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Comparative Analysis of Plasma-Assisted Combustion and Cracking Strategies for Ammonia Flame Stabilization
No full textThe urgent need to transition from carbon-intensive fossil fuels to sustainable energy carriers has positioned ammonia as a promising carbon-free fuel due to its high energy density, existing infrastructure, and potential for green production via renewable hydrogen. However, ammonia combustion faces critical challenges such as low burning velocity, narrow flammability limits, and high NOx emissions, which hinder its adoption in gas turbines and industrial burners. This work presents a comprehensive, energy-normalized comparison of two stabilization and performance-enhancement strategies: partial thermal cracking (10–28%
conversion to H2/N2) and nanosecond-pulsed plasma actuation (3–99 W), applied to swirl-stabilized premixed ammonia flames, evaluated both independently and
in combination. Partial thermal cracking introduces reactive hydrogen, extending the lean blow-off limit from ϕ = 0.75 to 0.55 at 10% cracking and sustaining combustion down to ϕ = 0.27 at 28% (7 m/s). This enhanced stability incurs a > 130% increase in NOx due to elevated flame temperatures and radical chemistry. Chemiluminescence imaging shows shorter, more compact flames, and flame transfer function tests reveal amplified thermoacoustic instabilities via stronger vortex–
flame coupling. When normalized by energy input, cracking extends lean blow-off limits approximately 4.5× more than plasma actuation and reduces N2O by approximately 80% at an added power ratio of 3.3, albeit with higher NOx penalties under lean conditions. Nanosecond-pulsed plasma actuation enhances combustion through kinetic, thermal, and transport effects at low energy cost. At 99 W, plasma extends the lean blow-off limit by approximately 10%, reduces N2O by 30%, and eliminates NH3 slip at 48 W. NOx emissions respond in a non-monotonic manner, rising by up to 20% at ϕ = 0.8 but decreasing by approximately 18% near stoichiometry, due to a voltage-dependent shift in NH2/NH versus OH radical populations. Plasma efficacy is limited by shock wave-induced gas expansion, which increases the local strain rate. Combining 10% cracking with plasma yields the greatest lean-limit extension
and the most pronounced lowering of flame center of gravity in lean mixtures, indicating improved plasma–flame coupling. These benefits vanish above approximately 20% cracking, and stability degrades at 28%. In combined operation, plasma generally elevates NOx except under extremely lean conditions, where it still suppresses NH3 slip without large NOx penalties. Flame transfer function assessments show that plasma can be tuned to either amplify or attenuate thermoacoustic gain, highlighting the complex interplay between electrical actuation and fuel reactivity. This first side-by-side evaluation of fuel-cracking and plasmaassisted
approaches provides critical insights for next-generation low-carbon combustion systems
A novel photovoltaic/thermal (PVT) system using nano-enhanced micro-encapsulated PCM slurry for steam production: A numerical study
No full textAs industries reliant on steam-based processes strive to reduce fossil fuel consumption and carbon emissions, interest in renewable technologies, particularly photovoltaic/thermal (PVT) systems that generate both thermal and electrical energy, is increasing. However, the limited thermal performance of PVT systems remains a key barrier. Traditional working fluids, such as water, nanofluids, and phase change material (PCM) slurries, exhibit low thermal conductivity, poor temperature regulation, and inefficient heat storage. To address these issues, a novel working fluid incorporating graphene oxide (GO) nanoparticles into microencapsulated PCM (MPCM) slurry is proposed. The integration of GO nanoparticles not only enhances the dispersion stability of the MPCM slurry but also significantly increases its thermal conductivity, leading to improved heat dissipation from PV cells. A comprehensive CFD investigation is conducted using ANSYS Fluent 2021, employing an Eulerian–Eulerian multiphase model to simulate the three-phase flow. In this model, water serves as the primary phase, while GO nanoparticles and MPCM function as secondary dispersed phases. The results demonstrate that increasing the GO volume fraction from 0 to 0.005 reduces average PV cell temperatures by up to 5°C at 40°C. Additionally, the nano-enhanced MPCM slurry achieves a thermal efficiency of 88.1 % and an electrical efficiency of 10.3 %. It is also found that using MPCM slurry as the working fluid, a 15 % volume fraction of MPCM with a melting point of 40°C achieves the highest thermal efficiency of 90.1 %, outperforming water by 20.1 % and surpassing previous studies on MPCM slurry and nanofluids
Pathological drivers of coral diseases across the Arabian Peninsula
No full textIncreasing trends of coral mortality are a challenge to coral reef management worldwide, and a need exists to identify the causes and pathways involved. Pathology is useful to help decipher potential causes of mortality in animals, because it illuminates agents associated with lesions and gives insights on the nature of how a host responds to said agents. To better understand the nature of threats facing corals in the Arabian Peninsula, we performed gross and microscopic pathology on corals from Saudi Arabia, Qatar, and the United Arab Emirates. Among 321 coral fragments examined from 21 genera, tissue loss was the most common lesion seen in 31% of samples, reflecting its widespread presence on reefs from the Arabian Peninsula. Histologically, 68% of lesions exhibited necrosis, predominantly in the basal body wall and surface body wall. Endolithic filamentous microalgae and sponges, originating from the skeleton, were associated with 57% and 39% of lesions, respectively, and were often linked to necrosis and hyaline membrane formation. Cell-associated microbial aggregates and coccidia were detected mainly in Acropora, Pocillopora, and Porites but were not associated with adverse host response. Notably, 69–100% of fragments showing lesions were female likely reflecting the temporal reproductive life history of corals in the region. Our findings highlight endolithic organisms as major contributors to coral tissue degradation in the Arabian Peninsula. Future studies might focus on drivers of endolithic microalgal and sponge dynamics in the region and their role in coral reef health.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Aine Hawthorn reviewed previous versions of this manuscript
Predictive Model of Sediment Distribution and Stratigraphic Traps along Salt Structures: Insights from Outcrop Analogs
No full textStratigraphic traps in salt controlled minibasins are attractive exploration targets for the hydrocarbon industry and for Carbon Capture Storage projects. However, predicting sediment dispersal patterns and thus, stratigraphic traps along salt structures is a major challenge. In addition to classic controlling factors for sediment supply and distribution (eustasy, tectonics, climate) the interplay with growing salt structures adds another level of complexity. Drastic spatial facies change very often occur at very small distances (<250m), especially near the salt structure. In order to characterize in great detail reservoir facies distribution inside salt controlled minibasins, we have compiled and synthetized sedimentological and stratigraphical data from world-class outcrop analogs (i.e. Sivas basin, Turkey; the Paradox basin, United States; the southern Pyrenees, Spain; La Popa basin, Mexico). This study highlights remarkable tendencies that enable to link specific halokinetic geometries with a typical sediment distribution. A new model is proposed with improved prediction capacity of sediment distribution and stratigraphic trap occurrence using diagnostic halokinetic geometries
Multi-Dimensional Deconvolution as a Framework for Processing and Targeted Imaging - A Comparison of Redatuming Approaches
No full textAcross many applications in seismic processing and imaging, multi-dimensional deconvolution (MDD)
has gained much traction, particularly in the context of processing ocean bottom (OB) data. Leveraging
matrix-free convolutional operators with efficient numerical optimisation, we approach MDD as a
general framework. As examples in the context of processing OB data, here we discuss and compare
receiver-side MDD and source-side MDD: The former redatums the survey to the receiver datum, while
the latter redatums it to the source surface – both without free-surface effects. For reservoir imaging and
monitoring, we discuss target-oriented redatuming (TOR) by MDD, which in turns relies on input
wavefields resulting from a prior redatuming step, such as wavefield injection or Marchenko-based
approaches. Using OB data from the Volve field, we compare source- and receiver-side MDD as
alternatives to processing OB data, where we observe both of the surface-based approaches yield goodquality, comparable results in estimating responses and corresponding depth images without freesurface effects, with the source-side method showing increased robustness to increased receiver spacing.
When comparing depth imaging results, we observe that TOR by MDD also delivers comparable images
to either surface-based methods, reassuring us that such targeted imaging and monitoring approaches
are viable for our MDD framework.We thank Paolo Terenghi, Arash JafarGandomi and Lorenzo Casasanta (all Shearwater GeoServices)
for valuable discussions and input. We acknowledge Shearwater GeoServices for permission to publish
this study
Viscoelasticity, Crystallization, and Mechanical Properties of Dis-entangled UHMWPE/HDPE Melt Blends and Their Nanocomposites
No full textThis dissertation explores the potential of disentangled ultra-high molecular weight polyethylene (dis-UHMWPE) as a high-performance material for industrial applications, focusing on its melt-blending compatibility with high-density polyethylene (HDPE) and enhanced processability through nanofillers. Unlike conventional entangled UHMWPE, dis-UHMWPE exhibits much lower viscosity, enabling solvent-free melt blending with commercial HDPE. This work systematically investigates the viscoelastic, thermal, and mechanical properties of dis-UHMWPE blends and their response under nonlinear shear and extensional flow, mimicking industrial processing conditions. It also examines the role of graphene oxide (GO) in modifying the rheological and mechanical behavior of dis-UHMWPE to improve processability in melt and solid-state applications.
The first part focuses on the successful homogenization of dis-UHMWPE within an HDPE matrix using melt blending. Unlike entangled UHMWPE, dis-UHMWPE blends show a significantly lower viscosity ratio with HDPE, facilitating better dispersion and compatibility. Rheological characterizations suggest that dis-UHMWPE promotes long-short entanglements with HDPE chains, enhancing mechanical properties, showing 36% improvement in maximum stress and 39% in Young’s modulus. The molecular blending mechanism is explained using a constraint release Rouse framework, highlighting kinetic advantages over conventional entangled UHMWPE.
The second part investigates the nonlinear rheological response under transient shear and extensional flow. Shear experiments show that increasing dis-UHMWPE content enhances network stretch, increases strain at peak stress, and slows relaxation dynamics. Extensional rheology reveals strain hardening induced by flow-induced crystallization (FIC), with shish-kebab structures confirmed via SEM, WAXD, and SAXS. Finite extensibility analysis reveals that strain hardening begins at a constant strain of ~2.63, independent of dis-UHMWPE content.
The final part examines the influence of GO. Rheological investigations reveal that GO reduces the plateau modulus and induces secondary relaxation via contour length fluctuations (CLF). LAOS experiments show that GO shifts dis-UHMWPE behavior from weak strain overshoot to strain-thinning, indicating reduced entanglement density and improved alignment. In blends, GO reduces zero-shear viscosity by 70% and improves dispersion by 24% at < 0.001 wt.% GO. In solid-state tapes, GO increases draw ratio while preserving tensile properties and reducing creep.
Overall, this work demonstrates that dis-UHMWPE, especially with GO, enables advanced polyethylene blends with enhanced mechanical and processing performance
Engineering of Janus transition metal dichalcogenide bilayers as absorber materials for solar cells.
No full textJanus transition metal dichalcogenide bilayers are investigated as potential solar cell materials by first-principles calculations to identify candidates with direct band gap and type-II band alignment. The effects of the interface stacking and interface composition are explored. 11 out of the 20 examined bilayers show promising features and therefore are characterized in terms of the charge transfer, absorption spectrum, and power conversion efficiency.The research reported in this publication was supported by funding from Jouf University (JU) and King Abdullah University of Science and Technology (KAUST). For computer time, this research used the resources of the Supercomputing Laboratory at KAUST
Core Extended Conjugation in Thiophene-Based Cations Enables Open-Circuit Voltage Improvement in Inverted Perovskite Solar Cells
No full textInterface engineering plays a pivotal role in enhancing the performance and stability of perovskite solar cells (PSCs). Here, we explore the influence of core conjugation in thiophene-based ammonium cations as surface passivation agents in the inverted (p–i–n) device architecture. The increased bonding strength observed with the conjugation extension allows specific defect suppression at the perovskite/PCBM interface, confirmed by combined spectroscopic analysis and density functional theory simulations. This passivation strategy yields a remarkable increase in the device open-circuit voltage (Voc), resulting in a champion power conversion efficiency of 22.8%, compared to 20.8% in the control device. This study highlights the importance of molecular conjugation and halide choice in designing efficient surface passivation strategies for effective surface defect passivation in high-performance PSCs.The authors are thankful to The Ministero dell’Università e della Ricerca(MUR), University of Pavia, for funding through the program“Dipartimentidi Eccellenza 2023–2027”. F.T. and G.G. acknowledge support of the HERO Project_CRG11 5035.3 through King Abdullah University of Science and Technology (KAUST). G.G. and F.T. acknowledge the GOPV project (CSEAA_00011), which received funds fromBando Ricerca di Sistema—CSEA—TIPO A Piano Triennale 2019–2021Decreto direttoriale 27 Ottobre 2021 del Ministero della Transizione Ecologica; MASE-(ex MITE). Computational resources were provided by KAUST’s Supercomputing Laboratory. L.P. thanks for his PhD fellowship, co-founded by the European Union – FSE, Programma Operativo Nazionale (PON) Ricerca e Innovazione 2014−2020 (CCI2014IT16M2OP005). N.M. and P.S. acknowledge the financial support from grant nos. IM-2023−82, APVV-21−0297, and APVV-20−0111
Fate of wastewater trace organic chemicals in vegetated biofiltration systems
No full textVegetated biofiltration system (VBS) is an effective green technology for urban stormwater and greywater treatment. However, VBS is yet to be optimised for effective treatment of wastewater, particularly if it contains trace organic chemicals (TrOCs). The effect of plant species has not been addressed under TrOC wastewater loading. This study tested and evaluated the effectiveness of VBS over a one-year period in removing six TrOCs commonly found in wastewater, namely Caffeine (CAF), Paracetamol (PCM), Sulfamethoxazole (SMX), N diethyl‑meta-toluamide (DEET), Bisphenol A (BPA) and Ibuprofen (IBU). Eleven VBS configurations were tested in a year-long laboratory column study to explore the role of seven different plant species (with differing characteristic), varied soil media depths, and soil characteristics, on the fate of TrOCs in the systems. The effect of different operational conditions (e.g., dosing volume and regime) on removal efficiency was investigated. The results indicated VBS was able to maintain a high removal rate (>95 %) of CAF, BPA, and IBU throughout the experiment, followed by PCM (>79 %), SMX (50 %-80 %), and DEET (<12 %). Plant species significantly impacted the removal of SMX and DEET (p < 0.05), with C. indica as the best performer. Reducing hydraulic loading rate and decreasing daily dosing volume and frequency contributed positively to the PCM, SMX, and DEET removal rates. Noticeable accumulations of SMX, DEET, and BPA (8.2, 43.1, and 54.5 ng·g-1, respectively) were detected in the filter media, particularly within the saturated zone. Higher chemical concentrations (i.e., CAF and DEET) were found in plant root tissue than in plant shoot tissue. This study offers valuable insights into VBS's design and operational aspects for removing TrOCs.This project is funded by the Australian Research Council Discovery Early Career Researcher Award (DECRA) Project (DE210101155), as well as the Centre of Excellence for NEOM Research at King Abdullah University of Science and Technology (KAUST). The authors would also like to thank Dr. James McDonald from the Water Research Centre, School of Civil and Environmental Engineering and Guy Taseski from the School of Biological, Earth & Environmental Sciences, UNSW Sydney, for their assistance
TetraheDrone: A Fractal Tetrahedral Modular VTOL Architecture for Scalable Hybrid Flight—Design, Unified Control, and Experimental Validation
No full textModular aerial robotic systems offer adaptability, configurability, scalability, and reliability, with practical advantages in manufacture, maintenance, storage, transport, and regulation. The TetraheDrone is a structured modular vertical takeoff and landing (VTOL) unmanned aerial system built on a recursive tetrahedral architecture inspired by the Sierpi´nski tetrahedron and Alexander Graham Bell’s tetrahedral kites. Its elementary module is a tri-wing tetrahedral tailsitter without control surfaces that performs hybrid flight, transitioning between hover and fixed-wing cruise. The architecture scales from one module to large structured assemblages while preserving geometric similarity, aerodynamic efficiency, and
controllability. A unified control methodology maps any assemblage’s actuation onto eight abstract signals derived from a tetrahedral decomposition, enabling intuitive flight control, scalable autonomy, and the use of redundant avionics distributed across modules. Theoretical modeling, simulation, and flight experiments confirm stable hover, repeatable transitions, precise fixed-wing cruise, and hybrid missions with multi-module vehicles. These results establish a scalable foundation for structured modular VTOL design and point to reconfigurable assemblages that retain efficiency, robustness, and ease of deployment