bluuebunny/crossref_metadata_2025 huggingface dataset:
SCR+ASC Performance During a Period of Late Diesel Injection for DPF Regeneration
Authors: Ovaska Teemu , Spoof-Tuomi Kirsi , Niemi Seppo , Valkjärvi Pauli , Mikulski Maciej , Lehtoranta Kati , Alanen Jenni , Happonen Matti , Maunula Teuvo
Published: December 2024

More efficient removal of nitrogen oxides and particulate matter from off-road diesel engines is needed for the future emission requirements (CARB Tier 5). The dual-SCR system is proposed to enhance low-temperature performance by adding a second SCR catalyst near the engine, in addition to the main SCR catalyst located after the diesel oxidation catalyst (DOC) and particulate filter (DPF). However, the regular regeneration of the DPF must be taken care of by injecting diesel fuel so that the excess hydrocarbon that ends up in the DOC+DPF oxidizes the carbon-containing particles at high temperatures. This study used late diesel injection during the DPF regeneration period of a high-speed, common-rail diesel engine. In addition to the US EPA Tier 4F compatible off-road engine, the experimental setup included the exhaust after treatment system (SCR, DOC, DPF) installed into the insulated exhaust line in laboratory environment. Steady-state experiments were conducted to assess how late diesel injection affects vanadium-SCR and ammonia slip catalyst performance, with the SCR inlet temperatures from 250 to 400 °C. The study’s overall conclusion is that the late diesel injection strategy through a vanadium-ccSCR catalyst is viable for particulate filter regeneration only when SCR inlet temperatures are sufficiently high (≥ 320 °C). At lower temperatures, hydrocarbons from late diesel injection might cause exothermic reactions in the SCR, leading to a notable reduction in its deNOx performance.
Comprehensive Life Cycle Analysis of Diverse Hydrogen Production Routes and Application on a Hydrogen Engine
Authors: Accardo Antonella , Gentilucci Gaia , Spessa Ezio
Published: December 2024

In the effort of achieving net-zero Greenhouse Gas (GHG) emissions, hydrogen is becoming increasingly relevant in several sectors such as automotive, cogeneration, maritime, off-road, and railroad. However, hydrogen can be produced from different routes that involve different production processes and feedstocks. In contrast to the key role of hydrogen in the transport sector’s decarbonization, publications that claim to address the environmental impacts of hydrogen are often focused on Global Warming Potential (GWP) and GHG emissions only. This manuscript focuses on the environmental impacts of hydrogen production considering different production routes (i.e., Steam Methane Reforming (SMR), SMR coupled with Carbon Capture and Storage (CCS), Coal Gasification (CG), CG coupled with CCS, electrolysis from fossil fuels and from wind) and a broad set of environmental impact categories, not only GWP. The Life Cycle Assessment (LCA) methodology is applied in the present study with a twofold aim. The first aim is to develop the LCA models of diverse hydrogen production routes and address present and potential well-to-tank environmental impacts. The second aim is to apply the previous findings to develop a cradle-to-grave LCA of a hydrogen engine, serving as a case study for the automotive sector. The LCA models are developed using SimaPro v.9.4.0.3 as LCA software and Ecoinvent v3.8 as background database. The functional units are 1 kg of hydrogen for the cradle-to-gate boundary and 1 mile of vehicle lifetime for the cradle-to-grave boundary. The life cycle impact assessment method is the TRACI 2.1 method developed by the US Environmental Protection Agency.
Investigation of Fuel Passage Geometry on Performance of Cooled Spray Inserts for Particulate Reduction in a Heavy-Duty Engine
Authors: Klingbeil Adam , Tinar Tristen
Published: December 2024

Cooled spray technology has the potential to reduce particulate emissions in heavy-duty diesel engines by more than 50% while minimally impacting other emissions and performance parameters. However, the ideal design of these components is not known and there are a variety of parameters that could be varied to optimize performance including fuel passage diameter and length, fuel passage inlet and outlet geometry, surface finish and manufacturing materials.

In this study, we evaluate the effect of Cooled Spray geometry on engine performance. A focused study on fuel passage inlet shaping reveals a strong sensitivity, suggesting that chamfering the fuel passage inlet is critical for improved engine performance. In addition, the fuel passage diameter is varied between 2.2 and 2.8 mm to characterize the sensitivity of engine performance to the fuel passage diameter. At low load, the Cooled Spray inserts consistently show improving performance with smaller fuel passage diameter coupled together with chamfered fuel passage inlets for both EGR and non-EGR operation. At high load operation, the performance of the Cooled Spray inserts is notably worse with less consistent trends to fuel passage diameter and fuel passage inlet shaping. Furthermore, the performance trends at high load are different for EGR and non-EGR operation. This work shows that there is significant performance potential for this technology, but the relationship between geometry and ambient conditions needs to be understood and exploited for best overall performance.
An Experimental Comparison of Methanol Combustion Strategies: Spark Ignition Versus Compression Ignition
Authors: Gandolfo John , Lawler Benjamin , Gainey Brian
Published: December 2024

Methanol has garnered significant attention over the past few years due to its potential as a hydrogen carrier in a future green economy. As a result, it is a leading candidate to displace fossil fuels in the transportation sector. Although recent research efforts have been directed towards adopting the fuel in compression ignition engines, methanol is an ideal fuel for light-duty high compression ratio spark ignition engines due to its fast laminar flame speed, high auto-ignition resistance, and high cooling potential. In this work, methanol was combusted in a single-cylinder spark ignition engine with a compression ratio of 14.8 and compared to E10 (regular grade gasoline - 10% ethanol, 90% ethanol by volume), E75 (75% ethanol, 25% gasoline by volume), and hydrous ethanol (92% ethanol, 8% water by mass) at 6 bar IMEPn. Methanol achieved a net fuel conversion efficiency of 42.5% compared to 41.6% with hydrous ethanol, 39.5% with E75, and 36.2% with E10.

Next, the performance of the high compression ratio spark ignition engine was then compared to a methanol-fueled light-duty single-cylinder compression ignition engine. At loads of 6 bar and 10 bar IMEPn, the net fuel conversion efficiency of stoichiometric spark ignition was higher than lean mixing-controlled compression ignition by 2.6 and 3.3 percentage points, respectively. The net fuel conversion efficiency of mixing-controlled compression ignition was higher than spark ignition by 0.2 percentage points at a load of 16 bar IMEPn. The competitiveness of spark ignition with mixing-controlled compression ignition was due to the high thermodynamic penalty associated with injecting a high heat of vaporization fuel like methanol close to top dead center where heat from the working fluid is absorbed to evaporate the fuel rather than being converted to thermodynamic work. To remedy this, an advanced compression ignition strategy using premixed and partially premixed injections was demonstrated to provide the highest net fuel conversion efficiency across the tested combustion strategies by avoiding this thermodynamic penalty and taking full advantage of the lean and unthrottled nature of compression ignition.
Effect of Intrinsic Instabilities on Engine Performance for Hydrogen-Methane Blends
Authors: Nawaz Behlol , Cowart Jim , Das Shubhra Kanti , Nasim Md Nayer , Mack J. Hunter
Published: December 2024

Intrinsic instabilities cause wrinkling in laminar flames due to the mixture’s innate properties, regardless of chamber construction. While their effects are generally overshadowed in turbulent flames such as those observed in internal combustion engines, this is not the case for hydrogen (H2) flames. Blends of H2 and methane (CH4) have great potential to be used as low-carbon fuels, though they face several challenges associated with combustion behavior, material compatibility, and distribution infrastructure. Multiple equivalence ratios (Φ = 0.7, 0.77, and 1.0) and blends (0, 20, 30, and 50% H2 fuel fractions) were first studied in an optically accessible constant volume combustion chamber (CVCC) to determine the propensity for wrinkling among different equivalence ratio and blend combinations. These equivalence ratio and blend combinations were then tested in a spark ignition (SI) engine to investigate the performance of different intrinsic instability regimes of H2-CH4 blends. The results show that an increase in H2 fraction in the fuel increases the heat release and the peak in-cylinder pressure while reducing the burn duration. However, there was no indication that any of these metrics were affected by the flame wrinkling for the blends considered in this study.
Operation and Performance of a Monofueled Compression Ignition, Direct Injection, Natural Gas Heavy Duty Engine
Authors: White Tyler , Bonfochi Vinhaes Vinicius , Eggart Brian , Singh Ashish , Turcios Marco , Munshi Sandeep , Naber Jeffrey
Published: December 2024

The Compression Ignition of Directly Injected Natural Gas (CIDI NG) offers a potential 25% reduction in CO2 emissions due to its high hydrogen-to-carbon ratio compared to diesel, while achieving ultra-low PM formation with high efficiencies and load capability. The primary challenge of a CIDI NG engine is achieving suitable ignition temperatures, upwards of 1150K, and in-cylinder conditions required for the stable ignition and combustion of late cycle high pressure direct injection of the fuel over a wide operating range. This experimental study investigates CIDI NG combustion in a heavy-duty Single Cylinder Research Engine (SCRE). The SCRE uses a combination of ignition-enhancing technologies targeting the required conditions, including an increased compression ratio, intake charge heating, thermal barrier coatings, EGR, and NG pilot injection. Additionally, charge mixing is promoted through the refinement of the piston bowl geometry, resulting in improved efficiency and reduced soot formation. This study shows the effect of the implemented hardware technology (CR, Bowl Geometry, Thermal Barrier Coating) on the combustion at key operating conditions (low, medium, high load, high-efficiency operation, low emissions) of the NG CIDI engine. Stable combustion and engine operation were demonstrated over a wide load from 5.5 bar to a peak load of 25 bar IMEPg, and a maximum indicated thermal efficiency (ITE) of 48.8% at a load of 15.2 bar IMEPg was achieved. The work conducted with the single cylinder research engine shows that this operation is feasible and can become commercially available in the future.
Mixing and Warming Characterisation of Cryogenic Hydrogen Jets Through Proper Orthogonal Decomposition
Authors: Tretola Giovanni , Shen Li , Leach Felix , Vogiatzaki Konstantina
Published: December 2024

Hydrogen is being increasingly used as an alternative fuel for vehicles and aircraft propulsion. For long-distance transportation and large-scale energy storage, liquid hydrogen or cryo-compressed hydrogen with typical densities of 70 g/L, is more promising than warm compressed gaseous hydrogen. The use of cryogenic compressed hydrogen introduces new challenges for existing safety standards. In the event of potential leaks, the resulting jets are characterised by intense heat and mass transfer. Furthermore, given the storage pressure and leak diameters, these jets can acquire extremely high velocities, which, in combination with the ultra-low temperature prevailing, introduce considerable challenges to characterize the physics of complex cryogenic hydrogen jets. In this study, using a novel CFD framework specifically tailored to ultra cold dynamics, we analyse the warming and diffusion of a hydrogen cryogenic gas jet into atmospheric air. The simulated conditions are based on an experimental vertical jet. Stagnation conditions are characteristic of unintended leaks from pipe systems that connect cryogenic hydrogen storage tanks and could be encountered at a fuel cell refuelling station. Jets with pressure up to 5 bar and temperatures just above the saturation liquid temperature were examined. Comparisons are made to the centreline mass fraction and temperature decay rates. Satisfactory agreement with the measurements was found in terms of centreline mass fraction and temperature. To characterise the mixing and warming mechanisms of such cold jets, a principle component analysis (PCA) method, namely the proper orthogonal decomposition (POD) technique, is also performed on the simulated data sampled at a fixed domain but at different instants in time. The combined role of the mass and heat flux on heating the cold hydrogen jet is observed. The POD shows the role of turbulent fluctuations in warming the core of the jet. The heat flux observed in the outer plume instead is not captured by the low-order temporal fluctuations, which means that thermal diffusion is responsible for the warming in this region.
Investigation of Performance and Emissions of Premixed Combustion of Hydroprocessed Esters and Fatty Acids (HEFA) in a CRDI Research Engine With Methanol PFI
Authors: Soloiu Valentin , Willis James , Dillon Nicholas , Norton Coleman , Davis Zachary , Graham Tristan
Published: December 2024

An investigation of the performance and emissions of premixed combustion of a synthetic paraffinic kerosene sustainable aviation fuel (SAF) consisting of hydroprocessed esters and fatty acids (HEFA) was conducted using a CRDI research engine with ultra-low sulfur diesel (ULSD) as a reference. In a constant volume combustion chamber (CVCC), HEFA exhibited a shorter ignition delay, confirmed by its higher derived cetane number (DCN) at 58.6 compared to ULSD at 48. Further investigation was carried out at 5 bar indicated mean effective pressure (IMEP) with the addition of EGR to control combustion and mitigate NOx. Methanol, a low reactivity fuel, was port fuel injected (PFI) at 50% with HEFA (by mass) and ULSD to investigate its cooling effect on in-cylinder temperatures as a means of mitigating NOx.

Combustion pressure for HEFA was found to be greater than ULSD in most cases and occurred sooner. The apparent heat release rate (AHRR) was notably lower for HEFA than for ULSD in most cases, while the addition of methanol resulted in an increased duration of the low temperature heat release region for both HEFA and ULSD. With addition of EGR and PFI, several negative temperature coefficient regions were observed correlating with the pilot, primary, and tertiary direct injections.

HEFA saw more than a 10% reduction in NOx than ULSD in CDC. The addition of EGR resulted in further reduction of NOx compared to ULSD at equal operating points. Implementing EGR and 50% methanol PFI with HEFA reduced NOx emissions by over 70% compared to ULSD in CDC. In all studied cases, CO2 emissions for HEFA were slightly reduced compared to ULSD at matched operating parameters, while CO increased compared to ULSD. Lastly, both ULSD and HEFA achieved a combustion efficiency of 97% in CDC at 5bar IMEP. The combustion behavior of the studied HEFA in combination with the emissions reduction suggests potential suitability as a substitute for ULSD in some applications.
Investigation of the Performance and Properties Characterization of Hydro-Processed Esters & Fatty Acids (HEFA), FT Synthetic Paraffinic Kerosene (S8), F-24, and Jet-A
Authors: Soloiu Valentin , Norton Coleman G. , Davis Zachary W. , Graham Tristan , Strickland Mitchell , Rahman Mosfequr
Published: December 2024

In this study, Hydro-processed Esters & Fatty Acids (HEFA), FT synthetic paraffinic kerosene (S8), with F-24, & Jet-A as reference, were analyzed for their performance and fuel characteristics.

The spray characteristics of each fuel were evaluated utilizing a Malvern Spraytec He-Ne Laser. The Sauter Mean Diameter (SMD) was determined to be 14.24 μm, 17.22 μm, 18.40 μm, and 19.19 μm for HEFA, Jet-A, F-24, and S8 respectively. HEFA also displayed a spray droplet distribution (SDD) with a Relative Span Factor (RSF) of 2.17. Jet-A indicated an RSF of 2.49. S8 and F-24 displayed RSF values of 3.26 and 3.25.

The autoignition characteristics and combustion regions of the neat research fuels were analyzed in a CVCC to determine the effect of Derived Cetane Number (DCN) on Ignition Delay (ID), and Low Temperature Heat Release (LTHR). HEFA was found to have a DCN of 58.58, which was comparable to S8’s DCN of 59.96. The DCN of HEFA displayed an 18.4% increase from conventional Jet-A which has a DCN of 49.47. In addition, HEFA demonstrated shorter ignition delay and combustion delay at 2.70 ms and 4.10 ms, which were 15.09% and 14.58% shorter than Jet-A. HEFA exhibited a similar behavior to S8 generating a LTHR region that lasted a duration of 1.08 ms, or 28.94% shorter than Jet-A. The shorter LTHR duration led to less overall net heat release during LTHR for HEFA compared to Jet-A.

The tribological properties of each fuel were tested for their friction and wear on a T-11 Pin on disk tribometer under ASTM standard G99-17. HEFA displayed favorable results in comparison to F-24, S8, and Jet-A due to its superior tribological properties. This is seen with HEFA having a friction force of 0.0903N and a wear rate of 0.678 mm3N∗m * 10−4. Jet-A showed similar signs of friction and wear with results of 0.0926N and 0.82752 mm3N∗m * 10−4. F-24 and S8 were the worst out of the four fuels tested showing a friction force and wear rate of 0.0916N and 0.0945N and a wear rate of 1.19 mm3N∗m * 10−4 and 0.0932 mm3N∗m * 10−4 respectively.
Experimental Investigation of the Effect of Air-Handling and DME-Propane Blends on the Performance and Emissions of a 4-Cylinder CI Engine
Authors: Hassan Hafiz Ahmad , Ankobea-Ansah King , De Ojeda William , Wu Simon Haibao , Hall Carrie
Published: December 2024

Dimethyl ether (DME) is considered an excellent alternative to diesel because of its higher cetane number and lower carbon content. Additionally, DME can be blended with abundantly available propane with minimal modifications to the propane infrastructure. This paper focuses on an experimental investigation of the effect of air-handling i.e., boost pressure and exhaust gas recirculation (EGR), and DME-propane blends on the combustion and emissions performance of a light-duty, four-cylinder, compression ignition (CI) engine. The boost pressure and EGR sweeps were carried out and showed that higher boost pressures resulted in increased brake thermal efficiencies (BTE) at the expense of higher NOx emissions which could be reduced by an increase in EGR. The fuel sweeps were carried out at 0, 15 and 25% propane (neat, 85% and 75% DME) with 0% and 25% EGR. The fuel sweeps indicated that the ignition delay (ID) increased and burn duration (BD) decreased monotonically when the blend increased to 25% propane/75% DME. The results suggest optimum engine performance with neat DME at 105 kPa boost pressure and 25% EGR with propane addition improving the BTE with negligible increase in emissions. Higher contents of Propane, up to 25%, did not affect the variability of combustion, with standard deviations of burn duration and peak cylinder pressures below 1% for all test cases.
Computational Model Validation of a Non-Firing Compression Ignition Engine and Chemical Kinetic Mechanism Selection for Diesel-Pilot Assisted Methane Combustion
Authors: Shaalan Amr , Sirna Amanda , Loprete Jason , Mathai Joel Reji , Trelles Juan Pablo , Mack J. Hunter , Van Dam Noah , Lopez-Pintor Dario , Assanis Dimitris
Published: December 2024

In this study, a computational fluid dynamics (CFD) model of a single-cylinder compression ignition engine is developed and validated under motoring conditions. The engine used is the Ricardo Hydra engine at the Advanced Combustion and Energy Systems laboratory at Stony Brook University, which is highly instrumented to collect all data necessary for experimental validation of high-fidelity 3-D model simulation. The model is validated against experimental data for various intake pressures and temperatures. The results show that the model can predict the in-cylinder pressure trace with a peak-pressure accuracy ranging from 0.8% to 1.9% while the trapped mass accuracy ranges from 0.9% to 2.3% depending on the operating conditions. A skeletal chemical kinetic mechanism for diesel fuel is also presented. The mechanism is validated against experimental data for ignition delay, NOx formation, and PAH formation. The results show that the mechanism can accurately predict the combustion behavior of diesel fuel. The validated CFD model and chemical kinetic mechanism will be used in future studies to investigate the potential of diesel-piloted methane as a low-carbon fuel.
Demonstration of Scaled Flowrate Testbed for Emission Aftertreatment Device Testing Under Representative Engine Exhaust Conditions
Authors: Loprete Jason , Kamal Nabil , Sirna Amanda , Mon Tala , Kyriakidou Eleni , Assanis Dimitris
Published: December 2024

The continued development of aftertreatment devices has been critical in reducing engine tailpipe emissions and meeting ever-evolving regulatory standards. Initial phases of catalytic aftertreatment device evaluation often occur at physically scaled-down conditions, typically using laboratory benchtop reactors to test synthesized catalysts that are coated on mini-cores with flow rates of less than 10 SLPM evaluated and often in the range of 0.1–1 SLPM. These flows are often generated artificially using bottled gases and heaters, which do not reflect the conditions that occur under real engine operation. This reduced-scale approach is driven by cost and time constraints, as full-scale device testing requires more catalyst material and production time. Real multicylinder engines produce exhaust flows several orders of magnitude greater than what occurs on the benchtop, with numbers ranging from 1000 to > 10,000 SLPM in typical on-road automotive applications. An intermediary scale approach that can bridge this flowrate chasm is necessary for the efficient rapid prototyping of novel catalytic reactions for aftertreatment applications. This manuscript focuses on validating a variably scaled testbed for catalyst testing that aims to eliminate barriers between cost-effective small-scale testing and realistic full-scale implementations. This study builds on a previous work incorporating a slip-stream approach driven by a venturi-ejector to route flow through a secondary branch containing the catalyst. The current investigation specifically focuses on improving the system’s overall flexibility in terms of accommodating new aftertreatment devices and operating conditions, as well as reducing required auxiliary instrumentation. Differences between the previous iteration of the system are detailed and discussed, as well as recommendations for further improvements to the system. Engine operating parameters such as intake pressure, equivalence ratio, spark timing, compression ratio, and ejector motive pressure are utilized to create the required catalyst inlet temperature, flows, and species concentration for evaluation. The system is tested using a blank catalyst for verifying composition across sampling locations, as well as to generate an operational emissions space for determining the system’s ability to be utilized for intermediate-scale catalyst testing. Initial results show the system’s repeatability and lack of species conversion with an inert monolith to be sufficient for eventually deploying a production catalyst and determining conversion efficiency.
Influence of Engine Operating Parameters and Different Fuels on the Soot Reactivity of Diesel Engines
Authors: Böhmeke Christian , Wagner Uwe , Koch Thomas
Published: December 2024

Strong efforts to reduce CO2 emissions, including in commercial vehicle diesel engines, require the optimization of all processes and engine components that influence fuel consumption. Subsequently, also the additional fuel consumption for particulate regeneration is increasingly focused on. Increasing soot loading of the DPF increases the exhaust back pressure and is therefore deteriorating thermal engine efficiency. Additionally, DPFs are only providing specific maximum soot loading capacities and have to be regenerated accordingly by oxidizing the accumulated soot. The energy or temperature, respectively, which is required for oxidizing the soot to CO2 strongly depends on the physicochemical properties of the soot and is commonly described as particulate reactivity. More reactive soot is advantageous for fuel-efficient regeneration as it can be oxidized at lower temperatures.

This work deals with the influence of various engine operating parameters (speed, load, air-fuel ratio, EGR, injection) as well as the influence of fuels on particulate emissions. The associated soot reactivity is compared between conventional fossil diesel (with and without fatty acid methyl ester), regeneratively produced paraffinic diesel fuel HVO (Hydrotreated vegetable oil) and a blend of HVO and oxymethylene ether (OME). All investigations were performed on a single-cylinder research engine. The engine out particle measurements were carried out using a particle size spectrometer and a photoacoustic sensor. Gaseous emissions were recorded using an exhaust gas measuring system and an infrared spectrometer. Additionally, collected engine out soot samples a thermogravimetric analysis (TGA) was implemented to determine the reactivity of the soot.

Regardless of the engine operating point set, it was found that the particulate mass for the HVO fuel is significantly lower than the particulate mass of the fossil diesel fuels. In contrast, however, the HVO fuel has an increased number of particles due to smaller particles. A significantly lower particle mass and particle number concentration was achieved with the HVO/OME blend. The NOx emissions were at a similar level regardless of the fuel used. A variation of engine operating parameters showed the same tendencies in terms of soot reactivity, regardless of the fuel used. However, the parameter variations were more or less pronounced depending on the respective fuel. It is particularly noteworthy that, aside from operation at low EGR rates and high air-fuel-ratios, where higher reactivities were observed when using diesel B0, no significant differences in reactivity were evident among the fuels used.
Effects of Inlet Port Geometry on MCC Mixing Sensitivity Study
Authors: Beurlot Kyle , Jacobs Timothy
Published: December 2024

Pre-combustion chambers are a common pathway to improve ignition stability and combustion quality while simultaneously offering significant emissions reduction potential in large-bore natural gas two-stroke engines. Prechambers serve to help reduce the carbon footprint of these pipeline engines by extending the lean ignition limits of operation, reducing fuel consumption and overall greenhouse gas emissions. By extension, the significant reduction potential of overall emissions from legacy engines serves to reduce the carbon footprint of pipeline compressor stations across the nation. Based on the foundations of previous research with encouraging results in prechambered engines, this study utilized a numerical simulation approach to evaluate new concepts for improving mixture homogeneity during the scavenging and gas exchange process in an industry relevant large bore natural gas two stroke engine. The simulation was created using Converge CFD software and was validated using experimental data. A wide variety of concepts were tested, and various parameters, including overall air flow, mixture quality, and flow field interaction are evaluated for their influences on the combustion process, including residual methane and NO production mechanisms. The paper reviews and analyzes the sensitivity of the prechamber and main chamber interactions to these parameters, providing fundamental insight into the combustion process and emissions formation.
Combustion Characteristics of Hydrogen, Propane and Methane Gases in a Boosted Featureless Port-Injection SI Engine
Authors: Fakeye Adebayo , Yang Junfeng
Published: December 2024

The search for alternative transport fuel with comparable performance to fossil fuels in powering internal combustion engines (ICEs) has been a topical research project for decades. This is important because ICE is a well-developed technology, but fossil fuels are a finite resource, yet their consumption causes environmental damage. The alternative fuel is therefore expected to overcome these limitations. Hydrogen gas has been on top of the list as the most suitable option, but it is widely proposed dilute it with other fuels for better performance. To understand the effects of diluents such as methane and propane on the combustion characteristics hydrogen gas, Particle Image Velocimetry (PIV) was employed in this study to compare the fundamental combustion characteristics of hydrogen, propane and methane as single fuels at similar conditions in a featureless Leeds University Ported Optical Engine, (LUPOE-2D). The experiments were carried out at low speed of 50 rpm and a boosted inlet pressure of 1.67 bar at port inlet closing, typical of a downsized engine. The mixtures were ignited during the compression stroke at 5 bar. The inlet air was heated, and the temperature of the cylinder head was slightly adjusted from room temperature of 25 ± 2°C for the different mixtures such that a temperature of 439K was obtained for the mixtures at spark pressure of 5 bar. The temperature was estimated using the first law of thermodynamics. Flame combustion characteristics such as flame wrinkling parameters, stretch rate, burning velocities, etc., were derived and compared. There is good agreement between the stretched laminar burning velocities derived from direct measurement of the flame speed and unburned gas velocities ahead of the flame front, extrapolated to the zero-stretch, the values derived from the products of the unstretched flame speeds and the density ratios, and Chemkin-computed values. The burning rates increased with increase in flame stretch except for H2 ϕ = 0.5 which increased to a peak before declining in similar manner as the flame stretch reached a peak and declined before the influence of wall confinement. The flame sphericity and the flame wrinkling amplitude were used to compare their flame wrinkling characteristics of the flames. H2 ϕ = 0.5 flames showed significant instability from the onset and became more winkled as the flame radius increased.
Layer thickness dependent interface strengthening of nanolayered W/NbMoTaW medium-entropy alloys
Authors: Zhang Y. W. , Ma Y. J. , Wang L. , Cheng J. , Zhang Z. Y. , Shen X. C. , Hua X. , Li G. J. , Cao Z. H.
Published: December 2024

In this work, the interface strengthening behavior of nanostructural W/NbMoTaW medium-entropy multilayer films with different W layer thicknesses was studied by a nanoindentation test. Results indicated that the hardness of multilayer films presented a significant size-dependent effect with the decrease of W layer thickness. The multilayer film reached a peak hardness of 19.8 GPa on account of interface strengthening at the critical layer thickness of 10 nm. An amorphous NbMoTaW layer leads to a decrease in hardness of multilayer films when W layer thickness was less than 10 nm. The room temperature toughness of the multilayer films predicted by the hardness/modulus ratio was improved with the decrease of W layer thickness. The size-dependent interface strengthening due to the decreasing W layer thickness and the solid solution strengthening due to the severe lattice distortion of the NbMoTaW layer are the main strengthening mechanisms of the multilayers.
Linear prediction on Cent scale for fundamental frequency analysis
Authors: Gowriprasad R. , Anand T. , Aravind Rangarajan , Murthy Hema A.
Published: December 2024

Understanding the fundamental frequency and harmonic content of audio signals is crucial for many applications in music analysis, including music transcription, audio synthesis, and genre identification. This study formulates a signal processing approach combining Linear Prediction (LP) analysis and the Cent scale to accurately characterize the pitch and harmonic structure of the audio signals. Pitch tracking on the LP spectrum in the Cent scale provides more accurate and reliable pitch estimation, especially in the presence of noise or overlapping harmonics. The Cent scale aligns the harmonics of different notes more closely, making it easier to discern the correct pitch.
May Measurement Month 2022: results from the global blood pressure screening campaign
Authors: Beaney Thomas , Kerr Gabriele Keziah , Kiru Gaia , McArdle Harsha , Schlaich Markus , Schutte Aletta E , Stergiou George S , Wang Ji-guang , Marin Marcos J , Henandez-Hernandez Rafael , Diaz Alejandro Bimbo F , Alcocer Luis , Lopez-Jaramillo Patricio , Poulter Neil
Published: December 2024

Introduction

Elevated blood pressure (BP) is the major contributor to mortality and disease burden worldwide. May Measurement Month (MMM) is a global BP screening campaign, which aims to raise awareness of BP measurement and provide evidence to inform and influence related health policy.

Methods

This cross-sectional survey included individuals aged≥18 years recruited through opportunistic sampling at sites in 60 countries during MMM 2022. Each participant had three sitting BP measurements and a questionnaire was completed including demographics, comorbidities and lifestyle factors. Hypertension was defined as a systolic BP≥140 mm Hg and/or a diastolic BP≥90 mm Hg (average of the second and third readings) or taking antihypertensive medication. Multiple imputation was used to estimate BP readings where any participant’s BP readings were missing. Linear mixed effects models were used to identify associations between participant characteristics and systolic or diastolic BP.

Results

Of the 715 518 participants surveyed (excluding 50 200 self-measured home BP screenees recruited via the ZOE Health Study app), 257 421 (36.0%) were identified as hypertensive, of whom 57.6% were aware and 49.3% were on antihypertensive medication. Of all participants with hypertension, 26.1% were controlled to <140/90 mm Hg and 12.0% to <130/80 mm Hg. Of those taking antihypertensive medication, 52.7% were taking only one drug class, 52.9% were controlled to <140/90 mm Hg and 24.4% to 130/80 mm Hg. In total, 190 314 (26.6% of total surveyed, 73.9% of hypertensives) participants screened were found to have untreated or inadequately treated hypertension. Only 27.6% of treated hypertensive participants were taking a statin. Substantial coexistence of diabetes, overweight and hypertension was apparent among participants.

Conclusions

MMM confirms a high global burden of hypertension with low rates of awareness, treatment and control. In the absence of systematic BP screening in many countries, the results from MMM underscore the continued need for BP screening to detect and thereby control raised BP.
Can oral cancer screening reduce late-stage diagnosis, treatment delay and mortality? A population-based study in Taiwan
Authors: Tsai Ethan , Walker Brigham , Wu Shiao-Chi
Published: December 2024

Objective

This study evaluates the effectiveness of Taiwan’s nationwide oral cancer screening programme in reducing late-stage diagnosis, treatment delays and mortality.

Design

A retrospective cohort study was conducted.

Setting

The study utilized Nationally representative datasets, including the Cancer Registry, Oral Mucosal Screening and National Health Insurance databases in Taiwan.

Participants

The study included patients with oral cancer diagnosed between 1 January 2010 and 31 December 2013, with follow-up through 31 December 2018. The final analysis included 16 430 patients.

Intervention

The intervention was Taiwan’s nationwide oral cancer screening programme which provides visual inspection and palpation of the oral mucosa.

Primary outcome measures

The primary outcomes measured were late-stage diagnosis (stages III and IV), treatment delay (time from diagnosis to treatment >30 days) and all-cause mortality.

Results

Oral cancer screening was statistically significantly associated with a reduced likelihood of late-stage diagnosis (adjusted OR (AOR)=0.85, 95% CI 0.80 to 0.91, p<0.01). However, screening was also associated with a higher likelihood of treatment delay (AOR=1.09, 95% CI 1.00 to 1.19, p=0.049). Taken together, the screening programme is associated with a slightly lower hazard of death (adjusted HR=0.94, 95% CI 0.89 to 0.99, p=0.01).

Conclusion

While Taiwan’s nationwide oral cancer screening programme effectively reduced late-stage diagnoses and mortality, barriers to timely treatment access remain. Ensuring prompt diagnosis and treatment following screening may further enhance the survival benefits of the programme.
State-of-the-art performance of deep learning methods for pre-operative radiologic staging of colorectal cancer lymph node metastasis: a scoping review
Authors: Keel Benjamin , Quyn Aaron , Jayne David , Relton Samuel David
Published: December 2024

Objectives

To assess the current state-of-the-art in deep learning methods applied to pre-operative radiologic staging of colorectal cancer lymph node metastasis. Specifically, by evaluating the data, methodology and validation of existing work, as well as the current use of explainable AI in this fast-moving domain.

Design

Scoping review.

Data sources

Academic databases MEDLINE, Embase, Scopus, IEEE Xplore, Web of Science and Google Scholar were searched with a date range of 1 January 2018 to 1 February 2024.

Eligibility criteria

Includes any English language research articles or conference papers published since 2018 which have applied deep learning methods for feature extraction and classification of colorectal cancer lymph nodes on pre-operative radiologic imaging.

Data extraction and synthesis

Key results and characteristics for each included study were extracted using a shared template. A narrative synthesis was then conducted to qualitatively integrate and interpret these findings.

Results

This scoping review covers 13 studies which met the inclusion criteria. The deep learning methods had an area under the curve score of 0.856 (0.796 to 0.916) for patient-level lymph node diagnosis and 0.904 (0.841 to 0.967) for individual lymph node assessment, given with a 95% confidence interval. Most studies have fundamental limitations including unrepresentative data, inadequate methodology, poor model validation and limited explainability techniques.

Conclusions

Deep learning methods have demonstrated the potential for accurately diagnosing colorectal cancer lymph nodes using pre-operative radiologic imaging. However, several methodological and validation flaws such as selection bias and lack of external validation make it difficult to trust the results. This review has uncovered a research gap for robust, representative and explainable deep learning methods that are end-to-end from automatic lymph node detection to the diagnosis of lymph node metastasis.
Compensatory function change by segment-counting method in predicted postoperative pulmonary function at 1 year after surgery: systematic review and meta-analysis
Authors: Wang Teng-Wei , Zhang Qiang , Cai Zhihong , Xu Qinhong , Lin Jinrong , Yeh Huilong
Published: December 2024

Background

This systematic review aimed to assess the accuracy of the segment-counting method in predicting long-term pulmonary function recovery and investigate compensatory changes following different extents of lung resection.

Methods

We included studies that measured forced expiratory volume at 1 s (FEV1) between 6 and 18 months postoperatively, comparing it to the predicted postoperative FEV1 (ppoFEV1) using the segment-counting method. The extent of lung resection was correlated with the ratio of postoperative FEV1 to ppoFEV1. A comprehensive search was conducted in Embase, MEDLINE and Web of Science using terms related to ‘lung resection’ and ‘pulmonary function’. The final search was completed on 18 February 2022. Risk of bias was assessed using the Newcastle-Ottawa Scale.

Results

39 studies comprising 78 observation cohorts met the inclusion criteria. The analysis showed significant differences in pulmonary function in patients with ≥3 resected segments. Meta-regression indicated that the number of resected segments significantly impacted the postoperative FEV1/ppoFEV1 ratio, explaining 57% of the variance (R²=0. 57), with moderate heterogeneity (I²=61. 87%) across studies. Other variables, including patient age, body mass index, video-assisted thoracoscopic surgery use and tumour stage, did not show significant effects.

Discussion

Limitations of the review included moderate heterogeneity between studies and potential selection bias related to the stage of cancer and lung volume reduction effects. The findings suggest that the extent of lung resection correlates with better-than-expected pulmonary function, potentially due to compensatory mechanisms.

PROSPERO registration number

This review was registered on PROSPERO (CRD42021293608).
Comparative retrospective study of injuries during military parachuting training and airborne operations from 2013 to 2020
Authors: Rebours Yannick , Aigle L , Agard G , Godron J , Michoud G
Published: December 2024

Introduction

French paratroopers have been deployed during airborne operations for nearly a century. Parachute operations have increased since the start ofOperations ServalandBarkhanein the Sahelo-Saharan strip. These military operations allow paratroopers to be dropped behind enemy lines. Our primary objective was to compare injuries sustained during airborne operations and training. Our secondary objective was to compare serious injuries sustained during airborne operations and training.

Methods

We conducted a multicentric comparative retrospective study of military parachuting injuries sustained during training and airborne operations from 1 January 2013 to 31 December 2020. Parachuting injuries included in our study came from the French Army Injury Register.

Results

During the study period, 91 injuries (among 90 wounded), including one death, were recorded during airborne operations and 2744 injuries (among 2516 wounded), including one death, were recorded during training. Proportionally, injuries were more common during airborne operations (3.3%) than training (0.3%), especially during military freefall operations. Operational static-line jumps are more associated with serious injuries than training ones (OR 3.17, 95% CI 1.79 to 5.62). Compared with training, operational jumps caused proportionally more knee injuries (OR 2.73, 95% CI 1.65 to 4.51, p=0.008) but fewer upper limb injuries (OR 0.36, 95% CI 0.17 to 0.74). A physician and/or nurse medically supported 83.3% of airborne operations. Data collection initially differed between paratrooper units until the French Army introduced a harmonised collection tool (Register of Parachuting Incidents (Fiche de Recueil Accident en Parachute)).

Conclusion

Our study highlights a significantly increased injury rate during airborne operations, especially serious ones, likely due to the cumulative effect of well-known parachuting risk factors (eg, unknown or high wind speed, unknown landing ground type, combat load and night drop), justifying surveillance by qualified parachuting health staff.
Lavandula angustifolia oil induces oxidative stress, stiffening of membranes, and cell wall in Cryptococcus spp.
Authors: Calegari-Alves Yohana Porto , da Rosa Rafael Lopes , Costa Renata Pereira , Innocente-Alves Camila , Faustino Aline Martins , Yates John R. , Beys-da-Silva Walter Orlando , Santi Lucélia
Published: December 2024

The Cryptococcus neoformans and Cryptococcus gattii species complexes are the etiological agents of cryptococcosis, a disease responsible for 181 000 deaths annually worldwide due to late diagnosis and limited treatment options. Studies focusing on the identification of new substances with antifungal activity, such as essential oils (EOs), are urgently needed. While the antifungal effects of EO have already been suggested, their mechanism of action at the molecular level still requires evaluation. In this work, we assessed the molecular changes induced by the exposure of Cryptococus neoformans (H99) and Cryptococcus deuterogatti (R265) to lavender essential oil (LEO) using a morphological and proteomics approach. The identified proteins were categorized by Gene Ontology according to biological processes and molecular functions, and Kyoto Encyclopedia of Genes and Genomes pathway analysis was also conducted. Our findings indicate that LEO creates a stressful environment in both strains; however, the response to this stimulus differs between the two species. In C. neoformans, changes were observed in energy metabolism and pathways related to alternative sources of energy and oxidative stress response. In C. deuterogatti, changes were identified in pathways related to cellular architecture, implying that the cell underwent morphological changes such as membrane and cell wall stiffening.
A cosmological reconstruction of the Higgs vacuum expectation value
Authors: Chakrabarti Soumya , Anagha V. , Ganesh Selva , Menon Vivek
Published: December 2024

We present a simple toy model of cosmic acceleration driven purely by a self-interacting scalar field embedded in theory of grand unification. The scalar self-interaction is Higgs-like and provokes a spontaneous symmetry breaking. The coefficient of the quadratic term in the self-interaction potential has an evolution and it leads to a cosmic variation of proton-to-electron mass ratio,

$$\mu $$

μ

. We perform a cosmological reconstruction from the kinematic parameter jerk and discuss a few cosmological consequences of the theory. We also compare the theoretically calculated

$$\mu $$

μ

variation with the observations of molecular absorption spectra from Cesium Atomic Clock data.
Maximal steered coherence in accelerating Unruh–DeWitt detectors
Authors: Li Hong-Wei , Fan Yi-Hao , Shen Shu-Ting , Yan Xiao-Jing , Li Xi-Yun , Zhong Wei , Sheng Yu-Bo , Zhou Lan , Du Ming-Ming
Published: December 2024

Quantum coherence, a fundamental aspect of quantum mechanics, plays a crucial role in various quantum information tasks. However, preserving coherence under extreme conditions, such as relativistic acceleration, poses significant challenges. In this paper, we investigate the influence of Unruh temperature and energy levels on the evolution of maximal steered coherence (MSC) for different initial states. Our results reveal that MSC is strongly dependent on Unruh temperature, exhibiting behaviors ranging from monotonic decline to non-monotonic recovery, depending on the initial state parameter

$$\Delta _0$$

Δ
0

. Notably, when

$$\Delta _0=1$$

Δ
0

=
1

, MSC is generated as Unruh temperature increases. Additionally, we observe that higher energy levels help preserve or enhance MSC in the presence of Unruh effects. These findings offer valuable insights into the intricate relationship between relativistic effects and quantum coherence, with potential applications in developing robust quantum technologies for non-inertial environments.