Wendelstein 7-X is a highly optimized stellarator that went into operation in 2015. With a 30 cubic meter volume, a superconducting coil system operating at 2.5 T, and steady-state heating capability ...of eventually up to 10 MW, it was built to demonstrate the benefits of optimized stellarators at parameters approaching those of a fusion power plant. We report here on the first results with the test divertor installed, during the second operation phase, which was performed in the second half of 2017. Operation with a divertor, and the addition of several new fueling systems, allowed higher density operation in hydrogen as well as helium. The effects that higher density operation had on both divertor operation and global confinement will be described. In particular, at high densities detachment was observed, and the highest fusion triple product for a stellarator was achieved.
The position of on-body motion sensors plays an important role in human activity recognition. Most often, mobile phone sensors at the trouser pocket or an equivalent position are used for this ...purpose. However, this position is not suitable for recognizing activities that involve hand gestures, such as smoking, eating, drinking coffee and giving a talk. To recognize such activities, wrist-worn motion sensors are used. However, these two positions are mainly used in isolation. To use richer context information, we evaluate three motion sensors (accelerometer, gyroscope and linear acceleration sensor) at both wrist and pocket positions. Using three classifiers, we show that the combination of these two positions outperforms the wrist position alone, mainly at smaller segmentation windows. Another problem is that less-repetitive activities, such as smoking, eating, giving a talk and drinking coffee, cannot be recognized easily at smaller segmentation windows unlike repetitive activities, like walking, jogging and biking. For this purpose, we evaluate the effect of seven window sizes (2-30 s) on thirteen activities and show how increasing window size affects these various activities in different ways. We also propose various optimizations to further improve the recognition of these activities. For reproducibility, we make our dataset publicly available.
Physical activity recognition using embedded sensors has enabled many context-aware applications in different areas, such as healthcare. Initially, one or more dedicated wearable sensors were used ...for such applications. However, recently, many researchers started using mobile phones for this purpose, since these ubiquitous devices are equipped with various sensors, ranging from accelerometers to magnetic field sensors. In most of the current studies, sensor data collected for activity recognition are analyzed offline using machine learning tools. However, there is now a trend towards implementing activity recognition systems on these devices in an online manner, since modern mobile phones have become more powerful in terms of available resources, such as CPU, memory and battery. The research on offline activity recognition has been reviewed in several earlier studies in detail. However, work done on online activity recognition is still in its infancy and is yet to be reviewed. In this paper, we review the studies done so far that implement activity recognition systems on mobile phones and use only their on-board sensors. We discuss various aspects of these studies. Moreover, we discuss their limitations and present various recommendations for future research.
For physical activity recognition, smartphone sensors, such as an accelerometer and a gyroscope, are being utilized in many research studies. So far, particularly, the accelerometer has been ...extensively studied. In a few recent studies, a combination of a gyroscope, a magnetometer (in a supporting role) and an accelerometer (in a lead role) has been used with the aim to improve the recognition performance. How and when are various motion sensors, which are available on a smartphone, best used for better recognition performance, either individually or in combination? This is yet to be explored. In order to investigate this question, in this paper, we explore how these various motion sensors behave in different situations in the activity recognition process. For this purpose, we designed a data collection experiment where ten participants performed seven different activities carrying smart phones at different positions. Based on the analysis of this data set, we show that these sensors, except the magnetometer, are each capable of taking the lead roles individually, depending on the type of activity being recognized, the body position, the used data features and the classification method employed (personalized or generalized). We also show that their combination only improves the overall recognition performance when their individual performances are not very high, so that there is room for performance improvement. We have made our data set and our data collection application publicly available, thereby making our experiments reproducible.
In this paper, we describe and validate the EquiMoves system, which aims to support equine veterinarians in assessing lameness and gait performance in horses. The system works by capturing horse ...motion from up to eight synchronized wireless inertial measurement units. It can be used in various equine gait modes, and analyzes both upper-body and limb movements. The validation against an optical motion capture system is based on a Bland-Altman analysis that illustrates the agreement between the two systems. The sagittal kinematic results (protraction, retraction, and sagittal range of motion) show limits of agreement of ± 2.3 degrees and an absolute bias of 0.3 degrees in the worst case. The coronal kinematic results (adduction, abduction, and coronal range of motion) show limits of agreement of - 8.8 and 8.1 degrees, and an absolute bias of 0.4 degrees in the worst case. The worse coronal kinematic results are most likely caused by the optical system setup (depth perception difficulty and suboptimal marker placement). The upper-body symmetry results show no significant bias in the agreement between the two systems; in most cases, the agreement is within ±5 mm. On a trial-level basis, the limits of agreement for withers and sacrum are within ±2 mm, meaning that the system can properly quantify motion asymmetry. Overall, the bias for all symmetry-related results is less than 1 mm, which is important for reproducibility and further comparison to other systems.
The Paris Agreement determined to limit global warming to below two degrees. National governments are now confronted with the challenge of taking action for climate protection. For Germany, this ...poses a major challenge, as the imminent phaseout of low-emission nuclear energy additionally increases the pressure to quickly advance the deployment of renewable energies. At the same time, their low energy density and the resulting high land requirements lead to severe conflicts in land use. The situation is aggravated by the fact that the diversity of societal actors leads to a diversity of energy strategies, which differ in terms of impacts on land use. We therefore want to analyse the impending restructuration of energy supply and the associated land use conflicts. We model potential scenarios of energy landscapes that can be derived from the two-degree target on the basis of Geographic Information Systems, by modifying the political guidelines and planning laws for the deployment of renewable energies. The analyses show that carbon-neutrality is attainable in principle. However, the spatial patterns of renewable energies differ considerably depending on the given legal framework. It also comes to show that land use policy must take greater account of the perspectives of those social groups that are confronted with the installation of renewable energies in the immediate vicinity of their own living environment.
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•The energy transition leads to considerable changes in land use patterns.•The study revealed that it is possible to realize a carbon-neutral regional energy system by 2050.•The existing legal framework for nature conservation offers sufficient spatial options for the energy transition.•The weighting of site factors must consider current power structures.•A low-conflict regional climate protection strategy should be based on public participation.
Assembly of the superconducting stellarator Wendelstein 7-X is well advanced, and commissioning of the device is being prepared. A first draft of the commissioning tasks has been developed and will ...be discussed in this paper.
The Wendelstein 7-X stellarator (W7-X), one of the largest stellarator fusion experiments, is in operation since 2015 at the Max Planck Institute for Plasma Physics (IPP) in Greifswald. W7-X has ...reached the final status in 2022 with actively cooled in-vessel components. The superconducting magnet system consist of 50 non-planar and 20 planar coils. The superconducting coils as well as the connections in between are made of the same NbTi cable-in-conduit conductor (CICC) type. Two plasma breakdowns in the past have induced voltages into the non-planar coils, which triggered the quench detection (QD) system and activated the safety system with a fast discharge of the magnet system. Plasma operation creates toroidal and poloidal currents; a plasma breakdown can change the plasma currents within 100 ms. Especially fast poloidal current changes are able to induce voltages into the superconducting coils. Using the adjustment capabilities of the QD system, new parameter sets for threshold values and shunted capacitor settings were deduced. These parameters prolongs the time until the start of the magnet discharge, which increases the hot spot temperature in the CICC in case of a quench. Thermo-hydraulic calculations with the program THEA from Cryosoft were performed to verify that the 130 K limit for the hot spot temperature is kept with the new QD parameter sets. The analysis were performed by the West Pomeranian University of Technology (ZUT) and by the Henryk Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences in Poland.
Our central target is to show that capitalism is not only much more robust to crises than presumed by its critics, but also features promising capabilities with regard to solving the environmental ...crisis. To elaborate this thesis, we analyse how far capitalism can survive given the end of fossil energy carriers and may maintain its productivity under the preconditions of a regenerative energy system. In a further step, we demonstrate that crises may actually provide the prerequisites of the economy's transformation towards sustainability. We argue that especially competitive capitalism as analysed by Schumpeter offers excellent preconditions for generating environmental innovations. However, we will also point out the numerous social problems of green infrastructure projects. In the last section, we assume that markets alone will not suffice to concertedly solve the global environmental crisis. Here, political action is needed that pools societal forces with regard to the ecological challenges, hence specifically promoting desirable innovations. The usefulness of state measures is to be judged in correlation to the respective specific national political and economic contexts. A generalised opposition to capitalistic social orders disregards the complexity of these contexts and is at danger of omitting decisive determinants of crisis management.
•critical analysis of the interrelation between fossil fuels and capitalism•possibilities of 'space-time compression' within post-fossil societies•capabilities of a green capitalism on the basis of renewable energies•social problems of green infrastructure projects•impact of political contexts on the transformation of energy systems
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