Diameter Range Research Articles

Numerical Reconstruction of Proton Exchange Membrane Fuel Cell Gas Diffusion Layers

Flooding and dehydration reduce stability and power performance in Proton Exchange Membrane Fuel Cells (PEMFCs). The Gas Diffusion Layer (GDL) plays a crucial role in facilitating reactant gas transport and removing product water from the electrode. To suit various PEMFCs, GDLs with different shapes have been commercialized. The impact of the GDL structure on the surface-tension-driven water transport behavior remains poorly understood. However, this is one important aspect that can be controlled by proper design. In this study, the GDL performance is investigated by comparing curved and straight carbon fibers within the region. Specifically, an image-processing method extracts porosity, domain size, and fiber diameter from an experimental image-based GDL reconstruction. These parameters are utilized by in-house developed computer codes to stochastically reconstruct curved and straight carbon fiber GDLs, respectively. The real and reconstructed GDLs are compared in terms of pore size distribution, tortuosity, and permeability. Liquid transport in these GDLs and corresponding gas channels is simulated using a volume of fluid method in OpenFOAM 7.0.Figure 1(a) presents the T-shaped simulation domain and top view of three GDLs. Figure 1(b) displays the Cumulative Density Function (CDF) of the pore size distribution for the three GDLs, revealing that the main difference between the three GDLs lies in the pore diameter range of 10-30 µm. Upon completion of the research program, we aim to identify the influence of fiber shape on the GDL transport properties as well as the water behavior inside them. Figure 1

Morphological analysis of polar landing regions for a solar powered ice drilling mission

Planning of mission toward the lunar polar region is supported here by the analysis and better understanding of the most frequent landforms: craters on the Moon in the polar region between 79.30 and 84.35 southern latitude. This work surveys impact crater morphologies and spatial density based age estimation and slopes for eight earlier selected, large candidate landing regions of the Luna-27 solar powered ice drilling mission at the southern lunar polar region. The morphological, morphometrical, slope and dating analysis provided the following results: The d/D values of craters follow the earlier found d/D trend for larger craters, but there is a scatter in depth values related to the ageing of craters. The occurrence of shallow craters looks to be somewhat more abundant here than at lower lunar latitudes, in agreement with Mahanti et al. (2015). Beside fresh craters, rock boulders also occur at some km sized local topographic elevations, indicating erosion of ∼1 m thick regolith layer by micro-scale impacts roughly on the scale of 100 Ma.Characteristic temporal sequence of change in the morphology of about 100 m-sized craters confirmed earlier results. The sequence starts from the freshest craters, with mass wasting produced stripes in the interior slope, later diminish of high-reflectance proximal ejecta happens, then boulders, and even later elevated rims diminish. The surveyed large terrains showed crater statistics-derived model ages ranged between 3.9 and 4.2 Ga, indicating below a thin pulverised surface regolith layer, the topography of the poorly fragmented bedrock below it still holds the Late Heavy Bombardment aged basement. The equilibrium crater population was possibly identified below the 100–200 m diameter range. Surveying crater retention at >30° slopes indicates exposure of 78–140 Ma for steep terrains, and 330–150 Ma for flat <5° slope surfaces considering the size domain below 100 m diameter. This observation indicates rejuvenation of the top few m thin layer of slopes produces faster mixing than on plains.The surveyed kilometre sized craters formed about 1–2 Ga ago, and show correlation between formation age and depth, indicating an infilling rate around 100 m thickness in 1 Ga duration. This is 2 orders of magnitude larger than the 1–2 m impact driven regolith mixing depth during the same period. Thus, while impact mixing desiccates the shallow top regolith layer, inside km scale craters earlier accumulated ice might still be there shielded by faster rock debris accumulation.The surveyed candidate landing regions were evaluated according to general landing safety, lower temperature (to support ice preservation), and solar illumination (for energy supply). Comparing the eight regions, altogether 5.1% of their total area was found to meet with the threshold values of slope angle below 8°, modelled 1 m deep subsurface temperature below 125 K and at least 20% of time available solar illumination and Earth visibility. The largest continuous area that fulfil the used constraints are present in the candidate LS8 area at −82.70°, −82.72°.

Pediatric evaluations for deep learning CT denoising.

Deep learning (DL) CT denoising models have the potential to improve image quality for lower radiation dose exams. These models are generally trained with large quantities of adult patient image data. However, CT, and increasingly DL denoising methods, are used in both adult and pediatric populations. Pediatric body habitus and size can differ significantly from adults and vary dramatically from newborns to adolescents. Ensuring that pediatric subgroups of different body sizes are not disadvantaged by DL methods requires evaluations capable of assessing performance in each subgroup. To assess DL CT denoising in pediatric and adult-sized patients, we built a framework of computer simulated image quality (IQ) control phantoms and evaluation methodology. The computer simulated IQ phantoms in the framework featured pediatric-sized versions of standard CatPhan 600 and MITA-LCD phantoms with a range of diameters matching the mean effective diameters of pediatric patients ranging from newborns to 18 years old. These phantoms were used in simulating CT images that were then inputs for a DL denoiser to evaluate performance in different sized patients. Adult CT test images were simulated using standard-sized phantoms scanned with adult scan protocols. Pediatric CT test images were simulated with pediatric-sized phantoms and adjusted pediatric protocols. The framework's evaluation methodology consisted of denoising both adult and pediatric test images then assessing changes in image quality, including noise, image sharpness, CT number accuracy, and low contrast detectability. To demonstrate the use of the framework, a REDCNN denoising model trained on adult patient images was evaluated. To validate that the DL model performance measured with the proposed pediatric IQ phantoms was representative of performance in more realistic patient anatomy, anthropomorphic pediatric XCAT phantoms of the same age range were also used to compare noise reduction performance. Using the proposed pediatric-sized IQ phantom framework, size differences between adult and pediatric-sized phantoms were observed to substantially influence the adult trained DL denoising model's performance. When applied to adult images, the DL model achieved a 60% reduction in noise standard deviation without substantial loss in sharpness in mid or high spatial frequencies. However, in smaller phantoms the denoising performance dropped due to different image noise textures resulting from the smaller field of view (FOV) between adult and pediatric protocols. In the validation study, noise reduction trends in the pediatric-sized IQ phantoms were found to be consistent with those found in anthropomorphic phantoms. We developed a framework of using pediatric-sized IQ phantoms for pediatric subgroup evaluation of DL denoising models. Using the framework, we found the performance of an adult trained DL denoiser did not generalize well in the smaller diameter phantoms corresponding to younger pediatric patient sizes. Our work suggests noise texture differences from FOV changes between adult and pediatric protocols can contribute to poor generalizability in DL denoising and that the proposed framework is an effective means to identify these performance disparities for a given model.

Effect of Variable Growth Conditions on Selected Anatomical Properties of Hungarian Turkey Oak Wood

Quercus cerris (Turkey oak) has been categorized as a drought-tolerant species because it can survive with rainfall below 400 mm/year, and it usually develops deep and penetrating taproots. This characteristic suggests that Turkey oak is a survival candidate species for the future environment with the predicted climate scenarios in Hungary. Potentially, Turkey oak could support a sustainable supply of timber to the Hungarian wood industry in the future, as the aesthetic value is similar to that of noble oaks. The objectives of the study are to determine 1; the selected micro-level wood properties (wood tissue characteristics) and 2; the selected macrolevel wood properties (tree-ring width, sapwood-heartwood ratio) for Turkey oak from two different sites. The heartwood portion for all trees constituted 67-82% of the cross-diameter. The growth-ring width decreased from pith to bark. The annual rings in the sapwood had a width value range of 1000 to 1600 μm; in heartwood 1600 to 2500 μm; in juvenile wood 2400 to 3300 μm. Soil quality and stand composition had a significant effect on growth-ring width. Fibre length ranged from 800.03 to 1305.59 m, whereas fibre-wall thickness varied between 11.73 and 18.51 μm, with soil quality and species composition having a highly significant influence. The earlywood parts of the growth rings had a vessel diameter range of 274.62-401.54 μm, whereas the latewood portion ranged from 46.50 to 190.08 μm. Overall, stand composition was a major source of variation in the properties studied.

Hydrological Analysis of Khargone Area, Khargone District, Madhya Pradesh, India

The paper is focused on hydrogeological analysis Khargone area, Khargone District, Madhya Pradesh, India. The study area typically consists of basalt rock formations dating from the Late Cretaceous to the Paleocene era of the Deccan Traps. The alluvium is clearly visible along the Kunda River's course. The hydrogeological examination of 70 open dug wells reveals well diameter range between 3 meters and 9 meters, Depth of well within the range of 6-7 m.b.g.l. Static water levels ranged from 1 m. to 17 m.b.g.l. The fluctuation ranges between 2 to 12 m respectively. The ground water level maps of post and pre monsoon periods indicate that in general the ground water movement is towards the kunda River. The suitable sites for ground water development have been suggested in the villages of Nangalda, Ibrampura, Thibgaon Khurd and Dongargaon.

A proposal for a constitutive equation fitting methodology for the rheological behavior of drilling fluids at different temperatures and high-pressure conditions

Drilling fluids are complex suspensions of particles with a wide diameter range. While extensive research has explored the rheological behavior of drilling fluids, several limitations still exist. High-pressure and high-temperature (HPHT) conditions encountered in drilling fluids have introduced unique challenges, and only a few studies have attempted to develop a comprehensive equation that addresses both aspects concurrently. This study aims to perform a rheological characterization of a water-based drilling fluid (WBDF) containing xanthan gum under HPHT conditions and propose a constitutive equation to fit rheological data in such conditions. The experiments were conducted using an Anton Paar MCR 702TD rotational rheometer, coupled with a pressure cell. Steady-state flow curves were obtained at three different temperatures (25, 55, and 100 °C) and pressures ranging from 100 to 800 bar. The experimental data were fitted to the power-law model, and the rheological parameters of the model were fitted with variations in temperature and pressure. The fluid exhibited shear-thinning behavior, with the influence of temperature being more predominant than the effect of pressure, however, both variables have a strong relationship. Furthermore, we proposed a methodology to establish an equation capable of predicting the shear stress of the drilling fluid under HPHT conditions. The equation was also compared with different drilling fluids tested on different rheometers. This equation demonstrated excellent predictive accuracy within the fitted range. The insights provided in this study hold substantial implications for the oil and gas industry, as predicting the rheological behavior of drilling fluids under varying temperatures and pressures within the annular region of the well is essential for efficient drilling planning, particularly in offshore fields.

Generation of microbubbles at high gas concentrations via cavitation

A novel method of continuous microbubble generation is proposed in which an air–water mixture is pressurized in a chamber (up to 47 atm), leading to complete gas dissolution, before being expelled through a restriction to induce bubble nucleation. This approach differs from existing methods for small-scale bubble generation due to the high pressure gas–liquid mixture, nucleation approach, and large gas concentrations, which range from saturation ratios of 2.85 to 9.56 at normal temperature and pressure. The flow of bubbles produced by the system is characterized through optical microscopy to determine the influence of various operating parameters on the volumetric bubble size distributions (VBSDs) at a fixed flow rate. In particular, the gas concentration, compressor pressure, restriction diameter, and restriction length are varied for two classes of restrictions: capillaries with large length-to-diameter ratios, and orifices with comparatively low ratios. VBSDs are modestly polydisperse under all conditions, but with tunable distributions in the 10–70 μm diameter range. The VBSDs for each configuration collapse when non-dimensionalized by the Sauter mean diameter, which provides an opportunity to describe bubble size distributions using a predictor model for this reduced order quantity. The coefficients from the predictor model reveal a low sensitivity of the Sauter mean diameter to the gas concentration and a reduction of bubble diameters when the residence time of solution in the restriction is decreased. Analysis of the technique of bubble generation yields an energy balance to quantify the relative energy ratio of the bubble generation process, which is presently less than 0.2%. Insight from the energy balance suggests that the process could be optimized to generate smaller bubbles.

Continuous gas-phase synthesis of iron nanoparticles at ambient conditions with controllable size and polydispersity

HypothesisBy altering aerosol growth dynamics with unipolar charges, one can obtain aerosols with narrow particles size distributions, a highly desirable feature in applications of functional nanoparticles. ExperimentsUnlike liquid colloid systems, aerosol particles in the free molecular regime undergo coarsening due to Brownian coagulation and will eventually attain a self-preserving size distribution with a typical geometric standard deviation of 1.46 - 1.48. We developed a novel continuous one-step aerosol synthesis reactor that produces iron nanoparticles from ferrocene at ambient conditions, which confines the site of precursor breakdown and particle formation in the downstream vicinity of a positive corona discharge. FindingsWe demonstrated that the particle size could be controlled within 3 - 10 nm with a suppressed geometric standard deviation (1.15 - 1.35). The as-produced iron nanoparticles were successfully used as catalyst for the growth of single-walled carbon nanotubes with a narrow diameter range. With a transient aerosol dynamics model, we showed that a fraction (as small as 0.1%) of unipolar-charged particles could have a significant impact on the aerosol growth dynamics, which eventually results in a narrower particle size distribution with smaller size and higher number concentrations.

Normative MRI for Lumbar Spinal Canal and Vertebral Body Dimensions in a Jordanian Population Sample

Aim: To provide normal values for the lumbar spinal canal, lumbar vertebral body and dural sac dimensions and canal body ratio by MRI for a Jordanian population sample.&#x0D; Material and methods: Three well trained observers reviewed 218 lumbar MRI scans performed between 2019–2021 (1090 lumbar levels) and obtained from the central computerized medical archive of three main governmental hospitals in north, central and south Jordan. All MRIs with alignment abnormalities (scoliosis and kyphosis), canal compression, vertebral disease (including fractures) or technical artifacts were excluded. The following were measured from L1 to L5 levels: the midsagittal diameters of the spinal canal and vertebral body, axial anteroposterior (AP), and transverse diameter of the vertebral body, dural canal and dural canal area. Data on sex and age were also documented.&#x0D; Results: The studied MRI scans included 113 males (51.8%) and 105 females (48.2%). Age ranged between 23–86 years old (mean 52.23 ± 13.125). The mid sagittal mid vertebral AP diameter of the lumbar spine range was 2.8–3.1 cm. The mid sagittal spinal canal diameter range was 1.3–1.5 cm. Canal body ratio was 3.3–3.6. The AP, transverse dural sac diameter ranges were 1.2–1.4 cm and 1.5–1.9 cm, respectively. Finally, the dural sac area ranged from 331–362 mm2.&#x0D; Conclusion: The dimensions of the lumbar spinal canal, vertebral bodies, and vertebral canal ratio at all levels were documented for a Jordanian population sample. Dimensions varied according to sex and when compared with other ethnic groups (Asian and African). The findings suggest that canal stenosis criteria should take these differences into consideration.

Statistical distribution of micro and macro pores in acrylic bone cement- effect of amount of antibiotic content

Aseptic loosening due to mechanical failure of bone cement is considered to be a leading cause of revision of joint replacement systems. Detailed quantified information on the number, size and distribution pattern of pores can help to obtain a deeper understanding of the bone cement's fatigue behavior. The objective of this study was to provide statistical descriptions for the pore distribution characteristics of laboratory bone cement specimens with different amounts of antibiotic contents. For four groups of bone cement (Palacos) specimens, containing 0.3, 0.6, 1.2 and 2.4 wt/wt% of telavancin antibiotic, seven samples per group were micro computed tomography scanned (38.97 μm voxel size). The images were first preprocessed in Mimics and then analyzed in Dragonfly, with the level of threshold being set such that single-pixel pores become visible. The normalized pore volume data of the specimens were then used to extract the logarithmic histograms of the pore densities for antibiotic groups, as well as their three-parameter Weibull probability density functions. Statistical comparison of the pore distribution data of the antibiotic groups using the Mann–Whitney non-parametric test revealed a significantly larger porosity (p < 0.05) in groups with larger added antibiotic contents (2.4 and 0.6 wt/wt% vs 0.3 wt/wt%). Further analysis revealed that this effect was associated with the significantly larger frequency of micropores of 0.1–0.5 mm diameter (p < 0.05) in groups with larger antibiotic content (2.4 wt/wt% vs and 0.6 and 0.3 wt/wt%), implying that the elution of the added antibiotic produces micropores in this diameter range mainly. Based on this observation and the fatigue test results in the literature, it was suggested that micropore clusters have a detrimental effect on the mechanical properties of bone cement and play a major role in initiating fatigue cracks in highly antibiotic added specimens.

Particle-wall hydrodynamic effects on optical trapping viscometry

Optical tweezers are a versatile setup used to measure forces in soft materials and characterize the rheological properties of fluids and gels. An accurate measurement of these forces is complicated by the interaction between the optically trapped materials and nearby substrate walls. This work presents a comprehensive Brownian Dynamic (BD) model that accounts for the hydrodynamic interactions between an optically trapped particle and a nearby boundary. The model is based on a midpoint algorithm, which simplifies accounting for diffusion gradients that arise from hydrodynamic interactions. Experiments using an optical tweezer and a quadrant position detector (QPD) are performed to validate these experiments. We conduct experiments by varying input laser current from 100 mA to 300 mA. Our experiments show that measured viscosity at 100 mA is ∼19% higher than the value expected for room temperature water (0.89 mPa-s). The discrepancy diminishes to 4% when a 300 mA current is used. Simulations performed with the BD model show that, for a nominal spring constant of ks=4.332×10−4IlaserpN/μm, the discrepancy can be explained via hydrodynamic interactions that influence the measured effective viscosity. Wide variability in confidence interactions observed in our data can be replicated by using a range of diameters in our simulation. This is consistent with DLS measurements of the particles used in this study, which show that the mean diameter was (1.63 ± 0.28) μm. This work has implications for measuring Newtonian media viscosities up to ∼63 mPa-s, as determined by a scaling analysis of limitations for our measurement system.

Revision of total hip arthroplasty by long locking stem with fully hydroxyapatite-coated modular metaphysis (Reef™): A continuous series of 78 cases at a minimum 2-year follow-up

IntroductionSince the Wagner and Vives stems were introduced in the 1980s, the range of uncemented implants for femoral revision has grown with increasing demand. Cementless modular implants with a wide range of lengths and diameters improved adaptation to the bone and secondary metaphyseal integration. Data are sparse for the Reef™ locking stem (Depuy-Synthes, Saint-Priest, France) and we therefore conducted a retrospective study at more than 2 years’ follow-up, in a continuous series of total hip arthroplasty (THR) revision procedures using this long fully-hydroxyapatite-coated modular locking stem, assessing (1) implant survival, (2) clinical and functional results, and (3) radiographic results. HypothesisThe study hypothesis was that all-cause≥2-year survival is>90%. Patients and methodsBetween 2007 and 2018, 413 femoral stem exchanges were performed in our center, a Reef™ model being needed in 93 cases. Etiologies comprised: Vancouver B2 or B3 periprosthetic fracture (57%, n=53), aseptic loosening (33%, n=30), septic loosening (10%, n=9) and 1 case of aseptic non-union under the stem (1%, n=1). Clinical and functional assessment used Harris Hip Score (HHS), Postel Merle d’Aubigné score (PMA) and Oxford-12 Hip Score (OHS). Radiographic assessment used immediate postoperative views and last follow-up radiographs, assessing osseointegration, filling index and stress shielding. Implant survival was estimated following Kaplan-Meier with 95% confidence intervals. ResultsMean follow-up was 6±3 years (range, 2–12). Last follow-up included 78 cases for analysis (12 deaths [13%] and 3 patients lost to follow-up before 2 years [3%]). Ten-year Reef™ implant survival was 98.7% (95% CI: 96.3–100) free of aseptic loosening (n=1) and 94% (95% CI: 87–100) for all causes (n=3). The failures related to aseptic loosening involved femoral stem fracture away from the modular part; the 2 cases of septic loosening did not undergo reimplantation for medical reasons. Preoperatively (scheduled surgeries, excluding periprosthetic fractures: n=40), mean HHS was 43±12 and 77±12 at last follow-up (81±13 in scheduled surgery [n=40] and 73±11 in emergency surgery for periprosthetic fracture [n=53]), mean PMA score was 13±2 and mean OHS was 26±9. The infection rate was 11% (n=9) including 7.6% new infection (n=6). The dislocation rate was 6% (n=5). The radiographic stress shielding rate was 11% (n=9) and significantly associated with low metaphyseal filling index (76±7% vs. 83±8% [p=0.009]). DiscussionLike other recent data, the present good survival results support the trend for uncemented stems in femoral revision, as encouraged by the 1999 symposium of the French Society of Orthopedic Surgery and Traumatology (SoFCOT). Primary diaphyseal fixation enables secondary metaphyseal integration on an implant with modularity ensuring good bone adaptation. Close contact between the bone and hydroxyapatite surfaces is a key-point in the surgical strategy. Level of evidenceIV, retrospective study.

A vertically translating collection system to facilitate roll-to-roll centrifugal spinning of highly aligned polyacrylonitrile nanofibers

Centrifugal spinning is a fiber spinning method capable of producing fibers in the nanoscale diameter range from a multitude of polymers, including polyacrylonitrile (PAN). With a traditional centrifugal spinner, fiber can be rapidly spun and collected on static collection posts. However, the use of posts inevitably forms a dense fiber “ring” that is incompatible with roll-to-roll manufacturing processes. In this work, factors that influence throughput and scalability of highly aligned centrifugally spun PAN fibers are explored. A custom centrifugal setup is used to vertically translate collected fibers during the spinning process to distribute them over a large surface area. In addition, factors that affect PAN fiber diameter during the spinning process are investigated, including spinneret to collector distance, rotational speed, and humidity. Resulting data demonstrates that these factors can be independently optimized to reliably produce quality PAN fiber in the nanoscale diameter range. Furthermore, the fiber mass collection rate can be increased without affecting sample quality when the vertical translation speed is increased. This work demonstrates the potential scalability of centrifugal spinning to quickly produce large amounts of highly aligned nanofiber in a cheap, efficient, and reliable manner, and also lends the ability to be collected in a roll-to-roll fashion.

Mapping microarchitectural degeneration in the dilated ascending aorta with ex vivo diffusion tensor imaging.

Thoracic aortic aneurysms (TAAs) carry a risk of catastrophic dissection. Current strategies to evaluate this risk entail measuring aortic diameter but do not image medial degeneration, the cause of TAAs. We sought to determine if the advanced magnetic resonance imaging (MRI) acquisition strategy, diffusion tensor imaging (DTI), could delineate medial degeneration in the ascending thoracic aorta. Porcine ascending aortas were subjected to enzyme microinjection, which yielded local aortic medial degeneration. These lesions were detected by DTI, using a 9.4 T MRI scanner, based on tensor disorientation, disrupted diffusion tracts, and altered DTI metrics. High-resolution spatial analysis revealed that fractional anisotropy positively correlated, and mean and radial diffusivity inversely correlated, with smooth muscle cell (SMC) and elastin content (P < 0.001 for all). Ten operatively harvested human ascending aorta samples (mean subject age 61.6 ± 13.3 years, diameter range 29-64 mm) showed medial pathology that was more diffuse and more complex. Nonetheless, DTI metrics within an aorta spatially correlated with SMC, elastin, and, especially, glycosaminoglycan (GAG) content. Moreover, there were inter-individual differences in slice-averaged DTI metrics. Glycosaminoglycan accumulation and elastin degradation were captured by reduced fractional anisotropy (R2 = 0.47, P = 0.043; R2 = 0.76, P = 0.002), with GAG accumulation also captured by increased mean diffusivity (R2 = 0.46, P = 0.045) and increased radial diffusivity (R2 = 0.60, P = 0.015). Ex vivo high-field DTI can detect ascending aorta medial degeneration and can differentiate TAAs in accordance with their histopathology, especially elastin and GAG changes. This non-destructive window into aortic medial microstructure raises prospects for probing the risks of TAAs beyond lumen dimensions.

A statistical analysis of exhaled respiratory droplet trajectory distribution in view of assessing the risk of infectious disease transmission

In the present work an analytical model of exhaled droplet trajectory and evaporation is employed to perform a preliminary statistical analysis of the droplet spatial distribution. The analysis is carried out for a set of over twenty thousand droplets distributed in the range of diameters from 0.1 μm to 1 mm. The type of respiratory events modelled are mouth breathing and speaking. The analytical model employed has been recently developed by the authors. It implements the fundamental laws of fluid dynamics and convection-diffusion, and features a 2D empirical numerical model of buoyant intermittent jet modelling the exhaled breath cloud. A discrete random walk turbulent dispersion model is also included allowing statistical analysis of the droplet trajectory to be performed. With proper boundary conditions any type of respiratory event can be simulated making the model particularly versatile. From the analysis, spatial virus concentration maps are derived for the largest droplets falling to the ground, and for the smaller droplets remaining airborne in the area in front of an infected emitter and successively uniformly dispersed in the ambient. This allows to estimate the risk of infection by fomite, direct inhalation and indirect inhalation routes, and provide a better understanding of infectious disease transmission risks.

Experimental study of the fuel spray and ignition characteristics in an aeroengine afterburner under subatmospheric pressure

The fuel atomization and ignition characteristics of an afterburner under subatmospheric pressure are important foundations for expanding the operating range of the afterburner at high flight altitudes. In this work, the lean ignition limits of the afterburner at subatmospheric pressure were obtained through experiments, and the fuel droplet size distribution and ignition process in the afterburner were acquired using a laser particle sizer and a high-speed camera. The results showed that the ignition equivalence ratio increased as the inlet pressure decreased and was lowest when the flame stabilizer blockage ratio was 0.3. When the inlet pressure of the combustor decreased from high pressure to subatmospheric pressure, the Sauter mean diameter (SMD) range of the fuel droplets increased from 60∼110 μm to 100∼190 μm due to the increase in the ignition equivalence ratio and the deterioration of the fuel atomization characteristics. Under subatmospheric pressure, the flame residence phase time in the ignition process decreases significantly, while the flame intensity fluctuates more dramatically during the flame growth phase due to the decrease in the equivalence ratio of the gaseous phase, the larger fuel droplet size, and the uneven fuel distribution. When the inlet pressure is high pressure, the flame propagates from the ignition position to the trailing edge of the flame stabilizer first and anchors within the shear layer behind the flame stabilizer, whereas under subatmospheric pressure, the flame does not propagate to the anchoring point in the first place, which is one reason for the difficulty of ignition of combustors under high-altitude conditions.

Select the Right Biopsy Needle for You and Your Embryos

Biopsy pipettes come in multiple versions, and precision, choice and control are essential. Pipettes are specially designed and polished to minimize damage and protect cell membranes during PGT procedures. Characteristics of some pipettes are • Internal diameter range: from 15 μm to 35 μm • 15 μm for polar body biopsy • 25 μm for trophectoderm biopsy • 30 to 35 μm for blastomere biopsy The pipettes should be manufactured with quality assured materials that are MEA and endotoxin (LAL) tested. All stages of production should be controlled, from the raw materials to the final product. Every single pipette should be checked for dimensions to minimise LOT-to-LOT variation. Some pipettes are made of borosilicate glass that helps prevent the risk of oil clogging the inner surface. All pipettes should have heat polished bases to ensure longevity of seals in your pipette holder. Choosing the exact micropipette tool best suited to your needs ensures a successful outcome.

Recessive and dominant inheritance patterns associated with synonymous differences in wool fibre curvature and medullation

ABSTRACT Segregation into lustrous and wild-type birth coats suggested both dominant and recessive inheritance patterns associated with birth coat and subsequently with low wool fibre curvature at lamb and yearling shearing. The hypothesis that these phenotypes also differ in the proportion of medullated fibres (%) was tested here. Progeny expressing dominant segregation of lustre at birth showed significant differences in medullation of lambs wool (P < 0.001), where 42.3% (SEM ± 6.5%) of fibres were medullated in the lustrous phenotype, and 4.8% (± 1.0%) in the wild-type. Medullation at yearling shearing had declined to 19.7% (± 5.3%) and 1.8% (± 0.3%) respectively but the significant difference prevailed (P < 0.001). Progeny expressing recessive segregation of lustre also exhibited more medullation as lambs (54.6% ± 6.0%) with only 9.5% (± 2.6%) in the wild-type (P < 0.001). Again, medullation declined in yearlings but the difference (P < 0.001) between phenotypes remained (22.6 ± 8.2 vs. 4.0 ± 1.7%). For both inheritance patterns medullation increased as fibre diameter increased in lambs wool (P < 0.001), but across the range of fibre diameter observed, more fibres were medullated in those lustrous at birth (P = 0.001).

Flow regime transition and bubble behavior in gas-liquid two-phase impinging jet reactor

The gas-liquid flow regimes transition mechanism and bubble behavior in gas-liquid two-phase impinging jet reactor are studied by numerical method. The liquid phase velocity, gas-liquid flow regimes, bubble behavior in the impinging reactor under different gas and liquid velocities are analyzed to explore. The vortex in flow field changes periodically, and the period is 7.5 s. According to the dispersion mode of bubbles in the reactor, the gas-liquid flow regimes can be divided into three regimes: cluster upflow, gradual dispersion and complete dispersion. The critical condition equations of flow regimes transition are established combination of Flow number (Fl) and Froude number (Fr). The distribution range of bubble diameter in the reactor increases with the increase of gas velocity and decreases with the increase of liquid velocity. The turbulent kinetic energy, turbulent dissipation rate and the velocity in the flow field are gradually weakens from the impact center to the radial direction. Based on dimensionless analysis, the mathematical model of bubble Sauter diameter is established to predict bubble Sauter diameter accurately. This research provides a theoretical basis for the amplification and optimization of reactors.

Mechanical properties of Okuzgozu (Vitis vinifera L. cv.) grapevine canes

BackgroundThe mechanical properties of Okuzgozu grapevine canes influence pruning and harvesting techniques, grape quality, and the feasibility of using mechanical harvesters. MethodsThis study determined the optimal cutting qualities for the native Okuzgozu grape variety (Vitis vinifera L.) over a range of phenological stages and cane diameters. The cutting tests of canes were performed at different growth periods (veraison, 15 days after veraison and harvesting time). A universal material testing equipment was used to investigate the cutting characteristics of the material. ResultsThe results indicate that both phenological stages and diameter significantly impacted measured cutting characteristics of grapevine canes. Cutting strength, cutting force, cutting energy and upper bio-yield force gradually decreased with phenological stages. All average maximum values were obtained during the veraison stage. At this stage, the highest values for cutting strength, cutting force, cutting energy, and upper yield were measured at 13.16 MPa, 774.55 N, 5.94 J, and 631.60 N, respectively. The lowest values were recorded at 9.63 MPa, 568.42 N, 3.33 J, and 513.13 N. A close relationship was observed between cane diameter and cutting energy. The energy requirement decreased linearly with decreasing cane diameter. ConclusionThe maximum cutting energy and force values were calculated at an internode 5 (IN5) as 7.34 J and 995.49 N respectively, the minimum cutting energy and force values were calculated at internode 1 (IN1) as 1.85 J and 385.52 N, respectively.