environment in comparison to traditional means of product presentation (pictures, videos, real product) – assessed with healthcare professionals.
The benchmark results reveal a multitude of already widely used VR applications in marketing and sales, especially factory planning is considered as a comparable high involvement use case. Subsequently, increased profitability in factory planning can be extended to medical room planning in form of increased efficiency through the reduction of iterations. The overall evaluation of the rapid room planning tool shows a high degree of usability and acceptance among test users and customers. Survey results are independent of customer proximity and age. This work concludes with recommendations for further development and the creation of additional content for the application.