8,889 research outputs found
Experimental Determination of Mechanical Quality Factor of Lead Zirconate Titanate (PZT-5A4E) by Equivalent Circuit Method under various Thermal and Resistance Conditions
No full textRayleigh number dependence of the Archimedes number dependent large-scale flow structure formation in mixed convection
No full textWe report on experimental investigations of large-scale flow structure formation in mixed convection. We characterize the flow field by measuring the velocity fields within a rectangular model room using 2D2C PIV. The control parameters are the Reynolds number Re, the Rayleigh number Ra and the Prandtl number Pr. All parameters are linked through the Archimedes number Ar. In 6.4x10-2 ≤ Ar ≤ 1.39x101, 4.2x103 ≤ Re ≤ 6.35x104 and Ra = 3.1x107, Ra = 1.8x108 and Pr = 0.713 we found flow 3 different flow structures. While keeping Ra and Pr constant and varying Ar through Re variations, we found an Ar dependence of the largescale flow structure formation within 6.4x10-2 ≤ Ar ≤ 1.39x101. Furthermore, we found a Ra dependence of the structure formation, which shifts the transition points between the structures to higher Archimedes numbers and reduces the mean velocities within the investigated domain
Influence of compression pressure from the hand access device on hand microcirculation during hand-assisted laparoscopic surgery
No full textHand access devices in hand-assisted laparoscopic surgery depend on compression pressure to prevent air leakage. Surgeons frequently experience hand ache during surgery. This study aimed to test whether the pressure with such a device affects the microvascular function of the hand.Eight healthy volunteers participated in this experimental study. The hand access device, applied to the forearm, was inflated to 0, 8, 12, and 16 mmHg in a random order, and the microvascular activity of the skin of the hand dorsum was quantified using laser Doppler and iontophoresis of increasing doses of acetylcholine (endothelial-dependent vasodilator) and sodium nitroprusside (endothelial-independent vasodilator). The end point was skin erythrocyte flux ratio as a measure of microvascular skin activity.No significant differences in microvascular responses to iontophoresis of acetylcholine and sodium nitroprusside were found at the four doses used when the hand access device was inflated at different pressures. The peak values for the hand allocated to acetylcholine were 3.48 +/- A 1.33, 3.42 +/- A 2.33, 3.38 +/- A 2.55, and 2.84 +/- A 3.10 arbitrary units, and the peak values for the hand allocated to sodium nitroprusside were 2.79 +/- A 1.60, 2.00 +/- A 1.60, 2.30 +/- A 1.50, and 2.40 +/- A 1.62 arbitrary units at cuff pressures of 0, 8, 12, and 16 mmHg, respectively.The pressure in the hand access device up to 16 mmHg does not affect the hand cutaneous microcirculation.</p
Reynolds numbers near the ultimate state of turbulent Rayleigh-Bénard convection
No full textWe report on measurements of the mean-flow Reynolds number ReU and the rms fluctuation Reynolds number ReV in turbulent Rayleigh-Bénard convection as a function of the Rayleigh number Ra for 4 x 1011 < Ra < 2 1014 and Pr ' 0:8. Both can be described by the same power law with an effective exponent = 0:44, in agreement with predictions for ReU but in disagreement with predictions for ReV
Timing Advance Estimation and Beamforming of Random Access Response in Crowded TDD Massive MIMO Systems
No full textTiming advance (TA) estimation at the base station (BS) and reliable decoding of random access response (RAR) at the users are important steps in the initial random access (RA) procedure. However, due to limited availability of physical resources dedicated for RA, successful completion of RA requests would become difficult in high user density scenarios, due to contention among users requesting RA. In this paper, we propose to use the large antenna array at the massive multiple input multiple output BS to jointly group RA requests from different users using the same RA preamble. We then beamform the common RAR of each detected user group onto the same frequency resource, in such a way that most users in the group can reliably decode the RAR. The proposed RAR beamforming therefore automatically resolves the problem of collision between multiple RA requests on the same preamble, which reduces the RA latency significantly as compared to LTE. Analysis and simulations also reveal that for a fixed desired signal-to-interference-and-noise ratio of the received RAR, both the required per-user preamble transmission power and the total RAR beamforming power can be decreased roughly by 1.5 dB with every doubling in the number of BS antennas.1
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Association of EBV with RA immunosuppressive type of treatment, family history and type of RA (SPRA and SNRA).
No full textAssociation of EBV with RA immunosuppressive type of treatment, family history and type of RA (SPRA and SNRA).</p
Investigation of electrical properties for cantilever-based piezoelectric energy harvester
No full textIn the present era, the renewable sources of energy, e.g., piezoelectric materials are in great demand. They play a vital role in the field of micro-electromechanical systems, e.g., sensors and actuators. The cantilever-based piezoelectric energy harvesters are very popular because of their high performance and utilization. In this research-work, an energy harvester model based on a cantilever beam with bimorph PZT-5A, having a substrate layer of structural steel, was presented. The proposed energy scavenging system, designed in COMSOL Multiphysics, was applied to analyze the electrical output as a function of excitation frequencies, load resistances and accelerations. Analytical modeling was employed to measure the output voltage and power under pre-defined conditions of acceleration and load resistance. Experimentation was also performed to determine the relationship between independent and output parameters. Energy harvester is capable of producing the maximum power of 1.16 mW at a resonant frequency of 71 Hz under 1g acceleration, having load resistance of 12 k Omega. It was observed that acceleration and output power are directly proportional to each other. Moreover, the investigation conveys that the experimental results are in good agreement with the numerical results. The maximum error obtained between the experimental and numerical investigation was found to equal 4.3%
Anti-erosive potential of commercial bioactive glasses on dental hard tissues / Erum Saleem Khan
No full textAims and Objectives: This study aimed to investigate the potential of two commercial
bioactive glasses NUPRO® Sensodyne® Prophylaxis Paste and Sylc® Prophy Powder
(Novamin®) in the secondary prevention of dental erosion.
Methodology: This in-vitro study utilized 30 enamel and 30 dentine specimens that
were prepared from human premolars and molars. The specimens were flattened and
polished and randomly divided into six groups having ten specimens in each group, of
which equal proportions of enamel and dentine specimens were further assigned to three
groups: Control, Nupro, and Sylc. All specimens were subjected to 10 minutes of
demineralisation in 0.3% citric acid at a pH of 3.2 ± 0.1. Baseline surface
microhardness (SMH) and surface roughness (Ra) measurements were made using a
Knoop indenter (HMV-2 Shimadzu Corporation, Japan) and the Infinite FocusG4
microscope (IFM, Alicona Imaging, Grambach/Graz, Austria). SMH was measured for
only enamel specimens. Nupro and Sylc were applied on the enamel and dentine.
Specimens were stored in remineralisation solution at 37°C and SMH measurements
were made for enamel specimens and Ra was measured for all enamel and dentine
specimens again 24 hours later. The specimens in all 6 groups were subjected to daily
cycles of acid challenge for 10 minutes and stored in remineralisation solution at 37°C
for six days. SMH (enamel) and Ra (enamel and dentine) measurements were made
every day before acid challenge. Additional 24 specimens were prepared for SEM
analysis at Baseline, Intervention and Day 6 of demineralisation. To determine the
elemental gain or loss analysis was done by Energy dispersive x-ray spectroscopy
(EDX) on specimens of Intervention and Day 6. The difference in SMH and Ra at the
ii
various time points from Baseline SMH & Ra, was the outcome measure used. The
data were analysed using SPSS version 22
Results:
All three groups of enamel showed a general trend of decrease in SMH over time. A
significant difference in SMH was observed in all three groups. Furthermore, there
were significant differences in SMH between the test groups and the controls (P <
0.05). However, significant differences in SMH were found only between Baseline
and Intervention. No significant differences were observed between the other
measurement time points and Baseline. In the Sylc group, significant differences in
SMH were observed between Baseline and Intervention and up to Day 3
demineralisation. Regarding Ra, there was a significant difference in Ra over time. A
significant difference in Ra existed between the test groups and the Control group as
well as between Nupro and Sylc (P < 0.05). All six groups showed a net increase in Ra
over the study period but with varying amounts and patterns. SEM-EDX showed
remineralisation tendency of both Sylc® Prophy Powder and NUPRO® prophylaxis
paste.
Conclusion: Sylc® Prophy Powder and NUPRO® prophylaxis paste were able to
reduce the rate of dental erosion. Sylc® Prophy Powder showed better reduction than
Nupro
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