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Magnetocaloric effect in M5XB2 family compounds
No full textThe purpose of work presented in this thesis is to investigate whether M5XB2 (M = Fe, Mn,V, Cr and X = Si, P) material system has potential as a room-temperature magnetocaloric application material by studying its crystal and magnetic structure, and magnetocaloric properties.RST/Fundamental Aspects of Materials and Energ
Unveiling the catalytic potential of two-dimensional boron nitride in lithium–sulfur batteries
No full textLithium–sulfur (Li–S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N2). The inherent conductivity of o-B2N2 mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N2 surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N2 surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N2 surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N2 as a host cathode material for Li–S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li–S batteries.Team Poulumi De
Biocompatible optical physically unclonable function hydrogel microparticles for on-dose authentication
No full textOn-dose authentication (ODA) enhances security by incorporating customized molecular or micro-tags into each pill, preventing counterfeit products in genuine packages. ODA's security relies on tag non-replication and non-reverse engineering. Combining ODA with graphical Physical Unclonable Functions (PUF) promises maximum security. PUF uses intrinsic micro or nanoscale randomness as a unique ‘fingerprint’. However, current graphical PUFs have limitations like specific illumination requirements and the use of toxic materials, restricting their use in pharmaceuticals. In this study, we propose a novel approach called on-dose PUF. This method involves embedding microspheres randomly within micro biocompatible hydrogel particles. We showcase two distinct types of such on-dose PUFs. The first type utilizes randomly distributed superparamagnetic colloids (SPC) of identical diameters, while the second type utilizes vortexed sunflower oil drops of various diameters. The diameter and coordinates of the microspheres serve as input for generating cryptographic keys. A universal circle identification and binning program is used for extracting this information. One advantage of this approach is that it enables imaging using white light illumination and low-magnification microscopy, as color and signal intensity information are not crucial. This method enables patients to verify their medication by using their mobile phones from home. To assess the performance of the proposed on-dose PUF, we conducted canonical investigations on the single-diameter system. This system can only generate one layer of cryptographic keys, making it potentially more vulnerable than the multiple-diameter system. However, the single-diameter system successfully passed NIST Statistical tests and exhibited sufficient randomness, ideal bit uniformity, Hamming distance, and device uniqueness. Furthermore, we found that the encoding capacity of the single-diameter system was 9.2×1018, providing ample labeling potential.Engineering ThermodynamicsEnergy TechnologyComplex Fluid Processin
Design of the new structure and capabilities of LADM edition II including 3D aspects
No full textThe decision to refine the existing content and to extend the scope of Edition I of the ISO 19152:2012 Land Administration Domain Model (LADM) is a response to requests from the international Land Administration (LA) community. This response has to be formally organised in accordance with ISO guidelines. This begins with gathering feedback from ISO/TC 211 Member States on the need for updated and enhanced capabilities of the LADM. In addition, several proposals have been made to extend the scope of the LADM Edition I. After analysing the feedback received, it was proposed to develop the LADM Edition II as a multi-part standard: Part 1 — Generic conceptual model, Part 2 — Land registration, Part 3 — Marine georegulation, Part 4 — Valuation information, Part 5 — Spatial plan information and Part 6 — Implementation aspects. In other words, Edition I focuses on land tenure, while the design and development of Edition II is based on the inclusion of rights, restrictions and responsibilities (RRRs) concerning marine georegulation, valuation information, spatial plan information as well as LADM implementation. 3D representations are relevant for all parts.This paper focuses on the design of the new structure of the second edition of the LADM and on the (operational) capabilities of this new edition in relation to the LA issues in Parts (standards addressing a specific part of the scope) and Packages (groups of conceptually close classes), with a particular attention to the requirements and design related decisions taken in the revision process. The parts 1, 2, 4 and 5 are the parts in which the authors are currently involved. Part 1 will be a high-level umbrella standard; Part 2 is largely based on LADM Edition I and focuses on land registration, with an enhanced support on the surveying functionality, including new subclasses of spatial unit, and extended 3D spatial profiles. Part 3 harmonises the description of RRRs and aligns land concepts with marine aspects from the marine domain based on the International Hydrographic Organisation (IHO) S121 Maritime Limits and Boundaries Product Specification. Part 4 deals with valuation information used and produced in the context of land administration, while Part 5 deals with spatial planning information and includes the planned use of the land (zoning), resulting in RRRs. Lastly, Part 6 is planned to be about implementation of the LADM and will be developed in close collaboration with the Open Geospatial Consortium (OGC).Digital Technologie
An in-depth comparison of linear and non-linear joint embedding methods for bulk and single-cell multi-omics
No full textMulti-omic analyses are necessary to understand the complex biological processes taking place at the tissue and cell level, but also to make reliable predictions about, for example, disease outcome. Several linear methods exist that create a joint embedding using paired information per sample, but recently there has been a rise in the popularity of neural architectures that embed paired -omics into the same non-linear manifold. This work describes a head-to-head comparison of linear and non-linear joint embedding methods using both bulk and single-cell multi-modal datasets. We found that non-linear methods have a clear advantage with respect to linear ones for missing modality imputation. Performance comparisons in the downstream tasks of survival analysis for bulk tumor data and cell type classification for single-cell data lead to the following insights: First, concatenating the principal components of each modality is a competitive baseline and hard to beat if all modalities are available at test time. However, if we only have one modality available at test time, training a predictive model on the joint space of that modality can lead to performance improvements with respect to just using the unimodal principal components. Second, -omic profiles imputed by neural joint embedding methods are realistic enough to be used by a classifier trained on real data with limited performance drops. Taken together, our comparisons give hints to which joint embedding to use for which downstream task. Overall, product-of-experts performed well in most tasks and was reasonably fast, while early integration (concatenation) of modalities did quite poorly.Pattern Recognition and Bioinformatic
Energy-conserving hyper-reduction and temporal localization for reduced order models of the incompressible Navier-Stokes equations
No full textA novel hyper-reduction method is proposed that conserves kinetic energy and momentum for reduced order models of the incompressible Navier-Stokes equations. The main advantage of conservation of kinetic energy is that it endows the hyper-reduced order model (hROM) with a nonlinear stability property. The new method poses the discrete empirical interpolation method (DEIM) as a minimization problem and subsequently imposes constraints to conserve kinetic energy. Two methods are proposed to improve the robustness of the new method against error accumulation: oversampling and Mahalanobis regularization. Mahalanobis regularization has the benefit of not requiring additional measurement points. Furthermore, a novel method is proposed to perform energy- and momentum-conserving temporal localization with the principle interval decomposition: new interface conditions are derived such that energy and momentum are conserved for a full time-integration instead of only during separate intervals. The performance of the new energy- and momentum-conserving hyper-reduction methods and the energy- and momentum-conserving temporal localization method is analysed using three convection-dominated test cases; a shear-layer roll-up, two-dimensional homogeneous isotropic turbulence and a time-periodic inviscid flow consisting of a vortex in a uniform background flow. Our main finding is that energy conservation in combination with oversampling or regularization leads to a robust method with excellent long time stability properties. When any of these two ingredients is missing, accuracy and/or stability is significantly impaired.Fluid Mechanic
Predictive simulations identify potential neuromuscular contributors to idiopathic toe walking
No full textBackground: Most cases of toe walking in children are idiopathic. We used pathology-specific neuromusculoskeletal predictive simulations to identify potential underlying neural and muscular mechanisms contributing to idiopathic toe walking. Methods: A musculotendon contracture was added to the ankle plantarflexors of a generic musculoskeletal model to represent a pathology-specific contracture model, matching the reduced ankle dorsiflexion range-of-motion in a cohort of children with idiopathic toe walking. This model was employed in a forward dynamic simulation controlled by reflexes and supraspinal drive, governed by a multi-objective cost function to predict gait patterns with the contracture model. We validated the predicted gait using experimental gait data from children with idiopathic toe walking with ankle contracture, by calculating the root mean square errors averaged over all biomechanical variables. Findings: A predictive simulation with the pathology-specific model with contracture approached experimental ITW data (root mean square error = 1.37SD). Gastrocnemius activation was doubled from typical gait simulations, but lacked a peak in early stance as present in electromyography. This synthesised idiopathic toe walking was more costly for all cost function criteria than typical gait simulation. Also, it employed a different neural control strategy, with increased length- and velocity-based reflex gains to the plantarflexors in early stance and swing than typical gait simulations. Interpretation: The simulations provide insights into how a musculotendon contracture combined with altered neural control could contribute to idiopathic toe walking. Insights into these neuromuscular mechanisms could guide future computational and experimental studies to gain improved insight into the cause of idiopathic toe walking.Biomechatronics & Human-Machine Contro
Integrated design optimization method for novel vapour-compression-cycle-based environmental control systems
No full textThe aircraft Environmental Control System (ECS) is the primary consumer of non-propulsive power at cruise conditions, hence, its performance optimization is crucial for the reduction of specific fuel consumption. A novel integrated system design optimization method is presented: thermodynamic cycle, component sizing and working fluid are taken into account simultaneously. This method was applied to the ECS of large rotorcraft based on a Vapour Compression Cycle system electrically driven by a high-speed centrifugal compressor. Steady-state and lumped parameter system component models have been developed using the Modelica acausal modelling language. The optimization design framework consists of an in-house code, featuring a Python-Modelica interface. The study case refers to a critical operating condition: the helicopter is on the ground during a hot and humid day. The working fluid is R-134a. The multi-objective optimization targets the maximization of the system efficiency and the minimization of system weight. The results show that more efficient systems can be designed only with heavier components. The design feasibility of high-speed centrifugal compressors is demonstrated. The advantage of an integrated system design optimization framework for complex energy systems is proved, allowing for the analysis of the impact of both component design and working fluid on system performance.Flight Performance and Propulsio
An adaptive parallel arc-length method
No full textParallel computing is omnipresent in today's scientific computer landscape, starting at multicore processors in desktop computers up to massively parallel clusters. While domain decomposition methods have a long tradition in computational mechanics to decompose spatial problems into multiple subproblems that can be solved in parallel, advancing solution schemes for dynamics or quasi-statics are inherently serial processes. For quasi-static simulations, however, there is no accumulating ‘time’ discretization error, hence an alternative approach is required. In this paper, we present an Adaptive Parallel Arc-Length Method (APALM). By using a domain parametrization of the arc-length instead of time, the multi-level error for the arc-length parametrization is formed by the load parameter and the solution norm. Given coarse approximations of arc-length intervals, finer corrections enable the parallelization of the presented method. This results in an arc-length method that is parallel within a branch and inherently adaptive. This concept is easily extended for bifurcation problems. The performance of the method is demonstrated using isogeometric Kirchhoff-Love shells on problems with snap-through and pitch-fork instabilities and applied to the problem of a snapping meta-material. These results show that parallel corrections are performed in a fraction of the time of the serial initialization, achievable on desktop scale.Ship and Offshore StructuresNumerical Analysi
Fracture Mechanics: An Engineering Primer
No full textIn this second edition, which is the result of numerous revisions, updates and additions, the authors cover the basic concepts of fracture mechanics for both the linear elastic and elastic-plastic regimes. The fracture mechanics parameters K, G, J and CTOD are treated in a basic manner along with the test methods to determine critical values. The development of failure assessment based on elastic-plastic fracture mechanics is reflected in a comprehensive treatment.Three chapters are devoted to the fracture mechanics characterisation of crack growth. Fatigue crack growth is extensively treated and attention is paid to the important topic of the initiation and growth of short fatigue cracks. Furthermore, sustained load fracture and dynamic crack growth are discussed, including various test techniques, e.g. the determination of the crack arrest toughness.Finally, there are two chapters dealing with mechanisms of fracture and the ways in which actual material behaviour influences the fracture mechanics characterisation of crack growth. This textbook is intended primarily for engineering students. It will be useful to practising engineers as well, since it provides the background to several test and design methods and to criteria for material selection.TU Delft OPEN TextbookTeam Vera Popovic