Equivalent Circle Research Articles

Texture development during multi-step cross rolling of a β titanium alloy: Experiments and simulations

In the present work, microstructure and texture evolution during multi-step cross rolling of a β-Ti alloy was investigated. The as-received samples were cross rolled in a laboratory rolling mill to 20%, 40%, 60% and 80% thickness reduction. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the changes in microstructure, while the changes in bulk texture were evaluated using X-ray diffraction. The as-received sample consisted of equiaxed as well as elongated grains. Equivalent circle average grain size (AGS) and the average band thickness (ABT) along normal direction (ND) for as-received β-Ti sample was 50 ± 3 μm and 27 ± 1.8 μm respectively. The AGS and ABT decreased with increase in cold rolling reduction (for 80% cold rolled sample ABT was 7.5 ± 2.3 μm). Another important feature was the presence of strain localizations in the cold rolled samples, the frequency of which increased with increase in strain. The as-received sample showed the presence of α (rolling direction RD//<110>) and γ (ND//<111>) fibers. At highest strain (80% cold rolling), rotated cube ({100}<110>) component was found to be significantly stronger than the γ-fiber texture. Visco-Plastic Self Consistent (VPSC) model was used for the simulation of texture during cold cross rolling. Qualitatively, full constraint VPSC model was found to match reasonably well with the experimental data. α-Fiber, γ-fiber and rotated cube were over estimated in the VPSC texture predictions.

Attribute Profiles of Different Attributes for Spectral-Spatial Classification of Hyperspectral Imagery

Incorporation of spatial information along with spectral features has a great impact on the analysis of hyperspectral images (HSIs). Attribute profiles have been proved to be a very effective state-of-the-art method for fusing spectral and spatial information in HSI. This paper recalls the construction of attribute profiles (APs) for HSI classification and provides a comprehensive analysis of different properties of connected components that can be used as an attribute while constructing APs. Various attributes have been widely and successfully used to construct attribute profiles for spectral-spatial classification of HSIs. In this paper, we investigate several unexplored attributes in addition to the existing ones. An empirical study on the attribute profiles, constructed by using different attributes, is carried out considering three real HSI data sets. Our study reveals that each attribute possesses interesting filtering capabilities among which the attributes namely complexity and diameter of equivalent circle, which are new in the HSI literature, are found most promising to incorporate spatial information for HSI classification. The paper also lists out suitable attributes for recognition of different classes in a remote sensing scene.

A transient contact position prediction method for worn tooth profile under dry running conditions

PurposeThe purpose of this paper is to establish a transient contact position prediction method of gears at the meshing point based on the equivalent contact model.Design/methodology/approachIn this method, the contacting surface profiles are constantly updated by changing the pressure angle and the chord tooth thickness, which has a direct connection with the equivalent base circle radius. According to the equivalent base circle radius, the equivalent pressure angle at the pitch circle and equivalent pitch point can be calculated. The equivalent contacting surface profile is determined by the equivalent pressure angle at the pitch circle; for each meshing point, there is one equivalent pressure angle at the pitch circle. Therefore, each meshing point can be regarded as a point on the equivalent contacting surface profile.FindingsThe model is applicable to find out the contact position after a series of meshing cycles through the law of pressure angle change and intentionally kept as simple as possible with the aim to be used in further study of gear flanks at the point of the actual contact.Practical implicationsThe results of the experiment are applied to the equivalent contact model to describe the transient contact position and assess the model accuracy.Originality/valueThe determination of the contact position of the worn tooth profile provides the action points of the force for the study of the contact fatigue.

Structural analysis of porous bioactive glass scaffolds using micro-computed tomographic images

Three-dimensional structural properties such as pore size, interconnectivity, and tortuosity of scaffold play an essential role in bone tissue regeneration. We report the structural characterization of bioactive glass-based scaffolds by employing micro-computed tomography (µCT) imaging. µCT images were filtered and binarized to get 3D reconstruction of the scaffold. Fast march method was applied on 3D reconstructed scaffold to estimate tortuosity. Further, Canny edge detection algorithm was used to identify pore boundaries. Graph traversal algorithm was used to identify pore networks as open, close, and through. Pore and minimum throat size for a through path were quantified using equivalent circle diameter based on ASTM F2603-06. The porosity (66.69%), mean pore size (443 µm), mean pore throat diameter (131 µm), and tortuosity in different planes (~ 1) imply suitability of the scaffold for bone tissue engineering. Any porous sample can be characterized by the methodology directly with µCT or other imaging techniques.

Computer Simulation of Nonlinear Distortion of Class D Sound Amplifier on GaN-Transistors

Class A, B, AB and D amplifiers are used in the field of sound reproduction equipment, but each has its own peculiarities. The principle of operation of class D amplifiers is based on pulse width modulation. Transistors act as switches, either in the closed or opened state without intermediate values. The efficiency of real class D amplifiers is approximately 90%, in the most economical models 95%, and they have low dependence of the output power. The class D amplifiers are compact in size. For this paper, GaN-transistors were selected as the base. Because they are, compared to silicon transistors, low resistance in the open state, high breakdown voltage, higher switching speed of the transistors. They also work at high temperatures.The nonlinear distortions is negative features of Class D amplifiers. They directly affect the sound quality. The distortions include nonlinearity, which is determined by the modulation method and the "dead" period, which is necessary to prevent the occurrence of cross-current at the moment when both half-transistors are open. Modeling the parameters of a Class D amplifier, especially at an early stage of development, is a necessary tool that can significantly reduce the time and money spent on development and production. In this paper, simulations were performed using equivalent circle methods.Changing the shape of the signal at the output of the cascade is called nonlinear distortion. They affect the output signal formation positively (e.g. in demodulation) and negatively (e.g. in amplifiers). When investigating GaN transistors on Class D amplifiers, the signal shape at the amplifier output will be different from the signal shape at the input nonlinear distortions occur. They are due to the features of the structure of the amplifier.The purpose of this work is to create a model of the output stage of a class D amplifier on GaN transistors so as to be able to investigate the effect of nonlinear distortions when changing the switching frequency for different signal frequencies.The GaN transistor EPC2022 transistor based on GaN transducer, which is assembled on the EPC9035 board for researching, it was selected as the basis for the amplifier model.The simulation was performed in the Multisim 14.1 software environment. The dependence of the occurrence of nonlinear distortions for switching frequencies of 100 kHz, 250 kHz, 500 kHz, 1000 kHz for sound signals of 1 kHz, 2 kHz, 5 kHz and 10 kHz is investigated. The study founds that nonlinear distortions for different conversion frequencies have different frequency dependencies. For the studied conversion frequencies, there is a decrease in the distortion with increasing frequency, which is caused by the decrease of the high-frequency harmonics of the output filter.The optimal working conditions for obtaining the minimum values of the coefficient of nonlinear distortions are determined. It is investigated that the created model proves the efficiency of using class D amplifiers on GaN transistors for audio paths. Because it allows to obtain a coefficient of nonlinear distortion of up to 1% and high efficiency.

Characterization of the Microstructure and Precipitates Formed During the Thermomechanical Processing of a CrNiMoWMnV Ultrahigh‐Strength Steel

The effect of total applied strain (TAS), finish forging temperature (FFT) on the microstructure, and precipitation kinetics of a newly developed low‐cost, low‐alloy CrNiMoWMnV ultrahigh‐strength steel has been investigated. A Gleeble 3800 thermomechanical simulator is used to simulate the hot forging process and its influence on the precipitation kinetics. Field‐emission scanning electron microscopy combined with electron‐backscattered diffraction is used to characterize the final overall microstructures, whereas transmission electron microscopy on carbon extraction replicas is used to characterize the precipitates in terms of morphology, size distribution, mean equivalent circle diameter, the 90th percentile in the cumulative diameter distribution (D90%ppt), chemical composition, and crystallography. Thermo‐Calc software is used to predict the precipitates expected in austenite at equilibrium. The final microstructure consists of lath martensite and a small fraction of the precipitates AlN, TiN, and composite TiN–AlN. Differences in the degree of strain‐induced precipitation caused by variations in TAS and FFT have been shown to greatly influence precipitate size distributions. Variations in the degree of precipitate dissolution and coarsening cause variations in the prior austenite grain size, which subsequently cause variations in the effective grain size of the final microstructure, i.e., that are defined by high‐angle grain boundaries.

Influence of Tempering Time on the Behavior of Large Carbides’ Coarsening in AISI H13 Steel

The mechanical properties, microstructures and precipitation behaviors in AISI (American Iron and Steel Institute) H13 steel tempered at 863 K for 0.5, 2, 4, 10 and 20 h were investigated. The values for H13 tempered for 2–4 h resulted in die steel that reached the desired properties as specified in NADCA (North American Die Casting Association) #207-2016. The cubic Ostwald ripening model was applied to simulate the coarsening of the large carbides, which were mainly M23C6 and M3C, as determined from FactSage predictions as well as measurements with transmission electron microscopy (TEM). TEM revealed that the equivalent circle radius (ECR) decreased during 0.5–2 h, because of the nucleation of many new precipitates. According to the Ashby-Orowan modified precipitation strengthening model, this decrease in ECR leads to an increase in the contribution of precipitates to yield strength. Between 2 and 4 h tempering, the ECR of large carbides increases sharply but then increases asymptotically from 4 to 20 h, which obeys the calculated Ostwald ripening rate for cementite and M23C6 in H13 after 863 K tempering. This observation for the Ostwald ripening of M23C6 is in agreement with experimental data for other steels in the literature.

Load Distribution in Meshing Process of Micro-segment Gears

In this paper, a precise transverse micro-segment tooth profile is established. Subsequently, a load distribution model of micro-segment gears is proposed based on the method of elastic potential energy. A method for choosing an equivalent base circle is proposed to accurately calculate the tooth force of each tooth pair of spur micro-segment gears. Similar to spur gears, a torque distribution method is also established for helical micro-segment gears. Based on the simulation analysis of different basic micro-segment parameters, their significant influence on the load distribution is presented. In addition, it is found that during an entire contact period, the maximal tooth force of a micro-segment gear pair is smaller than that of an involute gear pair. The model is also validated by the finite element method. This model provides a rapid and effective approach to determine the load for the subsequent analysis of the contact and bending strengths of micro-segment gears.

Prediction of Inclusion State in Molten Steel by Morphology and Appearance of Inclusions in Liquid Steel Samples

Inclusions are unwanted but to some extent inevitable in molten and solid steel. Usually solid inclusions are considered to be the most harmful. Inclusions can be converted into a less detrimental form with calcium treatment. The success of calcium treatment can be evaluated by analyzing the state of the inclusion population. The state of inclusions is usually determined by computational thermodynamics making use of the chemical composition of inclusions and system conditions. In this process, liquid and solid inclusions are usually distinguished. Herein, a classification procedure which combines computational thermodynamics and data‐driven reasoning is presented. The objective of this work is to study the predictability of the inclusion state based on its appearance and morphological properties. As a result, Al2O3–CaO–MgO–CaS inclusions are classified as liquid and solid ones based on their aspect ratio, equivalent circle diameter, and mean gray value with a recall of 82.7% and precision of 84.9%, by making use of a logistic regression‐based classifier.

Lychee Fruit Detection Based on Monocular Machine Vision in Orchard Environment.

Due to the change of illumination environment and overlapping conditions caused by the neighboring fruits and other background objects, the simple application of the traditional machine vision method limits the detection accuracy of lychee fruits in natural orchard environments. Therefore, this research presented a detection method based on monocular machine vision to detect lychee fruits growing in overlapped conditions. Specifically, a combination of contrast limited adaptive histogram equalization (CLAHE), red/blue chromatic mapping, Otsu thresholding and morphology operations were adopted to segment the foreground regions of the lychees. A stepwise method was proposed for extracting individual lychee fruit from the lychee foreground region. The first step in this process was based on the relative position relation of the Hough circle and an equivalent area circle (equal to the area of the potential lychee foreground region) and was designed to distinguish lychee fruits growing in isolated or overlapped states. Then, a process based on the three-point definite circle theorem was performed to extract individual lychee fruits from the foreground regions of overlapped lychee fruit clusters. Finally, to enhance the robustness of the detection method, a local binary pattern support vector machine (LBP-SVM) was adopted to filter out the false positive detections generated by background chaff interferences. The performance of the presented method was evaluated using 485 images captured in a natural lychee orchard in Conghua (Area), Guangzhou. The detection results showed that the recall rate was 86.66%, the precision rate was greater than 87% and the F1-score was 87.07%.

Evaluation of coal component liberation upon impact breakage by MLA

To elucidate the coal component liberation mechanisms upon typical impact breakage, the coal was selected from the Shangwan mine in China. Thereafter, mineral liberation analysis was adopted as the main method for investigating phase interface characteristics, classification characteristics of the various classes of comminuted products, and changes in the mineral area and length gradients upon mechanical impact breakage. The results indicate that the grain sizes of the comminuted products decreased in the following order: slag product >classifier product >bag product. Moreover, the disseminated grain size, dissemination mode, and original cleavages had a direct influence on the recovery rate of the completely liberated phase. The coal, which formed the main component of the samples, exhibited the highest cumulative mass recovery (CMR) in classified products and was most easily liberated. Furthermore, the kaolinite-bearing coal and pyrite were moderately liberated, the quartz and kaolinite were difficult to liberate, and the illite was extremely difficult to liberate. Under mechanical impact breakage, intragranular and intergranular fractures mainly occurred in particles, with the changes in the mineral boundary and mineral area corresponding to varying fracture modes. To a certain extent, the particle comminution could be quantified by the changes in the slope of the equivalent circle diameter–-CMR curve. It was determined that the main cause of the increased liberation degree is the generation of the completely liberated phase of the component of interest. Furthermore, by adopting the liberation factor for quantification of the mineral liberation, the calculation model for coal component liberation was obtained.

Hierarchical Management Control Based on Equivalent Fitting Circle and Equivalent Energy Consumption Method for Multiple Fuel Cells Hybrid Power System

In order to reduce the operating cost of hydrogen fuel cell hybrid electric tram, this paper proposes a hierarchical control method, which includes a control layer and a management layer. In the control layer, through three-dimensional efficiency, modeling, and geometric solution of fuel cell system (FCS), the equivalent fitting circle method is adopted to realize the optimal allocation among sets of multiple fuel cells with different parameters. Meanwhile, in management layer, according to the operation states of tram, the supercapacitor dynamic energy consumption coefficient is proposed and applies in the tram efficiency model for the equivalent energy consumption (EEC) method, and the improved EEC method can accurately provide the optimal power distribution of the hybrid system under different operating conditions. According to RT-LAB platform tests, compared with other online methods under the same operating conditions, the proposed method has the apparent satisfactory results in reducing hydrogen consumption. What is more, the actual tram operation test also shows that the proposed method ensures the output stability of the FCS so as to prolong its life and reduce its operation and maintenance costs.

Particle analysis of shape factors according to American Society for Testing and Materials.

Polyethylene wear is one of the major factors influencing the survivorship of joint replacements. Depending on the number, size and morphology of the polyethylene particles, biological responses of the periprosthetic soft tissue in terms of inflammatory processes can occur, leading to loosening of the implant. Various parameters are used to analyze wear particles, which are usually determined by examining scanning electron microscopy (SEM) images with a particle analysis program. In this study, three different software solutions for particle analysis (self-developed Particleanalyzer_HD, Leica QWin and ImageJ) were compared regarding particle number, size and morphology. These solutions were also compared to the American Society for Testing and Materials (ASTM) F1877-16 specifications regarding particle morphology. SEM image analysis revealed no differences for the equivalent circle diameter (p = 0.969). However, a significant difference was found for the aspect ratio between the Particleanalyzer_HD and the other two software solutions (p < 0.001) and between Leica QWin and the other two software solutions regarding the roundness (p < 0.001). Only the Particleanalyzer_HD showed an excellent agreement with the ASTM standard for both morphology parameters (intraclass correlation = 1.000). Only the Particleanalyzer_HD calculated the two morphology parameters according to the ASTM standard. A comparison of the particle morphology between different studies is barely possible, as different algorithms for particle analysis are used. It is strongly recommended that the calculation according to the ASTM standard is used to improve future comparability of findings from wear analysis studies. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:225-233, 2020.

Comparative Investigations on Internal Force Distribution Characteristics on Concrete Segments in Qiongzhou Strait Sub-Sea Tunnel

In the design of shield tunnel concrete segments, the calculation of internal forces on segment sections is an important part. In order to study the influence of combining calculation of water and soil pressure and separate calculation of water and soil pressure towards internal forces on segment sections, taking the Qiongzhou Strait sub-sea tunnel as the background, ANSYS software is used to establish the equivalent stiffness circle model, hinged model and beam spring model, and the internal forces on segment are calculated by two methods of combining calculation of water and soil pressure and separate calculation of water and soil pressure. The results show that the difference of the bending moment between the two methods is great while the difference of the axial force is small, the maximum bending moment of combining calculation of water and soil pressure is 2.2∼2.9 times larger than that of separate calculation of water and soil pressure, and the axial force is 11%∼16% larger than separate calculation of water and soil pressure.

Numerical calculation of the loss resistance of VLF monopole antennas using the equivalent conductivity of the ground plane

In this study, the ground-loss resistances of very low frequency (VLF) monopole antennas are considered. A novel method of obtaining solutions of the magnetic field and electric field losses for the earth system is outlined. The equivalent conductivity of the ground system is obtained using the parallel relationship between the nature surface and the ground wires. This provides significant convenience for the calculation of the ground loss and the design of the ground system. Because an equivalent ground plane is used, a unique solution of the ground loss resistances is achieved by using the integral of the equivalent unit circles. The proposed method is verified by comparing the numerical integral method and full-wave simulations. The numerical results and the effects of the VLF monopole antenna configurations on the loss resistances for different monopole heights and artificial-ground-plane installations are discussed.

The effect of electroslag remelting on the cleanliness of CrNiMoWMnV ultrahigh-strength steels

The cleanliness of ultrahigh-strength steels (UHSSs) without and with electroslag remelting (ESR) using a slag with the composition of 70% CaF2, 15% Al2O3, and 15% CaO was studied. Three experimental heats of UHSSs with different chemical compositions were designed, melted in an induction furnace, and refined using ESR. Cast ingots were forged at temperatures between 1100 and 950?C, air cooled, and their non-metallic inclusions (NMIs) were characterized using field emission scanning electron microscopy and laser scanning confocal microscopy. Thermodynamic calculations for the expected NMIs formed in the investigated steels with and without ESR were performed using FactSage 7.2 software while HSC Chemistry version 9.6.1 was used to calculate the standard Gibbs free energies (?G?). As a result of ESR the total impurity levels (TIL% = O% + N% + S%) and NMI contents decreased by as much as 46 % and 62 %, respectively. The NMIs were classified into four major classes: oxides, sulphides, nitrides, and complex multiphase inclusions. ESR brings about large changes in the area percentages, number densities, maximum equivalent circle diameters, and the chemical composition of the various NMIs. Most MnS inclusions were removed although some were re-precipitated on oxide or nitride inclusions leading to multiphase inclusions with an oxide or nitride core surrounded by sulphide, e.g. (MnS.Al2O3) and (MnS. TiN). Also, some sulphides are modified by Ca forming (CaMn)S and CaS.Al2O3. Some nitrides like TiN and (TiV)N are nucleated and precipitated during the solidification phase. Al2O3 inclusions were formed as a result of the addition of Al as a deoxidant to the ESR slag to prevent penetration of oxygen to the molten steel.

Effects of Illumination-Dependent Pupil Size on Higher Order Aberration

Purpose : We investigated the effect of illumination-dependent pupil size on higher order aberration. Methods : Thirty five patients (mean age, 22.5 ± 1.04 years) who had no ocular or systemic disease and had no other relevant surgical experience were selected, and we measured aberration. Due to the property of i.Profiler plus instrument, it is assumed that the pupil size ʻ3 mmʼ under photopic vision is similar to photopic vision environment and pupil size ʻmaximumʼ under semidark room is similar to mesopic vision environment. Correlation analysis between pupil size and equivalent defocus and equivalent blur circle was performed. Results : RMS values were 0.30±0.13 ㎛ and 0.38±0.15 ㎛ when the pupil size was divided into 3 mm and maximum. The equivalent defocus of total high order aberration was 0.28±0.14 D at the pupil size of 3 mm and 0.41±0.16 D at the maximum, which are significant differences(p=0.000). The difference of equivalent defocus of spherical aberration, coma aberration, and trefoil aberration was 0.07 D, 0.04 D, and 0.02 D at 3 mm and maximum, respectively, and there were significant differences in the spherical(p=0.000) and coma aberration(p=0.000)). There were significant positive correlations between equivalent defocus and equivalent blur circle(total higher order aberrations (R2=0.7045, p < 0.01), spherical aberration(R2=0.9376, p < 0.01), coma aberration(R2=0.8429, p < 0.01) and, trefoil aberration(R2=0.7824, p < 0.01)). Conclusions : The result of the aberration measurement is expressed as equivalent defocus, so that the degree of required correction can be expressed as diopter. Unless the correction of high order aberrations is considered, it is valuable to study the visual discomfort of high order aberrations as there would be a change in the corrected visual acuity.

Note on the use of different approaches to determine the pore sizes of tissue engineering scaffolds: what do we measure?

BackgroundCollagen-based scaffolds provide a promising option for the treatment of bone defects. One of the key parameters of such scaffolds consists of porosity, including pore size. However, to date, no agreement has been found with respect to the methodology for pore size evaluation. Since the determination of the exact pore size value is not possible, the comparison of the various methods applied is complicated. Hence, this study focuses on the comparison of two widely-used methods for the characterization of porosity—scanning electron microscopy (SEM) and micro-computed tomography (micro-CT).Methods7 types of collagen-based composite scaffold models were prepared by means of lyophilization and collagen cross-linking. Micro-CT analysis was performed in 3D and in 2D (pore size parameters were: major diameter, mean thickness, biggest inner circle diameter and area-equivalent circle diameter). Afterwards, pore sizes were analyzed in the same specimens by an image analysis of SEM microphotographs. The results were statistically evaluated. The comparison of the various approaches to the evaluation of pore size was based on coefficients of variance and the semi-quantitative assessment of selected qualities (e.g. the potential for direct 3D analysis, whole specimen analysis, non-destructivity).ResultsThe pore size values differed significantly with respect to the parameters applied. Median values of pore size values were ranging from 20 to 490 µm. The SEM values were approximately 3 times higher than micro-CT 3D values for each specimen. The Mean thickness was the most advantageous micro-CT 2D approach. Coefficient of variance revealed no differences among pore size parameters (except major diameter). The semi-quantitative comparison approach presented pore size parameters in descending order with regard to the advantages thereof as follows: (1) micro-CT 3D, (2) mean thickness and SEM, (3) biggest inner circle diameter, major diameter and area equivalent circle diameter.ConclusionThe results indicated that micro-CT 3D evaluation provides the most beneficial overall approach. Micro-CT 2D analysis (mean thickness) is advantageous in terms of its time efficacy. SEM is still considered as gold standard for its widespread use and high resolution. However, exact comparison of pore size analysis in scaffold materials remains a challenge.

Microstructural analysis of undoped and moderately Sc-doped TiO2 anatase nanoparticles using Scherrer equation and Debye function analysis

UV light sensitive undoped and moderate (4 at.%) Sc-doped anatase nanocrystallites were prepared by an efficient and environmentally benign method based on homogeneous hydrolysis of TiOSO4 and Sc2(C2O4)3.5H2O aqueous solutions using urea as a precipitation agent, without post-synthesis calcination or annealing.X-ray diffraction study of the obtained powders revealed single phase anatase in both samples. Two different methods were applied to estimate the anatase crystallite size and shape from the X-ray diffraction data. The first one is based on the more conventional Scherrer equation (as implanted in GSAS-II program) while the second one is based on Debye function analysis (as implanted in DUBUSSY suite version 2.2), which is considered to be more adequate for nanocrystallites. Although each program has its own shape models, both methods indicated similar results of elongated nanocrystallite geometry for Sc-doped TiO2: (i) GSAS-II confirmed ellipsoid shape with equatorial size of 5.1(0) nm and axial size of 6.8(0), (ii) DEBUSSY suite 2.2 showed cylinder shape with diameter of equivalent circle in the ab-plane, Dab = 4.9(1.0) nm and crystallite length along the c-axis, Lc = 5.4(3.2) nm. For the undoped TiO2 sample, equatorial size of 5.5(0) nm and axial size of 7.3(0) nm for the ellipsoid shape was determined according to GSAS-II, while Dab = 5.5(1.3) nm and Lc = 6.0(2.2) nm for the cylinder shape was determined by DEBUSSY suite 2.2. These outcomes were found to corroborate with HRTEM analysis.Doping with 4 at.% Sc caused ~0.3% growth of lattice parameters from a = 3.7979 [4] Å, c = 9.4995 [9] Å for the undoped sample to a = 3.8110 [7] Å, c = 9.5274 [16] Å for the moderately Sc doped sample, while reduction in the Ti vacancies by half was confirmed by both methods.The introducing of Sc as electronically active secondary species into the crystal lattice of TiO2 can greatly alter its optical absorption. The incorporation of Sc into the crystal lattice of TiO2 favors the substitution of Ti, as both have approximately the same ionic size, and generates surface oxygen vacancies which can act as trapping center for the photogenerated electrons and reduce the recombination of electron–hole pairs. We can expect Sc doped TiO2 nanomaterials to have applications as effective photocatalysts for selective photocatalytic oxidation of various environmental organic pollutants.

Conventional Ultra-high Molecular Weight Polyethylene versus Highly Cross-linked Polyethylene from Semi-constrained, Fixed-bearing Total Ankle Arthroplasty Systems

Category: Ankle Arthritis Introduction/Purpose: The aim of this study was to compare the polyethylene wear rate, particle size, and particle shape of primary semi-constrained, fixed-bearing, bone-sparing total ankle arthroplasty using conventional ultra-high molecular weight polyethylene (CPE) versus highly cross-linked polyethylene (HXLPE) by applying a level walking input using a joint simulator. Methods: Two fixed-bearing total ankle replacement systems with different types of polyethylene liners were tested: 1.) CPE sterilized in ethylene oxide, and 2.) HXLPE sterilized with gas plasma after electron beam irradiation. Three implants for each design underwent wear testing using gravimetric analysis over 5 million simulated walking cycles. A fourth implant was used as a load soak control. Equivalent circle diameter (ECD) and equivalent shape ratio (ESR) were computed to determine particle size and particle shape, respectively. Results: The mean wear rate from 1.5-5 million cycles (MC) was 2.0±0.3mg/MC for HXLPE and 16.7±1.3mg/MC for CPE (P &lt; 0.001). The total number of particles per cycle generated for HXLPE and CPE were 0.17x106 particles/cycle and 0.53x106 particles/cycle, respectively (P &lt; 0.001). The mean ECD of HXLPE particles (0.22 ±0.11μm) was significantly smaller than the mean ECD of CPE particles (0.32±0.14μm) (P&lt;0.001). HXLPE particles were significantly more round than CPE particles (P&lt;0.001). Conclusion: HXLPE liners had a significantly lower wear rate and produced significantly fewer and rounder particles than CPE liners. The results of this study suggest that HXLPE has more favorable wear characteristics for total ankle arthroplasty.