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Development of a ship performance model for power estimation of inland waterway vessels
Get PDFA ship performance model is an important factor in energy-efficient navigation. It formulates a speed–power relationship that can be used to adjust the engine loads for dynamic energy optimisation. However, currently available models have been developed for sea-going vessels, where the environmental conditions are significantly different from those experienced on inland waterways. Inland waterway shipping has great potential to become a mode of transport that can both improve safety and reduce emissions. Therefore, this paper presents the development of an energy performance model specifically for inland waterway vessels (IWVs). The holistic ship energy system model is based on empirical methods, from resistance to engine performance prediction, established in a modular code architecture. The resistance and propulsion prediction in confined waterways are captured by a newly developed method, considering a superposing of shallow water and bank effect. Verification against model tests and high-fidelity simulations indicate that the selected empirical methods achieved good accuracy for predicting ship performance. The resistance prediction error was 5.2% for single vessels and 8% for pusher-barge convoys based on empirical methods. The results of a case study investigating the performance of a self-propelled vessel under dynamic waterway data, indicate that the developed model could be used for onboard power monitoring and energy optimisation during operation
Evaluation of Out-of-Distribution Detection Performance on Autonomous Driving Datasets
No full textSafety measures need to be systemically investigated to what extent they evaluate the intended performance of Deep Neural Networks (DNNs) for critical applications. Due to a lack of verification methods for high-dimensional DNNs, a trade-off is needed between accepted performance and handling of out-of-distribution (OOD) samples.This work evaluates rejecting outputs from semantic segmentation DNNs by applying a Mahalanobis distance (MD) based on the most probable class-conditional Gaussian distribution for the predicted class as an OOD score. The evaluation follows three DNNs trained on the Cityscapes dataset and tested on four automotive datasets and finds that classification risk can drastically be reduced at the cost of pixel coverage, even when applied on unseen datasets. The applicability of our findings will support legitimizing safety measures and motivate their usage when arguing for safe usage of DNNs in automotive perception
Investigation of dark count rate in NbRe microstrips for single photon detection
Get PDFSuperconducting microstrip single photon detectors (SMSPDs) received great interest since they are expected to combine the excellent performance of superconducting nanostrip single photon detectors with the possibility to cover large active areas using low-cost fabrication techniques. In this work, we fabricated SMSPDs based on NbRe to investigate the role of vortices in the dark counts events in this innovative material and in devices with micrometer size. We realized devices with different layouts, namely single microstrips and pairs of parallel microstrips. The energy barriers related to the motion of single vortices or vortex-antivortex pairs, responsible of detection events, have been determined and compared with the ones of similar devices based on different materials, such as MoSi, WSi and NbN. The analysis confirms the high potential of NbRe for the realization of superconducting single photon detectors with large areas
Bacterial Cellulose Aerogels Derived from Pineapple Peel Waste for the Adsorption of Dyes
Get PDFValorization of pineapple peel waste is an attractive research topic because of the huge quantities of this byproduct generated from pineapple processing industries. In this study, the extract from pineapple waste was collected to produce a hydrogel-like form containing bacterial cellulose fibers with a three-dimensional structure and nanoscale diameter by the Acetobacter xylinum fermentation process. The bacterial cellulose suspension was subsequently activated by freeze-drying, affording lightweight aerogels as potential adsorbents in wastewater treatment, in particular the adsorptive removal of organic dyes. Intensive tests were carried out with the adsorption of methylene blue, a typical cationic dye, to investigate the influence of adsorption conditions (temperature, pH, initial dye concentration, time, and experiment scale) and aerogel-preparation parameters (grinding time and bacterial cellulose concentration). The bacterial cellulose-based aerogels exhibited high adsorption capacity not only for methylene blue but also for other cationic dyes, including malachite green, rhodamine B, and crystal violet (28-49 mg/g). However, its activity was limited for most of the anionic dyes, such as methyl orange, sunset yellow, and quinoline yellow, due to the repulsion of these anionic dyes with the aerogel surface, except for the case of congo red. It is also an anionic dye but has two amine groups providing a strong interaction with the hydroxyl group of the aerogel via hydrogen bonding. Indeed, the aerogel has a substantially large congo red-trapping capacity of 101 mg/g. Notably, the adsorption process exhibited similar performances, upscaling the solution volume to 50 times. The utilization of abundant agricultural waste in the simple aerogel preparation to produce a highly efficient and biodegradable adsorbent is the highlight of this work
Euler–Maruyama approximations of the stochastic heat equation on the sphere
No full textThe stochastic heat equation on the sphere driven by additive isotropic Wiener noise is approximated by a spectral method in space and forward and backward Euler–Maruyama schemes in time. The spectral approximation is based on a truncation of the series expansion with respect to the spherical harmonic functions. Optimal strong convergence rates for a given regularity of the initial condition and driving noise are derived for the Euler–Maruyama methods. Besides strong convergence, convergence of the expectation and second moment is shown, where the approximation of the second moment converges with twice the strong rate. Numerical simulations confirm the theoretical results
Tandem duplication parameterized by the length difference
No full textA tandem duplication in a string takes a substring and inserts another copy of it right beside it. Given two strings, we want to find a shortest sequence of tandem duplications that transform the shorter string into the longer one, or recognize that no such sequence exists. The problem, in particular with short tandem duplications, is of interest in genomics, and a number of complexity results are known. First we improve a recent simple XP algorithm. However, our main technical contributions are an FPT algorithm, where the parameter is the difference of lengths of the two given strings, and a polynomial kernel
Modelling Braking and Steering Avoidance Maneuvers for Micromobility
No full textRecent advancements in technology make it possible for advanced driving assistance systems (ADAS) to recognize micromobility vehicles (MMV) and include them in their threat assessment. However, today we lack the rider-vehicle models which are of great importance in understanding the interconnection between the MMV and its rider. These models may help ADAS predict micromobility kinematics and provide accurate threat assessments, especially when avoidance maneuvers from micromobility must be considered. In this study, we modelled avoidance maneuvers from micromobility vehicles to support ADAS threat assessment. We compared traditional bicycles (with and without assistance) with e-scooters (a small personal scooter and a large scooter) in a field test, where 36 participants avoided a stationary obstacle by either braking or steering. Kinematic data such as longitudinal and latera speed, acceleration, jerk and steering angle and rate were collected and analyzed
Life Cycle Cost and Life Cycle Assessment of Composite Bridge with Flat and Corrugated Webs
Get PDFTo satisfy the sustainability criteria, a bridge design must be economically viable during its entire service life with a minimal impact on the environment. While stainless steel is known for its excellent life cycle performance, its high cost prevents it from being used in bridges to a larger extent. This study evaluates a new design solution that takes advantage of using corrugated web in bridge girders to overcome this issue. Three design concepts are evaluated for a three-span case-study bridge. These include a bridge with carbon steel flat web, stainless steel flat web, and stainless-steel corrugated web girders. Each design is optimized using a genetic algorithm. The three optimal solutions are then evaluated in terms of investment costs, life cycle costs (LCC) and life cycle impact. The results show that the investment costs in a flat web girder bridge increase by 27% when stainless steel is used instead of C-Mn (carbon) steel. However, this increase is only 10% when corrugated web girders are used. On the other hand, the LCC savings increase from 6% to 18% for corrugated web girders. Finally, the use of corrugated web in stainless steel leads to a reduction in the climate impacts of up to 32% compared to carbon steel for the studied bridge
FATIGUE RESISTANCE OF ADHESIVE BONDED CONNECTIONS WITH AND WITHOUT INTERNAL STEEL PLATES IN LARGE TIMBER STRUCTURES
No full textA modular wooden wind turbine tower has been developed by the Swedish company Modvion AB, where the prefabricated modular elements are connected by glued timber-timber edge joints and by hybrid timber joints with bonded-in perforated steel plates. The application of wood-based products in such a demanding application and high-performance structure is challenging and a variety of questions had to be solved to ensure a reliable performance. The fatigue performance of the adhesive bonded connections has been evaluated in a research project and is presented in this paper. Test specimens of the fatigue resistance of the adhesive and the bond line has been developed. Different stress ratios with alternating loads and high numbers of load cycles have been tested. The results of the tests are presented in this paper
Robust and tunable coreless vortices and fractional vortices in chiral d-wave superconductors
Get PDFChiral Formula Presented-wave superconductivity has recently been proposed in a wide range of materials based on both experiment and theoretical studies. Chiral superconductors host a finite Chern number set by the winding of the superconducting order parameter and associated topologically protected chiral edge modes. However, the chiral edge currents and orbital angular momentum (OAM) generated by the edge modes are not topologically protected and another, more robust, experimental probe is therefore needed to facilitate experimental verification of chiral Formula Presented-wave superconductors. We have recently shown the appearance of quadruply quantized coreless vortices (CVs) in chiral Formula Presented-wave superconductors, consisting of a closed domain wall decorated with eight fractional vortices, and generating a smoking-gun signature of the Chern number, chirality, and the superconducting pairing symmetry [ P. Holmvall and A. M. Black-Schaffer , Phys. Rev. B 108, L100506 (2023)10.1103/PhysRevB.108.L100506 ]. Specifically, the CV spontaneously breaks axial symmetry for parallel chirality and vorticity, with a signature appearing directly in the local density of states (LDOS) measurable with scanning tunneling spectroscopy (STS). In this paper, we first demonstrate a strong tunability of the CV size and shape directly reflected in the LDOS and then show that the LDOS signature is robust in the presence of regular Abrikosov vortices, strong confinement, system and normal-state anisotropy, different Fermi surfaces (FSs), nondegenerate order parameters, and even nonmagnetic impurities. In conclusion, our paper establishes CVs as a tunable and robust signature of chiral Formula Presented-wave superconductivity