Understanding and quantifying the flow process at fracture intersections is critical for the accurate modeling of field-scale discrete fracture networks (DFNs) but remains challenging. Particularly, ...the geometric features of the inflection points inside the intersection are usually ignored, limiting insight into the flow behavior at the intersection. To fill this knowledge gap, the effect of the inflection curvature at intersections was investigated based on direct numerical simulations by solving Navier-Stokes equations. The inflection points at the intersection were classified as α and β, corresponding to the radii of curvature
R
α
and
R
β,
respectively. The effect of
R
α
,
R
β
on flow redistribution and head loss was systematically analyzed and the sensitivity to flow nonlinearity was determined by the Morris method. The results demonstrated that the inflection curvature of the intersection has a significant effect on head loss but a negligible effect on flow redistribution. With the increase of curvature radius, the flow nonlinearity caused by inflection β enhances and that caused by α diminishes. Nonlinear flow is more sensitive to variations in
R
β
than
R
α
. The effect of intersection geometry diminishes with the decrease of hydraulic gradient or the increase of distance from the intersection. Further, the critical distance of the intersection’s interference range was assessed by considering different indicators. The results can provide a reference for parameter selection and calculation simplification in DFN modeling.
The drying of residue cyclohexane in a series of reconstituted gangue samples at ambient conditions was studied. The reconstituted gangue samples contained controlled amounts of residual bitumen, ...water, and fines (solid particles <45 μm). Regardless of the gangue composition, the initial drying flux was constant, and more than 90% of the residual cyclohexane was removed in this stage. The initial drying was driven by the liquid film flow induced by the differences in liquid film's radii of curvature along the pore channels. The liquid was a diluted bitumen solution that was transported to the surface, where cyclohexane evaporated with a rate comparable to that of pure cyclohexane evaporation. Upon the solvent evaporation, the dissolved bitumen was deposited on the sample surface. The residual bitumen content exerted an adverse effect on the initial drying flux because the dissolved bitumen significantly increased the solution viscosity, thereby reducing the liquid film flow rate. There existed an optimum water content range (3.9‐6.0 wt%) that facilitated the formation of bitumen solution film in the pores, favouring drying. When there was a high concentration of water or no water, the initial drying flux was decreased remarkably. The initial drying flux was insensitive to the fines content. Adding fines may have two counteracting effects on the drying process. Fines decreased the mean pore size, thereby lowering the liquid film flow rate. However, the hydrophobicity of the pore surfaces was increased as fines are usually covered by asphaltenes. This favours liquid film formation.
A paper-based electrode is a very attractive component for a disposable, nontoxic, and flexible biosensor. In particular, wearable biosensors, which have recently been attracting interest, not only ...require these characteristics of paper-based electrodes but must also be able to detect various ions and biomolecules in biological fluids. In this paper, we demonstrate the detection ability of paper-based metal electrodes for wearable biosensors as part of a wireless potentiometric measurement system, focusing on the detection of pH and sodium ions. The paper-based metal electrodes were obtained by simply coating a silicone-rubber-coated paper sheet with a Au (/Cr) thin film by sputtering then modifying it with different functional membranes such as an oxide membrane (Ta
2
O
5
) and a fluoropolysilicone (FPS)-based Na
+
-sensitive membrane, corresponding to the targeted ions. Satisfactory and stable detection sensitivities of the modified paper-based Au electrodes were obtained over several weeks even when they were bent to a radius of curvature in the range of 6.5 to 25 mm, assuming use in a flexible body patch biosensor. Moreover, the Na
+
concentration in a sweat sample was evaluated using the paper-based Au electrode with the FPS-based Na
+
-sensitive membrane in a wireless and real-time manner while the electrode was bent. Thus, owing to their complex mesh structure, flexible paper sheets should be suitable for use as potentiometric electrodes for wearable wireless biosensors.
Curved waveguides are an important wave guiding structure and have been widely used in building integrated photonics circuits with various functions including directional couplers, modulators, ring ...resonators, and Mach-Zehnder interferometers etc. However, curved structure always leads to attenuation of the guided mode as it propagates through the bend region. In practice the bending loss may be negligible if the radius of curvature is large, but the loss increases rapidly at small radii. Amongst curved waveguide structures the S-bend has been widely used, because it is relatively easy to design and can provide a low transition loss between parallel offset waveguides. In this paper we present a new general approach to S-bend optical waveguides by cascading multiple sections of uniformly curved waveguides. The aims are to offer maximize structure that can be used in more powerful beam propagation methods to estimate the loss in bends of continuously-varying curvature. We approach the S shaped bend waveguide by multiple sections such as 2, 6, 14 and 30 sections back to back and calculate the total loss. The convergence of resulting curvature variation are very rapid and the overall loss calculation found good agreement with analytical calculation based on low slope approximation.
The aim of this study was to compare the cyclic fatigue resistance of rotary NiTi files, produced with four different manufacturing methods on specially designed dynamic models that simulated ...clinical conditions. In this study, 120 files, consisting of 30 files for Typhoon, ProTaper Next, RaCe, and Twisted Files nickel titanium rotary systems were used. The 30 files of each group were divided into three subgroups to be used in artificial canals with a 60° angle of curvature and radii of curvature of 2, 5, and 8 mm (n = 10). All files were rotated in the artificial canals until fracture occurred and the number of cycles to fracture was calculated. The data were analyzed using one‐ and two‐way analyses of variance and Tamhane multiple comparison tests. In all three groups, Typhoon instruments had the highest number of cycles to failure than the RaCe, ProTaper Next, and Twisted Files instruments, and the difference statistically significant (p < .05). There were no significant differences between the RaCe, ProTaper Next, and Twisted Files groups (p > .05). The CM wire Typhoon system was significantly more resistant to cyclic fatigue compared to the other file systems in all three artificial canals. When the fracture resistance of an instrument in three different artificial canals was compared, the mean NCFs decreased as the radius of the curvature of the canal decreased from 8 to 2 mm. Manufacturing method is one of the most important factors on cyclic fatigue resistance, also the radius of curvature effects the cyclic fatigue.
Manufacturing method is one of the most important factors on cyclic fatigue resistance, also the radius of curvature effects the cyclic fatigue. As the radius of curvature decreases, cyclic fatigue resistance of NiTi files decrease and among the examined files the highest fatigue resistant file is CM Wire Typhoon System.
This paper reports the fabrication of subwavelength nano-structures on the curved surface of a glass lens for the purposes of anti-reflection. It utilizes a flexible PDMS mold to transfer metallic ...patterns to the lens surface which is pre-coated with a polymer layer. Using the transferred metal pattern as an etching mask, nano-structures are directly fabricated on the lens surface by plasma dry-etching processes. A plano/convex lens made of BK-7 glass with a lens diameter of 12.7 mm and a radius of curvature of 25.8 mm is used in this paper. Hexagonally arrayed nano-structures with a truncated conical profile, a center-to-center pitch of 300 nm, and a maximum structure height of 290 nm are experimentally achieved. Measurement results show the optical transmittance is increased by about 2.4% in average for wavelength within visible light spectrum. The directly fabricated nano-structures also exhibit good anti-glaring effects and the potentials for further optical applications.
Display omitted
•Fabrication nano-structures on convex lens using metal contact printing lithography.•Large-area nano-patterning method for axial-symmetric curved surface.•Experimental evidence of fabricating subwavelength structures using proposed lithographic method.•Simulation and experimental investigation on the enhanced transmittance by surface nano-structures.
During milling of free-form surfaces, cutting force varies due to the variation of workpiece surface curvature, which can seriously affect machining quality. In this study, a layered strategy was ...proposed for flexible machining of complex parts with variable curvatures. By taking a blade as the research object, we first considered a constant cutting force as the starting point. The relationship between the machining allowance and the radius of curvature of the workpiece under a certain cutting force was established. By analyzing the curvature of each position of the blade, a reasonable cutting allowance was set for each layer and the machining process was carried out layer by layer, such that a stable cutting force was maintained on the workpiece surface during machining of each layer. Second, the blade surface deformation law was determined by using the T-spline surface characteristics and an improved offset algorithm, and a series of deformation surfaces was obtained. Finally, the feasibility of the proposed method was verified by using finite element simulations and validated by experiment, and the advantages of the proposed method were verified by comparison with the existing main blade processing methods.
Background:
Conventional osteochondral allograft (OCA) matching, requiring orthotopic, size-matched condyles, and narrow surgical time windows often prohibit timely transplantation.
Hypothesis:
The ...femoral condyle radius of curvature (RoC) is an appropriate, isolated criterion for donor-host matching in fresh OCAs, potentially enhancing matching efficiency when compared with conventional matching techniques.
Study Design:
Descriptive laboratory study.
Methods:
In part 1 of this study, 3-dimensional digital reconstructions of 14 randomly selected, cadaveric distal femoral hemicondyles were performed. Each condyle was divided into anterior, middle, and posterior zones. A virtual best-fit grid was applied to each, and each zone’s sagittal- and coronal-plane RoCs were determined. Seven nonorthotopic OCA transplantations were performed based on RoC matching with 1-mm tolerance, and the preoperative and postoperative surface geometry were quantified to assess the accuracy of articular surface restoration. Of note, each donor-host pair did not match by the conventional method. In part 2 of this study, 12 cadaveric distal femora were categorized by size and digitized in the aforementioned manner. Simulated circular defects measuring 20, 25, and 30 mm in diameter were introduced into each zone. OCA matches were determined based on donor and host RoCs, and the total number of potential matches (of 71 total comparisons) was recorded as a percentage for each simulated defect. Finally, the results of RoC matching were compared with the conventional method for simulated defects in all zones of both the medial and lateral femoral condyles.
Results:
Part 1: The mean surface deviation after OCA transplantation was −0.09 mm, with a mean maximum protrusion at any point of 0.59 mm. Part 2: Using the RoC, 20-mm defects had a 100% chance of being matched. Defects of 25 and 30 mm had a 91% and 64% chance of being matched, respectively. Compared with the conventional method, the RoC method yielded a 3.2-fold greater match rate for lesions of the medial and lateral femoral condyles (P = .02).
Conclusion:
This investigation shows that femoral condyle RoCs in the sagittal and coronal planes may be useful, alternative matching criteria, expanding on current standards.
Clinical Relevance:
These matching criteria may increase the number of available matches, reduce wait times for patients, and reduce the number of wasted grafts.
Chip is an important index to reflect the quality of machining, and its geometric characteristics such as chip sawtooth degree, sawtooth frequency and radius of curvature are greatly affected by ...cutting parameters. In order to study and predict the evolution of serrated chip in micro-milling of titanium alloy, finite element analysis software ABAQUS was used to establish the finite element model. Based on elasto-plastic constitutive model, fracture criterion and friction model, the influences of linear velocity and feed per tooth on chip morphology and cutting force were simulated. The relationship between serrated chip formation and cutting force fluctuation is revealed, so as to further explore the chip formation mechanism.
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