Abstract: The development of offshore wind energy in tropical cyclone-prone regions requires analytical frameworks that capture non-stationary climate dynamics. This study presents a multi-scale spectral approach to characterize Atlantic tropical cyclone variability and assess implications for offshore wind resilience in the Caribbean Basin. The methodology integrates Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) to resolve temporal variability in sea surface temperature, cyclone frequency, and intensity, complemented by two-dimensional kernel density estimation (KDE) and non-stationarity analysis. Using NOAA and National Hurricane Center datasets, results identify dominant periodicities at annual and ENSO (2–7 year) scales, a post-1995 spectral energy shift associated with the positive AMO phase, and a thermodynamically consistent energy corridor along 12-16°N. A statistically significant change point in 1987 (Pettitt test, p < 0.05) is detected, although spatial displacement is not significant. An integrated Wind Risk Index highlights the central-western Caribbean as a high-exposure zone overlapping offshore wind development areas. Exceedance analysis shows that 39.8% of observations surpass 25 m/s, 6.0% exceed 50 m/s, and 1.3% approach 70 m/s, indicating relevant design considerations. These findings support the need for non-stationary, multi-scale approaches in offshore wind risk assessment under tropical cyclone influence.

Abstract: Marine renewable energy systems, including offshore wind, tidal, and wave technologies, are central to global net-zero strategies but remain constrained by reliability-driven costs and uncertainty in structural performance. In harsh offshore environments, interacting degradation mechanisms (such as corrosion–fatigue, hydrogen embrittlement, variable-amplitude loading, wear, and manufacturing-induced variability) govern failure, yet are not adequately captured by existing empirical design frameworks. This review presents a comprehensive, mechanism-based perspective on structural integrity in marine renewable energy systems, explicitly linking microstructure-sensitive deformation and damage processes to engineering-scale performance and reliability. The materials landscape, including structural steels, titanium alloys, fibre-reinforced composites, and additively manufactured materials, is critically examined with emphasis on process–structure–property–performance relationships. Multiscale modelling approaches are synthesised, spanning crystal plasticity finite element modelling, mesoscale damage formulations, fracture mechanics, structural reliability methods, and emerging digital twin and data-driven frameworks. A key contribution of this work is the integration of microstructure-resolved modelling with system-level reliability and qualification, addressing a critical gap between materials physics and engineering design standards. The review identifies critical limitations in current practices, including the lack of explicit treatment of coupled degradation mechanisms, insufficient representation of manufacturing variability, and the absence of consistent uncertainty propagation across scales. Building on these insights, an integrated, mechanism-resolved framework is proposed that combines multiscale modelling, manufacturing-aware qualification, inspection-informed updating, and hybrid physics–data approaches. This framework supports a transition from static, empirical design towards predictive, lifecycle-based structural integrity assessment, enabling improved reliability, reduced uncertainty, and more cost-effective deployment of next-generation marine renewable energy systems.

Abstract: During the exploration drilling process, maintaining a vertical well trajectory is a critical issue. In geological formations with complex conditions that are prone to well deviation, conventional drilling tool assemblies exhibit poor anti-deviation performance. To achieve anti-deviation and accelerate drilling in exploration wells, a pre-bent drilling tool assembly is proposed. In this study, a dynamic model of the pre-bent drilling tool assembly was established. The anti-deviation mechanism of the pre-bent drilling tool assembly was investigated. The deviation-reduction effects of the drilling tool assembly under different parameter conditions were analyzed. The results indicate that the deviation-reducing force initially increases and then decreases as the pre-bend angle of the anti-deviation drilling tool increases. When the bend angle is between 1° and 1.13°, a larger deviation-reducing force is generated at the drill bit. A shorter distance (L1) between the near-bit stabilizer and the drill bit, a smaller near-bit stabilizer diameter, and a larger upper stabilizer diameter result in a greater deviation-reducing force. The relationship between the deviation-reducing force and the distance between the two stabilizers (L2) is not explicitly linear, but a decreasing trend is observed after the distance exceeds 10 m. Compared with the conventional pendulum anti-deviation drilling tool assembly, the deviation-reducing force of the pre-bent drilling tool assembly has an advantage of more than two orders of magnitude. Based on the calculation results, the optimal design of the pre-bent drilling tool assembly was carried out. The bend angle was increased to 1.15°, the diameter of the near-bit stabilizer was reduced to 305 mm, L2 was reduced to 9–11 m, and L1 was reduced to 0.9 m. Field applications in 22 exploration wells show that the pre-bent drilling tool assembly provides excellent anti-deviation effects. It can fully release the weight on bit while ensuring a vertical trajectory, achieving a 14% increase in the drilling rate. This technology effectively replaces vertical steering tools. Tool costs are significantly saved, providing an effective method for anti-deviation in complex formations.

Abstract: This paper reports thermophysical-property data for binary dielectric mixtures of hy-drofluoroether (HFE) fluids and ethyl acetate (EA) and applies a correlation-based workflow to compare their single-phase forced-convection performance in rectangular minichannels. Density, viscosity, thermal conductivity, and isobaric heat capacity were measured at three temperature levels (293.1, 313.1, and 328.1 K) for selected compositions of HFE-7100/EA, HFE-7300/EA, and HFE-73DE/EA. Using these meas-ured properties, Reynolds and Prandtl numbers were evaluated and a laminar ther-mally developing correlation was employed to obtain Nusselt numbers and corre-sponding heat transfer coefficients. The assessment was performed for two geometries representing a long reference minichannel module and a short multi-minichannel module. A validation dataset for pure HFE-7100 in the short module, derived from IR thermography and an energy-balance data reduction, indicates a systematic deviation between correlation-based estimates and experimental values, which should be con-sidered when interpreting absolute predictions. The presented dataset and workflow support transparent down-selection of candidate mixtures prior to extended experi-mental campaigns.

Abstract: The management of European mountain landscapes is increasingly threatened by rural abandonment and escalating environmental risks. This study investigates an innovative Stewardship-Renewable Energy Communities model for the Central Apennines, exploring how post-seismic public reconstruction can serve as a financial engine for territorial maintenance. Utilizing Open Data Sisma administrative records and Photovoltaic Geographical Information System irradiation metrics, the research assesses the solar potential of 20 municipalities within the Sibillini seismic crater. To ensure a reliable baseline, a Building Suitability Coefficient was introduced as a conservative proxy for the public reconstruction sector. Results indicate that the establishment of public Renewable Energy Communities could generate approximately €1.08 million in annual revenue from 325 identified energy nodes. This economic surplus provides a Stewardship Capacity sufficient to fund the active maintenance of 789.77 hectares per year through Nature-based Solutions, assuming a standardized rate of 1,200 €/ha. The study concludes that distributed rooftop solar portfolios represent a non-invasive, self-funding mechanism for mountain resilience. By leveraging the Anthropo-systemic capital of reconstructed public hubs, mountain territories can transition from passive management neglect to active, energy-backed stewardship, offering a reproducible template for high-value cultural landscapes.

Abstract: Hydrogen is emerging as a clean, alternative energy source that can be used in a wide range of applications. Worldwide, the transport sector is heavily dependent on fossil fuels, and to transition this sector to hydrogen technology, it will require extensive deployment of a hydrogen refuelling station network across countries to support hydrogen-powered vehicles. This study examines the consequences of hydrogen leaks from a liquid hy-drogen storage tank and dispenser. A validated DNV PHAST software tool was used to evaluate the hydrogen leak dynamics under varied leak apertures (5mm and 25mm), to determine dispersion patterns, jet-fire thermal radiation intensity, and explosion over-pressure distance relationship under different wind speed intensities. The results indicate that wind speed, system operating pressure, and leak aperture size have a significant impact on the dispersion concentration, jet fire thermal radiation, and explosion over-pressure effect distance; a 25mm leakage elevates the radiation intensity and explosion overpressure, producing a harmful effect distance greater than 5mm leakage cases. Furthermore, a 25mm leak from a dispenser produces an explosion overpressure with greater harm effect distance than a liquid hydrogen leak from a storage tank. This study reveals fundamental hydrogen incident dynamics and provides valuable insights to be considered in the hydrogen refuelling stations to prevent hydrogen releases.

Abstract: Flexible photovoltaic modules offer an innovative approach for Building Integrated Photovoltaics (BIPV) on non-planar envelopes. However, the dynamic outdoor environment aggravates the photoelectric mismatch mechanism caused by complex curved geometries. This study experimentally investigates the outdoor experimental investigation into the dynamic electrical and thermal performance of large-scale curved CIGS modules equipped with bypass diodes. Six representative configurations—flat, length-convex(lgvx), length-concave(lgcv), width-convex(wdvx), width-concave(wdcv), and wavy—were continuously monitored under real weather conditions in Hefei, China. The results indicate that while flat modules maintain the highest daily energy yield (453.32 Wh) , the wdvx in longitudinal direction exhibits exceptional adaptability, achieving an average Performance Ratio (PR) of 91.46% and outperforming the flat type during low solar altitude periods in the day. Infrared thermal imaging reveals significant temperature gradients driven by the mismatch effect, with the lgcv module reaching a peak temperature of 65.88°C. Furthermore, the I-V characteristic curves demonstrate that non-uniform self-shading triggers bypass diode activation, resulting in severe step-like current drops and multiple power peaks in concave and wavy shapes. These findings offer crucial practical guidelines for optimizing cell layout and thermal management in curved BIPV envelops.

Abstract: To address the difficulty of simultaneously achieving effective heat dissipation and adequate humidification in open cathode air cooled proton exchange membrane fuel cells (PEMFCs) under medium and high power operation, this study proposes a hydrothermal management strategy based on coordinated ultrasonic atomization humidification and fan speed regulation. A three dimensional single cell multiphysics model is developed and validated using a 300 W experimental platform. The effects of atomization frequency and water temperature on stack performance and internal hydrothermal distribution are systematically investigated. Results show that ultrasonic atomization provides inlet precooling, latent heat absorption, and active region humidification, thereby improving hydrothermal uniformity within the stack. Under the optimal condition of 100 kHz and 55 °C, the peak stack power increases by 21.0% to 319.00 W, while voltage consistency and surface temperature uniformity are also improved. Analysis based on the Stokes number and Dalton’s law of partial pressures indicates that the optimum results from a balance between suppressing droplet agglomeration and inertial deposition, and limiting oxygen dilution caused by excessive water vapor. The proposed strategy provides a compact and practical approach for improving the stability, uniformity, and efficiency of air cooled PEMFCs.

Abstract: Flexible photovoltaic(PV) technology not only has high power efficiency but also is thin and lightweight, enabling seamless adaption to the surface of curved buildings. However, the distinctive spatial geometry of curved surfaces leads to inhomogeneous irradiance, causing electrical mismatch losses. This paper presents a systematic indoor experimental study on the electrical performance of Copper Indium Gallium Selenide (CIGS) cells under various bending configurations, including length-convex (lgvx), length-concave (lgcv), width-convex (wdvx), and width-concave (wdcv). Tests were conducted under standard testing conditions (1000 W/m², 25°C) with central angles ranging from 0° to 180° and placed in longitudinal and horizontal orientations， respectively. Results indicate that width-bending configurations generally outperform length-bending ones due to lower mismatch losses. For width-bending, concave forms exhibit higher power output than convex forms due to a mutual reflection mechanism. Conversely, length-concave forms manifest the highest power mismatch loss (up to 319.70 mW at 180°) due to significant self-shading. These findings provide critical design guidelines for optimizing cell layouts in curved BIPV systems.

Abstract: This study develops and validates a climate-based, user-centred and data-informed framework to improve lighting performance in educational buildings through the integrated use of daylight and smart LED control systems. The research was conducted in a university facility in Madrid, Spain, using a mixed-methods approach combining on-site illuminance measurements, climate-based lighting simulations (CBMS) with Dialux Evo 12.1, and structured surveys on user perception. The objective was to quantify the dynamic interaction between daylight availability, artificial lighting demand, and perceived visual comfort, while assessing the energy-saving potential of daylight-responsive control strategies. Results show that existing LED systems meet current illuminance standards while maintaining low lighting power density (LPD). Daylight and electric lighting act complementarily, with daylight reducing artificial lighting demand by up to 50% in optimally oriented classrooms, particularly during spring and summer. Smart dimming and adaptive control systems provide additional energy savings ranging from 27% to 46%, with estimated payback periods of approximately four years. Overall, the findings demonstrate that integrating daylight and adaptive LED systems is an effective and scalable strategy for reducing energy use while maintaining visual comfort in educational buildings under Mediterranean climatic conditions.

Abstract: One of the most promising approaches for replacing conventional power plants during the transition to clean energy is the conversion of existing coalfired power plants (CPPs) into nuclear power plants. This strategy offers numerous ecological and economic advantages. However, integrating a nuclear reactor with a steam turbine originally designed for a coal plant is far from trivial and involves significant technical challenges. The purpose of this work is to analyze and evaluate various options for coupling a HighTemperature GasCooled Small Modular Reactor (HTGR SMR) with a potentially suitable subcritical steam turbine from an existing CPP, thereby creating several repowering configurations. The main difficulties stem from the fact that the turbine was designed to operate with live steam at lower flow rates, temperatures, and pressures than those typically provided by an HTGR SMR. In addition, the feedwater temperature and pressure requirements for the HTGR SMR steam generator differ substantially from those in a CPP, leading at best to additional efficiency losses. Moreover, the overall thermal cycle layouts of the two systems are fundamentally different. Despite these challenges, technically feasible combinations can be achieved. However, determining which option is the most economically viable depends on numerous additional factors, including the specific characteristics of the individual CPP and the regulatory framework of the country in which it operates.

Abstract: Hydrogen enrichment of compression ignition (CI) engines has emerged as a promising strategy to simultaneously enhance thermal efficiency and reduce carbon-based emissions. This study numerically investigates how hydrogen enrichment affects engine performance and emissions in methanol-diesel dual-fuel CI engines, a combustion mode gaining increasing attention for replacing fossil diesel with sustainable fuels, particularly in hard-to-abate sectors such as maritime transport. The simulations are based on the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations, incorporating the RNG k–ε turbulence model, the Eddy Dissipation Concept (EDC) for turbulence–chemistry interaction, and the G-equation for turbulent premixed flame propagation. The numerical model is validated against experimental data for in-cylinder pressure and heat release rate at 45% methanol substitution ratio (by energy). The results indicate that increasing the hydrogen enrichment ratio (HER, defined on an energy basis) from 5% to 20% raises the Sauter Mean Diameter (SMD) of the diesel fuel from 20.2 µm to 28.0 µm (+38%), driven by the reduction in gas-phase density and weakened Weber-number-controlled droplet breakup efficiency as hydrogen displaces charge oxygen. Furthermore, hydrogen's elevated adiabatic flame temperature and superior mass diffusivity intensify combustion, raising peak in-cylinder pressure from 75.2 to 79.1 bar (+5.2%), amplifying the peak heat release rate from 129 to 211 J/°CA (+63.6%), and elevating maximum in-cylinder temperature from 1542 to 1735 K (+193 K). These thermodynamic gains translate directly into a 6% improvement in indicated thermal efficiency and a 14% reduction in indicated specific fuel consumption (accounting for hydrogen, methanol, and diesel) at HER 20%. On the emissions front, CO₂ declines by 24% in direct proportion to the carbon-containing fuel mass displaced by hydrogen substitution, while NOₓ surges 3.52-fold through intensified Zeldovich thermal pathways. These findings establish hydrogen–enriched methanol–diesel dual-fuel combustion as a viable pathway toward high-efficiency, low-carbon CI engine operation, provided that targeted NOₓ mitigation strategies, such as exhaust gas recirculation (EGR) or optimized injection timing, are concurrently applied.

Abstract: After several critical reports by the Federal Audit Office on the implementation of the energy transition followed a cost estimation of €13.3 trillion by the Scientific Service of the German Bundestag. Political “lack of alternatives” and needed CO2 reduction led to an uncoordinated activism. The resulting promotion of state-funded NGOs and their lobbying pressure ultimately prevented a clear and stringent program management. The lack of scientific understanding regarding the importance of thermodynamic potential for demand-oriented supply failed to recognize a needed energy storage. Nature’s carbon cycle and the potential generation from CO2 and H2O to hydrocarbons were ignored, however this is the solution. The foreseeable financial collapse of the entire concept lies in the thermodynamically superfluous mandatory energy savings and the infrastructure rebuilding to avoid CO2 emissions. However, the use of renewable gaseous hydrocarbons as energy storage enables the continued use of the existing natural gas infrastructure and only requires recirculation of the raw material CO2 without further investments. The results already available today for the renewable feed-in proof the advantages of a solar-powered carbon cycle economy by the rising high costs of thCost Efficient e extensive regulatory measures for stabilizing the European grid. Finally the carbon cycle economy could save around €10 trillion and operating costs comparable to LNG.

Abstract: Aqueous pyrolysis liquid (APL) is the water‑rich by‑product of pyrolysis with high organic content; however, it is too dilute for economical fuel upgrading, so practical applications remain limited. This study investigates the feasibility of co-digesting hydrolyzed sewage sludge filtrate with APL in high-rate anaerobic reactors to enhance energy recovery and as a treatment step for APL. Two lab-scale reactors were operated for >500 days: one fed with filtrate and APL, and a control fed with filtrate only. Results show that APL can be degraded at loadings up to 0.3 g COD_APL/L/d (≈2.1% w/w) without severe inhibition, achieving 93% CODAPL removal and stable methane production. Compared to previous studies, this work demonstrates substantially higher APL degradation under co-digestion conditions. Higher loadings (≥0.44 g CODAPL/L/d) caused inhibition despite recovery attempts. Microbial analysis revealed a shift from acetoclastic to hydrogenotrophic methanogenesis, dominated by Methanobacterium and Methanosarcina, alongside enrichment of taxa linked to resistance to a toxic environment. Measurements of pollutant concentration in effluent indicated partial degradation of low-molecular-weight polycyclic aromatic hydrocarbons (PAHs) and transformation of some polyfluoroalkyl substances (PFAS), though most pollutants persisted in effluent. These findings highlight the potential of high-rate reactors for APL treatment and underscore the need for strategies such as inoculum acclimation, pretreatment, or additives to achieve industrial-scale loadings. The study provides insights into microbial resilience, pollutant fate, and operational considerations for integrated anaerobic digestion–pyrolysis systems.

Abstract: Regional electricity interconnections are increasingly recognised as enablers of cost-effective power system expansion and deep decarbonisation in emerging economies. In East Africa, Kenya and neighbouring countries — Tanzania, Ethiopia, and Uganda — operate relatively low-carbon electricity systems; however, rapidly growing electricity de-mand and expanding thermal generation are placing upward pressure on grid emissions intensity, particularly in Kenya. This study examines whether planned cross-border in-terconnections can mitigate this trajectory using OSeMOSYS Global, an open-source least-cost capacity expansion model, comparing stand-alone national power systems against an interconnected regional grid over 2022–2050. Results show that interconnec-tion enables access to low-cost renewable electricity and facilitates surplus generation ex-ports, maintaining system-wide carbon intensity within climate-finance eligibility thresh-olds of 100 gCO2/kWh. Outcomes are heterogeneous: Ethiopia and Kenya incur cost in-creases (+USD 481 million and +USD 568 million respectively) attributable to transmis-sion capital expenditure, whereas Tanzania and Uganda achieve net cost savings (−USD 590 million and −USD 891 million) alongside substantial emissions intensity reductions of 141.9 and 280.5 gCO2/kWh respectively. Regional emissions equity is preserved, with modest intensity increases in Ethiopia and Kenya offset by large reductions elsewhere. These findings strengthen the case for climate-financed regional transmission as a scala-ble and equitable mitigation strategy in East Africa.

Abstract: Improving the energy efficiency of existing residential buildings is a key challenge for reducing energy consumption in cold climate regions. A considerable proportion of the housing stock in Kazakhstan consists of Soviet-era multi-apartment buildings characterized by high heat losses and low thermal performance. The aim of this study is to assess heat losses and evaluate the energy-saving potential of a typical multi-apartment residential building located in a cold climate. A comprehensive energy audit was conducted, including an analysis of the thermal performance of building envelopes, calculation of heat losses through walls, windows, roof, and heating system pipelines, thermographic inspection, and air infiltration measurements using blower door testing. The results show that the largest share of heat losses occurs through external walls, windows, and uninsulated heating pipelines. The implementation of thermal modernization measures, such as wall insulation, window replacement, and pipeline insulation, can significantly reduce the building’s heat consumption and improve overall energy performance. The findings of this study demonstrate the high potential for improving the energy efficiency of existing residential buildings and may be useful for developing renovation strategies for similar buildings in cold climate regions.

Abstract: To achieve real-time and accurate detections of residual oil distribution during water or CO₂ flooding, this study utilizes the high-frequency Ground Penetrating Radar (GPR) for monitoring of the flooding process in real time. The U-Net neural networks are trained to invert for the subsurface dielectric constants and conductivity distributions. The study first utilizes the gprMax forward tool to simulate the dynamic response changes of rock electrical parameters during flooding and constructs a high-resolution training dataset of 100,000 samples. Each sample contains the relationships between a subsurface electrical parameter model and its corresponding multi-transmitter, multi-receiver GPR responses. A deep learning inversion network based on the U-Net architecture is trained to extract multi-scale features through an encoder-decoder structure, achieving an end-to-end mapping from GPR echo signals to subsurface electrical parameters. Numerical and physical core experimental results show that the method accurately inverts the electrical parameter distributions of the oil, water, and gas in the sandstone model, successfully capturing the position and morphology changes of the displacement front. The average relative error of dielectric constant inversion is controlled within 5%, with the error mainly concentrated in high-conductivity water regions for conductivity inversion results. Compared to traditional full waveform inversion methods, the proposed approach offers a fast inversion solution and is less affected by the initial model and noise. The results reveal the feasibility and superiority of the neural network based deep learning method in GPR electromagnetic inversion, providing a new method for real-time flooding monitoring and intelligent reservoir development during oil and gas flooding.

Abstract: Medium-to-long-term underground heat recovery systems often exhibit cumulative thermal imbalance that is not adequately described by classical local diffusion equations. This study develops a first-principles framework that links thermal engineering with non-equilibrium statistical physics. We derive a hybrid evolutionary generator that unifies local Gaussian diffusion and non-local fractional Lévy-type transport, enabling representation of cross-cycle memory and long-range correlation. Within the Onsager variational and Martin-Siggia-Rose (MSR) formalisms, cyclic thermal evolution is formulated as a gradient-flow process coupled with a thermodynamic conjugate information field. We further show that gradient phase change materials (PCMs) can modulate generator parameters toward a near scale-invariant regime associated with improved long-term stability. Based on this field structure, a path-integral adjoint optimal-control framework is established for periodic external heat-source operation. The proposed framework provides a physically consistent explanation for long-term thermal fading and a practical theoretical basis for sustainable underground heat recovery.

Abstract: Nationwide electrification and consistent power supply remain a forlorn dream in Nigeria, over a decade after the privatisation of the electricity sector. Most studies attribute it to corruption and weak institutions; however, these are just proximate causes. The real causes are underlying variables influencing the slowed metering penetration and poor revenue collection rates. This study examines all 11 DSICOS using monthly data of key performance indicators to assess each DISCOS’ post-privatisation metering and revenue performance. The study adopts an analytical framework comprising descriptive statistics for foundational analysis of key performance indicators (KPIs), Linear and Panel Fixed Effects (FE) regression, and Extension models to accurately quantify the conditional associations between key variables. The R2 values for the clustered robust standard errors (SEs) ranged from 0.715 to 0.879. The metering ratio is a strong positive and statistically significant determinant of revenue collected and collection rate. However, the metering impact trajectories are heterogeneous, with negative metering-collection efficiencies in Benin, Yola, Kaduna, and Enugu. The following structural archetypes were observed: Leaders (Ikeja, Eko, and Abuja); Mid-performers (Port Harcourt, Ibadan, and Kano); Laggers (Benin, Yola, Jos, Enugu, and Kaduna). Also, increasing the total customer base will not yield a proportional increase in energy billed or revenue growth, given the sector’s current overreliance on estimated billing. The value of this research lies in its sector-wide assessment of the DISCOS financial and metering profiles. It buttresses the argument for DISOC-specific frameworks and the dissolution of a uniform regulatory and operational strategy.

Abstract: The article discusses issues related to the possibility of using 10% hydrogen peroxide in ZS engine fuel to reduce exhaust emissions. The additive proposed by the authors of the article is a 12% hy-drogen peroxide solution. The article presents the results of engine and analytical tests carried out by the authors. The article mainly concerns the emission of toxic substances into the atmosphere in the case of an engine fuelled with standard and modified fuel. Laboratory tests showed that the cetane number increased by two units for the modified fuel. The results of engine tests showed that the fuel additive reduces the concentration of nitrogen oxides and hydrocarbons, whilst the soot content increased slightly.