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This experimental study demonstrates for the first time a solid-state circuitry and design for a simple compact copper coil (without an additional bulky permanent magnet or bulky electromagnet) as a contactless electromagnetic acoustic transducer (EMAT) for pulse echo operation at MHz frequencies. A pulsed ultrasound emission into a metallic test object is electromagnetically excited by
an intense MHz burst at up to 500 A through the 0.15 mm filaments of the transducer. Immediately thereafter, a smoother and quasi “DC-like” current of 100 A is applied for about 1 ms and allows an
echo detection. The ultrasonic pulse echo operation for a simple, compact, non-contacting copper coil is new. Application scenarios for compact transducer techniques include very narrow and
hostile environments, in which, e.g., quickly moving metal parts must be tested with only one, non-contacting ultrasound shot. The small transducer coil can be operated remotely with a cable
connection, separate from the much bulkier supply circuitry. Several options for more technical and fundamental progress are discussed.
Electro-magnetic acoustic transducers (EMATs) are intended as non-contact and non-destructive ultrasound transducers for metallic material. The transmitted intensities from EMATS are modest, particularly at notable lift off distances. Some time ago a concept for a “coil only EMAT” was presented, without static magnetic field. In this contribution, such compact “coil only EMATs” with effective areas of 1–5 cm2 were driven to excessive power levels at MHz frequencies, using pulsed power technologies. RF induction currents of 10 kA and tens of Megawatts are applied. With increasing power the electroacoustic conversion efficiency also increases. The total effect is of second order or quadratic, therefore non-linear and progressive, and yields strong ultrasound signals up to kW/cm2 at MHz frequencies in the metal. Even at considerable lift off distances (cm) the ultrasound can be readily detected. Test materials are aluminum, ferromagnetic steel and stainless steel (non-ferromagnetic). Thereby, most metal types are represented. The technique is compared experimentally with other non-contact methods: laser pulse induced ultrasound and spark induced ultrasound, both damaging to the test object’s surface. At small lift off distances, the intensity from this EMAT concept clearly outperforms the laser pulses or heavy spark impacts.
Inverter auf Basis der Pulsweitenmodulation dominieren in dem heutigen Stand der Technik. Wie bei den meisten elektronischen Einrichtungen entstehen während ihres Betriebs mehr oder weniger ungewollte Störungen, welche zur Beeinträchtigung der Funktion von anderen Geräten oder elektronischen Schaltungen führen. Die dafür angewandten technischen Gegenmaßnahmen scheinen meist aufwandmäßig hoch zu sein insbesondere bei kritischen elektrischen Einrichtungen. Dank der Resonanzinvertertopologie wird dieser Aufwand zum größten Teil erspart. Der Aufbau und die Funktionsweise der beiden Invertertopologien werden einzeln erläutert. Nach einigen Simulationsdurchführungen, welche unter verschiedenen Betriebsfrequenzen nacheinander erfolgen, werden die beiden Inverter gegenübergestellt und Mithilfe der Simulationsergebnisse verglichen. Aus den allgemeinen Vergleichen stellt sich heraus, dass die Resonanzinvertertopologie insbesondere bei niedrigen Frequenzen im EMV-Aspekt sowie unter Betrachtung der Leistungsfähigkeit den SVPWM-Inverter gewinnt. Während der Resonanzinverter in den niedrigen Frequenzen mehr Störaussendungen als der SVPWM-Inverter produziert, ist das Phänomen bei höheren Frequenzen eher invers.
In this contribution we present a novel approach to transform data from time-of-flight (ToF) sensors to be interpretable by Convolutional Neural Networks (CNNs). As ToF data tends to be overly noisy depending on various factors such as illumination, reflection coefficient and distance, the need for a robust algorithmic approach becomes evident. By spanning a three-dimensional grid of fixed size around each point cloud we are able to transform three-dimensional input to become processable by CNNs. This simple and effective neighborhood-preserving methodology demonstrates that CNNs are indeed able to extract the relevant information and learn a set of filters, enabling them to differentiate a complex set of ten different gestures obtained from 20 different individuals and containing 600.000 samples overall. Our 20-fold cross-validation shows the generalization performance of the network, achieving an accuracy of up to 98.5% on validation sets comprising 20.000 data samples. The real-time applicability of our system is demonstrated via an interactive validation on an infotainment system running with up to 40fps on an iPad in the vehicle interior.
We present a pipeline for recognizing dynamic freehand gestures on mobile devices based on extracting depth information coming from a single Time-of-Flight sensor. Hand gestures are recorded with a mobile 3D sensor, transformed frame by frame into an appropriate 3D descriptor and fed into a deep LSTM network for recognition purposes. LSTM being a recurrent neural model, it is uniquely suited for classifying explicitly time-dependent data such as hand gestures. For training and testing purposes, we create a small database of four hand gesture classes, each comprising 40 × 150 3D frames. We conduct experiments concerning execution speed on a mobile device, generalization capability as a function of network topology, and classification ability ‘ahead of time’, i.e., when the gesture is not yet completed. Recognition rates are high (>95%) and maintainable in real-time as a single classification step requires less than 1 ms computation time, introducing freehand gestures for mobile systems.
This thesis examines the role of economy in the transformation of Japanese energy supply. In 2021, following the Paris Agreement example, the Japanese Government formulates their “6th Energy plan” to realize the country's national energy policy aims to reduce CO2 emissions and secure energy supplies while increasing economic efficiency. This entails an emission reduction target of nearly 50 % compared to 2013 by 2030 and a complete greenhouse gas emission neutrality target by 2050. In order to achieve these Japan plans to reduce traditional combustibles fuels and introduce renewables as main sources, while nuclear energy will be used as support and safety load. The Japanese Government ensures of the necessity of the nuclear technology in spite of the critical effects the Fukushima accident had on the nation.
Japans energy supply depends by majority on fuel imports. The rising prices of fossil fuels, which are due to the Russian aggression, are causing economic hardships in Japan, which the Government is attempting to contain. These hardships are one of the assumed reasons of the sudden changes in the energy policies. Two hypotheses are established. The first one is that the METI is the main contributor of policy making and main force of the energy transfor-mation, therefore economic reasons guide the energy plan. The second one is that the nuclear energy is preferred because of complex external factors, like stakeholder and historical pecu-liarities of the energy sector. Most importantly, climate protection is only of secondary im-portance in the energy transformation. Asserting that economical motives are the main drivers of energy transformation, the Japanese 6th energy strategy is therefore analyzed. The Rational Choice theorem is chosen to be the academic foundation of this thesis. The theory describes a decision-making process which compares alternative paths of action and identifies the most suitable choice. Main elements are the “decision-making rule” and an “environmental-factor”. In the analysis of this thesis a "cost reducing" decision rule is adopted. The analysis consists of two parts in which these elements are analyzed.
The analysis is resulting in the recognition of METI as the most influential political organ. Ad-ditionally, the transformation of Japanese energy supply is heavily influenced by extern parties, especially the industry and businesses. The Keidanren and members of the “nuclear village” are found to be influencers and driving forces for nuclear energy. Furthermore, the analyze underlines the clear preference of METI for nuclear energy. Although different opinions in the midst of Japanese government (first and foremost the MOE) exist, there are no real competitor against METIs policy making. The thesis concludes that as long as METI and its beneficiaries are not willing to change the energy mix, nothing is changing. The academic research has demonstrated that even a more ambitious plan and a greater commitment to renewable ener-gies can achieve base load capability, but the government does not welcome such plans.
Die Digitalisierung des deutschen Gesundheitswesens ist im direkten Vergleich zu anderen Branchen und Gesundheitswesen deutlich im Rückstand. Ursachen für diesen Rückstand sollten identifiziert werden, um aus den gefundenen Faktoren Handlungsempfehlungen zu entwickeln, die dabei helfen sollen künftige Digitalisierungsprojekte effizienter zu gestalten. Zur Identifizierung wurde zunächst eine unstrukturierte Literaturrecherche durchgeführt, gefolgt von Experteninterviews, die den eigentlichen Kern der Arbeit darstellen. Die ausgewählten Probanden stellen Beteiligten des Projektes elektronische Arbeitsunfähigkeitsbescheinigung dar, dessen Projektverlauf evaluiert wurde, um aus den Herausforderungen zu lernen.