1,725,201 research outputs found
The Influence Of Equal Channel Angular Pressing Angles On The Microstructure And Properties Of Al-Si-Mg Alloy [TA483. J91 2006 f rb].
Full text linkPenyelidikan ini bertujuan untuk meningkatkan sifat-sifat fizikal dan mekanikal aloi Al-Si-Mg melalui penghalusan struktur ira yang dihasilkan oleh kecacatan plastik lampau.
The aim of this research is to improve the physical and mechanical properties of Al-Si-Mg alloy by grain structure refinement produced by severe plastic deformation through equal channel angular pressing (ECAP)
Simultaneous improvements of the strength and ductility of fine-grained AA6063 alloy with increasing number of ECAP passes
No full textIn this research, grain refinement through severe plastic deformation (SPD) in combination with a thermal treatment to create a fine initial grain structure with a high degree of supersaturation was taken as a viable approach to achieving simultaneous increases in the hardness, strength and ductility of the aluminum alloy AA6063 during further SPD. A recrystallized structure with grain sizes around 20 µm was obtained after two passes of equal channel angular pressing (ECAP), followed by a thermal treatment at 500 °C for 10 s and water quenching. The alloy with the supersaturated α-Al matrix was subjected to further ECAP processing up to six passes to create a cellular structure on a nano scale. Hardness and tensile tests revealed the changes of hardness, strength and ductility along with increasing number of ECAP passes. It was found that after two ECAP passes, the ductility of the alloy decreased from the value after the prior two-pass ECAP and thermal treatment. However, by further ECAP processing up to six passes, the ductility increased along with the increases in hardness and strength. The remarkable improvement in ductility was attributed to a nanosized cellular structure with a large area of high-angle grain boundaries developed from the fine initial grain structure formed during the two-pass ECAP and thermal treatment applied earlier.Accepted Author ManuscriptBiomaterials & Tissue Biomechanic
Site of cochlear stimulation and its effect on electrically evoked compound action potentials using the MED-EL standard electrode array
Full text linkBackground: The standard electrode array for the MED-EL MAESTRO cochlear implant system is 31 mm in length which allows an insertion angle of approximately 720°. When fully inserted, this long electrode array is capable of stimulating the most apical region of the cochlea. No investigation has explored Electrically Evoked Compound Action Potential (ECAP) recordings in this region with a large number of subjects using a commercially available cochlear implant system. The aim of this study is to determine if certain properties of ECAP recordings vary, depending on the stimulation site in the cochlea. Methods: Recordings of auditory nerve responses were conducted in 67 subjects to demonstrate the feasibility of ECAP recordings using the Auditory Nerve Response Telemetry (ART™) feature of the MED-EL MAESTRO system software. These recordings were then analyzed based on the site of cochlear stimulation defined as basal, middle and apical to determine if the amplitude, threshold and slope of the amplitude growth function and the refractory time differs depending on the region of stimulation. Results: Findings show significant differences in the ECAP recordings depending on the stimulation site. Comparing the apical with the basal region, on average higher amplitudes, lower thresholds and steeper slopes of the amplitude growth function have been observed. The refractory time shows an overall dependence on cochlear region; however post-hoc tests showed no significant effect between individual regions. Conclusions :Obtaining ECAP recordings is also possible in the most apical region of the cochlea. However, differences can be observed depending on the region of the cochlea stimulated. Specifically, significant higher ECAP amplitude, lower thresholds and steeper amplitude growth function slopes have been observed in the apical region. These differences could be explained by the location of the stimulating electrode with respect to the neural tissue in the cochlea, a higher density, or an increased neural survival rate of neural tissue in the apex. Trial registration: The Clinical Investigation has the Competent Authority registration number DE/CA126/AP4/3332/18/05
ECAP������ ��������� ������������ ��������� ������ ������������
No full textDynamic deformation behavior of ultra-fine-grained pure coppers fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four copper specimens using a torsional Kolsky bar, and then the test data were analyzed by their microstructures and tensile properties. The 1-pass ECAP`ed specimen consisted of fine dislocation cell structures elongated along the ECAP direction, which were changed to very fine, equiaxed subgrains of 300~400 nm in size as the pass number increased. The dynamic torsional test results indicated that maximum shear stress increased with increasing ECAP pass number. Adiabatic shear bands were not found at the gage center of the dynamically deformed torsional specimen of the 1- or 4-pass ECAP`ed specimen, while some weak bands were observed in the 8-pass ECAP`ed specimen. These findings suggested that the grain refinement according to the ECAP was very effective in strengthening of pure coppers, and that ECAP`ed coppers could be used without serious reduction in fracture resistance under dynamic torsional loading as adiabatic shear bands were hardly formed
Automatic detection of eCAP thresholds: Precision and accuracy of different methods
No full textWhen a person suffers from severe to profound hearing loss, a cochlear implant (CI) can aid in restoring auditory perception and speech comprehension. To obtain good speech comprehension, fitting of a CI to the user’s specific characteristics is crucial. Fitting can be a time-consuming process which requires the cooperation of a CI user and is dependent on the used methods (e.g., T-level measurements). Besides transmitting electrical stimuli, a CI can also record the response of the auditory nerve fibres to a stimulus. This response is called the electrically evoked compound action potential (eCAP). eCAP responses can be measured objectively without a user’s active cooperation and could potentially aid in the fitting of a CI. For this purpose, the eCAP thresholds are of main interest. eCAP thresholds can be determined manually by a clinical specialist, or automatically by an automatic threshold detection method. Automatic eCAP threshold detection can therefore be of aid in a completely objective and uniform CI fitting method. The goal of this study was to compare different automatic eCAP threshold detection methods (in combination with different averaging methods and different artefact reduction methods) based on the precision and accuracy of these methods.Five different automatic eCAP threshold detection methods have been examined in this study: sigmoid amplitude growth function (AGF), linear AGF, signal-to-noise ratio (SNR), cross-covariance between adjacent levels and cross-covariance with maximum level. The two different averaging methods that have been examined are standard averaging (SA) and FineGrain averaging (FG), the two different artefact reduction methods are alternating polarity (AP) and forward masking (FM). In total, 20 different combinations have been examined. The success rates of these 20 combinations have been determined, threshold confidence intervals (TCIs) were calculated as a measure of precision and the correlations between eCAP thresholds and T-levels were determined as a measure of accuracy of the different (combinations of) methods.The combination of FG FM resulted in the highest success rates for different threshold detection methods, and the threshold detection method SNR had the overall highest success rates. A two-way ANOVA revealed that both artefact reduction/averaging method and threshold detection method have a significant effect on the TCIs. The combination of FG FM had the best resultsregarding the TCIs, and the sigmoid AGF threshold detection method was the threshold detection method with the lowest mean TCI. A similar two-way ANOVA was performed for the correlation between eCAP thresholds and T-levels, revealing the same results as for the TCIs that both artefact reduction/averaging method and threshold detection method have a significant effect on the correlation coefficients. FG FM was again the best performing combination, and the sigmoid AGF threshold detection method resulted in the highest correlation coefficients.Based on these results, it can be stated that the FG FM combination for averaging and artefact reduction was the overall best combination. When comparing the different automatic threshold detection methods, the sigmoid AGF method resulted in eCAP thresholds with the highest precision and accuracy. Future research should focus on obtaining more data, further refinements of the different automatic eCAP threshold detection methods and the use of the determined eCAP thresholds in the clinical fitting of a CI.Technical Medicin
ECAP Supplementary Materials
No full textThis folder contains supplementary materials supporting the ECAP white paper, including conceptual diagrams, figure references, and an abbreviated summary of the Endocannabinoid-Associated Pathways (ECAP) model
Structural analysis of ECAP materials
No full textCílem této práce je seznámit čitatele s významnou a v posledních desetiletích pozoruhodně slibnou oblastí vývoje ušlechtilých kovových materiálů. Teoretická část je zaměřena na ultrajemnozrnné kovy a kovové slitiny zpracované za pomoci extrémní plastické deformace, konkrétně metodou ECAP. V praktická části je provedena analýza a srovnání rovinných řezů ECAP materiálů po zatížení. Hlavním účelem práce je ukázat jednu z možností porovnávání vzorků ECAP materiálů.Purpose of this work is to introduce readers into interesting and in a few last decades remarkable promising area of development fine metal materials. Theoretical part is aimed on ultrafine-grained metals and metal alloys processed by Severe Plastic Deformation, concretely by ECAP method. In the practical part of the work was made analyse a comparison of ECAP material plain cuts after stress. The main purpose of the work is to present one possibility how to compare samples of ECAP materials.Ústav fyziky a mater. inženýrstvíobhájen
Texture evolution of an Al-8Zn alloy during ECAP and post-ECAP isothermal annealing
No full textIn this work, the texture evolution of an Al-8 wt% Zn alloy during equal channel angular pressing (ECAP) and post-ECAP isothermal annealing was systematically investigated by electron backscatter diffraction (EBSD). Special attention is paid to the influence of static recovery and recrystallization on ECAP texture. After 1 pass of ECAP, the sample shows a texture similar to the ideal shear texture. During further deformation, the less deformed coarse grains rotate towards ideal ECAP texture orientations. After 5 passes of ECAP, the main texture component can still be depicted by fibers f1-f3. However, the f1, f2 and f3 fibers become less completed, indicating the fading of f1-f3 fibers. The weakening of ECAP texture with increasing deformation strains is attributed to continuous dynamic recrystallization (CDRX). Isothermal annealing treatments of the as-ECAPed 5P samples at 200 °C and 350 °C show that the static recovery and recrystallization do not change orientations of the major ECAP texture components. Instead, a full recrystallization and subsequent grain growth lead to a slight increase in the maximum intensity of ECAP texture
Texture evolution of an Al-8Zn alloy during ECAP and post-ECAP isothermal annealing
Full text linkIn this work, the texture evolution of an Al-8 wt% Zn alloy during equal channel angular pressing (ECAP) and post-ECAP isothermal annealing was systematically investigated by electron backscatter diffraction (EBSD). Special attention is paid to the influence of static recovery and recrystallization on ECAP texture. After 1 pass of ECAP, the sample shows a texture similar to the ideal shear texture. During further deformation, the less deformed coarse grains rotate towards ideal ECAP texture orientations. After 5 passes of ECAP, the main texture component can still be depicted by fibers f1-f3. However, the f1, f2 and f3 fibers become less completed, indicating the fading of f1-f3 fibers. The weakening of ECAP texture with increasing deformation strains is attributed to continuous dynamic recrystallization (CDRX). Isothermal annealing treatments of the as-ECAPed 5P samples at 200 °C and 350 °C show that the static recovery and recrystallization do not change orientations of the major ECAP texture components. Instead, a full recrystallization and subsequent grain growth lead to a slight increase in the maximum intensity of ECAP texture.acceptedVersion© 2019. This is the authors’ accepted and refereed manuscript to the article. Locked until 20.6.2021 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0
New process configurations for ECAP
No full textECAP is a very mature SPD process, which seems not to leave many options for further development. However, there are still unexplored ECAP configurations, two of which will be presented here
- …
