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1.	Hait, S., et al. (författare) Impact of ferromagnetic layer thickness on the spin pumping in Co60Fe20B20/Ta bilayer thin films 2021 Ingår i: Journal of Materials Science-Materials in Electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 32, s. 12453-12465 Tidskriftsartikel (refereegranskat)abstract We report the tuneable spin angular momentum transfer (spin pumping) from Co60Fe20B20 (CFB) amorphous alloy into the Ta heavy metal nanolayers. All the films are grown on Si (100) substrate at room temperature using ion-beam sputtering technique. Structural studies reveal that the grown Ta films over amorphous CFB are crystalline even at ultrathin regime. The bilayers possess very low interface roughness (< 0.5 nm) and are continuous throughout the thickness range. Comparative analysis of the spin pumping in CFB (4, 6 and 8 nm) as a function of the Ta thickness (vary from 1 to 10 nm in step of 1 nm) has been performed employing ferromagnetic resonance (FMR) spectroscopy. It is observed that the effective damping increase exponentially with the increase of Ta, (i.e. follows ballistic spin transport) in two series of CFB (4 nm)/Ta (0-10 nm) and CFB(6 nm)/Ta (0-10 nm) bilayers, which is characteristic of normal spin pumping. However, the anomalous behaviour has been observed for CFB (8 nm)/Ta (0-10 nm) bilayer series where the spin current generated in Ta with the thicker CFB behaves oppositely. The results demonstrate the strong dependence of ferromagnet thickness on the spin pumping into the Ta nanolayers. This study paves the way to choose suitable ferromagnetic layer thickness for spin current-induced switching applications in spintronics.
2.	Husain, Sajid, et al. (författare) Multi-jump magnetization switching in Co2FeAl full Heusler alloy thin films : Experiments and simulations 2019 Ingår i: Journal of Magnetism and Magnetic Materials. - : ELSEVIER SCIENCE BV. - 0304-8853 .- 1873-4766. ; 486 Tidskriftsartikel (refereegranskat)abstract Co2FeAl (CFA) thin films of 50 nm thickness have been grown on MgO (001) single crystal substrates at room temperature with and without post-annealing (PA) at 300 degrees C and 400 degrees C using dual ion-beam sputtering technique. The XRD pattern of the as-grown film revealed that CFA grows with preferred crystallographic orientation on the MgO (001) substrate. Temperature dependent anisotropy measurements on PA films revealed a dominating contribution from cubic anisotropy as confirmed by the analysis of azimuthal angle dependent longitudinal in-plane magneto-optical Kerr effect (MOKE) measurements. The contributions from the cubic and uniaxial anisotropies have also been quantified employing ferromagnetic resonance spectroscopy. Magnetization reversal is accompanied with a plateau in the MOKE hysteresis recorded at various azimuthal angles in the in-plane applied magnetic field configuration. The occurrence of the observed plateau is explained by the presence of a combination of domain walls such as 90 degrees, 135 degrees and 180 degrees domain walls and/or complex domains which is supported by results from micromagnetic simulations. These results demonstrate the feasibility of manipulating the magnetization switching in one of the two ferromagnetic electrodes of the magnetic tunnel junction devices based on Heusler alloy ferromagnetic films.
3.	Akansel, Serkan, et al. (författare) Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films 2018 Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 51:30 Tidskriftsartikel (refereegranskat)abstract Fe65Co35 thin films have been deposited on SiO2 substrates using sputtering technique with different choices of seed layer; Ru, Ni82.5Fe17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni82.5Fe17.5 and Rh. Adding these seed layers, the coercivity of the Fe65Co35 films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10-3 and 4.5X10-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10-3 and 4.0X10-3 for annealed samples.
4.	Batkovic, Ivo, 1992, et al. (författare) Experimental Validation of Safe MPC for Autonomous Driving in Uncertain Environments 2023 Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 31:5, s. 2027-2042 Tidskriftsartikel (refereegranskat)abstract The full deployment of autonomous driving systems on a worldwide scale requires that the self-driving vehicle can be operated in a provably safe manner, i.e., the vehicle must be able to avoid collisions in any possible traffic situation. In this article, we propose a framework based on model predictive control (MPC) that endows the self-driving vehicle with the necessary safety guarantees. In particular, our framework ensures constraint satisfaction at all times while tracking the reference trajectory as close as obstacles allow, resulting in a safe and comfortable driving behavior. To discuss the performance and real-time capability of our framework, we provide first an illustrative simulation example, and then, we demonstrate the effectiveness of our framework in experiments with a real test vehicle.
5.	Gupta, Ankit, 1988, et al. (författare) A Framework for Vehicle Lateral Motion Control With Guaranteed Tracking and Performance 2019 Ingår i: 2019 IEEE Intelligent Transportation Systems Conference, ITSC 2019. ; , s. 3607-3612 Konferensbidrag (refereegranskat)abstract In this paper, we propose a framework to design a controller for the vehicle lateral dynamics, which guarantees to meet desired safety and performance requirement. Bounded lateral deviation from the reference trajectory is the strict safety requirement considered in this paper.The proposed control design relies on a mild assumption. That is, the trajectory planner generates a trajectory that is piece-wise clothoidal (PWC), with bounded curvature and curvature rate.Closed-loop simulations using a linear quadratic regulator (LQR) and a model predictive control (MPC) controller, developed based on the proposed framework, validates the proposed approach.
6.	Gupta, Ankit (författare) Adapting Deep Learning for Microscopy: Interaction, Application, and Validation 2023 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Microscopy is an integral technique in biology to study the fundamental components of life visually. Digital microscopy and automation have enabled biologists to conduct faster and larger-scale experiments with a sharp increase in the data generated. Microscopy images contain rich but sparse information, as typically, only small regions in the images are relevant for further study. Image analysis is a crucial tool for biologists in the objective interpretation and extraction of quantitative measurements from microscopy data. Recently, deep learning techniques have shown superior performance in various image analysis tasks. The models learn feature representations from the data by optimizing for a task. However, the techniques require a significant amount of annotated data to perform well. Domain experts are required to annotate microscopy data, making it expensive and time-consuming. The models offer no insight into their prediction, and the learned features are not directly interpretable. This poses challenges to the reliable utilization of the technique in high-trust applications such as drug discovery or disease detection. High data variability in microscopy and poor generalization performance of deep learning models further increase the difficulty in general usage of the technique. The work in this thesis presents frameworks and methods to solve the practical challenges of applying deep learning in microscopy. The application-specific evaluation approaches were presented to validate the approaches, aiming to increase trust in the system. The major contributions of this work are as follows. Papers I and III present human-in-the-loop frameworks for quick adaption of deep learning to new data and for improving models' performance based on human input in visual explanations provided by the model, respectively. Paper II proposes a template-matching approach to improve user interactions in the framework proposed in Paper I. Papers III and IV present architectural modifications in the deep learning models proposed for better visual explanation and image-to-image translation, respectively. Papers IV and V present biologically relevant evaluations of approaches, i.e., analysis of the deep learning models in relation to the biological task.This thesis is aimed towards better utilization and adaptation of the DL methods and techniques to the microscopy data. We show that the annotation burden for the user can be significantly reduced by intuitive annotation frameworks and using contemporary deep-learning paradigms. We further propose architectural modifications in the models to adapt to the requirements and demonstrate the utility of application-specific analysis in microscopy.
7.	Gupta, Ankit, 1988, et al. (författare) Computation of low-complexity control-invariant sets for systems with uncertain parameter dependence 2019 Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 101, s. 330-337 Tidskriftsartikel (refereegranskat)abstract This paper considers the problem of computing a low-complexity robust control-invariant (LC-RCI) set for uncertain systems, along with a static linear state-feedback law. The LC-RCI set, assumed to be symmetric around the origin and described by the same number of affine inequalities as twice the dimension of the state vector, is the result of an iterative procedure, where semi-definite programs (SDPs) are solved at each step. The SDPs are formulated to increase the LC-RCI volume at each step, subject to tractable reformulations of the system constraints as well as the invariance condition (in the form of standard or dilated LMIs), and a new approach to determinant maximization. The two proposed algorithms are applicable to systems with rational parameter dependence, which cannot be handled with the existing similar approaches without introducing additional conservatism.
8.	Gupta, Ankit, 1988, et al. (författare) Computation of Parameter Dependent Robust Invariant Sets for LPV Models with Guaranteed Performance 2023 Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 151 Tidskriftsartikel (refereegranskat)abstract This paper presents an iterative algorithm to compute a Robust Control Invariant (RCI) set, along with an invariance-inducing control law, for Linear Parameter-Varying (LPV) systems. As the real-time measurements of the scheduling parameters are typically available, in the presented formulation, we allow the RCI set description along with the invariance-inducing controller to be scheduling parameter dependent. The considered formulation thus leads to parameter-dependent conditions for the set invariance, which are replaced by sufficient Linear Matrix Inequality (LMI) conditions via Polya's relaxation. These LMI conditions are then combined with a novel volume maximization approach in a Semidefinite Programming (SDP) problem, which aims at computing the desirably large RCI set. In addition to ensuring invariance, it is also possible to guarantee performance within the RCI set by imposing a chosen quadratic performance level as an additional constraint in the SDP problem. The reported numerical example shows that the presented iterative algorithm can generate invariant sets which are larger than the maximal RCI sets computed without exploiting scheduling parameter information.
9.	Gupta, Ankit, 1988, et al. (författare) Computation of Robust Control Invariant Sets with Predefined Complexity for Uncertain Systems 2021 Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 31:5, s. 1674-1688 Tidskriftsartikel (refereegranskat)abstract This paper presents an algorithm that computes polytopic robust control-invariant (RCI) sets for rationally parameter-dependent systems with additive disturbances. By means of novel LMI feasibility conditions for invariance along with a newly developed method for volume maximization, an iterative algorithm is proposed for the computation of RCI sets with maximized volumes. The obtained RCI sets are symmetric around the origin by construction and have a user-defined level of complexity. Unlike many similar approaches, fixed state feedback structure is not imposed. In fact, a specific control input is obtained from the LMI problem for each extreme point of the RCI set. The outcomes of the proposed algorithm can be used to construct a piecewise-affine controller based on offline computations.
10.	Gupta, Ankit, 1988 (författare) Control of Constrained Dynamical Systems with Performance Guarantees: With Application to Vehicle motion Control 2021 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In control engineering, models of the system are commonly used for controller design. A standard control design problem consists of steering the given system output (or states) towards a predefined reference. Such a problem can be solved by employing feedback control strategies. By utilizing the knowledge of the model, these strategies compute the control inputs that shrink the error between the system outputs and their desired references over time. Usually, the control inputs must be computed such that the system output signals are kept in a desired region, possibly due to design or safety requirements. Also, the input signals should be within the physical limits of the actuators. Depending on the constraints, their violation might result in unacceptable system failures (e.g. deadly injury in the worst case). Thus, in safety-critical applications, a controller must be robust towards the modelling uncertainties and provide a priori guarantees for constraint satisfaction. A fundamental tool in constrained control application is the robust control invariant sets (RCI). For a controlled dynamical system, if initial states belong to RCI set, control inputs always exist that keep the future state trajectories restricted within the set. Hence, RCI sets can characterize a system that never violates constraints. These sets are the primary ingredient in the synthesis of the well-known constraint control strategies like model predictive control (MPC) and interpolation-based controller (IBC). Consequently, a large body of research has been devoted to the computation of these sets. In the thesis, we will focus on the computation of RCI sets and the method to generate control inputs that keep the system trajectories within RCI set. We specifically focus on the systems which have time-varying dynamics and polytopic constraints. Depending upon the nature of the time-varying element in the system description (i.e., if they are observable or not), we propose different sets of algorithms. The first group of algorithms apply to the system with time-varying, bounded uncertainties. To systematically handle the uncertainties and reduce conservatism, we exploit various tools from the robust control literature to derive novel conditions for invariance. The obtained conditions are then combined with a newly developed method for volume maximization and minimization in a convex optimization problem to compute desirably large and small RCI sets. In addition to ensuring invariance, it is also possible to guarantee desired closed-loop performance within the RCI set. Furthermore, developed algorithms can generate RCI sets with a predefined number of hyper-planes. This feature allows us to adjust the computational complexity of MPC and IBC controller when the sets are utilized in controller synthesis. Using numerical examples, we show that the proposed algorithms can outperform (volume-wise) many state-of-the-art methods when computing RCI sets. In the other case, we assume the time-varying parameters in system description to be observable. The developed algorithm has many similar characteristics as the earlier case, but now to utilize the parameter information, the control law and the RCI set are allowed to be parameter-dependent. We have numerically shown that the presented algorithm can generate invariant sets which are larger than the maximal RCI sets computed without exploiting parameter information. Lastly, we demonstrate how we can utilize some of these algorithms to construct a computationally efficient IBC controller for the vehicle motion control. The devised IBC controller guarantees to meet safety requirements mentioned in ISO 26262 and the ride comfort requirement by design.
11.	Gupta, Ankit, et al. (författare) Efficient High-Resolution Template Matching with Vector Quantized Nearest Neighbour Fields 2024 Ingår i: Pattern Recognition. - : Elsevier. - 0031-3203 .- 1873-5142. ; 151 Tidskriftsartikel (refereegranskat)abstract Template matching is a fundamental problem in computer vision with applications in fields including object detection, image registration, and object tracking. Current methods rely on nearest-neighbour (NN) matching, where the query feature space is converted to NN space by representing each query pixel with its NN in the template. NN-based methods have been shown to perform better in occlusions, appearance changes, and non-rigid transformations; however, they scale poorly with high-resolution data and high feature dimensions. We present an NN-based method that efficiently reduces the NN computations and introduces filtering in the NN fields (NNFs). A vector quantization step is introduced before the NN calculation to represent the template with k features, and the filter response over the NNFs is used to compare the template and query distributions over the features. We show that state-of-the-art performance is achieved in low-resolution data, and our method outperforms previous methods at higher resolution.
12.	Gupta, Ankit, 1988, et al. (författare) Full-complexity characterization of control-invariant domains for systems with uncertain parameter dependence 2019 Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 3:1, s. 19-24 Tidskriftsartikel (refereegranskat)abstract This letter proposes an algorithm to find a robust control invariant (RCI) set of desired complexity and the associated linear, state-feedback control law. The candidate RCI set is restricted to be symmetric around the origin. The algorithm is applicable to rational parameter dependent systems with bounded additive disturbance. The system constraints are framed as simple affine inequalities whereas the invariance condition as a set of sufficient LMI conditions. The proposed iterative algorithm is guaranteed to be recursively feasible and converge to some stationary point.
13.	Gupta, Ankit, et al. (författare) Is brightfield all you need for MoA prediction? 2022 Konferensbidrag (refereegranskat)abstract Fluorescence staining techniques, such as Cell Painting, together with fluorescence microscopy have proven invaluable for visualizing and quantifying the effects that drugs and other perturbations have on cultured cells. However, fluorescence microscopy is expensive, time-consuming, and labor-intensive, and the stains applied can be cytotoxic, interfering with the activity under study. The simplest form of microscopy, brightfield microscopy, lacks these downsides, but the images produced have low contrast and the cellular compartments are difficult to discern. Nevertheless, by harnessing deep learning, these brightfield images may still be sufficient for various predictive purposes. In this study, we compared the predictive performance of models trained on fluorescence images to those trained on brightfield images for predicting the mechanism of action (MoA) of different drugs. We also extracted CellProfiler features from the fluorescence images and used them to benchmark the performance. Overall, we found comparable and correlated predictive performance for the two imaging modalities. This is promising for future studies of MoAs in time-lapse experiments.
14.	Gupta, Ankit, 1988, et al. (författare) Low-Complexity Explicit MPC Controller for Vehicle Lateral Motion Control 2018 Ingår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC. ; 2018-November, s. 2839-2844 Konferensbidrag (refereegranskat)abstract We consider the problem of controlling the vehicle lateral motion in highway scenarios while guaranteeing safety. We propose a solution consisting of a Low-Complexity Explicit Model Predictive Controller (LC-EMPC), where the lateral deviation from the desired path is hard constrained according to prescribed bounds. The robust satisfaction of such safety constraints can be achieved by imposing the terminal state to enter a Robust Invariant Set (RIS), which is known to result into a potentially high number of additional constraints, thus increasing the computational complexity of the controller. Our controller, instead, relies on recent results on the calculation of low-complexity RIS to significantly reduce the number of constraints in the MPC controller. Simulation results show that the designed controller is able to meet the desired objectives with highly reduced complexity.
15.	Gupta, Ankit, et al. (författare) Reconstruction of Bacterial and Viral Genomes from Multiple Metagenomes. 2016 Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 7:April Tidskriftsartikel (refereegranskat)abstract Several metagenomic projects have been accomplished or are in progress. However, in most cases, it is not feasible to generate complete genomic assemblies of species from the metagenomic sequencing of a complex environment. Only a few studies have reported the reconstruction of bacterial genomes from complex metagenomes. In this work, Binning-Assembly approach has been proposed and demonstrated for the reconstruction of bacterial and viral genomes from 72 human gut metagenomic datasets. A total 1156 bacterial genomes belonging to 219 bacterial families and, 279 viral genomes belonging to 84 viral families could be identified. More than 80% complete draft genome sequences could be reconstructed for a total of 126 bacterial and 11 viral genomes. Selected draft assembled genomes could be validated with 99.8% accuracy using their ORFs. The study provides useful information on the assembly expected for a species given its number of reads and abundance. This approach along with spiking was also demonstrated to be useful in improving the draft assembly of a bacterial genome. The Binning-Assembly approach can be successfully used to reconstruct bacterial and viral genomes from multiple metagenomic datasets obtained from similar environments.
16.	Gupta, Ankit, 1988, et al. (författare) Restricted-Complexity Characterization of Control-Invariant Domains with Application to Lateral Vehicle Dynamics Control 2017 Ingår i: IEEE Conference on Decision and Control. - 9781509028733 ; 2018-January, s. 4946-4951 Konferensbidrag (refereegranskat)abstract This paper proposes two algorithms to find a restricted-complexity robust control invariant (RCI) set along with a state-feedback gain. These algorithms are applicable to a linear system with additive disturbances subject to found polytopic state and input constraints. The RCI set is a polytope with restricted complexity, symmetric around the origin. Using a state transformation, novel LMI conditions are derived for the system constraints and invariance condition. Moreover, a new approach is proposed to iteratively increase the volume of the computed RCI set. The effectiveness of the proposed algorithm is illustrated by using lateral vehicle dynamics control example.
17.	Gupta, Ankit, et al. (författare) SimSearch : A Human-in-The-Loop Learning Framework for Fast Detection of Regions of Interest in Microscopy Images 2022 Ingår i: IEEE journal of biomedical and health informatics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2168-2194 .- 2168-2208. ; 26:8, s. 4079-4089 Tidskriftsartikel (refereegranskat)abstract Objective: Large-scale microscopy-based experiments often result in images with rich but sparse information content. An experienced microscopist can visually identify regions of interest (ROIs), but this becomes a cumbersome task with large datasets. Here we present SimSearch, a framework for quick and easy user-guided training of a deep neural model aimed at fast detection of ROIs in large-scale microscopy experiments. Methods: The user manually selects a small number of patches representing different classes of ROIs. This is followed by feature extraction using a pre-trained deep-learning model, and interactive patch selection pruning, resulting in a smaller set of clean (user approved) and larger set of noisy (unapproved) training patches of ROIs and background. The pre-trained deep-learning model is thereafter first trained on the large set of noisy patches, followed by refined training using the clean patches. Results: The framework is evaluated on fluorescence microscopy images from a large-scale drug screening experiment, brightfield images of immunohistochemistry-stained patient tissue samples, and malaria-infected human blood smears, as well as transmission electron microscopy images of cell sections. Compared to state-of-the-art and manual/visual assessment, the results show similar performance with maximal flexibility and minimal a priori information and user interaction. Conclusions: SimSearch quickly adapts to different data sets, which demonstrates the potential to speed up many microscopy-based experiments based on a small amount of user interaction. Significance: SimSearch can help biologists quickly extract informative regions and perform analyses on large datasets helping increase the throughput in a microscopy experiment.
18.	Gupta, Ankit, et al. (författare) Towards Better Guided Attention and Human Knowledge Insertion in Deep Convolutional Neural Networks 2022 Konferensbidrag (refereegranskat)abstract Attention Branch Networks (ABNs) have been shown to simultaneously provide visual explanation and improve the performance of deep convolutional neural networks (CNNs). In this work, we introduce Multi-Scale Attention Branch Networks (MSABN), which enhance the resolution of the generated attention maps, and improve the performance. We evaluate MSABN on benchmark image recognition and fine-grained recognition datasets where we observe MSABN outperforms ABN and baseline models. We also introduce a new data augmentation strategy utilizing the attention maps to incorporate human knowledge in the form of bounding box annotations of the objects of interest. We show that even with a limited number of edited samples, a significant performance gain can be achieved with this strategy.
19.	Gupta, Rahul, et al. (författare) Co2FeAl Full Heusler Compound Based Spintronic Terahertz Emitter 2021 Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 9:10 Tidskriftsartikel (refereegranskat)abstract To achieve a large terahertz (THz) amplitude from a spintronic THz emitter (STE), materials with 100% spin polarisation such as Co-based Heusler compounds as ferromagnetic layer are required. However, these compounds are known to loose their half-metallicity in the ultrathin film regime, as it is difficult to achieve L2(1) ordering, which has become a bottleneck for the film growth. Here, the successful deposition using room temperature DC sputtering of the L2(1) and B2 ordered phases of the Co2FeAl full Heusler compound is reported. Co2FeAl is used as ferromagnetic layer together with highly orientated Pt as nonferromagnetic layer in the Co2FeAl/Pt STE, where an MgO (10 nm) seed layer plays an important role to achieve the L2(1) and B2 ordering of Co2FeAl. The THz generation in the Co2FeAl/Pt STE is presented, which has a bandwidth of 0.2-4 THz. The THz electric field amplitude is optimized with respect to thickness, orientation, and growth parameters using a thickness dependent model considering the optically induced spin current, superdiffusive spin current, inverse spin Hall effect, and the THz attenuation in the layers. This study, based on the full Heusler Co2FeAl compound opens up a plethora of possibilities in STE research involving full Heusler compounds.
20.	Gupta, Rahul, et al. (författare) Engineering of spin mixing conductance at Ru/FeCo/Ru interfaces : Effect of Re doping 2020 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : AMER PHYSICAL SOC. - 1098-0121 .- 1550-235X. ; 101:2 Tidskriftsartikel (refereegranskat)abstract We have deposited polycrystalline Re-doped (Fe65Co35)(100-x)Rex (0 ≤ x ≤ 12.6 at. %) thin films grown under identical conditions and sandwiched between thin layers of Ru in order to study the phenomenon of spin pumping as a function of Re concentration. In-plane and out-of-plane ferromagnetic resonance spectroscopy results show an enhancement of the Gilbert damping with an increase in Re doping. We find 98% enhancement in the real part of effective spin mixing conductance [Re(g↑↓eff)] with Re doping. Conversely, the Re(g↑↓eff) does not change with Re doping in Fe65Co35 thin films which are seeded and capped with Cu layers. The enhancement in Re(g↑↓eff) of Re-doped Fe65Co35 thin films sandwiched between thin layers of Ru is linked to the Re doping-induced change of the interface electronic structure in the nonmagnetic Ru layer. The saturation magnetization decreases 35% with increasing Re doping up to 12.6 at. %. This study opens a direction of tuning the spin mixing conductance in magnetic heterostructures by doping of the ferromagnetic layer, which is essential for the realization of energyefficient operation of spintronic devices.
21.	Harrison, Philip John, et al. (författare) Evaluating the utility of brightfield image data for mechanism of action prediction 2023 Ingår i: PloS Computational Biology. - : Public Library of Science (PLoS). - 1553-734X .- 1553-7358. ; 19:7 Tidskriftsartikel (refereegranskat)abstract Fluorescence staining techniques, such as Cell Painting, together with fluorescence microscopy have proven invaluable for visualizing and quantifying the effects that drugs and other perturbations have on cultured cells. However, fluorescence microscopy is expensive, time-consuming, labor-intensive, and the stains applied can be cytotoxic, interfering with the activity under study. The simplest form of microscopy, brightfield microscopy, lacks these downsides, but the images produced have low contrast and the cellular compartments are difficult to discern. Nevertheless, by harnessing deep learning, these brightfield images may still be sufficient for various predictive purposes. In this study, we compared the predictive performance of models trained on fluorescence images to those trained on brightfield images for predicting the mechanism of action (MoA) of different drugs. We also extracted CellProfiler features from the fluorescence images and used them to benchmark the performance. Overall, we found comparable and largely correlated predictive performance for the two imaging modalities. This is promising for future studies of MoAs in time-lapse experiments for which using fluorescence images is problematic. Explorations based on explainable AI techniques also provided valuable insights regarding compounds that were better predicted by one modality over the other.
22.	Husain, Sajid, et al. (författare) Emergence of spin-orbit torques in 2D transition metal dichalcogenides: A status update 2020 Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 7:4 Tidskriftsartikel (refereegranskat)abstract Spin-orbit coupling (SOC) in two-dimensional (2D) materials has emerged as a powerful tool for designing spintronic devices. On the one hand, the interest in this respect for graphene, the most popular 2D material with numerous fascinating and exciting properties, is fading due to the absence of SOC. On the other hand, 2D transition metal dichalcogenides (TMDs) are known to exhibit rich physics including large SOC. TMDs have been used for decades in a variety of applications such as nano-electronics, photonics, optoelectronics, sensing, and recently also in spintronics. Here, we review the current progress in research on 2D TMDs for generating spin-orbit torques in spin-logic devices. Several challenges connecting to thin film growth, film thickness, layer symmetry, and transport properties and their impact on the efficiency of spintronic devices are reviewed. How different TMDs generate spin-orbit torques in magnetic heterostructures is discussed in detail. Relevant aspects for improving the quality of the thin film growth as well as the efficiency of the generated spin-orbit torques are discussed together with future perspectives in the field of spin-orbitronics.
23.	Husain, Sajid, et al. (författare) Large Damping-Like Spin–Orbit Torque in a 2D Conductive 1T-TaS2 Monolayer 2020 Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 20:9, s. 6372-6380 Tidskriftsartikel (refereegranskat)abstract A damping-like spin-orbit torque (SOT) is a prerequisite for ultralow-power spin logic devices. Here, we report on the damping-like SOT in just one monolayer of the conducting transition-metal dichalcogenide (TMD) TaS2 interfaced with a NiFe (Py) ferromagnetic layer. The charge-spin conversion efficiency is found to be 0.25 +/- 0.03 in TaS2(0.88)/Py(7), and the spin Hall conductivity (14.9 x 10(s) h/2e Omega(-1) m(-1) is found to be superior to values reported for other TMDs. We also observed sizable field-like torque in this heterostructure. The origin of this large damping-like SOT can be found in the interfacial properties of the TaS2/Py heterostructure, and the experimental findings are complemented by the results from density functional theory calculations. It is envisioned that the interplay between interfacial spinorbit coupling and crystal symmetry yielding large damping-like SOT. The dominance of damping-like torque demonstrated in our study provides a promising path for designing the next-generation conducting TMD-based low-powered quantum memory devices.
24.	Husain, Sajid, et al. (författare) Probing Charge Density Wave Effects in 1T-TaS2 Monolayer/Ni81Fe19 Heterostructure: A Spin Dynamics Approach 2021 Ingår i: Acs Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 3:8, s. 3321-3328 Tidskriftsartikel (refereegranskat)abstract The transition metal dichalcogenide 1T-TaS2 is known to exhibit a number of collective electronic states known as charge density wave (CDW) instabilities. Intriguing phenomena such as a large damping-like spin-orbit torque (SOT) have been reported in monolayer 1T-TaS2 [Nano Lett. 2020, 20 (9), 6372-6380]. Probing of CDWs in monolayer thick 1T-TaS2 has been an inconceivable task. Here, the temperature-dependent spin dynamics and the effect of CDWs in the 1T-TaS2(monolayer)/Ni81Fe19 (Py) (7 nm) heterostructure are reported. Employing ferromagnetic resonance, the effect of the different commensurate (C) and nearly commensurate (NC) CDW states on the spin dynamics during heating and cooling cycles has been characterized by use of the effective damping constant and the spin mixing conductance of the heterostructure. In addition, these CCDW and NCCDW states, which affect the SOT efficiencies due to damping- and field-like SOTs, have been evaluated by using angle-dependent planar Hall effect measurements in controlled cooling and heating cycles. Our findings provide a fundamental understanding of the effect of different CDW states on the spin dynamics in twodimensional 1T-TaS2 monolayer interfaced Py.
25.	Khoshkangini, Reza, 1984-, et al. (författare) Forecasting Components Failures Using Ant Colony Optimization for Predictive Maintenance 2021 Ingår i: Proceedings of the 31st European Safety and Reliability Conference. - Singapore : European Safety and Reliability Association. - 9789811820168 ; , s. 2947-2954 Konferensbidrag (refereegranskat)abstract Failures are the eminent aspect of any sophisticated machine such as vehicles. Early detection of faults and prioritized maintenance is a necessity of vehicle manufacturers as it enables them to reduce maintenance costs, safety risks and increase customer satisfaction. In this study, we propose to use a type of Ant Colony Optimization (ACO) algorithm to diagnose vehicles faults. We explore the effectiveness of ACO for solving fault detection in the form of a classification problem, which would be used for predictive maintenance by the manufacturers. We show experimental evaluations on the real data captured from heavy-duty trucks illustrating how optimization algorithms can be used as a classification approach to forecast component failures in the context of predictive maintenance © ESREL 2021
26.	Klintberg, Emil, 1989, et al. (författare) A primal active-set minimal-representation algorithm for polytopes with application to invariant-set calculations 2018 Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; 2018-December, s. 6862-6867 Konferensbidrag (refereegranskat)abstract This paper provides a description of a practically efficient minimal-representation algorithm for polytopes. The algorithm is based on a primal active-set method that heavily exploits warm-starts and low-rank updates of matrix factorizations in order to reduce the required computational work. By using a primal active-set method, several nonredundant inequalities can be identified for each solved linear program. Implementation details are provided both for the minimalrepresentation algorithm and for the underlying active-set method.
27.	Klintberg, Emil, 1989, et al. (författare) Tree-Structured Polyhedral Invariant Set Calculations 2020 Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 4:2, s. 426-431 Tidskriftsartikel (refereegranskat)abstract This letter provides a description of how hierarchical dependencies between inequalities can be exploited in order to efficiently calculate polyhedral approximations of maximal robust positive invariant sets using geometrically motivated methods. Due to the hierarchical dependencies, the calculations of preimage sets and minimal representations can be alleviated. It is also shown that as a byproduct from the calculations of minimal representations, a stopping criterion is obtained, which means that the commonly used subset test is superfluous.
28.	Kojchev, Stefan, 1992, et al. (författare) An iterative algorithm for volume maximization of N-step backward reachable sets for constrained linear time-varying systems 2021 Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; 2021-December, s. 5027-5032 Konferensbidrag (refereegranskat)abstract In this paper, we consider the computation of robust N-step backward reachable sets for state-and input con-strained linear time-varying systems with additive uncertainty. We propose a method to compute a linear, time-varying control law that maximizes the volume of the robust N-step reachable set for the closed-loop system. The proposed method is an extension of recent developments and involves the recursive solution of N semi-definite programs (SDP). We demonstrate the performance of the proposed method on the lateral control problem for emergency maneuvers of autonomous vehicles and compare it to results obtained when backward reachability is applied to the same system and a naively designed controller.
29.	Kok, Fatma O., et al. (författare) Reverse Genetic Screening Reveals Poor Correlation between Morpholino-Induced and Mutant Phenotypes in Zebrafish 2015 Ingår i: Developmental Cell. - : Elsevier BV. - 1534-5807 .- 1878-1551. ; 32:1, s. 97-108 Tidskriftsartikel (refereegranskat)abstract The widespread availability of programmable site-specific nucleases now enables targeted gene disruption in the zebrafish. In this study, we applied site-specific nucleases to generate zebrafish lines bearing individual mutations in more than 20 genes. We found that mutations in only a small proportion of genes caused defects in embryogenesis. Moreover, mutants for ten different genes failed to recapitulate published Morpholino-induced phenotypes (morphants). The absence of phenotypes in mutant embryos was not likely due to maternal effects or failure to eliminate gene function. Consistently, a comparison of published morphant defects with the Sanger Zebrafish Mutation Project revealed that approximately 80% of morphant phenotypes were not observed in mutant embryos, similar to our mutant collection. Based on these results, we suggest that mutant phenotypes become the standard metric to define gene function in zebrafish, after which Morpholinos that recapitulate respective phenotypes could be reliably applied for ancillary analyses.
30.	Kumar, Ankit, et al. (författare) Impact of the crystal orientation on spin-orbit torques in Fe/Pd bilayers 2020 Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 53:35 Tidskriftsartikel (refereegranskat)abstract Spin-orbit torques in ferromagnetic/non-magnetic heterostructures offer more energy-efficient means to realize spin-logic devices; however, their strengths are determined by the heterostructure interface. This work examines the impact of crystal orientation on the spin-orbit torque efficiency in different Fe/Pd bilayer systems. Results from spin torque ferromagnetic resonance measurements evidence that the damping-like torque efficiency is higher in epitaxial than in polycrystalline bilayer structures while the field-like torque is negligible in all bilayer structures. The strength of the damping-like torque decreases with deterioration of the bilayer epitaxial quality. The present finding provides fresh insight for the enhancement of spin-orbit torques in magnetic heterostructures.
31.	Kumar, Ankit, et al. (författare) Spin pumping and spin torques in interfacially tailored Co2FeAl/beta-Ta layers 2019 Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 100:21 Tidskriftsartikel (refereegranskat)abstract The Heusler ferromagnetic (FM) compound Co2FeAl interfaced with a high spin-orbit coupling nonmagnetic (NM) layer is a promising candidate for energy-efficient spin-logic circuits. The circuit potential depends on the strength of angular momentum transfer across the FM/NM interface, hence requiring low spin-memory loss and high spin-mixing conductance. To highlight this issue, spin pumping and spin torque ferromagnetic resonance measurements have been performed on Co2FeAl/beta-Ta heterostructures tailored with Cu interfacial layers. The interface tailored structure yields an enhancement of the effective spin-mixing conductance. The interface transparency and spin-memory loss corrected values of the spin-mixing conductance, spin Hall angle, and spin-diffusion length are found to be 3.40 +/- 0.01x10(19) m(-2), 0.029 +/- 0.003, and 2.3 +/- 0.5 nm, respectively. Furthermore, a high current modulation of the effective damping of around 2.1% has been achieved at an applied current density of 1 x 10(9)A/m(2), which clearly indicates the potential of using this heterostructure for energy-efficient control in spin devices.
32.	Malik, Rameez Saeed, 1987-, et al. (författare) Ultrafast dynamics in Fe65Co35 alloys: Effect of Re doping Annan publikation (populärvet., debatt m.m.)abstract Soft magnetic FeCo alloys are of great interest due to their potential spintronics applications. The magnetic damping parameter plays a vital role in the performance of these spintronics devices. The Gilbert damping parameter increase in these alloys with doping of 5d elements. Here, we have investigated the effect of Re doping on the element-specific magnetization dynamics of Ru/Fe65Co35/Ru thin films using the time-resolved magneto-optical Kerr effect. When varying the concentration of Re from 0 to 12.6 %, no change of the demagnetization time constant is observed. However, a gradual change of the remagnetization time is observed with the increase of Re concentration. This remagnetization dynamics can be related to the Gilbert damping parameter of these films. An interesting time-resolved dynamics at the Ru-edge is observed. A significant increase (40%) of the asymmetry signal is observed for the undoped sample and drops down with the Re doping. This effect is possibly a super diffusive spin current going from the magnetic layer to the non magnetic capping layer.
33.	Malik, Rameez Saeed, 1987-, et al. (författare) Ultrafast magnetization dynamics in half-metallic Co2FeAl Heusler alloy Annan publikation (populärvet., debatt m.m.)abstract We report on optically induced, ultrafast magnetization dynamics in the Heusler alloy Co2FeAl,probed by time-resolved magneto-optical Kerr effect. Experimental results are compared to resultsfrom electronic structure theory and atomistic spin-dynamics simulations. Experimentally, we findthat the demagnetization time (τM) in films of Co2FeAl is almost independent of varying structuralorder, and that it is similar to that in elemental 3d ferromagnets. In contrast, the slower processof magnetization recovery, specified byτR, is found to occur on picosecond time scales, and isdemonstrated to correlate strongly with the Gilbert damping parameter (α). Our results showthat Co2FeAl is unique, in that it is the first material that clearly demonstrates the importance ofthe damping parameter in the remagnetization process. Based on these results we argue that for Co2FeAl the remagnetization process is dominated by magnon dynamics, something which mighthave general applicabilit
34.	Ni, Lei, et al. (författare) Vehicle Lateral Motion Control with Performance and Safety Guarantees 2016 Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 49:11, s. 285-290 Konferensbidrag (refereegranskat)abstract This paper explores the use of Model Predictive Control (MPC) techniques to solve vehicle lateral motion control problem on highway scenarios. In particular, the problem of autonomously driving a vehicle along a desired path is formulated, where safety constraints and performance levels must be guaranteed for all possible road curvatures within a con [pact set. Safety constraints are translated into a maximum lateral deviation and orientation error w.r.t. a desired path, while performance requirements are formulated in terms of bounded lateral acceleration and velocity. Preliminary simulation results ahoy that the designed controller is capable of delivering acceptable performance at the cost of limited online computational costs. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
35.	Nilsson, Magnus, et al. (författare) Admissible sets for polytopic linear systems subject to slowly-varying unobservable disturbances 2020 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract This note describes a method to calculate sets of safe initial conditions for polytopic linear systems subject to slowly-varying unobservable disturbances. Such sets are herein called admissible sets; invariant sets are admissible but admissible sets are not necessarily invariant. By examining conditions for admissible sets of this particular system class, we prove that admissible sets can be calculated by only considering a special property that we call \emph{the $\lambda$-proximal-contraction property} at the vertices of the set that bounds the slowly-varying disturbances. An academic example is used to illustrate how to apply the method, and a discussion follows that summarizes the main points.
36.	Sharma, Ashok K., et al. (författare) Woods : A fast and accurate functional annotator and classifier of genomic and metagenomic sequences 2015 Ingår i: Genomics. - : Academic Press. - 0888-7543 .- 1089-8646. ; 106:1, s. 1-6 Tidskriftsartikel (refereegranskat)abstract Functional annotation of the gigantic metagenomic data is one of the major time-consuming and computationally demanding tasks, which is currently a bottleneck for the efficient analysis. The commonly used homology-based methods to functionally annotate and classify proteins are extremely slow. Therefore, to achieve faster and accurate functional annotation, we have developed an orthology-based functional classifier 'Woods' by using a combination of machine learning and similarity-based approaches. Woods displayed a precision of 98.79% on independent genomic dataset, 96.66% on simulated metagenomic dataset and >97% on two real metagenomic datasets. In addition, it performed >87 times faster than BLAST on the two real metagenomic datasets. Woods can be used as a highly efficient and accurate classifier with high-throughput capability which facilitates its usability on large metagenomic datasets.
37.	Wieslander, Håkan, et al. (författare) Learning to see colours: Biologically relevant virtual staining for adipocyte cell images 2021 Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 16:10 Tidskriftsartikel (refereegranskat)abstract Fluorescence microscopy, which visualizes cellular components with fluorescent stains, is an invaluable method in image cytometry. From these images various cellular features can be extracted. Together these features form phenotypes that can be used to determine effective drug therapies, such as those based on nanomedicines. Unfortunately, fluorescence microscopy is time-consuming, expensive, labour intensive, and toxic to the cells. Bright-field images lack these downsides but also lack the clear contrast of the cellular components and hence are difficult to use for downstream analysis. Generating the fluorescence images directly from bright-field images using virtual staining (also known as “label-free prediction” and “in-silico labeling”) can get the best of both worlds, but can be very challenging to do for poorly visible cellular structures in the bright-field images. To tackle this problem deep learning models were explored to learn the mapping between bright-field and fluorescence images for adipocyte cell images. The models were tailored for each imaging channel, paying particular attention to the various challenges in each case, and those with the highest fidelity in extracted cell-level features were selected. The solutions included utilizing privileged information for the nuclear channel, and using image gradient information and adversarial training for the lipids channel. The former resulted in better morphological and count features and the latter resulted in more faithfully captured defects in the lipids, which are key features required for downstream analysis of these channels.
38.	Zhang, Tianru, et al. (författare) Data management of scientific applications in a reinforcement learning-based hierarchical storage system 2024 Ingår i: Expert systems with applications. - : Elsevier. - 0957-4174 .- 1873-6793. ; 237 Tidskriftsartikel (refereegranskat)abstract In many areas of data-driven science, large datasets are generated where the individual data objects are images, matrices, or otherwise have a clear structure. However, these objects can be information-sparse, and a challenge is to efficiently find and work with the most interesting data as early as possible in an analysis pipeline. We have recently proposed a new model for big data management where the internal structure and information of the data are associated with each data object (as opposed to simple metadata). There is then an opportunity for comprehensive data management solutions to account for data-specific internal structure as well as access patterns. In this article, we explore this idea together with our recently proposed hierarchical storage management framework that uses reinforcement learning (RL) for autonomous and dynamic data placement in different tiers in a storage hierarchy. Our case-study is based on four scientific datasets: Protein translocation microscopy images, Airfoil angle of attack meshes, 1000 Genomes sequences, and Phenotypic screening images. The presented results highlight that our framework is optimal and can quickly adapt to new data access requirements. It overall reduces the data processing time, and the proposed autonomous data placement is superior compared to any static or semi-static data placement policies.

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