Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
A simulator for analyzing the interaction between the oil sand terrain and a pipe wagon articulating (PWA) system has been\r\ndeveloped in this paper. An elastic-plastic oil sand model was built based on the finite element analysis (FEA) method and von\r\nMises yield criterion using the Algor mechanical event simulation (MES) software. The three-dimensional (3D) distribution of\r\nthe stress, strain, nodal displacement, and deformed shape of the oil sands was animated at an environmental temperature of\r\n25?C. The 3D behavior of the oil sand terrain was investigated with different loading conditions. The effect of the load and contact\r\narea on the stress and nodal displacement was analyzed, respectively. The results indicate that both the max stress and max nodal\r\ndisplacement increase with the load varying from 0 to 3.6 E + 7 N and decrease with the contact area varying from 2 to 10m2. The\r\nmethod presented in this paper forms the basis for evaluating the bearing capacity of oil sand ground....
Vibration signals measured from a gearbox are complex multicomponent signals, generated by tooth meshing, gear shaft rotation,\r\ngearbox resonance vibration signatures, and a substantial amount of noise. This paper presents a novel scheme for extracting\r\ngearbox fault features using adaptive filtering techniques for enhancing condition features, meshing frequency sidebands. A\r\nmodified least mean square (LMS) algorithm is examined and validated using only one accelerometer, instead of using two\r\naccelerometers in traditional arrangement, as the main signal and a desired signal is artificially generated from the measured\r\nshaft speed and gear meshing frequencies. The proposed scheme is applied to a signal simulated from gearbox frequencies with\r\na numerous values of step size. Findings confirm that 10-5 step size invariably produces more accurate results and there has\r\nbeen a substantial improvement in signal clarity (better signal-to-noise ratio), which makes meshing frequency sidebands more\r\ndiscernible. The developed scheme is validated via a number of experiments carried out using two-stage helical gearbox for a\r\nhealthy pair of gears and a pair suffering from a tooth breakage with severity fault 1 (25% tooth removal) and fault 2 (50% tooth\r\nremoval) under loads (0%, and 80% of the total load). The experimental results show remarkable improvements and enhance gear\r\ncondition features. This paper illustrates that the new approach offers a more effective way to detect early faults....
A method for improving the contrast-to-noise ratio (CNR) while maintaining the -6 dB axial resolution of ultrasonic Bmode\r\nimages is proposed. The technique proposed is known as eREC-FC, which enhances a recently developed REC-FC\r\ntechnique. REC-FC is a combination of the coded excitation technique known as resolution enhancement compression (REC)\r\nand the speckle-reduction technique frequency compounding (FC). In REC-FC, image CNR is improved but at the expense of a\r\nreduction in axial resolution. However, by compounding various REC-FC images made from various subband widths, the tradeoff\r\nbetween axial resolution and CNR enhancement can be extended. Further improvements in CNR can be obtained by applying\r\npostprocessing despeckling filters to the eREC-FC B-mode images. The despeckling filters evaluated were the following: median,\r\nLee, homogeneous mask area, geometric, and speckle-reducing anisotropic diffusion (SRAD). Simulations and experimental\r\nmeasurements were conducted with a single-element transducer (f /2.66) having a center frequency of 2.25MHz and a -3 dB\r\nbandwidth of 50%. In simulations and experiments, the eREC-FC technique resulted in the same axial resolution that would be\r\ntypically observed with conventional excitation with a pulse. Moreover, increases in CNR of 348% were obtained in experiments\r\nwhen comparing eREC-FC with a Lee filter to conventional pulsing methods....
Palatal clicks are most interesting for human echolocation.Moreover, these sounds are suitable for other acoustic applications due\r\nto their regular mathematical properties and reproducibility. Simple and nondestructive techniques, bioinspired by synthetized\r\npulses whose form reproduces the best features of palatal clicks, can be developed. The use of synthetic palatal pulses also allows\r\ndetailed studies of the real possibilities of acoustic human echolocation without the problems associated with subjective individual\r\ndifferences. These techniques are being applied to the study of wood. As an example, a comparison of the performance of both\r\nnatural and synthetic human echolocation to identify three different species of wood is presented. The results show that human\r\necholocation has a vast potential....
Acoustic source mapping techniques using acoustic sensor arrays and delay-and-sum beamforming techniques suffer from bad\r\nspatial resolution at low-aperture-based Helmholtz numbers. This is especially a problem for three-dimensional map grids, when\r\nthe sensor array is not arranged around the region spanned by the grid but on only one side of it. Then, the spatial resolution\r\nof the result map in the direction pointing away from the array is much worse than in the other lateral directions. Consequently,\r\ndeconvolution techniques need to be applied. Some of the most efficient deconvolution techniques rely on the properties of the\r\nspatial beamformer filters used. As these properties are governed by the steering vectors, four different steering vector formulations\r\nfrom the literature are examined, and their theoretical background is discussed. It is found that none of the formulations provide\r\nboth the correct location and source strength. As a practical example the CLEAN-SC deconvolution methodology is applied to\r\nsimulated data for a three-source scenario. It is shown that the different steering vector formulations are not equally well suited for\r\nthree-dimensional application. The two preferred formulations enable the correct estimation of the source location at the cost of\r\na negligible error in the estimated source strength....
Loading....