263134 research outputs found
Sort by
Schatting van de bewegingstoestand van het voertuig en de bandenkrachten - Op weg naar praktische implementatie: verkenning van de belangrijkste beïnvloedende factoren
No full textOne of the central goals of legislative bodies around the world related to road traffic safety is the continued reduction of road fatalities. Against this background, active vehicle safety and driver assistance systems have been identified as key enablers for safer road traffic. These systems greatly benefit from information on the vehicle motion states and the forces acting in the tyre-road contact. These quantities of interest are decisive for the dynamic behaviour of road vehicles. For series-production vehicles, the direct measurement of these quantities using sensors is typically not viable for cost, robustness, and practical installation reasons. Seeking for alternatives, numerous research efforts continue to focus on methods for model-based estimation of the quantities of interest.
To date, the vast majority of model-based estimation approaches in vehicle dynamics use very simple models which come with limitations in terms of the quality of the provided quantities of interest and in terms of considering fundamental vehicle dynamics effects. An example is the linear single-track model, which only provides per-axle lateral forces instead of individual tyre lateral forces. Instead of enriching the single-track model with numerical representations of additional dynamics, this thesis first investigates the feasibility of using a more integrated estimation approach based on a considerably more complex four-wheel vehicle model including suspension kinematics. This approach is able to provide similar levels of accuracy as the single-track model variant, but exceeds it in terms of the availability of relevant quantities of interest. Subsequently, the implications of such an approach on the robustness of the estimation results as well as on the estimator development process are analysed. On the one hand, the influence of various factors and their perturbations is examined, on the other hand, effects originating from different estimator configuration and application cases are explored. Throughout this thesis, the road is assumed to be flat for all considered estimator variants.
The aforementioned investigations are enabled by the development of a scalable, modular estimation framework which allows for the consistent assessment and comparison of varying estimator configurations and applications, as well as factor perturbations. One of the cornerstones for both the estimator robustness analysis as well as the probe of the multi-dimensional estimator application and configuration space is the use of experimental measurement data wherever possible. In addition to two sets of data available from past test campaigns, another data set is recorded with a custom research validation and demonstration vehicle platform specifically developed for research validation purposes.
The detailed robustness analysis of the estimation results of the simple and the complex vehicle models against perturbations relies on sensitivity analysis. A key result is the level of importance of the influencing factors for different estimator applications and configurations, which are distinguished by the complexity of the vehicle model used, the test vehicle considered, and the driving manoeuvre performed. It can be concluded that the estimation approach based on the four-wheel vehicle model including suspension kinematics in general poses much higher requirements towards parameter accuracy and estimator covariance tuning compared to the variant employing the single-track model. A trend was identified suggesting a decrease in estimator robustness for increasing vehicle platform stiffness - specifically when employing the complex model. The influence of the dynamic excitation of the driving manoeuvre was found to be negligible. Depending on the required accuracy of the vehicle model parameters and estimator covariance settings, those with high relevance can be prioritized.
Resulting from the estimator application and configuration space probe, the influence of key determinants on the estimation results accuracy and the practical estimator development process is clarified. It was found that the influence of the type of performed driving manoeuvre and its level of dynamic lateral excitation on the estimation results accuracy typically exceeds the respective influence of both the vehicle model complexity as well as the overall test vehicle platform stiffness. Thereby, decisions with respect to which development aspects are to be prioritised for an optimal trade-off between estimation results accuracy and development efforts for specific targeted estimator applications are supported.status: Publishe
Impact op de Betrouwbaarheid van Software door Implementatie van Selectieve Beschermingstechnieken op Laag-Niveau Code
No full textMicrocontrollers are the heart of embedded systems. Thanks to developments in technological downscaling, microcontroller manufacturing has progressed significantly in recent years. As a result, embedded systems' performance and component density have increased considerably, allowing more functionality to be packed into smaller chips. This was made possible by lowering the supply voltage and shrinking transistor size, but these developments do come at the cost of increasing microcontrollers' vulnerability to the bit flips phenomena. This phenomenon causes a bit to change from its intended state (logical 0 to 1 or 1 to 0). Without detection mechanisms in place, these bit flips may result in silent errors, specifically data flow errors or control flow errors, leading to unpredictable and undesirable behavior in the system and ultimately impacting the reliability of embedded systems.
While many previous studies have focused on developing Software-Implemented Hardware Fault Tolerance (SIHFT) techniques, the results indicate that these software-based methods are often impractical to implement in real-world cases. Additionally, in cases where they are implementable, they can lead to excessive overhead. Therefore, this work takes a novel approach to addressing this problem. Instead of fully protecting the system, throughout this research, the application's behavior was analyzed at runtime using two criteria: (1) selecting components based on their memory interaction, and (2) selecting components based on their fault injection vulnerability. This analysis enables the ranking of components based on their vulnerability, focusing only on those most at risk. After identifying the vulnerable components, Selective Software-Implemented Fault Tolerance - Recovery (S-SWIFT-R), a well-known software protection method against bit flips, is applied to protect the selected components. These additional protection codes are directly included at the assembly level in the low-level code of the program. Extending our compiler plugin, which automatically implements software-based protection algorithms, to include S-SWIFT-R makes adopting this technique more convenient. This tool is available as a public GNU Compiler Collection (GCC) plugin under a GNU General Public License (GPL) license model.
The impact of the proposed approach was evaluated through academic and two industrial case studies. These industrial case studies are: 1) the autonomous mobile robots (AMR) of the Ultimate Factory lab, and 2) a small-scale factory. The first case study was conducted in the Ultimate Factory Lab, which is equipped with AMRs and various stations. The first significant step involved developing four test cases that represented the primary behaviors of the AMRs in the lab. To evaluate these test cases, throughout this research, a fault injection mechanism was implemented to introduce bit flips, and a monitoring system was established to assess performance under fault conditions. The second case study is on a small-scale factory including three stations: the testing station, the distribution station, and the sorting station. Each station is controlled by its microcontroller. The impact of fault injection is evaluated on them by introducing bit flips in each station and then applying the S-SWIFT-R protection technique.
The results demonstrated that the selective approach significantly reduced system overhead and the number of components that needed to be reserved compared to a full implementation. However, there was some impact on the application's reliability. Given that S-SWIFT-R is a selective methodology the number of protected components was gradually increased, allowing for the assessment of improvements at each stage and identification of the optimal balance between overhead and reliability. These studies demonstrate the effectiveness and impact of the proposed approach.
Finally, in this research, in collaboration with other researchers, the register analysis framework was used to reduce the overhead of DETECTOR, a SIHFT method. This led to the development of S-DETECTOR, the selective version of DETECTOR, which has a notably beneficial effect on reducing the associated overheads.status: Publishe
Labor Market Participation, Marriage and Individual Welfare
No full textWe empirically analyze the impact of labor market participation on individual welfare, focusing on material consumption distribution within households.
We model household allocations of consumption and time, considering individual preferences and intrahousehold decision processes. Utilizing a revealed
preference, nonparametric structural methodology, we assess individual welfare in multi-person households, accounting for consumption inequality and
economies of scale. Using US Panel Study of Income Dynamics (PSID) data,
we identify the effects of a measure of unemployment and education on welfare, revealing significant heterogeneity influenced by spousal education and
employment status, with employment effects predominating.status: Published onlin
Physical returns in a pricing world: Towards forward-looking market risk measures
No full textMost risk measures are calculated using the physical measure, P. This measure is commonly estimated using historical data, often under the implicit assumption that realized returns are homogeneous in time. Since risk measures are used to assess future risks, they should consider sources of forward-looking information as well. One natural source of this information is option data since it reflects the market's perception of future returns under the pricing measure Q. Several methodologies incorporating option data have been proposed in the literature. In this paper, we build on the established tilting framework that links P and Q, and propose a refined implementation that preserves the structure of the pricing kernel.
One of the key contributions is the introduction of the Adjusted Tilted Sato Bilateral Gamma (ATSBG) process, a new model that fits the S&P 500 option surface competitively relative to standard benchmarks. Within the adapted tilting framework, we use this process to infer an estimate of the physical distribution from option data and evaluate its performance across multiple return horizons. A second key contribution is that our results suggest that the physical measure can be reasonably well extracted from option surfaces, and that our model performs comparably to, and in some respects better than, existing models based on historical data.
Additionally, we provide a theoretical reformulation of the tilting framework within the setting of mixture models, offering structural insights into the relation between
and P and Q.status: Published onlin
Interaction Assessment of Converter Interfaced Power Systems Using Proximal Eigenvalue Displacement Approach
No full textstatus: Published onlin
Origin of the strong metal-support interaction in Pd/TiO2
No full textsponsorship: A.B. acknowledges the funding of Swiss National Science Foundation (SNSF) Starting Grant No. TMSGI2_226131. We thank ReMade@ARIE by the European Union as part of the Horizon Europe call HORIZON-INFRA-2021-SERV-01 under grant agreement number 101058414 and co-funded by UK Research and Innovation (UKRI) under the UK government's Horizon Europe funding guarantee (grant number 10039728) and by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 22.00187 for the access to the HR-STEM measurements (ERC, Julich, Germany) and XAS measurements at SuperXAS beamline of Swiss Light Source (PSI, Villigen, Switzerland) . Views and opinions expressed are however those of the author (s) only and do not necessarily reflect those of the European Union or the UK Science and Technology Facilities Council or the Swiss State Secretariat for Education, Research and Innovation (SERI) . Neither the European Union nor the granting authorities can be held responsible for them. We acknowledge ALBA synchrotron for granting the beamline at NOTOS beamline, and its staff for professional and friendly support. Eleonora Vottero and Guglielmo Peruzzi are acknowledged for contributing to acquiring preliminary IR spectroscopy data. We are indebted to Marc Eduard Usteri for ICP-OES and Chiara Pischetola for TPO measurements. (Swiss National Science Foundation (SNSF)|TMSGI2_226131, European Union|HORIZON-INFRA-2021-SERV-01, European Union|101058414, UK Research and Innovation (UKRI) under the UK government's Horizon Europe|10039728, Swiss State Secretariat for Education, Research and Innovation (SERI)|22.00187)status: Accepte
Imaging in gynecological disease (29): clinical and ultrasound features of primary ovarian immature teratoma
No full textOBJECTIVE: To describe the clinical and ultrasound characteristics at the time of diagnosis of primary ovarian immature teratoma with no other germ cell tumor components described on histopathology. METHODS: This was a retrospective study of women with a histological diagnosis of primary ovarian immature teratoma who had undergone a preoperative ultrasound examination between 1998 and 2024. Cases were identified from the databases of 17 contributing ultrasound centers and the International Ovarian Tumor Analysis (IOTA) database. The descriptions of the ultrasound images of the tumors made by the original ultrasound examiners using IOTA terminology were reported. In addition, grayscale and color or power Doppler ultrasound images or videoclips were retrieved for all tumors. Two independent ultrasound examiners reviewed the retrieved material and searched for specific ultrasound characteristics of immature teratomas using pattern recognition. We present their agreed description of the tumors. RESULTS: In total, 64 patients with ovarian immature teratoma were included, of which 38 (59.4%) were obtained from the IOTA database (IOTA studies phase 1, 1b, 2, 3, 5 and 7). The median age of the patients at diagnosis was 24.5 (interquartile range (IQR), 18.8-31.0; range, 12-50) years. The most common presenting symptoms were abdominal or pelvic pain (38/60, 63.3%) and abdominal swelling (30/60, 50.0%). All immature teratomas were unilateral. The median largest diameter of the tumor was 149.5 (IQR, 125.0-183.8; range, 27-400) mm. Using IOTA terminology, most tumors were described as multilocular-solid (32/64, 50.0%) or solid lesions (22/64, 34.4%). When present, the solid component had a median largest diameter of 98.5 (IQR, 59.8-146.8; range 6-400) mm. Most masses showed minimal (19/63, 30.2%) or moderate (35/63, 55.6%) vascularization on color or power Doppler ultrasound examination. Using pattern recognition, the most typical ultrasound feature was heterogeneous, bizarre echogenicity of the solid components, with hyperechogenic areas, cystic spaces and acoustic shadows. This feature, which we consider pathognomonic, was present in 48/57 (84.2%) immature teratomas in which the solid components were adequately assessable. CONCLUSIONS: The typical ultrasound appearance of an ovarian immature teratoma is a large unilateral adnexal mass with large solid components that is poorly or moderately vascularized. The pathognomonic feature is heterogeneous echogenicity of the solid components with hyperechogenic areas, cystic spaces and acoustic shadows. Preoperative suspicion of immature teratoma can guide treatment, such as offering fertility-sparing surgery. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.status: Published onlin
Tight Convergence Rates in Gradient Mapping for the Difference-of-Convex Algorithm
No full textWe establish new theoretical convergence guarantees for the difference-of-convex algorithm (DCA), where the second function is allowed to be weakly-convex, measuring progress via composite gradient mapping. Based on a tight analysis of two iterations of DCA, we identify six parameter regimes leading to sublinear convergence rates toward critical points and establish those rates by proving adapted descent lemmas.
We recover existing rates for the standard difference-of-convex decompositions of nonconvex-nonconcave functions, while for all other curvature settings our results are new, complementing recently obtained rates on the gradient residual.
Three of our sublinear rates are tight for any number of DCA iterations, while for the other three regimes we conjecture exact rates, using insights from the tight analysis of gradient descent and numerical validation using the performance estimation methodology.
Finally, we show how the equivalence between proximal gradient descent (PGD) and DCA allows the derivation of exact
PGD rates for any constant stepsize.status: Published onlin
