Tortuosity Values Research Articles

The influence of overnight orthokeratology and soft contact lens on the meibomian gland evaluated using an artificial intelligence analytic system

PurposeTo test the changes of meibomian gland (MG) morphology using an artificial intelligence (AI) analytic system in asymptomatic children wearing overnight orthokeratology (OOK) and soft contact lens (SCL). MethodsA retrospective study was conducted including 89 participants treated with OOK and 70 participants with SCL. Tear meniscus height (TMH), noninvasive tear breakup time (NIBUT), and meibography were obtained using Keratograph 5 M. MG tortuosity, height, width, density, and vagueness value were measured using an artificial intelligence (AI) analytic system. ResultsIn an average of 20.80 ± 10.83 months follow-up, MG width of the upper eyelid significantly increased and MG vagueness value significantly decreased after OOK and SCL treatment (all P < 0.05). MG tortuosity of the upper eyelid significantly increased after OOK treatment (P < 0.05). TMH and NIBUT did not differ significantly pre- and post- OOK and SCL treatment (all P > 0.05). The results from the GEE model demonstrated that OOK treatment positively affected MG tortuosity of both upper and lower eyelids (P < 0.001; P = 0.041, respectively) and MG width of the upper eyelid (P = 0.038), while it negatively affected MG density of the upper eyelid (P = 0.036) and MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). SCL treatment positively affected MG width of both upper and lower eyelids (P < 0.001; P = 0.049, respectively) as well as MG height of the lower eyelid (P = 0.009) and tortuosity of the upper eyelid, (P = 0.034) while it negatively affected MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). However, no significant relationship was found between the treatment duration and TMH, NIBUT, MG morphological parameters in OOK group. SCL treatment duration negatively affected MG height of the lower eyelid (P = 0.002). ConclusionsOOK and SCL treatment in asymptomatic children can influence MG morphology. The AI analytic system may be an effective method to facilitate the quantitative detection of MG morphological changes.

Experimental Study of Oxygen Depletion Effects on Soot Morphology and Nanostructure in Coflow Diffusion Aviation Fuel (RP-3) Flames

Oxygen concentration is a significant factor affecting soot formation and oxidation. However, there are few studies that have focused on the morphology and nanostructure characteristics of soot in aviation kerosene, oxygen-depleted combustion flames. In the present paper, five coflow flames under initial oxygen volume concentrations of 18.5%, 19%, 20%, 21%, and 23.5% were studied. The pneumatic probe sampling method and high-resolution transmission electron microscopy (HRTEM) analysis were conducted to quantify the morphology and nanostructure parameters, and laser extinction (LE) was applied to determine the soot volume fraction. Among the cases of different oxidizer oxygen concentrations (23.5% to 18.5%), the change in soot volume fraction was quantified, and the degree of graphitization of soot particles, i.e., the maturity, were compared. The results show that the peak value of soot volume fraction of the flames increased by 0.73 ppm as the oxygen concentration increased from 21% to 23.5%, and decreased by 1.25 ppm as the oxygen concentration decreased from 21% to 18.5%. When the oxygen concentration decreased from 23.5% to 18.5%, the soot primary particle diameter at the same dimensionless height decreased and then increased, which was attributed to the competition between the changes in the residence time and the growth rate of the soot particles. The quantitative analysis results of the soot nanostructure suggested that reduced oxygen concentration inhibited the graphitization process of carbon lattices and decreased the maturity and oxidation resistance of soot. When the oxygen concentration decreased from 23.5% to 18.5% at the same dimensionless height, the mean fringe length decreased by an average of 0.18 nm, and the mean value of fringe tortuosity and spacing increased by an average of 0.053 and 0.035 nm.

Probing the Pore Structure of the Berea Sandstone by Using X-ray Micro-CT in Combination with ImageJ Software

During diagenesis, the transformation of unconsolidated sediments into a sandstone is usually accompanied by compaction, water expulsion, cementation and dissolution, which fundamentally control the extent, connectivity and complexity of the pore structure in sandstone. As the pore structure is intimately related to fluid flow in porous media, it is of great importance to characterize the pore structure of a hydrocarbon-bearing sandstone in a comprehensive way. Although conventional petrophysical methods such as mercury injection porosimetry, low-pressure nitrogen or carbon dioxide adsorption are widely used to characterize the pore structure of rocks, these evaluations are based on idealized pore geometry assumptions, and the results lack direct information on the pore geometry, connectivity and tortuosity of pore channels. In view of the problems, X-ray micro-CT was combined with ImageJ software (version 1.8.0) to quantitatively characterize the pore structure of Berea Sandstone. Based on its powerful image processing function, a series of treatments such as contrast enhancement, noise reduction and threshold segmentation, were first carried out on the micro-CT images of the sandstone via ImageJ. Pores with sizes down to 2.25 μm were accurately identified. Geometric parameters such as pore area, perimeter and circularity could thus be extracted from the segmented pores. According to our evaluations, pores identified in this study are mostly in the range of 30–180 μm and can be classified into irregular, high-circularity and slit-shaped pores. An irregular pore is the most abundant type, with an area fraction of 72.74%. The average porosity obtained in the image analysis was 19.10%, which is fairly close to the experimental result determined by a helium pycnometer on the same sample. According to the functional relationship between tortuosity and permeability, the tortuosity values of the pore network were estimated to be in the range of 4–6 to match the laboratory permeability data.

Abstract Number ‐ 11: Automated Measurement Of Vascular Tortuosity: Association With Baseline Clinical Characteristics And Impact On Mechanical Thrombectomy

Introduction Vascular tortuosity is considered one of the main hurdles that may negatively impact mechanical thrombectomy in stroke treatment, delaying catheter access to the occluded vessel. Automatic characterization of anatomical vascular features may help in the planification of endovascular interventions. We developed a fully automatic algorithm for vascular tortuosity measurement and explored the association of several anatomical features with baseline characteristics and procedural outcomes. Methods An automatic software integrating segmentation, centerline extraction and vessel labelling, was used to extract features directly from computed tomography angiograms (CTA) of stroke patients undergoing transfemoral endovascular treatment.Mean vessel diameter and tortuosity index (TI) of the carotid arteries and brachiocephalic trunk were used as relevant tortuosity indicators. Patients were compared according to six different clinical conditions(gender, hypertension, dyslipidemia, diabetes, obesity and atrial fibrillation). Tortuosity values were also correlated with age.Patients with an anterior circulation stroke were further classified according to four procedural measures:time from groin puncture to first angiographic run, time to first retrieval attempt, time to revascularization. Results A sample of 558 patients with acute ischemic stroke who underwent mechanical thrombectomy at our medical center were included in this study. Forty patients (7.2%) were discarded due to sub‐optimal segmentation (n = 30) or processing errors (n = 10), leaving a final sample size of N = 518 (51% female, 74.8±12.9 years). Women presented significantly smaller mean diameter for all analyzed vessels (p &lt; 0.01) and an increased TI for both carotid arteries(p &lt; 0.01). Age was significantly correlated with increased TI in all analyzed vessels (0.35£r£0.52;p &lt; 0.01) Patients with hypertension and/or atrial fibrillation displayed significantly higher TI in both carotid arteries (p &lt; 0.01). Additionally, the brachiocephalic trunk was found to be more tortuous in patients with atrial fibrillation (p &lt; 0.01). A higher TI in all ipsilateral carotid segments was associated with higher times to first angiographic run and to final revascularization (p &lt; 0.05). A TI from the ipsilateral carotid segment over 0.28 independently predicted difficult catheter access (time to first angiographic run &gt;40 min, 3.8% of cases) with a sensitivity of 0.92 and a specificity of 0.68. Conclusions An automated software was successfully used to characterize the anatomical vascular features from CTA. Gender, age, hypertension and atrial fibrillation were found to significantly influence vascular tortuosity in anterior circulation arteries. Patients with difficult catheter access and/or delayed revascularization presented higher TI of ipsilateral carotid arteries. Carotid TI emerged as a potential predictor of difficult catheter access.

Effect of a compressed separator on the electrochemical performance of Li-ion battery

This work investigates the effects of compressed separators on the electrochemical performance of Li-ion batteries (LIBs) and the underpinning mechanisms. Two typical commercial separators (polypropylene (PP) and polyethylene (PE)) with different compressive behaviours were used in this study. The tortuosity values of compressed PP and PE separators were determined using Electrochemical Impedance Spectrum (EIS) tests, showing that the PP separator has a higher tortuosity than that of the PE separator under given compressive stress. LIBs with the compressed PP and PE separators were tested for their capacity performance. It is found that the onset strain of densifications can be considered as the critical compressive strain for the significant reduction of LIB's capacity. The experimental observations are supported by COMSOL modelling results.

Plot investigation on rill flow resistance due to path tortuosity

The path tortuosity t is an indicator of rill morphology accounting for the deviation of the thalweg from a straight alignment. The effect of t on flow resistance has been little investigated for rills. This paper reports the results of a plot investigation aimed to establish the suitable accuracy of the rill thalweg measurement to determine the tortuosity parameter and to test the reliability of a theoretical flow resistance law. Four rills were incised in clay soil (CS) and clay-loam soil (LS) and shaped by a clear flow discharge. The three-dimensional Digital Terrain Models were created by the Structure from Motion technique. For rills on LS, an approximate thalweg was tracked by photo-interpretation, and a specific calculation routine was applied to identify the cross sections with a constant spacing d. The actual rill thalweg was obtained as the line joining the lowest points of these cross-sections. Among the different tested d values, d = 0.075 m was chosen to determine t. For both CS and LS, the Darcy-Weisbach friction factor f featured a non-monotonic relation with t, which was explained as the result of three additive components due to bed roughness, sediment transport, and localized energy losses due to curves. The effect of the former two components on f contrasts that of the third, resulting in a linearly decreasing f-t relationship and constant flow velocity for the three lowest tortuosity values, and an increased friction factor and reduced flow velocity for the highest tortuosity value. The flow resistance law was positively tested, and the predicted friction factor was dependent on t.

The Effect of Tortuosity on Permeability of Porous Scaffold.

In designing porous scaffolds, permeability is essential to consider as a function of cell migration and bone tissue regeneration. Good permeability has been achieved by mimicking the complexity of natural cancellous bone. In this study, a porous scaffold was developed according to the morphological indices of cancellous bone (porosity, specific surface area, thickness, and tortuosity). The computational fluid dynamics method analyzes the fluid flow through the scaffold. The permeability values of natural cancellous bone and three types of scaffolds (cubic, octahedron pillar, and Schoen's gyroid) were compared. The results showed that the permeability of the Negative Schwarz Primitive (NSP) scaffold model was similar to that of natural cancellous bone, which was in the range of 2.0 × 10-11 m2 to 4.0 × 10-10 m2. In addition, it was observed that the tortuosity parameter significantly affected the scaffold's permeability and shear stress values. The tortuosity value of the NSP scaffold was in the range of 1.5-2.8. Therefore, tortuosity can be manipulated by changing the curvature of the surface scaffold radius to obtain a superior bone tissue engineering construction supporting cell migration and tissue regeneration. This parameter should be considered when making new scaffolds, such as our NSP. Such efforts will produce a scaffold architecturally and functionally close to the natural cancellous bone, as demonstrated in this study.

CFD analysis on the optimization of POCS performances under randomical transformations: a bridge with open-cell foams

Periodic Open Cell Structures (POCS) have been considered as possible catalytic substrates, thanks to recent developments in the Additive Layer Manifacturing (ALM) technique. In this work, the impact of the POCS cell shape on mass transfer has been investigated through CFD simulations. An algorithm able to increase the wet surface of a simple cubic POCS has been developed, keeping constant the mean pore diameter and with negligible porosity variations. Catalytic performances of the substrates have been evaluated, suggesting the possibility to enhance the mass transfer properties of the POCS up to that of foams by continuous randomical transformation of its shape. A dedicated CFD multi-region solver has been used for this purpose, accounting for heat/mass transfer and catalytic reactions. Moreover, a fluid-dynamic approach has been proposed in order to estimate the value of tortuosity, investigating its dependency on the POCS randomization level and its effect on the flow field.

New insights into the effects of available space characteristics within graphite-based anodes on the accessibility of solvated Li-ions under fast charging conditions

Energy storage materials for energy storage system or electric vehicle should be able to supply high capacity quickly. Especially, Li-ion accessibility within graphite-based anodes is the key point to enhance mass transfer and the electrochemical performance. In terms of solvated Li-ion accessibility to the space, space in graphite-based anode is classified as two consecutive scales, channel and surface pores. A Li-ion transferrable channel is controlled by the calendering process, and surface pores are modified with a chemical vapor deposition surface coating to enhance the solvated Li-ion accessibility in each space. Cross-analysis of BET with small-angle X-ray scattering was conducted to determine whether each space is accessible and where the optimal point is. Finding correlations with the tortuosity value provided not only quantitative but also geometrical information on the space which was derived from the making process of each electrode, reflecting actual solvated Li-ion movement. This study not only suggests two distinguishable views in enhancing the accessibility of solvated Li-ions but also presents new insights to figure out how the changes in space characteristics affect the electrochemical performance. Furthermore, these findings could provide a potential strategy to estimate commercialized graphite such that the actual solvated Li-ion movement can be interpreted.

Diagenetic overprint on porosity and permeability of a combined conventional-unconventional reservoir: Insights from the Eocene pelagic limestones, Gulf of Suez, Egypt

Lower to Middle Eocene organic-rich deep-water limestones of the ∼335-m-thick (1100 ft) Radwany (Thebes-equivalent) Formation represent a source rock and a potential reservoir unit at the October Oil Field in the Gulf of Suez. However, in spite of recent exploration advances, the pore system and diagenetic history of the formation are still poorly understood. This study aims to discriminate porosity types and their vertical distribution, assess the diagenetic processes controlling porosity evolution, and evaluate the unit's overall reservoir potential. To achieve these goals, we utilized an integrated petrographic, mineralogical, geochemical and petrophysical dataset from four offshore wells. At October Oil Field, the Radwany Formation is informally divided into three intervals (from the base up: C, B and A) which are composed of planktonic foraminiferal wackestone, wackestone-packstone and packstone microfacies. Pores include both fabric selective (interparticle, intraparticle and moldic) and non-fabric selective (fracture) types. Visible porosity reaches up to 11.6%, and the highest porosity values are associated with interparticle pores in foraminiferal packstone in interval C. The two overlying intervals have lower porosities but have TOC values of up to 6 wt %. The Nuclear Magnetic Resonance (NMR) analysis yields low amplitudes of short T2 components (max. 52 ms), which suggests the presence of small pores (intraparticle, moldic, fracture, and fissure). Based on the electrical quality index (EQI) rock classification, nine groups were identified, suggesting a high heterogeneity of the formation. The highest EQI values positively correlate with high porosity (visible and estimated) in the lower part of Interval C which is dominated by interparticle/intraparticle porosity, thus reflecting the low tortuosity values of this microfacies. Dominantly low EQI values in Intervals A and B indicate low porosity efficiency and higher tortuosity. Carbonate sediments of the Radwany Formation are interpreted to have undergone a complex series of diagenetic processes. These processes modified the primary pore system either by enhancing the reservoir properties (dissolution and fracturing), or by reducing or destroying porosity (cementation, mechanical and chemical compaction, and minor pyritization, chertification, and asphaltene precipitation). The study highlights the unconventional reservoir potential of the middle and upper parts of the Radwany Formation (intervals B and A) at October Oil Field, and the conventional reservoir potential of interval C. It emphasizes the complexity of diagenetic controls on the porosity evolution in deep-water limestones of the Gulf of Suez, and may provide valuable insight into similar deep-water carbonate systems in rift basin reservoirs elsewhere.

Tortuosity of branch retinal artery is more associated with the genesis and progress of diabetic retinopathy.

ObjectiveThe purpose of this study is to investigate the potential of using the tortuosity of branch retinal artery as a more promising indicator for early detection and accurate assessment of diabetic retinopathy (DR).Design and methodThe diagnoses, consisting of whether DR or not as well as DR severity, were given by ophthalmologists upon the assessment of those fundus images from 495 diabetic patients. Meanwhile, benefiting from those good contrast and high optical resolution fundus images taken by confocal scanning laser ophthalmoscope, the branch arteries, branch veins, main arteries and main veins in retina can be segmented independently, and the tortuosity values of them were further extracted to investigate their potential correlations with DR genesis and progress based on one-way ANOVA test.ResultsFor both two comparisons, i.e., between non-DR group and DR group as well as among groups with different DR severity levels, larger tortuosity increments were always observed in retinal arteries and the increments in branch retinal vessels were even larger. Furthermore, it was newly found that branch arterial tortuosity was significantly associated with both DR genesis (p=0.030) and DR progress (p<0.001).ConclusionBased on this cohort study of 495 diabetic patients without DR and with different DR severity, the branch arterial tortuosity has been found to be more closely associated with DR genesis as well as DR progress. Therefore, the branch arterial tortuosity is expected to be a more direct and specific indicator for early detection of DR as well as accurate assessment of DR severity, which can further guide timely and rational management of DR to prevent from visual impairment or even blindness resulting from DR.

Characterization of optical clearing mechanisms in muscle during treatment with glycerol and gadobutrol solutions.

The recent increasing interest in the application of radiology contrasting agents to create transparency in biological tissues implies that the diffusion properties of those agents need evaluation. The comparison of those properties with the ones obtained for other optical clearing agents allows to perform an optimized agent selection to create optimized transparency in clinical applications. In this study, the evaluation and comparison of the diffusion properties of gadobutrol and glycerol in skeletal muscle was made, showing that although gadobutrol has a higher molar mass than glycerol, its low viscosity allows for a faster diffusion in the muscle. The characterization of the tissue dehydration and refractive index matching mechanisms of optical clearing was made in skeletal muscle, namely by the estimation of the diffusion coefficients for water, glycerol and gadobutrol. The estimated tortuosity values of glycerol (2.2) and of gadobutrol (1.7) showed a longer path-length for glycerol in the muscle.

Investigation on effect of colloidal nano-silica on the strength and durability characteristics of red mud blended Portland cement paste through tortuosity

A novel binder system for cement-based composites depending upon the strength and durability characteristics is introduced in this study. The possibility of calcined red mud cement pastes with and without colloidal nano-silica (CNS) over Ordinary Portland Cement paste (OPC) at three W/B ratios (0.3, 0.4, 0.5) is evaluated. The optimum percentage of cement replacement by red mud (15%) was selected from compressive strength values of different cement replacements (5%, 10%, 15%, and 20%). Colloidal nano-silica (CNS) was added at 0.5%, 1%, 1.5%, and 2 % to the selected red mud cement paste. Water absorption, sorptivity, resistance to sulfate attack, and resistance to acid attack tests were conducted for optimum red mud cement paste with and without CNS. The experimental results are explained based on tortuosity with empirical formulas and mathematical models of pore network distribution. The tortuosity is directly proportional to the inter-connectivity of the pores. The mixes with 15% calcined red mud and 1.5% CNS replacement performed better strength and durability at all W/B ratios. The mix (R15NS1.5) with minimum tortuosity value results in the higher overall performance of the paste. The mixes with a 0.3 W/B ratio give high-performance cement paste compared to higher W/B ratios.

Microstructural and compaction characteristics of tropical black clay soil subgrade modified with lead-zinc mine tailings

Lead–Zinc Mine tailings (LZMT) are wastes generated after the extraction of lead and zinc from mined mineral ore, whose disposal mechanism is gradually becoming environmentally unfriendly. For effective recycling of LZMT, this present study utilized a combination of LZMT and Portland limestone cement (PLC) to improve the compaction and microstructural characteristics of tropical black clay soil (TBCS) for use in pavement design and construction. The LZMT and PLC were added to the expansive soil in varying proportions with mix ratios generated from Taguchi orthogonal array. The result obtained for the compaction characteristics showed that the maximum dry density (MDD) increased significantly when a combination of 20% LMZT and 4% PLC were blended with the expansive soil. The increase in the MDD was attributed to the formation of cementitious compounds. In addition, the optimum mix ratio obtained from the unconfined compressive strength of the TBCS, was used for the evaluation of the pore structure characteristics which included porosity, tortuosity and permeability. The result obtained from the analysis that was implemented with a combination of fractal geometry and Bradley and Roth adaptive thresholding image segmentation technique, indicates the possibility of a slight reduction in the strength properties of the modified soil due to its high level of porosity. Also, the permeability and tortuosity values obtained from the present study suggest a slight increase in the permeability of the modified soil-additive mixtures which may not be unconnected to the occurrence of pozzolanic reaction that resulted in the agglomeration and flocculation of the LZMT-PLC modified TBCS. Furthermore, microstructural analysis was executed on the modified TBCS and LZMT using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The result from the FTIR analysis indicates the pozzolanic character of LZMT in the presence of Si–O and Al–O tension bond with the bonds around 1000 cm−1 wavenumber, while the SEM analysis reveals the formation of a cementitious compound in the modified expansive soil-LZMT-PLC mixture.

Linking operating conditions of a GDI engine to the nature and nanostructure of ultrafine soot particles

Sub-23 nm particulate emissions from internal combustion engines have become a topic of interest for research and legislative regulations in recent years. Many studies focused on electrical mobility measurements of soot particles, but few works employed additional techniques that do not rely on equivalent diameters. In this work, exhaust-sampled soot from a 1.0 L gasoline direct injection engine was analysed by transmission electron microscopy (TEM). Three operating conditions were assessed: 1500 rpm fast-idle, 1500 rpm with 40 Nm and 1750 rpm with 20 Nm brake torque. A distinct mode of sub-10 nm particulates was found equally distributed on some sections of the TEM grids for all three conditions. These particulates appeared to be stable under the electron beam, suggesting a non-volatile nature. Differential mobility spectrometer measurements with and without catalytic stripper suggested the presence of volatiles but also indicated high levels of solid sub-23 nm particulates. Furthermore, more fractal soot agglomerates consisting of several primary particles were also observed by TEM. The nanostructure of primary particles exhibited mainly core-shell nanostructures for all operating conditions. An additional amorphous layer was observed surrounding primary particles for 1500 rpm fast-idle. Amorphous particulates and crystalline regions in agglomerates were identified for 1750 rpm with 20 Nm brake torque. Fringe analysis of the nanostructures was conducted for all three samples, with preliminary findings indicating similar fringe lengths of ca. 1.04 nm and tortuosity values of around 1.16.

Electrical, Diffusional, Hydraulic, and Geometrical Tortuosity Anisotropy Quantification Using 3D Computed Tomography Scan Image Data

Summary Sedimentary rocks display complex spatial distribution of both pore space and solid components, impacting the directional dependence of physical phenomena such as electrical conduction, fluid flow, heat transfer, and molecular diffusion. The complexity of the pore space is often quantified by the concept of tortuosity, which measures the sinuosity of the connecting paths in the pore space. Tortuosity is an important quantity in formation evaluation as it impacts petrophysical properties such as permeability and formation factor. However, the existence of various techniques can lead to nonuniqueness in assessment of tortuosity. Furthermore, spatial variation of the solid components of the rocks occurring at the core-scale domain reflected in the connectivity and distribution of the minerals is typically not quantified. The objectives of this paper are (a) to quantify tortuosity and tortuosity anisotropy of porous media through estimation of electrical, diffusional, hydraulic, and geometrical tortuosity at the pore scale and core scale and (b) to compare electrical, diffusional, hydraulic, and geometrical tortuosity. We estimate tortuosity in the pore space of microcomputed tomography (micro-CT) scan images and in the most connected and abundant solid phase of whole-core CT scan images. We conduct numerical simulations of electric potential distribution, diffusion, and fluid flow and velocity distribution to estimate electrical, diffusional, and hydraulic tortuosity, respectively. To calculate geometrical tortuosity, we use the segmented pore space from micro-CT scan images to extract a pore network model and compute the shortest path of all opposing pores of the samples. Finally, tortuosity values obtained with each technique are used to assess the anisotropy of the samples. We applied the documented workflow to core- and pore-scale images. The CT scan images in the core-scale domain belong to a siliciclastic formation. Micro-CT scan images in the pore-scale domain were obtained from Berea Sandstone, Austin Chalk, and Estaillades limestone formations. We observed differences in estimates of direction-dependent electrical, diffusional, hydraulic, and geometrical tortuosity for both types of images. The highest numerical differences were observed when comparing streamline electrical and hydraulic tortuosity with diffusional tortuosity. The observed differences were significant in anisotropic samples. Differences in tortuosity estimates can impact the outcomes of rock physics models for which tortuosity is an input. The documented comparison provides insight in the selection of techniques for tortuosity estimation. Use of core-scale image data provides semicontinuous estimates of tortuosity and tortuosity anisotropy, which are typically not attainable using pore-scale images. Additionally, the semicontinuous tortuosity anisotropy estimates from whole-core CT scan images provide a tool for selection of best locations to take core plugs.

An analysis of the influence of transfer learning when measuring the tortuosity of blood vessels

Background and Objective: Convolutional Neural Networks (CNNs) can provide excellent results regarding the segmentation of blood vessels. One important aspect of CNNs is that they can be trained on large amounts of data and then be made available, for instance, in image processing software. The pre-trained CNNs can then be easily applied in downstream blood vessel characterization tasks, such as the calculation of the length, tortuosity, or caliber of the blood vessels. Yet, it is still unclear if pre-trained CNNs can provide robust, unbiased, results in downstream tasks involving the morphological analysis of blood vessels. Here, we focus on measuring the tortuosity of blood vessels and investigate to which extent CNNs may provide biased tortuosity values even after fine-tuning the network to a new dataset under study. Methods: We develop a procedure for quantifying the influence of CNN pre-training in downstream analyses involving the measurement of morphological properties of blood vessels. Using the methodology, we compare the performance of CNNs that were trained on images containing blood vessels having high tortuosity with CNNs that were trained on blood vessels with low tortuosity and fine-tuned on blood vessels with high tortuosity. The opposite situation is also investigated.Results: We show that the tortuosity values obtained by a CNN trained from scratch on a dataset may not agree with those obtained by a fine-tuned network that was pre-trained on a dataset having different tortuosity statistics. In addition, we show that improving the segmentation accuracy does not necessarily lead to better tortuosity estimation. To mitigate the aforementioned issues, we propose the application of data augmentation techniques even in situations where they do not improve segmentation performance. For instance, we found that the application of elastic transformations was enough to prevent an underestimation of 8% of blood vessel tortuosity when applying CNNs to different datasets.Conclusions: The results highlight the importance of developing new methodologies for training CNNs with the specific goal of reducing the error of morphological measurements, as opposed to the traditional approach of using segmentation accuracy as a proxy metric for performance evaluation.

Physicochemical analysis of the exhaust soot from a gasoline direct injection (GDI) engine and the carbon black

The purpose of the present study is to understand the physicochemical properties of the GDI soot and determine a GDI soot surrogate for the oxidation investigations. The high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analyzer were used to characterize the soot properties, including the morphology, nanostructure, chemical composition, carbon chemical state and oxidation reactivity. The GDI soot sample was harvested from the gasoline particulate filter equipped on a modern China VI passenger vehicle operated over the Worldwide harmonized Light-duty Test Cycle. The obtained GDI soot comprises large numbers of near-spherical primary particles that cluster together to form aggregates with a mean gyration radius of 123.79 nm, and the mean diameter of primary particles is 27.63 nm. The primary particle exhibits a typical core–shell structure, and the mean values of fringe length, separation distance and tortuosity are 0.836 nm, 0.362 nm and 1.263, respectively. In addition to the carbon element, the oxygen element is another important component of soot particles, accounting for 6.28% of the total number of atoms. The carbon component is mainly composed of sp2 hybridized graphitic carbon and sp3 hybridized aliphatic carbon, and the ratio of sp2/sp3 is 2.02. Moreover, the apparent activation energy of soot sample is determined to be 141.7 kJ/mol. The Special Black 4 (SB4) was assessed as a potential surrogate for the GDI soot. The comparison of physicochemical properties shows that the SB4 and GDI soot have almost the same fractal dimension, gyration radius, primary particle size, fringe length, separation distance, tortuosity, sp2/sp3 ratio and apparent activation energy. The great similarities in physicochemical properties highlight that the SB4 can serve as a good GDI soot surrogate for the soot oxidation investigations.

Tortuosity prediction and investigation of fluid flow behavior using pore flow approach in heap leaching

The aim of the current study is to use the pore flow approach in the hydrodynamic modeling of heap leaching. Also, by using this approach and presenting a novel method, the tortuosity of the porous media was predicted. For this purpose, a laboratory scale column with dimensions 20 cm × 20 cm × 45 cm containing copper oxide ore was prepared. Four sides of this ore box were photographed, vectorized and then numerical modeling of the fluid flow was implemented with the pore flow approach. Ore materials were from the first loading lift of a real copper mine, and the irrigation rate was equal to the operational rate of 10 L m−2 h−1 (2.77 × 10−6 m s−1). The average particle diameter was 1.8 cm and the voidage (inter-particle porosity) was about 20%. The modeling results show the velocity and pressure distribution in the media correspond to the pore flow approach. It strongly depends on the shapes of the ore particles and their arrangement. Correlation analysis of inter-particle porosity, velocity and pressure distribution confirm that the average velocity of the fluid is inversely related to the bulk voidage of the bed. Also, the pressure is a function of porosity and how the particles are placed next to each other. In the current research, a semi-empirical function is presented for tortuosity prediction in porous media by using a coupled numerical modeling and image processing approach. This equation predicts the average tortuosity value of the ore box around 1.445. Finally, the pore flow approach was implemented in a heap side wall and the seepage, pooling and fluid flow paths were predicted.

Estimation of Hydrogeological Parameters by Using Pumping, Laboratory Data, Surface Resistivity and Thiessen Technique in Lower Bari Doab (Indus Basin), Pakistan

Determination of hydrological properties of the aquifer is of fundamental importance in hydrogeological and geotechnical studies. An attempt has been made to refine the hydraulic conductivity values computed from the pumping test by utilizing the hydraulic values computed in the laboratory. This study uses hydraulic conductivity computed in the laboratory of rock samples, pumping test data in conjunction with the empirical equations, and vertical electric sounding (VES) to determine the hydraulic properties of Lower Bari Doab (LBD) in the Indus Basin of Pakistan. The utilized dataset comprises pumping test results (Kpump) from 17 water wells, hydraulic conductivity values (Klab) of different grain size subsurface lithologies, and 50 VES stations. To this end, the investigated area is divided into 17 polygons by using the Thiessen technique, and equal distribution/weight of conductivities values is assigned to 17 polygons (one polygon around each water well where pumping test is conducted). The true resistivity ranging from 20–90 ohm-m along with an average thickness of the aquifer is computed using the VES data for each polygon. A novel approach has been developed to estimate the hydraulic conductivity of the aquifer by combining laboratory data and pumping test which is used to compute the other hydraulic properties. The calculated hydraulic conductivity, transmissivity, and tortuosity values of the aquifer range from 4.4 to 85.6 m/day, 674 to 8986 m2/day, and 13 to 20, respectively. The porosity ranges from 32 to 45% and the formation factor values fall in the range 4 to 12. Higher hydraulic conductivities were encountered in the southern portion of the area near the junction of the rivers, and it increases with an increase in porosity. The aquifer having T &gt; 5700 m2/day and K &gt; 40 m/day, yields a large quantity of water whereas the portion of an aquifer with T &lt; 1100 m2/day and K &lt; 13 m/day are combatively low yield aquifer. The results of the resistivity method show that the subsurface geological material, as depicted from true resistivity, is composed of layers of sand, clay, and silt mixed with gravel/sand. This study improves the understanding of the aquifer and will help in the development and management of groundwater resources in the area including the prediction of future behavior of the aquifer.