https://research.chalmers.se/ 2026-09-22 00:16:46 Visar de 30 senaste forskningspublikationerna för Chalmers https://research.chalmers.se//Images/chalmers_bldmrk.jpg Odd-chain fatty acids (OCFAs) are high-value lipids with emerging medical and nutritional applications. However, their natural abundance is low, and conventional extraction or chemical synthesis methods are inefficient or unsustainable. Microbial fermentation using oleaginous yeasts offers a promising alternative, particularly when employing short-chain fatty acids digestates rich in propionic acid, the main precursor for OCFA synthesis.In this thesis work yeast-based OCFA production has been explored by improving quantitative analytical methods, identifying suitable yeast cell factories, characterizing their performance, and initiating strain engineering efforts. First, a fatty acid methyl ester protocol was optimized for robust OCFA analysis. Second, eight strains capable of growth on 15 g/L propionic acid and production of OCFA were identified in a screening of nineteen oleaginous yeasts. Third, four yeast species were selected for further study: Cutaneotrichosporon oleaginosus for its high OCFA titers, Rhodotorula toruloides for its high OCFA yield, Yarrowia lipolytica for its high tolerance to propionic acid, and Blastobotrys adeninivorans for its ability to produce OCFAs, grow well in propionic acid and as a relatively underexplored yeast. Cultivation on mixtures of acetic and propionic acids at different carbon-to-nitrogen ratios revealed distinct and interesting performance characteristics for OCFA production in each yeast species. Fourth, a plasmid-based CRISPR-Cas9 metabolic engineering platform was established for B. adeninivorans through the identification of native autonomous replication systems, enabling the generation of mutants with enhanced OCFA content.Overall, this work advances methodologies for fatty acid analysis, identifies promising oleaginous yeasts for OCFA production and characterize them, and establishes a new genetic engineering tool for strain development. These results provide a foundation for the development of efficient yeast cell factories and economically viable bioprocesses for sustainable OCFA production. Doktorsavhandling 2026-09-21 17:21:28 https://research.chalmers.se/publication/554064 2026-09-21T17:21:28Z Let us imagine that we have a circular support of known radius in 2 dimensions and that we want to construct a minimum weight cantilever of a given span to support a mouse at the tip and the weight of the cantilever itself. The cantilever is made from 2 materials, one for tension and one for compression, with known strengths. We will make the same assumptions that Anthony Michell made in his seminal paper of 1904, 'The limits of economy of material in frame-structures', except that we will include the own weight of the structure, which Michell did not. However we follow Michell in ignoring buckling and thus the structure will consist of a fine network of pin ended struts and ties in which compression members can be very slender. This assumption means that if we replace our mouse by a rat that weights 10 times as much, then the whole structure will have to weight 10 times a much. We offer an alternative derivation of Michell's result, again using virtual power (also known as virtual work) as he did. Including the own weight of the structure in the formulation means that the equations almost certainly require a numerical solution, and we present numerical results for the cantilever, which we compare to Michell's for the special case of a weightless cantilever. Paper i proceeding 2026-09-21 17:11:02 https://research.chalmers.se/publication/554068 2026-09-21T17:11:02Z We present a simple cracked elastic model that can be used for the analysis of slender masonry arches where elastic deformation and cracking significantly reduce the load capacity. The aim of this work is to produce results that can be compared with those obtained from more sophisticated numerical methods such as the finite element method and the discrete element method. The proposed formulation uses Euler-Bernoulli beam theory and considers only the compressed part of the cross-section. The arch is discretised using three-node quadratic B-spline beam elements and solved using dynamic relaxation. Using displacement control, we investigate how Young's modulus and cracking affect the peak load under a point load. The results of our formulation are compared with the collapse loads predicted by the rigid circular arch and by a discrete element analysis, as well as the stiffness of the linear elastic circular arch in the case when there are no cracks. The preliminary results of a relatively slender arch show that the collapse load is affected by elastic deformation when the Young's modulus is below 10 GPa. However, further work is needed to investigate why the stiffest arches with a Young's modulus above 80 GPa had a collapse load slightly higher than that of the rigid arch, which should not be possible. Paper i proceeding 2026-09-21 16:48:22 https://research.chalmers.se/publication/554066 2026-09-21T16:48:22Z Stream processing has become a fundamental data processing mechanism in modern edge-to-cloud systems, enabling the transformation of continuous data streams into timely aggregated results and actionable insights, e.g., in traffic or energy consumption monitoring. In practice, deploying and executing streaming applications, referred to as continuous queries, is often challenged by fluctuating workloads, changing resource availability, and varying application requirements. For example, a traffic monitoring system running on a roadside device might observe a surge in events reported by cars and, as a result, might need to produce outputs more frequently to support timely control decisions, despite limited computational power. This necessitates that Stream Processing Engines (SPEs) -- software systems for executing continuous queries on unbounded data streams -- dynamically adjust their behavior at runtime rather than relying on fixed configurations. Yet existing SPEs offer limited support for such adaptive capabilities, and even core operations such as data aggregation are no exception.This thesis addresses this limitation by exploring how stream Aggregates -- stateful operators that summarize streaming data -- can be relaxed at runtime to adaptively trade performance against resource consumption and output guarantees. On the one hand, stream Aggregate states can vary significantly and shift over time in response to variations in the incoming data, and not all states are accessed with equal frequency; therefore, those states updated infrequently could be compressed. However, deciding when and what to compress is not trivial, as the optimal trade-off between memory savings and processing overhead varies with workload. We thus design an on-demand compression mechanism that uses Reinforcement Learning (RL) to dynamically tune Aggregate state compression levels at runtime, balancing memory consumption and processing efficiency under a target latency threshold, and identify policies that balance feedback timeliness and learned quality. On the other hand, Aggregates are defined by two key parameters -- window advance (the output frequency) and window size (the interval length) -- which typically remain fixed throughout execution, limiting their ability to adapt to changing workloads and resource conditions. Therefore, we support dynamic reconfiguration of both parameters at runtime, allowing analysts to specify a set of acceptable advances and sizes to trade performance and guarantees via weaker (at-most-once) or stronger (exactly-once) reconfiguration semantics. We provide alternative reconfiguration strategies for both in-order and out-of-order tuple arrival models, and empirically show that the approach matches fixed-configuration baselines' performance while supporting reconfiguration in negligible time. Licentiatavhandling 2026-09-21 16:46:23 https://research.chalmers.se/publication/553698 2026-09-21T16:46:23Z Despite the efforts devoted to the identification of new electrode materials with higher specific capacities and electrolyte additives to mitigate the well-known limitations of current lithium-ion batteries, this technology is believed to have almost reached its energy density limit. It suffers also of a severe safety concern ascribed to the use of flammable liquid-based electrolytes. In this regard, solid-state electrolytes (SSEs) enabling the use of lithium metal as anode in the so-called solid-state lithium metal batteries (SSLMBs) are considered as the most desirable solution to tackle the aforementioned limitations. This emerging technology has rapidly evolved in recent years thanks to the striking advances gained in the domain of electrolyte materials, where SSEs can be classified according to their core chemistry as organic, inorganic, and hybrid/composite electrolytes. This strategic review presents a critical analysis of the design strategies reported in the field of SSEs, summarizing their main advantages and disadvantages, and providing a future perspective toward the rapid development of SSLMB technology. Reviewartikel 2026-09-21 16:45:01 https://research.chalmers.se/publication/554061 2026-09-21T16:45:01Z Halides are potential electrolytes for Li metal solid state batteries owing to their combination of high ionic conductivity, ductility and electrochemical stability against oxidation. However, their reactivity with the Li metal electrode may result in the formation of secondary compounds hindering their practical utility in terms of cycling performance as key indicator in battery operation. In this work, we investigate the high performance of symmetric cells with Li3YCl4Br2 halide and bare Li-metal electrode, able to withstand 1000 h of Li electrodeposition-dissolution with an overpotential as low as 46 mV. Through a comprehensive analysis employing physico-chemical and electrochemical characterizations, complemented by computational methodologies, we unravel the dynamics of the complex of the Li/halide interface and its evolution during cycling. The reactivity between Li3YCl4Br2 with metallic Li results in the reduction of the halide into LiCl, LiBr and Y metal. Surprisingly, during cycling, those secondary products from the reduction of the halide build a structured solid electrolyte interphase, containing a Y-rich electronic conductive and LiCl and LiBr ionic conductive layers. The particular chemistryand robustness of this solid electrolyte interphase exhibiting a mixed ionic and electronic conductivity appears to be responsible for the outstanding cycling stability. Artikel i vetenskaplig tidskrift 2026-09-21 16:44:14 https://research.chalmers.se/publication/554063 2026-09-21T16:44:14Z Aqueous electrolytes containing sulfuric acid and organic electrolytes made by dissolving quaternary ammonium salts in propylene carbonate have long been used as electrolytes in supercapacitors. In the organic electrolyte system, acetonitrile was later also used as a solvent. This paper will describe more recent electrolytes for supercapacitors, including those in the research and development stage. The main electrolytes discussed here are novel-solvent-based electrolytes, highly concentrated electrolytes, deep eutectic electrolytes, polymer gel electrolytes, and solid-state electrolytes. The advantages as well as problems of these electrolytes are discussed, and the prospects of electrolytes for supercapacitors are presented. Reviewartikel 2026-09-21 16:43:40 https://research.chalmers.se/publication/554062 2026-09-21T16:43:40Z In this work the effect of encapsulating a standard liquid electrolyte (1 M LiFSI in EC:DMC) into a polymer matrix for Li-ion capacitors pre-lithiated using Li2C4O4 sacrificial salt is presented. The polymer precursor is added in liquid state, which facilitates the integration in already existing cell manufacturing lines and is polymerized in situ at 60 °C after cell assembly. The application of a gel polymer electrolyte (GPE) is demonstrated to have many benefits such as lowered risk of electrolyte leakage, reduced flammability, improved high-temperature stability and high-temperature performance. The introduction of the polymer component is suggested to improve the stability of the solid electrolyte interface (SEI), enabling capacity retention of >95 % after 1200 h floating at 60 °C first (600 h) and 70 °C after (600 h). The increased performance at higher temperatures over room temperature is explained by an increased capacity of the hard carbon (HC) negative electrode together with an improved ionic conductivity of the GPE. Further increasing the operational temperature window of the LIC to 80 °C enables additional 600 h floating, demonstrating the feasibility of the GPE concept to improve high temperature stability and performance of commercial Li-ion capacitors, importantly, without sacrificing room temperature operation. Artikel i vetenskaplig tidskrift 2026-09-21 16:37:57 https://research.chalmers.se/publication/554065 2026-09-21T16:37:57Z The paper discusses the future of ship stability as a scientific and engineering discipline, in view of the possibilities for making progress in the “conventional” ship stability topics by employing advanced numerical tools (such as CFD), artificial intelligence techniques (such as machine learning), high-performance computing, increased connectivity, and unprecedented availability of the stability-relevant data. The paper also addresses the emerging ship stability issues prompted by energy transition and autonomous shipping, which are not in the focus of the maritime research community and, at the same time, lack adequate regulatory support. The present view of the evolution of ship stability is provided in the conclusions. Paper i proceeding 2026-09-21 15:33:57 https://research.chalmers.se/publication/545498 2026-09-21T15:33:57Z The weak binding and spatially extended neutron densities characteristic of drip-line nuclei give rise to a distinctive low-energy dipole response. The drip-line nucleus He8 is the most neutron-rich bound nucleus with a mass-to-charge ratio of A/Z=4. We measure the dipole response of He8, including for the first time the four-neutron decay channel. A total dipole strength of ∑B(E1)(E∗<15 MeV)=0.95(16)e2 fm2 and a dipole polarizability of αD=0.61(1) fm3 are extracted from the differential Coulomb-excitation cross section and compared to state-of-the-art theoretical calculations employing coupled cluster and three-body approaches. We find that the dipole continuum is dominated, even at high excitation energies well above the 4n decay threshold, by two-neutron emission, pointing to a He6+2n structure of the excited dipole mode. No indication was found for a 4n final-state correlation, while pronounced nn and He6-n final-state correlations are apparent. Artikel i vetenskaplig tidskrift 2026-09-21 15:16:34 https://research.chalmers.se/publication/552152 2026-09-21T15:16:34Z The paper analyses the state-of-the-art and future perspectives by reviewing a selection ofpapers published in STAB2015, ISSW2016 & 2017. These works have been organized in differentsections, according to the main thematic areas of research, covering intact and damage stability,regulatory issues including probabilistic approaches, advanced numerical methods for ship motionand stability failure prediction including roll damping, operational issues related to ship stabilityand environmental modelling. Furthermore, the challenges of feeding back to the educationalprocess the research conducted are discussed. This review paper is a joint effort within the SRDC(Stability R&D Committee). Paper i proceeding 2026-09-21 14:27:04 https://research.chalmers.se/publication/505757 2026-09-21T14:27:04Z Introduction Understanding population-level variation in bone size and shape is important for general biomechanics, clinical assessments, and for developing heterogeneous human body models used in safety restraint design. Thoracic injuries are common in severe motor vehicle crashes, and although rib fractures are frequently studied, sternal fractures also occur in these scenarios. This study aimed to investigate how demographic factors-sex, age, stature, and BMI-relate to variations in sternal size, shape, and cortical thickness, all important factors for fracture tolerance.Methods Computed tomography scans from 56 female and 58 male subjects were segmented using a machine-learning-based pipeline to extract sternal geometries. A template mesh was fitted to each subject using landmarking and surface-fitting techniques, and cortical bone mapping was applied to estimate cortical thickness. Principal component analysis (PCA) was then used to quantify variation in shape and thickness. Multivariate linear regression models were created for each principal component (PC) using the demographic predictors and first-order interaction terms.Results The leading principal components captured variation in cortical thickness distribution, overall size, the manubriosternal joint, and the positions of the sternocostal joints. There were significant demographic trends for five PCs, which explained 39.4% of the total variance in the PCA. When using the significant regression trends to predict sternal shape and cortical thickness in the original sample, R 2-values were 0.22 for spatial coordinates and 0.07 for cortical thickness, indicating substantial unexplained individual variation. The mean sternum had an average cortical thickness of 0.92 mm.Discussion Predictor-isolation analyses indicated that sex exerted a stronger influence on overall size than stature. Further, sternal width increased with age, and individuals with higher BMI tended to exhibit slightly greater cortical thickness. While regression models were developed to explore demographic associations, the predictive performance was limited, indicating that the model should primarily be interpreted as a descriptive representation of population-level variation rather than a predictive tool. Artikel i vetenskaplig tidskrift 2026-09-21 13:19:11 https://research.chalmers.se/publication/553784 2026-09-21T13:19:11Z Supercooled liquid water often persists in mixed-phase clouds for hours to days, even though a simple, well-mixed Wegener-Bergeron-Findeisen model predicts rapid depletion of liquid water in the presence of ice. The persistence is well documented, but the relative importance of the maintaining mechanisms remains uncertain. This model intercomparison study addresses this issue by comparing results from 10 model configurations against observations from the Pi Cloud Chamber at Michigan Technological University, which produces cloudy Rayleigh-Bénard convection. To simplify the problem, we exclude ice-nucleating particle processes and assume that the ice crystals are spherical. Each model was first tuned to reproduce the observed steady liquid-cloud state and then run with ice injected at a range of rates. The evolution of spherical ice crystals is consistent across models, but differences emerge in the liquid phase. Most models that simulate the full chamber tend to retain liquid droplets for the entire simulation, because persistent supersaturation near the bottom activates new droplets that replace those that mix into the core and evaporate. In contrast, models that assume a well-mixed domain, exclude the near-wall region, or use coarse resolution do not sustain droplets and undergo complete glaciation. Models that use Lagrangian microphysics expose particles to greater supersaturation variability than bin schemes. Overall, these results demonstrate that liquid persistence in mixed-phase clouds is highly sensitive to the representation of spatial heterogeneity and mixing, and provide guidance for improving microphysical parameterizations in atmospheric models. Artikel i vetenskaplig tidskrift 2026-09-21 13:17:40 https://research.chalmers.se/publication/554037 2026-09-21T13:17:40Z Bicyclists are the most seriously injured road user in Sweden. For fatal crashes car-to-bicycle is themost common configuration and the most frequently injured body part is the head. However, the most frequentcrash configuration is single-bicycle with the shoulder as the most injured body part. Shoulder injuries are non-fatal but often result in long-term consequences. Shoulder-thorax-protection for bicyclists is underdeveloped.The objective of the study was to evaluate the protection provided by a conceptual airbag vest. Twenty-four car-to-bicycle and eight single-bicycle crash simulations with a Human Body Model rider (SAFER HBM) were carriedout, varying impact speed and impact angle. The airbag was coupled with the SAFER HBM and the shape coversthe outer surface of the torso, particularly the shoulder and thorax. Shoulder peak contact force, risk of mildtraumatic brain injury (mTBI), Head Injury Criterion (HIC), and the risk for two or more fractured ribs wereassessed for bicyclists with and without an airbag vest. The airbag vest showed potential for shoulder protection.In single-bicycle crash simulations, a substantial reduction in shoulder contact force was observed. Additionally,the airbag vest showed potential to reduce the risk of mTBI and HIC, particularly in single-bicycle crash simulations.For all evaluated loadcases, the risk of fractured ribs remained low, both with and without the airbag vest. Thedetachment and position upward next to the head provided unexpected head injury protection and could beincorporated deliberately in future designs of the airbag vest. Shoulder contacts with stiff elements of the carproduced the highest shoulder contact forces and biggest challenge for the airbag vest design. These contactscould be further simplified into worst-case component testing to aid the development of better protection. Atissue-based injury risk prediction is desirable as injury prediction capability of human body model need to bedeveloped in the future. Nevertheless, the conceptual airbag vest substantially reduced loading to the shoulderand had protective effects on head and thorax. Paper i proceeding 2026-09-21 12:49:57 https://research.chalmers.se/publication/554060 2026-09-21T12:49:57Z Projektets syfte var att integrera en eller flera GPT-baserade språkmodeller i en befintlig molntjänst för kvalitetssäkring och egenkontroll i byggprojekt. Arbetet genomfördes under perioden 1 september 2023 till 31 augusti 2024 av Incoord, Robert Dicksons stiftelse, Chalmers tekniska högskola, Högskolan i Halmstad och Elicit. Metoden kombinerade behovsanalys, fallstudie och prototypbaserad utveckling med iterativa tekniska tester och användartester.Projektet resulterade i en fristående API-tjänst utvecklad med Python och FastAPI som kopplades till den befintliga webbapplikationen. Generativ AI implementerades genom två funktioner: 1) analys av projektbeskrivningar 2) generering av projektspecifika förslag till egenkontroller utifrån projekt, underprojekt, disciplin och användarroll. Arkitekturen utformades så att AI-funktionerna kan aktiveras eller inaktiveras utan att applikationens kärnfunktioner påverkas.Testerna visade att den tekniska integrationen fungerade och att användarna upplevde nytta av AI-stödet. Resultaten visar samtidigt att AI-genererade förslag behöver granskas av en person med relevant sakkunskap. Svarskvaliteten kan variera och lösningen är beroende av externa AI-tjänster för tillgänglighet och databehandling. Fortsatt utveckling bör därför prioritera kvalitetssäkring, spårbarhet, informationssäkerhet, tydlig ansvarsfördelning och ytterligare validering i representativa byggprojekt. Projektets huvudsakliga slutsats är att generativ AI kan skapa värde som en avgränsad stödfunktion i en befintlig applikation förutsatt att användningsfallet är tydligt och att mänsklig kontroll är en integrerad del av arbetsflödet. Rapport 2026-09-21 12:14:59 https://research.chalmers.se/publication/554059 2026-09-21T12:14:59Z A major challenge in physics-informed machine learning is to understand how the incorporation of prior domain knowledge affects learning rates when training data is not independent and identically distributed. Focusing on empirical risk minimization with physics-informed regularization, we derive complexity-dependent bounds on the excess risk in probability and in expectation. We prove that, when the physical prior information is aligned, the learning rate improves from the (slow) Sobolev minimax rate to the (fast) optimal i.i.d. one without sample-size deflation due to data dependence. Paper i proceeding 2026-09-21 10:55:29 https://research.chalmers.se/publication/554057 2026-09-21T10:55:29Z Parallelism is inherent in most problems but due to current programming models and architectures which have evolved from a sequential paradigm, the parallelism exploited is restricted. We believe that the most efficient parallel execution is achieved when applications are represented as graphs of operations and data, which can then be mapped for execution on a modular and scalable processing-in-memory architecture. In this paper, we present PHOENIX, a general-purpose architecture composed of many Processing Elements (PEs) with memory storage and efficient computational logic units interconnected with a mesh network-on-chip. A preliminary design of PHOENIX shows it is possible to include 10,000 PEs with a storage capacity of 0.6GByte on a 1.5cm2 chip using 14nm technology. PHOENIX may achieve 6TFLOPS with a power consumption of up to 42W, which results in a peak energy efficiency of at least 143GFLOPS/W. A simple estimate shows that for a 4K FFT, PHOENIX achieves 117GFLOPS/W which is more than double of what is achieved by state-of-the-art systems. Paper i proceeding 2026-09-21 10:49:37 https://research.chalmers.se/publication/253798 2026-09-21T10:49:37Z During cardiopulmonary bypass surgery, a key role is played by the oxygen and carbon-dioxide exchange between the body and the oxygenator. In this work, we present a preliminary mathematical model of this gas exchange and show some results based on experimental data in piglets. Paper i proceeding 2026-09-21 10:37:49 https://research.chalmers.se/publication/554056 2026-09-21T10:37:49Z This paper proposes a safe active learning algorithm in which a model predictive controller optimises system operation and simultaneously explores informative dynamics to learn model parameters, all while ensuring that safety constraints are satisfied. The recursively updated model consists of a recurrent neural network with a Bayesian last layer. The algorithm is complemented with guarantees of recursive feasibility, safety, and finite termination of exploration. The proposed framework is validated in simulation on a benchmark energy system, demonstrating that the algorithm ensures a finite exploration of the system dynamics while optimising the operation and satisfying physical constraints. Paper i proceeding 2026-09-21 10:26:55 https://research.chalmers.se/publication/554055 2026-09-21T10:26:55Z In 2025, the Year of Quantum Science and Technology (https://quantum2025.org/), we celebrate a century of quantum mechanics, witnessing a surge in activities that illuminate its inherent strangeness and drive technological innovation. Superconductivity, discovered 114 years ago, stands as a prime example, offering direct and compelling evidence of macroscopic quantum phenomena. Beyond its ability to conduct immense currents without loss, superconductivity reveals the quantum realm operating on a scale we can directly observe and manipulate. The macroscopic quantum coherence, where an ensemble of particles is described by a single wave function, leads to remarkable consequences: dissipation-less current and flux quantization-the basic properties exploited in superconducting quantum circuit fabrication. This Roadmap has been inspired by intensive discussions and collaborations emerging from the European Cooperation in Science & Technology COST-Action CA21144 (SuperQuMap-Superconducting Nanodevices and Quantum Materials for Coherent Manipulation). The aim of the COST Action SuperQuMap is to establish a strong European network centered on macroscopic quantum behavior in superconductors, bringing together groups of different backgrounds and more than 30 countries. The roadmap outlines the network's concrete activities, driving advancements in superconductor-based quantum technologies and charting future directions. Spanning fundamental research to practical applications, the roadmap incorporates insights from industry partners developing quantum computation. It begins by exploring quantum materials, highlighting how topology and electronic correlations could catalyze a quantum leap in technology. We then delve into manipulating the superconducting phase, leveraging advancements in magnetism, 3D fabrication, and tunable correlations. Further, we showcase the advanced microscopy techniques-such as angle-resolved photoemission spectroscopy and scanning probes-used to visualize quantum behavior. Finally, and crucially, we detail the quantum devices developed within the network, and their transformative impact on modern quantum computing approaches. Reviewartikel 2026-09-21 09:40:57 https://research.chalmers.se/publication/550849 2026-09-21T09:40:57Z We investigate phase-coherent quantum transport in nanoscale Al-Bi2Se3-Al nanoribbon Josephson junctions by combining normal-state conductance spectroscopy with a junction-length-dependent study of Josephson transport. Differential conductance maps versus bias and gate voltage reveal Fabry-Perot interference, whose periodicity matches the nanoribbon width, consistent with transverse quantization and quasi-ballistic surface-state trajectories in 430 nm wide devices. A systematic investigation of the characteristic voltage I c R n as a function of junction length L exhibits a clear plateau for L <= 500 nm, indicative of a short ballistic contribution to the Josephson transport, and decreases for longer junctions as diffusive transport dominates. Together, Fabry-Perot interference and Josephson transport measurements provide complementary, channel-selective evidence for quasi-ballistic surface-state transport persisting over several hundred nanometers in hybrid topological insulator nanostructures. These results demonstrate the potential of Bi2Se3 nanoribbon Josephson junctions as a nanoscale platform for phase-coherent superconducting electronics, topological quantum computing architectures, and topological spintronic devices. Artikel i vetenskaplig tidskrift 2026-09-21 09:39:24 https://research.chalmers.se/publication/552910 2026-09-21T09:39:24Z Thermomigration (TM) is an ex-situ technique that enables tuning of the transport properties in YBa (Formula presented) (Formula presented) Cu (Formula presented) (Formula presented) O (Formula presented) (Formula presented) -based nanostructures by driving oxygen migration through local Joule heating. We apply an AC current bias to conduct TM on grooved Dayem nanoBridge (GDB)-based Superconducting Quantum Interference Devices (SQUIDs) and investigate its impact on transport characteristics via current–voltage and voltage modulation measurements. By adjusting both the timing and amplitude of the applied AC bias, we identified two distinct TM modes: a ‘hard’ regime, characterized by high-bias, rapidly repeated AC-current bursts that reduce the critical current, and a ‘soft’ regime, in which lower-bias bursts separated by longer waiting times selectively tune the differential resistance at the operating point. Both tuning methods significantly enhance device performance, with voltage modulation improvements higher than a factor 5. Our findings confirm TM as a powerful post-fabrication tool for optimization of the transport properties of GDB-based high temperature superconductor SQUIDs. Artikel i vetenskaplig tidskrift 2026-09-21 09:38:16 https://research.chalmers.se/publication/552890 2026-09-21T09:38:16Z The InP high-electron-mobility transistor (HEMT) is indispensable for low-noise amplifiers (LNAs) in radio astronomy and quantum computing. The composition of the InxGa1−xAs channel in the InP HEMT is known to influence the LNA noise performance. However, the various physical mechanisms responsible for noise generation are not fully characterized and understood. Here, we investigate the InxGa1−xAs channel noise from 4 K to 300 K for 100-nm gate-length InP HEMTs with channel indium content of 53%, 60% and 70%. Channel noise was quantified by extracting the equivalent drain noise temperature Td using both on-wafer and LNA-based measurements, covering 40-300 K and 4-40 K, respectively. The 60% indium channel InP HEMT exhibited the lowest channel noise across the full temperature range. The Td extracted from on-wafer characterization was found to obey a parabolic temperature dependence which predicted the Td at 4 K for all InP HEMTs in good agreement with LNA-based measurements. By expressing the channel noise as the sum of one thermal and one excess noise term, it was found that the former increased linearly with ambient temperature and dominated at 300 K. The channel noise at 4 K was determined by the excess noise term and exhibited a non-monotonic dependence on the channel indium content in the InP HEMT. The results suggest that the excess noise in the InxGa1−xAs channel originates not only from temperature-independent shot noise but also from impact ionization and real-space transfer noise. Artikel i vetenskaplig tidskrift 2026-09-20 15:51:03 https://research.chalmers.se/publication/554033 2026-09-20T15:51:03Z The electrification of heavy commercial vehicles offers opportunities beyond replacing conventional powertrains with batteries and electric machines. In particular, electric axles enable propulsion, braking, and motion control to be distributed and coordinated across the vehicle. This thesis investigates how modular electric axle powertrains can be designed and controlled to reduce operational costs while maintaining safe, robust, and predictable vehicle behaviour.A modular powertrain architecture is proposed in which different axles or axle groups can be assigned distinct functions. A dedicated cruise axle is tailored for efficient steady-state highway operation, while a startability axle provides high traction at low speeds and on demanding grades. The joint selection of motor ratings and gear ratios, together with coordinated axle operation, is investigated to identify powertrain configurations that satisfy vehicle motion requirements while improving energy efficiency and driving range.Building on this modular electric axle architecture, the thesis then addresses the coordination of multiple electric powertrains and friction brakes. Control allocation methods are developed to distribute wheel-torque demands among redundant actuators while achieving the requested vehicle motion and minimising operational losses. In contrast to conventional heuristic weighting, the proposed formulations represent actuator losses as physically based cost rates, providing a direct connection between control decisions and vehicle operating cost. Tyre-friction constraints are incorporated to account for the coupled longitudinal and lateral demands during vehicle manoeuvres.For demanding driving conditions, vehicle-level motion control is combined with lower-level actuator coordination. A model predictive control-based force generator regulates longitudinal and yaw responses within prescribed operating limits, while subsequent control allocation distributes the required forces among the available actuators. The developed methods are evaluated under conditions including low-friction surfaces and combined braking and cornering, with emphasis on stability, path tracking, and predictable vehicle response.Finally, the optimisation framework is extended beyond energy consumption by incorporating tyre wear alongside actuator losses. The results demonstrate that modular electric axles, combined with optimisation-based design and control, can provide new means of improving energy efficiency, reducing operating costs, and maintaining safe and predictable motion in heavy electric vehicles Doktorsavhandling 2026-09-20 13:23:28 https://research.chalmers.se/publication/553997 2026-09-20T13:23:28Z Semiconductor lasers are compact, coherent light sources that have enabled or transformed a wide range of applications since their invention in the 1960s. They have rapidly matured at visible and infrared wavelengths; however, their progress at ultraviolet-C (UV-C, λ<280 nm) wavelengths has been considerably slower. To date, continuous-wave electrically driven UV-C edge-emitting lasers have been reported, but vertical-cavity surface-emitting lasers have only been demonstrated under optical pumping. Photonic-crystal surface-emitting lasers (PCSELs), on the other hand, are a new type of semiconductor laser and have recently attracted attention for their unique optical properties. They combine watt-level single-mode output powers and circularly symmetric beams with low divergence angles below 1°. PCSELs have demonstrated strong performance at visible and infrared wavelengths, but were not realized in the UV-C before this work.In this thesis, we demonstrate the first UV-C PCSELs operating at room temperature under pulsed optical pumping. We investigate the influence of photonic crystal design parameters, including hole filling factor, lattice constant, etch depth, and lateral photonic crystal size, on lasing characteristics and address the challenges in achieving lasing under electrical injection. Our results indicate that the lasing threshold of PCSELs decreases with increasing device size. Therefore, a larger size is beneficial for low-threshold operation. However, for large sizes (>100 μm), current injection across the device area is challenging due to the poor electrical conductivity of Al-rich AlGaN, which may prevent lasing. To reduce the current spreading distance and improve current uniformity, we introduce a ring-shaped photonic crystal design, where a central circular region is etched to accommodate an additional n-contact. These findings help better understand III-nitride-based UV-C PCSELs and open a pathway toward future electrically driven devices. Doktorsavhandling 2026-09-20 10:52:56 https://research.chalmers.se/publication/554032 2026-09-20T10:52:56Z Bismuth vanadate (BiVO4) is one of the most promising photoanode materials for water splitting, yet its intrinsic oxygen evolution reaction (OER) performance is limited. Here, we employ hybrid density functional theory calculations to investigate the synergistic effects of nitrogen doping and oxygen vacancy formation on BiVO4 for the OER. We analyze two OER mechanisms, the traditional single-site adsorption evolution mechanism (AEM) and the dual-site bridging mechanism (DSBM), to understand the enhanced catalytic activity observed experimentally. Our results show that nitrogen doping on the surface, combined with the creation of a vanadium active site through oxygen vacancy, significantly reduces the OER overpotential from 1.44 V in pristine BiVO4 to 0.93 V (AEM) and 1.16 V (DSBM). Besides, the nitrogen dopants on the surface alter the local acid-base chemistry: proton adsorption on nitrogen becomes 0.52 eV more favorable than on oxygen, and water dissociation is 0.31 eV easier at the V site than at the Bi site. By offering low-energy proton-binding sites, nitrogen stabilizes key intermediates and favors formation of a stable O–O dimer, producing a pronounced reduction in overpotential. These findings highlight that the effective defect engineering strategies can significantly enhance the overall performance of BiVO4- based photoanodes in operational photoelectrochemical systems. Artikel i vetenskaplig tidskrift 2026-09-19 21:29:57 https://research.chalmers.se/publication/548865 2026-09-19T21:29:57Z Transition metal oxides, such as BiVO4, have attracted significant attention for their potential in photoelectrochemical water-splitting. BiVO4, a model material in this area, is prone to charge localization in the form of small polarons. Recently, self-trapped excitons (STEs) in BiVO4 have been experimentally observed, but their precise nature remains elusive. In this study, we employ time-dependent density functional theory (TD-DFT) with a nonempirical PBE0(α) hybrid functional to investigate the localization, stability, and optical properties of STEs in BiVO4. Our results reveal two distinct localized exciton configurations with comparable energies. We show that the emission from a single STE configuration leads to multiple peaks in the emission spectrum, originating from different types of internal transitions. The positions of peaks in the calculated optical spectra are in good agreement with experimental observations. Artikel i vetenskaplig tidskrift 2026-09-19 21:29:30 https://research.chalmers.se/publication/547352 2026-09-19T21:29:30Z Charge localization is an important phenomenon that influences various material properties, including excited-state energetics, charge transport, catalytic activity, and recombination. As such, it has significant implications for optoelectronic and photocatalytic applications. In this Perspective, we begin by addressing the methodological challenges associated with modeling localized charges, highlighting their complexity and the need for accurate computational approaches. We then discuss how charge localization impacts the performance of solar cells and photocatalysts, providing specific examples to illustrate these effects. Connections between theoretical predictions and experimental observations are explored to underline the importance of integrating modeling and experiments. Finally, we outline future research directions, emphasizing the development of advanced methods to better capture localized charge behavior and its role in materials design. Artikel i vetenskaplig tidskrift 2026-09-19 21:29:14 https://research.chalmers.se/publication/545849 2026-09-19T21:29:14Z Although electrostatics can be incorporated into machine-learned interatomic potentials, existing approaches are computationally very demanding, limiting large-scale, long-time simulations of electrostatics-driven phenomena such as dielectric response, infrared activity, and field-matter coupling. Here, we extend the neuroevolution potential (NEP), a highly efficient machine-learned interatomic potential, to a charge-aware framework (qNEP) by introducing explicit, environment-dependent partial charges. Each ionic partial charge is represented by a neural network as a function of the local descriptor vector, analogous to the NEP site-energy model. This formulation enables the direct prediction of the Born effective charge tensor for each ion and, consequently, the polarization. As a result, dielectric properties, infrared spectra, and coupling to external electric fields can be evaluated within a unified framework. We derive consistent expressions for the forces and virials that explicitly account for the position dependence of the partial charges. The qNEP method has been implemented in the free-and-open-source GPUMD package with support for both Ewald summation and particle-particle particle-mesh treatments of electrostatics. We demonstrate the accuracy and efficiency of the qNEP approach through representative applications to water, Li7La3Zr2O12, BaTiO3, and a magnesium-water interface. These results show that qNEP enables accurate atomistic simulations with explicit long-range electrostatics, scalable to million-atom systems on nanosecond time scales using consumer-grade GPUs. Artikel i vetenskaplig tidskrift 2026-09-19 21:28:45 https://research.chalmers.se/publication/551952 2026-09-19T21:28:45Z The unique electronic properties of CsGeX 3 perovskites (X = Cl, Br, I) make them promising candidates for nonlinear optical applications. Understanding charge localization is needed to fully understand their physical and electronic behavior. Here, we perform a theoretical investigation of electron and hole polaron formation, and self-trapped exciton binding in CsGeX 3 using hybrid density functional theory. We find that polaron stability decreases from Cl to I. In particular, single-electron polarons form highly favorably in CsGeCl3 and CsGeBr3, whereas single-hole polarons can only be formed in CsGeCl3. Double electron polarons are energetically favorable across the series. In addition, CsGeCl3 and CsGeBr3 exhibit stable self-trapped exciton configurations. These findings constitute a basis for understanding polaronic effects on the electronic properties of CsGeX 3 perovskites and open up access to their optimization in nonlinear optical applications. Artikel i vetenskaplig tidskrift 2026-09-19 21:28:28 https://research.chalmers.se/publication/550092 2026-09-19T21:28:28Z