Average Diagonal Length Research Articles

Fracture toughness and hardness of in-office, 3D-printed ceramic brackets.

Three-dimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of in-office, 3D printed ceramic brackets. 3D-printed zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3 M St. Paul, MN) and 3D-printed customized polycrystalline alumina ceramic ones (LightForce™, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α= .05. Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3D-printed zirconia proved to be less hard (1261 ± 39 vs 2000 ± 49 vs 1840 ± 38) but more resistant to crack propagation (K1c=6.62 ± 0.61 vs 5.30 ± 0.48 vs 4.44 ± 0.30 MPa m1/2 ) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent. Under the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters.

A solution-processed octahedral nano-blocks structure CaIn2S4 film for UV/vis photodetection

A novel CaIn2S4 with three-dimensional octahedral nano-blocks (ONBs) are successfully synthesized on fluorine-doped tin oxide (FTO) substrate by a simple hydrothermal method. The CaIn2S4 ONBs are uniform grown and scattered on the whole FTO substrate with high regular and symmetric morphology as well as average diagonal length of about 600 nm. Based on the as-synthesized CaIn2S4 ONBs, a photodetector (PD) is fabricated. Satisfyingly, it is found that the CaIn2S4 ONBs PD achieves a broad-band response ranging from ultraviolet (UV) to visible ( vis) light at zero bias voltage. It is also significant that the CaIn2S4 ONBs PD enables a fast response, in which the rise time and decay time are less than 0.15 and 0.2 s, respectively. Furthermore, the morphological evolution of the CaIn2S4 ONBs and plausible UV/vis detection mechanism of the CaIn2S4 ONBs PD are discussed.

Reliability of Recurrence Quantification Analysis Measures for Sit-to-Stand and Stand-to-Sit Activities in Healthy Older Adults Using Wearable Sensors

Standing up and sitting down are prerequisite motions in most activities of daily living scenarios. The ability to sit down in and stand up from a chair or a bed depreciates and becomes a complex task with increasing age. Hence, research on the analysis and recognition of these two activities can help in the design of algorithms for assistive devices. In this work, we propose a reliability analysis for testing the internal consistency of nonlinear recurrence features for sit-to-stand (Si2St) and stand-to-sit (St2Si) activities for motion acceleration data collected by a wearable sensing device for 14 healthy older subjects in the age range of 78 ± 4.9 years. Four recurrence features—%recurrence rate, %determinism, entropy, and average diagonal length—were calculated by using recurrence plots for both activities. A detailed relative and absolute reliability statistical analysis based on Cronbach’s correlation coefficient (α) and standard error of measurement was performed for all recurrence measures. Correlation values as high as α = 0.68 (%determinism) and α = 0.72 (entropy) in the case of Si2St and α = 0.64 (%determinism) and α = 0.69 (entropy) in the case of St2Si—with low standard error in the measurements—show the reliability of %determinism and entropy for repeated acceleration measurements for the characterization of both the St2Si and Si2St activities in the case of healthy older adults.

An Investigation of Ultrasonic-Assisted Electrochemical Machining of Micro-Hole Array

This paper uses an ultrasonic vibration-integrated array electrode for 301 stainless steel micro-hole drilling. The influence of machining parameters such as ultrasonic vibration amplitude, working voltage, pulse-off time and electrode feed rate on different processing characteristics are discussed. The experimental results show that the ultrasonic-assisted electrode array vibrating generates a periodic pressure difference for the electrolyte. The periodic pressure difference forms a pumping effect and a cavitation effect. The two effects can effectively renew the electrolyte in the machining gap and discharge the reaction product, gas and reaction heat from the gap. Machining speed can be increased by over 500% when the ultrasonic amplitude increases from 0.94 μm to 2.87 μm. Micro-hole drilling with the optimum experimental parameter combination of ultrasonic amplitude 2.87 μm, working voltage 11 V, pulse-off time 50 μs and electrode feed rate 5 μm/s can result in a minimum average diagonal length and a smaller amount of variation in diagonal length. It also improves the inlet and outlet taper angle of micro-holes.

Effect of axis ratio on unsteady wake of surface mounted elliptic cylinder immersed in shear flow

Three-dimensional flow past surface mounted elliptic cylinder has been investigated numerically using OpenFOAM. Axis ratio (AR) of the elliptic cylinder is varied from 0.5 to 2. Effects of shear intensity (K) of the nonuniform incoming flow and Reynolds number (Re) varying from 150 to 250 on wake dynamics have been examined using Hilbert Huang transformation and Recurrence analysis. Qualitative and quantitative analyses of wake unsteadiness are illustrated using Hilbert spectra and degree of stationarity. Various recurrence quantification estimates have been reported to reveal insight about unsteady wake transition with the change in Re, AR and K. Four types of distinguishable wake flows, viz., steady, periodic, quasi-periodic and chaotic have been characterized with the help of vorticity contours, frequency spectra and bifurcation diagram. In aperiodic flow, wake oscillation contains multiple laminar states or slow changing states which has been disclosed using laminarity and trapping time. Nonstationarity and synchronous wake behavior along the height of the cylinder have been examined using cross-recurrence analysis and quantified in terms of recurrence rate, determinism and average diagonal length. In addition, the effect of change in K for each value of Re and AR has been studied on the mean drag coefficient of the cylinder.

Correlation Between Friction Coefficient and Friction Vibration in Running-In Process Based on Cross Recurrence Plots

Abstract The friction coefficient is difficult to measure in a real application, whether friction coefficient and vibration signals have the same dynamic characteristics is an urgent issue to be solved. The running-in friction tests were carried out under dry friction, starved, and flooded lubrications. Cross recurrence plots (CRPs) and their measures were used to explore the correlation between friction signals. The results show that the more obvious the diagonal structures in CRPs, the better the correlation between the two signals. The measures from different friction systems are smaller than those from the same system. Average diagonal length is more sensitive to characterize the correlation. Irrespective of lubrication conditions, friction coefficient and vibration in the same friction system have a strong correlation. The correlation under boundary lubrication is the strongest, followed by oil-rich and dry friction. Thus, friction coefficient or vibration can be selected according to the convenience of measurement to monitor the running-in process.

DYNAMIC IDENTIFICATION OF WEAR STATE BASED ON NONLINEAR PARAMETERS

This paper presents a new methodology of wear state recognition by using fractal parameters, multifractal parameters and recurrence parameters. The relationship between these nonlinear parameters is analyzed. A nonlinear state point of worn surface is established by fractal dimension, average diagonal length and spectrum width. Further, a steady state sphere is obtained by the nonlinear state point and [Formula: see text]-means clustering algorithm. Results show that fractal, multifractal and recurrence parameters characterize the worn surface from different perspectives. They should be used simultaneously to comprehensively characterize the integral structures, partial structures and internal structures of worn surface. The proposed nonlinear state point shows a variation process of concentration–stabilization–separation during the wear process. The wear states can be identified effectively by the relationship between nonlinear state points and steady state sphere.

Effectiveness of Recurrence Quantification Measures in Discriminating Subjects With and Without Voice Disorders

The objective of this study was to analyze the accuracy of recurrence quantification measurements (RQMs) in discriminating between individuals with and without voice disorders. This study consisted of a total of 541 recorded voice samples from normal and dysphonic subjects. All subjects recorded a sustained vowel /Ɛ/ and underwent a laryngoscopic examination of the larynx. Twelve RQMs and three parameters related to the topology of the phonatory system were extracted from the samples, for a total of 15 measures. The classification used quadratic discriminant analysis and includes the measures of accuracy, sensitivity, and specificity. Single measurements such as Shannon's entropy, average diagonal length, and transitivity had only acceptable performance ratings (≥70%) in discriminating between individuals with and without voice disorders. The combination of the parameters average diagonal length, Shannon's entropy, trapping time, length of the longest vertical line, tau, imbedding dimension, neighborhood radius, and transitivity produced the highest accuracy in discrimination (83.27%). Therefore, the performance of RQMs related to the formation of diagonal lines in classifying individuals with and without voice disorders was acceptable at ≥70%. A combination of RQMs showed good performance in discriminating between the study groups, with higher sensitivity and specificity.

Recurrence Plots: a New Tool for Quantification of Cardiac Autonomic Nervous System Recovery after Transplant.

ObjectiveTo evaluate a possible evolutionary post-heart transplant return of autonomic function using quantitative and qualitative information from recurrence plots.MethodsUsing electrocardiography, 102 RR tachograms of 45 patients (64.4% male) who underwent heart transplantation and that were available in the database were analyzed at different follow-up periods. The RR tachograms were collected from patients in the supine position for about 20 minutes. A time series with 1000 RR intervals was analyzed, a recurrence plot was created, and the following quantitative variables were evaluated: percentage of determinism, percentage of recurrence, average diagonal length, Shannon entropy, and sample entropy, as well as the visual qualitative aspect.ResultsQuantitative and qualitative signs of heart rate variability recovery were observed after transplantation.ConclusionThere is evidence that autonomic innervation of the heart begins to happen gradually after transplantation. Quantitative and qualitative analyses of recurrence can be useful tools for monitoring cardiac transplant patients and detecting the gradual return of heart rate variability.

Recurrence evolvement of brass surface profile in lubricated wear process

This investigation exemplifies how recurrence analysis can be applied to characterize the non-linear dynamic evolution of Cu–30%Zn brass surfaces when sliding under boundary lubricated conditions against AISI 52,100 steel. Roughness profiles of the wear surface of the brass specimen were measured periodically using a specially-designed apparatus to locate the same area of the wear surface. Recurrence plots of these changing surface profiles measured are presented. Two recurrence parameters, average diagonal length (ADL) and correlation dimension (CD), are also computed. The recurrence plots depict conditions before wear testing, during steady-state wear, and after severe wear begins. These sequential plots evolve from a periodic-like pattern, to a partially homogeneous pattern, and then to a disrupted pattern. During wear, the ADL first decreases, stabilizes at a small value, and then finally increases significantly, corresponding, respectively, to a wear-in stage, a steady-wear stage, and a severe wear stage. By contrast, the CD parameter tends toward two dimensions at first, then fluctuates around a large value and then rapidly decreases toward one dimension. The computation of ADL and CD reveals changes in randomness and complexity as the wear surface of the brass specimen passes through three stages. It reveals the non-linear dynamic behavior of the brass-on-steel sliding wear process particularly, but the method may be useful for studies of other metallic wear surface as well.

Recurrence plots to characterize gas–solid fluidization regimes

Recurrence plots have been used to analyze and characterize the investigated fluidization regimes: bubbling, slugging and turbulent. Recurrence plots can be qualitatively analyzed considering the distribution of their local white areas (LWA) and local bold areas (LBA). The LWA reflect the macro-scale structure in the bed and appreciably increase for slugging regime because of the increase of the bubble phase contribution to the fluidization dynamics. On the other hand, the LBA, reflecting meso-scale and micro-scale structures, decreases. Several recurrence quantification analysis parameters (RQA) have been computed for the different regimes analyzed and the most appropriate ones have been chosen to characterize and classify the fluidization regimes. It has been found out that the determinism (DET), the average diagonal length (L), the laminarity (LAM), the trapping time (TT) and the recurrence time of type 2 (RET2) detect the evolution from bubbling to slugging regime. The evolution from bubbling to turbulent regime can be detected with all the investigated RQA parameters. A combination of two RQA parameters gives an excellent classification map which distinguishes the slugging from the bubbling regime.

Characterizing atmospheric surface layer turbulence using chaotic return map analysis

Nonlinear time series analysis methods are used to investigate the dynamics of mechanical and convective turbulences in the atmospheric surface layer flow. Using dynamical invariant analysis (e.g. correlation dimension, Lyapunov exponent and mutual information) along with recurrence quantification analysis (e.g. recurrent rate, determinism, average diagonal length of recurrence plot, etc.) of the vertical wind component data, it is confirmed that a convective turbulence is a lower order manifold in its phase space exhibiting higher degree of organization than a mechanical turbulence. Applying a quasi-one-dimensional chaotic return map technique, the topological differences between the mechanical and convective turbulences are explored. These quasi-one-dimensional return maps are produced using the local maxima of the first principal component of the reconstructed turbulence data. A comparison of the probability distribution of the local maxima of a forced Lorenz model with the turbulence data indicates the possible existence of a stable fixed point for both type of turbulences. Furthermore, dynamically the mechanical turbulence is found to resemble an unforced Lorenz model whereas the convective turbulence resembles a forced Lorenz model.

Evaluation of the Spectrin Compartment Size in Normal and Diseased Red Blood Cells by Single Particle Tracking.

In a process termed “hop diffusion”, membrane proteins diffuse randomly within a cytoskeletally-enclosed compartment over short time scales, periodically hopping from one compartment to the next. Band 3 diffuses in the erythrocyte membrane bilayer in a manner that is thought to be restricted by the size and stability of the spectrin network. Although a fraction of band 3 may exhibit reduced mobility due to its association with spectrin (mediated by proteins such as ankyrin and adducin), another subpopulation of band 3 is thought to diffuse freely within the spectrin compartments, hopping from one corral to the next by transient opening of the barrier (presumably a spectrin tetramer) separating adjacent corrals. Based on this hypothesis, measurement of the compartment size and hopping frequency of a band 3 molecule in the erythrocyte membrane can provide information on the structure and stability of the spectrin network. We have combined single particle tracking (SPT) techniques with high-speed video microscopy to determine the average compartment size and diffusion coefficient of the mobile fraction of band 3 in both normal and diseased red blood cells (RBCs). Streptavidin-linked quantum dots (525nm emission) and 40 nm fluorescent beads were attached to band 3 via a DIDS-biotin-linker, and fluorescence microscopy coupled to a high speed camera was used to determine the position of band 3 with a time resolution of 8 ms (120 fps). Labeling specificity was demonstrated by blotting with streptavidin-horseradish peroxidase, and flow cytometry studies established the binding constant of DIDS-biotin for band 3 in the intact cell of ∼1-2*10−5 M. For diffusion studies, RBCs were incubated with 10−11 M conjugate in order to attach only one or two streptavidin-quantum dots per cell. SPT data were collected on both healthy and pathologic human RBCs, including HbSS (sickle cells), HbSC (sickle cell hemoglobin C), HbSBo (sickle cell zero-beta-thalasamia), HbSB+ (sickle cell beta-plus-thalasamia), HS (hereditary spherocytosis), and HPP (hereditary pyropoikilocytosis). Movement within the observed compartments was found to be random, with an average diagonal length for the mobile fraction in healthy cells of ∼100nm and a diffusion coefficient of ∼1–2*10−10cm2/s. HbSS cells, however, displayed a comparatively smaller compartment size (∼60–80nm) with a lower diffusion coefficient (0.1−1*10−10cm2/s). In contrast, HPP cells exhibited an average compartment size of ∼133nm with a diffusion coefficient of 6*10−10cm2/s. SPT data further suggest the presence of multiple populations of band 3, exhibiting both free diffusion and restricted mobilities with different characteristics. Details of band 3 diffusion in all of the aforementioned diseased and normal blood cells will be provided, and a model accounting for the multiple populations of band 3 will be presented.